Metal oxoclusters as molecular building blocks for the development of nanostructured inorganic-organic hybrid thin films

Silica-based inorganic-organic hybrid thin films embedding the organically modified oxohafnium clusters (Hf4O2(OMc)(12), OMc=OC(O)-C(CH3)=CH2) were obtained by photo-activated free radical copolymerisation of the methacrylate groups of the cluster with those of the pre-hydrolysed (methacryloxypropyl)trimethoxysilane (MAPTMS, (CH2=C(CH3)C(O)O)(CH2)(3)Si(OCH3)(3)). By this route, a covalent anchoring of the cluster to the forming silica network was achieved. Samples characterized by two different Si/Hf compositions (18:1, 5:1) were prepared. The surface and in-depth composition of the thin films were investigated through Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). XPS depth profiles performed on the thin layers evidenced a homogenous in depth distribution of the hafnium guest species within the whole silica films and sharp film-substrate interfaces.