WO2002006159A1 - Titanium-containing materials - Google Patents

Titanium-containing materials Download PDF

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WO2002006159A1
WO2002006159A1 PCT/NZ2001/000144 NZ0100144W WO0206159A1 WO 2002006159 A1 WO2002006159 A1 WO 2002006159A1 NZ 0100144 W NZ0100144 W NZ 0100144W WO 0206159 A1 WO0206159 A1 WO 0206159A1
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method
preparing
ti0
solution
metal
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PCT/NZ2001/000144
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French (fr)
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Najeh Ibrahim Al-Salim
Timothy Kemmitt
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Industrial Research Limited
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B82NANOTECHNOLOGY
    • B82YSPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00Nanotechnology for materials or surface science, e.g. nanocomposites
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/42Platinum
    • BPERFORMING OPERATIONS; TRANSPORTING
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    • B01J23/48Silver or gold
    • B01J23/50Silver
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Abstract

The invention relates to a method of preparing a solution containing particles which contain titanium ions wherein one or more hydrolysable titanium-containing compound(s) is stabilised by oxalic acid in a reaction medium. The reaction further relates to the preparation of titania materials (including particulate materials, coating solutions and films) which comprise or include anatase phase titania, and so are suitable in photocatalytic applications. The invention also deals with a method of preparing B-phase titania.

Description

TITANIUM-CONTAINING MATERIALS

FIELD OF THE INVENTION

This invention relates to processes for preparing titanium-containing materials. More particularly, it relates to processes of preparing solutions containing colloidal particles containing titanium ions, and to processes for preparing titanium dioxide containing materials from such solutions. This invention also relates to application of these titanium-containing materials.

BACKGROUND OF THE INVENTION

Titanium-containing composite materials have a range of applications. These include applications that depend on the ability of these materials to function as photocatalysts, constituents of film electrodes, hydrophilic surfaces, and to prevent the growth of micro-organisms.

Photocatalvsts

Photocatalysis using titania and titania-based materials have been widely described in recent years for water treatment and air purification (Hoffmann, Martin, Choi and Bahnemann, Chem. Rev. 1995, 95, 69). Anatase was reported to be the most active phase of Ti02 with a band gap of 3.2 eV (387 nm). Trace organic contaminants can be photodegraded on the surface of anatase particles under UV light to carbon dioxide, water, and possibly mineral ions.

Different factors have been reported to affect the photoactivity of anatase. High surface area and large pore diameter are extremely important to enhance the adsorption of contaminants and increase the light interaction with the material.

The crystallite size can also determine the extent of photoactivity of Ti02. Smaller crystallite size is considered essential to repress charge recombination of the photogenerated electrons and holes and render them more available for redox reactions at the surface of the photocatalyst particles.

Another way of increasing the photoactivity of anatase is by doping with metals or metal oxides. Of the metals, platinum doping has been found to be very effective in improving the photocatalytic process. The extent of doping and the dopant particle size are important factors. Doping a photocatalyst with more than 5% by weight platinum should be avoided as this could produce large platinum particle size and prevent the light from reaching the photocatalyst surface. Deposition of platinum metal on titania has been reported using a number of different methods. One of the methods is by photodeposition of platinum by irradiating hexachloroplatinic acid that is adsorbed on anatase powder under nitrogen first described by Kraeutler and Bard (J. Am. Chem. Soc. 1978, 100, 4317). Photodeposition of platinum was also achieved by illuminating a deaerated suspension of hexachloroplatinic acid and Ti02 using ethanol as a sacrificial electron donor (Yamaguchi and Sato, J. Chem. Soc. Faraday Trans. 1, 1985, 81, 1237). High temperature reduction (480°C) of hexachloroplatinic acid adsorbed on Ti02 in hydrogen gas was also reported (Pichat et al Nouv. J. Chim 1981, 5, 627636). Anderson and Xianzhi (Patent number WO9640430, 1996) described a method of reducing hexachloroplatinic acid adsorbed on Ti02 pellets using NaBHL} in dilute NaOH.

Doping of Ti02 with silver by photodeposition is known (Schwarz et al, Chem. Rev. 1995, 95, 477) where Ti02 was dispersed in a dilute solution of silver nitrate and a sacrificial agent. The suspension was then irradiated with a mercury lamp. However copper 2+ was reported to be reduced to Cu20 under irradiation of Ti02 (Sakata et al, Chem. Letters, 1998, 1253).

The formation of photocatalyst thin films has been reported to be useful in maintaining clean surfaces. Building surfaces like windows and tiles, automobile screens and mirrors, etc. may attract all sorts of contaminants such as oil deposits, smoke and dust. When a surface is coated with a photocatalyst film, this coating can degrade the deposited contaminants by the aid of natural or artificial UV light. This process of phenomenon is usually referred to as a "self-cleaning surface".

Hydrophilic Surfaces Windows, mirrors and'other surfaces are fogged when cold due to the condensation of moisture droplets. One of the ways to avoid this phenomenon is to make the surface hydrophilic by applying a transparent hydrophilic coating, such as Ti02. Hydrophilicity can be expressed by measuring the contact angle of a water drop on the surface. In order to maintain the hydrophilicity of such a surface, it needs to be periodically exposed to a UV light. Exposure to even a low intensity of UV radiation from sunlight or fluorescent light can maintain the hydrophilicity. In this way the contact angle can be reduced to 2-5°, which is enough to prevent fogging of the surface. A recent Patent by TOTO Ltd (EP 0816466 Al, 1998) described a method of applying TiOi-containing thin film that is capable of maintaining a contact angle of 3° when subjected to irradiation using a white fluorescent lamp having a UV intensity of 0.004 mW/cm2.

Scrubbing Technology

One of the desired applications of photocatalysts is their use to degrade volatile organic compounds (VOCs) under UV irradiation. Many VOCs such as formaldehyde, toluene trichloroethylene (TCE), ethylene, etc. are considered toxic, carcinogenic, irritant or harmful to a different extent. Some of these are considered easy to photodegrade such as formaldehyde, while others, such as toluene and ethylene, are considered difficult to decompose. Photocatalysts can also be used in purification of water to degrade any traces of pollutants such as organic compounds, dyes, etc., and even microorganisms by allowing water to be in contact with the UV irradiated photocatalyst. Of particular interest is the effect of ethylene gas on stored fruit, vegetables and cut flowers. These produce need to be consumed, exported or delivered to supermarkets and food stores while still being fresh. Ageing of produce can be caused by exposure to ethylene gas. This is known to be released by produce, such as apples and bananas and will affect other things that are stored in the same place. Ethylene is a plant hormone that causes ripening and ageing of fruit, vegetable and flowers even in low concentrations. The ripening speed may vary from one type of produce to another depending on the concentration of ethylene. For example, tomatoes ripen within hours if exposed to ethylene in a concentration of more than 100 ppm. Kiwi fruit may ripen even at lower concentration of few parts per million of ethylene. This can create problems in storing or transporting different produce in the same cold store or container.

Nelson et al (US Patent 6240767, 2001) have described a system for accurately monitoring part per million level of ethylene gas in atmosphere and fruit containers. Having an efficient way to control and degrade high level of ethylene is as important as monitoring the ethylene concentration during storage or transport.

Patterned Films

The development of new methods for depositing patterned ceramic films onto surfaces is especially important in microcircuit fabrication such as field-effect transistors that need to be down-sized to a submicrometer thickness. Titanium dioxide has a favourable dielectric and refractory properties to be utilised as part of a micropatterned film. Koumoto, Sugiyama and Seo (Chem. Mater. 1999, 11, 2305) have described a low temperature patterning process for Ti02 deposition that utilises phenyltrichlorosilane as a patterning template which was irradiated with a Hg lamp through a photomask before deposition of Ti02 from acidic (NH() TiF6 solution. These patterns exhibit significant line edge roughness of -7.3 micrometer that corresponds to 28% variation according to the authors, which exceeds the usual 5% variation allowed by current electronics design rules. Kikuta, Tkagi and Hirano (J. Am. Ceram. Soc. 1999, 82, 1569) have shown that finer patterns of Ti02 can be produced from solutions of titanium alkoxide modified with alkanolamines by photolithography. The precursors were coated on a substrate and decomposed by ultra-high-pressure mercury lamp. The films were then heat-treated to convert it to anatase phase.

It is an object of the present invention to provide an alternative process for preparing titanium-containing materials, and/or to provide an alternative means of employing titanium containing compounds, and/or to at least provide the public with a useful alternative.

STATEMENTS OF THE INVENTION

In a first aspect of the invention there is provided a method of preparing a solution containing colloidal particles which contain titanium ions comprising or including the step of : A. reacting or otherwise stabilising one or more hydrolysable titanium-containing compound(s) with oxalic acid in a reaction medium under conditions such that a colloidal solution is obtained.

Preferably A occurs under conditions such that peptization of the colloidal solution is substantially obtained and substantially maintained.

Preferably the conditions include stirring or agitation of the one or more hydrolysable titanium- containing compound(s) with oxalic acid in the reaction medium, more preferably at a temperature between ambient temperature to near the boiling point of the reaction mixture, even more preferably at a temperature between about 40°C and about 80°C. Preferably the stirring or agitation occurs over a reaction time ranging from substantially 15 minutes up to substantially 3 hours.

Preferably the reaction medium comprises water or a water/alcohol mixture and wherein the titanium- containing compound is hydrolysable in water and/or in base.

Preferably the titanium containing compound is water-hydrolysable and the titanium-containing compound is of the formula Ti(OR)4, where R is a C2-C6 linear or branched chain alkyl group; more preferably the titanium containing compound is titanium tetraisopropoxide and/or titanium tetrabutoxide. Preferably the water-hydrolysable titanium containing compound is: first combined with a solution of oxalic acid in alcohol, followed by addition of water, or added directly to water, or to a mixture of water and an alcohol, to form a slurry, followed by addition of oxalic acid, or - added to a solution of oxalic acid in water or in a mixture of water and alcohol.

Preferably the water-hydrolysable titanium-containing compound is hydrolysed using water prior to reaction with or stabilisation by oxalic acid, to give a hydrolysis product.

Alternatively or additionally the titanium-containing compound is base-hydrolysable and the titanium- containing compound is selected from, but not restricted to, TiCl4 and/or TiOS04.

Preferably the base-hydrolysable titanium-containing compound is hydrolysed to a hydrolysis product, using a base prior to reaction with or stabilisation by oxalic acid, the hydrolysis product being filtered and/or washed, to form a slurry before reaction with or stabilisation by, the oxalic acid.

Preferably the oxalic acid is either anhydrous oxalic acid, or hydrated oxalic acid, and preferably the amount of oxalic acid is such as to provide a mole ratio of oxalic acid: titanium in the range of about 0.2: 1 to about 1: 1.

Preferably the water content of the reaction medium is such as to provide a mole ratio of water: titanium in the range of from about 200: 1 to about 800: 1; more preferably in the range of from about 400: 1 to about 600: 1. Preferably, when alcohol is present in the reaction medium, the alcohol is a mono hydroxyl aliphatic alcohol having the formula ROH, where R is a to C linear or branched alkyl group, such as ethanol or t-butanol, and the preferred amount of alcohol present is such as to provide a mole ratio of alcohol: titanium of from zero to 100:1, more preferably 10: 1 to 50: 1. Preferably the solution may be stored at any concentration level prior to further use, preferably at up to about 32% by weight Ti02, between 0°C and 20°C.

Preferably the oxalate concentration of the solution is at any stage reduced by irradiating the solution with UV light.

According to a second aspect of the invention there is provided a solution containing colloidal particles which contain titanium ions prepared substantially according to the preceding method.

According to a third aspect of the invention there is provided a solution containing colloidal particles which contain titanium ions wherein the particles are stablised by oxalic acid, or stabilised by reaction with oxalic acid.

According to a fourth aspect of the invention there is provided a solution containing colloidal particles which contain titanium ions prepared substantially as herein described with reference to any one of more of the accompanying examples.

According to a fifth aspect of the invention there is provided a method of preparing a TiO2- Containing Product comprising or including the steps of:

I. preparation of a solution containing colloidal particles which contain titanium ions wherein the particles are Stabilised by oxalic acid, or stabilised by reaction with oxalic acid, and

II. further processing of the solution to obtain the product.

Preferably I occurs under conditions such that peptization of the colloidal solution is substantially obtained and substantially maintained. Preferably the conditions include stirring or agitation of one or more hydrolysable titanium-containing compound(s) with oxalic acid in a water or water/alcohol reaction medium, more preferably at a temperature between ambient temperature to near the boiling point of the reaction mixture, even more preferably at a temperature between about 40°C and about 80°C. Preferably the stirring or agitation occurs over a reaction time ranging from substantially 15 minutes up to substantially 3 hours. Preferably the Ti02 phase in the product, at least initially, includes, is predominantly or is substantially anatase.

Preferably the method comprises or includes the steps of:

1) preparation of a solution containing colloidal particles which contain titanium ions wherein the particles are stabilised by oxalic acid or stabilised by having been reacted with oxalic acid, and

2) preparation of a colloidal mixture by addition of, or mixing with, one or more additives to the solution, and

3) further processing of the solution to obtain the product. Preferably step 1) comprises or includes the method as previously described in one or more of the first- fourth aspects of the invention.

Preferably the additives of step 2) include one or more of: a) silica or a silica precursor, (preferably when added it is as colloidal silica, and preferably added in an amount to yield a ratio substantially from 1 to 99 wt % relative to titanium in the product, more preferably from 30-60 wt %, and preferably the concentration of the colloidal silica is such as to provide between about 1 and 50% by weight in the product), b) water, or alcohol, soluble ketone(s) c) organic acid(s), d) water soluble aliphatic or aromatic alcohol(s), diol(s) or polyol(s), e) elhanolamine(s), f) metal precursor(s), g) surfactant(s) (and preferably when added the surfactant(s) is or includes one or more of the Brij series, Triton series, Tergitol series, Pluronic series, potassium dodecyl sulphate, or any other surfactant that does not cause gelling), h) silane(s) (and preferably when added, it is is added neat or as solution in an aqueous or organic solvent that is miscible with water, preferably it is a hydrolysable or partially hydrolysable silane compound of a formula RSiX3> R2SiX 2 and SiX4 (where R is a simple or functionalrsed organic group and X could be a halide or an alkoxide group)).

