Schindra Kumar Ray

Ag-BaMoO4: Er3+/Yb3+ photocatalyst for antibacterial application

Silver loaded and Er3+/Yb3+ doped BaMoO4 octahedron microcrystals were fabricated by microwave hydrothermal process. The synthesized samples were characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray spectroscopy (EDS), and Ultraviolet-visible diffuse reflection spectroscopy (UV-Vis DRS). The antibacterial application of samples were investigated by visible light irradiation and disk-diffusion method towards representative Gram-negative pathogen (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive pathogen (methicillin resistant Staphylococcus aureus). The complete inactivation of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were observed by Ag-BaMoO4: Er3+/Yb3+ photocatalyst within 1h, 4h, and 5h, respectively, under visible light irradiation. The high killing percentage and superior zone of inhibition revealed the excellent antibacterial performance. The FESEM images were used to visualize the morphology with the extent of damage in the phospholipid layer present in the cell membrane of bacteria. The synergistic effect of loaded silver particles and doped Er3+/Yb3+ ions in BaMoO4 contributed for efficient antibacterial performance in visible light as well as in the dark. The excellent antibacterial performance of Ag-BaMoO4: Er3+/Yb3+ photocatalyst makes the material suitable for smart weapon for multidrug-resistant microorganisms and disinfectants in biomedical application.

Insight Into Malachite Green Degradation, Mechanism and Pathways by Morphology-Tuned α-NiMoO4 Photocatalyst

The microwave hydrothermal process was used for the synthesis of various morphologies of α‐NiMoO4 by simply adjusting the pH during experimental conditions. The effect of morphology/size on the photocatalytic performances for degradation of malachite green (MG) has been investigated under UV‐Vis/visible light irradiation. Nanorod morphology has strong tendency to degrade (88.18%) the MG as compared to spherical quantum‐sized (57.65%) and layered square microsheet (37.98%) under UV‐Vis irradiation in 180 min. The active species trapping experiment revealed that active species (OH•, O2•− and h+) play a crucial role for MG degradation. The high BET surface area, greater amount of oxygen defect and efficient separation of electron–hole pair are responsible for MG degradation. About seventeen types of organic fragments of MG were confirmed by high resolution‐quadruple time of flight electrospray ionization mass spectroscopy (HR‐QTOF ESI/MS) technique on the basis of retention time and molecular masses. Degradation mechanism and pathways were proposed that follow the demethylation, nitration, decarboxylation, hydrolysis, decarboxylation and oxidation reaction. The reduction of total organic carbon revealed the mineralization of MG during photocatalytic degradation process. Therefore, this article represents the investigation of MG degradation by various morphology of α‐NiMoO4 and detailed degradation mechanism and pathways.

Understanding Mechanism of Photocatalytic Microbial Decontamination of Environmental Wastewater

Several photocatalytic nanoparticles are synthesized and studied for potential application for the degradation of organic and biological wastes. Although these materials degrade organic compounds by advance oxidation process, the exact mechanisms of microbial decontamination remains partially known. Understanding the real mechanisms of these materials for microbial cell death and growth inhibition helps to fabricate more efficient semiconductor photocatalyst for large-scale decontamination of environmental wastewater or industries and hospitals/biomedical labs generating highly pathogenic bacteria and toxic molecules containing liquid waste by designing a reactor. Recent studies on microbial decontamination by photocatalytic nanoparticles and their possible mechanisms of action is highlighted with examples in this mini review.