Thermal and (photo-)catalytic properties of Poly(N-isopropylacrylamide)-stabilised gold nanoparticles induced by radiolysis

Abstract

Gold nanoparticles (AuNPs) are widely studied due to their unique physicochemical properties, which are highly dependent on their size, shape, and composition. Efficient and environmentally friendly synthesis methods and effective stabilisation agents are essential for fabricating AuNPs with controlled sizes and shapes. This study explores the radiolytic synthesis method, a green synthesis approach using ionising radiation (gamma irradiation), and investigates the use of a thermosensitive polymer, Poly(N-isopropylacrylamide) (PNIPAM), and its monomer, N-isopropylacrylamide (NIPAM), for stabilising gold nanoparticles in aqueous solutions. The resulting PNIPAM-AuNPs and NIPAM-AuNPs were spherical, homogenously dispersed, with average sizes of 5.4 nm and 3.5 nm, respectively, and exhibited high stability at room temperature over a long time. Thermal analysis revealed enhanced thermal responsiveness for PNIPAM-AuNPs, an effect not observed with the NIPAM-AuNPs. The AuNPs demonstrated excellent catalytic activity in the reduction of 4-nitrophenol (4-NP) in the presence of sodium borohydride and showed efficient plasmonic photocatalytic activity in the visible lightdriven reduction of 4-nitrothiophenol (4-NTP). These findings support the potential of radiolytically synthesised polymerstabilised AuNPs for catalysis and environmental remediation applications.