DE102006014069A1 - Preparing a noble metal-containing inorganic oxide-brine, useful e.g. in the preparation of photovoltaic elements, comprises preparing the brine, and reacting a noble metal-precursor component with a water miscible organic solvent - Google Patents

Abstract

Preparation of noble metal-containing inorganic oxide-brine (I) comprises preparation of the brine by reacting an inorganic oxide forming precursor component, silicon alkoxide or its mixture and/or hydrolyzable metal component or its mixtures; and reaction of a noble metal-precursor component, preferably in the presence of a colloid stabilizer, in a solvent, water, at least with a water miscible organic solvent in a closed pressure container at greater than 100[deg]C. Preparation of noble metal-containing inorganic oxide-brine (I) comprises preparation of the brine by reacting an inorganic oxide forming precursor component, silicon alkoxide or its mixture and/or hydrolyzable metal component or its mixtures; and reaction of a noble metal-precursor component, preferably in the presence of a colloidal stabilizer, in a solvent, water, at least with a water miscible organic solvent in a closed pressure container at greater than 100[deg]C, where the reaction comprises the hydrolysis of the inorganic oxide forming precursor component and simultaneous complete reduction of the noble metal precursor component, by alcohol, to elementary noble metal. An independent claim is included for a noble metal-containing inorganic oxide-brine comprising a noble metal particle on the surface of oxide particle, existing as silicon oxide and/or metal oxide containing adsorbent.

Description

It is known that one material surfaces, especially textile and polymeric materials, functionalized by a surface treatment can to increase the utility value properties and the materials effectively from damaging chemical, mechanical, thermal, electromagnetic and biological Einflüsssen to protect. Through an effective surface modification can for the mentioned, new, attractive applications are opened up. Economical and ecological safety, in addition to improving the quality parameters, crucial Application criteria.

For functionalization of material surfaces wins the sol-gel technique (cf C. J.Brinker, G.W.Scherer, Sol-Gel-Science, Academic Press 1990), because it allows for economical and good quality inorganic processes Oxide layers, so-called ceramic coatings, at low temperatures on organic material surfaces deposit.

Schema 1 Sol-Gel-Prozeß (z.B. zur Bildung von SiO₂-Schichten)

Scheme 1 sol-gel process (eg to form SiO ₂ layers)

in this connection represents the inorganic oxide sol (II), the actual coating solution (similar to a Lack), by solvent evaporation a solvent-containing Gel layer (III) forms, which in different drying stages through Solvent removal and cross-linking into the pure oxide film.

• (A) Antimikrobiell wirkende Substanzen werden in der Sol-Gel-Beschichtung immobilisiert und kontrolliert freigesetzt ( DE 4329279.8 (v. 31.08.1993). Hierbei hat in jüngster Zeit die Sol-Gel-Immobilisierung von kolloidalem Silber aufgrund seiner geringen Toxizität und excellenten Langzeitwirkung ein besonderes Interesse erlangt ( JP 08067835 , JP 09025437 , DE 10225324 , DE 10315720 , DE 10337399 ). Das Problem derartiger Schichten besteht in einer geeigneten Einbringung kolloidaler Silberpartikel in die Schicht und alle bisherigen Verfahrensweisen haben verschiedene Nachteile: (i) Der Zusatz kolloidalen Silbers zum Beschichtungssol erfordert neben hohen Materialkosten einen hohen Dispergier- und Stabilisierungsaufwand; (ii) Der Einsatz von Silbersalzen und Silberkomplexen führt (neben lichtinduzierten Verfärbungen) zu einer unerwünscht schnellen Ausdiffusion von Silberionen aus der Schicht; (iii) Die in situ-Reduktion zugesetzter Silbersalze im Sol ist hinsichtlich Teilchengröße und Dispersionsstabilität schwer steuerbar; (iv) Die thermische Reduktion der Silbersalze in der Schicht ist für viele organische Substrate (Holz, Textilien, Polymere) aufgrund thermischer Zersetzungen nicht möglich.
• (B) Photokatalytisch wirkende TiO₂-Beschichtungen auf Sol-Gel-Basis zerstören bei UV-Bestrahlung oxidativ anhaftende Keime und andere organische Ablagerungen („selbstreinigende" Oberflächen). Nachteilig hierbei ist, dass nur die Anatas-Modifikation eine hohe Photoaktivität zeigt, was eine nachtägliche Temperung der Schichten z.B. auf 500°C ( JP 6090489 ), 300-1000°C ( DE 19962055 ) oder eine nachträgliche hydrothermale Behandlung der Schichten von 60-200°C (WO 2004/007070) erforderlich macht. Während Temperungen über 300°C für alle organischen Substrate ausscheiden, beeinträchtigt die nachträgliche hydrothermale Behandlung der Schichten die Schichtqualität und ist sehr zeit- und kostenaufwendig und daher wirtschaftlich nicht praktikabel. Genereller Nachteil von TiO₂-Schichten ist zudem, dass zur Erzielung der Keimfreiheit die Anwesenheit von Licht erforderlich ist. Darum ist man bestrebt, in derartigen Schichten antimikrobiell wirkende Substanzen zusätzlich zu immobilisieren, um eine biozide Wirkung auch bei Abwesenheit von Licht zu garantieren.

