Covalent Functionalization of Silicon Surfaces with a Cavitand-Modified Salen

Si(100) and porous silicon substrates have been engineered with cavitand modified salen molecules. A salen derivative, specifically designed for covalently anchoring on silicon, was grafted onto Si(100) surfaces by photochemical hydrosilylation, and onto porous silicon by thermal hydrosilylation. These hybrid systems have been studied by different analytic techniques. Monochromatized X-ray photoelectron spectroscopy (XPS) was used to characterize both flat and porous samples. Atomic force microscopy (AFM) and, in particular, atomic force lithography (AFL) were used to evaluate the monolayer structure and morphology of the flat silicon surface, while Fourier transform infrared spectroscopy (FTIR) was adopted to probe the hydrosilylation process involving porous samples. The uranyl complex of the salen derivative was directly synthesized on the silicon surface by the reaction between Si-anchored salen and uranyl acetate. This surface-based synthesis suggests that the salen molecules are intact and keep their specific properties after silicon anchoring.