Shedding light on precursor and thermal treatment effects on the nanostructure of electrospun TiO2 fibers

• TiO2 fibers were prepared by electrospinning technique.
• Ti oxysulfate and (Bendoni et al., 2015) Ti n-butoxide (TNBT) used as precursors along with PVP.
• Anatase crystallites of about 5 nm were obtained in O2 at 450 °C with TNBT precursor.
• Precursor crystallization occurred already at RT during the electrospinning process.
• Electrospray technique did not give the same promising results.

Electrospinning technique was employed for the synthesis of different TiO2 samples, starting from titanium oxysulfate and titanium n-butoxide (TNBT) as precursors. The electrospun fibers, obtained after optimization of starting solutions, were either calcined in air at 450 °C or treated in 50 mbar of pure oxygen at 450 °C. The main goal was to obtain TiO2 fibers constituted by crystallites with size lower than 10 nm (size largely reported in literature for this kind of synthesis) in the anatase form. Before thermal treatment, the morphology of the fibers was characterized by Scanning Electron Microscopy (SEM); after thermal treatment TiO2 morphological and structural properties were determined by Transmission Electron Microscopy (TEM) as well as by high resolution (HR-) TEM and X-ray Diffraction (XRD).TiO2 prepared with TNBT precursor and treated in oxygen at 450 °C gave the best results in terms of crystalline phase (pure anatase) and particle size (about 5 nm). Moreover, HR-TEM analysis of the fibers obtained from TNBT before thermal treatment revealed that the precursor crystallization occurred already at room temperature during the electrospinning process, giving rise to nucleation germs for the subsequent growth of TiO2 crystallites during the thermal treatment. On the contrary, samples prepared by electrospray and by simple solvent evaporation at room temperature of the solution with the same TNBT precursor did not give the same promising results in terms of crystalline phase and particle size.

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