Sintesi e caratterizzazione di sistemi accoppiati g-C3N4-ZnO per applicazioni fotocatalitiche

The present thesis deals with the synthesis and the characterization of semiconductor materials based on carbon nitride and zinc oxide. Graphitic carbon nitride has recently received a great attention due to its interesting chemical-physical properties, its two-dimensional structure and, above all, its moderate bandgap (2,7 eV), which allows for the absorption of solar radiation in the visible light range. The formation of heterojunctions with other semiconductors, in this project we used ZnO, is one of the strategies that allow to delay the recombination of charge carriers by stabilising them on the two different materials, improving their optoelectronic properties and allowing applications particularly relevant for sustainable chemistry, including photocatalysis. Therefore, the purpose of this work was to synthesise zinc oxide, graphitic carbon nitride and carbon nitride coupled to zinc oxide, by following different procedures, with the aim of obtaining nanostructured materials, possibly with a high surface area and good photocatalytic performances. In particular, the heterojunction materials were prepared by developing different synthetic procedures: by following deposition or ultrasound synthesis; another approach involves into the pyrolysis in air of melamine-based precursors; the last approach involves in the preparation of supramolecular aggregates of melamine and cyanuric acid. Almost all the syntheses were performed both in water and in ethanol. The materials thus synthesized were characterized structurally by powder X ray diffraction technique (XRPD), optically with Diffuse Reflectance UV Visible spectroscopy (DR-UV-VIS), morphologically with Field Emission Scanning electron microscope (FE-SEM) and from an electronic point of view with Electronic Paramagnetic Resonance (EPR). The XRPD patterns were used for the recognition and study of the crystalline phases, while the UV-VIS spectra were used for the evaluation of absorption and band gap value. The FE-SEM images of the mixed samples allow a more in-depth morphological analysis of the interface between the two phases, revealing significant differences between the products obtained from the various synthetic procedures. In addition, the EPR characterization allowed the study of the movement of the charges and their nature, in conditions of darkness and illuminance, at room temperature or at cryogenic temperature (77 K). Finally, the photocatalytic performances of the materials thus prepared were evaluated following the degradation of various organic molecules in lake water, this characterization was subsequently performed by the colleagues of the analytical laboratory and the results obtained are still under study.