Synthesis of nanosized silver particles by chemical reduction method

Synthesis of nanosized silver particles by chemical reduction using formaldehyde in aqueous solution was studied in this work. Effects of several processing variables such as quantities of alkaline solution and formaldehyde and reaction time were investigated. Effects of protective agents such as PVP (polyvinyl-pyrrolidone) and PVA (polyvinyl alcohol) were also included. The products were mainly characterized for its particle size distribution to provide information on the optimal conditions of synthesis and sufficient stability against coagulation. Our results indicated that for [AgNO3]=0.01 M solution, the addition of [formaldehyde]/[AgNO3]=4, [NaOH]/[AgNO3]=1 and [Na2CO3]/[Ag]=1, together with PVP/Ag weight ratio of 9.27 or PVA/Ag weight ratio of 3.37, could produce silver colloids having sizes between 7 and 20 nm. The suspension was stable for at least 24 h. Silver particles can be easily collected through centrifuge and filtration when the solution is mixed with sufficient amount of acetone. The wet precipitate can be redispersed for further applications with increase in particle size.