Search

Undersea optical communication (UOC) has been considered as the most potential next‐generation underwater wireless communication technology for ocean exploration. Photodetector is the essential component in UOC system, however, the harsh undersea environment like light attenuation and seawater corrosivity restricts the applications of conventional photodetectors. Herein, a novel natural‐electrolyte self‐powered photoelectrochemical (PEC) photodetector based on core‐shell structured Cu@GaN nanowires (NWs) network is demonstrated and direct utilization of seawater. High quality GaN shell is encapsulated on the Cu NWs network through Ga‐coating and high temperature nitridation processes. A Schottky junction along radial direction has formed at the Cu/GaN interface due to the outward diffusion of Cu into the GaN layer. Such a structure provides narrowed band detection on blue light as well as efficient carrier separation. A self‐powered undersea PEC photodetector is designed with a mini‐pipes connected device chamber, which allows direct indrawing of seawater and blue channel light communication (458 nm). This photodetector works stably for UOC in both shallow and deep‐sea conditions in Pacific Ocean area. It shows a high responsivity up to 5.04 mA W−1 and rapid response time of 0.68 ms. This photodetector can be easily integrated to marine equipment without waterproof packaging for the future energy‐saving UOC. [ABSTRACT FROM AUTHOR]

Hybrid piezo/triboelectric nanogenerators (H‐P/TENGs) are developed to compensate the drawbacks of a single nanogenerator by synergizing high triboelectric output voltage and piezoelectric output current in continuous contact‐separation cycles. In particular, piezoelectric zinc oxide (ZnO) has been widely used due to its excellent orientation along the c‐axis and tunable growth structures. Herein, various growth structures of ZnO, unoriented, oriented, and hierarchical structures, are incorporated in H‐P/TENGs, enhancing their power densities from 6 to 17 times. Particularly, oriented ZnO nanorod/PVA (ZnR) achieves a maximum power density of 15.9 W m−2 (≈17‐fold increment compared to pristine PVA). The highly oriented ZnO growth along the c‐axis enables large deformation upon a vertical compression, subsequently generating a large piezoelectric polarization. Moreover, the enhancement mechanism via piezoelectric polarization is elucidated using a modified overlapped electron cloud model supported with Kelvin probe force microscopy measurements. The polarization of ZnO nanocomposites enlarges the difference in the highest electron energies (ΔE) between the two triboelectric layers, driving more electrons to transfer during contact electrification, thereby enriching their surface charge densities. This study highlights the significance of growth structure control in maximizing the piezoelectric responses of ZnO, consequently improving the output performances of H‐P/TENGs. [ABSTRACT FROM AUTHOR]

Commonly, an elusive intermediate is generated from a precursor and then trapped and consumed in a reaction. Vinylidene ortho‐quinone methides (VQMs) have been demonstrated as transient axially chiral intermediates in asymmetric catalysis due to their orthogonal π‐bonds forming an allene motif. The current understanding of VQMs is primarily based on time‐resolved absorption, trapping experiments and computational studies. Herein, we report the first isolation and comprehensive characterization of a VQM, including crystallographic analysis. The disturbed aromaticity of the VQM led to its high reactivity as an electrophile or a 4π‐component capable of asymmetric dearomatization of an electron‐deficient phenyl group. Notably, the VQM could be isolated in enantiomerically enriched form, and the subsequent transformation was stereospecific, indicating that the generation of the VQM was involved in the enantiodetermining step. This study paves the way for the direct application of VQMs as starting materials. [ABSTRACT FROM AUTHOR]

Enantioselective construction of molecules bearing multiple stereogenic elements is increasingly related to the synthesis of enantiopure natural products, pharmaceuticals, and functional materials. However, atom‐economical and enantioselective approaches to install multiple stereogenic elements in a small molecular template by limited chemical transformation remain challenging. We describe an organocatalytic enantioselective method for the preparation of polychiral molecules bearing four types of stereogenic elements in fused azepines via vinylidene ortho‐quinone methide (VQM)‐mediated intramolecular electrophilic aromatic substitution. This method was proved robust with a wide range of substrate scope (46–92 % yield), with excellent diastereoselectivity (>20:1 dr) and enantioselectivity achieved (up to 97 % ee). Optical properties and Ru3+‐induced fluorescence responses of these compounds suggest their potential applications in optoelectronic materials and heavy metal ion detection. [ABSTRACT FROM AUTHOR]