Strain-Reduced Inversion Symmetry in Ultrathin SnPSe Crystals for Giant Bulk Piezophotovoltaic Generation.

With the potential to surpass the Shockley-Queisser (S-Q) limitation for solar energy conversion, the bulk photovoltaic (BPV) effect, which is induced by the broken inversion symmetry of the lattice, presents prospects for future light-harvesting technologies. However, the development of BPV is largely limited by the low solar spectrum conversion efficiency of existing noncentrosymmetric materials with wide band gaps. This study reports that the strain-induced reduction of inversion symmetry can enhance the second-order nonlinear susceptibility (χ) of SnPSe crystals by an order of magnitude, which contributes to an extremely high value of 1.

Orientation-Related Giant Photothermoelectric Energy Conversion in Quasi-One-Dimensional van der Waals TaSe Crystals.

Featuring the capabilities of self-power, low dark current, and broadband response, photothermoelectric (PTE) detection demonstrates great potential for application in the military and civilian fields. The development of materials with an intrinsically high efficiency for PTE energy conversion and the in-depth study of its thermoelectric properties on the device performance are of great significance. Here, we reported a quasi-one-dimensional (quasi-1D) van der Waals (vdW) TaSe crystal as a promising material candidate for PTE detection.

Orientation-Selective Memory Switching in Quasi-1D NbSe Neuromorphic Device for Omnibearing Motion Detection.

Intelligent neuromorphic hardware holds considerable promise in addressing the growing demand for massive real-time data processing in edge computing. Resistive switching materials with intrinsic anisotropy and a compact design of non-volatile memory devices with the capability of handling spatiotemporally reconstructed data is crucial to perform sophisticated tasks in complex application scenarios. In this study, an anisotropic resistive switching cell with a planar configuration based on lithiated NbSe nanosheets is demonstrated.

A small library of copper-based metallenes with superior antibacterial activity.

We report the preparation of a small library of copper-based metallenes, such as copperene, brassene, bronzene, cupronickelene and AlCuZn trimetallene, a cryo-pretreatment assisted liquid phase exfoliation method. To the best of our knowledge, these nanosheets may represent a new category of metallenes. Benefiting from mixed-valence copper-induced oxidative stress and cleavage effects of layered structures, the obtained metallenes could efficiently eliminate drug-resistant bacteria even at a concentration as low as 1 μg mL.

Phase Transformation on Multilayer 2M-WS for Improved Surface-enhanced Raman Scattering.

In recent years, two-dimensional (2D) transition metal dichalcogenides (TMDCs) have been widely recognized as an ideal platform for surface-enhanced Raman scattering (SERS). Given their rich structural phases, phase transformation in 2D TMDCs is an efficient strategy to tailor their SERS performance. In this paper, we present the great SERS performance of multilayer 2M-WS and then investigate the effect of its phase transformation on SERS performance.

Stacking Faults Enabled Second Harmonic Generation in Centrosymmetric van der Waals RhI.

Second harmonic generation (SHG) in van der Waals (vdW) materials has garnered significant attention due to its potential for integrated nonlinear optical and optoelectronic applications. Stacking faults in vdW materials are a typical kind of planar defect that introduces a degree of freedom to modulate the crystal symmetry and resultant SHG response. However, the physical origin and tunability of stacking-fault-governed SHG in vdW materials remain unclear.

Out-of-plane Emission Dipole of Second Harmonic Generation in Odd- and Even-layered vdWs Janus NbSeI.

Integration of atomically thin nonlinear optical (NLO) devices demands an out-of-plane (OP) emission dipole of second harmonic generation (SHG) to enhance the spontaneous emission for nanophotonics. However, the research on van der Waals (vdWs) materials with an OP emission dipole of SHG is still in its infancy. Here, by coupling back focal plane (BFP) imaging with numerical simulations and density functional theory (DFT) calculations, we demonstrate that vdWs Janus NbSeI, ranging from bulk to the monolayer limit, exhibits a dominant OP emission dipole of SHG owing to the breaking of the OP symmetry.

Nanoskiving of van der Waals Materials toward Edge/Basal Plane Contact Heterojunctions for High-Performance Photodetection.

