Preparation of Nano-Sized Ag Metal Colloid by an Advanced Wet-Process Using 3-Mercapto-Propionic Acid

摘要

For the synthesis of the nano-sized Ag metal particle, the sodium borohydride for the reducing agent was added into the aqueous solution of the AgNO_3 with 3-mercapto-propionic acid as protective agent. Because the surface of nano-sized Ag metal particle was protected by the adsorbed 3-mercapto-propionic acid, the synthesis of the aqueous colloid system with high density became possible. The negative charge of carboxylate anion protect the aggregation of metal particles in the solution of high pH value (pH > 5), but the aggregation was occurred in the solution of low pH value (pH < 2). By changing the quantity of the agent of propionic acid and the pH value of solution, the particle size can be controlled optionally in the range of 50～200 nm.