An advantage of the sol-gel technique is the ability to adapt the sols to their intended use by chemically modifying and immobilizing various functional substances. In particular, the equipment of material surfaces with germicidal antimicrobial coatings is currently of increasing interest and has hitherto been realized in two fundamentally different ways:

• (A) Antimicrobial substances are immobilized in the sol-gel coating and released in a controlled manner ( DE 4329279.8 (v. 31.08.1993). Recently, the sol-gel immobilization of colloidal silver has acquired a special interest due to its low toxicity and excellent long-term effect ( JP 08067835 . JP 09025437 . DE 10225324 . DE 10315720 . DE 10337399 ). The problem with such layers is the proper incorporation of colloidal silver particles into the layer, and all previous processes have several disadvantages: (i) The addition of colloidal silver to the coating sol, in addition to high material costs, requires a high dispersion and stabilization effort; (ii) The use of silver salts and silver complexes leads (in addition to light-induced discolorations) to an undesirably rapid outdiffusion of silver ions from the layer; (iii) The in situ reduction of added silver salts in the sol is difficult to control in terms of particle size and dispersion stability; (iv) The thermal reduction of silver salts in the layer is not possible for many organic substrates (wood, textiles, polymers) due to thermal decomposition.
• (B) Photocatalytically active TiO ₂ coatings on a sol-gel basis destroy oxidatively adhering nuclei and other organic deposits ("self-cleaning" surfaces) on UV irradiation, with the disadvantage that only the anatase modification shows high photoactivity a night-time heat treatment of the layers, for example to 500 ° C ( JP 6090489 ), 300-1000 ° C ( DE 19962055 ) or a subsequent hydrothermal treatment of the layers of 60-200 ° C (WO 2004/007070) is required. While anneals above 300 ° C for all organic substrates excreted, the subsequent hydrothermal treatment of the layers affects the quality of the layer and is very time and cost consuming and therefore not economically feasible. Another general disadvantage of TiO ₂ layers is that the presence of light is required to achieve sterility. Therefore, it is endeavored to additionally immobilize antimicrobial substances in such layers in order to guarantee a biocidal effect even in the absence of light.

The object of the present invention was thus a new coating system, in particular Sol-gel base, which enables the functionalization, in particular antibacterial equipment, a wide range of material surfaces in a simple and cost-effective manner and avoids the disadvantages of the prior art.

Surprisingly could solve the problem be used that are used for coating noble metal-containing inorganic oxide sols, by a solvothermal synthesis method according to claim 1 of Siliciummalkoxiden and / or hydrolyzable metal compounds and noble metal compounds in the presence of colloid stabilizers in aqueous-organic solvents in a closed pressure vessel at temperatures above 100 ° C received become. This one-step process involves hydrolytic formation the oxide brine, a reduction of the precious metal compounds by alcohol to noble metal colloids adsorbed on the surface of the oxide particles be, and the increase the degree of crystallinity the oxide (nano) particles simultaneously.

