Systematic Study of the Structure–Property Relationships of Branched Hierarchical TiO₂/ZnO Nanostructures

We report a simple and effective route for fabricating branched hierarchical nanostructures of TiO(2)/ZnO by combining electrospinning and the low-temperature hydrothermal growth technique. First, TiO(2) nanofibers were prepared by electrospinning polystyrene (PS)/titanium tetraisopropoxide (Ti(OiPr)(4)) solutions onto glass substrates followed by calcination at 500 °C. The electrospun TiO(2) nanofibers served as a 3D primary platform upon which the branched, highly uniform, and dense secondary ZnO nanorods were hydrothermally grown. We observed that the concentration of Ti(OiPr)(4) in the polystyrene solution has a significant effect on the surface roughness and areal material ratio of the electrospun fibers. Most significantly, the morphology of the branched secondary ZnO nanorods and the overall charge transfer capacity of the nanoheterostructured systems are controlled by the density of the TiO(2) platform. This study demonstrates that, by properly choosing the synthesis parameters, it is possible to fine-tune the microscopic and macroscopic properties of branched hierarchical metal-oxide systems. The presented approach can be applied to the development of controlled, reproducible, miniaturized, and robust high-performance metal-oxide photovoltaic and photocatalytic systems.