Modifications under irradiation of a self-assembled monolayer grafted on a nano-porous silica glass: a solid-state NMR characterization

Controlled pore glasses with a pore size of 8 nm are grafted with chlorodimethylsilane (ClSi(CH3)2H). The surface of the glass is carefully characterized before and after irradiation with 10 MeV electrons by solid-state NMR measurements. 1H MAS NMR experiments in one and two dimensions (2D double quantum and 2D exchange) have been used to reveal the grafting of the chlorodimethylsilane at the silica surface and evidence the formation of a homogeneous layer on the surface. Irradiation leads to a high H2 yield (3.3 * 10-7 mol/J) due to the efficient cleavage of the Si H bond. Methane is detected in smaller quantities (5.5 * 10-8 mol/J), indicating that the Si-H bond is preferentially cleaved over the Si-C bond. The H2 production arising from OH groups on the surface is very minor in comparison to the S- H and Si-C radiolysis. (authors)