J. Judith Vijaya

Comparative investigation of zirconium oxide (ZrO2) nano and microstructures for structural, optical and photocatalytic properties.

ZrO(2) nanocrystals were synthesized by the microwave combustion method (MCM) using urea as the fuel without using any template, catalyst or surfactant. For the purpose of comparison, it was also prepared using the conventional combustion method (CCM). The as-synthesized ZrO(2) was characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy. The results indicated that the ZrO(2) nanocrystals obtained by MCM show high crystallinity and uniform size distribution than the ones prepared by CCM. Hence, the influence of the preparation methods on the structure, morphology and optical activity of ZrO(2) was investigated systematically. Photocatalytic degradation (PCD) of 4-Chlorophenol (4-CP), a potent endocrine disrupting chemical in aqueous medium was investigated by ZrO(2) nanocrystals obtained by MCM. The kinetics of PCD was found to follow pseudo first-order. Having established that ZrO(2) was photo catalytically active, the mixed oxide catalysts of ZrO(2)-TiO(2) were also tested for the PCD of 4-CP.

Green synthesis of NiO nanoparticles using Moringa oleifera extract and their biomedical applications: Cytotoxicity effect of nanoparticles against HT-29 cancer cells

Green protocols for the synthesis of nickel oxide nanoparticles using Moringa oleifera plant extract has been reported in the present study as they are cost effective and ecofriendly, moreover this paper records that the nickel oxide (NiO) nanoparticles prepared from green method shows better cytotoxicity and antibacterial activity. The NiO nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), High resolution transmission electron microscopy (HRTEM), Energy dispersive X-ray analysis (EDX), and Photoluminescence spectroscopy (PL). The formation of a pure nickel oxide phase was confirmed by XRD and FTIR. The synthesized NiO nanoparticles was single crystalline having face centered cubic phase and has two intense photoluminescence emissions at 305.46nm and 410nm. The formation of nano- and micro-structures was confirmed by HRTEM. The in-vitro cytotoxicity and cell viability of human cancer cell HT-29 (Colon Carcinoma cell lines) and antibacterial studies against various bacterial strains were studied with various concentrations of nickel oxide nanoparticles prepared from Moringa oleifera plant extract. MTT assay measurements on cell viability and morphological studies proved that the synthesized NiO nanoparticles posses cytotoxic activity against human cancer cells and the various zones of inhibition (mm), obtained revealed the effective antibacterial activity of NiO nanoparticles against various Gram positive and Gram negative bacterial pathogens.

Photocatalytic activity of binary metal oxide nanocomposites of CeO2/CdO nanospheres: Investigation of optical and antimicrobial activity.

We report the synthesis of high quality CeO2-CdO binary metal oxide nanocomposites were synthesized by a simple chemical precipitation and hydrothermal method. Cerium nitrate and cadmium nitrate were used as precursors. Composition, structure and morphology of the nanocomposites were analyzed by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). XRD pattern proves that the final product has cubic phase and the particle size diameter of the nanocomposites are 27nm, XRD results also indicated that the crystalline properties of the nanocomposite were improved without affecting the parent lattice, FESEM analysis indicates that the product is composed of spherical particles in clusters. The morphological and optical properties of CeO2-CdO nanosamples were characterized by HRTEM and DRS spectroscopy. The IR results showed high purity of products and indicated that the nanocomposites are made up of CeO2 and CdO bonds. Absorption spectra exhibited an upward shift in characteristic peaks caused by the addition of transition metal oxide, suggesting that crystallinity of both the metal oxide is improved due to specific doping level. TGA plots further confirmed the purity and stability of nanomaterials prepared. Hence the nanocomposite has cubic crystal lattice and form a homogeneous solid structure. From the result, Cd(2+) ions are embedded in the cubic crystal lattice of ceria. The growth rate increases which are ascribed to the cationic doping with a lower valence cation. Ce-Cd binary metal oxide nanocomposites showed antibacterial activity, it showed the better growth inhibition towards p.aeruginosa. Exploit of photodegradation and photocatalytic activity of large scale synthesis of CeO2-CdO binary metal oxide nanocomposites was reported.

