Double jet process for producing nanosilver dispersions

Abstract

This invention provides a double jet process to produce silver nanoparticles, the process comprising providing a double-jet system to form a reaction mixture in a reactor containing the reactor solution by adding a basic aqueous silver ammonia complex solution and a basic reducing solution to the reactor solution at the same controlled rate with a targeted pH profile for the reactor solution from acidic to basic determined by the addition rate and the initial pH of the reactor solution. Use of this process results in a dispersion comprised of silver nanoparticles that have a specific size and de-agglomeration level that is determined by the process conditions.

What is claimed is: 
     
         1 . A process for preparing silver nanoparticles, said process comprising the steps of:
 (a) preparing a basic aqueous silver ammonia complex solution comprising a water soluble silver salt and ammonia in deionized water;   (b) preparing a basic reducing solution comprising hydrazine monohydrate in deionized water;   (c) preparing an acidic reactor solution with a pH in the range of 3.0 to 5.0, said reactor solution comprising:
 (i) one or more dispersing agents, one of which is gum arabic hydrated in deionized water; and 
 (ii) nitric acid; 
   (d) maintaining the basic aqueous silver ammonia complex solution and the basic reducing solution at the same temperature T M , wherein T M  is in the range of 10° C. to 90° C.;   (e) providing a double-jet system to form a reaction mixture in a reactor containing the reactor solution by adding the basic aqueous silver ammonia complex solution and the basic reducing solution to the reactor solution at the same controlled rate with a targeted pH profile for the reactor solution from acidic to basic determined by the addition rate and the initial pH of the reactor solution; and   (f) maintaining the reaction mixture in the reactor at constant temperature in the range of 10° C. to 90° C. to produce the silver nanoparticles.   
     
     
         2 . The process of  claim 1  further comprising the steps of:
 (h) separating the silver nanoparticles from the reaction mixture; 
 (i) washing the silver nanoparticles with deionized water; and 
 (j) transferring the silver nanoparticles to a nonaqueous solution 
 
     
     
         3 . The process of  claim 1 , wherein said water soluble silver salt is silver nitrate. 
     
     
         4 . The process of  claim 1 , wherein said one or more additional dispersing agents are selected from the group consisting of benzotriazole, salts of polynaphthalene sulfonate formaldehyde condensate, poloxamer block copolymer, ethoxylated phenols, polyethylene glycol with molecular weight ranges from 200 to 8000, and mixtures thereof. 
     
     
         5 . The process of  claim 1 , wherein the molar ratio of ammonia to silver is greater than 2.