TW201902353A - Method of producing nano ceria-titania binary oxide sol and its application in antibacteria - Google Patents

Abstract

This invention declares the method to produce ceria-titania binary oxide sol. The suspended complex nanosized particles of anatase structure titania in aqueous solution were synthesized by a sol-gel method using titanium tetrachloride as the precursors, and nanosized ceria sol were synthesized. Titanium tetrachloride is dissolved in aqueous solution of hydrogen chloride at low temperature. Ammonia solution is then added to form titanium tetrahydroxide. Hydrogen peroxide is then added. The mixture is then heated between 60-100 DEG C for hours to form titania sol. The ceria sol is added during heated procedure. The TiO2 particles are nano sized. That ceria particle size is less than 100nm. The TiO2 particle is in anatase structure. The sol is excellent in dispersibility and is stable at pH= 7~9 without causing agglomeration and precipitation. The transparent adherent CeO2-TiO2 film on substrates is obtained through spray-coating or dip-coating. It exhibits super-hydrophylic property. It has very high photoactivity under illumination by ultraviolet visible light, and sunlight. It has self-cleaning and dirt-removing capabilities and anti-bacterial. The distinguishing feature is the antibacterial activity of ceria-titania film could achieve higher than 99.99%, while titania film is inactive.

Description

 Preparation method of nanometer cerium oxide-titanium dioxide composite sol and its application in antibacterial efficacy  

The invention discloses a method for producing a nano-cerium oxide-titanium dioxide composite sol, which can be used as a raw material for coating a carrier, and the invention discloses its application in decontamination, self-cleaning and antibacterial treatment. The invention discloses that titanium tetrachloride is used as a raw material, titanium tetrachloride is first added to an aqueous hydrochloric acid solution in an ice bath (0-5 ° C), and then an aqueous solution of ammonia water is added to prepare titanium hydroxide, after repeated centrifugation and water washing. , completely remove the chloride ion, and then add hydrogen peroxide, the solution is heated at 60 to 100 ° C for a period of time, then add cerium oxide sol, wherein the weight ratio of titanium tetrachloride, hydrogen peroxide and cerium oxide to water is 0.01% -3%: 0.04%-14.1%: 0.0003%-0.01%: 99.9497%-82.89%, after the complete hydrolysis of the titanium hydroxide colloid, a stable suspension transparent nano-cerium oxide-titanium dioxide composite sol can be formed. Nano-sized solid particles are suspended in water, as shown in the analytical chart of the scanning electron microscope (Fig. 1). Titanium dioxide is a diamond-shaped particle with a long axis of 10-20 nm, a short axis of 2-4 nm, and dioxide dioxide. The crucible is a square particle with a particle size of less than 100 nm. Further, the aqueous solution is neutral, and it can be immersed on the carrier. The transparent nano-cerium oxide-titanium dioxide film can be obtained by sputtering or immersion plating on the carrier, and the nano-cerium dioxide-titanium dioxide film has super-support on the carrier. It is hydrophilic and has strong decontamination and self-cleaning effects, as well as antibacterial effects. Irradiated by fluorescent lamps, ultraviolet lamps or sunlight, it has high activity and can be used as a photocatalyst for decontamination, self-cleaning and antibacterial, and has strong antibacterial function under both illumination and non-lighting. The nano-cerium dioxide-titanium dioxide film is characterized in that it can achieve an antibacterial effect of more than 99.99% under visible light irradiation, and is different from the pure titanium dioxide film in visible light irradiation without obvious antibacterial effect.

A photocatalyst is a substance that promotes a chemical reaction by irradiation of light. The materials currently available as photocatalysts include oxides such as titanium dioxide (TiO ₂ ) and sulfides such as CdS. Among them, titanium dioxide is most commonly used as a photocatalyst because of its strong redox ability, high chemical stability and non-toxic properties. substance. Photocatalyst is good at treating extremely low concentrations of harmful chemicals in the air and does not release harmful substances by itself. Therefore, it is an excellent catalyst for environmental purification. Photocatalysts can produce functions such as deodorization, sterilization, antibacterial, antifouling and removal of harmful substances.

