RESUMO
The application of transition metal hydroxides has long been plagued by its poor conductivity and stability as well as severe aggregation tendency. In this paper, a novel hierarchical core-shell architecture, using an F-doped Co(OH)2 nanorod array (Co(OH)F) as the core and Mn/Ni co-doped Co(OH)2 nanosheets (NiCoMn-LDH) as the shell, was constructed via an MOF-mediated in situ generation method. The obtained Co(OH)F@ NiCoMn-LDH composites exhibited excellent supercapacitive performance with large specific capacitance as well as improved rate capability and long-term stability. The effect of the Ni/Mn ratio on the supercapacitive performance and energy storage kinetics was systematically investigated and the related mechanism was revealed.
RESUMO
In this work, the facile fabrication of Co3O4 particles/reduced graphene oxide (Co3O4/rGO) composites on Indium tin oxide (ITO) slide was achieved by an electrophoretic deposition and annealing process. The deposition time and ratio of the precursors were optimized. Structural characterization and chemical composition investigation indicated successful loading of Co3O4 particles on graphene sheets. When applied as a non-enzymatic H2O2 sensor, Co3O4/rGO showed significant electrocatalytic activity, with a wide linear range (0.1-19.5 mM) and high sensitivity (0.2247 mA mM-1 cm-2). The good anti-interference ability, reproducibility, and long-term stability of the constructed sensor were also presented. The application of Co3O4/rGO in real sample analysis was evaluated in human urine sample with satisfactory results, indicating the feasibility of the sensor in physiological and medical applications.
RESUMO
A systematic study of polycrystalline La0.67Sr0.33MnO3 (LSMO) manganite coatings has been undertaken to analyse the effect of various particle sizes on the magnetic and electric transport properties. In order to acquire a series of samples with different particle sizes, the samples were prepared by a sol-gel method and were subjected to annealing at four different temperatures. With decreasing particle sizes, the magnetization decreases while the coercivity increases, which is attributed to the magnetically disordered surface layer. More attractively, the electrical transport properties can be systematically manipulated by particle sizes and so can the low field magnetoresistance (LFMR) values. Emphasis is placed on how the particle size affects the temperature dependence of resistivity, and three conduction models are explored to describe the transport behaviours in three temperature regions. A minimum resistivity is observed in the low temperature region in the presence and absence of a magnetic field, which can be mainly explained as due to the intergranular spin polarized tunneling (ISPT) through the grain boundaries (GBs) in polycrystalline materials.
