Enhanced Photodetection Performance of InBiSe3/ReS2 Polarization-Sensitive Heterostructure Photodetectors.

Individual anisotropic two-dimensional (2D) materials have been widely applied for developing polarization-sensitive photodetectors, but they often suffer from limitations in photoresponsivity, detection range, etc. To overcome these challenges, van der Waals (vdW) heterostructures created by stacking different 2D materials provide a promising solution to enhance the performance of the photoelectronic device. In this work, a novel polarization-sensitive photodetector is developed by leveraging a heterojunction formed by InBiSe3 and anisotropic ReS2 nanoflakes. The InBiSe3/ReS2 vdW heterostructure devices exhibit excellent photodetection performance with a high photoresponsivity (R) of 7.68 A W-1 and a specific detectivity (D*) up to 1.26 × 1011 Jones as well as an external quantum efficiency (EQE) of 1790% under 532 nm laser irradiation. Additionally, benefiting from the broadband light absorption of InBiSe3 crystals together with the pronounced anisotropic electronic and optical characteristics of ReS2 flakes, the devices demonstrate a broad spectral response range from 402 to 1006 nm with a distinct polarization sensitivity of 1.24. Moreover, the devices exhibit extraordinary optical communication and high contrast polarimetric imaging capacity. This work demonstrates the enhanced photodetection performance with the InBiSe3/ReS2 vdW heterostructures operating in a photoconductive mode and illustrates promising application of these heterostructures in integrated optoelectronic systems.

The Nonvolatile Memory and Neuromorphic Simulation of ReS2/h-BN/Graphene Floating Gate Devices Under Photoelectrical Hybrid Modulations.

The floating gate devices, as a kind of nonvolatile memory, obtain great application potential in logic-in-memory chips. The 2D materials have been greatly studied due to atomically flat surfaces, higher carrier mobility, and excellent photoelectrical response. The 2D ReS2 flake is an excellent candidate for channel materials due to thickness-independent direct bandgap and outstanding optoelectronic response. In this paper, the floating gate devices are prepared with the ReS2/h-BN/Gr heterojunction. It obtains superior nonvolatile electrical memory characteristics, including a higher memory window ratio (81.82%), tiny writing/erasing voltage (±8 V/2 ms), long retention (>1000 s), and stable endurance (>1000 times) as well as multiple memory states. Meanwhile, electrical writing and optical erasing are achieved by applying electrical and optical pulses, and multilevel storage can easily be achieved by regulating light pulse parameters. Finally, due to the ideal long-time potentiation/depression synaptic weights regulated by light pulses and electrical pulses, the convolutional neural network (CNN) constructed by ReS2/h-BN/Gr floating gate devices can achieve image recognition with an accuracy of up to 98.15% for MNIST dataset and 91.24% for Fashion-MNIST dataset. The research work adds a powerful option for 2D materials floating gate devices to apply to logic-in-memory chips and neuromorphic computing.

Incorporating ReS2 Nanosheet into ZnIn2S4 Nanoflower as Synergistic Z-Scheme Photocatalyst for Highly Effective and Stable Visible-Light-Driven Photocatalytic Hydrogen Evolution and Degradation.

Inspired by natural photosynthesis, the visible-light-driven Z-scheme system is very effective and promising for boosting photocatalytic hydrogen production and pollutant degradation. Here, a synergistic Z-scheme photocatalyst is constructed by coupling ReS2 nanosheet and ZnIn2S4 nanoflower and the experimental evidence for this direct Z-scheme heterostructure is provided by X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and electron paramagnetic resonance. Consequently, such a unique nanostructure makes this Z-scheme heterostructure exhibit 23.7 times higher photocatalytic hydrogen production than that of ZnIn2S4 nanoflower. Moreover, the ZnIn2S4/ReS2 photocatalyst is also very stable for photocatalytic hydrogen evolution, almost without activity decay even storing for two weeks. Besides, this Z-scheme heterostructure also exhibits superior photocatalytic degradation rates of methylene blue (1.7 × 10-2 min-1) and mitoxantrone (4.2 × 10-3 min-1) than that of ZnIn2S4 photocatalyst. The ultraviolet-visible absorption spectra, transient photocurrent spectra, open-circuit potential measurement, and electrochemical impedance spectroscopy reveal that the superior photocatalytic performance of ZnIn2S4/ReS2 heterostructure is mostly attributed to its broad and strong visible-light absorption, effective separation of charge carrier, and improved redox ability. This work provides a promising nanostructure design of a visible-light-driven Z-scheme heterostructure to simultaneously promote photocatalytic reduction and oxidation activity.

