Beyond ZnO nanostructure properties: surface functionalization as the key for different applications.

Multiple functional properties of ZnO are very well known and make it an interesting material for different applications, such as optoelectronics, transparent electronics, piezoelectric devices, sensing and catalysis. In particular, when it is obtained in form of nanostructures, most of these properties become strongly surface and/or size dependent. In this work we present an overview on different kinds of surface functionalizations that we used to add further and new functional properties to ZnO nanostructures synthesized in our laboratories. Inorganic and organic semiconductor, superparamagnetic iron oxide nanoparticles and noble metals have been coupled so far with ZnO nanostructures by different physical or chemical techniques and clear enhancements or modifications in their surface reactivity, light absorption, magnetic or other peculiar properties have been observed. Some examples for gas sensing application, photocatalytic degradation of water pollutants and some new ideas for complex geometries in hybrid photovoltaic applications are presented as case studies. Further perspectives for other feasible applications of these multifunctional composite nanostructures are finally discussed.