Photosensitization of Inorganic Semiconducting Nanostructures for Solar Energy Conversion

The engineering of efficient solar energy conversion devices with Earth-abundant elements is of paramount importance to meet the energy demands of a carbon-neutral society and to mitigate environmental damage. Converting solar energy into clean solar fuels and to drive industrially relevant processes is an attractive alternative to address the global energy problem. Typical molecular methods for the production of solar fuels make use of photosensitizers containing precious metals in order to harvest visible light. Carbon dots and kesterite nanocrystals have both recently and separately been considered as suitable candidates to photosensitize metal oxide structures due to their low cost and absorption across the visible portion of the solar spectrum. The physical and electronic architecture of these nanohybrids is a crucial factor that will dictate their optical and catalytic properties. In this work, the photosensitization of zinc oxide nanowires with carbon dots to produce solar fuels is explored. In addition, due to the unknown formation pathway of carbon dots, the formation mechanism for the synthesis of kesterite Cu2ZnSnS4 nanocrystals is evaluated to achieve better control at tuning the optical and photocatalytic properties of nanomaterials. The carbon dot system is employed as a heterogeneous photocatalytic electrode surface for the α-heteroarylation of 1-phenylpyrrolidine and the generation of a high value-added benzyl amine pharmacophore. Furthermore, insight into possible mechanisms of electron transfer between the photoelectrode andorganic substrate is presented. Regarding the kesterite nanocrystals, the optimization of their synthesis to tailor the size dispersity is investigated given the strong correlation between the size and function of nanomaterials. A non-classical formation mechanism is suggested with the formation of a copper-sulfide intermediate followed by the incorporation of Sn4+ and Zn2+ through cation exchange.