N. Kannadasan

Biosynthesis of silver nanoparticles from the marine seaweed Sargassum wightii and their antibacterial activity against some human pathogens

In this paper, we have reported on biological synthesis of nano-sized silver and its antibacterial activity against human pathogens. The nanoparticles of silver were formed by the reduction of silver nitrate to aqueous silver metal ions during exposure to the extract of marine seaweed Sargassum wightii. The optical properties of the obtained silver nanoparticles were characterized using UV–visible absorption and room temperature photoluminescence. The X-ray diffraction results reveal that the synthesized silver nanoparticles are in the cubic phase. The existence of functional groups was identified using Fourier transform infrared spectroscopy. The morphology and size of the synthesized particles were studied with atomic force microscope and high-resolution transmission electron microscope measurements. The synthesized nanoparticles have an effective antibacterial activity against S. aureus, K. pneumoniae, and S. typhi.

Synthesis, characterization and photocatalytic activity of ZnO nanoparticles prepared by biological method

Zinc oxide have been produced via a simple green method from zinc nitrate and leaf extract aqueous solutions. Prepared ZnO nanoparticles (NPs) were investigated by employing through UV-Visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence (PL) spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR), field emission-scanning electron microscope (FE-SEM), and transmission electron microscope (TEM), respectively. The present investigation, confirmed the estimated band gap 3.51eV and the PL intensity at 402nm in visible region are dependent upon the geometrical shape and size of the ZnO NPs. The TEM micrograph and XRD pattern confirmed the hexagonal wurtzite structure of ZnO NPs. The presence of functional groups and the chemical bonding are confirmed by FTIR spectra. EDS shows that the highly pure ZnO nanostructures. Moreover, the catalytic activity of synthesized ZnO in the reduction of methylene blue was studied by UV-Vis spectroscopy. The effects of process conditions on the morphology and size of ZnO have been found from FE-SEM and TEM analyses, respectively.

Effect of annealing on the ZnS nanocrystals prepared by chemical precipitation method

Nanocrystals of ZnS have been synthesized through simple chemical precipitation method using thiourea as sulphur source. The synthesized products were annealed at different temperatures in the range of 200-800°C. The as-synthesized and annealed samples were characterized by X-ray diffraction (XRD), UV-Visible absorption (UV-Vis), and room temperature photoluminescence (PL) measurements. The morphological features of ZnS annealed at 200 and 500°C were studied by atomic force microscope (AFM) and transmission electron microscope (TEM) techniques. The phase transformation of ZnS and formation of ZnO were confirmed by thermogravimetric (TG) and differential thermal analysis (DTA) curves.

Luminance behavior of Ce3+ doped ZnS nanostructures.

We report the synthesis and characterization of undoped and various levels of Ce(3+) doped ZnS nanocrystal. The structure and size of the products were studied by X-ray diffraction (XRD). The existence of functional groups was identified by Fourier transform infrared spectrometry (FT-IR). The UV-Visible measurements reveal that the synthesized products are blue shifted when compared with bulk phase of ZnS as a result of quantum confinement effect. The PL studies show an enhancement in the intensity of emission band in the UV region on increased Ce(3+) doping. The morphology of the products was evaluated by Field emission scanning electron microscope (FESEM) and High resolution transmission electron microscopy (FESEM). The presence of Ce(3+) was confirmed by Energy dispersive spectral analysis (EDS). The thermal stability of pure and doped products was analyzed by thermo gravimetric and differential thermal analysis (TG-DTA).

Optical behavior and sensor activity of Pb ions incorporated ZnO nanocrystals.

We present the synthesis and characterization of nanocrystalline ZnO doped with Pb in different concentrations. The structural and chemical compositions of the products are characterized by XRD, XPS, EDS and FT-IR spectroscopy. The observed results suggest that Pb ions (Pb(2+) and Pb(4+)) are successfully incorporated into the lattice position of Zn(2+) ions in ZnO. The optical properties of the products are studied by UV-Vis and room temperature PL measurements. The PL emission spectra of ZnO:Pb, show the intensity quenching for both the UV and visible emissions. The influence of Pb on controlling the size and morphology of ZnO is studied by FESEM and confirmed by HRTEM. Amperometric response shows that ZnO incorporated with 0.075M of Pb ions has enhanced sensor activity for H2O2 than the undoped product.

Synthesis and characterization of surfactants assisted Cu2+ doped ZnO nanocrystals

In the present work, we report a simple chemical precipitation method to synthesize precursors of different levels of Cu(2+) ions doped crystalline zinc oxide (ZnO) nanoparticles in the presence of capping agents namely cetyltrimethyl ammonium bromide (CTAB) and sodium hexametaphosphate (SHMP). Thermal analysis result suggests that 300°C could be the optimum level of annealing for the harvest of pure phase of ZnO from the as prepared particles. The structural, optical and chemical features of undoped and surfactants assisted ZnO: Cu(2+) nanoparticles were studied by X-ray powder diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-Visible (UV-Vis) absorption spectroscopy and photoluminescence (PL) measurements. Among the two surfactants used SHMP is an effective one in controlling the size and morphology of the particles.

Synthesis of Ce4+ ions doped ZnO electrode as a sensor for hydrogen peroxide

Abstract Ce4+ ions doped ZnO nanoparticles were synthesized by the simple chemical precipitation method with different levels of cerium. The synthesized products were analyzed for X-ray diffraction and photoluminescence measurements. The morphology of the optimum level of Ce4+ doped ZnO was studied by high resolution transmission electron microscopy analysis. To ascertain the sensor activity of Ce4+ doped ZnO, the electrocatalytic response to the reduction of H2O2 was studied with ZnO and ZnO: Ce4+ electrodes. Fabricated ZnO: Ce4+ sensor displays excellent performance towards the detection of H2O2 than bare ZnO.

Effect of Thermal Annealing on the Cd(OH) 2 and Preparation of Cdo Nanocrystals

Nanosized β-Cd(OH)2 were successfully synthesized via simple chemical precipitation method using cadmium nitrate as a precursor in a solution of sodium hydroxide. The CdO nanoparticles were harvested from β-Cd(OH)2 by thermal decomposition at 400°C. The structural, optical, and magnetic properties of the as prepared and annealed products of β-Cd(OH)2 were studied. The morphology of the CdO nanocrystals annealed at 400°C analyzed by FETEM exhibits pseudo spherical morphology with sizes around 60 nm.

Synergistic effect of bimetal ions (Ce, Pb) incorporation on optical, structural, and sensory activity of ZnO nanocrystals

We report the synthesis and application of cerium and lead co-doped ZnO nanocrystals for the detection of H2O2. The nanocrystals of undoped and co-doped ZnO were prepared by a simple chemical precipitation method. The structural and chemical compositions of the products were characterized by the X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results demonstrate that Ce and Pb ions were successfully incorporated into the lattice position of Zn2+ ions in ZnO matrix. The optical properties of the synthesized products were analyzed by UV-Visible reflectance (UV-Vis DRS) and photoluminescence (PL) measurements. The photoluminescence results of co-doped ZnO suggest suppressed UV emission and enhanced oxygen vacancy mediated green emission on increased Pb doping. The morphological features of undoped and co-doped products were studied by the field emission scanning electron microscope (FESEM) and confirmed by the high-resolution transmission electron microscope (HRTEM). The electrochemical properties of the products were investigated by amperometry, cyclic voltammetry, and electrochemical impedance spectroscopy. The results indicate that the co-doped ZnO electrode is capable of delivering a higher sensory activity against H2O2 than the bare ZnO.