In this research, a facile co-precipitation method was used to synthesize pure and Mg-doped ZnO nanoparticles (NPs). The structure, morphology, chemical composition, and optical and antibacterial activity of the synthesized nanoparticles (NPs) were studied with respect to pure and Mg-doped ZnO concentrations (0–7.5 molar (M) %). X-ray diffraction pattern confirmed the presence of crystalline, hexagonal wurtzite phase of ZnO. Scanning electron microscope (SEM) images revealed that pure and Mg-doped ZnO NPs were in the nanoscale regime with hexagonal crystalline morphology around 30–110 nm. Optical characterization of the sample revealed that the band gap energy (E_g) decreased from 3.36 to 3.04 eV with an increase in Mg²⁺ doping concentration. Optical absorption spectrum of ZnO redshifted as the Mg concentration varied from 2.5 to 7.5 M. Photoluminescence (PL) spectra showed UV emission peak around 400 nm. Enhanced visible emission between 430 and 600 nm with Mg²⁺ doping indicated the defect density in ZnO by occupying Zn²⁺ vacancies with Mg²⁺ ions. Photocatalytic studies revealed that 7.5% Mg-doped ZnO NPs exhibited maximum degradation (78%) for Rhodamine B (RhB) dye under UV-Vis irradiation. Antibacterial studies were conducted using Gram-positive and Gram-negative bacteria. The results demonstrated that doping with Mg ions inside the ZnO matrix had enhanced the antibacterial activity against all types of bacteria and its performance was improved with successive increment in Mg ion concentration inside ZnO NPs.

Photocatalytic degradation is essential for the successful removal of organic contaminants from wastewater, which is important for ecological and environmental safety. The advanced oxidation process of photocatalysis has become a hot topic in recent years for the remediation of water. Cadmium sulphide (CdS) nanostructures doped with Titanium oxide (CdS/TiO₂) nanocomposites has manufactured under ambient conditions using a simple and modified Chemical Precipitation technique. The nanocomposites crystal structure, thermal stability, recombination of photo-generated charge carriers, bandgap, surface morphology, particle size, molar ratio, and charge transfer properties are determined. The production of nanocomposites (CdS-TiO₂) and their efficient photocatalytic capabilities are observed. The goal of the experiment is to improve the photocatalytic efficiency of TiO₂ in the visible region by doping CdS nanocomposites. The results showed that as-prepared CdS-TiO₂ nanocomposites has exhibited the highest photocatalytic activity in the process of photocatalytic degradation of AB-29 dye, and its degradation efficiency is 84%. After 1 h 30 min of visible light irradiation, while CdS and TiO₂ showed only 68% and 09%, respectively. The observed decolorization rate of AB-29 is also higher in the case of CdS-TiO₂ photocatalyst ~ 5.8 × 10⁻⁴mol L⁻¹ min⁻¹) as compared to the reported decolorization rate of CdS ~ 4.5 × 10⁻⁴mol L⁻¹ min⁻¹ and TiO₂ ~ 0.67 × 10⁻⁴mol L⁻¹ min⁻¹. This increased photocatalytic effectiveness of CdS-TiO₂ has been accomplished by reduced charge carrier recombination as a result of improved charge separation and extension of TiO₂ in response to visible light.

Cerium oxide (CeO₂) nanoparticles were prepared by the precipitation method. The average crystallite size of cerium oxide nanoparticles was calculated from the X-ray diffraction (XRD) pattern and found to be 11 nm. The FT-IR spectrum clearly indicated the strong presence of cerium oxide nanoparticles. Raman spectrum confirmed the cubic nature of the cerium oxide nanoparticles. The Scanning Electron Microscopy (SEM) analysis showed that the nanoparticles agglomerated forming spherical-shaped particles. The Transmission Electron Microscopic (TEM) analysis confirmed the prepared cerium oxide nanoparticles with the particle size being found to be 16 nm. The optical absorption spectrum showed a blue shift by the cerium oxide nanoparticles due to the quantum confinement effect. The dielectric properties of cerium oxide nanoparticles were studied for different frequencies at different temperatures. The dielectric constant and the dielectric loss of the cerium oxide nanoparticles decreased with increase in frequency. The AC electrical conductivity study revealed that the conduction depended on both the frequency and the temperature.

Nickel ferrite (NiFe₂O₄) nanoparticles were synthesized using co-precipitation method. The X-ray diffraction (XRD) pattern was used to determine the structure of NiFe₂O₄ nanoparticles. The presence of NiFe₂O₄ nanoparticles was confirmed by the FT-IR spectrum. The details of the surface morphology of NiFe₂O₄ nanoparticles were obtained by Scanning Electron Microscopic analysis. The particle size of the NiFe₂O₄ nanoparticles could be determined by means of Transmission Electron Microscopy. This work aimed at the investigation of the dielectric properties such as the dielectric loss and the dielectric constant of NiFe₂O₄ nanoparticles at varied frequencies and temperatures. In addition, the magnetic properties of the NiFe₂O₄ nanoparticles were studied.