Photocatalytic degradation effect of malachite green and catalytic hydrogenation by UV–illuminated CeO2/CdO multilayered nanoplatelet arrays: Investigation of antifungal and antimicrobial activities

CeO2/CdO multi-layered nanoplatelet arrays have been synthesized by sol-gel method at two different temperatures using Citrus limonum fruit extract and the effect of particle size on the photocatalytic performance is studied. The particle size and phases was analysed by X-ray diffraction pattern (XRD) which brought out the formation of cubic phase in the synthesized samples. Field Emission Scanning electron microscopy (FESEM) revealed the surface morphology and made up of cumulative form of platelet shaped arrays with an average size of 10nm. The elemental composition and the purity of the nanomaterials were confirmed by Energy Dispersive X-ray spectroscopy (EDX). CeO2/CdO multilayered binary metal oxide nanoplatelet arrays were formed which was further explored with Fourier transform infrared spectroscopy (FTIR), it reveals that the nanocomposites contain CeO and CdO bonds. Determination of the direct and indirect bandgap energy of the nanoplatelet arrays was carried out by UV-Vis-DRS studies. In MG degradation, both the hole (h+) and hydroxyl radical (OH) played a major role than the superoxide radical (O2-). Possible photo degradation mechanisms are proposed and discussed in this article. CeO2/CdO multi-layered nanoplatelet arrays showed antibacterial activity and among the tested ones, it showed better growth inhibition towards P. aeruginosa MTCC73. Thus, this greener synthetic procedure was a highly effective method due to low-cost, highly effective UV light responsive material for environmental safety.

Studies on the efficient dual performance of Mn1–xNixFe2O4 spinel nanoparticles in photodegradation and antibacterial activity

The present work describes the successful synthesize of spinel magnetic ferrite Mn1-xNixFe2O4 (x=0.0, 0.1, 0.2, 0.3, 0.4 & 0.5) nanoparticles via a simple microwave combustion method which was then evaluated for its photocatalytic activity in the degradation of indigo carmine (IC) synthetic dye, a major water pollutant. Our results reveal that the synthesized of Ni2+ doped MnFe2O4 nanoparticles possess well-crystalline pure cubic spinel phase, exhibit excellent optical and magnetic properties. Further, the photocatalytic performance of the synthesized nanoparticles at different concentration ratios of Ni2+ ions was monitored by photocatalytic degradation of indigo carmine synthetic dye under UV (λ=365nm) light irradiation. In order to get maximum photocatalytic degradation (PCD) efficiency, we have optimized various parameters, which include catalyst dosage, initial dye concentration, pH and Ni2+ dopant content. It was found that the reaction was facilitated with optimum catalyst dose of 50mg/100mL, high dye concentrations of 150mg/L and acidic pH and among all the synthesized samples, Mn0·5Ni0.5Fe2O4 exhibit superior performance of photocatalytic activity on the degradation of indigo carmine synthetic dye. These results highlighted the potential use of effective, low-cost and easily available photocatalysts for the promotion of wastewater treatment and environmental remediation. In addition, the antibacterial activity of spinel magnetic Mn1-xNixFe2O4 nanoparticles against two Gram positive bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gram negative bacteria (Pseudomonas aeruginosa and Escherichia coli) was also examined. Our antibacterial activity results are comparable with the results obtained using the antibiotic, streptomycin.

Facile synthesis of heterostructured cerium oxide/yttrium oxide nanocomposite in UV light induced photocatalytic degradation and catalytic reduction: Synergistic effect of antimicrobial studies

Ceria (CeO2) is an exciting alternative noble metal catalyst, because it has ability to release and absorb oxygen in the redox system, and function as an oxygen buffer. In this study, heterostructured catalysts consisting of CeO2/Y2O3 nanocomposites were successfully synthesized by hydrothermal method in the presence of sodium hydroxide as a reducing agent from cerium nitrate and yttrium nitrate as a precursor which was then evaluated for its photocatalytic activity in the degradation of Rhodamine B (RhB) synthetic dye. Scanning electron microscopy (SEM) imparts the surface morphology and size of the prepared sample. Elemental compositions and the purity of the nanoparticles are proved by energy dispersive X-ray Spectroscopy (EDX). CeO2/Y2O3 nanoparticles were made up of CeO and YO bonds which are confirmed by Fourier transform infrared spectroscopy (FTIR). Synthesis temperature and pressure, during hydrothermal reactions, plays a critical role in controlling the shape, size, oxygen vacancy concentration, and low temperature reducibility in CeO2 based nanocomposites. The lattice constants and oxygen vacancy concentrations of ceria nanoparticles also depend upon the concentration of hydroxide ion which leads to better morphology at low temperature and pressure. Hydrogenation of p-nitrophenol to p-aminophenol with a reducing agent is conveniently carried out in aqueous medium by using this binary metal oxide catalyst. Further, the photocatalytic performance of the synthesized nanoparticles was monitored by photocatalytic degradation of Rhodamine B synthetic dye under UV light irradiation. To get maximum photocatalytic degradation (PCD) efficiency, we have used H2O2 for the generation of excess reactive oxygen species (ROS). In addition, the antibacterial activity of nanoparticles against bacteria was also examined. The observed antibacterial activity results are comparable with the results obtained using the standard antibiotic.

