Spatial separation of electrons and holes for enhancing the gas-sensing property of a semiconductor: ZnO/ZnSnO3 nanorod arrays prepared by a hetero-epitaxial growth.

The construction of semiconductor composites is known as a powerful method used to realize the spatial separation of electrons and the holes in them, which can result in more electrons or holes and increase the dispersion of oxygen ions ([Formula: see text] and O - ) (one of the most critical factors for their gas-sensing properties) on the surface of the semiconductor gas sensor. In this work, using 1D ZnO/ZnSnO3 nanoarrays as an example, which are prepared through a hetero-epitaxial growing process to construct a chemically bonded interface, the above strategy to attain a better semiconductor gas-sensing property has been realized. Compared with single ZnSnO3 nanotubes and no-matching ZnO/ZnSnO3 nanoarrays gas sensors, it has been proven by x-ray photoelectron spectroscopy and photoluminescence spectrum examination that the as-obtained ZnO/ZnSnO3 sensor showed a greatly increased quantity of active surface electrons with exceptional responses to trace target gases and much lower optimum working temperatures (less than about 170 °C). For example, the as-obtained ZnO/ZnSnO3 sensor exhibited an obvious response and short response/recovery time (less than 10 s) towards trace H2S gas (a detection limit down to 700 ppb). The high responses and dynamic repeatability observed in these sensors reveal that the strategy based on the as-presented electron and hole separation is reliable for improving the gas-sensing properties of semiconductors.

Cobalt-copper bimetallic selenides embedded in nitrogen-doped porous carbon nanocubes for diclofenac electrochemical sensing.

Diclofenac (DCF) is a non-steroidal anti-inflammatory drug (NSAID), and its overuse poses a potential threat to human health and the aquatic environment, designing high-efficiency electrocatalysts for DCF detection is urgent. Herein, cobalt-copper bimetallic selenides embedded in nitrogen-doped porous carbon nanocubes (CoCuSe@NC) were elaborately designed via one-step in situ selenization of bimetallic CoCu-MOF. The chemical constituents and micromorphology of CoCuSe@NC composites can be further optimized by precisely regulating the selenization process and the doping ratio of bimetal in MOF precursor. As an electrocatalyst, CoCuSe@NC was proved to be highly efficient in electrochemical sensing of DCF with a broad linear range of 0.1-400 µmol/L and a detection limit of 0.024 µmol/L. This was attributed to the synergistic advantages between the heterogeneous structures, which produced more electrochemically active sites, effectively shortened the electron transport path, and improved electrocatalytic performance. Consequently, the constructed sensor exhibits high sensitivity, remarkable stability and applicability, and in particular can selectively detect DCF from other structurally similar coexisting analogs, resulting from the unique metal chelation ability. This work paves the way for designing effective bimetallic selenide electrocatalysts and exploring their applications in DCF electrochemical sensing.