ABSTRACT Organic photovoltaic catalysts (OPCs) hold great potential for energy conversion and environmental purification yet often suffer from inefficient exciton dissociation and rapid charge recombination, particularly at disordered donor/acceptor (D/A) interfaces, limiting their photocatalytic performance. Herein, we propose an embedded interface strategy that involves a highly polarizable molecule named Y6CO‐S at the D/A interface within OPC bulk heterojunction (BHJ) to amplify the local electric field and enhance molecular ordering, improving hole transfer efficiency and prolonging hole polaron lifetime, and thereby boosting photocatalytic activity. Specifically, the optimized PM6:PYF‐T‐o:Y6CO‐S nanoparticles (NPs) achieve remarkable photocatalytic sacrificial average mass‐united/area‐united hydrogen evolution rates of 263.8‐1974.7 mmol h − 1 g − 1 and 42.7‐182.4 mmol h −1 m −2 at varied NP concentrations under simulated sunlight (AM 1.5G, 100 mW cm −2 ) for 10 h along with high external quantum efficiencies of >10% across the visible to near‐infrared region, 36%–47% exceeding those of the binary PM6:PYF‐T‐o system without Y6CO‐S embedded interface and representing one of the highest performances reported to date for photocatalysts. This work demonstrates the significant potential of embedded interface strategy in developing high‑performance heterojunction OPCs as well as other optoelectronic applications.

Understanding the intrinsic excited-state dynamics of nonfullerene acceptors (NFAs) is essential for linking molecular design to device performance. Here, we study the prototypical NFA Y6 in dilute solution using femtosecond transient absorption and fluorescence upconversion spectroscopy. We resolve two coupled low-lying excited-state components with LE-like and CT-like character. Distinct initial populations prepared by different excitation energies evolve into the same long-time spectral and kinetic fingerprint, providing direct evidence for a reversible quasi-equilibrium. Temperature-dependent exchange rates follow Arrhenius behavior with an apparent activation energy of ∼76 meV. This quasi-equilibrium biases the population toward the weakly emissive CT-like branch, shortening the effective exciton lifetime and constraining exciton utilization in strongly coupled donor-acceptor systems.

Iron-doped gallium oxide (Ga2O3) is extensively exploited as semi-insulating substrates for epitaxial thin film growth to fabricate next-generation high-power electronics and ultraviolet optoelectronics. However, the influence of iron (Fe) dopants on electron transport dynamics remains poorly understood, particularly in the context of defect-mediated scattering and trapping mechanisms. Here, we employ time-resolved terahertz (THz) spectroscopy to investigate the temperature-dependent photoconductivity and free electron dynamics in Fe-doped Ga2O3 crystals. The frequency-dependent THz conductivities demonstrate dispersive charge transport dominated by heterogeneous scattering, modeled effectively by the Drude-Smith formulizm. The temperature dependence of both electron mobility and electron scattering time indicates a transition from phonon-dominated scattering to a defect-mediated scattering mechanism. Moreover, the kinetics of transient photoconductivity further uncover that the free electrons collapse into a highly localized state fostered by Fe3+ dopants on a sub-100 ps timescale. Nevertheless, this trapping process is suppressed at low temperature because the itinerant electrons are trapped at the shallow defects before encountering deep centers associated with the Fe3+ dopant. Our results offer a fundamental understanding of the microscopic electron transport mechanism in Fe-doped Ga2O3 crystals.

The emerging magnetic van der Waals (vdW) materials provide a platform for exploring novel physics regarding magnetism in low dimensions and developing ultrathin spintronic applications. Here, we investigate the ultrafast dynamics of excitons in a vdW NiPS3 crystal. The temporal evolution of the transient reflection spectra indicates that the spin-correlated exciton is formed through photocarrier localization, the rate of which is independent of the magnetic degrees of freedom. However, the recombination rate of these excitons correlates with the long-range magnetic order, likely arising from a spin-flip rooted in the underlying antiferromagnetic background during the recombination. Our findings uncover intertwined coupling between carrier, lattice, and spin degrees of freedom in NiPS3, which may pave the path toward ultrafast optical manipulation of spin-related quantum states in vdW antiferromagnets.