Preferably if added, the metal precursor is a metal salt or metal complex, more preferably a soluble metal salt or complex, preferably of Pd, Pt, Ag and Cu.

When the metal is Pd or Pt preferably the precursor is (but not restricted to) one of the hexachloro- complexes of Pd or Pt, and preferably the Pd or Pt hexachloro-complex is mixed with a low carbon organic compound (such as formaldehyde, formic acid, methanol or ethanol) as a sacrificial compound, which is preferably added in excess relative to the precursor metal, more preferably at a etaksacrificial compound mole ratio of approximately.1:5.

Alternatively or additionally, the metal is Ag and the precursor is one or more of (but not restricted to) silver acetate or silver nitrate.

Alternatively or additionally the metal is Cu and the precursor is one or more of (but not restricted to) copper acetate, copper sulphate and copper nitrate.

Preferably step 3) includes removal of the solvent, more preferably by one or both of the steps of : i) causing the solution to gel (a gelling step), ii) curing of the gel (a curing step) to remove or reduce the quantity of the oxalic acid and/or any one or more additives. Preferably the gelling step is effected by one or more of: evaporating the solvent; at room temperature or above; and/or evaporating the solvent under a vacuum, with or without heating; and/or addition of a gelling agent including (but not restricted to) a dilute mineral acid solution such as of HC1, HN03 or H2S04, or an alkaline solution such as KOH, ammonia, sodium carbonate or tetraalkylammonium hydroxide.

Preferably a xerogel may be produced from the gelling step.

Preferably the curing of the gel is effected by exposure to UV radiation and/or by heat.

Preferably the wavelength of the UV radiation substantially or partially coincides with the band gap of the Ti0 in the anatase phase.

Preferably the curing time is determined by the amount of oxalic acid to be decomposed and/or the wavelength of the radiation and/or the intensity of the radiation.

Preferably there is an additional step 4), which includes one or both the steps of: i) impregnation of the titanium containing-product with a metal precursor, (an impregnation step) and/or ii) transformation to a metal or metal oxide of any metal precursor added within step 2) and/or step

4) (a transformation step).

Preferably the metal of the precursor of i) may be one or more of Pd, Pt, Cu or Ag.

Preferably when the metal precursor includes Pd or Pt the metal precursor may be mixed with a sacrificial compound of formaldehyde, formic acid, methanol or ethanol, in excess relative to the metal precursor.

Preferably the transformation step occurs by one or more of: i) heating at a suitable temperature to transform the metal precursor to the metal or metal oxide, and/or ii) exposing the metal precursor or the Ti02-Containing Product containing the metal precursor, to a dilute hydrazine hydrate solution for a sufficient time to allow the complete reduction of the metal to zero valency, and/or iii) UV irradiation to form metal particles and/or metal oxides within the titanium dioxide.

Preferably when: • the metal of the metal precursor is Ag, UV irradiation is employed and UV irradiation is stopped substantially when the colour of the TiCVproduct changes to light grey-black, and/or

• the metal of the metal precursor is Cu, UV irradiation is employed and UV irradiation is stopped substantially when the colour of the Ti02-Containing Product changes from light green to bronze, and/or • the metal of the metal precursor is Pd, UV irradiation is employed and UV irradiation is stopped substantially when the colour of the Ti02-Containing Product changes from grey to black and/or

• the metal of the metal precursor is Pt, UV irradiation is employed and UV irradiation is stopped substantially when the colour of the Ti02-Containing Product changes from grey to black. Preferably when hydrazine hydrate solution exposure is employed in the transformation step the Ti02- product is then washed with water to remove the excess hydrazine.

Preferably the final metal content in the Ti02 of the Ti02-product is less than 2% by weight, more preferably it is between 0.2 to 0.5 % by weight.

Preferably sometime prior to step 3) the oxalate concentration of the solution is reduced by irradiating the solution with UV light.

According to a sixth aspect of the invention there is provided a method of preparing a particulate material of or containing TiO2 comprising or including the steps of:

I. preparation of a solution containing colloidal particles which contain titanium ions wherein the particles are stabilised by oxalic acid, or are stabilised by reaction with oxalic acid,

II. further processing of the solution to obtain the particulate material.

Preferably I. occurs under conditions such that peptization of the colloidal solution is substantially obtained and substantially maintained.

Preferably the conditions include stirring or agitation of one or more hydrolysable titanium-containing compound(s) with oxalic acid in a water or water/alcohol reaction medium, more preferably at a temperature between ambient temperature to near the boiling point of the reaction mixture, even more preferably at a temperature between about 40°C and about 80°C. Preferably the stirring or agitation occurs over a reaction time ranging from substantially 15 minutes up to substantially 3 hours.

Preferably the particulate material is partially or substantially entirely Ti0

Preferably the Ti02 phase in the particulate material, at least initially, includes, is predominantly or is substantially anatase and/or predominantly or substantially Ti02 B phase. Preferably the method comprises or includes the steps of:

1) preparation of a solution containing colloidal particles which contain titanium ions wherein the particles are stabilised by oxalic acid or stablisied by having been reacted with oxalic acid,

2) preparation of a colloidal mixture by addition of one or more additives to the solution,

3) further processing of the colloidal mixture to obtain the particulate material. Preferably step 1) comprises or includes the method as previously described in one or more of the first to fourth aspects of the invention.

Preferably the additives of step 2) include one or more of: colloidal silica, or a silica precursor, a metal precursor. Preferably, when colloidal silica or a silica precursor is added it is in an amount to give a ratio substantially between 1 and 99 weight percent relative to titanium or more preferably a ratio from 30 to 60 wt % relative to titanium, and preferably the concentration of the colloidal silica is between about 1 and 50% by weight. Preferably when a metal precursor is added, it is a soluble metal salt or complex, preferably of one or more of Pd, Pt, Ag and Cu.

Preferably the metal of the metal precursor is one of: - Ag and the precursor is one or more of (but not restricted to) silver acetate or silver nitrate, and/or

Cu and the precursor is one or more of (but not restricted to) copper acetate, copper sulphate and copper nitrate, and/or

Pd or Pt and precursor is (but not restricted to) one the hexachloro-complexes of Pd or Pt. Preferably when the metal is Pd or Pt and the Pd or Pt hexachloro-complex is mixed with a low carbon organic compound as a sacrificial compound, of formaldehyde, formic acid, methanol or ethanol, and it is added in excess relative to the metal precursor, preferably at a mole ratio of approximately.l:5. Preferably step 3) includes: i) a gelling step, and ii) a curing step to remove or reduce the quantity of the oxalic acid and/or one or more other additives. Preferably the gelling step is effected by one or more of: evaporating the solvent; at room temperature or above; evaporating the solvent under a vacuum, with or without heating; - addition of a gelling agent including (but not restricted to) a dilute mineral acid solution such as HC1, HNO3 or H2S04, or an alkaline solution such as KOH, ammonia, sodium carbonate or tetraalkylammonium hydroxide. Preferably curing of the gel is effected by exposure to UV radiation and/or by heat, and preferably a xerogel is produced from the gelling step. Preferably the wavelength of the UV radiation substantially or partially coincides with the band gap of the Ti02 in the anatase phase, and preferably the curing time is determined by the amount of oxalic acid to be decomposed and/or the wavelength of the radiation and/or the intensity of the radiation. Preferably there is an additional step 4) which includes one or both the steps of: i) impregnation of the particulate material with a metal precursor, (an impregnation step) and, ii) transformation to a metal or metal oxide of any metal precursor added within step 2) and/or step

4) (a transformation step). Preferably the metal of the precursors of step i) is one or more of Pd, Pt, Cu or Ag. Preferably when the metal precursor is Pd or Pt the metal precursors is mixed with a sacrificial compound of formaldehyde, formic acid, methanol or ethanol, in excess relative to the metal precursor. Preferably the transformation step occurs by one of more of: i) heating at a suitable temperature to transform the metal precursor to the metal or metal oxide, and/or ii) exposing the metal precursor or the particulate material containing the metal precursor, to a dilute hydrazine hydrate solution for a sufficient time to allow the complete reduction of the metal to zero valency, and/or iii) UV irradiation to form metal particles and/or metal oxides within the titanium dioxide.

Preferably: the metal of the metal precursor is Ag, UV irradiation is employed and UV irradiation is stopped substantially when the colour of the particulate material to light grey-black, and/or the metal of the metal precursor is Cu, UV irradiation is employed and UV irradiation is stopped substantially when the colour of the particulate material changes from light green to bronze and/or the metal of the metal precursor is Pd, UV irradiation is employed and UV irradiation is stopped substantially when the colour of the particulate material changes from grey to black, and/or the metal of the metal precursor is Pt, UV irradiation is employed and UV irradiation is stopped substantially when the colour of the particulate material changes from grey to black.

Preferably when hydrazine hydrate solution exposure is employed in the transformation step the powder is then washed with water to remove the excess of hydrazine.

Preferably the final metal content in the Ti02 of the Ti02-product is less than 2% by weight and more preferably between 0.2 to 0.5 % by weight.

Preferably before step 3) the oxalate concentration of the solution is reduced by irradiating the solution with UV light.

Preferably the particulate material produced in the method is a powder; alternatively it is granular.

According to a seventh aspect of the invention there is provided a method of preparing a TiO2 coating solution comprising or including the steps of:

I. preparation of a solution containing colloidal particles which contain titanium ions wherein the particles are stabilised by oxalic acid, or are stabilised by having been reacted with oxalic acid, and π. further processing of the solution to obtain the coating solution.

Preferably I. occurs under conditions such that peptization of the colloidal solution is substantially obtained and substantially maintained.

Preferably the conditions include stirring or agitation of one or more hydrolysable titanium-containing compound(s) with oxalic acid in a water or water/alcohol reaction medium, more preferably at a temperature between ambient temperature to near the boiling point of the reaction mixture, even more preferably at a temperature between about 40°C and about 80°C. Preferably the stirring or agitation occurs over a reaction time ranging from substantially 15 minutes up to substantially 3 hours. Preferably the method comprises or includes the steps of:

1) preparation of a solution containing colloidal particles which contain titanium ions wherein the particles are stabilised by oxalic acid, or are stabilised by having been reacted with oxalic acid,

2) preparation of a colloidal mixture by addition of one or more additives to the solution. Preferably step 1) includes or comprises the method as claimed in any one of the first to fourth aspects of the invention.

Preferably step 2) includes any one or more of the following: i) Addition of or mixing with silica, or a silica precursor (preferably, when added or mixed, it is colloidal silica, and it is added in an amount to give a ratio substantially between 1 and 99 weight percent relative to titanium, more preferably from 30 to 60 wt % relative to titanium; and preferably the concentration of the colloidal silica is between about 1 and 50% by weight), ii) Addition of or mixing with any proportion of water-soluble or alcohol-soluble ketone(s)

(preferably when added or mixed, it is acetone and/or acetylacetone), iii) Addition of or mixing with any proportion of organic acid(s) (preferably when added or mixed, and it is mono-, di- or multi-functional, with or without hydroxyl groups, more preferably it/they may be one or more of acetic, lactic, tartaric, citric, maleic, malic, malonic, diglycolic, benzoic, 1,2,4,5-C6H2 (COOH)4, EDTA, and/or mixtures thereof), iv) Addition of or mixing with any proportion of water-soluble aliphatic or aromatic alcohol(s), diol(s) or polyol(s) (preferably when added it/they may be one or more of ethanol, propanol, ethylene glycol, glycerol, polyethylene glycol, polyvinylalcohol, phenol, catechol, polysaccharides), v) Addition of or mixing with any proportion of ethanolamine(s), (such as monoethanolamine, diethanolamine and triethanolamine, or a mixture thereof), vi) Addition of or mixing with any proportion of surfactant(s) (preferably when added or mixed, it/they may be selected from one or more of the Brij series, Triton series, Tergitol series, Pluronic series, potassium dodecyl sulphate, or any other surfactant that does not cause gelling, and preferably at a concentration is between 0.01 to 5% by weight relative to Ti02), vii) Addition of or mixing with one or more metal precursor(s),

Addition of or mixing with one or more silane(s) (preferably when added or mixed, and it is a hydrolysable or partially hydrolysable silane compound(s) of a formula RSiX3, R2SiX2 and SiX4 (where R is a simple or functionalised organic group and X could be a halide or an alkoxide group) and preferably added neat or as a water-miscible solution, preferably such that n the silane concentration is between 1-50%, more preferably 10-35% by total weight.). Preferably when one or more metal precursor(s) is added or mixed it is a soluble metal salt or complex of one or more of Pd, Pt, Ag and Cu. Preferably the metal is one or more of:

Ag and the precursor is one or more of (but not restricted to) silver acetate or silver nitrate, and/or

Cu and the precursor is one or more of (but not restricted to) copper acetate, copper sulphate and copper nitrate, and/or

Pd or Pt and precursor is (but not restricted to) one of the hexachloro-complexes of Pd or Pt. Preferably when the metal is Pd or Pt, the Pd or Pt hexachloro-complex is mixed with a low carbon organic compound as a sacrificial compound, of formaldehyde, formic acid, methanol or ethanol, which added in excess relative to the metal precursor.

Preferably here is the further step 3) of storing the coating solution at any concentration, preferably between 0-20°C, more preferably between 4-15°C.

According to an eighth aspect of the invention there is provided a method of preparing a TiO2-coated substrate comprising or including the steps of:

I. preparation of a coating solution substantially as previously described, and

II. further processing of the solution to obtain the coated substrate.

Preferably the Ti02 phase in the coated substrate, at least initially, includes, is predominantly or is substantially anatase.

