ZnO/ZnAl2O4nanocomposite films were synthesised by ultrasonic spray pyrolysis (USP) by extracting Al2O(SO4)2oxide with zinc chloride hydrate in deionised water. The sample was then subjected to heat treatment at 650°C and 700°C for 1 h, which led to the formation of the spinel oxide (ZnAl2O4) and wurtzite (ZnO) phases. Al2(SO4)3·18H2O salt was transformed into aluminum oxide sulfate Al2O(SO4)2, which is an intermediary decomposition product, by calcination at 795°C for 3 h. The structures of the synthesised ZnO/ZnAl2O4films were confirmed by XRD, FTIR, and X-ray photoelectron spectroscopy (XPS). XPS spectra of the major Zn, Al, and O photoelectron lines and the major X-ray induced Zn LMM Auger lines for ZnO/ZnAl2O4are presented.
A complex ZnO/ZnAl2O4 heterostructures thin films on glass and Si (111) substrates have been successively obtained by a soft ultrasonic spray pyrolysis (USP) method deposition using the Zn/Al molar ratios concentrations of 0.07/0.13 and 0.1/0.1, respectively. According to (XRD) an ordered zinc oxide (ZnO) and zinc aluminate (ZnAl2O4) structures deposited onto glass from the air annealing at 500 °C during 2 hours was observed and confirmed by the (EDX), (FTIR) and Raman spectroscopy techniques. The estimated crystallites size and stress values of ZnO and ZnAl2O4 in the ZnO/ZnAl2O4/glass film were 19 nm/0.469 GPa and 11 nm/-0.292 GPa, respectively. The lower Zn/Al molar ratio around 0.035/0.06 produced only ZnO as a single phase, suggesting the Al insufficient quantity. The Si (100) substrate with 0.07 Zn molarity conducted to the Zn2SiO4/ZnO/ZnAl2O4 composite. The Raman integrated intensity bands of ZnO and ZnAl2O4 increases with increasing Zn to Al molar ratio (0.1/0.1 comparatively to 0.07/0.13). The ZnO&ZnAl2O4 crystallinity enhances as Zn molarity increases. The ZnO films in the composites grow with (002) texture. The TC(hkl) value indicated that ZnAl2O4 in the ZnO/ZnAl2O4/glass layer is polycrystalline preferentially oriented along the (311) plane. Spinel ZnAl2O4 oxide onto Si (111) substrate grown according to the (220) orientation. Crystallites are larger in ZnO/ZnAl2O4/Si than in ZnO/ZnAl2O4/glass. The ZnO/ZnAl2O4 film onto glass substrate is transparent in the visible and near infrared regions and sensitive to UV absorption, as characterized by UV-Vis spectroscopy. The ZnO and ZnAl2O4Egvalues in the ZnO/ZnAl2O4/glass composite were 3.25 and 3.88 eV, respectively.
ZnO nanoparticles were successfully produced via a simple low cost hydrothermal method using different metal precursors. Zn (CH3COO)2), (Zn (NO3)2) and (ZnCl2) were the source materials. The obtained nanoparticles were investigated by means XRD, SEM and DRS. The XRD exhibited the high crystallinity of the pure ZnO phase with hexagonal wurtzite crystalline structure for all simples excepted for ZnO synthetized from ZnCl2 precursor. The crystallite sizes was estimated in the range of 20-37 nm. The precursor type do not affect the Eg of the nanoparticles. The bandgaps energies were between 3.21-3.22 eV. The type of precursor affect the particles morphology. SEM images revealed different morphologies. The photocatalytic activity of the synthetized ZnO NPs in comparison with that of commercial powder for the methylene blue (MB) degradation under UV irradiation, showed the appropriate activity of nanostructures obtained by Zn (NO3)2 and Zn (CH3COO)2 precursors. The first-order kinetic constant over ZnO from Zn (NO3)2 was 1.9, 3.7 and 1.5 times of ZnO commercial powder, ZnO from ZnCl2 and Zn (CH3COO)2, respectively. The ZnO NPs from Zn (NO3)2 and Zn (CH3COO)2 precursors have the best photocatalytic degradation performance with a degradation rate of 99.3% and 96.4%, respectively. The higher photocatalytic performance was probably due to the larger crystallinity, purity phase and specific morphologies than smaller particle size effect. Thus, the synthetized ZnO nanoparticles by the soft hydrothermal process are a promising candidate for the photocatalytic purposes of dyes from waters.
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