Synthesis, stabilization, growth behavior, and catalytic activity of highly concentrated silver nanoparticles using a multifunctional polymer in an aqueous-phase

This article proposes an initiative protocol for the aqueous-phase synthesis of highly concentrated Ag nanoparticles with long-term stability, in which the multifunctional polymer in the reaction was found to be of great importance to the formation and stabilization of Ag nanoparticles. Highly concentrated Ag nanoparticles (above 20 g L-1) synthesized by the reaction of AgNO3 with branched polyethyleneimine exhibited long-term stability without any size change or precipitation (more than 40 days). Transmission electron microscopy and UV-vis analysis revealed that aggregation of small Ag nanoparticles occurred at the very early stages of synthesis, and spherical Ag nanoparticles with sizes of around 8 nm were synthesized by coalescence and reshaping of aggregates. We also investigated the influence of reaction temperature and pH of the reacting solution on the Ag nanoparticle synthesis, demonstrating that these experimental factors are critical in terms of reaction completion time, size, size distribution, morphology, and stability of Ag nanoparticles. In addition, the resulting Ag nanoparticles exhibited effective activity in the catalytic reduction of 4-nitrophenol to 4-aminophenol by NaBH4.