Patent ID: 7846976

Claim:
A process for producing nano-sized metallic fine particles by chemically reducing metallic ions, wherein the reduction of the metallic ions is performed in 2 steps using two types of reducing agents which significantly differ in reducing ability thereof, a reducing agent in which the reduction ability is strong, referred to as “strong reducing agent”, is used in the first reduction step, and a reducing agent in which the reduction ability is weak, referred to as “weak reducing agent”, is used in the second reduction step, wherein in the first reduction process, the strong reducing agent is added to an aqueous metallic salt solution, and the reduction is preformed until the amount of metal ions in the aqueous metallic salt solution is 50 to 1%, and subsequently, wherein in the second reduction process, the weak reducing agent is added to an aqueous metallic salt solution, and the reduction is preformed until the amount of metal ions in the aqueous metallic salt solution is substantially 0%, and wherein as the strong reducing agent of the first reduction process, at least one selected from the group consisting of boron hydride, dimethylamine borane, hydrazine, and ascorbic acid is used and wherein as the weak reducing agent of the second reduction process, at least one of alkylamine and alkanolamine is used, which is represented by the following formulas (1) to (4): H 2 NR (R:C n H 2n+1 , n=integer of 1 to 8) formula (1) HNR 2 (R:C n H 2n+1 , n=integer of 1 to 8) formula (2) NR3:(R:C n H 2n+1 , n=integer of 1 to 8) formula (3) N(ROH) 3 (R:C n H 2n , n=integer of 1 to 8) formula (4).