Preferably the substrate is one or more of (but not restricted to) glass, quartz, glass fibre, woven glass fibre, ceramics, silicon wafers, metals, polymer surfaces (such as polyethylene or polyester), wood, or building materials such as mortar, brick, tiles, or concrete. Preferably step II includes i) application of the coating solution to a substrate, and ii) a gelling step, and iii) a curing step.

Preferably application of the coating solution is effected by techniques such as (but not restricted to) spin-coating, dip-coating or spraying.

Preferably prior to application of the coating solution a protective layer of amorphous silica and/or alumina (and/or precursors thereof) is applied to the substrate.

Preferably the precursor(s) for amorphous silica may be selected from (but not limited to) the series tefraalkoxysilanes, alkoxychlorosilanes and the precursors for amorphous alumina may be selected from (but not limited to) the series aluminium trialkoxides, and the precursors are prepared by hydrolysing the silica and/or the alumina precursor(s) in acid solution.

Preferably curing of the gel is effected by exposure to UV radiation and/or by heat. Preferably the wavelength of the UV radiation substantially or partially coincides with the band gap of anatase TiO2.

Preferably the curing time is determined by the amount of oxalic acid to be decomposed and/or the amount of silane (if present) and/or the amount of surfactant (if present) and/or the wavelength of the radiation and/or the intensity of the radiation.

Preferably the gelling step is effected by one or more of: evaporating the solvent; at room temperature or above; evaporating the solvent under a vacuum, with or without heating; - addition of a gelling agent including (but not restricted to) a dilute mineral acid solution such as

HC1, HN03 or H2S04, or an alkaline solution such as KOH, ammonia, sodium carbonate or tetraalkylammonium hydroxide.

Preferably there is a further step III which includes one or both the steps of: i) impregnation of the titanium containin'g-product with a metal precursor, (an impregnation step) and/or ii) transformation of any metal precursor added within step I) and/or step HI) (a transformation step).

Preferably the metal of the precursors of step i) is one or more of Pd, Pt, Cu or Ag, and preferably when the metal precursor is Pd or Pt the metal precursors is mixed with a sacrificial compound of formaldehyde, formic acid, methanol or ethanol, in excess relative to the metal precursor.

Preferably curing of the gel is effected by exposure to UV radiation and/or by heat and/or by evaporation of the solvent, and preferably a xerogel is produced either as an intermediate, or as a product. Preferably, when UV radiation is employed the wavelength of the UV radiation substantially or partially coincides with the photocatalytically active band gap of the Ti02 in the anatase phase.

Preferably the curing time is determined by the amount of oxalic acid to be decomposed and/or the wavelength of the radiation and/or the intensity of the radiation.

According to a ninth aspect of the invention there is provided a method of preparing a hardened TiO2- coated substrate comprising or including the steps of: i) preparation of a coating solution substantially as described previously and wherein at least both an acid and an alcohol are added to the solution in a certain quantity, ii) application of the coating solution to a substrate, iii) heating to around 150°C, iv) further heating to around 450°C to decompose the organic materials and/or to effect sintering of the coating. According to a tenth aspect of the invention there is provided a method of preparing a patterned TiO2- coated substrate comprising or including the steps of : i) preparation of a coated substrate substantially as described previously prior to any gelling or curing steps (if any), ii) masking one or more regions of the coating , iii) curing of the unmasked region(s) of coating by exposing the unmarked region(s) to an ultraviolet light to photocatalytically destroy the oxalic acid and other organic materials present in the titanium oxide of the unmasked region(s), iv) development of the film.

Preferably the coating solution produces a film which contains 50 to 100%) by weight titania after curing.

Preferably only one layer of coating solution is applied to obtain sharper and clearer patterns. Preferably development of the film is by one or more of: i) application of an acid solution wherein the acid solution is any dilute mineral acid such as sulphuric and/or an organic acid solution such as oxalic, lactic, citric, tartaric or sulphuric acid and/or an acidic salt solution where the salt is, ammonium sulphate or aluminium sulphate and/or; ii) application of other materials such as hydrogen peroxide and/or; iii) a radicational or mechanical method including ultrasonication, and/or iv) any other method for redissolution of the UV - unexposed gel.

Preferably the development occurs at room temperature, or under conditions of heating, and preferably is followed by a final step of sintering the coating. Preferably there may be one or more additional prior step to sintering including one or both of the steps of

- evaporating the solvent; at room temperature or above and/or

- evaporating the solvent under a vacuum, with or without heating.

Preferably curing of the gel is effected by exposure to UV radiation and/or by heat, and preferably a xerogel may be produced as an intermediate.

Preferably when UV radiation is employed the wavelength of the UV radiation substantially or partially coincides with the photo catalytically active band gap of the Ti02 in the anatase phase.

According to an eleventh aspect of the invention there is provided a method of increasing the content of rutile and/or TiO2-B phases in a TiO2 product including or comprising : preparing a Ti02-containing product as substantially as previously described wherein the Ti02 phase is predominantly or at least partially anatase or is predominantly or at least partially Ti02-B phase, and heating to increase the Ti02-B and/or rutile content.

Preferably heating to substantially between 200°C to 400° causes or initiates phase change of Ti02-B to anatase phase to titanium dioxide-B and/or rutile phase in the product. Additionally further heating to substantially above 400°C will increase the content of the rutile phase in the product.

Preferably the Ti02 undergoes a phase change substantially entirely to rutile at temperatures substantially higher than 500°C.

Alternatively addition of substantially up to 50% by weight silica results in stabilisation of the anatase and/or Ti02-B phase thereby requiring heating to over 600°C to initiate and/or complete the transformation to rutile phase.

According to a twelfth aspect of the invention there is provided a TiO2-containing product substantially prepared according to the method previously described.

According to a thirteenth aspect of the invention there is provided a TiO2-containing product prepared substantially as herein described with reference to any one or more of the accompanying examples. According to a fourteenth aspect of the invention there is provided a TiO2 particulate material substantially prepared according to the method previously described.

According to a fifteenth aspect of the invention there is provided a TiO2 particulate material prepared substantially as herein described with reference to any one or more of the accompanying examples. According to a sixteenth aspect of the invention there is provided a TiO2-containing coating solution substantially prepared according to the method as previously described.

According to a seventeenth aspect of the invention there is provided a TiO2-containing coating solution prepared substantially as herein described with reference to any one or more of the accompanying examples. According to a eighteenth aspect of the invention there is provided a TiO2-containing coated substrate substantially prepared according to the method as previously described.

According to a nineteenth aspect of the invention there is provided a TiO2-containing coated substrate prepared substantially as herein described with reference to any one or more of the accompanying examples. According to a twentieth aspect of the invention there is provided a TiO2-containing hardened film substantially prepared according to the method as previously described. According to a nineteenth aspect of the invention there is provided a TiO2-containing hardened film prepared substantially as herein described with reference to any one or more of the accompanying examples.

According to a twentieth aspect of the invention there is provided a TiO2-containing patterned film substantially prepared according to the method as previously described.

According to a twenty-first aspect of the invention there is provided a TiO2-containing patterned film prepared substantially as herein described with reference to any one or more of the accompanying examples.

According to a twenty-second aspect of the invention there is provided a method of preparing a TiO2-based photocatalyst including or comprising the following steps:

1) preparation of a solution containing colloidal particles which contain titanium ions wherein the particles are stabilised by oxalic acid, or stabilised by reaction with oxalic acid,

2) further processing of the solution to obtain the photocatalyst.

Preferably the Ti02-based photocatalyst is a Ti02 particulate material, and the further processing includes a gelling and a curing step.

Preferably the Ti02-based photocatalyst is a Ti02 coating or film on a substrate, and the further processing includes preparation of a coating solution and application of the coating solution to the substrate, and a gelling and a curing step.

Preferably the Ti02 phase in the particulate material, coating or film, at least initially, includes, is predominantly or is substantially anatase.

Preferably the Ti02-based photocatalyst acts as a photocatalyst upon irradiation of or exposure to UV light. Preferably the Ti02-based photocatalyst is metal or metal-oxide doped, preferably the metal is selected from Pt, Pd, Cu or Ag.

Preferably the Ti02-based photocatalyst can be used to photocatalytically degrade organic compounds and wherein the degradation occurs via application of or exposure to UV radiation, and/or the Ti02-based photocatalyst can act as a hydrophilic surface when coated on a substrate.

According to a twenty-third aspect of the invention there is provided a TiO2-based photocatalyst prepared substantially according to the method as previously described.

According to a twenty-fourth aspect of the invention there is provided a TiO2-based photocatalyst prepared substantially as herein described with reference to any one or more of the examples.

According to a twenty-fifth aspect of the invention there is provided a method of preparing B phase TiO2, including or comprising the following steps: 1) preparation of a solution containing colloidal particles which contain titanium ions wherein the particles are stabilised by oxalic acid, or stabilised by reaction with oxalic acid, and

2) further processing of the solution to obtain Ti0 predominantly or substantially in the Ti02-B phase, and 3) heating of the Ti02 to substantially between 200-300°C.

Preferably the further processing step 2) includes removal of the solvent and/or a gelling step and/or a curing step.

Preferably step 1) is substantially according to one or more of the methods described previously in the first-fourth aspects of the invention. Preferably there is a further step 4) of heating beyond 450°C provide Ti02 in the rutile phase.

According to a twenty-sixth aspect of the invention there is provided B phase TiO2, prepared substantially according to the method previously described.

According to a twenty-seventh aspect of the invention there is provided B phase TiO2, prepared substantially as herein described with reference to any one or more of the examples.

Although the present invention is broadly as defined above, it is not limited thereto and also includes embodiments of which the following description provides examples.

BRIEF DESCRIPTION OF THE DRAWINGS

In particular, a better understanding of the invention will be gained with reference to the accompanying drawings and figures in which: Figure 1 shows a thermal analysis (TGA and DTA) of the powder prepared from gelling the sol in

Example 5; Figure 2 shows X-ray diffraction (XRD) patterns of the powder prepared from gelling the sol in

Example 9 with no silica added; Figure 3 shows the infrared spectra of the film prepared as in Example 10 and cured by UV light; Figure 4 shows the effect of added Si02 on the photoactivity and surface area using a 2M sol of the invention; Figure 5 shows the change in photoactivity with a catalyst loading using 2M sol of the invention +

50% Si02 coated on woven glass fibre; Figure 6 shows the effect of humidity on the photoactivity using two coatings of 2M sol of the invention + 50% Si02 coated on woven glass fibre;

Figure 7 shows the UV degradation of some surfactants on Ti02 films followed by I.R spectroscopy; Figure 8 shows the x-ray diffraction spectrum of Ti02-B containing material; Figure 9 shows the surface profile of a Ti02 patterned film;

Figure 10 shows the scanning electron micrograph (SEM) of a Ti02 patterned film; Figure 11 shows the photodecomposition of Rhodamine B dye on Ti02 film; Figure 12 shows the photodecomposition of ethylene gas on platinised Ti0 photocatalyst cloth; Figure 13 shows the photothermal decomposition of ethylene gas on a platinised Ti02 photocatalyst cloth; and Figure 14 shows the photothermal decomposition of toluene gas on a platinised Ti02 photocatalyst cloth.

DESCRIPTION OF THE INVENTION

As defined above, the invention relates to processes of preparing solutions containing colloidal particles which contain titanium ions (ie titanium-containing sols), and to processes for preparing titanium dioxide containing materials. In particular xerogels (a gel in which the solvent has been removed by evaporation at an ambient temperature), powders and coated films can be prepared from the solutions. Further, the invention also relates to the application of the titanium dioxide containing materials.

A. Preparation of Titanium -Containing Materials

Al- General

The applicants have found that titanium-containing colloidal solutions stabilised by oxalic acid can be prepared by stablisation or peptization. Peptization is the process by which colloidal sols are stabilised usually by addition of electrolytes. In the case of Ti02 a pH of approximately <4 is required, thus acidic conditions are generally employed. These colloidal solutions have certain advantageous properties that render them highly suitable for use in preparing titanium dioxide-containing materials.

In particular, the applicants have found that titanium dioxide-containing materials prepared from such colloidal solutions do not require firing at high temperatures in order to have properties that make them suitable for use in such application as photocatalysts. This is because titanium dioxide prepared by removal of the solvent from such colloidal solutions has been found to contain or to comprise titanium dioxide directly in the anatase crystalline form. This form is primarily required for titanium dioxide to have photocatalytic properties in the UV range, or is at least the most convenient photocatalytic form of titanium dioxide.

Typically, conversion of titanium dioxide from the amorphous form, which is the typical phase produced initially in other processes, to the anatase crystalline form has generally required heating to temperatures of at least 300°C to 400°C. In contrast, titanium dioxide materials prepared from the colloidal solutions of the present invention can be cured simply by exposure to solar light or an ultraviolet light source. Importantly, irradiation of the materials is effective to remove the oxalic acid present, as the titanium dioxide, which is already in the anatase form, photocatalyses decomposition of the oxalic acid. The ability of the titanium dioxide materials to be cured without the need for high temperatures enables the preparation of composite materials comprising a substrate coated with a titanium dioxide film in which the substrate used does not need to be heat resistant. Thus, composite materials in which the substrate is, for example, a thermoplastic material or wood, can be prepared.

Alternatively, the titanium-dioxide containing materials of the invention can be cured by heating to appropriate temperatures. Generally, a temperature of as low as about 200°C will be sufficient to decompose the oxalic acid present in the material and yield a product in which the titanium dioxide is in the anatase form. Further, anatase, Ti02-B, rutile phase or a mixture can be obtamed, depending on the amount of oxalic acid used in the preparation and on the firing temperature. Thus, if crystalline Ti02 as the anatase phase or a mixture of anatase and titanium dioxide B is desired, the titanium dioxide material would generally be cured at a temperature of from about 200°C to 400°C. Above 400°C a mixture of anatase and rutile will generally be obtained, which will transform completely to rutile at high temperatures, as is known in the art.

The production of the titanium dioxide materials is carried out in two stages- firstly preparation of titanium containing colloidal solutions or sols, and then the preparation of the titanium-containing materials.

