Increase Of Co Doping Concentration Research Articles

Antimicrobial, antioxidant, cytotoxicity and photocatalytic performance of Co doped ZnO nanoparticles biosynthesized using Annona Muricata leaf extract.

In the present study, ZnO nanoparticles doped with 3%, 5% and 7% of cobalt have been synthesized by green method using Annona muricata leaf extract. The obtained nanopowder was characterised by XRD, FTIR, XPS, HRTEM, SAED, SEM, EDAX and UV-Visible spectroscopy techniques. XRD patterns confirm the formation of pure and Co doped ZnO nanoparticles with a hexagonal wurtzite structure with high phase purity. FTIR spectra indicate the stretching vibration of Zn-O at 495cm-1. The incorporation of Co2+ ions into the ZnO lattice was identified by XPS analysis. EDX spectra confirm the existence of Co, Zn and O elements. The SEM and HRTEM micrographs show morphology of nanoparticles. The optical study specifies a decrease in energy band gap with an increase in Co-doping concentration. The photocatalytic performance of ZnO and Zn0.93Co0.07O has been examined for the degradation of methylene blue (MB) under sunlight irradiation. The antimicrobial activity of synthesized nanoparticles against s.aureus, p.aeruginosa, b.subtilis bacterial strains c.albicans and a.niger fungal strains as investigated. The Zn0.93Co0.07O nanoparticles exhibit good antioxidant properties. Moreover, the cytotoxicity of ZnO nanoparticles was evaluated against L929 normal fibroblast cells. So, this work suggests that Annona muricata leaf extract mediated pure and Co-doped ZnO nanoparticles are a potential candidate for biomedical and photocatalytic applications.

Fluorescence Emission and Ferromagnetic of Zn0.97−xNi0.03CoxS Nanorods Synthesized via a Hydrothermal Route

Wurtzite structure Ni and Co co-doped Zn0.97−xNi0.03CoxS (x = 0.01, 0.03 and 0.05) nanorods were successfully synthesized by a hydrothermal route with ethylenediamine. The effects of Co doping concentration on the crystal microstructure, morphology, optical and magnetic properties were systematically investigated by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive spectrometry (EDS), UV–visible spectra (UV–VIS), photoluminescence (PL) and a vibrating sample magnetometer (VSM). The morphology of as-prepared samples is one-dimensional wurtzite rod-like with good dispersion. It is demonstrated that the Ni and Co co-doped ZnS nanorods lead to an increased visible light absorption, slightly increased band gap, and decreased PL intensity. Blue shift of the band gap occurs in doped Zn0.97−xNi0.03CoxS nanorods. PL spectra shows an obvious ultraviolet emission peak at 375 nm and a weaker side band at 730 nm, implying the excellent single-phase ZnS. Notably, two major blue emissions band around 497 nm and 576 nm are quenched sharply with the increase of Co doping concentration. The CIE chromaticity diagram results show that the prepared Zn0.97−xNi0.03CoxS samples exhibit excellent light-emitting ability. All samples possess ferromagnetic behavior at room temperature. The saturation magnetization of Zn0.97−xNi0.03CoxS nanorods with an appropriate amount of Co decreases obviously, reaching a minimum at 3% Co.

Revealing the doping mechanism and effect of cobalt on the HTB-type iron fluoride: A first-principle study

FeF3 with a hexagonal-tungsten-bronze structure (HTB-FeF3) has been proposed as a promising cathode material with high theoretical specific capacity and voltage. However, it suffers from the drawbacks of poor Li kinetics and cycling life due to poor electrical conductivity. Moreover, its fundamental information, such as its geometrical structure, elastic properties and electronic structure, can rarely be found. Hence, first-principle calculations have been carried out to systematically investigate the effects of Co doping on the FeF3. We focus on CoxFe1-xF3 systems, in which x is equal to x = 0.08, 0.17 and 0.25, respectively. Firstly, the formation energies of CoxFe1-xF3 are obtained according to the elemental chemical potentials determined by the phase stability conditions. The calculated formation energies indicate that CoxFe1-xF3 can be synthesized under the F-rich growth conditions. Moreover, difficulty of Co doping FeF3 decreases with the increase of Co doping concentration. By analysis of the electronic structure of CoxFe1-xF3, it is found that the band gap of CoxFe1-xF3decreases remarkably and Co0.17Fe0.83F3 has the lowest band gap (0.993 eV), This phenomenon can be attributed to the Co-3d impurity energy levels occurring between valence band and conduction band. In order to further clarify the doping mechanism of Co on the FeF3, the elastic constants, bulk modulus and Debye temperature of FeF3 and Co0.17Fe0.83F3 are calculated. The results suggest that Co doping can help avoid particle fracture of FeF3 during charge/discharge cycling in the Li-ion batteries. Besides, it also can help us to further understand thermodynamic properties of FeF3 and Co0.17Fe0.83F3.

