Synthesis of a biomimetically formed core–shell SiO2@Ag photocatalyst for the degradation of aqueous organic pollutants

Abstract

In this paper, a novel photocatalyst is prepared, characterized and tested. This material comprises a biomimetically formed silica core and silver based nanospheres, strongly attached to the substrate. The synthesis of the silica substrate is achieved by employing a silica precursor, tetraethyl-orthosilicate, and a dendritic polymer, poly(ethylene)imine. The latter enables the formation of silica cores through biosilification by regulating the pH with phosphate buffer solutions. These cores with a mean diameter of 200 nm, allow the formation of silver-based photocatalysts (10 nm) on their surface with the addition of silver nitrate and sodium hydrogen carbonate. Silver, silver carbonate and silver phosphate act synergistically regarding their photocatalytic performance. Furthermore, their immobilization on silica substrates enhances their photostability while silica prevents the formation of silver agglomerates. The structure of the catalyst was examined through Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray diffraction analysis and Fourier Transform Infrared Spectroscopy. Moreover, the photocatalytic properties were assessed by a model reaction, the reduction of 4-nitrophenol to 4-aminophenol using Ultraviolet–visible spectroscopy. Finally, the reusability of the photocatalyst was also examined. In conclusion, a viable photocatalyst, suitable for the degradation of 4-nitrophenol, is presented (100 % during the first and second cycle and 98 % during the third cycle).