Unusual Stability and Catalytic Activity of Gold Nanoparticles in Polyoxyethylene Cholesteryl Ether

We report a simple and spontaneous method for creation of extremely stable and catalytically active gold nanoparticles (AuNPs) from polyoxyethylene cholesteryl ether (ChEO₁₅) and sodium tetrachloroaurate (III) dihydrate (Na[AuCl₄] · 2H₂O). AuNPs with uniform size and distribution were prepared at 27 °C (AuNPs were formed in <3 h) and at 50 °C (AuNPs were formed in <1 h). Our elucidations propose that creation of well-defined AuNPs is assisted by reductive ChEO₁₅ surfactant solution via complexation and in-situ reduction of AuCl^-₄ ions in which ChEO₁₅ acts both as a reducing and consequently a stabilizing (capping) moiety. AuNPs size can be altered by suitably choosing the Au precursor concentration. The resulting AuNPs reveal outstanding catalytic activity for conversion of nitrophenols to aminophenol in the presence of NaBH₄ and also exhibit synthetic peroxidase-like activity. This simple yet effective synthesis technique opens prospect for creation of stable and active AuNPs.