Enhanced stability of gold nanoparticles capped with double hydrophilic block copolymers synthesized by eATRP

In this study, the gold nanoparticles (Au NPs) are capped with a novel, well-defined double hydrophilic block copolymer, poly (ethylene glycols)-block-poly(mono-2-(methacryloyloxy) ethyl succinate) (PEG-b-PSEMA). The PEG-b-PSEMA, with long side chains and relatively narrow dispersity index, is successfully prepared by aqueous electrochemically mediated atom transfer radical polymerization using a PEG-Br macroinitiator (M n ≈2000 g mol −1 ). By simply mixing PEG-b-PSEMA and Au precursor before adding reductants, coulombic interactions occur between the Au precursor and the carboxylate group of the PSEMA, as a result dense Au NPs are formed. This enables the Au NPs to remain dispersed even in the presence of temperature variations, pH adjustments, and incubation in organic solvents. Au NPs were endowed by PEG-b-PSEMA with more remarkable catalytic activity in organic solvents of 4-nitrophenol into 4-aminophenol than by sodium citrate (Au@citrate) and MeO-PEG-OH (Au@PEG). In addition, PEG-b-PSEMA-stabilized Au NPs (Au@PEG-b-PSEMA) were also tested for the dye degradation property against Rhodamine-B in only pH 10 basic solution, and over 99% of dye degradation can be achieved in 9 min. PEG-b-PSEMA induces coulombic interactions with Au NPs, providing outstanding stability for catalytic applications in organic or specific acidic-base environments.