Electrospun ZnO was deposited on a glass substrate from zinc acetate dihydrate (Zn(CH 3 COO) 2 .2H 2 O) with polyvinyl acetate (PVAc) polymer dissolved in N, N, dimethyl formamide (DMF) and annealed in the presence of oxygen until organic molecules were decomposed. The resultant fibre was characterized using scanning electron microscope with energy dispersive spectrophotometry (SEMEDS), Fourier transform infrared (FTIR), and Rutherford backscattering spectroscopy (RBS). SEMEDS and FTIR exhibited a total decomposition of the organic precursor. The mean fibre width was found to be 260 nm, and fibre thickness was measured at 460 nm. XRD patterns indicate that ZnO was corundum with the hexagonal wurtzite structure. The crystallite size was determined by the Debye formula to be 54 nm. The optical analysis indicated that the percentage transmittance increased after calcination. The material band gap for this electrospun ZnO fibre was found to be 3.28 eV. The material optical parameters such as dispersion energy, average oscillator strength, and single oscillator strength were also calculated. The optical conductivity and dielectric plot demonstrated that the material conductivity and dielectric properties increase with increasing photon energy and increase sharply around the material energy bandgap. The Urbach tail analysis of the materials shows that they obey the Urbach rule. Therefore, the n-type electrospun ZnO fibre high refractive index is attributable to the presence of excess oxygen.

Many metal oxide heterostructures have been synthesized as mixed oxides or layered structures for photocatalytic, photodegradation of pollutants and light-harvesting applications. However, in the layered structures the effects of interfacial properties and composition have largely not been explored. Hence, the effects of interfacial mixing and diffusion of sandwiched thin CuO layer on optical absorption of as-deposited and heat-treated multi-layered structured SnO2/CuO/SnO2 films were studied. The RBS analysis of the as-deposited films showed the presence of a minute amount of Cu in the surface and bottom SnO2 layers of the structure. We attributed this to inhomogeneous layer thickness evidenced by very low Sn/Cu atoms ratio of the CuO layer. However, the thermal treatment of the layered structure led to pronounced interlayer mixing and consequent formation of SnO2-CuO solid solutions throughout the layered structure. The layer integrity of the inserted CuO of the as-deposited films was very high and the as-deposited structure was far more optically absorbing. However, the annealed structure showed lesser optical absorption because of the onset of interfacial mixing and improved crystallization. This reflected in the optical bandgap variations of the as-deposited and annealed multilayered structures. The significance of this result is that the multi-layered films possess band narrowing – evidence of increased photon absorption - making it a better candidate than pure SnO2 oxide for photocatalysis, photodegradation and photodetection applications. It also pointed to the fact that attention must be paid to effects of heat treatments or annealing when inserting an absorbing layer into a photocatalyst or a material meant for photodegradation or any light-harvesting material.

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