TG–DTA analysis, structural, optical and magnetic properties of PbS thin films doped with Co2+ ions

Cobalt-doped PbS (PbS:Co) thin films were grown on glass substrates via a cost effective spray technique using perfume atomizer. The effect of Co doping concentration on the thermal behavior, structural, optical and magnetic properties of PbS thin films was investigated and the results are reported in this paper. TG–DTA studies confirm that the thermal behavior of pure PbS is strongly influenced with Co doping. X-ray diffraction patterns reveal that both the undoped and doped PbS thin films exhibit face-centered cubic crystal structure with a strong (2 0 0) preferential growth texture. The increase of Co doping concentration tends to increase the band gap of pure PbS from 2.24 to 2.46 eV which may be attributed to quantum confinement effect. Undoped PbS thin film exhibit paramagnetic behavior at room temperature which becomes ferromagnetic with Co doping. From the results obtained it is observed that the PbS thin films doped with 3 wt% Co concentration exhibit better magnetic properties.

Influence of dopant on structural, optical and dielectric properties of Sn1−XCoxO2 nanoparticles

In this work, the optical and dielectric properties of Co doped SnO2 nanoparticles were studied using a.c. impedance spectroscopy. X-ray diffraction (XRD) confirmed that the Co doped SnO2 powder samples have the same tetragonal structure as pure SnO2 nanoparticles. The structural, surface morphological studies, compositional analyses and optical energy band gap were investigated by XRD, Scanning electron microscopy (SEM), Energy Dispersive X-ray Analysis (EDAX), and UV–Vis Spectroscopy. It is evident from the XRD result that annealed SnO2 samples exhibits tetragonal crystal structure with crystallite size ranging from 8 to 12 nm. The optical band gaps value of doped SnO2 nanoparticles were calculated to be in the range 5.33–5.8 eV. Impedance spectroscopy was carried out at room temperature in the frequency range of 100 kHz–14 MHz to explore the electrical properties of Sn1−xCoxO2 nanoparticles. For all the Co doped SnO2 samples prepared with Co content x ≤ 0.04, the SnO2 lattice contracts with the increasing dopant concentration. The dielectric constant, dielectric loss and a.c. electrical conductivity decrease with the increase in Co doping concentration. The decrease of dielectric constant and dielectric loss of the nanomaterial with respect to increasing frequency suggests that this nanomaterial can be employed in the fabrication of devices used at high-frequencies.

Influence of Co doping on combined photocatalytic and antibacterial activity of ZnO nanoparticles

The present work aims to investigate the structural, optical, photocatalyst and antibacterial properties of bare and cobalt doped ZnO nanoparticles (NPs) with different concentrations Zn1−xCoxO (x = 0, 0.03, 0.06 and 0.09) synthesized by co-precipitation method. The XRD patterns confirmed that all samples of cobalt doped ZnO nanostructures revealed the formation of single phase having hexagonal wurtzite structure with crystallite size in the range of 31–41 nm. Further, the decreasing trend in lattice parameters and grain sizes were also seen with increasing doping concentrations which confirms the incorporation of Co ions into the ZnO lattice. This result was further supported by the FT-IR data. HR-TEM images demonstrated the distinct hexagonal like morphology with small agglomeration. The UV–visible absorption spectra exhibits red shift with increase in Co doping concentration in ZnO while corresponding bandgap energy of cobalt doped ZnO NPs decreased with increased Co doping concentration. PL spectra showed a weak UV and visible emission band which may be ascribed to the reduction in oxygen vacancy and defects by cobalt doping. XPS and EDX spectral results confirm the composition and the purity of Co doped ZnO NPs. Furthermore, the Co doped ZnO NPs were found to exhibit lesser photocatalytic activity for the degradation of methyl green dye under UV light illumination in comparison with the bare ZnO NPs. Moreover, anti-bacterial studies reveals that the Co doped ZnO NPs possess more antibacterial effect against gram positive Basillus subtills and gram negative Klebsiella pneumoniae bacterial strains than the bare ZnO NPs.

Effect of cobalt concentration on morphology of Co-doped SnO2 nanostructures synthesized by solution combustion method

Cobalt (Co) doped SnO2 nanostructures were synthesized by solution combustion synthesis and structural and optical properties were investigated. The morphology of SnO2 nanostructure was changed from nanoflakes to nanospheres via nanorods and crystallite size was reduced from 4.7 nm to 2.7 nm as increase of Co doping concentration. The obvious diffraction peaks of X-ray diffraction and clear lattice fringes confirmed the formation of rutile phase of SnO2. The absorption edge transfers to upper wavelengths and energy bandgap was found to be decreasing by increase of Co concentration. The observed absorption band shows the characteristic band of d–d transitions of Co2+ ions in octahedral site symmetry. Vibrational spectroscopy shows the characteristic absorption peaks of Sn–O and confirms the incorporation of Co ions in SnO2 lattice.

