R. Murugan

Comparative study of structural and magnetic properties of transition metal (Co, Ni) doped ZnO nanoparticles

In this paper, we report the structural, optical and magnetic properties of nano crystalline samples of Zn1−x(TM)xO (TMxa0=xa0Ni, Co and xxa0=xa00, 0.05, 0.10 and 0.15) synthesized by co-precipitation method. The synthesized samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), photoluminescence (PL), micro-Raman, and vibrating sample magnetometerxa0(VSM). It is observed from XRD patterns that all the samples reveal polycrystalline hexagonal wurtzite structure without any extra phase and average particle size decreased with increasing transition metal (TM) doping concentration. FTIR spectrum has been used to confirm the functional group of Ni–O and Co–O bond. SEM images demonstrated the grain like morphologies of TM doped ZnO nanoparticles (NPs). PL spectra of all samples exhibited a broad emission in the visible range. The carriers (donors) bounded on the TM sites were observed from the micro Raman spectroscopic studies. TM doped ZnO NPs showed significant changes in the M–H loop where the diamagnetic behavior of ZnO changes to ferromagnetic nature when doping with Ni and Co ions.

Effect of rf power on the properties of magnetron sputtered CeO2 thin films

Cerium oxide (CeO2) thin films were prepared by rf magnetron sputtering (PVD) technique onto glass substrates at a pressure of 3xa0×xa010−4xa0mbar of Ar+ atmosphere. The thickness of deposited CeO2 films ranges from 380 to 590xa0nm. X-ray diffraction studies on the films showed that the films are polycrystalline in nature. The crystallite size (D), dislocation density (δ) and micro-strain (ε) were evaluated from XRD patterns. The obtained micro-strain and dislocation density of the films were found to be ~10−3 and ~1016xa0lines/m2 respectively, along with a marginal increase in crystallite size from ~6 to ~9xa0nm. The experimental diffraction values of the films agreed with the standard values. The optical properties of cerium oxide films were studied in the wavelength range 325–900xa0nm. Optical absorption, extinction coefficients, refractive index and optical conductivity were evaluated from optical measurements. The films are found to be highly transparent in visible region and exhibits low reflectance in the ultraviolet region. The optical band gap of the films was found to decrease from 3.53 to 3.45xa0eV, with the increase of film thickness. The defects were found to increase with the increase of rf power. Emission bands like UV, weak blue, blue, blue–green and green bands were observed from PL spectra of CeO2 thin films. Raman active mode (F2g) of CeO2 thin films was observed at 466xa0cm−1 and films deposited at higher rf power show increased line width as well as peak intensity in Raman spectra. Rf power induced formations of flower like morphology were observed in SEM images. The surface roughness of CeO2 thin films was increased from 2.9 to 7.7xa0nm with the increase of rf power as ascertained from AFM images and the results are discussed.

Structural, optical and antibacterial activity studies of neodymium doped ZnO nanoparticles

Trivalent neodymium doped ZnO (Zn1−xNdxO, xxa0=xa00.0, 0.03, 0.06 and 0.09) nanoparticles (NPs) synthesized by co-precipitation method with improved optical and antibacterial performance is reported. X-ray diffraction pattern indicates most of Nd3+ ions are incorporated in Zn2+ ions of ZnO lattice and hence there is no secondary peak of NdO3 in synthesized ZnO NPs. Fourier transform infrared spectroscopy analysis of synthesized NPs exhibits similar patterns in Zn/Nd–O bands observed at 480xa0cm−1. High resolution scanning electron microscopy images revealed the formation of spindle like morphology and the incorporation of Nd ions is confirmed by energy dispersive spectra analysis. UV–visible absorption spectra of pure and Nd doped ZnO NPs showed the variation of the band gap in the range of 3.06–2.65xa0eV. Raman analysis confirmed the formation of wurtzite structure of NPs was distorted due to Nd substitution in ZnO matrix. X-ray photoelectron spectroscopy confirmed the Nd incorporation in the ZnO lattice as Nd3+. The prepared Nd doped ZnO NPs showed potential application in antibacterial activities.

Glucose sensing behavior of cobalt doped ZnO nanoparticles synthesized by co-precipitation method

Pure and Zn1−xCoxO (xxa0=xa00.05, 0.10 and 0.15) nanoparticles were synthesized by co-precipitation method. Powder X-ray diffraction studies confirmed that pure and Co doped ZnO have a single phase nature with hexagonal wurtzite structure and Co2+ ions were successfully incorporated into the lattice position of Zn2+ ions in ZnO matrix. FTIR and EDS spectra results confirmed the incorporation of the dopants into the ZnO lattice structure. FESEM images showed the flower like morphology in ZnO and flowers are dispersed to grains in Co doped ZnO nanoparticles. The chemical composition of Zn0.90Co0.10O nanoparticles were confirmed by XPS. The XPS results clearly showed the existence of Co as a doping element into the ZnO crystalline lattice. Further, the synthesized Co doped ZnO nanoparticles have been used for electrochemical non-enzymatic glucose biosensing. The lowest detection limit of the proposed sensor was found to be 5xa0µM. The sensor selectively oxidizes glucose in the presence of other interfering compounds like l-dopa, ascorbic acid, hydrogen peroxide and uric acid.

Properties of SILAR deposited magnetite (Fe3O4) thin films: effect of bath temperatures

Magnetite thin films were deposited by varying the temperature of the bath in the SILAR deposition process. Structural, morphological and optical properties of the deposited films were analyzed using X-ray diffraction, Raman spectroscopy, Field emission scanning electron microscopy, UV–Visible spectroscopy. With the increase in bath temperature of the deposition process, crystallite size decreases and dislocation density and microstrain increases. Raman spectra confirm the formation of magnetite phase for all the deposited films. FESEM images reveal the bath temperature’s influence on the surface morphology. Considerable variations in the optical properties were observed for the films and were discussed in detail.