Alkoxysilane effect in hybrid material: A comparison of pHEMA-TiO2 and pMAPTMS-TiO2 nanoparticulate hybrids

We report on a comparative study of photonic sensitivities of organic-inorganic hybrids prepared with size-selected 5 nm titanium-oxo-alkoxo nanoparticles and two different organic phases: HEMA (2-hydroxyethyl methacrylate) and MAPTMS (3-methacryloxypropyltrimethoxysilane). After organic polymerization, the obtained pHEMA-TiO2 and pMAPTMS-TiO2 hybrids are solids with different inter-component bindings. While surface exchange fixes organic (HEMA than pHEMA) groups on the nanoparticle surface, the titanium-oxo-alkoxo nanoparticles do not interact with the organic component in the pMAPTMS-TiO2 hydrid. Indeed, MAPTMS molecules are hydrolyzed forming condensed Si-O-Si species. The formation of Si-O-Ti bonds is observed at the organic thermal polymerization stage, which may be a signature of the silica layer formation at the particles surface. Consequently, the quantum efficiency of the photoinduced charge separation and storage in pMAPTMS-TiO2 hybrids is found considerably lower compared to that in pHEMA-TiO2 hybrids. The 3D micro structuring of the hybrid solutions has been realized using 2-photon laser polymerization. The structures were mechanically more stable and easier to achieve in pMAPTMS-TiO2 compared to pHEMA-TiO2. Moreover, higher density of the photoinduced electrons decreases the damage threshold in the pHEMA-TiO2 hybrids.