Aqueous-based dispersions of metal nanoparticles

Abstract

The invention relates to a method for preparing an aqueous-based dispersion of metal nanoparticles comprising: (a) providing an aqueous suspension of a metal salt; (b) pre-reducing the metal salt suspension by a water soluble polymer capable of metal reduction to form a metal nuclei; and (c) adding a chemical reducer to form metal nanoparticles in dispersion. The invention further relates to aqueous-based dispersions of metal nanoparticles, and to compositions such as ink comprising such dispersions.

1 . An aqueous-based dispersion comprising metal nanoparticles and at least one water soluble polymer, said aqueous-based dispersion is characterized by:
 (a) the concentration of said metal nanoparticles in said dispersion is in the range 0.5-35 wt %;   (b) the size of said nanoparticles is below 20 nm in diameter;   (c) the weight ratio of said water soluble polymer to said metal nanoparticles is below 0.1:1; and   (d) up to 25%, based on the total weight of the dispersing medium of organic solvents.   
     
     
         2 . An ink composition, comprising the aqueous-based dispersion of  claim 1 . 
     
     
         3 . An aqueous-based dispersion comprising metal nanoparticles and at least one water soluble dispersant, said aqueous-based dispersion is characterized by:
 (a) the concentration of said metal nanoparticles in said dispersion is in the range 5-80 wt %;   (b) the size of said nanoparticles is below 20 nm in diameter;   (c) the weight ratio of said water soluble dispersant to said metal nanoparticles is below 0.1:1; and   (d) up to 25%, based on the total weight of the dispersing medium of organic solvents.   
     
     
         4 . An ink composition, comprising the aqueous-based dispersion of  claim 3 .