The self-assembly of gold nanoparticles in large-pore ordered mesoporous carbons

Abstract

Simple encapsulation of 3 nm gold nanoparticles in ordered mesoporous carbon with large pores of 17 nm and thick pore walls of 16 nm was achieved by a metal–ligand coordination assisted-self-assembly approach. Polystyrene-block-polyethylene-oxide (PS-b-PEO) diblock copolymer with a large molecular weight of the PS chain and mercaptopropyltrimethoxysilane were used as the template and the metal ligand, respectively. Small-angle X-ray scattering, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy showed that monodispersed aggregation-free gold nanoparticles approximately 3 nm in size were partially embedded in the large open pore structure of the ordered mesoporous carbon. The strong coordination between the gold species and the mercapto groups and the thick porous walls increased the dispersion of the gold nanoparticles and essentially inhibited particle aggregation at 600 °C. The gold nanoparticles in the ordered mesoporous carbon are active and stable in the reduction of nitroarenes involving bulky molecules using sodium borohydride as a reducing agent under ambient conditions (30 °C) in water. The large interconnected pore structure facilitates the mass transfer of bulky molecules.