The unique features of edges in van der Waals materials may lead to edge-basal plane contacts that could provide new opportunities for electronic and optoelectronic devices. However, few studies have addressed edge/basal plane contact heterojunctions owing to the formidable challenges in integrating edges with the basal plane to form a heterojunction. Here, taking the example of black phosphorus (BP)/ReS, a heterojunction with contact between the edge and the basal plane was successfully achieved by the introduction of a nanoskiving technique to fabricate BP edges with controlled orientation, followed by the dry transfer of a ReS flake.

Intercorrelated Ferroelectricity and Bulk Photovoltaic Effect in Two-Dimensional SnPS Semiconductor for Polarization-Sensitive Photodetection.

A two-dimensional (2D) ferroelectric semiconductor, which is coupled with photosensitivity and room-temperature ferroelectricity, provides the possibility of coordinated conductance modulation by both electric field and light illumination and is promising for triggering the revolution of optoelectronics for monolithic multifunctional integration. Here, we report that semiconducting SnPS crystals can be achieved in a 2D morphology using a chemical vapor transport approach with the assistant of space confinement and experimentally demonstrate the robust ferroelectricity in atomic-thin SnPS nanosheet at room temperature. The intercorrelated programming of ferroelectric order along out-of-plane (OOP) and in-plane (IP) directions enables a tunable bulk photovoltaic (BPV) effect through multidirectional electrical control.

Neuro-inspired optical sensor array for high-accuracy static image recognition and dynamic trace extraction.

Neuro-inspired vision systems hold great promise to address the growing demands of mass data processing for edge computing, a distributed framework that brings computation and data storage closer to the sources of data. In addition to the capability of static image sensing and processing, the hardware implementation of a neuro-inspired vision system also requires the fulfilment of detecting and recognizing moving targets. Here, we demonstrated a neuro-inspired optical sensor based on two-dimensional NbS/MoS hybrid films, which featured remarkable photo-induced conductance plasticity and low electrical energy consumption.

Defect Emission and Its Dipole Orientation in Layered Ternary Znln S Semiconductor.

Defect engineering is promising to tailor the physical properties of 2D semiconductors for function-oriented electronics and optoelectronics. Compared with the extensively studied 2D binary materials, the origin of defects and their influence on physical properties of 2D ternary semiconductors are not clarified. Here, the effect of defects on the electronic structure and optical properties of few-layer hexagonal Znln S is thoroughly studied via versatile spectroscopic tools in combination with theoretical calculations.

Formulating N-Doped Carbon Hollow Nanospheres with Highly Accessible Through-Pores to Isolate Fe Single-Atoms for Efficient Oxygen Reduction.

It is challenging yet promising to design highly accessible N-doped carbon skeletons to fully expose the active sites inside single-atom catalysts. Herein, mesoporous N-doped carbon hollow spheres with regulatable through-pore size can be formulated by a simple sequential synthesis procedure, in which the condensed SiO is acted as removable dual-templates to produce both hollow interiors and through-pores, meanwhile, the co-condensed polydopamine shell is served as N-doped carbon precursor. After that, Fe─N─C hollow spheres (HSs) with highly accessible active sites can be obtained after rationally implanting Fe single-atoms.

Revisiting the Hetero-Interface of Electrolyte/2D Materials in an Electric Double Layer Device.

Electric double layer (EDL) devices based on 2D materials have made great achievements for versatile electronic and opto-electronic applications; however, the ion dynamics and electric field distribution of the EDL at the electrolyte/2D material interface and their influence on the physical properties of 2D materials have not been clearly clarified. In this work, by using Kelvin probe force microscope and steady/transient optical techniques, the character of the EDL and its influence on the optical properties of monolayer transition metal dichalcogenides (TMDs) are probed. The potential drop, unscreened EDL potential distribution, and accumulated carriers at the electrolyte/TMD interface are revealed, which can be explained by nonlinear Thomas-Fermi theory.

Synaptic plasticity realized by selective oxidation of TiS nanosheet for neuromorphic devices.

Memristive devices operating analogous to biology synapses demonstrate great potential for neuromorphic applications. Here, we reported the space-confined vapor synthesis of ultrathin titanium trisulfide (TiS) nanosheets, and subsequent laser manufacturing of a TiS-TiO-TiS in-plane heterojunction for memristor applications. Due to the flux-controlled migration and aggregation of oxygen vacancies, the two-terminal memristor demonstrates reliable "analog" switching behaviors, in which the channel conductance can be incrementally adjusted by tuning the duration and sequence of programming voltage.

Two-dimensional semiconducting SnPSe with giant second-harmonic-generation for monolithic on-chip electronic-photonic integration.