A2. Production of Titanium Sols

The solutions containing colloidal particles containing titanium ions of the present invention (the titanium sols) may be prepared by reacting a mixture containing a hydrolysable titanium-containing compound and oxalic acid, in a reaction medium which comprises either water or a mixture of water and an alcohol.

The titanium-containing compound used may be a titanium-containing compound that is hydrolysable in water or base. Also, the use of mixtures of two or more hydrolysable titanium-containing compounds is within the scope of the present invention.

It is particularly preferred that the water hydrolysable titanium-containing compound is a compound of the formula Ti(OR) , where R is a C2-C6 linear or branched chain alkyl group. Two preferred titanium- containing compounds are titanium tetraisopropoxide and titanium tetrabutoxide, which are hydrolysable in water.

Alternative titanium-containing compounds that may be used include TiCl4 and TiOS04, which can be hydrolysed using a base prior to reaction with oxalic acid. In this case the hydrolysed products (hydrated titania or titanic acid) would preferably be filtered and washed, preferably with deionised water, before reaction with the oxalic acid. The hydrolysed product is more preferably used as slurry without drying. The hydrolysable titanium containing compound may, for example in the case where the compound is of the formula Ti(OR) , be first combined with a solution of oxalic acid in alcohol followed by addition of water. Alternatively, the titanium-containing compound may just be added directly to water (or to a mixture of water and an alcohol), then oxalic acid is added to the so formed slurry. Otherwise the titanium-containing compound may be added to a solution of oxalic acid in water or in water/alcohol solution.

The oxalic acid may be either anhydrous oxalic acid, or hydrated oxalic acid, such as H2C 04. 2H20. It is preferred that the amount of oxalic acid is such as to provide a mole ratio of oxalic acid: titanium in the range of about 0.2:1 to about 1:1 to get the sols. Below 0.2 ratio either very white colloids or unstable colloids are obtained.

As indicated above, the reaction medium can comprise either water or a mixture of water and an alcohol. It is preferred that the water content is such as to provide a mole ratio of water: titanium in the range of from about 200:1 to about 800:1, more preferably from about 400:1 to about 600:1. Below 200:1 ratio peptization becomes difficult and may produce unstable colloids. The preferred amount of alcohol present is such as to provide a mole ratio of alcohol: titanium of from zero to 100:1, more preferably 10:1 to 50:1.

It is preferred that the alcohol, when present, is a mono hydroxyl aliphatic alcohol having the formula ROH, where R is a Cj to C4 linear or branched alkyl group, such as ethanol or t-butanol.

In order to form a sol, ie a solution containing colloidal particles containing titanium ions, the reaction mixture is preferably stirred or agitated, at a temperature between ambient temperature to near the boiling point of the mixture, more preferably at a temperature between about 40°C and about 80°C.

The sol can be stored at any desired concentration level, preferably up to about 32% by weight Ti02. It is however preferred that if a concentrated sol is prepared, that this be then diluted with water to give a concentration of about 2-20% by weight as Ti02 for preparation of thin films.

The reaction time required to form a colloidal solution will depend on the composition and concentration of the reaction mixture. However, in general, the required reaction time will range from about 15 minutes up to about 3 hours.

The sols thus prepared will contain colloidal particles of a submicrometer to a few nanometer sizes, or less and containing titanium ions, with the particles being stabilised by oxalic acid. Without wishing to be bound by any theory, it is thought that the structure of the colloidal particles is likely to be nTiO2.H2C204 or similar, where n is a number greater than or equal to 1, ie Ti02 particles stabilised by oxalic acid or any of its dissociated forms, and that the oxalic acid prevents the titanium dioxide precipitating out of the solution.

A3- Preparation of the Titanium Dioxide Solid Materials

Once prepared, the sols may be irradiated by UV light to reduce the concentration of oxalic acid in the sol, especially when the oxalate concentration is about 0.5 mole ratio or higher relative to Ti. The UV light may conveniently be provided by a mercury lamp or a xenon lamp or any other intense UV source with a wavelength less than 400 nm.

The titanium-containing colloidal solutions may, by removal of the solvent, be used to prepare titanium dioxide or titanium dioxide-containing materials, including titanium dioxide powders and composite materials comprising a substrate coated with a film of titanium dioxide.

In one embodiment of this invention, if a titanium dioxide powder or film of higher surface area is to be prepared, it is usually preferred that the sol is first mixed with colloidal silica, in an amount of between about 1 and 99 weight percent relative to titanium, preferably from 30 to 60 wt % relative to titanium. The concentration of colloidal silica used can have any desired concentration, but is preferably between about 1 and 50% by weight.

A further option within the invention is to use a titania sol prepared according to the above, and further mix it with a hydrolysable or partially hydrolysable silane compound of a formula RSiX3 and SiXt (where R is a simple or functionalised organic group and X could be a halide or an alkoxide groups that may exist together) before causing the sol to gel. Such a silane can be added as neat or as solution in an aqueous or organic solvent that is miscible with water, such as ethanol, acetone, etc. Such a silane material can form a linkage between titania particles through -Ti-O-Si-O-Ti- bonding. This can suppress crystal growth of the titania particles as well as add better abrasion properties to the photocatalyst.

To prepare a xerogel or a powder, the sol is then preferably caused to gel. This may be achieved by evaporating the solvent at room temperature or above, or under a vacuum with or without heating. Alternatively, the sols can be caused to gel by adding a dilute mineral acid solution, such as HC1, HN03 or H2S04, or an alkaline solution, such as KOH, ammonia, sodium carbonate or tetraalkylammonium hydroxide. These gels can if desired be redissolved in acidic solutions, such as sulphuric, nitric, oxalic, citric, lactic and tartaric acids, etc. at room temperature or by heating, depending on the type and concentration of the acid. The process of redissolving the gelled material is particularly important in film patterning, as it will be described later. The gels can be cured to remove the oxalic acid and form titanium dioxide containing materials or films, by exposure to solar light or a UV light source, or by heating at appropriate temperatures. If a UV source is used, this can be a mercury lamp, a xenon lamp, a black light lamp, or other UV source. The wavelength of the light can be below 400 nm to coincide with the band gap of the titania photocatalyst. The required curing time will depend on the film thickness, the amount of oxalic acid to be decomposed, the wavelength of the radiation and its intensity. The UV cured material will contain Ti02 in the anatase form. The curing process of a film prepared as in Example 10 below was monitored by infrared spectroscopy (Figure 3).

Alternatively, the gels can be cured by heating at appropriate temperatures as will be known in the art, to form anatase, Ti02-B or rutile. At temperatures as low as 200°C to 400°C, crystalline Ti02, as the anatase phase or a mixture of anatase and titanium dioxide-B, is obtained. Above 400°C a mixture of anatase and rutile will be obtained, which will transform completely to rutile at high temperature. This was monitored using thermal analysis (TGA, DTA) (Figure 1) and powder X-ray diffraction (XRD) (Figure 2). In this case the crystallite size gradually increased from 37 A in the xerogel to 58 A after heating at 300°C for 1 hour, then rapidly increased above 100 A accompanied with the formation of rutile. When silica (Nalcogel colloidal silica) was present with the titanium dioxide, the anatase form could be stabilised at higher temperature with a small change in the anatase crystallite size. As one can see from the examples given below, if the material contains 50% by weight silica the anatase phase can be stabilised up to 600°C and the anatase crystallite size will change from 37A in the xerogel to only 56A after heating at 600°C for 1 hour. Therefore inclusion of silica into the photocatalyst can stabilise the anatase phase and increase the surface area of the material, thus improves its photocatalytic activity (Figure 4). The highest surface area and photoactivity obtained was with the 50% by weight Si02 for which the specific surface area was 246.3 m2/g according to BET method for nitrogen sorption. The pore size distribution according to BJH analysis of the nitrogen desorption isotherm showed a maximum at 35 A pore diameter and cumulative pore volume of pores between 17 and 100 A of 0.1125 cmVg with the average pore diameter of 28.2 A. However, for the pure titania powder the surface area was 153 m2/g according to BET method. The pore size distribution according to BJH analysis showed a smaller maximum at 34.3 A pore diameter and cumulative pore volume of pores between 17 and 100 A of 0.02254 cm3/g with the average pore diameter of 24.5 A. It is clear that blending amorphous silica can change the surface properties and increase the surface area of the material described in this invention, which is important for adsorption of pollutants.

Film Production

In order to prepare titanium dioxide films, the titanium-containing colloidal solutions may initially be mixed with one or more compounds that enhance the film-casting process to produce thicker and more abrasion resistant films. Water soluble alcohol, as much as 50%, has been found to enhance the film- forming process. In particular methanol and ethanol gave better results in spray coating. The sols may also be mixed with any proportion of water-soluble or alcohol-soluble ketones, such as acetone and acetylacetone.

Further, the sols may be mixed with any proportion of organic acids. The organic acid can be mono-, di- or multi-functional and it may also contain hydroxyl groups. Such acids include for example acetic, lactic, tartaric, citric, maleic, malic, malonic, diglycolic, benzoic, 1,2,4,5-C6H2 (COOH) , EDTA, and mixtures thereof.

The sols may also be mixed with any proportion of water-soluble aliphatic or aromatic alcohols, diols or polyols. Examples of such compounds include ethanol, propanol, ethylene glycol, glycerol, polyethylene glycol, polyvinylalcohol, phenol, catechol, polysaccharides and other polyols as will be known by persons skilled in the art, or a mixture of the same.

The sols may also be mixed with any proportion of ethanolamines, such as monoethanolamine, diethanolamine and triethanolamine, or a mixture thereof.

When such acids and alcohols are added together to the sol in a certain quantity, the sol can be coated on a substrate and heated to around 150°C to give a polymeric hard film which allows the coated substrate to be easily handled. This characteristic has many applications, especially for example, in the robotic industry. This can be heated further to decompose the organic material and produce the anatase coating.

The applicants also prefer blending of amorphous silica by addition of silica colloid and/or silane compounds as mentioned earlier to the titanium dioxide colloid prepared in this invention. Such silane compounds may act as particle couplers to help improving the film thickness and getting more abrasion resistant films, which then either be cured under UV irradiation or heating to decompose any organic residues.

In addition, and especially if the film is to be formed on a hydrophobic surface such as some polymer surfaces, the sols may be mixed with any proportion of surfactant. The surfactant can be chosen from but not limited to the Brij series, Triton series, Tergitol series, Pluronic series, potassium dodecyl sulphate, or any other surfactant that does not cause gelling. Preferably, the surfactant concentration is between 0.01 to 5% by weight relative to Ti02.

Coated Substrates

The sols thus prepared can be coated on a variety of substrates. Examples of such substrates include glass, quartz, glass fibre, woven glass fibre, ceramics, silicon wafers, metals, polymer surfaces (such as polyethylene or polyester), wood, or building materials such as mortar, brick, tiles, or concrete. The coating method used may be any suitable method known in the art, such as spin-coating, dip-coating or spraying.

It is also preferred to apply a protective layer of amorphous silica or alumina on the substrate before coating with the photocatalyst, especially if the substrate consists of organic materials such as a polymer that could be deteriorated by the photocatalyst coating. The same method can be done with glass and other supported films that are prepared by heating. The precursors for amorphous silica and alumina can be prepared by hydrolysing a silicon alkoxide or an aluminium alkoxide in acidic solutions as is known to those who are skilled in the art. For examples precursors for amorphous silica and alumina can be chosen from the series tetraalkoxysilanes, alkoxychlorosilanes and aluminium trialkoxides but are not limited to these. It is more preferred that the alkoxy radicals would have low carbon backbones of C1-C5.

The films that are coated with the photocatalyst can be cured as described above, ie by exposure to solar light or a UV light source, or by heating at appropriate temperatures.

Fine Patterned Films

In the present invention, the applicants have been able to produce fine line patterns of less than 4 micrometer wide with very sharp edges using a low intensity black light lamp. This will enable the formation of Ti02 patterns on polymeric substrates.

In one form of this invention it is possible, by utilising the photocatalytic properties of the titanium dioxide containing material as prepared by the present method, to produce a substrate coated with films having different patterns.

The coating solution may be chosen from any combination of the titania colloid with a silica colloid, a hydrolysable or partially hydrolysable silane and a surfactant. However it is preferred that the coating solution will produce a film which contains 50 to 100%) by weight titania after curing. The titania content of the coating solution will be chosen so that it produces the required thickness of the patterned film. It is also preferred to apply only one layer to get sharper and clearer patterns. The patterning process comprises two steps. In the first step, parts of the film may be masked and the unmasked parts are exposed to an ultraviolet light. This will photocatalytically destroy the oxalic acid and other organic materials present in the titanium oxide of the unmasked portions.

The next step is to develop the film by acid treatment. The destruction of the oxalic acid in the unmasked parts renders those parts of the film insoluble, whereas the parts of the film that have not been exposed to UV light can be dissolved using a suitable acid solution or any material that reacts with or dissolves oxalic acid and or the titanium dioxide-containing gel, since such parts of the film are not cured. The acid solution may be any dilute mineral acid, organic acid solution or an acidic salt solution. Preferably, the acid is oxalic, lactic, citric, tartaric or sulphuric acid. The acidic salt can be, for example, ammonium sulphate or aluminium sulphate. Other materials such as hydrogen peroxide may also be used to develop the patterns. Additionally or alternatively a radiational or mechanical method such as ultrasonication can be used to develop the patterned film by removing the uncured parts.

In this way titanium dioxide films having very fine patterns of few micrometers wide or less and submicrometer to few nanometer thick can be produced on a variety of substrates, including plastic and polymeric surfaces, since it is done at room temperature and low level UV light (Figure 9, 10). This process may find a particular industrial applicability in the electronics industry such as field-effect transistors and other microdevices.

Doping

Here we describe at least two methods of dispersing platinum and other metal particles by photo- and chemical reduction in Ti02 films and powders that are prepared in this invention.

The properties of the titanium dioxide-containing powders and films, for example the photocatalytic properties, may be enhanced by doping with a metal salt or complex. Suitable dopants will be known to those persons skilled in the art.