Visible-light-absorbing semiconductor nanocrystals have shown great promise as photocatalysts for promoting photoredox chemistry. However, their utilization in organic synthesis remains considerably limited compared to small molecule photosensitizers. Recently, the generation of hot electrons from quantum-confined systems has emerged as a powerful means of photoreduction, yet the efficiencies remain limited under mild conditions. In this study, we present an efficient hot-electron generation system facilitated by the spin-exchange Auger process in Mn 2+ -doped CdS/ZnS quantum dots. These hot electrons can be effectively utilized in a wide range of organic reactions, such as the Birch reduction and reductive cleavage of C-Cl, C-Br, C-I, C-O, C-C, and N-S bonds. Notably, these reactions accommodate substrate reduction potentials as low as −3.4 V versus the saturated calomel electrode. Through two-photon excitation, we achieve the generation of a “super” photoreductant using visible-light irradiation power that is only 1% of that previously reported for molecular and quantum dot systems. By modulating the intensity of light output, the spin-exchange Auger process enables the on/off generation of hot electrons, allowing for programmable assembly-point cross-coupling cascades. Our findings demonstrate the potential of quantum-confined semiconductors in facilitating challenging organic transformations that were unattainable with molecular photocatalysts.

Layered van der Waals (vdW) magnetic semiconductors open a new avenue for exploring intertwined excitonic and magnetic phenomena. Here, we investigate this interplay in the vdW antiferromagnet MnPS3, uncovering an exceptionally long exciton lifetime ( 100 μs) below the Néel temperature (T_N). We demonstrate that the exciton lifetime is governed by phonon-assisted nonradiative recombination and thus exhibits a strong temperature dependence. In contrast, the exciton radiative recombination shows a distinct temperature dependence that is sensitive to magnetic order. Below T_N, the temperature dependence of the radiative recombination rate is consistent with a magnon-assisted emission pathway, while above T_N it reflects the combined effects of short-range spin correlations and phonons. These findings not only establish MnPS3 as a compelling candidate for excitonic devices due to its long-lifetime and correlation with magnetic orders but also provide crucial insights into the interplay between excitons, spins, and lattice in vdW magnetic semiconductors.

Halide perovskites have attracted substantial attention recently. However, the strong lattice distortion effects in these materials have led to debates regarding the nature of charge carriers. While the behavior of carriers in bulk three-dimensional materials is well-documented, the characteristics of carriers in two-dimensional perovskites remain less well understood. In this study, we provide direct and clear evidence of small polaron formation through transient spectroscopic analysis of deformation potential and dynamic lattice screening. Coherent acoustic phonon wave signals reveal a strong coupling between carriers and lattice degrees of freedom, leading to small polaron formation and a spin lifetime enhancement of up to 10-fold. Utilizing optical Kerr spectroscopy and theoretical modeling, we observed a notably long polarization response time at room temperature, attributed to lattice distortion and small polarons approximately two-unit cells in size. Temperature-dependent coherent phonon dynamics and X-ray diffraction further confirmed the presence of small polarons. This discovery underscores the significance of the cooperative interplay between exciton dynamics and the small polaron field, particularly in influencing the Coulomb exchange interaction of excitons.

On-chip stimulated Brillouin scattering[SBS]has attracted extensive attention by introducing acousto-optic coupling inter-actions in all-optical signal processing systems.A series of chip-level applications such as Brillouin lasers,amplifiers,gyro-scopes,filters,and nonreciprocal devices are realized based on Brillouin acousto-optic interaction.Here,we first introduce the fundamental principle of SBS in integrated photonics and a method for calculating Brillouin gain;then we illustrate the Brillouin effect on different material platforms with diverse applications.Finally,we make a concise conclusion and offer prospects on the future developments of on-chip SBS.

On-chip stimulated Brillouin scattering (SBS) has attracted extensive attention by introducing acousto-optic coupling interactions in all-optical signal processing systems. In this article, we demonstrate stimulated intermodal Brillouin scattering (SIMBS) through a hybrid photonic-phononic silicon waveguide on the silicon-on-insulator (SOI) platform. The designed photonic-phononic waveguide can independently control the optical and acoustic fields by introducing the ridge waveguide as a line defect into the honeycomb lattice phononic crystal slab. Small-signal Stokes gain of 0.7 dB is achieved in a 1-cm long straight waveguide device with an on-chip pump power of 42.5 mW. Positive net Brillouin amplification is also expected by effectively reducing the linear loss. Our proposed device offers a potential approach to implementing Brillouin amplifiers, nonreciprocal devices, and signal processing in planar photonic integrated circuits.

Direct utilization of solar energy by semiconductor nanocrystals for chemical transformations via photocatalysis has recently drawn a great deal of attention. While most photocatalytic reactions are mediated through photoredox events, the ultimate reaction scalability relies on the use of sacrificial agents. The imbalanced population of photogenerated electrons and holes often leads to catalyst degradation through photocorrosion. To circumvent this, we designed Ni2+-doped CsPbBr3 nanoplatelets (NPls) as a "redox-neutral" photocatalyst, where both oxidative and reductive cycles occur in one photocatalyst. We showed that surface Ni2+ ions can act as an "electron shuttle" to reduce protons, generating clean-energy H2 gas, while the photogenerated holes can be used to oxidize diaryl hydrazines to afford valuable azobenzenes and derivatives. Compared with previous photocatalytic demonstrations, our catalysts show excellent reaction yields with a wide substrate scope, unity atomic efficiency, and enhanced stability and recyclability.