Improving the coverage area and flake size of ReS2through machine learning in APCVD.

Machine learning is playing a crucial role in optimizing material synthesis, particularly in scenarios where several parameters related to growth exhibit different and significant outcomes. An example of such complexity is the growth of atomically thin semiconductors through chemical vapor deposition (CVD), where multiple parameters can influence the thermodynamics and reaction kinetics involved in the synthesis. Herein, we performed a set of orthogonal experiments, varying the key parameters such as temperature, carries gas flux and precursor position to identify the optimal conditions for maximizing covered area and the size of rhenium disulfide (ReS2) crystals. The experimental results were used to establish correlations among the three thermodynamic variables through an artificial neural network. Contour plots were then generated to visualize the impact on the coverage and flake size of the crystals. This study demonstrates the capability of machine learning to enhance the potential of CVD-growth for the integration of 2D semiconductors like ReS2at larger scales.

Anisotropic sensing based on single ReS2flake for VOCs discrimination.

Selective and sensitive detection of volatile organic compounds (VOCs) holds paramount importance in real-world applications. This study proposes an innovative approach utilizing a single ReS2field-effect transistor (FET) characterized by distinct in-plane anisotropy, specifically tailored for VOC recognition. The unique responses of ReS2, endowed with robust in-plane anisotropic properties, demonstrate significant difference along thea-axis andb-axis directions when exposed to four kinds of VOCs: acetone, methanol, ethanol, and IPA. Remarkably, the responses of ReS2were significantly magnified under ultraviolet (UV) illumination, particularly in the case of acetone, where the response amplified by 10-15 times and the detection limit decreasing from 70 to 4 ppm compared to the dark conditions. Exploiting the discernible variances in responses along thea-axis andb-axis under both UV and dark conditions, the data points of acetone, ethanol, methanol and IPA gases were clearly separated in the principal component space without any overlap through principal component analysis, indicating that the single ReS2FET has a high ability to distinguish various gas species. The exploration of anisotropic sensing materials and light excitation strategies can be applied to a broad range of sensing platforms based on two-dimensional materials for practical applications.

Ternary ReS2(1-x)Se2xalloys of different composition for Q-switched and mode-locked all-fiber laser.

This paper systematically studied the composition-controlled nonlinear optical properties and pulse modulation of ternary ReS2(1-x)Se2xalloys for the first time. The compositionally modulated characteristics of ReS2(1-x)Se2xon the band gap were simulated based on the first principles. We investigated the effect of the band gap on the saturable absorption properties. In addition, we demonstrated the modulation characteristics of different components ReS2(1-x)Se2xon 1.5µm Q-switched pulse performance. The Q-switched threshold, repetition rate, and pulse duration increase as the S(sulfur)-element composition rise. And pulse energy also was affected by the S(sulfur)-element composition. The ReS0.8Se1.2SA was selected to realize a conventional soliton with high energy in the all-fiber mode-locked laser. The pulse was centered at 1562.9 nm with a pulse duration of 2.26 ps, a repetition rate of 3.88 MHz, and maximum pulse energy of 1.95 nJ. This work suggests that ReS2(1-x)Se2xhas great potential in laser technology and nonlinear optics, and widely extends the material applications in ultrafast photonics.

Sensitive detection of uric acid based on low-triggering-potential cathodic luminol electrochemiluminescence achieved by ReS2 nanosheets.

