Interaction of ZnII porphyrin with TiO2 nanoparticles: from mechanism to synthesis of hybrid nanomaterials.

The mechanism of interaction of Zn porphyrin (ZnPP) with TiO2 surfaces is investigated with a view to optimizing the synthesis of hybrid nanomaterials. The strategy consists of studying the adsorption of ZnPP on TiO2 flat surfaces by taking advantage of complementary surface characterization techniques. Combining a detailed X-ray photoelectron spectroscopic analysis with AFM imaging allows ZnPP-surface and ZnPP intermolecular interactions to be discriminated. Probing the adsorption of ZnPP on TiO2 nanoparticles (NPs) reveals the dominant role of ZnPP-mediated interactions, which are associated with the formation of ZnPP multilayers and/or with the state of aggregation of NPs. These preliminary investigations provide a guideline to synthesizing a novel ZnPP-TiO2 hybrid nanomaterial in a one-step protocol. In this material, ZnPP molecules are presumably involved in the TiO2 lattice rather than on the NP surface. Furthermore, ZnPP molecules preserve their electronic properties within the TiO2 NPs, and this makes the ZnPP-TiO2 hybrid nanomaterial an excellent candidate for nanomedicine and related applications, such as localization of nanoparticles in cells and tissues or in photodynamic therapy.