The composite may be either heated at a suitable temperature to form the metal oxide or UV irradiated to form metal particles inside the titanium dioxide or some cases can produce metal oxides. The addition of a soluble metal salt or complex may either be directly to the sols or by impregnation of the powders and films themselves with an aqueous or alcoholic solution of the metal salt for a sufficient time to allow adsorption. When the metal is chosen from the group Pd, Pt, Ag and Cu, the adsorbed metal salt or complex can be either thermally decomposed or photocatalytically decomposed under UV light. The photocatalytic doping process may take between few minutes to several hours. The photocatalytic process will involve photooxidation of the organic radical of the metal precursor and the photoreduction of the metal ion to zero oxidation state whereby the metal particles are dispersed uniformly on the surface of the catalyst particles. The final metal content in the photocatalyst is preferably less than 2% by weight and more preferably between 0.2 to 0.5 % by weight. Above 0.5% by weight doping the activity of the photocatalyst may marginally increase.

In this method the preferred precursor for Pd and Pt are the hexachloro-complexes. It is preferred to mix these precursors with a sacrificial compound, more preferably the sacrificial compound is a low carbon organic compound such as formaldehyde, formic acid, methanol or ethanol that is added in excess relative to the doping metal. For example, if platinum and formaldehyde are to be used, the more preferable molar ratio is about 1:5 of Pt: formaldehyde. For silver deposition the applicants prefer to use either silver acetate or silver nitrate, although other soluble silver compounds can be used. The precursor solutions can be added either to the colloid or impregnated in the catalyst particles or films after curing. No sacrificial agent is needed in this case. The colour of the silvered catalyst ranges between light grey to black.

In this invention the preferred copper precursors are copper acetate and copper nitrate, although other salts such as the sulphate can be used. The copper precursor can be added to the colloid before gelling or impregnated in the photocatalyst particles or films after gelling and curing. The colour of the catalyst will change from light green to bronze due to the reduction of Cu(II) to Cu(0) after exposure to UV light.

In another embodiment reduction of the metal precursor that is adsorbed on the titanium-containing catalyst can be performed by exposing such a catalyst to a dilute hydrazine hydrate solution for a sufficient time to allow the complete reduction of the metal to zero valency. In this case it is preferred to wash the catalyst with water to remove the excess of hydrazine. In this method hydrazine can penetrate into the catalyst particles or grains and reduce the metal precursor that is adsorbed inside the grains, whether the particles are of pure titania, a titanium-containing material, or silica particles.

B. Application of titanium dioxide materials

The titanium dioxide powders, grains and composite materials containing titanium dioxide materials have a number of applications.

For example, the materials will perform as photocatalysts. The material is able to decompose organic compounds or pollutants in air and water under solar radiation or UV light. In particular the undesirably carbon structures are broken down into relatively harmless C02 and H20. Dyes can be photocatalytically discoloured or bleached using the materials prepared in this invention when irradiated with sunlight or artificial UV light. In this invention we present for example, a method for preparing and supporting a photocatalyst that is capable of reducing ethylene concentration rapidly and efficiently.

A particular example includes the filtering of ethylene (ethene) gases from horticultural storage facilities. This is a colourless gas produced by some fruits as they ripen. However, this gas also causes premature ripening of other fruits stored in the same facility. An example is the storage of apples and kiwifruit, where the former produces ethene that prematurely ripens the latter. This is a significant issue for horticultural exporters, as it may damage their product before it reaches the market.

In addition, the titanium dioxide films will have superhydrophilic properties when they are first prepared. This hydrophilicity is maintained by exposure to solar light or UV light, with a contact angle close to zero. This hydrophilicity is particularly useful for such applications as anti-fogging mirrors and glass windows, where the hydrophilic surface will prevent the formation of small water droplets, that cause the fogging.

Furthermore, the titanium dioxide-containing materials have anti-microbial activity, including activity against bacteria, viruses and fungi. These properties may be utilised for example in forming a surface such as a bench top, or tiles coated with a film of titanium dioxide, to reduce or eliminate the growth of micro-organisms.

The advantages of the applicant's invention include the following: - the ability to coat a wide range of surfaces including plastics and other thermally unstable substances curing within 30 minutes under sunlight and les under UV light source reduced costs related to equipment, energy savings and plant operation ability to produce an abrasion-resistant finish at higher temperatures ability to produce large sample sizes easily - coatings have high porosity and surface area ensuring high photocatalytic activity although high temperatures are needed to ensure that the material or coating produced is abrasion resistant, relatively low temperatures can be used where abrasion resistance is not an issue - for example in an air filter where the material does not come into physical contact with anything other than air or gases - extensive testing has demonstrated that the Ti02 material is higly effective at breaking up ethylene and other workplace compounds. Decomposition of these materials has improved from 30% to 95% per hour, illustrating the effectiveness of this invention as a scrubber.

The invention will now be described in more detail with reference to the following non-limiting examples.

C - EXAMPLES

Example 1

Preparation of titania sol using titanium tetraisopropoxide (TTD?) and UV light 14.2 g of TTEP was added to 3.15 g of oxalic acid dihydrate solution in 20 ml absolute ethanol. The mixture was stirred for 10 minutes then solvent was evaporated under vacuum. Water was added to the white solid and the mixture was stirred at 75°C to peptize it into a clear sol. The solution then was irradiated by a UV light using a mercury lamp for 3 hours. During that the amount of oxalic acid dropped to half its original concentration as determined by permanganate titration.

Example 2

Preparation of titania sol using in situ α-titanic acid and 0.5 mole ratio of oxalic acid α-Titanic acid was obtained by hydrolysing 14.2 g TTIP in 100 ml water. 3.15 g of oxalic acid dihydrate was added and the mixture was stirred at 70°C to form a colourless sol.

Example 3

Preparation of titania sol using α-titanic acid prepared from TTIP and 0.5 mole ratio of oxalic acid

14.2 g of TTIP was added to oxalic acid solution in water (150 ml). The mixture was stirred at 70°C to 10 form the sol as described in Example 2.

Example 4

Preparation of titania sol using α-titanic acid from titanyl sulfate

Titanyl sulphate solution was hydrolysed with dilute ammonia solution to get a white precipitate, which 15 was filtered and washed with distilled water until it became free of sulphate. The resulting slurry was kept in a closed container and analysed for the content of Ti02 by heating a specimen in a furnace to 500°C. 21 g of α-Titanic acid slurry (19% by weight Ti02) was added to 200 ml of water containing 3.15 g of oxalic acid dihydrate. The mixture was stirred at 70°C to form a bluish-white colloid after 1 hour. Powder XRD measurement after gelling and heating to 200°C showed the presence of anatase 20 phase. Anatase diffraction lines became sharper after heating to 300°C for 30 minutes.

Example 5

Preparation of titania sol using α-titanic acid and 0.3 mole ratio of oxalic acid

1.42 g of TTEP was hydrolysed in 40 ml water to form α-titanic acid. 0.19 g of oxalic acid solution in 25 water was added and the mixture was stirred at 65-70°C to get a colloidal solution. Powder XRD showed the presence of anatase phase.

Example 6

Preparation of titania sol using α-titanic acid and 0.25 mole ratio of oxalic acid

30 14.2 g of TTEP was added to oxalic acid (1.57 g) solution in water (400 ml). The mixture was stirred at 65°C to get a bluish-white colloid. Anatase phase was detected in the xerogel prepared once the solvent was removed.

Example 7 35 Preparation of titania sol using titanium tetraisopropoxide (TTD?) and 0.5 mole ratio of oxalic acid.

14.2 g of TTEP was added to 3.15g oxalic acid dihydrate solution in 50ml absolute ethanol. The so formed complex was hydrolysed with 200ml water and the mixture was stirred at 58°C until a clear sol was obtained. Powder XRD after gelling and heating the powder to 200°C showed the presence of a relative 74% Ti02- B phase and 26% anatase phase. The powder heated to 250°C showed that some of Ti02-B was transferred to anatase with ratios of 57% Ti02-B and 43% anatase. Between 300°C to 410°C only well 5 crystalline anatase was obtained. Transfer to rutile phase started to occur after heating at 450°C (Figure 8).

Example 8

Preparation of titania sol using titaniumtetrabutoxide (TTB) and 0.25 mole ratio of oxalic acid.

10 17g of TTB was added to 1.57g oxalic acid solution in 40 ml t-butanol. The complex was hydrolysed with 500 ml of water and the mixture was stirred at 65°C to get a clear sol. The sol was gelled then heated to 350°C to get an off- white anatase powder.

Example 9 15 Preparation of titania sol containing 30% silica

A mixture was prepared as in Example 6. 5.7g of Nalcogel brand 30% Silica colloid was added to the slurry and the resultant mixture was heated at 60°C until a clear colloid was obtained.

Example 10 0 Titania sol from TTD?

14.2 g of TTIP was added to 1.57 g hydrated oxalic acid in 40 ml absolute ethanol and stirred for five minutes at 50°C. The solution was hydrolysed with 400 ml of warm water and the mixture was stirred vigorously at 65°C for two hours. The volume of the resulting clear sol was reduced to 50 ml under vacuum to get 8% by weight or to 25 ml to form 16% by weight colloid. The colloid was filtered using 5 0.4 micrometer Sartorius Minisart filter.

Example 11

Preparation of titanium sol containing 50% silica

A sol was prepared as in Example 10, then the required amount of Nalcogel brand 30% silica colloid was 0 added.

Example 12

Low temperature preparation of photocatalyst grains and powders

16-20%) pure titania colloids or titania-silica colloids were prepared according to the examples above then 5 were caused to gel. If grains are desired it was preferred to gel the colloid at 70-80°C, and if powders were desired it was preferred that the solvent is evaporated under vacuum at 50°C. Heating of such grains or powders at 200°C for one hour produced anatase photocatalysts. The heating time can be made longer than one hour to increase the crystallite size. Example 13

High temperature formation of photocatalyst grains and powders

A 16%) titania silica colloid was prepared as in example 11. The colloid would preferably be gelled at 80°C if grains were desired, but when a powder was desired the solvent was evaporated under vacuum first. The xerogels were heated at 500°C for one hour to get a nanocrystalline anatase containing material, with crystallite size of 8.1 nm.

Example 14 Preparation of thin film and UV curing at room temperature

The sol in Example 10 was coated on a 2x1 cm silicon plate. The film was exposed to mercury UV light at a distance of 5 cm for 30 minutes. Decomposition of the oxalate was monitored by infra red spectroscopy. (Figure 3).

Example 15

Degradation of surfactants on a TiO2 film

One drop of each of 2% by weight of surfactant solutions (Brij 98, Brij 97, Brij 78, Brij 58, Brij 35, Triton X-100, Tergitol 15-S-12) was spread on the film of example 14, each at a time and left to dry at room temperature. The films were subjected to irradiation from mercury UV lamp at a distance of 5 cm. The concentration of the surfactants was monitored using infrared spectroscopy. The absorption peaks for C-H stretching at around 2900 cm"1 and for C-O-C bending at around 1100 cm"1 were found to disappear after 30 minutes of irradiation in the Brij series and after 50 minutes for Triton and Tergitol surfactants (Figures 7a and 7b). This indicates that the Ti02 film cured at room temperature can photodegrade these surfactants under UV irradiation.

Example 16

TiO2 film on a polymer sheet

50x50x3 -mm polyacrylic sheet was spin coated with Ti02 using a 4% sol of Example 10 containing 0.2%

Brij 97 surfactant. The film was irradiated under black light lamp for 2 hours. Coating was repeated in the same way to get a hydrophilic coating.

Example 17

Preparation of thin film and UV patterning

The 4% sol in Example 10 containing 0.1%) Brij 97 was spin coated on a 5x5x0.1 cm glass plate. A black and white image printed on a transparent thin cellulose acetate sheet was placed on the film surface. The plate was exposed to a black light lamp for 6 hours. The film was soaked in a dilute warm lactic acid solution to dissolve the unexposed area of the film and leaving the parts that were exposed to the UV radiation. Example 18

TiO2/25%SiO2 finely patterned film

10 ml of the 8% titania sol of Example 10 was well mixed with O.lg of 2% Brij 97 surfactant and 1 g of glycidoxypropyltrimethoxysilane. The mixture was spin coated on a pre-cleaned 50x50x1 mm glass plate. A finely patterned mask was securely placed on the film and was irradiated from the top at 10 cm distance under a black light lamp for 15 hours. The mask was removed and the film was soaked in a dilute warm lactic acid for 15 minutes. The so formed pattern was traced by a DETAK surface profiler (Sloan Technology Corporation) (Figure 9) and by SEM (Figure 10).

Example 19

A hydrophilic photocatalyst thin film at room temperature

A spin coating mixture, which contains 55% by weight Ti02 and 45%> by weight Si02 was prepared by mixing 12 ml of 8% titania colloid from Example 10, 1.164 g of 30% Nacogel silica colloid, 1.716 g of glycidoxypropyl-trimethoxysilane and 0.1 g of 2% Brij 78 solution. A clean glass plate was spin coated with this mixture at 600 rpm for 2 minutes. The so coated plate was irradiated under black light lamp for 15 hours, after this the film became hydrophilic. Film thickness was 0.5 micrometer and the film did not scratch when tested by H9 pencil.

Example 20

Preparation of heat cured thin film and testing for hydrophilicity

The sol in Example 5 was spin coated on 50x50x1 mm glass plate. The plate was heated to 200°C. After cooling, the plate was coated again and heated. Five coatings were applied in this way. The film was stained with 0.1% oleic acid solution in acetone and left under the sun light. Decomposition of the oleic acid was estimated by the reduction of the contact angle of water on the surface, which was reduced to its original angle of <2 after 6 hours.

Example 21

Preparation of heat cured film on woven glass cloth A piece of woven glass cloth (6x6 cm) was dip coated with the sol as prepared in Example 11. After drying in warm air, the cloth was heated at 210°C for 15 minutes. The coating was repeated to produce multiple layers of the anatase catalyst.

