Competitive effects of polymeric ligands molecular weight on the gold colloidal nanocatalysts: Impact of catalysts design and catalytic performance

Abstract

This research investigates the influence of hydro-soluble polymeric ligands on the properties and catalytic performance of colloidal gold nanoparticles supported on activated carbon. The aim was to understand how polymer molecular weight affects Au nanoparticle size, dispersion, and catalytic activity, providing a framework for optimizing catalysis from the design phase. Three polymeric ligands (PVA, PEO, and PVAm) with different molecular weights were synthesized via controlled chain-transfer-to-solvent reactions and used to prepare supported colloidal Au nanoparticles through sol-immobilization. The results demonstrated that molecular weight significantly impacts Au nanoparticle size. Moreover, catalytic activity was assessed using the reduction of 4-nitrophenol as a model reaction. As polymer molecular weight increased, the apparent kinetic constant (k_app) decreased, particularly for PEO-based catalysts, where k_app decreased by an order of magnitude. Higher molecular weight polymers also formed dense polymeric "brushes," hindering reagent diffusion and reducing catalytic performance. Further analysis of Au/polymer weight ratios revealed that decreasing polymer content improved catalytic activity, particularly in Au-PVAm catalysts. The findings underscore the crucial role of polymeric ligands in colloidal nanocatalyst design, emphasizing the need to investigate the metal-polymer interface to optimize catalyst properties.