The resulting noble metal-containing inorganic oxide sols exhibit excellent colloid stability and form well-adhering coatings with excellent antimicrobial activity on any material surfaces and moreover, depending on the composition, further advantageous properties; For example, in TiO ₂ sols simultaneously high photoactivity.

object The present invention thus provides methods of preparation of noble metal-containing inorganic oxide sols according to claims 1-7 as well as those obtainable therewith Brine according to claims 8-12 and their use according to claims 13-20.

To prepare the noble metal-containing inorganic oxide sols can be used as oxide-forming precursor component is a silicon alkoxide having the general structure (R ¹ O) ₄ Si, (R ¹ O) ₃ SiR ^2, or (R ¹ O) ₂ SiR ² R ² wherein R ^{1 is} an alkyl radical having 1-4 C atoms and R ^{2 is} an alkyl or fluoroalkyl radical having 1-16 C atoms, where R ² further comprises additional alkoxy, epoxy, amino or alkylamino groups or other O, N or S-containing functional groups may contain as substituents, or a mixture of such silicon alkoxides are used.

When precursor (Precursor) for Metal oxides are preferably metal alkoxides derived from elements of the II.-V. Derive group of the periodic table, or mixtures thereof used. Some preferred examples of such elements are Ti, Al, Zr and Zn.

in principle can but also other hydrolyzable metal compounds of elements the II.-V. Group of the periodic table such. Halides or carboxylates, preferably acetates, are used as precursors.

It is possible, too, above-mentioned precursors in mixed form, e.g. Mixtures of silicon alkoxides and metal alkoxides or mixtures of different silicon alkoxides or mixtures of different metal alkoxides. There are Mixtures comprising at least one silicon alkoxide, preferably.

In a specific embodiment of the present invention, a mixture of a titanium alkoxide and at least one other alkoxide, preferably silicon alkoxide, is used. Preferably, such a mixture is used that the proportion of TiO ₂ in the resulting oxide matrix component of the noble metal-containing sol or of the dried gel is ≥ 50% by weight.

In a particularly preferred embodiment of the invention, the oxide component of the noble metal-containing oxide sol or gel comprises 60-80% by weight of TiO ₂ and 40-20% by weight of SiO ₂ , for example about 75% by weight of TiO ₂ and about 25 Wt .-% SiO ₂ .

to Preparation of the noble metal-containing inorganic oxide sols can as Noble metal precursor precious metal compounds, preferably salts or complexes of Au, Ag, Cu, Pt, Pd or Ru, preferably in concentrations of 0.1-20 wt .-%, based on the formed oxide in the sol or in the gel layer can be used.

The preparation process according to the invention is characterized in that it is a solvothermal synthesis which is carried out in an aqueous / organic medium in a closed pressure vessel, for example a stainless steel or glass autoclave, at a temperature of at least 100.degree. Preferably, the temperature is between 100 and 200 ° C, more preferably between 100 and 160 ° C. As UV / Vis and Raman spectroscopic studies show, the hydrolysis of the silicon or metal alkoxides occurs and reduction of the noble metal compounds usually already in a temperature range between 100 and 120 ° C. For the conversion of amorphous TiO ₂ sols into photoactive crystalline anatase particles, a temperature between 120 and 140 ° C. is generally sufficient.

The used pressures typically range from 2 to 10 bar.

For the solvothermal Reaction are called solvents water-miscible organic liquids, preferably ethanol, Methanol or acetone used for the hydrolysis of the silicon or metal alkoxides mixed with at least the equivalent amount of water be so that the proportion of water between 1-99 wt .-% may be. It is not necessary to reduce the precious metal compounds required alcohol to the reaction mixture, as by the hydrolysis of the silicon or metal alkoxides during the Reaction alcohol is formed. Thus, the reduction reaction runs also in a non-alcoholic solvent without addition of a additional Reducing off easily. To speed up the hydrolysis can catalytic amounts of acid or ammonia or alkali are added to the reaction mixture become.