Example 22 Testing the photoactivity of coated glass cloths (degradation of acetaldehyde)

A piece of woven glass cloth prepared in Example 21 was placed in a one litre gas tight reactor with a quartz window at the top. The reactor is provided with a small fan, and a thermohygrometer. The humidity was adjusted to 25 ±1% at 20°C. Acetaldehyde gas was injected in the reactor to give a concentration between 40-60 ppm. After 30 minutes equilibrium in the dark the coated glass cloth was irradiated by a black light lamp at 4 cm distance. The concentration of acetaldehyde was monitored using gas detectors.

The effect of added silica on the activity is shown in Figure 4. The decomposition rate of acetaldehyde versus the number of coatings (thickness of the film) is shown in Figure 5.

Example 23

The effect of humidity on the photodegradation of acetaldehyde The humidity effect on the photodecomposition of acetaldehyde was also tested. The humidity range used for testing was between about 10 and about 90% relative humidity at 20°C. The humidity inside the reactor was changed either by circulating the air through a desiccant or by adding water vapour prior to the injection of acetaldehyde. The effect of humidity on the photoactivity is shown in Figure 6.

Example 24

Photo-platinised photocatalyst glass cloth

A 6x6 cm woven glass cloth was prepared as in Example 21, then it was heated to 500°C for 1 hour. Three millilitres of a doping solution containing 0.1% by weight platinic acid and 0.5% by weight formaldehyde was sprayed on the surface of the catalyst and allowed 5 minutes equilibrium time. The wet glass cloth was irradiated under UV light from a 20- Watt black light lamp for 5 minutes during which the colour of the catalyst changed to grey-black. The glass cloth was washed with distilled water and dried at 80°C to get a platinised photocatalyst.

Example 25 Photo-silvering a photocatalyst glass cloth

A 25 ml of 16% by weight titania colloid was prepared as in example 10 and was well mixed with 1.26 ml of 1% silver nitrate solution producing a colloid with 0.2% by weight silver relative to Ti02. A 6x6 cm glass cloth was coated with this solution and dried at 70°C, then heated at 210°C for 15 minutes. The photocatalyst cloth was irradiated under black light lamp for 30 minutes, during which its colour changed to grey.

Example 26

Silvering a photocatalyst glass cloth using hydrazine

A photocatalyst glass cloth was prepared as in Example 25. After heating to 210°C the cloth was cooled to room temperature then sprayed with a 1% hydrazine hydrate solution. After 5 minutes the cloth was washed with distilled water to remove excess hydrazine, then dried in the oven. Before using this cloth in photocatalysis experiments, it is preferred to irradiate it under UV light to photo-degrade any traces of adsorbed hydrazine. Example 27

Copper doped titania thin film

20 ml of 4% titania containing colloid from Example 10 was mixed with 0.5 ml of 1% copper acetate solution to give 0.2% by weight Cu relative to Ti02. After addition of 0.1% Brij surfactant the solution was spin coated on a clean glass plate. The coated plate was irradiated under black light lamp for 5 hours, then another layer was applied by the same way. This film can be used as antibacterial coating.

Example 28 Photodegradation of a dye

The film that was prepared as in Example 20 by heating to 200°C was stained with 0.5% alcoholic solution of Rhodamine B base. The stained film was placed on a laboratory bench facing sunlight that was coming through a window. The fading of the dye colour was monitored using a Hewlett Packard diode array UV-visible spectrophotometer at wavelength 540 nm. It took 15 min for the dye on the film to completely disappear and become hydrophilic again (Figure 11).

Example 29

Photodegradation of ethylene gas

A 6x6cm platinised photocatalyst cloth was prepared as in Example 24 loaded with 0.09 g of the photocatalyst. The photocatalyst cloth was placed inside a 150 ml gas tight reactor. The humidity inside the reactor was adjusted to 40% at 20°C. 1 ml of 1% ethylene gas in air was injected into the reactor to produce 70 ppmv of ethylene inside the reactor. After 30 minutes equilibrium, the black light lamp was turned on and the ethylene concentration was monitored using a Hewlett Packard 6890 gas chromatograph equipped with an Innowax column and FID detector. After 30 minutes the temperature inside the reactor became 40°C and 97.1% of the ethylene was decomposed (Figure 12).

Example 30

Photothermal degradation of ethylene gas

A 11x17 cm platinised photocatalyst cloth was prepared as in Example 24 which was loaded with 0.6 g photocatalyst. Humidity in the photoreactor was adjusted to 41% at 20°C. 0.6 ml of pure ethylene gas

(26.78 micromole) was injected. After 30 minutes equilibrium, the UV lamp (black light lamp) and heat were turned on with the temperature inside the photoreactor was raised to 85°C. The concentration of ethylene was monitored by GC as in Example 29 and was found to be reduced by 98.9% after 30 minutes

(Figure 13)

Example 31

Photothermal degradation of toluene The same platinised photocatalyst cloth of Example 30 was used and the humidity inside the reactor was 47%o at 20°C. A 2.5 microlitre of pure liquid toluene (20 micromoles) was injected inside the reactor and left to evaporate and adsorbed on the photocatalyst for 40 minutes. The black light lamp and the heat were turned on to raise the temperature inside the reactor to 85°C. The concentration of toluene gas was monitored using the same technique as in Example 29. After 30 minutes the concentration of toluene was reduced by 93.8% and in one hour in was reduced by 99.4% (Figure 14)

While the invention has been described with reference to particular embodiments and examples, those persons skilled in the art will appreciate that variations and modifications may be made without departing from the scope of the invention.

