Aluminium and nickel-doped zinc oxide thin films fabricated through the aqueous spray-coating method and evaluations of their photocatalytic activities
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Date
2025
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University of Namibia
Abstract
This work introduces the aqueous spray-coating method to address the challenges in
the fabrication of thin films for photocatalytic applications. The aqueous spray-coating
method has shown to be an effective method for the fabrication of undoped, aluminium
(Al), and nickel (Ni)-doped Zinc Oxide (ZnO) thin films on quartz glass substrates
with many advantages, such as simple instrumentation set-up, inexpensiveness, the
ease of controlling the rate of deposition, and high yield. An aluminium (Al3+) complex
salt was synthesised in this study as a source of Al3+ ions in the prepared precursor
solutions for fabricating Al-doped ZnO thin films. The synthesised complex was
characterised using Fourier transform infrared (FTIR) spectroscopy. The various thin
films were fabricated by depositing the prepared aqueous precursor solutions
containing Zn2+ complexes alone as well as Zn2+ with varying mole percentages (2, 4,
8, and 16%) of Al3+ or Ni2+ complexes onto pre-heated quartz glass substrates, and the
as-sprayed films were heat-treated at 450oC for 30 minutes. The structural, optical,
morphological, and photocatalytic characteristics of the fabricated thin films were
evaluated using X-ray diffractometer (XRD), ultraviolet–visible (UV–Vis)
spectrophotometer and scanning electron microscope (SEM). The XRD results
revealed that the fabricated thin films have a hexagonal wurtzite phase. The optical
properties (absorbance and transmittance) of the fabricated thin films were analysed
using the UV–Vis spectrophotometer, and all the fabricated thin films showed high
transmittance in the visible region over 70%, even after Al and Ni doping. Experiments
on methyl orange dye degradation in the presence of the fabricated thin films under
visible light showed that Al-doped ZnO exhibits good photocatalytic activities that
increase with an increase in the doping mole% of Al. On the contrary, Ni-doped ZnO
thin films exhibited a very slight to no degradation of the methyl orange dye under the
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same conditions. The highest degradation efficiency was obtained for 8% Al-doped
ZnO thin films under visible light irradiation
Description
A thesis submitted in fulfilment of the requirements for the Degree of Master of Science in Chemistry
Keywords
Aqueous spray-coating method, Thin films, ZnO, Precursor solutions, Hexagonal wurtzite phase, Photocatalytic activity, Namibia, University of Namibia