The majority of previously reported cathodic electrochemiluminescence (ECL) systems often required very negative potential to be carried out, which has greatly limited their applications in the sensing field. Screening high-performance cathodic ECL systems with low triggering potential is a promising way to broaden their applications. In this work, rhenium disulfide nanosheets (ReS2 NS) have been revealed as an efficient co-promoter to realize low-triggering-potential cathodic luminol ECL. One strong cathodic ECL signal appeared at a potential of -0.3 V and one anodic ECL peak was obtained at -0.15 V under the reverse potential scan, which were caused by electrogenerated reactive oxygen species (ROS) from hydrogen peroxide. The generation of strong luminol ECL at low potential was the result of the electrocatalytic effect of ReS2 NS on the reduction of H2O2. The scavenging effect of uric acid (UA) on the ROS could significantly inhibit the cathodic ECL. As a result, an ECL sensor was proposed, which showed outstanding performance for the detection of UA in the range of 10 nM to 0.1 mM with a low detection limit of 1.53 nM. Moreover, the ECL sensor was successfully applied in the sensitive detection of UA in real samples. This work provides a new avenue to establish a low-potential cathodic ECL system, which will sufficiently expand the potential application of cathodic ECL in the sensing field.

Identifying, Resolving, and Quantifying Anisotropy in ReS2 Nanomechanical Resonators.

As an emerging two-dimensional semiconductor, rhenium disulfide (ReS2 ) is renowned for its strong in-plane anisotropy in electrical, optical, and thermal properties. In contrast to the electrical, optical, optoelectrical, and thermal anisotropies that are extensively studied in ReS2 , experimental characterization of mechanical properties has largely remained elusive. Here, it is demonstrated that the dynamic response in ReS2 nanomechanical resonators can be leveraged to unambiguously resolve such disputes. Using anisotropic modal analysis, the parameter space for ReS2 resonators in which mechanical anisotropy is best manifested in resonant responses is determined. By measuring their dynamic response in both spectral and spatial domains using resonant nanomechanical spectromicroscopy, it is clearly shown that ReS2 crystal is mechanically anisotropic. Through fitting numerical models to experimental results, it is quantitatively determined that the in-plane Young's moduli are 127 and 201 GPa along the two orthogonal mechanical axes. In combination with polarized reflectance measurements, it is shown that the mechanical soft axis aligns with the Re-Re chain in the ReS2 crystal. These results demonstrate that dynamic responses in nanomechanical devices can offer important insights into intrinsic properties in 2D crystals and provide design guidelines for future nanodevices with anisotropic resonant responses.

Modulating the Function of GeAs/ReS2 van der Waals Heterojunction with its Potential Application for Short-Wave Infrared and Polarization-Sensitive Photodetection.

Van der Waals heterojunction (vdWs) of 2D materials with integrated or extended superior characteristics, opening up new opportunities in functional electronic and optoelectric device applications. Exploring methods to achieve multifunctional vdWs heterojunction devices is one of the most promising prospects in this area. Herein, a diverse function of forward rectifying diode, Zener tunneling diode, and backward rectifying diodes are realized in GeAs/ReS2 heterojunction by modulating the doping level of GeAs. The tunneling diode presents an interesting trend forward negative differential resistance (NDR) behavior which may facilitate the application of multi-value logic. More importantly, the GeAs/ReS2 forward rectifying diode exhibits highly sensitive photodetection in the wide-spectrum range up to 1550 nm corresponding to a short-wave infrared (SWIR) region. In addition, as two strong anisotropic 2D materials of GeAs and ReS2 , the heterojunction exhibits strong polarization-sensitive photodetection behavior with a dichroic photocurrent ratio of 1.7. This work provides an effective strategy to achieve multifunctional 2D vdW heterojunction devices and develops more possibilities to broaden their functionalities and applications.

Mechano/acousto-electric coupling between ReS2and surface acoustic wave.