The crystal structure of titanium dioxide has three types of a tetragonal high-temperature rutile type, a low-temperature anatase type, and an orthorhombic brookite type. Among them, only anatase structure has the effect of photocatalyst. The photolysis mechanism of the photocatalytic treatment process is to excite the photocatalyst by ultraviolet light or sunlight to generate electrons and holes in the catalyst, thereby oxidizing the substances adsorbed on the surface, thereby cracking the substances adsorbed on the surface into small molecules. Taking titanium dioxide as an example, the titanium dioxide reaction starts from a wavelength of 400 nm (because the energy difference of titanium dioxide is about 3.1 eV, and the wavelength of light at 400 nm provides about 3.1 eV), and the titanium dioxide absorbs light energy to generate electrons (e- And the hole (h+), which has a relatively strong oxidizing power, can directly oxidize the pollutant molecules adsorbed on the surface of the material to decompose it, or oxidize water molecules adsorbed on the surface of the substance to hydroxyl radicals. (‧OH). The contaminants of the original macromolecules cleave the macromolecules into small molecules through photocatalytic photoreaction to achieve the purpose of contaminant removal.

Photocatalysts are widely studied and applied in environmental protection, energy, sterilization, and self-cleaning. Since 1972, Fujishma and Honda published in Nature for the first time in the journal Nature that TiO ₂ will decompose water to produce H ₂ and O ₂ after illuminating. More and more people are investing in research on the photocatalytic properties of TiO ₂ and are committed to various possibilities. Modification method to improve the effect of TiO ₂ photocatalyst.

The photocatalytic mechanism of surface metal modified titanium dioxide is reported by John T. Yates et al. in Chemical Review 1995, Volume 95, pp. 735-758. K. Rajeshwar et al., Pure Applied Chemistry, Vol. 73, No. 12, pp. 1849-1860, 2001, found that silver addition can increase the efficiency of reduction of Cr(VI) to Cr(III) by titanium dioxide. P. Falaras et al., Applied Catalysis B: Environmental 42 (2003) pp. 187-201, utilizes a silver-added titanium dioxide film to photocatalytically decompose methyl orange. Pierre Pichat et al., Photochem. Photobiol. Sci., 2004, 3, pp. 142-144, also disclose that silver addition enhances the rate of removal of 2-chlorophenol from titanium dioxide; however, previous literatures were in powder form, large particles of titanium dioxide. And all use ultraviolet light as a light source.

The invention uses a titanium tetrachloride as a raw material to study a method for preparing a transparent nano titanium dioxide photocatalyst stable suspension agent, wherein the titanium dioxide is anatase crystal, and the material preparation method of the invention is that the titanium tetrachloride aqueous solution is first added with ammonia water to become hydrogen hydroxide. Titanium, hydrogen peroxide is added, and then boiled at 60-100 degrees Celsius for several times, and a cerium oxide suspension is added to obtain a transparent nano-cerium dioxide-titanium dioxide crystal photocatalyst suspension. The product was analyzed by a transmission electron microscope and an X-ray diffractometer, and the nanoparticle of the ceria-titanium dioxide obtained by the present invention was visualized by electron microscopy analysis as shown in Fig. 1. The crystallization analysis is shown in the X-ray diffraction analysis chart (Fig. 2). It can be seen from Fig. 2 that the cerium oxide particles are attached to the surface of the TiO 2 crystal, and the addition of cerium oxide does not affect the crystallization of the titanium dioxide, so that the titanium dioxide maintains the crystal of the anatase and the cerium oxide particles themselves Less than 4 nanometers (less than the detection limit of the instrument), the crystal of cerium oxide cannot be seen in Figure 2.

The ceria-titanium dioxide composite sol material is plated on the support by an immersion coating method to obtain a transparent and strong ceria-titanium dioxide film. Irradiation with ultraviolet light or fluorescent lamps shows strong photocatalytic activity. Moreover, the cerium oxide-titanium dioxide film can achieve an antibacterial effect of more than 99.99% under visible light irradiation, which is different from the pure titanium dioxide film under the irradiation of a fluorescent lamp, and has no obvious antibacterial effect.

Generally, when titanium dioxide is prepared at low temperature, most of the non-crystalline particles are formed, and it must be calcined at about 300 ° C to form anatase crystals. This type of crystal has a photocatalytic effect, but some carriers, such as general glass, Leather, cloth, etc. cannot withstand such high temperatures, and the present invention discloses that anatase nanocrystalline crystal particles are formed at the time of preparation, and when it is coated on a carrier, it is not required to be calcined at a high temperature. Titanium dioxide film can be used as a photocatalyst. However, the generally coated titanium dioxide aqueous solution is made of titanium alkoxide as a raw material, which is expensive and complicated in the production process. The invention uses the cheaper titanium tetrachloride as a raw material to prepare an aqueous solution of cerium oxide-titanium dioxide at a low temperature, wherein the titanium dioxide crystallizes into anatase.

