Selective Functionalization of ZnO nanostructure for electronic, gas sensing and photovoltaic application

Organic-inorganic hybrid nanostructures are receiving considerable attention for the development of "smart" materials with new tailored properties. The interaction between nanostructure and organic molecules give rise to transduction effects, in charge and excitation exchange, that could improve the electric properties of the material. A key iussue to obtain effective useful materials is the control of the functionalization at the nanoscale. We approch the functionalization of ZnO nanostructures using directional and kietical properties of the molecular beams in different ways. We selective functionalize ZnO nanostructures, with organic oligomers, using Supersonic Molecular Beam Deposition (SuMBD), applying the directional properties of the seeded supersonic beams. We used ZnO because of its ability to form controlled nanostructures with semicondacting properties. We applied SuMBD to ZnO nanorods [1], which present interesting advantages, especially in solar cells applications. First of all, ZnO nanorods present a continuous crystalline structure, which could be grown on a conductive transparent metal oxide (TCO) made ZnO doped with Aluminium (AZO) deposited directly on glass [2]. In such a way, the structural homogeneity and crystalline properties are maintained all over the NR length, allowing a continuous path for the electrons in the material. Using the directional properties of the beam, a selective functionalization, only on one specific side of the nanorod, has been realized. Moroever we used Vapour phase deposition to functionalize ZnO nanotrapods for gas sensing application. It has already been demonstrated that the combined use of nanostructured metal oxides and organic molecules improves the selectivity in gas sensing performances at least in the case of TiO2 [3]. We realized gas sensor devices based on films of interconnected ZnO nanoterapods opportunely functionalized by Titanyl Phthalocyanine. The aim is to combine the high surface area ratio and the structural property of the crystalline structure of the ZnO nanoterapods with the sensitivity of the interaction, meditated as a transducer, of the TiOPc molecule. The electronic properties of the nanohybrid material results different from the single behavior of each component. The dynamic in time and the sensing properties have been studied. The presence of a charge exchange at the hybrid interface results is crucial determine the response and the selectivity. ZnO nanohybrids result very useful to reach important changes in the efficency of different devices.