Two-dimensional (2D) materials are promising candidates for developing next generation electronic/optoelectronic devices with programmable multi functions, due to their widely tunable properties by various physical stimuli. Mechanical strain is one of the most promising means to effectively modulate the physical properties of 2D materials. Nevertheless, few studies reported micro/nano scale controllable strain application platforms, limiting the development of novel mechano-electrical/optoelectrical devices based on 2D materials. This work proposes surface acoustic wave (SAW) device as a controllable strain modulation platform for 2D materials with sub-micro scale resolution. The platform uses the piezoelectric material (LiNbO3) as the substrate, which is deposited with interdigitated transducers (IDT) to generate SAW on the surface. The propagation of SAW causes surface deformation, which is then transferred to the 2D materials on the substrate. The period of the surface deformation/strain is related with that of SAW, which is determined by the period of IDT with nano meter scale. It is demonstrated that the photo luminescence spectrum of a 2D ReS2flake on this platform gradually shifts with the SAW excitation power, which reaches a shift of 3 nm as the SAW excitation power achieves 26 dBm, corresponding to a band gap increase of 5 meV. Meanwhile, the platform is also capable to provide acousto-electric coupling between SAW and 2D materials, which is demonstrated by the shift of the SAW resonant frequency due to the re-distribution of photo-generated carriers in ReS2upon light illumination.

Research on Fine-Grained Image Recognition of Birds Based on Improved YOLOv5.

Birds play a vital role in maintaining biodiversity. Accurate identification of bird species is essential for conducting biodiversity surveys. However, fine-grained image recognition of birds encounters challenges due to large within-class differences and small inter-class differences. To solve this problem, our study took a part-based approach, dividing the identification task into two parts: part detection and identification classification. We proposed an improved bird part detection algorithm based on YOLOv5, which can handle partial overlap and complex environmental conditions between part objects. The backbone network incorporates the Res2Net-CBAM module to enhance the receptive fields of each network layer, strengthen the channel characteristics, and improve the sensitivity of the model to important information. Additionally, in order to boost data on features extraction and channel self-regulation, we have integrated CBAM attention mechanisms into the neck. The success rate of our suggested model, according to experimental findings, is 86.6%, 1.2% greater than the accuracy of the original model. Furthermore, when compared with other algorithms, our model's accuracy shows noticeable improvement. These results show how useful the method we suggested is for quickly and precisely recognizing different bird species.

Interlayer Transition Induced Infrared Response in ReS2/2D Perovskite van der Waals Heterostructure Photodetector.

The emerging Ruddlesden-Popper two-dimensional perovskite (2D PVK) has recently joined the family of 2D semiconductors as a potential competitor for building van der Waals (vdW) heterostructures in future optoelectronics. However, to date, most of the reported heterostructures based on 2D PVKs suffer from poor spectral response that is caused by intrinsic wide bandgap of constituting materials. Herein, a direct heterointerface bandgap (∼0.4 eV) between 2D PVK and ReS2 is demonstrated. The strong interlayer coupling reduces the energy interval at the heterojunction region so that the heterostructure shows high sensitivity with the spectral response expanding to 2000 nm. The large type-II band offsets exceeding 1.1 eV ensure fast photogenerated carriers separation at the heterointerface. When this heterostructure is used as a self-driven photodetector, it exhibits a record high detectivity up to 1.8 × 1014 Jones, surpassing any reported 2D self-driven devices, and an impressive external quantum efficiency of 68%.

ReS2 Nanoflowers-Assisted Confined Growth of Gold Nanoparticles for Ultrasensitive and Reliable SERS Sensing.

ReS2, as a new member of transition metal dichalcogenides (TMDCs), has emerged as a promising substrate for semiconductor surface-enhanced Raman spectroscopy (SERS) due to its unique optoelectronic properties. Nevertheless, the sensitivity of the ReS2 SERS substrate poses a significant challenge to its widespread application in trace detection. In this work, we present a reliable approach for constructing a novel ReS2/AuNPs SERS composite substrate, enabling ultrasensitive detection of trace amounts of organic pesticides. We demonstrate that the porous structures of ReS2 nanoflowers can effectively confine the growth of AuNPs. By precisely controlling the size and distribution of AuNPs, numerous efficient and densely packed "hot spots" were created on the surface of ReS2 nanoflowers. As a result of the synergistic enhancement of the chemical and electromagnetic mechanisms, the ReS2/AuNPs SERS substrate demonstrates high sensitivity, good reproducibility, and superior stability in detecting typical organic dyes such as rhodamine 6G and crystalline violet. The ReS2/AuNPs SERS substrate shows an ultralow detection limit of 10-10 M and a linear detection of organic pesticide molecules within 10-6-10-10 M, which is significantly lower than the EU Environmental Protection Agency regulation standards. The strategy of constructing ReS2/AuNPs composites would contribute to the development of highly sensitive and reliable SERS sensing platforms for food safety monitoring.

