Electrical transport and optical studies of ferromagnetic Cobalt doped ZnO nanoparticles exhibiting a metal-insulator transition

The observed correlation of oxygen vacancies and room temperature ferromagnetic ordering in Co doped ZnO1-o nanoparticles reported earlier (Naeem et al Nanotechnology 17, 2675-2680) has been further explored by transport and optical measurements. In these particles room temperature ferromagnetic ordering had been observed to occur only after annealing in forming gas. In the current work the optical properties have been studied by diffuse reflection spectroscopy in the UV-Vis region and the band gap of the Co doped compositions has been found to decrease with Co addition. Reflections minima are observed at the energies characteristic of Co+2 d-d (tethrahedral symmetry) crystal field transitions, further establishing the presence of Co in substitutional sites. Electrical transport measurements on palletized samples of the nanoparticles show that the effect of a forming gas is to strongly decrease the resistivity with increasing Co concentration. For the air annealed and non-ferromagnetic samples the variation in the resistivity as a function of Co content are opposite to those observed in the particles prepared in forming gas. The ferromagnetic samples exhibit an apparent change from insulator to metal with increasing temperatures for T>380K and this change becomes more pronounced with increasing Co content. The magnetic and resistive behaviors are correlated by considering the model by Calderon et al [M. J. Calderon and S. D. Sarma, Annals of Physics 2007 (Accepted doi: 10.1016/j.aop.2007.01.010] where the ferromagnetism changes from being mediated by polarons in the low temperature insulating region to being mediated by the carriers released from the weakly bound states in the higher temperature metallic region.Comment: 7 pages, 6 figure

Bacteriological and immunological study associated with patients of Urinary Bladder carcinoma

The blood, serum & urine samples are collected from (22) patients with urinary bladder cancer were admitted to Al-Hilla general teaching hospital after diagnosis by helping urology physician. The result appeared that E.coli with high percentage (22.7% ,27.2%)in nixed &single infection respectively followed by Ps.aeuroginosa (22.7% , 13.6%) and S.aureus (18.8% , 9.09%).   Interleukin 2 &Interleukin 8 concentration level was detected in serum by enzyme-linked immunosorbent assay(ELISA) and data were compared with control to compare the performance of each cytokins & results show no elevated , no significant decrease in level  in two cytokins, this leads  to an independent factors for the detection of urinary bladder cancer

Detection P53, Rb1 and H-ras Loss of Heterozygosity LOH in Patients with Urinary Bladder carcinoma

In this study 22 samples of urine sediments were obtained from patients with Urinary Bladder Carcinoma, DNA base technique and LOH detection was investigated in three genes P53, Rb1 and H-ras. The result are shown that LOH was present in most cases and for all genes where LOH in P53 represents (31.8%) and for Rb1 (45.4%) and for H-ras gene (27.2%).In some cases, more than one gene locus mutations were found

Magnetic response of core-shell cobalt ferrite nanoparticles at low temperature

Cobaltferritenanoparticles (size: 26±4nm) have been synthesized by coprecipitation route. The coercivity of nanoparticles follows a simple model of thermal activation of particle moments over the anisotropy barrier in the temperature range of 30–300K in accordance with Kneller’s law; however, at low temperatures

Ferromagnetism in Li doped ZnO nanoparticles: The role of interstitial Li

ZnO nanoparticles doped with Li (Zn1−yLiyO, y ≤ 0.1) have been investigated with emphasis on the correlation between their magnetic, electronic, and structural properties. In particular, defects such as interstitial Li and Zn atoms, substitutional Li atoms, and oxygen vacancies have been identified by X-ray photoelectron spectroscopy(XPS) and their respective roles in stabilization of the magnetic moment are discussed. X-ray diffraction(XRD) and XPS give clear evidence of Li presence at both substitutional and interstitial sites. XPS studies further show that the amount of substitutional Li defects (Lizn) and interstitial Li defects (Lii) vary non-monotonically with the Li concentration, with the Lii defects being noticeably high for the y = 0.02, 0.08, and 0.10 concentrations, in agreement with the XRD results. Magnetization studies show room temperature ferromagnetism in these nanoparticles with the moment being largest for the particles with high concentration of interstitial lithium and vice versa. Both interstitialZn(Zni) defects and Zn-O bonds were determined from the Zn LMM Auger peaks; however, the variation of these with Li concentrations was not large. Oxygen vacancies (Vo) concentrations are estimated to be relatively constant over the entire Li concentration range. We relate the Lii and Zni defects to the formation and stabilization of Znvacancies and thus stabilizing the p-type ferromagnetism predicted for cation (zinc)vacancy in the ZnO type oxides

Effect of Reducing Atmosphere on the Magnetism of Zn1-xCoxO Nanoparticles

We report the crystal structure and magnetic properties of Zn1-xCoxO nanoparticles synthesized by heating metal acetates in organic solvent. The nanoparticles were crystallized in wurtzite ZnO structure after annealing in air and in a forming gas (Ar95%+H5%). The X-ray diffraction and X-ray photoemission spectroscopy (XPS) data for different Co content show clear evidence for the Co+2 ions in tetrahedral symmetry, indicating the substitution of Co+2 in ZnO lattice. However samples with x=0.08 and higher cobalt content also indicate the presence of Co metal clusters. Only those samples annealed in the reducing atmosphere of the forming gas, and that showed the presence of oxygen vacancies, exhibited ferromagnetism at room temperature. The air annealed samples remained non-magnetic down to 77K. The essential ingredient in achieving room temperature ferromagnetism in these Zn1-xCoxO nanoparticles was found to be the presence of additional carriers generated by the presence of the oxygen vacancies.Comment: 11 pages, 6 figures, submitted to Nanotechnology IO