This study demonstrates an acetate ligand (AcO-)-assisted strategy for the controllable and tunable synthesis of colloidal methylammonium lead iodide (MAPbI3) perovskite nanocrystals (PNCs) for efficient photovoltaic and photodetector devices. The size of colloidal MAPbI3 PNCs can be tuned from 9 to 20 nm by changing the AcO-/MA ratio in the reaction precursor. In situ observations and detailed characterization results show that the incorporation of the AcO- ligand alters the formation of PbI6 octahedral cages, which controls PNC growth. A well-optimized AcO-/MA ratio affords MAPbI3 PNCs with a low defect density, a long carrier lifetime, and unique solid-state isotropic properties, which can be used to fabricate solution-processed dual-mode photovoltaic and photodetector devices with a conversion efficiency of 13.34% and a detectivity of 2 × 1011 Jones, respectively. This study provides an avenue to further the precisely controllable synthesis of hybrid PNCs for multifunctional optoelectronic applications.

It is particularly meaningful to therapeutic drug monitoring (TDM) of mycophenolic acid (MPA) for transplant patients to maximize the drug efficacy and minimize the adverse effect. In this study, a novel fluorescence and colorimetric dual-readout probe was put forward to fast and reliable detect MPA. The blue fluorescence of MPA was largely enhanced in the presence of poly (ethylenimine) (PEI), while the red fluorescence of CdTe@SiO2 (silica-coated CdTe quantum dots) provided a reliable reference signal. Hence, combining PEI70,000 and CdTe@SiO2, a fluorescence and colorimetric dual-readout probe could be constructed. For fluorescence measurement of MPA, the linearity was obtained in the MPA concentration range of 0.5-50 mu g/mL, with a limit of detection (LOD) of 33 ng/mL. For the visual detection, the fluorescent colorimetric card was established in the MPA concentration from 0.5 to 50 mu g/mL corresponding to the fluorescence color from red to violet and then to blue, which could be used for semi-quantification. Furthermore, in the light of the ColorCollect APP by the smartphone, the ratio of blue and red brightness values was linear with the MPA concentration from 1 to 50 mu g/ mL; thus, quantification of MPA could be realized by APP with the LOD of 83 ng/mL. The developed method was successfully applied to the analysis of MPA in the plasma samples of three patients after oral administration of mycophenolate mofetil, which was the prodrug of MPA. The result was comparable to those obtained by the clinically widely-used enzyme multiplied immunoassay technique. The developed probe was fast, cost-effective and operational convenience, and possessed high potential for TDM of MPA.

The preparation of flexible sensors on medical catheters is primarily an indirect process using certain materials as substrates. Using medical catheters as flexible substrates is beneficial for directly detecting the strain and contact force of the catheters. In this study, a strain sensor is prepared by rubbing graphite on a silicone medical catheter with a minimum inner diameter of 1 mm x 2 mm. The gauge factor (GF) of the strain sensor is adjusted by changing the resistance during preparation. By precisely controlling the composite material seepage zone, the maximum achievable GF is 121 at a low strain of 1%, which can be used to detect low forces with a resolution of 0.0013 N. Liquid glue is used to encapsulate the sensor, which barely changes the conductive network of the sensor. The response time of the strain sensor is 50 ms, and the performance of the sensor remains unchanged after 1000 cycles, which renders it suitable for intestinal shape detection. Additionally, we demonstrate the feasibility of integrating four strain sensors on the medical catheter to detect its bending direction via vector synthesis, which allows the spatial shape to be examined. The results obtained indicate the potential of the friction method for preparing strain sensors with different GFs on medical catheters to be used in different medical applications.& COPY; 2023 Vietnam National University, Hanoi. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

We design and fabricate the suspended silicon microring with racetrack and spiral structure to exploit the resonantly enhanced stimulated Brillouin scattering (SBS). The designed photonic-phononic waveguide can provide the independent control on the optical and acoustic modes by introducing the silicon ridge waveguide into the phononic crystal slab as a line defect. We demonstrate efficient forward SBS in the two kinds of microrings and extract the characteristic Brillouin parameters through the heterodyne four-wave mixing measurement. The stronger inhomogeneous broadening effect in the spiral microring due to the structural variations is also observed. In addition, our microrings show the single mode transmission spectrum and high quality factor, which is beneficial to the enhanced intramodal forward SBS. This design can readily extend to other silicon-based platforms and paves the way toward on-chip photonic-phononic signal processing and Brillouin amplifier technologies.

