Search

This paper presents a comprehensive investigation of the synthesis and characterization of Zn1−xCoxO (0 ≤ x ≤ 0.05) nanopowders using a chemical co-precipitation approach. The structural, morphological, and vibrational properties of the resulting ZnO nanostructures were assessed through X-ray diffraction, scanning electronic microscopy, and Raman spectroscopy to examine the influence of cobalt doping. Remarkably, a notable congruence between the experimental results and the density functional theory (DFT) calculations for the Co-doped ZnO system was achieved. Structural analysis revealed well-crystallized hexagonal wurtzite structures across all samples. The SEM images demonstrated the formation of spherical nanoparticles in all the samples. The vibrational properties confirmed the formation of a hexagonal wurtzite structure, with an additional Raman peak corresponding to the F2g vibrational mode characteristic of the secondary phase of ZnCo2O4 observed at a 5% cobalt doping concentration. Furthermore, a theoretical examination of cobalt doping's impact on the elastic properties of ZnO demonstrated enhanced mechanical behavior, which improves stability, recyclability, and photocatalytic activity. The photocatalytic study of the synthesized compositions for methylene blue (MB) dye degradation over 100 min of UV light irradiation demonstrated that Co doping significantly improves photocatalytic degradation. The material's prolonged lifetime, reduced rate of photogenerated charge carrier recombination, and increased surface area were identified as pivotal factors accelerating the degradation process. Notably, the photocatalyst with a Zn0.99Co0.01O composition exhibited exceptional efficiency compared to that reported in the literature. It demonstrated high removal activity, achieving an efficiency of about 97% in a shorter degradation time. This study underscores the structural and photocatalytic advancements in the ZnO system, particularly at lower cobalt doping concentrations (1%). The developed photocatalyst exhibits promise for environmental applications owing to its superior photocatalytic performance. [ABSTRACT FROM AUTHOR]

This study offers important insights into the impact of incorporating cobalt on a range of characteristics of ZnO nanoparticles. Undoped ZnO and doped Zn1−xCoxO (x = 0.01 and 0.05) were effectively elaborated by the co-precipitation method. It establishes for the first time a full description of physical properties from experimental and theoretical points of view for Co-doped ZnO nanoparticles. The theoretical results studied by means of the Density Functional Theory are correlated with the experimental findings obtained using various techniques. Besides, the structural analysis revealed the formation of the hexagonal wurtzite structure of all the powdered samples with the appearance of the secondary phase ZnCo2O4 for the Zn0.95Co0.05O composition. An increasing trend of the average crystallite size from 26.49 to 53.93 nm was obtained under Co doping effect. Concerning the optical characterization, the band gap energy was found to decline with increasing Co doping concentration. Furthermore, the dielectric analysis was performed at different temperatures in the range frequency 40–107 Hz. An enhancement of the dielectric constant was observed with the addition of Co into ZnO host matrix. Overall, this novel contribution improves the performances of such structures that make them potential candidates for dielectric applications. [ABSTRACT FROM AUTHOR]

Anatase titanium dioxide is one of the most promising energy materials. However, it suffers from low electrical conductivity due to its wide band gap that corresponds to only UV radiation absorption. Regarding these challenges, Zn doping is considered as an attractive solution to enhance its performance in photocatalysis, solar cells, and transparent conducting oxide films. Thus, with this motive, we have investigated Zn-doped titanium dioxide (Zn:TiO2) by ab initio calculations within the density functional theory (DFT). The theoretical RAMAN spectra are calculated using the Becke three-parameter Lee–Yang–Parr (B3LYP) functional through the implementation algorithm of the CRYSTAL17 code. Results agree well with the experimental data, and the observed modes reveal the anatase phase of TiO2. The increase in Zn content leads to a band gap reduction, and the optical properties are strongly enhanced in TiO2: Zn (4 and 6%), which extend light absorption edge to the visible light range and promote good photocatalytic activity. Correlations between DFT calculations and electrical response are also established. Accordingly, the values of the capacitance as well as resistance are extracted from the equivalent circuit model of the Nyquist plots. The resistance decreases with increasing the Zn content which results in higher leakage current under constant voltage stress. The mechanical response is also investigated to verify the stability of the (Zn:TiO2) films. In the tetragonal structure, pure TiO2 has a large bulk modulus of 178 GPa and a small shear modulus of 71.8 GPa. However, with increasing the Zn concentration, the stiffness and brittleness of the films decrease, while the anisotropic character increases. This could be very promising for energy-related applications. [ABSTRACT FROM AUTHOR]