We demonstrate the reduction of gold on silica monoliths by decoration of amine and imine functionalities on the surface of silica. The reduction of gold was found to be more facile on imine decorated silica, due the strong electrostatic interaction of highly polarized imine with Au³⁺ ions.

Abstract

We demonstrate the reduction of gold (Au) on silica monoliths by surface decoration of amine and imine (formed by reaction of amine present in 3-amino propyl triethoxy silane (APTES) and acetone) functionalities on the surface of silica. The reduction of Au³⁺ to Au⁰ was confirmed by X-ray diffraction (XRD), UV-Diffuse reflectance and X-ray Photo electron spectroscopic techniques. Without employing the conventional strategies with reducing agents like sodium borohydride and sodium citrate, here, the surface functionalized amine and imine was found to reduce the metal ions, additionally, the surface silanols was found to anchor and serve as the adsorption sites to hold the metal ions prior to reduction. The control experiment was performed with silica monoliths without the surface functionalities displayed no evident reduction of Au³⁺ to their respective metallic form. Interestingly, the reduction of Au was found to be more facile on imine modified silica, due to the strong electrostatic interaction of highly polarized imine with Au³⁺ ions.