Arumugam Sivasamy

In recent years, the demand for rare earth elements has surged due to their unique characteristics and diverse applications. This investigation focuses on utilizing the rare earth element dysprosium oxide (Dy₂O₃) for the photocatalytic oxidation of model pollutants under solar light irradiation. A novel RGO-Dy₂O₃ nanocomposite photocatalyst was developed using a solvothermal approach, Dy₂O₃ nanorods uniformly deposited onto reduced graphene oxide (RGO) nanosheets. Comprehensive characterization techniques, including Brunner-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), Raman spectroscopy, high resolution – transmittance electron microscopy (HR-TEM), field emission–electron scanning microscopy (FE-SEM), atomic force microscopy (AFM), electron paramagnetic resonance spectroscopy (EPR), photoluminescence spectroscopy (PL), and electrochemical impedance spectroscopy EIS techniques. The UV–visible diffusive reflectance spectroscopy (UV–Vis-DRS) studies revealed a band gap energy of 3.18 eV and a specific surface area of 114 m²/g for the fabricated RGO-Dy₂O₃ nanocomposite. The RGO-Dy₂O₃ nanocomposite demonstrated a high photocatalytic degradation efficiency of 98.1% at neutral pH for methylene blue (MB) dye for the dye concentration of 10 ppm. The remarkable photocatalytic performance was achieved within 60 min under solar light irradiation. Reusability tests demonstrated stability, maintaining over 90% photocatalytic efficiency after three cycles. The EPR spectra and quenching experiments confirmed that photogenerated hydroxyl radicals significantly influence the photodegradation processes. The RGO-Dy₂O₃ nanocomposite photocatalyst, with its green, easy preparation process and recycling capabilities, presents an ideal choice for various applications. It offers a viable alternative for the photocatalytic degradation of organic dyes in real wastewater, contributing to sustainable environmental remediation.

Semiconductor photocatalysis is the most efficient advanced oxidation processes for wastewater treatment. A new carbon-based photocatalyst bismuth oxide/multi-walled carbon nanotube (Bi₂O₃/MWCNT) nanocomposite has a considerable impact on improving photocatalytic performance. Bi₂O₃/MWCNTs (BMC) nanocomposite was prepared through the hydrothermal processing with 2.5, 5, 7.5 and 10 wt% of MWCNTs. The prepared photocatalysts have been thoroughly examined by various techniques. The X-ray diffraction confirmed the prepared photocatalyst as α-Bi₂O₃ with high crystallinity. The band gap of Bi₂O₃ and BMC 7.5 nanocomposite was found to be 2.41 and 1.94 eV. The prepared photocatalyst revealed smooth and porous merged flower-like structure with respect to the addition of MWCNTs. The model pollutant chromium(VI) (Cr(VI)) has been used to check the reduction efficiency of the prepared photocatalyst under solar irradiation. It was found that BMC 7.5 nanocomposite showed enhanced photocatalytic metal ion reduction (87.48%) compared to pristine Bi₂O₃ (69.29%). The preliminary photocatalytic Cr(VI) ion reduction experiments were carried to determine the photoreduction efficiency of pristine bismuth oxide and bismuth MWCNT nanocomposite. The kinetic study on Cr(VI) ion reduction obeyed pseudo-first-order rate kinetics for both the prepared photocatalysts. The efficiency of the photocatalysts was further analysed by reusing the same up to 3 cycles without loss of the efficacy.

Developing and implementing visible light active organic–inorganic hybrid semiconductor nanomaterials with enhanced photocatalytic properties find newer environmental and energy treatment capabilities. Here, we are reporting polymeric g-C₃N₄ layers coated with different propositions of erbium oxide nanoparticles, characterized using XPS, UV–Vis-DRS, FT-IR, HR-TEM, FE-SEM, elemental mapping, XRD and surface area techniques and its photocatalytic activities were evaluated under visible light irradiations. The hybrid nanocomposite materials possess better crystalline nature and erbium oxide particles were on the surface of polymeric g-C₃N₄. The surface area and bandgap energy of the polymeric g-C₃N₄-erbium oxide (5 wt%) nanohybrid composite were 99.9 m²/g and 2.52 eV. The photocatalytic activities as prepared nanohybrid composites were assessed for the oxidation of orange G dye molecules in the presence of visible light and were highly active in a broader range of pH with the presence of various inorganic anions. The rate of photocatalytic oxidation of dye molecules varied from 4.79 × 10⁻⁴ to 1.77 × 10⁻⁴ min⁻¹ for the initial concentration of 5 to 20 ppm and retained its activities above 95% up to three cycles of reusability. Hence, the organic–inorganic novel catalytic nanohybrid composite may find more comprehensive applications in the area of environmental and energy applications.

To study their physicochemical and antimicrobial properties, zinc oxide nanoparticles were synthesized using a simple chemical route and 4-dimethylaminobenzaldehyde (4DB) as an organic additive. ZnO nanoparticles were characterized with XRD analysis, which confirmed the presence of a hexagonal wurtzite structure with different crystalline sizes. The SEM morphology of the synthesized nanoparticles confirmed the presence of nanorods in both modifications of ZnO nanoparticles. EDS analysis proved the chemical composition of the synthesized samples via different chemical approaches. In addition, the optical absorption results indicated that the use of 4DB increased the band gap energy of the synthesized nanoparticles. The synthesized Zn₈O₈ and Zn₈O₈:4DB clusters were subjected to HOMO–LUMO analysis, and their ionization energy (I), electron affinity (A), global hardness (η), chemical potential (σ), global electrophilicity index (ω), dipole moment (μ), polarizability (α_tot), first-order hyperpolarizability (β_tot), and other thermodynamic properties were determined. Furthermore, the antimicrobial properties of the ZnO nanoparticles were studied against G+ (S. aureus and B. subtilis) and G− (K. pneumoniae and E. coli) bacteria in a nutrient agar according to guidelines of the Clinical and Laboratory Standards Institute (CLSI).