Yingkai Liu

Mixed‐dimensional van der Waals heterojunctions offer opportunities for self‐powered optical sensing and information processing, yet identifying the spatial origin of zero‐bias photoresponse remains important for understanding device operation. Here, a vertical WSe ₂ /CdSe heterojunction composed of a WSe ₂ nanosheet and a CdSe nanobelt is investigated for visible photodetection. Under 610 nm illumination, the device exhibits a photovoltaic response with an open‐circuit voltage of 0.403 V and a short‐circuit current of 4.77 × 10 ⁻¹⁰ A. Quantitative photocurrent mapping reveals a mean response of 5.94 nA in the heterojunction overlap region, approximately 50 times that near the metal contacts. Scanning Kelvin probe microscopy yields a reproducible contact‐potential‐difference contrast of 293 ± 15 mV, whereas electronic‐structure calculations support a type‐II band‐edge configuration and interfacial charge redistribution. At 100 Hz, the measured rise/fall times are 1.09/0.99 ms at 0 V and 165/191 μs at +3 V. Under +3 V bias, approximately 97% of the reference modulation amplitude is retained at 1 kHz. Self‐powered optical imaging and wavelength‐ and time‐window‐dependent 8‐bit information recognition are further demonstrated, with all 96 tested bits correctly decoded. These results highlight the potential of mixed‐dimensional WSe ₂ /CdSe heterojunctions for self‐powered visible‐light sensing and optical information recognition.

Triethylamine (TEA) is a toxic, flammable amine compound with stringent occupational exposure limits, making its detection necessary for workplace safety and environmental monitoring. However, traditional metal-oxide sensors operate at temperatures as high as 160–350°C, resulting in high power consumption and incompatibility with the low-temperature operating conditions required by complementary metal-oxide-semiconductor (CMOS) integrated circuits. This severely hinders their integration into the Internet of Things (IoT). Here, we report blue-light-activated gas sensing based on SnS₂/TiO₂ heterostructured nanoflowers synthesized by a facile hydrothermal method for ppb-level detection of TEA at room temperature (RT, 23°C). The formation of an n–n heterojunction induces spontaneous interfacial electron transfer from TiO₂ to SnS₂, reducing the ultrahigh baseline resistance of pristine SnS₂ (often >10 GΩ) to a measurable range. Under 450 nm blue-light irradiation (80 mW/cm²), the optimized sensor (Sn/Ti = 8:1) delivers a response of 17.32 toward 10 ppm TEA at RT—about 4.9 times higher than in the dark—with an ultralow detection limit of 14.9 ppb, excellent selectivity, and good humidity tolerance. Combined experimental characterizations and DFT calculations reveal that the enhanced performance originates from three synergistic effects: the hierarchical high-surface-area architecture, efficient interfacial charge transfer, and blue-light-accelerated surface reaction kinetics with photoinduced carrier separation. Together, these overcome the severe bottleneck in the dark. This work demonstrates a low-power, room-temperature sensing concept based on light-activated SnS₂/TiO₂ heterojunctions, offering a material-level basis for future low-power olfactory nodes in IoT systems.

The development of high-performance triethylamine (TEA) gas sensors operating at reduced temperatures remains a challenge for practical applications. Here, we address this by decorating CuO nanosheets with Ag nanoparticles at controlled molar ratios (0.1:1, 0.2:1, and 0.3:1). Compared with pure CuO, the optimal Ag/CuO sensor (0.2:1) achieves a 13.3-fold higher response to 100 ppm TEA and lowers the operating temperature by 60 °C, while also enabling ppb-level detection. Experimental and density functional theory (DFT)-based mechanistic studies reveal that Ag nanoparticles act as catalytic centers that not only promote surface reactions but also enhance electron transfer, collectively accounting for the observed improvement. This work provides a simple and effective design strategy for practical gas sensors via rational noble metal loading.