The photocatalytic reaction of the ceria-titanium dioxide catalyst by ultraviolet light can be used to decompose organic substances in wastewater or drinking water. The photochemical reaction is a heterogeneous photocatalytic reaction in which titanium dioxide having a semiconducting property is exchanged with cerium oxide to excite electrons from a covalent band to a conductive band under appropriate wavelength radiation to generate holes and electrons. Yes, holes and electrons react with water and oxygen to form hydroxyl radicals and peroxidic free radicals, which can react with organic matter to form new substances.

 Photocatalytic reaction principle  

The electrons in the outer layer of the semiconductor material can be divided into two electron energy bands, a Valence band and a conduction band, and the energy difference between the two bands is called a band gap. . While electrons are located in different energy bands, their ability to move is different. If the electrons are in the covalent band, they cannot move. The electrons in the conduction band can move freely in the crystal lattice. Reaction mechanism for heterogeneous photocatalytic catalysts. To carry out the photocatalytic reaction, the catalyst must be activated first, that is, a light source with a larger energy than the band gap is applied, and the electronic transition of the covalent band is excited to the conduction band to generate electrons and holes, and the electrons of the conduction band can be moved to the touch. The surface of the medium interacts with an electron acceptor (such as O ₂ ) adsorbed on the surface of the catalyst, allowing the oxygen molecules to carry away the electrons of the conduction band to form a radical species; likewise, the holes generated by the covalent band can be It interacts with an electron supply adsorbed on the surface of the catalyst (such as OH groups on the surface, multi-electron organic matter), and then further oxidizes the organic matter.

Titanium dioxide can be made into powder directly into the wastewater, or it can be applied to the surface of the substrate. The ultraviolet light can accelerate the decomposition of organic substances in water and air, but it will face the complete surface area of how to recover powder and catalyst. Received problems such as exposure to ultraviolet light. In order to improve these problems, the ceria-titanium dioxide is coated into a transparent film, and it is desired to increase the exposed area of the ceria titanium dioxide to increase the photocatalytic effect. This not only solves the above problems, but also increases the use of the cerium oxide-titanium dioxide photocatalyst.

At present, the antibacterial effect of titanium dioxide itself does not have a good antibacterial effect under the condition of visible light irradiation, so how to improve the antibacterial effect of the material is how to compound with other materials. Therefore, the invented ceria-titanium dioxide composite material can break through the problem of no antibacterial effect of titanium dioxide under visible light irradiation, and achieve an antibacterial function of 99.99% or more under fluorescent light or sunlight. The nano-sized cerium oxide particles are adsorbed on the surface of the titanium dioxide crystal, so that the electron tunnel can effectively extend the time of the transfer and recombination, which not only enhances the photocatalytic activity, but also successfully shifts the wavelength of the photocatalytic activity from the ultraviolet light band to the visible light wavelength band. The cerium oxide-titanium dioxide film can have a good antibacterial effect under visible light irradiation.

In addition, in order to produce a titanium dioxide film, several major preparation methods have been developed in recent years. A substrate having a large surface area is usually formed by chemical vapor deposition. The principle uses a chemical reaction to form a solid species in a reaction zone, and further deposits it on the surface of the carrier. The force is strong, there must be high temperature equipment, and the process is complicated.

The invention uses the cheaper titanium tetrachloride as a raw material to prepare an aqueous solution of anatase crystal titanium dioxide-cerium oxide at a low temperature. The nanocrystalline cerium oxide-titanium dioxide film was prepared by using a nanocrystalline crystal particle suspension coating method to prepare a transparent and stable suspended nanocrystalline crystal particle film. At the time of preparation, anatase nano titanium dioxide crystal particles and nano cerium oxide particles are formed, and after being coated on the carrier, it is not required to be calcined at a high temperature. The suspension solution is stable, and the nanoparticles do not aggregate and precipitate in a short time. This solution is neutral and therefore does not corrode the carrier.

The main innovative feature of the invention is the improvement of the antibacterial effect under visible light irradiation. The photocatalytic property of the ceria-titanium dioxide composite material under visible light is utilized, and the special reaction mechanism is used to achieve the antibacterial effect under visible light. The main point of the present invention is to disclose a sol (sol) for producing nano-scale cerium oxide-titanium dioxide, which has high photocatalytic effect and antibacterial effect by irradiation with a fluorescent lamp or ultraviolet light.