Synthesis of MoS2 nanosheet supported Z-scheme TiO2/g-C3N4 photocatalysts for the enhanced photocatalytic degradation of organic water pollutants

MoS2 nanosheets loaded with Z-scheme TiO2/g-C3N4 photocatalysts were prepared using a wetness impregnation method. Exfoliated two-dimensional g-C3N4 and MoS2 nanosheets were used for Z-scheme nanocomposite preparation. Structural, morphological, and photo-physical properties of the prepared photocatalysts were investigated using various spectroscopy and microscopy techniques. Few-layer MoS2 loaded Z-scheme TiO2/g-C3N4 photocatalysts exhibited extended absorbance in the visible region compared to other photocatalysts. The photocatalytic degradation of methylene blue, a common dye, and atrazine, a potent herbicide, in aqueous media were investigated using both pure and composite Z-scheme photocatalysts. 10 wt% g-C3N4 loaded-TiO2 showed higher degradation performance than the other g-C3N4-loaded and bare photocatalysts. This degradation enhancement was due to the improved electron/hole pair separation at the TiO2/g-C3N4 interface imparted by the Z-scheme electron transfer. Furthermore, MoS2 nanosheets loaded with Z-scheme TiO2/g-C3N4 photocatalysts exhibited superior degradation performance compared to all other photocatalysts. Few-layer MoS2 co-catalyst, as an electron acceptor/accelerator, in the Z-scheme composite photocatalyst increased the photocatalytic activity. Suitable mechanism was proposed for this enhanced charge separation performance using PL analysis and band potentials of photocatalysts. The pathway of atrazine degradation was investigated using LC/MS/MS, and a possible degradation mechanism was proposed.

Structure and magnetic properties of Cu-Ni alloy nanoparticles prepared by rapid microwave combustion method

Abstract Cu-Ni alloy nanoparticles were prepared by a microwave combustion method with the molar ratios of Cu2+ to Ni2+ as 3:7, 4:6, 5:5, 6:4 and 7:3. The as-prepared samples were characterized by XRD, HR-SEM, EDX and VSM. XRD and EDX analyses suggest the formation of pure alloy powders. The average crystallite sizes were found to be in the range of 21.56–33.25 nm. HR-SEM images show the clustered/agglomerated particle-like morphology structure. VSM results reveal that for low Ni content (Cu5Ni5, Cu6Ni4 and Cu7Ni3), the system shows paramagnetic behaviors, whereas for high Ni content (Cu3Ni7 and Cu4Ni6), it becomes ferromagnetic.

Green synthesis of Ag nanoparticles using Tamarind fruit extract for the antibacterial studies

In the present study, first time we report the microwave-assisted green synthesis of silver nanoparticles (AgNPs) using Tamarindus indica natural fruit extract. The plant extract plays a dual role of reducing and capping agent for the synthesis of AgNPs. The formation of spherical shape AgNPs is confirmed by XRD, HR-SEM, and HR-TEM. The presence of face-centered cubic (FCC) silver is confirmed by XRD studies and the average crystallite size of AgNPs is calculated to be around 6-8nm. The average particle diameter is found to be around 10nm, which is identified from HR-TEM images. The purity of AgNPs is confirmed by EDX analysis. The presence of sigmoid curve in UV-Visible absorption spectra suggests that the reaction has complicated kinetic features. To investigate the functional groups of the extract and their involvement in the reduction of AgNO3 to form AgNPs, FT-IR studies are carried out. The redox peaks are observed in cyclic voltammetry in the potential range of -1.2 to +1.2V, due to the redox active components of the T. indica fruit extract. In photoluminescence spectroscopy, the excited and emission peaks were obtained at 432nm and 487nm, respectively. The as-prepared AgNPs showed good results towards antibacterial activities. Hence, the present approach is a facile, cost- effective, reproducible, eco-friendly, and green method.

Pure and Mg-doped self-assembled ZnO nano-particles for the enhanced photocatalytic degradation of 4-chlorophenol

A novel self-assembled pure and Mg doped ZnO nano-particles (NPs) were successfully synthesized by a simple low temperature co-precipitation method. The prepared photocatalysts were characterized by X-ray diffraction, high resolution scanning electron microscopy, high resolution transmission electron microscopy, diffuse reflectance spectroscopy and photoluminescence (PL) spectroscopy. The results indicated that the prepared photocatalysts showed high crystallinity with a uniform size distribution of the NPs. The degradation of cholorphenols is highly mandatory in todays scenario as they are affecting the environment adversely. Thus, the photocatalytic degradation of 4-chlorophenol (4-CP), a potent endocrine disrupting chemical in aqueous medium was investigated by both pure and Mg-doped ZnO NPs under UV-light irradiation in the present study. The influence of the Mg content on the structure, morphology, PL character and photocatalytic activity of ZnO NPs were investigated systematically. Furthermore,the effect of different parameters such as 4-CP concentration, photocatalyst amount, pH and UV-light wavelength on the resulting photocatalytic activity was investigated.