Triethylamine (TEA) poses a serious threat to human health, necessitating high-performance gas sensors. This work enhances TEA sensing by co-modifying In2O3 with CuO and Ag. A series of In2O3-based composites (binary In2O3/CuO with different ratios of In to Cu, and ternary Ag/In2O3/CuO with 3–9 wt % Ag) was prepared via solvothermal calcination and chemical reduction. Sensing performance progressively improved from pristine In2O3 to binary and ternary composites. The 7 wt % Ag-loaded In2O3/CuO sensor showed a 46.65-fold higher response to 100 ppm TEA than pristine In2O3. Moreover, the optimal working temperature was reduced by 80 °C and it achieved a ppb-level detection limit. The enhanced performance is attributed to the synergistic effects of p–n heterojunction formation, Ag-induced chemical and electronic sensitization, and oxygen-vacancy regulation. This study provides an effective strategy for developing high-performance metal-oxide-semiconductor gas sensors through the cooperative engineering of heterojunctions and noble-metal sensitization.

A dual‐band device that can simultaneously possess high sensitivity and neuron‐like processing capabilities is highly desirable for next‐generation intelligent optoelectronic systems. However, traditional single‐material devices have the problems of poor performance and low integration level. Furthermore, due to their high‐power consumption, they are limited in applications such as integrated sensing, computing and storage, optical encryption communication, and imaging. Here, we report a multifunctional CuInP ₂ S ₆ (CIPS)/Ga ₂ O ₃ heterojunction that integrates ultraviolet (UV–Visible photodetection, artificial synaptic function, neuron‐like recognition, and dual‐wavelength optical communication and imaging. Notably, this constructed type‐II CIPS/Ga ₂ O ₃ van der Waals heterojunction provides an opportunity to modulate the interface charge carrier transport, then enhance the light absorbance, thereby achieving high responsivity (275 A/W), and enhanced detectivity (1.95 × 10 ¹⁵ Jones) under irradiation of 245 nm UV light. Significantly, the device also exhibits vital synaptic plasticity, including dual‐pulse promotion and adjustable memory retention capability. By mapping the experimentally extracted single‐device forgetting dynamics to a simulated convolutional neural network framework, high accuracy has been achieved on both simple and complex datasets. Additionally, wavelength‐selective light response supports dual‐band UV‐visible light communication and imaging. This work establishes a multifunctional heterojunction platform, advancing the research and development of modern optoelectronics.

High‐performance photodetectors for low‐light imaging and high‐speed information processing require high responsivity, high specific detectivity, fast response, and ultralow power consumption enabled by minimal dark current. Although 2D van der Waals heterojunctions can suppress dark current and promote carrier separation via built‐in electric fields, most reported devices still rely on external bias, limiting their application in energy‐efficient integrated systems. Moreover, integrating self‐powered photodetection with programmable optoelectronic logic in a single device remains challenging. Here, we report a vertical trilayer vdW heterojunction phototransistor based on PdSe ₂ /SnS ₂ /MoS ₂ with synergistic functionality. By strengthening the built‐in electric field and optimizing interfacial energy‐level alignment, this architecture suppresses the dark current to the picoampere level while bringing the ideality factor close to unity (η ≈ 1). The device operates in a fully self‐powered mode, achieving a high responsivity of 654 mA W ⁻¹ and a specific detectivity of 5.4 × 10 ¹² Jones under 638 nm illumination—surpassing most previously reported PdSe ₂ ‐based self‐powered photodetectors. Beyond photodetection, gate‐voltage modulation enables switchable multistable output states, thereby seamlessly integrating self‐powered sensing with programmable optoelectronic logic in a single device. This work establishes a viable device paradigm for low‐power, highly integrable visible and near‐infrared optoelectronic logic systems.

Advancing multimodal perception in artificial intelligence remains a challenge, requiring photodetectors with intelligent multi‐mode switching. Here, we present an innovative multifunctional photodetector based on a type‐II band‐aligned In ₂ S ₃ /InSe van der Waals heterojunction. It exhibits conventional photoconductive detection capabilities, achieving a light on/off current ratio of 1.75 × 10 ⁵ under 380 nm relatively strong light illumination at a 5 V bias. It switches to a photonic synapse mode under weak light illumination, emulating human learning and forgetting behaviors, and exhibits the characteristics of visual neural synapses. Inspired by this, we simulated a biomimetic visual neural network capable of waste recognition and classification, achieving 97.77% identification accuracy. Without bias, the device exhibited self‐powered photodetection with an ultrafast response, high‐resolution imaging, and encrypted optical communication. A “waveform analysis” software was developed to decode the encrypted current signals, enabling automated data processing and secure communication. This study provides a foundation for innovative optoelectronic devices and efficient artificial vision systems, demonstrating significant potential for next‐generation multifunctional components.

