Photochemical synthesis of dendritic silver particles

Abstract

Forming dendritic silver particles by combining silver ions, a reducing agent, and a polymer comprising amine groups in an aqueous solution to yield a precursor solution, and irradiating the precursor solution with ultraviolet radiation to form a multiplicity of dendritic silver particles. A desired morphology of the dendritic particles, including branch and junction density, may be achieved by selecting growth parameters, such as molar ratio of amine groups to silver ions, a length of time of irradiating, or both.

What is claimed is: 
     
         1 . A method of forming dendritic silver particles, the method comprising:
 combining silver ions, a reducing agent, and a polymer comprising amine groups in an aqueous solution to yield a precursor solution; and   irradiating the precursor solution with ultraviolet radiation to form a multiplicity of dendritic silver particles.   
     
     
         2 . The method of  claim 1 , wherein the reducing agent comprises an organic acid. 
     
     
         3 . The method of  claim 1 , wherein the reducing agent comprises citric acid or ascorbic acid. 
     
     
         4 . The method of  claim 1 , wherein a molar ratio of silver ions to the conjugate base of the weak acid in the precursor solution is in a range of about 3 to about 3.5. 
     
     
         5 . The method of  claim 1 , wherein the polymer comprising amine groups is poly(allylamine). 
     
     
         6 . The method of  claim 1 , wherein a pH of the precursor solution is in a range of about 12 to about 13. 
     
     
         7 . The method of  claim 1 , wherein a molar ratio of amine groups to silver in the precursor solution is between about 6 and about 12. 
     
     
         8 . The method of  claim 1 , wherein irradiating the precursor solution occurs under ambient conditions. 
     
     
         9 . The method of  claim 1 , wherein the precursor solution is irradiated with ultraviolet radiation for at least 3 minutes. 
     
     
         10 . The method of  claim 9 , wherein the precursor solution is irradiated with ultraviolet radiation for up to 20 minutes. 
     
     
         11 . The method of  claim 1 , wherein the wavelength of the ultraviolet radiation is in a range of about 320 nm to about 400 nm. 
     
     
         12 . The method of  claim 1 , wherein the ultraviolet radiation has an output power in a range of about 1.5 W/cm 2  to about 4 W/cm 2 . 
     
     
         13 . The method of  claim 1 , wherein the dendritic silver particles have a linear dimension up to about 100 microns. 
     
     
         14 . The method of  claim 1 , wherein the dendritic silver particles are dendritic silver nanoparticles. 
     
     
         15 . The method of  claim 1 , wherein the dendritic silver particles comprise at least 95 wt % silver. 
     
     
         16 . The method of  claim 1 , wherein a branch density of the dendritic silver particles is in a range of about 0.1×10 5  branch/mm 2  to about 11×10 5  branch/mm 2 . 
     
     
         17 . The method of  claim 1 , wherein a junction density of the dendritic silver particles is in a range of about 1×10 4  junction/mm 2  to about 36×10 4  junction/mm 2 . 
     
     
         18 . The method of  claim 1 , wherein a fractal dimension of the dendritic silver particles is in a range of about 1.4 to about 1.9. 
     
     
         19 . The method of  claim 1 , wherein each dendritic silver particle of the multiplicity has a unique structure. 
     
     
         20 . The method of  claim 1 , further comprising selecting a molar ratio of amine groups to silver, a length of time of the irradiating, or both to achieve a desired morphology of the multiplicity of dendritic silver particles.