Search

Abstract The removal of toxic dye pigments from the environment is of utmost importance since even trace amounts of these pollutants can lead to harmful impacts on ecosystems. Heterogeneous photocatalysis is a potential technique for eliminating microbiological, inorganic, and organic pollutants from wastewater. Here, we report the band gap alteration of ZnO by making its composites with CuSe to enhance photocatalytic activity. The purpose is to develop metal oxide nanocomposites (ZnO/CuSe) as an effective and efficient material for the photodegradation of methyl blue. The photocatalysts, ZnO nanorods, CuSe, and ZnO/CuSe nanocomposites of different weight ratios were synthesized by the simple and cost-effective technique of precipitation. UV–Vis spectra verified that the ZnO/CuSe photocatalyst improved absorption in the visible region. The optical bandgap of ZnO/CuSe nanocomposites reduced from 3.37 to 2.68 eV when CuSe concentration increased from 10 to 50%. ZnO/CuSe composites demonstrated better photocatalytic activity than ZnO when exposed to UV–visible light. The pure ZnO nanorods could absorb UV light and the nanocomposites could absorb visible light only; this was attributed to the transfer of excited high-energy electrons from ZnO to CuSe.

The authors report a scheme for enhancing the photodegradation properties of TiO2 nanoparticles (TiO2 NPs) by controlling their structural phases through cations doping (cobalt and Sulfur). Cobalt-sulfur co-doped TiO2 nanoparticles were synthesized via a hydrothermal process, with sulfur content varying at levels of 0.69, 1.37, and 2.06 atomic percent (at. %), while maintaining a constant cobalt content of 0.2 at. %. Our finding shows that the methyl blue dye loaded with pure TiO2 degraded marginally in 120 min (⁓ 10.5%) while in the presence of an optimally doped sample (Co: 0.2 at. %, S 2.06 at. %), it degraded almost 93% for the same duration. The study explores the underlying physical mechanisms that contribute to the varying levels of photoactivity, and these mechanisms are found to be influenced by the valency of the doping agents. The findings of this study demonstrate that precise control over the formation of the anatase phase through doping enables the production of a remarkably efficient TiO2-based photocatalyst. Our results indicate great prospects in enhancing TiO2-based photocatalyst development chemically, a suitable approach for large-scale nanoparticle production for industrial applications.

Abstract This study explored the structural, optical, and dielectric properties of Pure and Mn+2 doped ZnO nano-particles (Zn1−xMnxO) with x ≥ 20%, synthesized by co-precipitation method followed by annealing at 4500C. Different characterization techniques were conducted to characterize the as-prepared nano-particles. X-ray Diffraction analysis of the pure and Mn+2 doped presented a hexagonal wurtzite structure and a decreased crystallite size with increasing doping concentration. Morphological analysis from SEM revealed finely dispersed spherical nanoparticles with particle size of 40–50 nm. Compositional analysis from EDX confirmed the incorporation of Mn+2ions in ZnO structure. The Results of UV spectroscopy showed that changing the doping concentration affects the band gap, and a red shift is observed as the doping concentration is increased. The band gap changes from 3.3 to 2.75 eV. Dielectric measurements exhibited decrease in the relative permittivity, dielectric loss factor and ac conductivity by increasing Mn concentration.

This research pursued the effect of various calcination temperatures (300–1000 °C) on developing structural phases and the optical, dielectric, and photodegradation characteristics of cobalt-doped titanium dioxide nanoparticles (TiO2 NPs). The prepared NPs were characterized using X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX), Fourier transform infrared (FTIR) spectroscopy analysis, ultraviolet–visible light (UV–VIS) spectroscopy, and photodegradation of methylene blue in the presence of visible light. XRD analysis revealed the formation of a tetragonal anatase phase for the samples calcined at 300–600 °C, while the Co-doped samples calcined at 800 °C and 1000 °C displayed a tetragonal rutile phase. The optical band gap analysis indicated that doping in the host matrix produced lower band gap energy for all the prepared samples. Dielectric measurements showed that the rutile phase heated at 800 °C had a larger dielectric constant and dielectric loss than the un-doped TiO2 and the other cobalt-doped samples. Finally, the anatase Co-doped TiO2 exhibited a maximum MB degradation of 93 % in 90 min compared to un-doped TiO2, which only degraded 14 % and rutile-TiO2 NPs (62 % degradation). The underlying mechanism responsible for the diverse photodegradation performance displayed by the anatase and rutile phases of TiO2 NPs is discussed. Overall, these results demonstrate that cobalt doping and the crystalline phase of TiO2 NPs are vital parameters involved in optimizing the photocatalytic activity of TiO2.

The toxic dye pigments, even in small quantities, can damage ecosystems. Removing organic, inorganic, and microbiological contaminants from wastewater via heterogeneous photocatalysis is a promising method. Herein, we report the band structure tuning of ZnO/CuO nanocomposites to enhance photocatalytic activity. The nanocomposites were synthesized by a chemical approach using step-wise implantation of p-type semiconductor CuO to n-type semiconductor ZnO. Various characterization techniques such as X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX) and UV spectroscopy were used to investigate the crystal structure, surface morphology, elemental composition and optical properties of the synthesized samples. As the CuO content increased from 10% to 50% in ZnO/CuO nanocomposites, the optical bandgap decreased from 3.36 to 2.14 eV. The photocatalytic activity of the samples was evaluated against the degradation of methylene blue (MB) under visible irradiation. Our study demonstrates a novel p–n junction oxide photocatalyst based on wt. 10% CuO/ZnO with superior photocatalytic activity. Effectively 66.6% increase in degradation rate was achieved for wt. 10% CuO/ZnO nanocomposite compared to pure ZnO nanoparticles.

La1-xCaxMnO3 nanoparticles (x = 0.1, 0.2, 0.3) (LCMO NPs) were synthesized using the coprecipitation method. The prepared samples were investigated using x-ray diffraction (XRD), which confirmed the single-phase structure. The nanoparticle’s crystallite size was determined using Debye–Scherrer’s formula. Scanning electron microscopy showed that the size of the nanoparticles was between 33 nm and 55 nm. Energy-dispersive x-ray spectroscopy (EDX) was used to determine the elemental composition of samples. The four-probe method was used to measure the temperature-dependent electrical resistivity. Magnetic properties, such as hysteresis loop, magnetoresistance, and magnetization versus temperature, were measured using a vibrating sample magnetometer. The study of magnetization versus applied magnetic field M(H) showed that, at 77 K, all the loops exhibit ferromagnetism. DC magnetization versus temperature at a 70-Oe-applied field for all samples showed a paramagnetic-ferromagnetic phase transition. A decrease in Curie temperature Tc after increasing the concentration of x was observed. The real and imaginary parts of temperature-dependent ac magnetic susceptibility were measured and revealed a transition from the ferromagnetic to the paramagnetic phase at a particular temperature Tc, with DC magnetization behavior.