R. Ragu

Pure and nickel (Ni) doped cobalt oxide nanoparticles were employed by the co-precipitation method to present the structural, optical, and photocatalytic characteristics of Ni_xCo_3-xO₄ nanoparticles (x = 0, 0.05, 0.1, and 0.3) for organic pollutant photodegradation. X-ray diffraction (XRD) was employed on Ni_xCo_3-xO₄ samples with particle sizes ranging from 14 to 22 nm, confirming the occurrence of cubic phase. In addition, particle size was calculated by Debye Scherrer, Williamson-Hall (W-H) and Halder methods, respectively. The Fourier transform infrared (FTIR) analyses of all samples characterised the inherent lattice vibrations of spinel structures octahedral and tetrahedral sites, respectively. FESEM image depicts irregular-shaped clusters and EDX confirmed the presence of Ni, Co and O elements. The mesoporous nature of the pores and high BET specific surface area indicated the presence of several active sites, proving their viability as photocatalysts. UV-Vis spectrophotometer was utilised to measure the optical properties, which included recording absorption spectra and computing optical parameters. The photocatalytic activities of the pure Co₃O₄ and Ni_xCo_3-xO₄ photocatalysts were studied by the degradation of a series of four dyes (Congo Red, Tartrazine, Rhodamine B, and Methylene Blue) solution under visible light irradiation. Compared to pure cobalt oxide, Ni-incorporated Co₃O₄ exhibits a substantially higher photocatalytic efficiency that increases with Ni doping concentration. The photocatalysts displayed superior recycling stability, retaining high performance after three cycles. The photosensing properties were investigated under UV light, and a considerable photocurrent enhancement was observed. As a result, it is illustrated that Ni-doped cobalt oxide NPs are a potential material for the fabrication of photosensitive devices.

Transition metal oxides have gathered momentum among the scientific community on account of their peculiar procession in physico-chemical, opto-electronic, magnetic, electrochemical, and biological attributes resulting from anisotropic charge distribution of partly filled d-orbitals, non-stoichiometric behaviour, and diverse oxidation states of the cations. The current work emphasize on the systematic synthesis and characterization of pure and zinc (Zn) incorporated nickel oxide (NiO) nanoparticles in varying concentrations Zn_xNi_1−xO (x = 0, 0.1, 0.2, and 0.3) via a scalable sol-gel approach assisting citric acid (C₆H₈O₇) as a congealing factor. A series of extensive analyses were executed to investigate the structural, opto-electrical, and magnetic characteristics of prepared nanoparticles. X-Ray Diffraction (XRD) studies confirmed the face-centered cubic structure of as-synthesized samples and the corresponding crystallite size is found to decrease with an increasing dopant concentration as estimated from the Scherrer method. Scanning electron microscopy studies portrayed the spherical structure and porous nature of NiO nanoparticles. Particle size calculated from SEM shows the decreasing trend with dopant discrepancy which is in accordance with crystallite size measured from XRD results. Energy Dispersive X-ray (EDX) spectra revealed the presence of estimated molecular assembly in synthesized samples. The cubic configuration and the presence of functional groups existing in synthesized nanoparticles were endorsed from Fourier Transform Infra-Red (FTIR) spectra. The optical absorption spectrum examined from UltraViolet-visible (UV-vis) spectroscopy evaluates the energy bandgap and it is noticed to increase from 2.48 to 2.87 eV affirming the Burstein Moss shift. The energy dispersion of optical parameters plays a crucial contribution in optical materials pursuant to its prominence in optical communications and in fabricating novel devices for spectral dispersion. Optical and energy dispersion parameters evaluated from Wemple-DiDomenico (WDD) model and non-linear optical parameters were deliberated from optical studies. Urbach energy and another pivotal optical criterion highly correlated with the bandgap energy anchored in the fabrication of optoelectronic devices were assessed. The electrical characteristics such as dielectric constant, loss, and conductivity exhibited by pure and Zn doped nickel oxide nanoparticles were reported. Molecular electronic polarizability assessed through elementary solid-state parameters is in better concurrence with diverse relations like Clausius-Mossotti, Lorentz-Lorent, bulk modulus, optical electronegativity, energy band gap. The pore size distribution of substance matrix and the associated surface area were elucidated from Brunauer-Emmett-Teller (BET) analysis. Dispersive magnetic properties and two pivotal parameters were derived from the Law of Approach to Saturation (LAS) operandi. Further, microbial cell mechanism was illustrated through nano-architecture design, and the antibacterial and antifungal activity encountered by undoped and zinc doped NiO nanoparticles against different microbial strains were deeply discussed for pilot production of antimicrobial agents.

Ag nanoparticles and Ag/GO nanocomposites have been synthesized by facile, eco‐friendly, and cost‐effective green approach using the peel extracts of Punica granatum. The synthesized Silver Nanoparticles and Silver Graphene Oxide nanocomposites were characterized by UV–visible spectroscopy, X‐ray diffraction, transmission electron microscopy, and Fourier transform infrared analysis. AgNPs revealed spherical morphology with particle size ranging from 30 to 40 nm. Scanning electron microscopy results revealed silver nanoparticles with an average size of 35 nm being uniformly distributed over GO sheets. The surface plasmon band appears at 433 nm for AgNPs and 458 nm for Ag/GO nanocomposites. The green synthesized nanoparticles were found to have excellent antibacterial efficacy against both gram positive (Staphylococcus aureus, Bacillus subtilis) and gram negative (Klebsiella pneumoniae, Escherichia coli) bacterial strains. The results showed that Ag/GO nanocomposites showed better antibacterial activity than pure AgNPs with maximum inhibitory zone of 28 mm for Escherichia coli. This attributes to the role of GO sheets in preventing AgNPs from agglomerating and oxidizing. The anticancer activity of AgNPs and Ag/GO nanocomposites were tested against human breast cancer cell line (MCF‐7) which demonstrated a dose dependent activity with half minimum inhibitory concentration of 100 and 150 μg/ml.