The Precious metal compounds are solvothermal in the course of the invention Process reduced to colloidal precious metal particles and on the surface of the Adsorbed oxide particles. By the adsorption of the noble metal particles on the oxide surface becomes a high stability the colloidal solution reached. To ensure this (especially with highly concentrated sols), it is usually necessary, the reaction mixture before the solvothermal process colloid stabilizers add. Water- or alcohol-soluble polymers proved to be particularly suitable N- and / or O-containing Compounds such as polyethylene oxide derivatives, modified polysiloxanes, Polyvinyl alcohol, polyvinylpyrrolidone or cellulose ether or a A range of commercial sulfonate, phosphate or alkoxylate group-containing Surfactants or mixtures thereof in a proportion up to 10 wt .-%. The inventively usable Colloid stabilizer is not equivalent to a dispersant and does not include any commonly used as a dispersant in the art Compounds, in particular no inorganic phosphate compounds such as trisodium phosphate and pyrophosphate.

• – insbesondere silberhaltige Oxid-Sole, aber auch andere edelmetallhaltige Oxid-Sole, können zur effektiven antimikrobiellen Ausrüstung von Materialoberflächen, vorzugsweise von Holz, Textilien und Kunststoffen eingesetzt werden (vgl. Beispiel 1);
• – edelmetallhaltige SiO₂-Sole, die durch co-kondensierte Alkylsilane oder Fluoralkylsilane modifiziert wurden, können zur eis- und wasserabweisenden Ausrüstung von Materialoberflächen eingesetzt werden (vgl. Beispiel 2);
• – edelmetallhaltige TiO₂-Sole (mit Ag-, Pt-, Ru- oder Pd-Partikeln dotiert) können zur Herstellung photoaktiver Beschichtungen mit photokatalytischen und photoelektrischen Eigenschaften eingesetzt werden, die z.B. zur Ausrüstung von selbstreinigenden Materialoberflächen oder zur Herstellung photovoltaischer Elemente dienen (vgl. Beispiel 3);
• – edelmetallhaltige TiO₂-Sole können zur Herstellung photoaktiver Beschichtungen genutzt werden, z.B. zur Ausrüstung von Materialoberflächen mit schaltbarem Benetzungsverhalten, die zur Herstellung von wiederverwendbaren Drucksystemen von großem Interesse sind (vgl. Beispiel 4). Hierbei wirkt sich insbesondere der Einbau der Edelmetallkatalysatoren (im Vergleich zum undotierten TiO₂) vorteilhaft auf die Schalthöhe aus (vgl. Tabelle 3).

The stable noble metal-containing inorganic oxide sols formed by the solvothermal process can be used immediately after production for coating material surfaces. Depending on the composition, the sols are suitable for different applications:

• - In particular silver-containing oxide sols, but also other noble metal-containing oxide sols, can be used for effective antimicrobial finishing of material surfaces, preferably of wood, textiles and plastics (see Example 1);
• Noble metal-containing SiO ₂ sols modified by co-condensed alkylsilanes or fluoroalkylsilanes can be used for ice and water-repellent finishing of material surfaces (see Example 2);
• - noble metal-containing TiO ₂ sols (doped with Ag, Pt, Ru or Pd particles) can be used for the production of photoactive coatings with photocatalytic and photoelectric properties, for example, to equip self-cleaning material surfaces or for the production of photovoltaic elements (see Example 3);
• - Precious metal-containing TiO ₂ sols can be used for the production of photoactive coatings, for example for the equipment of material surfaces with switchable wetting behavior, which are for the production of reusable printing systems of great interest (see Example 4). In particular, the incorporation of the noble metal catalysts (in comparison to undoped TiO ₂ ) has an advantageous effect on the switching height (see Table 3).

