Krishnasamy Sankaranarayanan

Silver phosphate (Ag₃PO₄) exhibits excellent photocatalytic performance but has limitation in its stability and reusability. To overcome the issue of reusability, composites of silver phosphate nanostructures are tailored. This paper elucidates the photocatalytic study of silver phosphate-anchored hydroxyapatite (HA) (Ca₁₀(PO₄)₆(OH)₂) on the degradation of commercial textile dye, Sunfix Red (SR) S3B 150 by changing the experimental parameters such as catalyst concentration, dye concentration, and pH of the dye solution under the sunlight. Silver phosphate-anchored HA (HA_Ag₃PO₄(x)) was prepared via a two-step process. HA was synthesized by a simple wet chemical precipitation and silver phosphate-anchored HA (HA_Ag₃PO₄(x)) via in situ ion-exchange method. The synthesized photocatalysts were subjected to characterization studies such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), ultravioletvisible spectroscopy, and X-ray photoelectron spectroscopy (XPS). All the synthesized composites exhibited the bandgap of 2.34eV and degraded SR in 45min with the rate constant 0.07168min⁻¹ under sunlight. The trapping tests for radicals were done to study the role of free radicals in the degradation of the dye, SR, and the possible degradation mechanism was proposed. The postphotocatalytic analysis of XRD showed that the structure of Ag₃PO₄ remained intact declaring its structural stability. It was observed that the concentration of AgNO₃ precursor influenced the number of nucleation over the surface of HA and the particle size of Ag₃PO₄. The applicability of the synthesized material was extended to other organic dyes such as Sunzol Black (SB) DN conc., methylene blue (MB), and rhodamine B (RhB) by the prepared composite and the findings were presented.

A major problem in world health care is the development of antibiotic resistance in bacteria. In light of this, pure and calcium-doped zinc tin oxide (ZTO) nanoparticles, Zn₂SnO₄ (S₁), Zn₂Sn_0.7Ca_0.3O₄ (S₂), Zn₂Sn_0.5Ca_0.5O₄ (S₃), and Zn₂Sn_0.3Ca_0.7O₄ (S₄), were synthesized via simple and cost effective microwave assisted method. The doping effect on antibacterial activity was studied in detail. The XRD spectrum revealed that all the deposited samples exhibited a spinel cubic structure. A decrease in crystallite size, an increase in strain and dislocation density was observed with an increase in Ca concentration. FESEM images exhibited an irregular and non-homogeneous nature with crystalline morphology having a physical dimension of nm size. EDAX confirmed the purity of deposited samples. We used the agar well diffusion technique to study the antibacterial activity of Gram-positive and Gram-negative bacteria. The doping of the ZTO matrix with Ca ions increased its antibacterial performance by 99% against Klebsiella pneumoniae bacteria, and its effectiveness was enhanced with increasing Ca ion concentration inside the Zn₂SnO₄ nanoparticles.