Growth of silicalite-1 films on gold substrates

The crystallisation of thin continuous silicalite-l films on modified gold surfaces prepared at 100 degrees 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-l 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-l films on Au is discussed. (C) 1997 Elsevier Science B.V.