Remarkable Magnetic Properties of Co-doped ZnO Nanorods Array at Room Temperature Originated from Vertical Growth on Zn Foil

Large-area arrays of highly oriented Co-doped ZnO nanorods with hexagonal structure were grown on Zn substrates by single-step hydrothermal process. Structure analysis indicates that the as-prepared products have wurtzite structure, and no other secondary phase is found in the nanorods. The intensity of UV emission peak decreases with the increase of Co doping concentration. When Co is doped into ZnO lattice, oxygen vacancies and Zn interstitials are created. The concentration of these defects increases with rise of the Co concentration. Magnetic measurement reveals that the Co doped ZnO nanorod arrays exhibit obvious room-temperature ferromagnetic behavior with a large coercive field H c of 52.8 kA/m, which makes them potentially useful as building components for spintronics.

Dielectric and magnetic properties of (Zn, Co) co-doped SnO2 nanoparticles**Project supported by the National Basic Research Program of China (Grant Nos. 2015CB921004, 2012CB821404, and 2011CBA00103) and the National Natural Science Foundation of China (Grant Nos. 11374261 and 11204059).

Polycrystalline samples of (Zn, Co) co-doped SnO2 nanoparticles were prepared using a co-precipitation method. The influence of (Zn, Co) co-doping on electrical, dielectric, and magnetic properties was studied. All of the (Zn, Co) co-doped SnO2 powder samples have the same tetragonal structure of SnO2. A decrease in the dielectric constant was observed with the increase of Co doping concentration. It was found that the dielectric constant and dielectric loss values decrease, while AC electrical conductivity increases with doping concentration and frequency. Magnetization measurements revealed that the Co doping SnO2 samples exhibits room temperature ferromagnetism. Our results illustrate that (Zn, Co) co-doped SnO2 nanoparticles have an excellent dielectric, magnetic properties, and high electrical conductivity than those reported previously, indicating that these (Zn, Co) co-doped SnO2 materials can be used in the field of the ultrahigh dielectric material, high frequency device, and spintronics.

English

We report the effect of cobalt doping on the structural, morphological, electrical and optical properties of nanocrystalline ZnO films febricated by chemical spray pyrolysis technique (CSPT). The structural studies reveal stronge c-axis orientated wurtzite structure. However with the increase in Co doping concentration ( at 5%), an inclination from (0 0 2) to (1 0 1) plane has been observed. This may be due to fact that, in addition to substitutional sites, Co may start to occupy interstitial sites due to the deformation of lattice structure caused by substitution of nearby Zn atoms by other Co atoms. Self-assembly of particles are clearly displayed in AFM images. The particle size and roughness of the films are found to decrease with the increase in Co doping percentage. Optical transmittance spectra showed red shift at higher doping. In addition to the band edge, absorption bands are also observed for all Co doped samples at 573nm, 606nm and 666 nm, which are attributed to d-d transitions of tetrahedrally coordinate Co 2+ . This is particularly important because Co 2+ doping in ZnO produce a significant red shift in band gap energy and, most importantly, the additional optical absorption bands could extend to the visible range of solar energy.

First principles study on the structural, magnetic and electronic properties of Co-doped FeF 3

To better understand the effects of Co-doping on the crystal and electronic structures of FeF 3, the theoretical studies of three types of doped models (CoFe 5F 18, Co 2Fe 4F 18, and Co 3Fe 3F 18) have been carried out by means of first principles method based on density functional theory. It is found that the stability of Co-doped FeF 3 decreases with the increase of Co-doping concentration. And Co doping does not impair the crystal structure of FeF 3, but it can make G-type anti-magnetic structure of FeF 3 convert into metamagnetism structure. Besides, the band gap of FeF 3 decreases via Co doping, and the conductivity of the Co doping FeF 3 compounds can be improved, thus indicating a high discharge specific capacity when the Co doping FeF 3 compounds are used as cathode material of lithium ion batteries.

Effect of Co substitution on magnetic properties of Sr 14Cu 24O 41

A series samples of Sr 14(Cu 1− x Co x ) 24O 41 ( x=0, 0.02, 0.06, 0.14, 0.18) were prepared by standard solid-state reaction. X-ray diffraction measurements show that all the samples are single phase and their lattice parameter hardly changes by Co dopant. Electron diffraction experiments and X-ray photo-emission spectroscopy measurements reveal that Co ions substituted Cu ions in the chain. The measurements of magnetic susceptibility from 10 to 300 K in an applied magnetic field of 1.0 T show that Co dopant induces increase in susceptibility. The spin gaps are observed in all the samples, and decrease with increase in Co doping concentration. Fitting of the date indicates that strong antiferromagnetic interaction is induced and antiferromagnetic dimeried state may be formed due to Co 3+ ions doping in these compounds.