Fabricating fiber, rice and leaf-shaped TiO2 by tuning the chemistry between TiO2 and the polymer during electrospinning

Electrospinning is a facile technique for the fabrication of nanofibers (one-dimensional, 1D, nanostructures) of metals, metal oxides and polymers on a commercial scale which find applications in the fields of energy (dye-sensitized solar cells, Li-ion batteries, fuel cells, etc.), healthcare, environmental engineering and biotechnology (membranes and filters). While electrospinning polymer solutions results in polymer nanofibers, metal oxide nanofibers (say of TiO2) are made by electrospinning a TiO2 precursor along with a polymer into composite nanofibers and subsequently removing the polymer by a sintering process. However, we have found that the morphology of the electrospun TiO2 depends on the chemical nature of the polymer involved and more precisely the chemical interactions between the polymer and the TiO2 during the sintering process. When the polymer is changed from polyvinyl pyrrolidone (PVP) to polyvinyl acetate (PVAc) to a mixture of PVP and PVAc, the morphology of the TiO2 varies from continuous fibre to rice-shaped to leaf-shaped. The present manuscript explores the chemistry between the TiO2 and the above mentioned polymers which results in the structural anisotropy of the electrospun TiO2. The electrospun metal oxides are useful for energy and environmental applications.