The Progress on Magnetic Material Thin Films Prepared Using Polymer-Assisted Deposition.

Polymer-assisted deposition (PAD) has been widely used in the preparation of high-quality oxides and sulfides for basic research and applications. Specifically, diverse PAD-prepared magnetic material thin films such as ZnO, Ga2O3, SrRuO3, LaCoO3, LaMnO3, Y3Fe5O12, MoS2, MoSe2, and ReS2 thin films have been grown, in which thickness-dependent, strain-modulated, doping-mediated, and/or morphology-dependent room-temperature ferromagnetism (RTFM) have been explored. Inspired by the discovery of intrinsic low-temperature FM in two-dimensional (2D) systems prepared using mechanical exfoliation, the search for more convenient methods to prepare 2D ferromagnetic materials with high-temperature FM has seen explosive growth, but with little success. Fortunately, the very recent synthesis of 2D NiO by PAD has shed light on this challenge. Based on these abovementioned developments, the difficulties of PAD when preparing a-few-nanometer single-crystalline materials and the opportunities in PAD for novel materials such as chiral magnetic soliton material Cr1/3NbS2 are discussed.

Photocatalytic Applications of ReS2-Based Heterostructures.

ReS2-based heterostructures, which involve the coupling of a narrow band-gap semiconductor ReS2 with other wide band-gap semiconductors, have shown promising performance in energy conversion and environmental pollution protection in recent years. This review focuses on the preparation methods, encompassing hydrothermal, chemical vapor deposition, and exfoliation techniques, as well as achievements in correlated applications of ReS2-based heterostructures, including type-I, type-II heterostructures, and Z-scheme heterostructures for hydrogen evolution, reduction of CO2, and degradation of pollutants. We believe that this review provides an overview of the most recent advances to guide further research and development of ReS2-based heterostructures for photocatalysis.

Position-Wise Gated Res2Net-Based Convolutional Network with Selective Fusing for Sentiment Analysis.

Sentiment analysis (SA) is an important task in natural language processing in which convolutional neural networks (CNNs) have been successfully applied. However, most existing CNNs can only extract predefined, fixed-scale sentiment features and cannot synthesize flexible, multi-scale sentiment features. Moreover, these models' convolutional and pooling layers gradually lose local detailed information. In this study, a new CNN model based on residual network technology and attention mechanisms is proposed. This model exploits more abundant multi-scale sentiment features and addresses the loss of locally detailed information to enhance the accuracy of sentiment classification. It is primarily composed of a position-wise gated Res2Net (PG-Res2Net) module and a selective fusing module. The PG-Res2Net module can adaptively learn multi-scale sentiment features over a large range using multi-way convolution, residual-like connections, and position-wise gates. The selective fusing module is developed to fully reuse and selectively fuse these features for prediction. The proposed model was evaluated using five baseline datasets. The experimental results demonstrate that the proposed model surpassed the other models in performance. In the best case, the model outperforms the other models by up to 1.2%. Ablation studies and visualizations further revealed the model's ability to extract and fuse multi-scale sentiment features.

Hydrogen-Etched Bifunctional Sulfur-Defect-Rich ReS2 /CC Electrocatalyst for Highly Efficient HER and OER.