The invention adopts a nanocrystal particle suspension coating method to prepare a ceria-titanium dioxide film, and produces a transparent, stable suspension and photocatalytic activity of ceria-titanium dioxide nanocrystal crystal particles. The invention uses an inexpensive titanium tetrachloride and cerium oxide suspension as raw materials to prepare an aqueous solution of nano-sized cerium oxide-titanium dioxide particles, which is used as a coating material and has a photocatalytic effect after coating. The nano-sized titanium dioxide has an anatase crystal form, and the process is an innovative low-temperature process (temperature range 60-100 ° C), so it is not necessary to be calcined at a high temperature (temperature above 400 ° C). The suspension solution is very stable, and the nanoparticles do not aggregate and precipitate after more than 3 years. This solution is neutral and does not corrode the carrier.

First, titanium tetrachloride was slowly added to an aqueous hydrochloric acid solution at 0-15 ° C, and then 30% aqueous ammonia was added to become a titanium hydroxide colloidal solution. The colloidal solution was centrifuged and washed several times until there was no chloride ion (the titration of silver nitrate until no white silver chloride precipitated). The titanium hydroxide colloidal solution is further added with hydrogen peroxide, and then connected to the condenser tube at a temperature of 60 to 100 degrees Celsius in a three-necked flask. After boiling for a while, the cerium oxide suspension is added to obtain nano cerium oxide. Titanium dioxide photocatalyst suspension. The transparent ceria-titanium dioxide solution can be coated on glass or any carrier such as ceramics or plastic sheets. It can be applied to ultraviolet light or fluorescent lamps as a light source, which will produce relatively high catalytic activity, with decontamination, self-cleaning and Antibacterial effect and super hydrophilic. Moreover, the cerium oxide-titanium dioxide composite material can achieve an antibacterial effect of more than 99.99% under visible light irradiation, which is different from the pure titanium dioxide film under the irradiation of fluorescent lamps, and has no obvious antibacterial effect.

 Embodiment 1:  

A method for preparing a ceria-titania sol catalyst, the steps of which comprise:

a. Titanium tetrachloride is added to a hydrochloric acid aqueous solution at 0 to 5 ° C to form a solution, and then a NH ₄ OH solution is added to form a titanium hydroxide colloid, and the pH thereof is in the range of 7 to 12;

b. adding hydrogen peroxide to form an aqueous solution, the weight ratio of TiCl ₄ /H ₂ O ₂ is between 1/2 and 1/10, the amount of TiCl _{4 is} 0.01%-3%, and the amount of hydrogen peroxide is 0.04% -14.1%. .

c. This solution is heated in the range of 60 to 100 ° C for 1-10 hours, and a ceria suspension is added, which has a CeO ₂ addition amount of 0.0003% to 0.01%.

d. Continue heating until the colloid completely disappears, that is, a ceria-titanium dioxide composite sol is formed, and dispersed in a nanometer scale, and stably suspended in water.

 铈铈铈Example 1  

In an ice bath at 0 ° C, titanium tetrachloride was slowly dropped into a 5 molar concentration (5 M) aqueous hydrochloric acid solution, and then the solution was slowly added with 30% aqueous ammonia, and stirring was continued until the pH of the solution was 7, after several centrifugation, water washing until the concentration of chlorine is less than 5000ppm, then add it to distilled water, and add hydrogen peroxide, the solution is in a three-necked conical flask, connected to the condenser at 90 ° C 1 Hours, adding CeO ₂ solution, the weight ratio of TiCl ₄ /H ₂ O ₂ /H ₂ O/CeO ₂ is 1/2/96.95/0.05 (weight ratio), and then boiled for 2 hours to obtain nano-grade Ceria-titanium dioxide composite sol.

 Example 2  

Same as in Example 1, except that the weight ratio of the added materials was changed to 2/4.52/91.48/2 by TiCl ₄ /H ₂ O ₂ /H ₂ O/CeO ₂ , respectively.

 Comparative example 1  

Titanium dioxide is commercially available from Evonik-Degussa, Inc., model number P-25 to water in a weight ratio of 1/100.

 Embodiment 2  

Method for making transparent nano-cerium oxide-titanium dioxide substrate:

 First, cleaning the substrate  

The surface of the unwashed substrate may have oily substances or other impurities, which may cause uneven coating and peeling during calcination. The substrate is cleaned so that the ceria-titanium dioxide nanoparticles can adhere more firmly. On the substrate. The procedure for cleaning the substrate is as follows:

1. The substrate is placed in a neutral detergent and ultrasonically shaken for one hour.

2. Clean the residual detergent on the surface of the substrate with deionized water and wash it with ultrasonic wave for one hour.

3. The substrate was placed in a sodium hydroxide solution and ultrasonically shaken for one hour.

4. Wash the sodium hydroxide solution on the surface of the substrate with deionized water and wash it with ultrasonic wave for one hour.

