We demonstrate a simple transistor based on the conducting polymer poly(3,4-ethylene dioxythiophene)/poly(styrene sulfonic acid), capable of sensing glucose in a neutral pH buffer solution by a mechanism involving sensing of hydrogen peroxide.

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Topological insulators (TIs) have been found in strained binary HgTe and ternary I-III-VI 2 chalcopyrite compounds such as CuTlSe 2 which have inverted band structures. However, the nontrivial band gaps of these existing binary and ternary TIs are limited to small values, usually around 10 meV or less. In this work, we reveal that a large non-trivial band gap requires the material having a large negative crystal field splitting ∆ CF at top of the valence band and a moderately large negative s − p band gap E s−p g . These parameters can be better tuned through chemical ordering in multinary compounds. Based on this understanding, we show that a series of quaternary I 2 -II-IV-

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Deep-sea polymetallic sulfides associated with hydrothermal systems are considered a potential viable resource for base and precious metals. The Southwest Indian Ridge (SWIR, Indian Ocean) hosts active and inactive hydrothermal systems. Inactive hydrothermal fields are more abundant than active fields but are difficult to remotely characterize. We report a deep-sea self-potential investigation to locate inactive ore deposits at the Yuhuang hydrothermal field on the ultraslow-spreading SWIR. A horizontal array of six nonpolarizing AgCl electrodes are attached to a deep-towed transient electromagnetic system to record the electrical field at a height of 40 m above the seafloor. The observed electrical field strength near a previously recognized sulfide deposits (verified by drilling) reaches an amplitude of 0.5 mV/m. Negative self-potential anomalies (~−27 mV) were observed by integrating the measured electrical field. The high electrical conductivities (up to 12 S/m) of sulfide samples measured in the laboratory and the oxidized sulfides recovered from the surface of the deposit suggest that the self-potential anomalies are due to sulfide mineralization and corrosion of the polymetallic sulfides. Inversion of the self-potential data reveals a localized body with a thickness of~65 m, which is interpreted as the Yuhuang ore deposit. Our field data demonstrate that the self-potential method is a useful exploration method to identify and image seafloor massive sulfide deposits hosted in inactive hydrothermal fields at mid-ocean ridges.

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