Claims

CLAIMS 35
1. A method of preparing a solution containing colloidal particles which contain titanium ions comprising or including the step of : A. reacting or otherwise stablilising one or more hydrolysable titanium-containing compound(s) with oxalic acid in a reaction medium.
2. A method of preparing a solution as claimed in claim 1 wherein A occurs under conditions such that peptization of the colloidal solution is substantially obtained and substantially maintained.
3. A method of preparing a solution as claimed in claim 2 wherein the conditions include stirring or agitation of the one or more hydrolysable titanium-containing compound(s) with oxalic acid in the reaction medium, at a temperature between ambient temperature to near the boiling point of the reaction mixture.
4. A method of preparing a solution as claimed in claim 3 wherein the temperature is between about 40°C and about 80°C.
5. A method of preparing a solution as claimed in claim 4 wherein the stirring or agitation occurs over a reaction time ranging from substantially 15 minutes up to substantially 3 hours.
6. A method of preparing a solution as claimed in claim 5 wherein the reaction medium comprises water or a water/alcohol mixture and wherein the titanium-containing compound is hydrolysable in water and/or in base.
7. A method of preparing a solution as claimed in any one of claims 1 to 6 wherein, the titanium containing compound is water-hydrolysable and is of the formula Ti(OR)4, where R is a C2-C6 linear or branched chain alkyl group.
8. A method of preparing a solution as claimed in claim 7 wherein the titanium containing compound is titanium tetraisopropoxide and/or titanium tetrabutoxide.
9. A method of preparing a solution as claimed in claim 8 wherein the titanium containing compound is: first combined with a solution of oxalic acid in alcohol, followed by addition of water, or - added directly to water, or to a mixture of water and an alcohol, to form a slurry, followed by addition of oxalic acid, or added to a solution of oxalic acid in water or in a mixture of water and alcohol.
10. A method of preparing a solution as claimed in claim 9 wherein the water-hydrolysable titanium- containing compound is hydrolysed using water prior to reaction with or stabilisation by oxalic acid, to give a hydrolysis product.
5 11. A method of preparing a solution as claimed any in one of claims 1 to 6 wherein the titanium- containing compound is base-hydrolysable and the titanium-containing compound is selected from, but not restricted to, TiCl4 and/or TiOS04.
12. A method of preparing a solution as claimed in claim 11 wherein the base-hydrolysable titanium- 10 containing compound is hydrolysed to a hydrolysis product, using a base prior to reaction with or stabilisation by oxalic acid, the hydrolysis product being filtered and/or washed, to form a slurry before reaction with or stabilisation by, the oxalic acid.
13. A method of preparing a solution as claimed in any one of the preceding claims wherein the oxalic 15 acid is either anhydrous oxalic acid, or hydrated oxalic acid.
14. A method of preparing a solution as claimed in claim 13 wherein the amount of oxalic acid is such as to provide a mole ratio of oxalic acid: titanium in the range of about 0.2:1 to about 1:1.
20 15. A method of preparing a solution as claimed in claim 14 wherein the water content of the reaction medium is such as to provide a mole ratio of water: titanium in the range of from about 200:1 to about 800:1.
16. A method of preparing a solution as claimed in claim 11 wherein the water content of the reaction 25 medium is such as to provide a mole ratio of water: titanium in the range of from about 400:1 to about
600:1.
17. A method of preparing a solution as claimed in any one of the preceding claims wherein, when alcohol is present in the reaction medium the alcohol is a mono hydroxyl aliphatic alcohol having the
30 formula ROH, where R is a Ci to C4 linear or branched alkyl group, such as ethanol or t-butanol.
18. A method of preparing a solution as claimed in claim 17 wherein the preferred amount of alcohol present is such as to provide a mole ratio of alcohol: titanium of from zero to 100:1, more preferably 10:1 to 50:1 in the solution.
35
19. A method of preparing a solution as claimed in claim 18 wherein the solution may be stored at any concentration level prior to further use.
20. A method of preparing a solution as claimed in claim 19 wherein the solution is stored at up to about 32% by weight Ti02, between 0°C and 20°C.
21. A method of preparing a solution as claimed in any one of the preceding claims wherein the oxalate 5 concentration of the solution is at any stage reduced by irradiating the solution with UV light.
22. A solution containing colloidal particles which contain titanium ions prepared substantially according to the method as claimed in anyone of claims 1 to 21.
10 23. An aqueous solution containing colloidal particles which contain titanium ions wherein the particles are stablised by oxalic acid, or stabilised by reaction with oxalic acid.
24. A solution containing colloidal particles which contain titanium ions prepared substantially as herein described with reference to any one of more of the accompanying examples.
15
25. A method of preparing a TiO2-Containing Product comprising or including the steps of:
I. preparation of a solution containing colloidal particles which contain titanium ions wherein the particles are stabilised by oxalic acid, or stabilised by reaction with oxalic acid, and IE. further processing of the solution to obtain the product. 20
26. A method of preparing a Ti02-Containing Product as claimed in claim 25 wherein I occurs under conditions such that peptization of the colloidal solution is substantially obtained and substantially maintained.
25 27. A method of preparing a Ti02-Containing Product as claimed in claim 26 wherein the conditions include stirring or agitation of the one or more hydrolysable titanium-containing compound(s) with oxalic acid in the reaction medium, and at a temperature between ambient temperature to near the boiling point of the reaction mixture.
30 28. A method of preparing a Ti02-Containing Product as claimed in claim 27 wherein the temperature is between about 40°C and about 80°C.
29. A method of preparing a Ti02-Containing Product as claimed in claim 28 wherein the stirring or agitation occurs over a reaction time ranging from substantially 15 minutes up to substantially 3 hours.
35
30. A method of preparing a Ti02-Containing Product as claimed in any one of claims 25 to 29 wherein the Ti02 phase in the product, at least initially, includes, is predominantly or is substantially anatase.
31. A method of preparing a Ti02-Containing Product as claimed in claim 30 wherein the method comprises or includes the steps of:
1) preparation of a solution containing colloidal particles which contain titanium ions wherein the particles are stabilised by oxalic acid or stabilised by having been reacted with oxalic acid, and 5 2) preparation of a colloidal mixture by addition of, or mixing with, one or more additives to the solution, and 3) further processing of the solution to obtain the product.
32. A method of preparing a Ti02-Containing Product as claimed in claim 31 wherein step 1) comprises 10 or includes the method as previously described in any one of claims 1 to 21.
33. A method of preparing a Ti02-Containing Product as claimed in claim 31 or 32 wherein the additives of step 2) include one or more of: a) silica or a silica precursor,
15 b) water, or alcohol, soluble ketone(s), c) organic acid(s), d) water soluble aliphatic or aromatic alcohol(s), diol(s) or polyol(s), e) elhanolamine(s), f) metal precursor(s), 20 g) surfactant(s), h) silane(s).
34. A method of preparing a Ti02-Containing Product as claimed in claim 30 wherein when silica is added it is colloidal silica, and is added in an amount to yield a ratio substantially from 30-60 wt %
25 relative to titanium in the product.
35. A method of preparing a Ti02-Containing Product as claimed in claim 34 wherein the concentration of the colloidal silica is such as to provide between about 1 and 50%) by weight in the product.
30 36. A method of preparing a Ti02-Containing Product as claimed in claim 33 wherein when a surfactant(s) is added, it includes one or more of the Brij series, Triton series, Tergitol series, Pluronic series, potassium dodecyl sulphate, or any other surfactant that does not cause gelling.
37. A method of preparing a Ti0 -Containing Product as claimed in claim 33 wherein when a metal 35 precursor is added, it is a metal salt or metal complex.
38. A method of preparing a Ti02-Containing Product as claimed in claim 37 wherein the metal precursor is a soluble metal salt or complex, of one or more of Pd, Pt, Ag and Cu.
39. A method of preparing a Ti02-Containing Product as claimed in claim 38 wherein the metal is Pd or Pt and the precursor is (but not restricted to) one of the hexachloro-complexes of Pd or Pt.
5 40. A method of preparing a Ti02-Containing Product as claimed in claim 39 wherein the Pd or Pt hexachloro-complex is mixed with a low carbon organic compound as a sacrificial compound, such as formaldehyde, formic acid, methanol or ethanol, the scarificial compound added in excess relative to the precursor metal.
10 41. A method of preparing a Ti02-Containing Product as claimed in claim 38 wherein the metal is Ag and the precursor is one or more of (but not restricted to) silver acetate or silver nitrate.
42. A method of preparing a Ti02-Containing Product as claimed in claim 38 wherein the metal is Cu and the precursor is one or more of (but not restricted to) copper acetate, copper sulphate and copper
15 nitrate.
43. A method of preparing a Ti02-Containing Product as claimed in claim 33 wherein the silane(s) is added neat or as solution in an aqueous or organic solvent that is miscible with water, and is a hydrolysable or partially hydrolysable silane compound of a formula RSiX3> R2SiX 2 and SiX (where
20 R is a simple or functionalised organic group and X could be a halide or an alkoxide group).
44. A method of preparing a Ti02-Containing Product as claimed in claim 31 wherein step 3) includes one or both the steps of: i) causing the solution to gel (a gelling step), 5 ii) curing of the gel (a curing step) to remove or reduce the quantity of the oxalic acid and/or any one or more additives.
45. A method of preparing a Ti02-Containing Product as claimed in claim 44 wherein the gelling step is effected by one or more of:
30 - evaporating the solvent; at room temperature or above; and/or evaporating the solvent under a vacuum, with or without heating; and/or addition of a gelling agent including (but not restricted to) a dilute mineral acid solution such as of HC1, HN03 or H2S04, or an alkaline solution such as KOH, ammonia, sodium carbonate or tetraalkylammonium hydroxide.
35
46. A method of preparing a Ti02-Containing Product as claimed in claim 45 wherein a xerogel is produced from the gelling step.
47. A method of preparing a Ti02-Containing Product as claimed in claim 44 wherein curing of the gel is effected by exposure to UV radiation and/or by heat, and the curing time is determined by the amount of oxalic acid to be decomposed and/or the wavelength of the radiation and/or the intensity of the radiation.
5
48. A method of preparing a Ti02-Containing Product as claimed in claim 47 wherein when UV exposure is employed the wavelength of the UV radiation substantially or partially coincides with the photo catalytically active band gap of the Ti02 in the anatase phase.
10 49. A method of preparing a Ti02-Containing Product as claimed in claim 31 or 32 wherein there is an additional step 4), which includes one or both the steps of: i) impregnation of the titanium containing-product with a metal precursor, (an impregnation step) and/or ii) transformation of any metal precursor to a metal or metal oxide added within step 2)
15 and/or step 4) (a transformation step).
50. A method of preparing a Ti02-Containing Product as claimed in claim 49 wherein the metal of the precursor of step i) is one or more of Pd, Pt, Cu or Ag.
20 51. A method of preparing a Ti02-Containing Product as claimed in claim 50 wherein when the metal precursor is Pd or Pt the metal precursors is mixed with a sacrificial compound of formaldehyde, formic acid, methanol or ethanol, in excess relative to the metal precursor.
52. A method of preparing a Ti02-Containing Product as claimed in claim 49 wherein 25 the transformation step is employed and occurs by one or more of: i) heating at a suitable temperature to transform the metal precursor to the metal or metal oxide, and/or ii) exposing the metal precursor or the Ti02-Containing Product containing the metal precursor, to a dilute hydrazine hydrate solution for a sufficient time to allow the 30 complete reduction of the metal to zero valency, and/or iii) UV irradiation to form metal particles and/or metal oxides within the titanium dioxide.
53. A method of preparing a Ti02-Containing Product as claimed in claim 52 wherein:
• the metal of the metal precursor is Ag, UV irradiation is employed and UV irradiation is stopped 35 substantially when the colour of the Ti02-product changes to light grey-black, and/or
• the metal of the metal precursor is Cu, UV irradiation is employed and UV irradiation is stopped substantially when the colour of the Ti02-Containing Product changes from light green to bronze, and/or • the metal of the metal precursor is Pd, UV irradiation is employed and UV irradiation is stopped substantially when the colour of the Ti02-Containing Product changes to grey to black and/or
• the metal of the metal precursor is Pt, UV irradiation is employed and UV irradiation is stopped substantially when the colour of the Ti02-Containing Product changes to grey to black.
5
54. A method of preparing a Ti02-Containing Product as claimed in claim 52 wherein Hydrazine hydrate solution exposure is employed and the Ti02-product is then washed with water to remove the excess . hydrazine.
10 55. A method of preparing a Ti02-Containing Product as claimed in claim 31 or 32 wherein the final metal content in the Ti02 of the Ti02-product is less than 2%> by weight.
56. A method of preparing a Ti02-Containing Product as claimed in claim 55 wherem the final metal content in the Ti02 of the Ti02-product is between 0.2 to 0.5 % by weight.
15
57. A method of preparing a Ti02-Containing Product as claimed in claim 31 or 32 wherein sometime prior to step 3) the oxalate concentration of the solution is reduced by irradiating the solution with UV light.
20 58. A method of preparing a particulate material of or containing TiO2 comprising or including the steps of:
I. preparation of a solution containing colloidal particles which contain titanium ions wherein the particles are stabilised by oxalic acid, or stablising by reaction with oxalic acid,
El. further processing of the solution to obtain the particulate material. 25
59. A method of preparing a particulate material of or containing Ti02I. occurs under conditions such that peptization of the colloidal solution is substantially obtained and substantially maintained.
60. A method of preparing a particulate material of or containing Ti02as claimed in claim 59 wherein the 30 conditions include stirring or agitation of one or more hydrolysable titanium-containing compound(s) with oxalic acid in the reaction medium, at a temperature between ambient temperature to near the boiling point of the reaction mixture.
61. A method of preparing a particulate material of or containing Ti02 as claimed in claim 60 wherein the 35 temperature is between about 40°C and about 80°C.
62. A method of preparing a particulate material of or containing Ti02 as claimed in claim 61 wherein the stirring or agitation occurs over a reaction time ranging from substantially 15 minutes up to substantially 3 hours.
5 63. A method of preparing a particulate material claimed in 58 wherein the particulate material is partially or substantially entirely Ti02.
64. A method of preparing a particulate material as claimed in claim 63 wherein the Ti02 phase in the particulate material, at least initially, includes, is predominantly or is substantially anatase.
10
65. A method of preparing a particulate material as claimed in claim 58 or 64 wherein the method comprises or includes the steps of:
1) preparation of a solution containing colloidal particles which contain titanium ions wherein the particles are stabilised by oxalic acid or stablisied by having been reacted with oxalic acid, 15 2) preparation of a colloidal mixture by addition of one or more additives to the solution,
3) further processing of the colloidal mixture to obtain the particulate material.
66. A method of preparing a particulate material as claimed in claim 65 wherein step 1) comprises or includes the method as previously described in any one of claims 1 to 21.
20
67. A method of preparing a particulate material as claimed in claim 65 wherein the additives of step 2) include one or more of: colloidal silica, or a silica precursor, a metal precursor.
25
68. A method of preparing a particulate material as claimed in claim 67 wherein the additives include colloidal silica and it is added in an amount to give a ratio substantially between 30 to 60 weight percent relative to titanium and the concentration of the colloidal silica is between about 1 and 50% by weight.
30
69. A method of preparing a particulate material as claimed in claim 67 wherein the additives include one or more metal precursor and the metal precursor is a soluble metal salt or complex of Pd, Pt, Ag and Cu.
35 70. A method of preparing a particulate material as claimed in claim 69 wherein the metal of the metal precursor is one of:
Ag and the precursor is one or more of (but not restricted to) silver acetate or silver nitrate, and/or - Cu and the precursor is one or more of (but not restricted to) copper acetate, copper sulphate and copper nitrate, and/or
- Pd or Pt and precursor is (but not restricted to) one the hexachloro-complexes of Pd or Pt.
5 71. A method of preparing a particulate material as claimed in claim 70 wherein the metal is Pd or Pt and the Pd or Pt hexachloro-complex is mixed with a low carbon organic compound as a sacrificial compound, of formaldehyde, formic acid, methanol or ethanol, and it is added in excess relative to the metal precursor.
10 72. A method of preparing a particulate material as claimed in claim 71 wherein the metal: sacrificial compound mole ratio is approximately.1:5.
73. A method of preparing a particulate material as claimed in claim 65 wherein step 3) includes: i) a gelling step, and
15 ii) a curing step to remove or reduce the quantity of the oxalic acid and/or one or more other additives.
74. A method of preparing a particulate material as claimed in claim 73 wherein the gelling step is effected by one or more of:
20 - evaporating the solvent; at room temperature or above; evaporating the solvent under a vacuum, with or without heating; addition of a gelling agent including (but not restricted to) a dilute mineral acid solution such as
HC1, HN03 or H2S04, or an alkaline solution such as KOH, ammonia, sodium carbonate or tetraalkylammonium hydroxide. 25
75. A method of preparing a particulate material as claimed in claim 74 wherein a xerogel is produced from or as part of the gelling step.
30 76. A method of preparing a particulate material as claimed in claim 74 wherein curing of the gel is effected by exposure to UV radiation and/or by heat and the curing time is determined by the amount of oxalic acid to be decomposed and/or the wavelength of the radiation and/or the intensity of the radiation.
35 77. A method of preparing a particulate material as claimed in claim 76 wherein UV exposure is employed and the wavelength of the UV radiation substantially or partially coincides with the photo catalytically active band gap of the Ti02 in the anatase phase.
78. A method of preparing a particulate material as claimed in claim 65 wherein there is an additional step 4) which includes one or both the steps of: i) impregnation of the particulate material with a metal precursor, (an impregnation step) and, 5 ii) transformation to a metal or metal oxide of any metal precursor added within step 2) and/or step 4) (a transformation step).
79. A method of preparing a particulate material as claimed in claim 78 wherein the metal of the precursors of step i) is one or more of Pd, Pt, Cu or Ag.
10
80. A method of preparing a particulate material as claimed in claim 79 wherein when the metal precursor is Pd or Pt the metal precursors is mixed with a sacrificial compound of formaldehyde, formic acid, methanol or ethanol, in excess relative to the metal precursor.
15 81. A method of preparing a particulate material as claimed in claim 78 wherein the transformation step occurs by one of more of: i) heating at a suitable temperature to transform the metal precursor to the metal or metal oxide, and/or ii) exposing the metal precursor or the particulate material containing the metal precursor, to