The design on synthesizing a sturdy, low-cost, clean, and sustainable electrocatalyst, as well as achieving high performance with low overpotential and good durability toward water splitting, is fairly vital in environmental and energy-related subject. Herein, for the first time the growth of sulfur (S) defect engineered self-supporting array electrode composed of metallic Re and ReS2 nanosheets on carbon cloth (referred as Re/ReS2 /CC) via a facile hydrothermal method and the following thermal treatment with H2 /N2 flow is reported. It is expected that, for example, the as-prepared Re/ReS2 -7H/CC for the electrocatalytic hydrogen evolution reaction (HER) under acidic medium affords a quite low overpotential of 42 mV to achieve a current density of 10 mA cm-2 and a very small Tafel slope of 36 mV decade-1 , which are comparable to some of the promising HER catalysts. Furthermore, in the two-electrode system, a small cell voltage of 1.30 V is recorded under alkaline condition. Characterizations and density functional theory results expound that the introduced S defects in Re/ReS2 -7H/CC can offer abundant active sites to advantageously capture electron, enhance the electron transport capacity, and weaken the adsorption free energy of H* at the active sites, being responsible for its superior electrocatalytic performance.

Ultrahigh Photoresponsive Device Based on ReS2 /Graphene Heterostructure.

Heterostructures that combine graphene and transition metal dichalcogenides, such as MoS2 , MoTe2 , and WS2 , have attracted attention due to their high performances in optoelectronic devices compared to homogeneous systems. Here, a photodevice based on a hybrid van der Waals heterostructure of rhenium disulfide (ReS2 ) and graphene is fabricated using the stacking method. The device presents a remarkable ultrahigh photoresponsivity of 7 × 105 A W-1 and a detectivity of 1.9 × 1013 Jones, along with a fast response time of less than 30 ms. Tremendous photocurrents are generated in the heterostructure due to the direct bandgap, high quantum efficiency, and strong light absorption by the multilayer ReS2 and the high carrier mobility of graphene. The ReS2 /graphene heterostructured device displays a high photocurrent under the applied gate voltages due to the photogating effect induced by the junction between graphene and ReS2 . The ReS2 /graphene heterostructure may find promising applications in future optoelectronic devices, providing a high sensitivity, flexibility, and transparency.

Unraveling the Raman Enhancement Mechanism on 1T'-Phase ReS2 Nanosheets.

2D transition metal dichalcogenides materials are explored as potential surface-enhanced Raman spectroscopy substrates. Herein, a systematic study of the Raman enhancement mechanism on distorted 1T (1T') rhenium disulfide (ReS2 ) nanosheets is demonstrated. Combined Raman and photoluminescence studies with the introduction of an Al2 O3 dielectric layer unambiguously reveal that Raman enhancement on ReS2 materials is from a charge transfer process rather than from an energy transfer process, and Raman enhancement is inversely proportional while the photoluminescence quenching effect is proportional to the layer number (thickness) of ReS2 nanosheets. On monolayer ReS2 film, a strong resonance-enhanced Raman scattering effect dependent on the laser excitation energy is detected, and a detection limit as low as 10-9 m can be reached from the studied dye molecules such as rhodamine 6G and methylene blue. Such a high enhancement factor achieved through enhanced charge interaction between target molecule and substrate suggests that with careful consideration of the layer-number-dependent feature and excitation-energy-related resonance effect, ReS2 is a promising Raman enhancement platform for sensing applications.

Large-Area CVD-Grown Sub-2 V ReS2 Transistors and Logic Gates.

We demonstrated the fabrication of large-area ReS2 transistors and logic gates composed of a chemical vapor deposition (CVD)-grown multilayer ReS2 semiconductor channel and graphene electrodes. Single-layer graphene was used as the source/drain and coplanar gate electrodes. An ion gel with an ultrahigh capacitance effectively gated the ReS2 channel at a low voltage, below 2 V, through a coplanar gate. The contact resistance of the ion gel-gated ReS2 transistors with graphene electrodes decreased dramatically compared with the SiO2-devices prepared with Cr electrodes. The resulting transistors exhibited good device performances, including a maximum electron mobility of 0.9 cm2/(V s) and an on/off current ratio exceeding 104. NMOS logic devices, such as NOT, NAND, and NOR gates, were assembled using the resulting transistors as a proof of concept demonstration of the applicability of the devices to complex logic circuits. The large-area synthesis of ReS2 semiconductors and graphene electrodes and their applications in logic devices open up new opportunities for realizing future flexible electronics based on 2D nanomaterials.