This paper addresses the effect of Mn (2%, fixed) and Co (2, 4, and 6%, varied) substitution on the structural, optical, dielectric and magnetic responses of ZnO nanoparticles synthesized by the co-precipitation chemical route. The X-ray diffraction analysis confirms the hexagonal wurtzite structure of ZnO. The incorporation of co-doping in the ZnO host, indicated by peak shifting in the XRD patterns, enhanced the crystallite size of the Mn/Co dual-doped ZnO nanoparticles. The FTIR spectra show a characteristic peak around 875 cm⁻¹ assigned to Zn–O stretching, this validates the formation of the wurtzite structure of ZnO. Raman spectroscopy reveals the characteristic band of the wurtzite structure of ZnO nanoparticles along with coupled vibration modes of Mn/Co with the donor defect states in the doped samples. Enhanced optical absorption in the visible region and a significant red-shift in the absorption band edge were found due to doping. The optical band gap is found to decrease from 3.45 eV to 3.15 eV when Co doping increases up to 6%. The dielectric properties, strongly frequency-dependent, decrease with increasing Co doping while the electrical conductivity increases. Ferromagnetism is observed in all the doped samples, and its origin is attributed to an increase in oxygen vacancies which form bound magnetic polarons. It can be inferred that the doping of Mn and Co can be an effective tool to tune the physical properties of ZnO nanoparticles for potential spintronics and high-frequency applications.

In the present study, pure, Co, Gd, and Co/Gd di-doped ZnO nanoparticles were synthesized via the co-precipitation synthesis route. The prepared samples were characterized through different techniques such as the X-ray diffraction method (XRD), scanning electron microscopy (SEM), UV-Vis spectroscopy, photoluminescence (PL)spectroscopy, and an impedance analyzer and vibrating sample magnetometer (VSM). The XRD pattern shows ZnO’s wurtzite hexagonal crystal structure; moreover, the shifting of characteristic peaks toward the lower angle indicates the inclusion of Co and Co/Gd in the ZnO host lattice. SEM micrographs show various morphologies such as rods, the agglomeration of particles, and spherical nanoparticles. The UV-Vis spectroscopy reveals that the absorption increased in the visible region and there was a substantial redshift for the doped samples. The bandgap decreased from 3.34 to 3.18 eV for the doped samples. The PL spectra show near-edge and inter-band transitions; the origin of inter-band transitions is attributed to the defect states present within the bands. The dielectric constant is strongly frequency dependent and decreases with Co and Co/Gd doping, while the electrical conductivity increases. A VSM study indicates that pure ZnO is diamagnetic, while the Co and Co/Gd doped ZnO nanoparticles showed ferromagnetic behavior. Under UV-visible light irradiation, the Co/Gd-ZnO nanoparticles showed higher photocatalytic activity than the ZnO nanoparticles. The enhanced photocatalytic activity may be attributed to a decreased bandgap with doping.

Total and partial DOS of non-degenerate d_eg and d_t2g states of (a) ScMnGe and (b) ScFeGe Heusler alloys.

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.

Supercapacitors exhibit limitations such as low energy density, high self-discharge rates, and degradation of electrochemical performance over extended cycling. This study presents the development of a high-performance asymmetric supercapacitor by synthesizing novel ZnO-VSe₂ nanocomposites through wet-chemical methods, aiming to enhance capacity, energy density, and durability. The capacitive performance of these materials was systematically evaluated in an aqueous alkaline electrolyte (KOH) at a concentration of 2 M. ZnO-VSe₂ composite demonstrates superior electrochemical energy storage capabilities, achieving a specific capacitance of 898 F/g and reducing overall resistance, enabling rapid electrolyte diffusion. These optimized electrochemical characteristics underscore the potential of ZnO-VSe₂ for energy storage applications. Specifically, the ZnO-VSe₂||AC asymmetric supercapacitor achieved an impressive capacitance of 260 F/g, an energy density of 71 Wh/kg, and a maximum power output of 6948 W/kg, along with a remarkable stability of 89.1% at a current density of 10 A/g over 5000 cycles. The proposed methodology offers a cost-effective and promising approach for evolving high-energy hybrid supercapacitors for energy storage applications.