Rambabu Kuchi

Large-scale room-temperature aqueous synthesis of Co superstructures with controlled morphology, and their application to electromagnetic wave absorption

In this work, we report on the large-scale room-temperature synthesis of Co superstructures using a facile liquid phase reduction method in an aqueous medium. This method yielded pure Co powders within a short period of time without the use of any surfactants. The morphological changes in the Co superstructures could be controlled simply by varying the amounts of reducing agent (hydrazine hydrate). The morphology of the Co powders systematically controlled from aggregated foliage to isolated microfoliage by increasing the hydrazine hydrate addition from 4 ml to 8 ml. The morphology-dependent electromagnetic properties, including the electric permittivity, and magnetic permeability, were investigated over the microwave frequency range, 2-18 GHz. Co isolated microfoliage showed a maximum reflection loss (RL) of -32 dB at 9 GHz with a matching thickness of 2.5 mm, whereas the aggregated foliage Co superstructures displayed a maximum RL of -17 dB at 11 GHz with a matching thickness of 2.5 mm. The stronger absorption for isolated microfoliage was ascribed to a continuous micro networks and vibrating microcurrent dissipation arise from size and shape of the isolated microfoliage. The calculated RL suggested that the as-prepared samples were potential microwave absorption candidates in the X-band region.

Precise Determination of the Temperature Gradients in Laser-irradiated Ultrathin Magnetic Layers for the Analysis of Thermal Spin Current

We investigated the temperature distribution induced by laser irradiation of ultrathin magnetic films by applying a finite element method (FEM) to the finite difference time domain (FDTD) representation for the analysis of thermal induced spin currents. The dependency of the thermal gradient (∇T) of ultrathin magnetic films on material parameters, including the reflectivity and absorption coefficient were evaluated by examining optical effects, which indicates that reflectance (R) and the apparent absorption coefficient (α*) play important roles in the calculation of ∇T for ultrathin layers. The experimental and calculated values of R and α* for the ultrathin magnetic layers irradiated by laser-driven heat sources estimated using the combined FDTD and FEM method are in good agreement for the amorphous CoFeB and crystalline Co layers of thicknesses ranging from 3~20 nm. Our results demonstrate that the optical parameters are crucial for the estimation of the temperature gradient induced by laser illumination for the study of thermally generated spin currents and related phenomena.

Development of an Fe3O4@Cu silicate based sensing platform for the electrochemical sensing of dopamine

Abnormal levels of dopamine (DA) in body fluids is an indication of serious health issues, hence development of highly sensitive platforms for the precise detection of DA is highly essential. Herein, we demonstrate an Fe3O4@Cu silicate based electrochemical sensing platform for the detection of DA. Morphology and BET analysis shows the formation of ∼320 nm sized sea urchin-like Fe3O4@Cu silicate core–shell nanostructures with a 174.5 m2 g−1 surface area. Compared to Fe3O4 and Fe3O4@SiO2, the Fe3O4@Cu silicate urchins delivered enhanced performance towards the electrochemical sensing of DA in neutral pH. The Fe3O4@Cu silicate sensor has a 1.37 μA μM−1 cm−2 sensitivity, 100–700 μM linear range and 3.2 μM limit of detection (LOD). In addition, the proposed Fe3O4@Cu silicate DA sensor also has good stability, selectivity, reproducibility and repeatability. The presence of Cu in Fe3O4@Cu silicate and the negatively charged surface of the Cu silicate shell play a vital role in achieving high selectivity and sensitivity during DA sensing. The current investigation not only represents the development of a highly selective DA sensor but also directs towards the possibility for the fabrication of other Cu silicate based core–shell nanostructures for the precise detection of DA.