Thottipalayam Subramaniyam Senthil

This study investigates the influence of calcium doping on the structural, optical, and photocatalytic properties of bismuth ferrite nanoparticles. Pure and calcium-doped BiFeO₃ nanoparticles (Ca@BFO) with doping concentrations of 0.05, 0.075, and 0.1 M were synthesized via a sol–gel method. X-ray diffraction analysis confirmed structural modifications and crystallite size reduction upon doping. Raman spectroscopy indicated enhanced peak intensities for Ca@BFO samples, suggesting improved structural ordering. UV–vis spectroscopy demonstrated a reduction in the wide bandgap to 2.24 eV for the 0.1 M Ca-doped BFO, leading to enhanced visible-light absorption. Photocatalytic activity was assessed by the degradation of methylene blue under different pH conditions, with the best performance observed at pH 8 for the 0.1 M Ca-doped BFO sample. Stability and reusability studies showed minimal activity loss over multiple cycles. These findings highlight the potential of Ca@BFO nanoparticles for efficient photocatalysis and environmental remediation applications.

Photocatalysts based on semiconducting chalcogenides due to their adaptable physio-chemical characteristics are attracting attention. In this work, Bi-doped PbS (henceforth PbS:Bi) was prepared using a straightforward chemical precipitation approach, and the influence of γ-irradiation on PbS's photocatalytic ability was investigated. Synthesized samples were confirmed structurally and chemically. Pb_(1-x)Bi_xS (x = 0, 0.005, 0.01, 0.02) samples that were exposed to gamma rays showed fine-tuning of the optical bandgap for better photocatalytic action beneath visible light. The photocatalytic degradation rate of the irradiated Pb_0.995Bi_0.005S sample was found to be 1.16 times above that of pure PbS. This is due to the occupancy of Bi³⁺ ions at surface lattice sites as a result of their lower concentration in PbS, which effectively increases interface electron transport and the annealing impact of gamma irradiation. Scavenger tests show that holes are active species responsible for deterioration of the methylene blue. The irradiated PbS:Bi demonstrated high stability after being used repeatedly for photocatalytic degradation.