To fabricate WO3 nanofibers, first a mixture of tungsten oxide precursor and a conducting polymer
used to control viscosity of the solution are prepared. The precursor solutions are prepared by mixing
ammonium metatungstate hydrate (AMH) in de-ionized water (DI) at 16.7% w/v, 33.3% w/v and 50.0%
w/v concentrations. The conducting polymer is prepared by mixing polyvinyl alcohol (PVA) with deionized
water (DI). Finally, the precursor and polymeric solutions are mixed and stirred vigorously for 24
h to obtain a homogeneous solution. The solution is then fed into the electrospining setup. The feed rate,
the high voltage power supply, and the distance between the injection needle and the collector plate are
fixed at 0.3 ml/min, 19.5 kV, and 15 cm, respectively. The nanofibers are electrospun onto pre-patterned
Pt interdigitated electrodes. The resulting nanofibers are hot-pressed at 120ºC and calcined at 500ºC,
700ºC and 900ºC to remove the polymer and to carry out growth in some samples.