Effect of Stabilizers in the Synthesis of Silver Nanoparticles and Methylene Blue Oxidation

Metal nanocatalysts have received increasing attention in catalysis due to their higher reactivity and surface area-to-volume ratio at nano-size. Silver nanoparticle (AgNP) is among metal nanocatalysts that have been studied in various catalytic reactions (e.g., hydrogenation and oxidation). However, the high reactivity of AgNPs at nano-size caused instability and aggregation. Therefore, stabilizing molecules (or stabilizers) are always applied to maintain the nano size of AgNPs and prevent aggregation. Herein, the effects of different types and molar ratio of stabilizers-to-Ag precursor, to the synthesized AgNPs (i.e, size and concentration) were investigated. Two types of stabilizers, polyvinylpyrrolidone (PVP) and citrate were used in this study. The roles of stabilizers to the catalytic performance of synthesized AgNPs were then elucidated by using methylene blue oxidation as the model reaction. The UV-Vis absorption analyses showed that both stabilizers produced slightly different size and concentration of AgNPs based on the different wavelength and absorption intensity of the peak. We also found that the molar ratio of stabilizers-to-Ag precursor that produced better yield of AgNPs was 1:1 and 1:3 for PVP and citrate, respectively. Then, AgNPs stabilized by citrate was found having slightly higher catalytic activity in the methylene blue oxidation than AgNPs stabilized by PVP. This study provides insights to the roles of stabilizers for the synthesis of stable AgNPs with efficient catalytic reaction and can be used as guideline to other metal nanocatalysts.