Method of manufacturing silver platelets

Abstract

The present invention provides an aqueous solution-based method for producing nano-sized silver platelets, which employs the controlled mixing of a silver ion solution, a reducing solution, and an acidic solution, under suitable conditions. Also provided are the silver platelets produced thereby, and compositions containing the silver platelets.

What is claimed is: 
     
         1 . A method for making silver nano-platelets with an aspect ratio of at least 2, comprising the essentially simultaneous addition of a silver ion solution and a reducing solution to an acidic solution, under conditions that permit the reduction of the silver ions to metallic silver, wherein
 (a) the silver ion solution comprises a plurality of silver ions;   (b) the reducing solution comprises one or more reducing agents;   (c) the acidic solution comprises one or more stabilizing agents; and   (d) at least part of the reduction takes place in the presence of palladium ions.   
     
     
         2 . The method of  claim 1 , wherein the reducing solution comprises ascorbic acid, isoascorbic acid, or a salt thereof. 
     
     
         3 . The method of  claim 1 , wherein at least a portion of the silver ion solution further comprises palladium ions. 
     
     
         4 . The method of  claim 1 , wherein the silver ion solution is divided into a preceding portion and a succeeding portion, and wherein the preceding portion of the silver ion solution comprises palladium ions. 
     
     
         5 . The method of  claim 1 , wherein the total amount of palladium, relative to the total amount of silver, is about 0.2% by weight. 
     
     
         6 . The method of  claim 1 , wherein the total amount of palladium, relative to the total amount of silver, is at least 0.05% by weight. 
     
     
         7 . The method of  claim 1 , wherein the acidic solution comprises gum arabic. 
     
     
         8 . A silver nano-platelet obtained in accordance with the method of  claim 1 . 
     
     
         9 . A silver nano-platelet obtained in accordance with the method of  claim 7 . 
     
     
         10 . A plurality of the silver nano-platelets obtained in accordance with the method of  claim 1 , wherein at least 90% of the silver platelets have a width within the range of W±20% W, where W is the mean width of the silver platelets. 
     
     
         11 . The plurality of silver nano-platelets of  claim 10 , wherein at least 80% of the silver platelets have a thickness within the range of T±20% T, where T is the mean thickness of the silver platelets.