Enhanced spin Seebeck effect via oxygen manipulation.

Spin Seebeck effect (SSE) refers to the generation of an electric voltage transverse to a temperature gradient via a magnon current. SSE offers the potential for efficient thermoelectric devices because the transverse geometry of SSE enables to utilize waste heat from a large-area source by greatly simplifying the device structure. However, SSE suffers from a low thermoelectric conversion efficiency that must be improved for widespread application. Here we show that the SSE substantially enhances by oxidizing a ferromagnet in normal metal/ferromagnet/oxide structures. In W/CoFeB/AlOx structures, voltage-induced interfacial oxidation of CoFeB modifies the SSE, resulting in the enhancement of thermoelectric signal by an order of magnitude. We describe a mechanism for the enhancement that results from a reduced exchange interaction of the oxidized region of ferromagnet, which in turn increases a temperature difference between magnons in the ferromagnet and electrons in the normal metal and/or a gradient of magnon chemical potential in the ferromagnet. Our result will invigorate research for thermoelectric conversion by suggesting a promising way of improving the SSE efficiency.

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.