Ultrafine WC_1–<i>x</i> Nanocrystals: An Efficient Cocatalyst for the Significant Enhancement of Photocatalytic Hydrogen Evolution on g‑C₃N₄

Developing noble metal-free, inexpensive, and highly active cocatalysts to increase the photocatalytic activity of photocatalysts and promote the practical application is significantly important. In this work, ultrafine carbon-deficient tungsten carbide (WC1–x) nanocrystals with an average size of 1.98 ± 0.29 nm are successfully prepared as cocatalysts to dramatically enhance the photocatalytic activity of graphitic carbon nitride (g-C3N4). The optimized system (WC1–xCN5) exhibits the best photocatalytic H2 production rate of 124.5 μmol h–1 (2490 μmol h–1 g–1), which is about 56 times that of bare g-C3N4. In this system, ultrafine WC1–x nanocrystals play a multifunctional role: effectively boosting the carrier separation and transfer and providing rich active sites for H2 production. Hence, the loading of WC1–x nanocrystals remarkably increases the photocatalytic H2 production activity of g-C3N4. This work demonstrates that ultrafine WC1–x nanocrystals have practical application potential to enhance photocatalytic H2 evolution of g-C3N4

Computing Shor's algorithmic steps with classical light beams

When considered as orthogonal bases in distinct vector spaces, the unit vectors of polarization directions and the Laguerre-Gaussian modes of polarization amplitude are inseparable, constituting a so-called classical entangled light beam. Equating this classical entanglement to quantum entanglement necessary for computing purpose, we show that the parallelism featured in Shor's factoring algorithm is equivalent to the concurrent light-path propagation of an entangled beam or pulse train. A gedanken experiment is proposed for executing the key algorithmic steps of modular exponentiation and Fourier transform on a target integer $N$ using only classical manipulations on the amplitudes and polarization directions. The multiplicative order associated with the sought-after integer factors is identified through a four-hole diffraction interference from sources obtained from the entangled beam profile. The unique mapping from the fringe patterns to the computed order is demonstrated through simulations for the case $N=15$

Quantitative Determination of Charge Accumulation and Recombination in Operational Quantum Dots Light Emitting Diodes via Time-Resolved Electroluminescence Spectroscopy

In this work, we report the quantitative determination of charge accumulation and recombination in an operated QLED using time-resolved electroluminescence (TREL) spectroscopy. As a supplement technique, time-resolved current (TRC) measurement was introduced and simulated using equivalent circuit model with a series resistance, a parallel resistance, and a capacitance. By modeling the key processes in a typical TREL spectra, the stages of delay, rising, and decay can be correlated to the charge accumulations, charge injection and recombination, and charge release and recombination, respectively. In particular, the rising stage can be described using a modified Langevin recombination model. The electroluminescence recombination rate can be derived by fitting the rising stage curves in the TREL spectra, providing an intrinsic parameter of the emissive materials. In all, this work provides a methodology to quantitatively determine the charge accumulation and recombination of an operational QLED device

Single-Photon-Camera-Based Time and Spatially Resolved Electroluminescence Spectroscopy for Micro-LED Analysis

To investigate the operational mechanisms of micrometer-sized light-emitting diodes (micro-LEDs), we here demonstrate a transient methodology of time and spatially resolved electroluminescence spectroscopy (TSR-EL) to measure the spatial distribution of light emission from LED devices. By combining a single-photon camera (SPC) with the time-gated sampling method, we derived the time and spatially resolved electroluminescence intensity with increasing time. Benefiting from the high sensitivity of the SPC, this methodology can detect ultralow electroluminescence (EL) at the delay stage from the device operated around the turn-on voltage. Furthermore, we investigated the spatial light distribution of a typical quantum dots light-emitting diode (QLED) under different applied voltages and varied temperatures. It was found that the EL emission of the QLED device became more uniform with increasing temperature and applied voltage. Moreover, the methodology of TSR-EL is versatile to investigate other LEDs such as organic light-emitting diodes (OLEDs), micro-LEDs, etc

Activated Triplet Exciton Release for Highly Efficient Room-Temperature Phosphorescence Based on S,N-Doped Polymeric Carbon Nitride

Polymeric carbon nitride (PCN) shows great potential applications in the areas of sustainable energy (photocatalysis and photoelectric conversion, as well as other important catalytic reactions), biosensing, biomedicine, devices, and more, but efficient phosphorescence is very scarce because of the lack of an effective synthetic method and an unsettled phosphorescent mechanism. Herein, we report a strategy to promote efficient phosphorescence to activate triplet exciton release by introduction of S and N elements. PCN could be synthesized by thiourea or urea (named S,N-PCN and N-PCN, respectively) at a relatively low reaction temperature (260 °C). S,N-PCN exhibits phosphorescence quantum yield (4.15%) higher than that (0.41%) for N-PCN. The introduction of C=S and C≡N groups in S,N-PCN networks could boost the intersystem crossing (ISC), leading to small singlet–triplet energy (ΔEST) up to more triplet exciton generation. Considering the excellent optical stability of PCN, a preliminary application of visible-light-excited PCN in advanced anticounterfeiting is proposed

Polarization-Sensitive Detector Based on MoTe₂/WTe₂ Heterojunction for Broadband Optoelectronic Imaging

