Papers by Keyword: Co²⁺

Abstract: The spin Hamiltonian parameters (SHPs, g factors and hyperfine structure constants) defect structure for LiMgPO₄ doped with 0.1% Co²⁺ at 4.2 K are theoretically investigated from the perturbation formulas of the SHPs for a rhombically distorted octahedral 3d⁷ cluster. The impurity Co²⁺ on host Mg²⁺ site is found to suffer the larger axial relative compression ratio ρ (≈ 0.76%) and the planar angular variation Δφ (≈ 6.64^°) related to the host oxygen octahedron due to size mismatch. The calculated SHPs based on the above defect structure show good agreement with the measured results. Present study can be helpful to the preparation and characterization for the local structures for transition-metal impurities in lithium-magnesium phosphate, which may is helpful to search for the phosphor materials with better dosimetric characteristics.

Abstract: The adsorption behaviors and mechanism of geopolymers based on metakaolin-fly ash for Sr²⁺, Co²⁺ and Cs⁺ were investigated in static method. The results showed that the geopolymer has a strong adsorbability for Sr²⁺, Co²⁺ and Cs⁺ and the adsorbances are mainly affected by ion concentration and pH value of the solution. The adsorption dynamic model of the material for Sr²⁺, Co²⁺ and Cs⁺ is confirmed to be the first-order reaction and the adsorption isotherm curves showed that the adsorption behaviors belong to monolayer adsorption which is simulated by the Langmuir model very well. Desorption of Sr²⁺, Co²⁺ and Cs⁺could be carried on by immersing the adsorbents in the solutions with low pH or high ionic strength solution. Desorption experiments and XRD analysis indicate that the adsorption behaviors of geopolymer for the three kinds of ions are mainly chemical adsorption, according to the ion-exchange mechanism.

Abstract: Chitosan and N,O-carboxymethyl chitosan are non-toxic natural absorbents. In this paper, the adsorbing behavior of Chitosan and O, N-carboxymethyl Chitosan for Co²⁺ respectively were studied. The result indicated that the adsorbing ability of N,O-carboxymethyl chitosan was better than this of chitosan. The adsorbing ratio increased clearly with the increasing in the pH value of solution and absorbent amount, but it was not sensitive to the concentration of Co²⁺. Within ten minutes, the adsorbing ratio of above absorbents could achieve above 80%. But with time prolonging, the adsorbing ratio increased slowly. When time was more than 15 minutes and the pH value was higher than 10, the adsorption rate slowly flatted out.

Abstract: Exploring an effective replacement material of bone transplantation to repair bone defect is the hot topic in bone defect therapy at present. The biomimetic materials will be the main dircetion. Chitosan, the N-deacetylated derivative of chitin, has been regarded as suitable materials because of its biocompatibility, biodegradability, reliability and wide sources, which is the next generation of promising materials for tissue engineering. This study introduce the best CoCl₂_-Chitosan-gel-sticks of different concentrations prepared by using the in-situ Precipitation Method and Alternate deposition Method. This investigation progeny will have a wide range of applications in biological materials field and other fields.

Abstract: Epigallocatechin gallate (EGCG), a major polyphenol of green tea, has been shown to inhibit the growth of various cancer cell lines. Co²⁺ is one of essential trace elements of human nutrition, both lack and excess have adverse effects on health.In this research, MTT assays were applied to investigate the effects of Co²⁺, EGCG and their coactions on Cal-27 cells, The results show that Co²⁺ and EGCG inhibited the growth of Cal-27 cells in a time-and dose-dependent model, and inhibition effects were extremely dependent on their concentrations, added orders and [Co²⁺]/[EGCG] ratio. Inhibitory effects of Co²⁺ could be decreased in the presence of EGCG. LC/MS analysis showed that a new component arised when EGCG and Co²⁺ were mixed together. It was inferred that the new components were [EGCG-2Co] and [EGCG-Co], and the process might be responsible for the observed effect of the bioactivities of Co²⁺ against Cal-27 cells.

Abstract: The EPR parameters and the local structure for Co2+ in ZnO are deduced from the perturbation formulas of these parameters for a 3d7 ion in a trigonally distorted tetrahedron. The ligand orbital and spin-orbit coupling contributions are taken into account uniformly from the cluster approach in view of the covalency of the system. The impurity V3+ is found not to locate exactly on the Zn2+ site but to experience a small displacement of 0.04 Ǻ away from the ligand triangle, along the C3 axis. The theoretical EPR parameters based upon the above impurity displacement are in good agreement with the observed values.

Abstract: The local structure and the spin Hamiltonian parameters g factors gi (i =x, y and z) and the hyperfine structure constants Ai for Co2+ in orthorhombic CaTiO3 are theoretically investigated from diagonalization of 6 × 6 energy matrix within the 4T1 ground state for a 3d7 ion in orthorhombic symmetry. In the calculations, the contributions from the admixtures of various J states (J=1/2, 3/2, 5/2), the ligand orbitals and spin-orbit coupling and the fourth-order orthorhombic field parameter, which were usually neglected in the previous works, are taken into account. The crystal-field parameters are determined from the superposition model in consideration of the suitable lattice distortion due to the charge and size mismatching substitution of Ti4+ by Co2+. Based on the studies, the bond lengths R1 and R2 in the xy plane are estimated to suffer the relative alternation R ≈ 5.4%, yielding more significant orthorhombic distortion in the impurity center as compared with that for the host Ti4+ site in pure crystal. The calculation results based on the above local lattice distortion show reasonable agreement with the observed values. The various contributions to the spin Hamiltonian parameters are discussed. Present studies may theoretically verify that the impurity Co2+ occupies the 6-fold coordinated Ti4+ site rather than the 12-fold coordinated Ca2+ site, associated with the enhanced orthorhombic distortion due to the mismatching substitution.

Abstract: The axial displacements for Co2+ and Ni3+ in Al2O3 are theoretically investigated starting from the perturbation formulas of the EPR parameters for a 3d7 ion with high spin (S=3/2) and low spin (S=1/2) in trigonal symmetry, respectively. Based upon these studies, the Co2+ is found to shift towards the center of the oxygen octahedron by an amount
ZCo (≈ 0.03 Å) along the C3 axis, while the Ni3+ may suffer another axial displacement
ZNi (≈ −0.38 Å) away from the center of the octahedron. The calculated EPR parameters based upon the above axial displacements show good agreement with the observed values. The differences in the EPR parameters and the axial displacements for the two 3d7 ions are discussed.