Growth of silicalite-1 films on gold substrates

The crystallisation of thin continuous silicalite-1 films on modified gold surfaces prepared at 100°C in clear precursor solutions has been studied by grazing angle X-ray diffractometry, infrared spectroscopy, dynamic light scattering, scanning electron microscopy, Kr adsorption and ellipsometry. The gold surfaces were pre-treated with a silane coupling agent, gamma-mercaptopropyltrimethoxysilane, and hydrolysed in an acidic solution, pH<4, to create a modified negatively charged interface on which positively charged colloidal silicalite-1 seed crystals were adsorbed. The colloidal seed crystals are believed to be preferentially adsorbed with their {010} face parallel to the Au surface. Continued growth of the oriented seed crystals in a following hydrothermal step results in the formation of a continuous thin oriented crystalline film. The mechanism for the formation of silicalite-1 films on Au is discussed.