• – das einstufige Verfahren zur Herstellung edelmetallhaltiger anorganischer Oxid-Sole aus einfachen Laborchemikalien (z.B. Tetraethoxysilan und Silbernitrat) ersetzt die bislang erforderlichen und arbeitsaufwändigen 2 bis 3 separaten Arbeitsschritte (Sol-Herstellung, Herstellung und Stabilisierung der Edelmetall-Kolloide, gegebenenfalls Überführung eines amorphen Metalloxids (z.B. amorphes TiO₂) in eine kristalline Modifikation (z.B. die photoaktive kristalline Anatas-Modifikation von TiO₂), vermeidet den Zusatz externer Reduktionsmittel oder Antioxidantien, und führt zu einer drastischen Kosten- und Zeiteinsparung sowie Verbesserungen der Schichtqualität;
• – die Herstellung der edelmetallhaltigen Sole ist in beliebigen Konzentrationen und Zusammensetzungen möglich und ergibt selbst in extremen Verdünnungen (wichtig z.B. zur Beschichtung von Textilien, Leder, Folien) und niedrigen Viskositäten eine homogene Verteilung der Edelmetall-Kolloide im Sol und in der Beschichtung;
• – durch die Adsorption der Edelmetallpartikel auf der Oxid-Oberfläche wird eine hohe Stabilität der kolloidalen Lösung erreicht; die Sole zeigen darum unabhängig von der Konzentration eine ausgezeichnete Kolloidstabilität und die daraus hergestellten funktionellen Schichten unterscheiden sich in der Struktur und Wirksamkeit gegenüber Schichten, die aus Oxid-Solen, denen separat Edelmetallkolloide zugemischt wurden, hergestellt wurden;
• – die edelmetallhaltigen anorganischen Oxid-Sole bilden auf beliebigen Materialoberflächen gut haftende Beschichtungen mit exzellenter antimikrobieller Aktivität (und bei Einsatz von TiO₂ gleichzeitig hoher Photoaktivität).

The many possible uses of the precious metal-containing sols prepared according to the invention, due to their multifunctionality, are a great advantage over the prior art. Further advantages are the following:

• - The one-step process for the preparation of noble metal-containing inorganic oxide brine from simple laboratory chemicals (eg tetraethoxysilane and silver nitrate) replaces the previously required and laborious 2 to 3 separate steps (sol production, production and stabilization of precious metal colloids, optionally transfer of an amorphous metal oxide ( eg amorphous TiO ₂ ) in a crystalline modification (eg the photoactive crystalline anatase modification of TiO ₂ ), avoids the addition of external reducing agents or antioxidants, and leads to drastic cost and time savings as well as improvements in film quality;
• The preparation of the noble metal-containing sols is possible in any desired concentrations and compositions and, even in extreme dilutions (important, for example, for coating textiles, leather, Foils) and low viscosities, a homogeneous distribution of noble metal colloids in the sol and in the coating;
• - By the adsorption of the noble metal particles on the oxide surface, a high stability of the colloidal solution is achieved; the sols therefore exhibit excellent colloidal stability regardless of concentration, and the functional layers made therefrom differ in structure and effectiveness from layers made from oxide sols to which noble metal colloids have been separately added;
• - The noble metal-containing inorganic oxide sols form on any material surfaces well-adherent coatings with excellent antimicrobial activity (and when using TiO ₂ at the same time high photoactivity).

The The following examples are for closer explanation of the present invention, but without being limited thereto.

EXAMPLE 1

Production of silver-containing antimicrobial oxide coatings

The compositions given in Table 1 were heated to 120 ° C. for 1 h in a stainless steel autoclave from Büchi. With the resulting homogeneous brown-black colloid solutions textile samples (20 × 20 cm ² , viscose fabric) were dip-coated and dried at 120 ° C for 1 h. After a 5X ECE standard wash at 40 ° C, the samples were tested for their antimicrobial activity against Bacillus subtilis. All coated samples showed complete inhibition of bacterial growth.