5. Place the substrate in an oven and dry it for storage.

 Second, the coating method  

An immersion coating method or a spray coating method can be employed. The steps of the immersion coating are as follows: 1. Place the coating liquid on the lifting machine table, 2. Fix the glass substrate on the lifting machine, 3. Dip the substrate into the coating liquid, and the rate of decline is 5. -10cm/min, 4. Start to lift the film, the rate of rise is 5-10cm / min, 5. After the film is finished, irradiate under ultraviolet light for 30 minutes, 6. Place the treated substrate in the oven In the case of drying at 60-160 ° C, the nano-cerium dioxide-titanium dioxide primary coating operation is completed. 7. When the multilayer coating is produced, the above steps must be repeated.

 Example  

The present invention utilizes the standard inspection specification established by ISO 27447:2009 as a standard to test the antibacterial effect. The present invention utilizes the sol immersion plating of the embodiment 1-2 on the glass to carry out the illuminating antibacterial reaction. This antibacterial test method was tested for antimicrobial efficacy using Escherichia coli (OP50). The original bacterial solution concentration is 2.68×10 ⁶ CFU/ml, and the antibacterial result is shown in Fig. 3. The pure titanium dioxide (Fig. 3-1) is compared with the ceria-titanium dioxide (Fig. 3-2 and Fig. 3-3). The antibacterial effect of the immersion cerium oxide-titanium dioxide substrate (Fig. 3-3) can reach 99.99% or more.

In addition, the present invention also has an antibacterial test for the MRSA which is difficult to be treated in a hospital environment, and is tested according to the test specification of ISO 27447:2009, and the original bacterial liquid concentration is 2.32×10 ⁶ CFU/ml, and the antibacterial result is obtained. As shown in Fig. 4, the sample of pure titanium dioxide (Fig. 4-1) also showed no obvious antibacterial effect, and the antibacterial effect of the sample of the ceria-titanium dioxide material substrate (Figs. 4-2 and 4-3) was also Up to 99.99% or more.

The ceria-titanium dioxide particle material prepared by the invention and the transparent ceria-titanium dioxide glass substrate prepared by using the material thereof have strong photocatalytic activity after being irradiated by ultraviolet light, and have decontamination, self-cleaning and antibacterial. It has super hydrophilicity. Moreover, the cerium oxide-titanium dioxide catalyst can achieve an antibacterial effect of more than 99.99% under visible light irradiation, which is different from the pure titanium dioxide film under the illumination of a fluorescent lamp, and has no obvious antibacterial effect.

Claims (7)

 A method for preparing a ceria-titanium dioxide composite sol, the method comprising the steps of: adding titanium chloride solution at 0 to 5 ° C to form a solution, and then adding an aqueous ammonia solution to form a titanium hydroxide colloid, the pH thereof The value is in the range of 6 to 12; hydrogen peroxide is added to form an aqueous solution, and the solution is further heated in the range of 60 to 100 ° C, and then the cerium oxide suspension is added, and heating is continued until the colloid is completely hydrolyzed to form a stable state. Transparent ceria-titanium dioxide sol, wherein the weight ratio of titanium tetrachloride, hydrogen peroxide and ceria to water ranges from 0.01% to 3%: 0.04% to 14.1%: 0.0003% to 0.01%: 99.9497%-82.89% The nano-sized solid particles are suspended in water, and the pH of the aqueous solution is 6.5-10.    The method for preparing a ceria-titanium dioxide composite sol according to the first aspect of the patent application, wherein the pH value of the aqueous solution of the titanium hydroxide colloid is in the range of 6 to 12, the titanium dioxide is a nano particle, and the ceria is granular. 100nm.    A method for preparing a ceria-titanium dioxide composite sol according to the first aspect of the patent application, wherein the amount of titanium dioxide added is 0.01% to 3%, and the amount of hydrogen peroxide added is 0.04% to 14.1%.    A method of preparing a ceria-titanium dioxide composite sol according to the first aspect of the patent application, wherein the heating temperature is between 80 and 99 °C.    An antibacterial nanocomposite sol coating liquid prepared by the method of preparing a nano-cerium oxide-titanium dioxide composite sol according to the first item of the patent application.    A visible light antibacterial composite sol functional component is a cerium oxide-titanium dioxide composite sol obtained by a method for preparing a nano cerium oxide-titanium dioxide composite sol according to the first claim of the patent application.    For example, the method for utilizing the titanium dioxide composite sol of the sixth application patent is to use ultraviolet light, fluorescent lamps or sunlight as a method for decomposing organic substances, so that the substrate has self-cleaning and decontaminating effects, and is exposed to visible light. The substrate has an antibacterial effect.