Significant Parameters in the Optimization of Synthesis of Silver Nanoparticles by Chemical Reduction Method

Silver nanoparticles of narrow size distributions were synthesized by reduction of highly concentrated silver nitrate (AgNO₃) solution with sodium hypophosphite (NaH₂PO₂ · H₂O) in the presence of polyvinyl pyrrolidone (PVP). An orthogonal experimental design (OED) with L₉ orthogonal array was employed as a chemometric method to optimize the experimental conditions for the synthesis of silver nanoparticles. Particle size of silver nanoparticles was considered as the defining characteristics. The concentration of reducing agent, weight ratio of AgNO₃ to protecting agent, and temperature were optimized using a three-level OED and nine experiments. The particle size was characterized to optimize the synthesis conditions. The concentration of reducing agent emerged as the most important parameter influencing the particle size. The temperature also influenced the particle size. Based on 1 M AgNO₃ solution and 0.1 M NaH₂PO₂ · H₂O, 1.7 g silver nanoparticles of 10-50 nm were obtained from 3.4 g silver nitrate with weight ratio of PVP/AgNO₃ equal to unity at 40 °C.