• ¹⁾ a = log KBE (unbeschichtete Blindprobe, 24h) – log KBE (A-F beschichtete Probe, 24 h) KBE = (Bakterien-)Kolonie bildende Einheiten
• ²⁾ TE2OS = Tetraethoxysilan Si(OEt)₄ (FLUKA)
• ³⁾ PVP = Polyvinylpyrrolidon (MERCK, Molgewicht 25000-30000)
• ⁴⁾ GLYEO = 3-Glycidyloxypropyl-triethoxysilan (FLUKA)
• ⁵⁾ MeTES = Methyltriethoxysilan (FLUKA)
• ⁶⁾ OTS = Octyltrimethoxysilan (FLUKA)
• ⁷⁾ BYK333 = Polyether-modifiziertes Dimethylpolysiloxan Copolymer (BYK Chemie GmbH Wesel)
• ⁸⁾ Klucel E = niedrigviskose Hydroxypropylcellulose (Aqualon GmbH)

Table 1 shows the composition of the reaction mixtures before autoclaving and the specific antimicrobial activity a of the resulting coatings after autoclaving and coating on viscose fabric and 5 times ECE standard wash at 40 ° C. Table 1

• ¹⁾ a = log CFU (uncoated blank, 24h) - log CFU (AF coated sample, 24 h) CFU = (bacterial) colony forming units
• ²⁾ TE2OS = tetraethoxysilane Si (OEt) ₄ (FLUKA)
• ³⁾ PVP = polyvinylpyrrolidone (MERCK, molecular weight 25000-30000)
• ⁴⁾ GLYEO = 3-glycidyloxypropyltriethoxysilane (FLUKA)
• ⁵⁾ MeTES = methyltriethoxysilane (FLUKA)
• ⁶⁾ OTS = octyltrimethoxysilane (FLUKA)
• ⁷⁾ BYK333 = polyether-modified dimethylpolysiloxane copolymer (BYK Chemie GmbH Wesel)
• ⁸⁾ Klucel E = low-viscosity hydroxypropylcellulose (Aqualon GmbH)

EXAMPLE 2

Preparation of a water-repellent antimicrobial coating

The coating solution D (Table 1) after autoclaving was dip coated (30 cm / min) on aluminum sheet (25 × 75 mm ² ). After annealing (1 h / 120 ° C) results in a yellow clear layer with strong water-repellent effect (contact angle to water 93 °).

EXAMPLE 3

Production of a photocatalytic noble metal-containing TiO ₂ coating

The in Table 2 compositions was in a stainless steel autoclave the company Büchi 1 h heated to 140 ° C. With the resulting homogeneous brown-black colloid solutions Glass samples were dip-coated and annealed at 120 ° C for 1 h. The photocatalytic effect was due to the light-induced destruction of a sprayed Octylsilane layer (and the associated decrease in the contact angle across from Water).

• 1) UV-Mitteldruckstrahler (50 W/cm), Abstand der Proben zum UV-Strahler: 20 cm,
• 2) Klucel E = niedrigviskose Hydroxypropylcellulose/Aqualon GmbH
• 3) HCPt = Hexachloroplatinsäure-Hydrat/FLUKA

Table 2 demonstrates the photocatalytic effect of TiO2 layers prepared from Ag, Pt, and Pd-containing sols by the oxidation of an octyltrimethoxysilane (OTS) layer by UV irradiation by H ₂ O edge angle measurement -Radiation. Table 2

• 1) UV medium-pressure lamp (50 W / cm), distance of the samples to the UV lamp: 20 cm,
• 2) Klucel E = low viscosity hydroxypropyl cellulose / Aqualon GmbH
• 3) HCPt = hexachloroplatinic acid hydrate / FLUKA

EXAMPLE 4

Production of a Switchable Precious Metal-Containing TiO ₂ Coating

• 1) UV-Mitteldruckstrahler (50 W/cm), Abstand der Proben zum UV-Strahler: 20 cm

The wetting behavior of the layers produced according to Table 2 by dip coating (30 cm / min) on glass slides of 25 × 75 mm ² against water can be greatly increased by irradiation with an MD-UV lamp (drop in the contact angle) and by annealing to 20,000 be regenerated again (see Table 3). The switching behavior can be repeated as desired. Table 3 Reversible change in the contact angle of noble metal-containing TiO ₂ coatings on glass

