Showing papers by "L. John Kennedy published in 2016"

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

Abstract: 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.

Spinel Ferrite Nanoparticles: Synthesis, Crystal Structure, Properties, and Perspective Applications

Abstract: Recent developments show that the exceptional physical, optical, magnetic, and electrical properties of spinel ferrite (SF) nanomaterials have now attracted the attention as high-density data storage materials, catalysts, gas sensors, rechargeable lithium batteries, information storage systems, magnetic bulk cores, adsorbents, magnetic fluids, microwave absorbers, and medical diagnostics. The aim of this review consists on an overview on the methods of preparation, the crystal structure and application of SFs used in technology for the design of new materials and devices. The chapter begins with a review of the different synthesis methods commonly used for the preparation of SFs. Then, the structural features of spinel unit cell, crystal chemical parameters, and extrinsic magnetic and optical properties are described in this chapter. Since the magnetism of SFs depends not only on particle chemistry and phase but also on the particle size and environment, the role of cationic distribution and ion exchange interaction are explored in determining the magnetic properties of the system. In addition, the potential applications of SFs in different fields of technology are also discussed.

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

Abstract: 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.

Comparative Study of Electrical Conductivity on Activated Carbons Prepared from Various Cellulose Materials

Abstract: The objective of this study was to calculate the electrical conductivity of the activated carbons obtained from various cellulose materials (sugarcane bagasse, rice straw, cotton cloth and waste newspaper) by a two-stage process. The DC conductivity was calculated by a two-probe method. Scanning electron microscopy and X-ray analysis confirmed the surface morphology and formation of graphene multilayer, respectively. The carbonization temperature has a distinct effect on the electrochemical performances of the cellulose materials. The activated carbon compressed at 750.12 kPa offered the highest electrical conductivity for all the other samples. It may be due to the dense packing of the material, collapse of the pores and decrease in air gap between the carbon particles as well as a combination of multilayer graphene, which could be the factors accountable for the increase in conductivity with compression pressures. The conductivity increases with an increase in the temperature. In addition, all the carbon samples showed a good electrochemical property and the specific capacitance at the scan rate of 2–3 mV/s.

Hierarchical ZSM-5 catalytic performance evaluated in the selective oxidation of styrene to benzaldehyde using TBHP

Abstract: Hierarchical ZSM-5 catalysts with different Si/Al ratios (20, 60 and 100) were hydrothermally synthesized. The prepared samples were studied by several techniques, including X-ray diffraction (XRD), X-ray fluorescence (XRF) analysis, Fourier transform infrared (FTIR) spectroscopy, N2 adsorption–desorption, high resolution transmission electron microscopy (HR-TEM), high resolution scanning electron microscopy (HR-SEM), and differential scanning calorimetry (DSC) technique. The average crystallite size and crystallinity decreases with increasing Si/Al ratio, which is confirmed by XRD. FTIR analysis further confirms the formation of ZSM-5 by the presence of characteristic bending, stretching and framework vibration. The HR-TEM images showed that all the samples having disc-like nanostructures are assembled by many primary nanocrystals. The as-synthesized ZSM-5 zeolites are thermally stable, which is confirmed by DSC. The catalytic activity of ZSM-5 zeolites was evaluated in the selective oxidation of styrene using tertiary-butyl hydroperoxide (TBHP) as the oxidant. Among the catalysts, ZSM-5(60) catalyst showed significantly higher yield of benzaldehyde at optimum conditions. The catalyst was recovered and recycled three times without a significant loss in activity and selectivity.

Effects of Ba doping on structural, morphological, optical, and photocatalytic properties of self-assembled ZnO nanospheres

Abstract: A simple low-temperature co-precipitation method was employed to synthesize pure and Ba-doped self-assembled ZnO nanospheres. The presence of self-assembled nanosphere-like morphology, high crystallinity, uniform size distribution, and more defects were confirmed by X-ray diffraction, high-resolution scanning electron microscopy, high-resolution transmission electron microscopy, diffuse reflectance spectroscopy, and photoluminescence spectroscopy. Photocatalytic degradation of 2,4,6-trichlorophenol, a potent endocrine-disrupting chemical in aqueous medium was investigated. The effects of Ba doping on the structure, morphology, absorption, emission, and photocatalytic activity of ZnO nanospheres were investigated systematically. Furthermore, the effects of different photocatalytic degradation reaction parameters were investigated. The resulting photocatalytic degradation activity of Ba-doped ZnO nanospheres shows superior efficiency compared to pure ZnO and commercial TiO2 (Degussa P-25). A simple co-precipitation method was developed to synthesize pure and Ba-doped ZnO self-assembled nanospheres. The prepared photocatalyst shows a novel morphology, high crystallinity, uniform size distribution, and more defects. Effect of Ba doping on the structural, optical and photocatalytic properties of ZnO nanospheres were investigated systematically.

Synergy effect in the photocatalytic degradation of textile dyeing waste water by using microwave combustion synthesized nickel oxide supported activated carbon

Abstract: Nickel oxide nanoparticles supported activated carbon (NSAC) photocatalyst was successfully prepared using a cost-effective microwave irradiation method. The earned UV light-sensitive NSAC composites were characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, High-resolution scanning electron microscope with energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller surface area analyzer. Optical properties of NSAC composites were investigated using UV–Vis diffuse reflectance spectroscopy and photoluminescence spectroscopy, which exposed prolonged light absorption in UV light region and hold better charge separation capability, respectively, as compared to pure NiO. The photocatalytic activity was tested by the degradation of textile dye waste water (TDW) under UV light irradiation. Chemical oxygen demand of TDW was calibrated before and after the photocatalysis experiment under UV light to evaluate the mineralization of wastewate...

Influence of Fe-Doping on the Structural, Morphological, Optical, Magnetic and Antibacterial Effect of ZnO Nanostructures.

Abstract: Pure and Fe-doped ZnO nanostructures with different weight ratios (0.5, 1.0, 1.5, and 2.0 at wt% of Fe) were successfully synthesized by a facile microwave combustion method using urea as a fuel. The detailed structural characterization was performed by means of X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and vibrating sample magnetometry (VSM). XRD patterns refined by the Rietveld method indicated that Fe-doped ZnO have a single pure phase with wurtzite structure, suggesting that Fe ions are successfully incorporated into ZnO crystal lattice by occupying Zn ionic sites. Interestingly, the morphology was found to change substantially from grains to nanoflakes and then into nanorods with the variation of Fe-content. The optical band gap estimated using DRS was found to be red-shifted from 3.220 eV for the pure ZnO nanostructures, then decreases up to 3.200 eV with increasing Fe-content. Magnetic studies showed that Fe-doped ZnO nanostructures exhibit room temperature ferromagnetism (RTFM) and the saturation magnetization attained a maximum value of 8.154 x 10(-3) emu/g for the highest Fe-content. The antibacterial activity of pure and Fe-doped ZnO nanostructures against a Gram-positive bacteria and Gram-negative bacteria was investigated. Pure ZnO and Fe-doped ZnO exhibited antibacterial activity, but it was considerably more effective in the 1.5 wt% Fe-doped ZnO nanostructures.