Polarization-sensitive detectors have significant applications in modern communication and information processing. In this study. We present a polarization-sensitive detector based on a MoTe2/WTe2 heterojunction, where WTe2 forms a favorable bandgap structure with MoTe2 after forming the heterojunction. This enhances the carrier separation efficiency and photoelectric response. We successfully achieved wide spectral detection ranging from visible to near-infrared light. Specifically, under zero bias, our photodetector exhibits a responsivity (R) of 0.6 A/W and a detectivity (D*) of 3.6 × 1013 Jones for 635 nm laser illumination. Moreover, the photoswitching ratio can approach approximately 6.3 × 105. Importantly, the polarization sensitivity can reach 3.5 (5.2) at 635 (1310) nm polarized light at zero bias. This study both unveils potential for utilizing MoTe2/WTe2 heterojunctions as polarization-sensitive detectors and provides novel insights for developing high-performance optoelectronic devices

Polarization-Sensitive Detector Based on MoTe₂/WTe₂ Heterojunction for Broadband Optoelectronic Imaging

Polarization-sensitive detectors have significant applications in modern communication and information processing. In this study. We present a polarization-sensitive detector based on a MoTe2/WTe2 heterojunction, where WTe2 forms a favorable bandgap structure with MoTe2 after forming the heterojunction. This enhances the carrier separation efficiency and photoelectric response. We successfully achieved wide spectral detection ranging from visible to near-infrared light. Specifically, under zero bias, our photodetector exhibits a responsivity (R) of 0.6 A/W and a detectivity (D*) of 3.6 × 1013 Jones for 635 nm laser illumination. Moreover, the photoswitching ratio can approach approximately 6.3 × 105. Importantly, the polarization sensitivity can reach 3.5 (5.2) at 635 (1310) nm polarized light at zero bias. This study both unveils potential for utilizing MoTe2/WTe2 heterojunctions as polarization-sensitive detectors and provides novel insights for developing high-performance optoelectronic devices

Quantitative Determination of Charge Accumulation and Recombination in Operational Quantum Dots Light Emitting Diodes via Time-Resolved Electroluminescence Spectroscopy

In this work, we report the quantitative determination of charge accumulation and recombination in an operated QLED using time-resolved electroluminescence (TREL) spectroscopy. As a supplement technique, time-resolved current (TRC) measurement was introduced and simulated using equivalent circuit model with a series resistance, a parallel resistance, and a capacitance. By modeling the key processes in a typical TREL spectra, the stages of delay, rising, and decay can be correlated to the charge accumulations, charge injection and recombination, and charge release and recombination, respectively. In particular, the rising stage can be described using a modified Langevin recombination model. The electroluminescence recombination rate can be derived by fitting the rising stage curves in the TREL spectra, providing an intrinsic parameter of the emissive materials. In all, this work provides a methodology to quantitatively determine the charge accumulation and recombination of an operational QLED device

Waved 2D Transition-Metal Disulfides for Nanodevices and Catalysis: A First-Principle Study

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) monolayers have found various applications spanning from electronics in physics to catalysis in chemistry due to their unique physical and chemical properties. Here, the effect of structure engineering on the physical and chemical properties of transition-metal disulfide monolayers (MS2) is systematically investigated based on density functional theory (DFT) calculations. The calculation results show that waved MS2 (w-MS2) can be achieved under compression due to the zero in-plane stiffness, leading to high flexibility within a wide range of compression. The bandgap and conductivity of semiconducting w-MS2 are reduced because the d orbitals of transition-metal elements become more localized as the curvature increases. A transition from a direct band to an indirect one is observed in w-MoS2 and w-WS2 after a critical strain. We further demonstrate the structure engineering can modulate the magnetism of w-VS2, leading to nonuniform distribution of magnetic moments along the curvature. Furthermore, we find that waved TMDs show reduced Gibbs free energy for hydrogen adsorption, resulting in enhanced catalytic performance in hydrogen reaction evolution (HER). It is expected that the waved 2D TMDs may find applications into various areas, such as nanodevices and catalysis

Activated Triplet Exciton Release for Highly Efficient Room-Temperature Phosphorescence Based on S,N-Doped Polymeric Carbon Nitride

Polymeric carbon nitride (PCN) shows great potential applications in the areas of sustainable energy (photocatalysis and photoelectric conversion, as well as other important catalytic reactions), biosensing, biomedicine, devices, and more, but efficient phosphorescence is very scarce because of the lack of an effective synthetic method and an unsettled phosphorescent mechanism. Herein, we report a strategy to promote efficient phosphorescence to activate triplet exciton release by introduction of S and N elements. PCN could be synthesized by thiourea or urea (named S,N-PCN and N-PCN, respectively) at a relatively low reaction temperature (260 °C). S,N-PCN exhibits phosphorescence quantum yield (4.15%) higher than that (0.41%) for N-PCN. The introduction of C=S and C≡N groups in S,N-PCN networks could boost the intersystem crossing (ISC), leading to small singlet–triplet energy (ΔEST) up to more triplet exciton generation. Considering the excellent optical stability of PCN, a preliminary application of visible-light-excited PCN in advanced anticounterfeiting is proposed