Cucurbit[7]uril-stabilized gold nanoparticles as catalysts of the nitro compound reduction reaction

Abstract

The catalytic performance of cucurbit[7]uril-protected gold nanoparticles is reported for the first time for the reductive degradation of the banned but still used antibacterial compound nitrofurantoin. The cucurbit[7]uril-protected gold nanoparticles were produced by Au(III) reduction by sodium borohydride and subsequent addition of cucurbit[7]uril as a ligand. Working in this way, 5.7 nm gold nanoparticles were obtained and characterised by spectrophotometric and high-resolution transmission electron microscopic techniques. For a 1 : 100 nitro compound : sodium borohydride molar ratio, a normalised pseudo-first order apparent constant of 0.27 L s⁻¹ m⁻² at 25 °C and an activation energy of 34 kJ mol⁻¹ were obtained. For comparative purposes, the reduction reaction of the pollutant 4-nitrophenol was also studied and an apparent kinetic constant of 0.12 L s⁻¹ m⁻² at 25 °C and an activation energy of 68 kJ mol⁻¹ were obtained, data that, when compared with recently reported work, demonstrates that these nanoparticles are an efficient catalyst.