Annealing effect on structural and optical properties of nanostructured carbon of oil fly ash modified titania thin-film

Dopants and crystallisation influence the photocatalytic performance of eco-friendly titania nanocomposites and consequently improve the quality of applications using titania nanocomposites. In this work, oil fly ash was used as the starting material for producing carbon nanomaterials prepared by high-energy ball milling in an acetic acid medium. Titania/carbon from a carbonaceous oil fly ash (TiO2/COFA) nanocomposite thin-film was fabricated on glass substrates via the spin-coating method. The obtained nanocomposites were then treated using advanced heat technology, where pressure, temperature rate and time duration were controlled. The structural, morphological, optical, and photoluminescence properties of annealed TiO2/COFA thin films are revealed for the first time. Between 300 and 500 degrees C, energy dispersive X-ray spectroscopy (EDS) analysis showed the successful doping of 7 wt% carbon nanoparticles in the TiO2 films. Structural development occurred in the anatase phase, including a decrease in the internal lattice strain and dislocation density and an increase in the crystallite size, leading to improved TiO2/COFA thin films as confirmed by atomic force microscopy (AFM) and scanning electron microscopy (SEM) images. According to the optical investigations, there were increases in the absorbance, transmittance, and band gap of vacuum-annealed TiO2/COFA thin films with increasing annealing temperatures. The annealed thin films had a higher Urbach's energy, and the photoluminescence intensities increased at 500 degrees C, indicating an abundance of defect-induced local electronic states and, subsequently, an improvement in the optical performance of the layers. These results suggest that the nanocomposite thin films may have potential for use as eco-friendly light-harvesting layers in solar cell components.