• 1) UV medium-pressure lamp (50 W / cm), distance of the samples to the UV lamp: 20 cm

Claims (20)

A process for the preparation of noble metal-containing inorganic oxide sols, characterized in that the formation of the sols by reacting an inorganic oxide-forming precursor component comprising a silicon alkoxide or a mixture of silicon alkoxides and / or a hydrolyzable metal compound or a mixture of hydrolyzable metal compounds, and a Precious metal precursor component, in particular in the presence of a colloidal stabilizer, in a solvent comprising water and at least one water-miscible organic solvent, in a closed pressure vessel at temperatures above 100 ° C, wherein the reaction, the hydrolysis of the inorganic oxide-forming precursor component and the simultaneous complete reduction of the noble metal precursor component by alcohol to elemental precious metal. A method according to claim 1, characterized in that as an inorganic oxide-forming precursor component silicon alkoxides of the general structure (R ¹ O) ₄ Si, R ¹ O) ₃ SiR ^2, or (R ¹ O) ₂ SiR ² R ² wherein R ^{1 is} an alkyl radical having 1-4 C atoms and R ^{2 is} an alkyl or fluoroalkyl radical having 1-16 C atoms, wherein R ² further comprises additional alkoxy, epoxy, amino or alkylamino groups or other O, N - or S-containing functional groups may contain as substituents used. Method according to claim 1 or 2, characterized as the inorganic oxide-forming precursor component a metal alkoxide or a mixture of metal alkoxides derived of elements of the II.-V. Group of the Periodic Table, is used. Method according to one of claims 1-3, characterized as the inorganic oxide-forming precursor component a mixture of silicon alkoxides and metal alkoxides, a mixture from different silicon alkoxides or a mixture of different Metal alkoxides is used. Method according to one of claims 1-4, characterized that as a noble metal precursor component Salts or complexes of Au, Ag, Cu, Pt, Pd or Ru in concentrations of 0.1-20 wt .-%, based on the oxide in the sol formed, used become. Method according to one of claims 1-5, characterized in that that the water content in the solvent between 1-99% by weight. Method according to one of claims 1-6, characterized that as colloid stabilizers water or alcohol-soluble polymeric N and / or O-containing compounds, e.g. Polyethylene oxide derivatives, modified Polysiloxanes, polyvinyl alcohol, polyvinylpyrrolidone or cellulose ethers, or sulfonate, phosphate or alkoxylate group-containing surfactants or mixtures thereof to a maximum of 10 wt .-%, based on the oxide in the formed sol, be used. Noble metal-containing inorganic oxide sol, the noble metal particle on the surface of oxide particles consisting of silica, a metal oxide or a mixture of silica and a metal oxide adsorbed contains obtained by the method according to any one of claims 1-7. Precious metal-containing inorganic oxide sol according to claim 8, characterized in that it comprises a colloid stabilizer. Precious metal-containing oxide sol according to claim 8 or 9, characterized in that it is a TiO ₂ -containing sol. Noble metal-containing oxide sol according to claim 10, characterized in that the proportion of TiO ₂ in the oxide component ≥ 50 wt .-% is. A noble metal-containing oxide sol according to claim 11, characterized in that the oxide component comprises 60-80 wt .-% TiO ₂ and 40-20 wt .-% SiO ₂ . Use of the sols according to any one of claims 8-12 for the coating and functionalization of material surfaces. Use of the sols according to any one of claims 8-12 for antimicrobial equipment of material surfaces, preferably of wood, textiles and plastics. Use of the sols according to any one of claims 8-12 for ice and water repellent equipment as well as for oil and dirt repellent equipment of material surfaces. Use of the sols according to any one of claims 8-12 to the equipment of material surfaces with switchable wetting behavior. Use of the sols according to any one of claims 8-12 to the equipment of material surfaces with photocatalytic and photoelectric properties. Use of the sols according to any one of claims 10-12 for the production of switchable printing plates. Use of the sols according to any one of claims 10-12 to the equipment of self-cleaning material surfaces. Use of the sols according to any one of claims 10-12 for the production of photovoltaic elements.