Double Hydrophilic Block Copolymer Templated Au Nanoparticles with Enhanced Catalytic Activity toward Nitroarene Reduction

We present a facile method for synthesizing water-dispersible gold nanoparticles (Au NPs) using a double hydrophilic block copolymer (DHBC), poly(ethylene oxide)-block-poly(acrylic acid) (PEO-b-PAA), as a template and demonstrate their application in the reduction of nitroarenes. Selective coordinative interactions between a gold precursor and the PAA block of the DHBC lead to the formation of micelles, which are subsequently transformed into Au NPs with an average diameter of 10 nm using a reducing agent. The DHBC-templated Au NPs (Au@DHBC NPs) remain stable in water for several months without any noticeable aggregation. Furthermore, Au@DHBC NPs are found to be highly effective in catalyzing the reduction of a series of nitroarenes. Remarkably, the turnover frequency in the case of 4-nitrophenol using Au@DHBP NPs reaches 800 h(-1), outperforming previously reported Au NP-based catalytic systems. We believe the enhanced catalytic activity is due to the DHBC shell around Au NPs, which templates the formation of spherical Au NPs and, more importantly, provides the confined interior for the enhanced catalytic activity in nitroarene reduction. Considering the wide potential application of DHBC as a template for the synthesis of novel metal NPs, we anticipate that the approach presented in this study will offer a new means to create a variety of water-stable catalytic nanomaterials in various fields of green chemistry.