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Thangeeswari T.,VelTech Multitech Engineering College | Velmurugan J.,Anna University | Priya M.,Anna University
2014 International Conference on Science Engineering and Management Research, ICSEMR 2014 | Year: 2014

In this study, the equi molar mixing of selected divalent metal ions such as Ni, Pb and Cu with ZnO nano particles are prepared through decomposition of cationic acetate solid solution. The effects on the structural, compositional and optical properties are discussed. Simple solution- thermal method is suitable and more economical for large-scale production. The powder X- ray diffraction pattern of the equal amount of divalent metal ions mixed ZnO samples shows the mixed phases of the respective divalent metal oxides apart from the wurtzite ZnO peaks. Scanning electron microscope (SEM), Fourier Transform Infrared spectroscopy (FTIR), Thermo gravimetric analysis (TGA) and UV-visible spectrophotometry were employed to characterize the samples. From the study of FTIR spectroscopy, the Zn-O bonding is shifted towards the higher wave numbers on mixing Ni, Pb and Cu oxides with the ZnO nano particles. The absorption band of ZnO/NiO, ZnO/PbO, and ZnO/CuO mixed oxides are distinctly broadened and red-shifted indicating the strong interfacial interaction between ZnO and mixed oxides. The band gap of the nano particles can be tuned in the range of 2.7-3eV by the addition of divalent metal ions. © 2014 IEEE. Source


Thangeeswari T.,VelTech Multitech Engineering College | Thangeeswari T.,Anna University | Murugasen P.,Saveetha Engineering College | Velmurugan J.,Anna University
Journal of Superconductivity and Novel Magnetism | Year: 2015

Dysprosium-(Dy) and cobalt (Co)-doped zinc oxide (ZnO) nanoparticles with various concentrations have been synthesized by simple chemical precipitation method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray (EDAX) measurements were conducted respectively for the structural, morphological, and compositional investigation of the sample. XRD analysis indicated that diffraction peaks of all the samples can be indexed to the hexagonal wurtzite structure of ZnO. No secondary phases including Co and Dy ions were detected in the samples even for the highest doping concentrations of Dy. Average particle size is found to be 25–34 nm. Scanning electron microscope and transmission electron microscope analysis revealed that the dopant atoms of Co and Dy are homogeneously distributed in ZnO wurtzite structure. The samples were characterized by EDAX to confirm the expected stoichiometry. In the photoluminescence spectra, Dy co-doped samples show a violet emission along with a broad yellow emission due to the4F9/2–6H15/2 inner shell transitions of Dy3+ ion. The photoluminescence (PL) enhancement process in Dy co-doped ZnO:Co is mainly due to Dy as a sensibilizer which could effectively enhance the luminescence intensity. Absorption spectra of dysprosium- (Dy) and cobalt (Co)-doped ZnO nanoparticles exhibited enhanced optical absorption in visible region. Magnetization measurements have shown that the particles have room temperature ferromagnetic behavior with relatively high coercive fields which are decreasing with the increase of doping concentration. The analysis of optical and magnetic properties shows that Co- and Dy-doped ZnO nanoparticles are a promising material for DMS application and have potential applications in optoelectronic devices. © 2015, Springer Science+Business Media New York. Source


Pavithra S.,St Peters University | Rengarajan A.,VelTech Multitech Engineering College
IET Seminar Digest | Year: 2013

This paper presents a new idea in image segmentation algorithm driven by human visual system segmentation techniques and has been widely studied in the visual attention. The human eyes fixate at important locations in the scene, and every fixation point lies inside a particular region of arbitrary shape and size. we propose a method to segment the object of interest by finding the optimal closed contour around the fixation point in the polar space, The human visual system has two types of attention: overt attention (eye movements) and covert attention (without eye movement). For evaluating the segmentation result, from both region-based and boundary-based perspectives, are integrated into an objective function .Our approach can be complemented in a variety of ways, An interesting avenue has to do with learning models of the world. For example, if we had a model of a 'squirrel,' we could segment the 'squirrel,' more correctly in the region. Source


Thangeeswari T.,VelTech Multitech Engineering College | Velmurugan J.,Anna University | Priya M.,Saveetha Engineering College
International Journal of ChemTech Research | Year: 2015

Well crystalline Co-Bi co-doped ZnO nanostructures with various concentration of Bi were synthesized by simple chemical route technique using metal acetate precursors. Xray diffraction patterns of the pure and Co with Bi doped samples have shown the well crystalline diffraction peaks corresponds to the characteristic wurtzite ZnO crystal structure. Aggregated nano particles have emerged with flower like morphology and it can be seen from the scanning electron microscopy and transmission electron microscopy. The average particle diameter was estimated and found to be 25–35 nm. Tunable optical band gap related to an additional electron state created by dopant was observed from the UV–Visible spectra. Typical PL emission in the UV, visible and continuous deep level emission further demonstrates that the potential application of the material in optoelectronics. From this study it is suggested that this kind of excellent optical tunability of the Bi co-doped ZnO: Co system will be the potential material for future opto-electronic devices. © 2015, Sphinx Knowledge House. All rights reserved. Source


Thangeeswari T.,VelTech Multitech Engineering College | Thangeeswari T.,Anna University | Velmurugan J.,Anna University | Priya M.,Saveetha Engineering College
Journal of Materials Science: Materials in Electronics | Year: 2013

Well crystalline Co-Bi co-doped ZnO nanostructures with various concentration of Bi were synthesized by simple chemical precipitation technique using metal nitrate precursors. The structural and magnetic properties of the samples calcined at 300 C for 6 h has been studied comprehensively. X-ray diffraction patterns of the pure and Co-with Bi doped samples have shown the well crystalline diffraction peaks corresponds to the characteristic wurtzite ZnO crystal structure. Aggregated nano particles have emerged with flower like morphology and it can be seen from the scanning electron microscopy and transmission electron microscopy. The average particle diameter was estimated and found to be 25-35 nm. Tunable optical band gap related to an additional electron state created by dopant was observed from the UV-Visible spectra. Typical PL emission in the UV, visible and continuous deep level emission further demonstrates that the potential application of the material in optoelectronics. Excellent ferromagnetic features of the material at room temperature reveal the additional carrier induced exchange interaction could enhance the ferromagnetism in co-doped ZnO nanostructure. The addition of Bi at 3+ states can act as donor within the semiconductor which provides the additional electron charge carrier that could involve directly to the exchange interaction effectively at certain limit and enhances the ferromagnetism. At higher doping concentration the formation of diamagnetic Bi2O3 secondary phase have contributed to change the ferromagnetic behaviour of the sample. From this study it is suggested that this kind of combined ferromagnetism and excellent optical tunability of the Bi co-doped ZnO:Co system will be the potential material for future magneto-opto-electronic devices. © 2013 Springer Science+Business Media New York. Source

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