In ₂ Se ₃ exhibits advantages such as atomic-level thickness and tunable bandgap. However, the optoelectronic performance of a single In ₂ Se ₃ -based device is insufficient, limiting its application in imaging fields. Moreover, conventional semiconductor devices integrated on Si/SiO ₂ substrates further restrict their use in wearable electronic sensors. In this study, a flexible CdSe/ β -In ₂ Se ₃ heterostructure device is fabricated via a combination of wet and dry transfer techniques, achieving enhanced optoelectronic performance, which is attributed to the unique type‐II band alignment of the CdSe/ β -In ₂ Se ₃ heterojunction. Under 520 nm illumination, the device exhibits a high responsivity of 4.32 × 10 ³ A W ⁻¹ , an external quantum efficiency of 1.03 × 10 ⁶ %, and a specific detectivity of 1.59 × 10 ¹³ Jones, with fast response times of 10/20 ms for the rise and decay processes, respectively. Furthermore, the application of the flexible device for visible light imaging is demonstrated, providing a technical foundation for the utilization of In ₂ Se ₃ in wearable electronic sensors.

Precise, noninvasive quantification of gaseous ammonia (NH3) in exhaled breath is a promising clinical diagnostic method with important applications for assessing liver and kidney metabolic function. A critical factor in NH3 detection is the electronic structure of metal active sites. However, the pivotal role of electron spin as a descriptor of these electronic properties is often overlooked. Here, we address this by synthesizing Co-HITP, CoNi-HITP, and CoNiFe-HITP gas-sensitive materials. These materials were developed by strategically modulating the spin state of Co metal sites, achieved through the synergistic coupling of Fe, Co, and Ni single atoms. Experimental investigations, complemented by density functional theory (DFT) calculations, revealed that the modulated spin states at the metal sites and their synergistic effects profoundly influence the adsorption and activation processes of NH3 and key reaction intermediates (e.g., *NH2, *HNO, and *NO), consequently altering the energy barriers. The optimized CoNiFe-HITP exhibited exceptional sensitivity (88.8%), selectivity, and a low detection limit (50 ppb) for 1000 ppm NH3 at room temperature. This study not only highlights the potential of 2D metal−organic frameworks as an ideal platform for spin regulation to enhance gas sensitivity but also provides novel design insights for developing highly efficient and low-power gas sensors.

Based on the excellent physical properties of the two-dimensional materials InSe and ZrSSe, exploring whether their heterostructures can realize tunable band alignment has become an important scientific issue in the research of optoelectronic functional materials. In this work, first-principles calculations based on density functional theory (DFT) were employed to systematically investigate the evolution of the electronic structure and optical properties of InSe/ZrSSe van der Waals heterostructures (vdW heterostructures) under varying interlayer distances, strain, and external electric fields. The results show that both the InSe/SeZrS and InSe/SZrSe heterostructures exhibit type-II band alignment, enabling efficient interfacial separation of photoinduced electron–hole pairs and delivering excellent optical absorption from the visible to the near-infrared region. Notably, for the InSe/SZrSe heterostructure, both the conduction-band minimum (CBM) and valence-band maximum (VBM) shift regularly under either uniaxial or biaxial strain, when the strain exceeds 3%, the band alignment can transform from type II to type I. Moreover, under an applied out-of-plane electric field, heterostructure model can undergo transitions from type II to type I or even type III band alignment. These findings highlight the broad application potential of InSe/ZrSSe heterostructures in photocatalysis and optoelectronic devices, and provide a solid theoretical basis for their experimental fabrication and device design.