柔性压力传感器由于具有人体组织一样的柔软性在健康监测、电子皮肤和人机交互等领域扮演重要角色,21世纪物联网技术和人工智能的飞速发展带动了柔性压力传感器的应用热潮,其中柔性压阻式压力传感器因具有结构简单、易于制备、成本低的优点而被广泛使用.为了使柔性压阻式压力传感器能够应用于不同区间下的压力检测,科研人员通过材料选择和结构设计不断优化传感器的性能.本文从材料选择、制备方法和性能优化几个方面综述了近几年柔性压阻式压力传感器的发展动态,并从实际应用的角度出发对未来传感器的发展方向作出展望.

The rapid development of internet technology and artificial intelligence drives the demand for flexible sensors. Compared with vacuum technology and solution method, the fabrication of flexible sensors by pencil writing directly has advantages such as low cost, simple operation, low temperature, and no pollution. However, they are based on paper and rely on rigid fibers on the surface of it. The polymer is comfortable, portable and has excellent tensile properties, making it more suitable than paper as flexible substrates for wearable devices. In this paper, flexible pressure sensors and arrays are prepared by friction on polymers (Eco-flex、PDMS and bionic skin). The sensitivity of the prepared pressure sensor was 0.78 kPa−1 in the range of 20 kPa, and the response time was 400 ms, while the pressure detection ranged up to 160 kPa. Finally, it can be reused for 1000 cycles. As a wearable device, it can be applied to object grasping, muscle movement and respiratory monitoring. Furthermore, by combining the friction process with the transfer printing process, the stretchable flexible pressure sensor can be prepared on 3D cylindrical and curved hemispherical surfaces. Moreover, patterned sensors can also be prepared. It should be noted that the sensor can be cleaned after being discarded and has no pollution to the environment due to the mild type of materials, which is of certain significance for the development of flexible sensors towards green and low-cost development trends.

Aluminum scandium nitride (AlScN) has attracted extensive attention for its excellent piezoelectric properties in the micro‐electromechanical system applications. In this work, AlScN is demonstrated to be a promising candidate for on‐chip acousto‐optic coupling interactions with outstanding piezoelectric properties as well. Based on piezoelectric Al 0.6 Sc 0.4 N film deposited on silicon‐on‐insulator platform, the proposed devices exhibit impressive acousto‐optic coupling performances over a short interaction length of 210 µm with surface acoustic waves actuated by interdigital transducers. Meanwhile, the acousto‐optic coupling performances are further improved in a compact spiral waveguide with eight interaction segments, where the measured modulation efficiency is enhanced from −21.5 to −12.5 dB and the radiofrequency (RF) 3‐dB bandwidth is narrowed from 4 to 3.1 MHz at central frequency of 3.044 GHz with RF drive power of 18.6 dBm. The measured modulation efficiency is proportional to the incident RF drive power, depicting a linear increasing trend with a slope of one as the RF power increases up to 24.6 dBm. Such acousto‐optic devices are capable of achieving broadband acousto‐optic modulation and narrow‐band microwave photonic filtering. Besides, the designed device structure provides a prospect in single‐sideband modulation, acousto‐optic frequency shift, and nonreciprocal light propagation.

High-performance electrochromic materials with high optical contrast, coloration efficiency, and excellent stability have always been critical for polymer electrochromics, and will boost diverse applications including flexible displays and wearable electronics. Herein, we develop a donor-acceptor-donor type copolymer from strong electron-withdrawing acceptor unit isoindigo and electron-donating moiety bisEDOT by synthesizing and electropolymerizing its precursor (E)-1,1'-dihexyl-6,6'-bis(2,2',3,3'-tetrahydro-[5,5'-bithieno[3,4-b][1,4]dioxin]-7-yl)-[3,3'-biindolinylidene]-2,2' -dione (BisE -IDOH -BisE). Such polymer exhibits a low optical bandgap of 1.02 eV with stable and reversible electrochromism from kelly-green to sky blue. Further kinetic studies demonstrate that this polymer displays intriguing overall electrochromic performances throughout the NIR window with simultaneously high optical contrast up to 90%, high coloration efficiency of 1025 cm(2) C-1, fast switching time of 1.1 s, and excellent reversible stability (< 4% loss upon 50 0 0 cycling), which presents one of the best overall performances among the reported electrochromic polymers so far. With these amazing electrochromic properties, isoindigo-EDOT based polymers can be further developed towards device patterning and real applications like flexible indoor decoration displays and near infrared camouflage. (C) 2021 Elsevier Ltd. All rights reserved.