Preparation and Properties of Cobalt Doped ZnO Nanowires (original) (raw)
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Preparation of electrodeposited cobalt nanowires
Materials Research-ibero-american Journal of Materials, 2006
Nanostructured magnetic materials have great interest because of their applications in high-density magnetic information storage and for magnetic sensors. The electrodeposition of materials into porous alumina arrays is a suitable technique to produce nanomaterials, since highly ordered uniform nanomaterials can be obtained simply and cheaply. In this work, template-assisted Co nanowire arrays were prepared by electrodeposition into nanometer-sized pores of an alumite film using a two-electrode electrochemical cell. The Co nanowires were electrodeposited from a solution of 400 g/L of CoSO 4 .7H 2 O and 40 g/L of H 3 BO 3. The morphology of the samples was investigated by means of TEM and AFM. The structural characteristic of the samples was examined using XRD, EDX and FTIR, which confirm the cobalt nanowire formation.
Synthesis and Characterization of Zinc Oxide (ZnO) Nanowire
Journal of Nanomedicine & Nanotechnology, 2015
Nanowires are structures that have a lateral size constraint to tens of nanometers or less and an unconstrained longitudinal size. The syntheses and characterization of ZnO nanowire with hexagonal structure was successfully achieved using chemical bath deposition technique. The nanowires obtained were further characterized by scan electron microscope (SEM), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and spectrophotometer. The SEM micrographs revealed the morphology of ZnO nanowires with diameter 170.3 nm and 481 nm. This revealed that the pH 8.1 of the bath solution and the optimized value form ZnO nanowires with hexagonal shape at top surface. The XRD pattern of the samples revealed ZnO nanowire have hexagonal crystallite structure. Where upon the crystallite size supported increased annealing temperature (0.536 nm, 0.541 nm and 0.557 nm at 100°C, 150°C and 200°C respectively). The EDX analysis revealed the elemental compositions of samples and confirmed the presence of Zn and O2. The results of the optical analysis showed that ZnO nanowire have high absorbance in the ultraviolet and infrared regions with high transmittance in the visible region. The absorbance of the nanowire increases with increasing annealing temperature. Its high absorbance in the ultraviolet region suggest it applicability as solar harvester for trapping solar energy, used for photovoltaic panel with capacity to converting sunlight radiation directly to electricity for commercial or industrial purposes.
Structural and magnetic properties of electrodeposited cobalt nanowires in polycarbonate membrane
physica status solidi (a), 2009
Perpendicular Silicon nanowires (SiNWs), having 20 micrometer in length, were fabricated by metal assisted chemical etching of n-type Si(100) wafers in aqueous HF-solution. In a second step, NiFe films were electrodeposited onto theses SiNWs. The structure and magnetic properties of as deposited NiFe layers were studied by X ray diffraction (XRD) and vibrating sample magnetometer (VSM). From X-ray diffraction, the FCC NiFe structure was evidenced with a lattice constant, a, equal to 3.5270 Å. From hysteresis curves, we compute the coercive field, Hc, values. We found that the Hc // values range from 102 Oe to 236 Oe.
Co-DOPED ZnO NANOWIRES GROWN BY VAPOR-LIQUID-SOLID METHOD: STRUCTURAL, OPTICAL AND MAGNETIC STUDIES
2012
We report on the growth of Co-doped ZnO nanowires (NWs) on Si substrate using a self-catalytic vapor deposition method from a Co-doped ZnO nanopowder source and study its structural, optical and magnetic properties for the as-grown and rapid thermal annealed samples. Co (5%)-doped ZnO (ZnCoO) nanoparticles (NPs) are used as source material for the growth process. Electron microscopy imaging clearly reveals the formation of long ZnO NWs with uniform diameter. X-ray di®raction analysis con¯rms the single crystalline hexagonal structure of Co-doped ZnO NWs without impurities of metallic cobalt or other phases. Micro-Raman studies of doped samples show doping/disorder induced additional modes as compared to the undoped ZnO. Room temperature photoluminescence spectra of the doped ZnO NWs show strong emission band at 380nmandnosigni¯cantemissionwasobservedinthevisibleregionindicatinglowdefectcontentintheNWs.Theˉelddependentmagnetization(MAˋHcurve)measuredatroomtemperatureexhibitsparamagneticnaturefortheNWswiththemagneticmomentintherange2Aˋ3.7milli−emu/cm2fortheappliedeldof2Tesla,whilethesourceZnCoONPsexhibitroomtemperatureferromagnetismwithsaturationmagnetization380 nm and no signi¯cant emission was observed in the visible region indicating low defect content in the NWs. Thē eld dependent magnetization (MÀH curve) measured at room temperature exhibits paramagnetic nature for the NWs with the magnetic moment in the range 2À3.7 milli-emu/cm 2 for the applied eld of 2 Tesla, while the source ZnCoO NPs exhibit room temperature ferromagnetism with saturation magnetization 380nmandnosigni¯cantemissionwasobservedinthevisibleregionindicatinglowdefectcontentintheNWs.Theˉelddependentmagnetization(MAˋHcurve)measuredatroomtemperatureexhibitsparamagneticnaturefortheNWswiththemagneticmomentintherange2Aˋ3.7milli−emu/cm2fortheappliedeldof2Tesla,whilethesourceZnCoONPsexhibitroomtemperatureferromagnetismwithsaturationmagnetization6 emu/g. Possible mechanism of alteration in magnetic behavior in doped NWs are discussed based on the growth conditions and role of defects.