20 a dilute hydrazine hydrate solution for a sufficient time to allow the complete reduction of the metal to zero valency, and/or iii) UV irradiation to form metal particles and/or metal oxides within the titanium dioxide.
82. A method of preparing a particulate material as claimed in claim 81 wherein: 25 - the metal of the metal precursor is Ag, UV irradiation is employed and UV irradiation is stopped substantially when the colour of the particulate material to light grey-black, and/or the metal of the metal precursor is Cu, UV irradiation is employed and UV irradiation is stopped substantially when the colour of the particulate material changes from light green to bronze and/or 30 - the metal of the metal precursor is Pd, UV irradiation is employed and UV irradiation is stopped substantially when the colour of the particulate material changes from grey to black, and/or the metal of the metal precursor is Pt, UV irradiation is employed and UV irradiation is stopped substantially when the colour of the particulate material changes from grey to black.
35 83. A method of preparing a particulate material as claimed in claim 81 wherein hydrazine hydrate solution exposure is employed and the powder is then washed with water to remove the excess of hydrazine.
84. A method of preparing a particulate material as claimed in claim 65 wherein the final metal content in the Ti02 of the Ti02-product is less than 2% by weight and more preferably between 0.2 to 0.5 % by weight.
5 85. A method of preparing a particulate material as claimed in claim 65 wherein before step 3) the oxalate concentration of the solution is reduced by irradiating the solution with UV light.
86. A method of preparing a particulate material as claimed in any one of claims 58 to 85 wherein the particulate material is a powder.
10
87. A method of preparing a particulate material as claimed in any one of claims 58 to 85 wherein the particulate material is granular.
88. A method of preparing a TiO2 coating solution comprising or including the steps of:
15 I. preparation of a solution containing colloidal particles which contain titanium ions wherein the particles are stabilised by oxalic acid, or are stabilised by having been reacted with oxalic acid, and II. further processing of the solution to obtain the coating solution.
20 89. A method of preparing a Ti02 coating solution as claimed in claim 88 wherein I occurs under conditions such that peptization of the colloidal solution is substantially obtained and substantially maintained.
90. A method of preparing a Ti02 coating solution as claimed in claim 89 wherein the conditions include 25 stirring or agitation of one or more hydrolysable titanium-containing compound(s) with oxalic acid in the reaction medium, at a temperature between ambient temperature to near the boiling point of the reaction mixture.
91. A method of preparing a Ti0 coating solution as claimed in claim in claim 90 wherein the a 30 temperature is between about 40°C and about 80°C.
92. A method of preparing a Ti02 coating solution as claimed in claim 91 wherein the stirring or agitation occurs over a reaction time ranging from substantially 15 minutes up to substantially 3 hours.
35 93. A method of preparing a coating solution as claimed in claim 88 or 92 wherein the method comprises or includes the steps of:
1) preparation of a solution containing colloidal particles which contain titanium ions wherein the particles are stabilised by oxalic acid, or are stabilised by having been reacted with oxalic acid, 2) preparation of a colloidal mixture by addition of one or more additives to the solution.
94. A method of preparing a coating solution as claimed in claim 93 wherein step 1) includes or comprises the method as claimed in any one of claims 1 to 24.
95. A method of preparing a coating solution as claimed in claim 93 wherein step 2) includes any one or more of the following: i) Addition of or mixing with silica, or a silica precursor, ii) Addition of or mixing with any proportion of water-soluble or alcohol-soluble ketone(s), iii) Addition of or mixing with any proportion of organic acid(s), iv) Addition of or mixing with any proportion of water-soluble aliphatic or aromatic alcohol(s), diol(s) or polyol(s), v) Addition of or mixing with any proportion of ethanolamine(s), such as monoethanolamine, diethanolamine or triethanolamine, or a mixture thereof, vi) Addition of or mixing with any proportion of surfactant(s), vii) Addition of or mixing with one or more metal precursors), viii) Addition of or mixing with one or more silane(s).
96. A method of preparing a coating solution as claimed in claim 95 wherein silica is added or mixed, it is colloidal silica, and it is added in an amount to give a ratio substantially between 30 to 60 weight percent relative to titanium and the concentration of the colloidal silica is between about 1 and 50% by weight.
97. A method of preparing a coating solution as claimed in claim 95 wherein water-soluble and/or alcohol-soluble ketone(s) is added or mixed, and it is acetone and/or acetylacetone.
98. A method of preparing a coating solution as claimed in claim 95 wherein organic acid(s) is added or mixed and are one or more of acetic, lactic, tartaric, citric, maleic, malic, malonic, diglycolic, benzoic, 1,2,4,5-C6H2 (COOH)4, EDTA, and/or mixtures thereof.
99. A method of preparing a coating solution as claimed in claim 95 wherein water-soluble aliphatic or aromatic alcohol(s), diol(s) or polyol(s) is/are added or mixed and it is/are one or more of ethanol, propanol, ethylene glycol, glycerol, polyethylene glycol, polyvinylalcohol, phenol, catechol, polysaccharides.
100. A method of preparing a coating solution as claimed in claim 95 wherein one or more the surfactant(s) is added or mixed, selected from one or more of the Brij series, Triton series, Tergitol series, Pluronic series, potassium dodecyl sulphate, or any other surfactant that does not cause gelling.
101. A method of preparing a coating solution as claimed in claim 100 wherein the surfactant concentration is between 0.01 to 5% by weight relative to Ti02.
5 102. A method of preparing a coating solution as claimed in claim 95 wherein one or more metal precursor(s) is added or mixed and is a soluble metal salt or complex, of the group of Pd, Pt, Ag and Cu.
103. A method of preparing a coating solution as claimed in claim 102 wherein the metal is one or 0 more of:
- Ag and the precursor is one or more of (but not restricted to) silver acetate or silver nitrate, and/or
- Cu and the precursor is one or more of (but not restricted to) copper acetate, copper sulphate and copper nitrate, and/or 5 - Pd or Pt and precursor is (but not restricted to) one of the hexachloro-complexes of Pd or Pt.
104. A method of preparing a coating solution as claimed in claim 103 wherein the metal is Pd or Pt and the Pd or Pt hexachloro-complex is mixed with a low carbon organic compound as a sacrificial compound, such as formaldehyde, formic acid, methanol or ethanol, which added in excess relative to 0 the metal precursor.
105. A method of preparing a coating solution as claimed in claim 95 wherein a silane(s) is added or mixed, and it is a hydrolysable or partially hydrolysable silane compound(s) of a formula RSiX3, R2SiX2 and SiX4 (where R is a simple or functionalised organic group and X could be a halide or an 5 alkoxide group) and it/they is/are added neat or as a water-miscible solution, at a concentration between 1-50% by total weight.
106. A method of preparing a coating solution as claimed in claim 93 wherein there is the further step 3) of storing the coating solution at any concentration, between 0-20°C. 0
107. A method of preparing a coating solution as claimed in claim 106 wherein the coating solution is stored between 4-15°C.
108. A method of preparing a TiO2-coated substrate comprising or including the steps of: 5 I. preparation of a coating solution as claimed in any one of claims 98 to 107, and π. further processing of the solution to obtain the coated substrate.
109. A method of preparing a coated substrate as claimed in claim 108 wherein the Ti02 phase in the coated substrate, at least initially, includes, is predominantly or is substantially anatase.
110. A method of preparing a coated substrate as claimed in claim 109 wherein the substrate is one or more of (but not restricted to) glass, quartz, glass fibre, woven glass fibre, ceramics, silicon wafers, metals, polymer surfaces (such as polyethylene or polyester), wood, or building materials such as mortar, brick, tiles, or concrete.
111. A method of preparing a coated substrate as claimed in claim 108 wherein step II includes: i) application of the coating solution to a substrate, and ii) a gelling step, and iii) a curing step.
112. A method of preparing a coated substrate as claimed in claim 111 wherein application of the coating solution is effected one of the techniques of spin-coating, dip-coating or spraying.
113. A method of preparing a coated substrate as claimed in claim 112 wherein prior to application of the coating solution a protective layer of amorphous silica and/or alumina is applied to the substrate, or a precursor of amorphous silica selected from (but not limited to) the series tetraalkoxysilanes, alkoxychlorosilanes; or a precursor of amorphous aluminia selected from (but not limited to) the series aluminium trialkoxides and wherein the precursors may consent to the silica or precursor by hydrolysis in acid solution.
114. A method of preparing a coated substrate as claimed in claim 111 wherein curing of the gel is effected by exposure to UV radiation and/or by heat and the curing time is determined by the amount of oxalic acid to be decomposed and/or the amount of silane (if present) and/or the amount of surfactant (if present) and/or the wavelength of the radiation and/or the intensity of the radiation.
115. A method of preparing a coated substrate as claimed in claim 114 wherein when UV radiation is employed the wavelength of the radiation substantially or partially coincides with the photocatalytic band gap of anatase Ti02
116. A method of preparing a coated substrate as claimed in claim 111 wherein the gelling step is effected by one or more of: - evaporating the solvent; at room temperature or above; evaporating the solvent under a vacuum, with or without heating; addition of a gelling agent including (but not restricted to) a dilute mineral acid solution such as HC1, HN03 or H2S04, or an alkaline solution such as KOH, ammonia, sodium carbonate or tetraalkylammonium hydroxide.
5 117. A method of preparing a coated substrate as claimed in claim 108 wherein there is a further step III which includes one or both the steps of: i) impregnation of the titanium containing-product with a metal precursor, (an impregnation step) and/or ii) transformation to a metal or metal oxide of any metal precursor added within step I) 0 and/or step III) (a transformation step).
118. A method of preparing a coated substrate as claimed in claim 119 wherein the metal of the precursors of step i) is one or more of Pd, Pt, Cu or Ag.
5 119. A method of preparing a coated substrate as claimed in claim 118 wherein when the metal precursor is Pd or Pt the metal precursors is mixed with a sacrificial compound of formaldehyde, formic acid, methanol or ethanol, in excess relative to the metal precursor.
120. A method of preparing a hardened Ti02-coated substrate comprising or including the steps 0 of : i) preparation of a coating solution as claimed in any one of claims 88 to 107 and wherein at least both an acid and an alcohol are added to the solution, ii) application of the coating solution to a substrate, iii) heating to around 150°C, 5 iv) further heating to around 450°C to decompose the organic materials and/or to effect sintering of the coating; v) impregnation with a metal precursor followed by UV irradiation and/or heating.
121. A method of preparing a patterned TiO2-coated substrate comprising or including the steps 0 of : i) preparation of a coated substrate as claimed in any one of claims 108 to 119, but prior to any gelling or curing steps (if any), ii) masking one or more regions of the coating , iii) curing of the umnasked region(s) of coating by exposing the unmarked region(s) to an ultraviolet 5 light to photocatalytically destroy the oxalic acid and other organic materials present in the titanium oxide of the unmasked region(s), iv) development of the film.
122. A method of preparing a patterned TiO2-coated substrate as claimed in claim 121 wherein the coating solution produces a film which contains 50 to 100% by weight titania after curing.
123. A method of preparing a patterned Ti02-coated substrate as claimed in claim 122 wherein 5 only one layer of coating solution is applied to obtain sharper and clearer patterns.
124. A method of preparing a patterned Ti02-coated substrate as claimed in claim 121 wherein development of the film is by one or more of: i) application of an acid solution wherein the acid solution is any dilute mineral acid such as
10 sulphuric and/or an organic acid solution such as oxalic, lactic, citric, tartaric and/or an acidic salt solution where the salt is, ammonium sulphate or aluminium sulphate, and/or, ii) application of other materials such as hydrogen peroxide, and/or, iii) a radiational or mechanical method including ultrasonication, and/or iv) any other method for redissolution of the UV - unexposed gel. 15
125. A method of preparing a patterned Ti02-coated substrate as claimed in claim 124 wherein the development occurs at room temperature, or under conditions of heating.
126. A method of preparing a patterned Ti02-coated substrate as claimed in claim 125 wherein there 20 is a final step of sintering the coating.
127. A method of preparing a patterned Ti02-coated substrate as claimed in 126 wherein there may be one or more additional prior step to sintering including one or both of the steps of
- evaporating the solvent; at room temperature or above and/or 25 - evaporating the solvent under a vacuum, with or without heating.
128. A method of preparing a patterned Ti02-coated substrate as claimed in claim 124 wherein curing of the coating is effected by exposure to UV radiation and/or by heat.
30 129. A method of preparing a patterned Ti02-coated substrate as claimed in claim 128 wherein a xerogel is produced as an intermediate or product of the gelling step.
130. A method of preparing a Ti02-Containing Product as claimed in claim 128 wherein US exposure is employed and the wavelength of the UV radiation substantially or partially coincides with
35 the photo catalytically active band gap of the Ti02 in the anatase phase.
131. A method of increasing the content of rutile and/or TiO2-B phases in a TiO2 product including or comprising : preparing a Ti02-containing product as claimed in any one of claims 25-57 wherein the Ti02 phase is predominantly or at least partially anatase, or is predominantly or at least partially Ti02-B phase and heating to increase the anatase and/or rutile content. 5
132. A method as claimed in claim 131 wherein heating to substantially between 200°C to 400° causes or initiates phase change of Ti02-B to anatase phase to titanium dioxide-B and/or rutile phase in the product.
10 133. A method as claimed in claim 132 wherein further heating to substantially above 400°C will increase the content of the rutile phase in the product.
134. A method as claimed in claim 133 wherein the Ti02 undergoes a phase change substantially entirely to rutile at temperatures substantially higher than 500°C.
15
135. A method as claimed in claim 134 wherein addition of substantially up to 50%> by weight silica results in stabilisation of the anatase phase and/or Ti02-B phase thereby requiring heating to over 600°C to initate and/or complete the transformation to rutile phase.
20 136. A TiO2-containing product substantially prepared according to the method as claimed in any one of claims 25-57.
137. A TiO2-containing product prepared substantially as herein described with reference to any one or more of the accompanying examples.
25
138. A TiO2 particulate material substantially prepared according to the method as claimed in any one of claims 58 to 87.
139. A TiO2 particulate material prepared substantially as herein described with reference to any 30 one or more of the accompanying examples.
140. A TiO2-containing coating solution substantially prepared according to the method as claimed in any one of claims 88 - 107.
35 141. A TiO2-containing coating solution prepared substantially as herein described with reference to any one or more of the accompanying examples.
142. A TiO2-containing coated substrate substantially prepared according to the method as claimed in any one of claims 108 - 119.
143. A TiO2-containing coated substrate prepared substantially as herein described with reference 5 to any one or more of the accompanying examples.
144. A hardened TiO2-coated substrate substantially prepared according to the method as claimed in claim 135.
10 145. A hardened TiO2-coated substrate prepared substantially as herein described with reference to any one or more of the accompanying examples.
146. A hardened TiO2-coated substrate substantially prepared according to the method as claimed in any one of claims 122 - 130.
15
147. A hardened TiO2-coated substrate prepared substantially as herein described with reference to any one or more of the accompanying examples
148. A method of preparing a TiO2-based photocatalyst including or comprising the following 20 steps:
1) preparation of a solution containing colloidal particles which contain titanium ions wherein the particles are stabilised by oxalic acid, or stabilised by reaction with oxalic acid,
2) further processing of the solution to obtain the photocatalyst.
25 149. A method of preparing a Ti02-based photocatalyst as claimed in claim 148 wherein the Ti02- based photocatalyst is a Ti02 particulate material, and the further processing includes a gelling and a curing step.
150. A method of preparing a Ti02-based photocatalyst as claimed in claim 149 wherein the Ti02- 30 based photocatalyst is a Ti02 coating or film on a substrate, and the further processing includes preparation of a coating solution and application of the coating solution to the substrate, and a gelling and a curing step.
151. A method of preparing a Ti02-based photocatalyst as claimed in claim 150 wherein the Ti02 35 phase in the particulate material, coating or film, at least initially, includes, is predominantly or is substantially anatase and/or Ti02-B.
152. A method of preparing a Ti02-based photocatalyst as claimed in claim 151 wherein Preferably the Ti02-based photocatalyst acts as a photocatalyst upon irradation of or exposure to UV light.
153. A method of preparing a Ti02-based photocatalyst as claimed in claim 152 wherein the Ti02- 5 based photocatalyst is metal or metal-oxide doped.
154. A method of preparing a Ti02-based photocatalyst as claimed in claim 153 wherein the metal is selected from Pt, Pd, Cu or Ag.
10 155. A method of preparing a Ti02-based photocatalyst as claimed in claim 154 wherein Ti02-based photocatalyst can be used to photocatalytically degrade organic compounds and wherein the degradation occurs via application of or exposure to UV radiation.
156. A method of preparing a Ti02-based photocatalyst as claimed in claim 155 wherein the Ti02- 15 based photocatalyst can act as a hydrophilic surface when coated on a substrate.
157. A TiO2-based photocatalyst prepared substantially according to the method as claimed in any one of claims 148 to 156.
20 158. A TiO2-based photocatalyst prepared substantially as herein described with reference to any one or more of the examples.
159. A method of preparing B phase TiO2 including or comprising the following steps:
1) preparation of a solution containing colloidal particles which contain titanium ions wherein the 25 particles are stabilised by oxalic acid, or stabilised by reaction with oxalic acid,
2) further processing of the solution to obtain Ti02 predominantly or substantially in the Ti02-B phase,
3) heating of the Ti02 to substantially between 200-300°C.
30 160. A method of preparing B phase Ti02 as claimed in claim 159 wherein the further processing step 2) includes removal of the solvent and/or a gelling step and/or a curing step.
161. A method of preparing B phase Ti02 as claimed in claim 160 wherein step 1) is according to the method described previously.
35
162. A method of preparing B phase Ti02 as claimed in claim 161 there is a further step 4) of heating beyond 450°C provide Ti02 in the rutile phase.
163. B phase TiO2, prepared substantially according to the method of claims 159 to 162.
164. B phase TiO2, prepared substantially as herein described with reference to any one or more of the examples.
PCT/NZ2001/000144 2000-07-17 2001-07-17 Titanium-containing materials WO2002006159A1 (en)

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