Method for producing nanoparticles from a noble metal and use of the nanoparticles thus produced

Abstract

The invention relates to a method for producing nanoparticles from a noble metal and to the use of the nanoparticles produced using the method. It is the object of the invention to provide possibilities for a simple and inexpensive production of nanoparticles from a noble metal in which influence can be directly made on the particle size of the nanoparticles thus produced. Nanoparticles of silver, gold and platinum can be produced with an adjustable particle size using the method in accordance with the invention. A chemical compound of the respective noble metal is dissolved in an aqueous solution or the noble metal is dissolved in an acid mixture. An aqueous solution containing at least one surfactant is added to the respective solution and a reductant is additionally added with silver and platinum. The parameters: concentration of the chemical compound or of the noble metal, the temperature, pH and the fraction of surfactant are influenced to influence the particle size. The noble metal particles precipitated from the respective solution can be centrifuged out.

1 . A method for producing nanoparticles from a noble metal, which is selected from silver, gold, and platinum, having an adjustable particle size, the method comprising:
 dissolving a chemical compound of the respective noble metal in an aqueous solution or dissolving the noble metal in an acid mixture;   adding an aqueous or alcoholic solution containing at least one surfactant to the respective solution and additionally adding a reductant with silver and platinum; wherein the particle size of the nanoparticles is influenced by influencing the parameters: concentration of the chemical compound or of the noble metal, temperature, pH, and the fraction of surfactant; and   centrifuging out the noble metal particles precipitated from the respective solution.   
     
     
         2 . The method in accordance with  claim 1 , wherein the particle size is reduced with a smaller concentration of the chemical compound used or of the noble metal, and/or at an elevated temperature and/or with an increased fraction of surfactant. 
     
     
         3 . The method in accordance with  claim 1 , wherein the particle size is reduced with an increased pH. 
     
     
         4 . The method in accordance with  claim 1 , wherein, for the production of nanoparticles of gold or platinum, the respective metal is dissolved in a mixture of hydrochloric acid and nitric acid. 
     
     
         5 . The method in accordance with  claim 1 , wherein, for the production of nanoparticles, the silver is dissolved in hot nitric acid, preferably at a temperature in the range from 100° C. to 150° C. 
     
     
         6 . The method in accordance with  claim 1 , wherein the at least one surfactant is selected from alkoxylates, alkylolamides, esters, amine oxides, alkyl polyglucosides, alkylphenols, arylalkyl phenols, water-soluble homopolymers, water-soluble statistical copolymers, water-soluble block copolymers, water soluble graft polymers, polyvinyl alcohols, copolymers of polyvinyl alcohols and polyvinyl acetates, polyvinylpyrrolidones, cellulose, starch, gelatins, gelatin derivatives, amino acid polymers, polylysine, polyasparagine acid, polyacrylates, polyethylene sulfonates, polystyrene sulfonates, polymethacrylates, condensation products of aromatic sulfonic acids with formaldehyde, napththalenesulfonates, lignosulfonates, copolymerizates of acrylic monomers, polyethyleneimines, polyvinylamines, polyallylamines, poly(2-vinylpyridines), block copolyethers, block copolyethers with polystyrene blocks, sodium dodecylbenzenesulfonate, and polydiallyl dimethyl ammonium chloride. 
     
     
         7 . The method in accordance with  claim 1 , wherein hydroxylamine is used for the production of nanoparticles from silver and hydrazine hydrate or sodium borohydride is used as a reductant for the production of nanoparticles from platinum. 
     
     
         8 . The method in accordance with  claim 1 , wherein the pH in the solution is set with added NaOH, added NH 3  and/or added piperidine. 
     
     
         9 . The method of  claim 1 , comprising using the nanoparticles for the production of electrically conductive and/or printable ink, and/or electrically conductive and optically reflective layers.