Two-dimensional (2D) layered semiconductors with nonlinear optical (NLO) properties hold great promise to address the growing demand of multifunction integration in electronic-photonic integrated circuits (EPICs). However, electronic-photonic co-design with 2D NLO semiconductors for on-chip telecommunication is limited by their essential shortcomings in terms of unsatisfactory optoelectronic properties, odd-even layer-dependent NLO activity and low NLO susceptibility in telecom band. Here we report the synthesis of 2D SnPSe, a van der Waals NLO semiconductor exhibiting strong odd-even layer-independent second harmonic generation (SHG) activity at 1550 nm and pronounced photosensitivity under visible light.

Self-Sacrificing Template Synthesis of Carbon Nanosheets Assembled Hollow Spheres with Abundant Active Fe-N O Moieties for Electrocatalytic Oxygen Reduction.

Single-atom Fe-N-C (Fe -N-C) materials represent the benchmarked electrocatalysts for oxygen reduction reaction (ORR). However, single Fe atoms in the carbon skeletons cannot be fully utilized due to the mass transfer limitation, severely restricting their intrinsic ORR properties. Herein, a self-sacrificing template strategy is developed to fabricate ultrathin nanosheets assembled Fe -N-C hollow microspheres (denoted as Fe /N-HCMs) by rational carbonization of Fe chelating polydopamine coated melamine cyanuric acid complex.

A polarization-sensitive photothermoelectric photodetector based on mixed-dimensional SWCNT-MoS heterostructures.

Mixed-dimensional van der Waals (vdW) integration has been demonstrated to be effective for the modulation of the physical properties of homogeneous materials. Herein, we reported the enhancement of photothermal conversion and decrease of thermal conductivity in metallic single-walled carbon nanotube (SWCNT) films with the integration of chemical vapor deposition-grown monolayer MoS films. The induced temperature gradient in SWCNT-MoS hybrid films drives carrier diffusion to generate photocurrent the photothermoelectric (PTE) effect, and a self-powered photodetector working in the visible band range from 405 to 785 nm was demonstrated.

Isolating Fe Atoms in N-Doped Carbon Hollow Nanorods through a ZIF-Phase-Transition Strategy for Efficient Oxygen Reduction.

Transition metal-nitrogen-carbon (TM-N-C) catalysts have been intensely investigated to tackle the sluggish oxygen reduction reactions (ORRs), but insufficient accessibility of the active sites limits their performance. Here, by using solid ZIF-L nanorods as self-sacrifice templates, a ZIF-phase-transition strategy is developed to fabricate ZIF-8 hollow nanorods with open cavities, which can be subsequently converted to atomically dispersed Fe-N-C hollow nanorods (denoted as Fe -N-C HNRs) through rational carbonization and following fixation of iron atoms. The microstructure observation and X-ray absorption fine structure analysis confirm abundant Fe-N active sites are evenly distributed in the carbon skeleton.

Bifunctional WC-Supported RuO Nanoparticles for Robust Water Splitting in Acidic Media.

We report the strong catalyst-support interaction in WC-supported RuO nanoparticles (RuO -WC NPs) anchored on carbon nanosheets with low loading of Ru (4.11 wt.%), which significantly promotes the oxygen evolution reaction activity with a η of 347 mV and a mass activity of 1430 A g , eight-fold higher than that of commercial RuO (176 A g ).

2D Indium Phosphorus Sulfide (In P S ): An Emerging van der Waals High-k Dielectrics.

2D van der Waals (vdW) semiconductors hold great potentials for more-than-Moore field-effect transistors (FETs), and the efficient utilization of their theoretical performance requires compatible high-k dielectrics to guarantee the high gate coupling efficiency. The deposition of traditional high-k dielectric oxide films on 2D materials usually generates interface concerns, thereby causing the carrier scattering and degeneration of device performance. Here, utilizing a space-confined epitaxy growth approach, the authors successfully obtained air-stable ultrathin indium phosphorus sulfide (In P S ) nanosheets, the thickness of which can be scaled down to monolayer limit (≈0.

Mechanical Anisotropy in Two-Dimensional Selenium Atomic Layers.

Two-dimensional (2D) trigonal selenium (-Se) has become a new member in 2D semiconducting nanomaterial families. It is composed of well-aligned one-dimensional Se atomic chains bonded via van der Waals (vdW) interaction. The contribution of this unique anisotropic nanostructure to its mechanical properties has not been explored.