Interaction of Gold with Co-Condensed and Grafted HMS-SH Silica: A 29Si {1H} CP-MAS NMR Spectroscopy, XRD, XPS and Au LIII EXAFS Study

Hexagonal mesoporous silica (HMS) is functionalised with mercaptopropyl groups by adopting two different procedures; co-condensation and grafting. In both cases tetraethylorthosilicate (TEOS) and 3-mercaptopropyltriethoxysilane (3-MPTES) are used as the silicon and sulfur precursors, respectively. The obtained materials are analysed by several techniques such as N2 sorption, TG-DTA, XRD, SAXS and-solid state 29Si {1H} CP-MAS NMR spectroscopy. By taking advantage of the chemical interaction between gold and the –SH groups, the effect of the thiol addition procedure on the supporting capability of the functionalised silica is evaluated by depositing gold through the incipient wet impregnation technique. The influence of the functionalisation method on the electronic structure of gold and on its surface distribution is determined by extended X-ray fine absorption spectra (EXAFS) of Au at the LIII edge and by X-ray photoelectron spectroscopy (XPS).