Physical Chemistry Chemical Physics, 2013
In the present paper, vertically aligned arrays of zinc nanowires were synthesized by electrochemical deposition into ion track-etched polycarbonate membranes in the ionic liquid electrolyte 1-ethyl-3methylimidazolium trifluoromethylsulfonate ([EMIm]TfO)/Zn(TfO) 2 . Cyclic voltammetry and chronoamperometry were performed to investigate the electrochemical growth of zinc nanowires inside of the membranes. The transport processes and mechanisms of the nanowire growth in the membranes are also discussed. A supporting zinc or copper layer was deposited on the sputtered side in order to make the back layer thick enough to stabilize the wires. Zinc nanowires with a diameter of 90 nm and a length of up to 18 mm were obtained after removing the template. Furthermore, short nanowires with lengths less than 5 mm and a sandwich-like structure with nanowires in the middle were also synthesized. Vertically aligned zinc nanowire structures on such a substrate might be a potential anode candidate for future generation lithium ion batteries.
Synthesis and magnetic properties of Mn doped ZnO nanowires
2007
Mn doped ZnO nanowires have been synthesized using a simple autocombustion method. The as-synthesized Mn doped ZnO nanowires were characterized by X-ray diffraction and transmission electron microscopy. An increase in the hexagonal lattice parameters of ZnO is observed on increasing the Mn concentration. Optical absorption studies show an increment in the band gap with increasing Mn content, and also give evidence for the presence of Mn2+ ions in tetrahedral sites. All Zn1−xMnxO (0≤x≤0.250≤x≤0.25) samples are paramagnetic at room temperature. However, a large increase in the magnetization is observed below 50 K. This behavior, along with the negative value of the Weiss constant obtained from the linear fit to the susceptibility data below room temperature, indicate ferrimagnetic behavior. The origin of ferrimagnetism is likely to be either the intrinsic characteristics of the Mn doped samples, or due to some spinel-type impurity phases present in the samples that could not be detected.
Surface and Interface Analysis, 2008
Preparation of ZnO in different nano-morphological forms became a hot topic during the last few years. This tendency was motivated by the wide field of potential applications ranging from optics to electronics and spintronics. In the present work, we deal with the preparation of ZnO nanowires and nanostructured thin films using electrochemical deposition.ZnO nanowires were grown using the template approach, namely by replicating the nanopores of polycarbonate ion track membranes. The method yields uniform arrays of nanowires with the morphology controlled by the shape and size of the templates pores. Adding polyvinylpyrolidone as an additive in the growth bath became a necessity due to the fact that polycarbonate ion track membranes are usually hydrophobic and thus filling of the nanopores with the growth electrolyte is rather difficult. In order to better understand the influence of the additive on the electrochemical deposition of such nanostructures, similar experiments were performed for the deposition of ZnO thin films.Scanning electron microscopy, X-ray diffraction and optical spectroscopy measurements were performed for characterization of the deposited structures. Copyright © 2008 John Wiley & Sons, Ltd.
Electrical and Magnetic Properties of Doped ZnO Nanowires
MRS Proceedings, 2006
ZnO nanowires doped with Mn, Fe, Sn, and Li during the thermal growth following direct chemical synthesis were investigated using electric and magnetic measurements. Currentvoltage characteristics of individual nanowires configured as a two-terminal device with Al electrodes show apparent rectify behavior indicating the Schottky-like barrier formation and resistivity being less 3 Ω · cm. Reproducible resistance modulation by a dc voltage at room temperature is observed. Magnetic susceptibility of the doped nanowires as a function of temperature demonstrates Curie-Weiss behavior. Magnetization versus field curves show hysteresis with the coercive field of about 200 Oe. The spatially-resolved magnetic force measurements of individual nanowires revealed the magnetic domain structure. The domains align perpendicular to c-axis and can be polarized in the external magnetic field.
Journal of Non-Crystalline Solids, 2001
Cobalt wires have been synthesized by electrodeposition in porous polycarbonate membranes with a pore diameter of % 200 nm and a thickness of % 6 lm. The in¯uence of the citrate concentration, and dierent substrates (Ag, Cu), sputtered on the bottom of membranes, on the nanocrystalline structure and magnetic properties of the wires are discussed. Crystallization of the wires as a function of the synthesis bath conditions was measured by X-ray diraction and the magnetic properties at room temperature were measured using vibrating-sample magnetometry. Dierences, on deposition rate and crystalline domains size, have been observed, as well as the coercive forces and the hysteresis squareness change in the hysteresis loops of the wires depending on the citrate concentration in the electrochemical bath.