The different stacked heterostructures of transition metal dichalcogenides, which are the building blocks of moir & eacute; structures, represent a novel class of two-dimensional (2D) materials with promising applications in advanced optoelectronics and nonlinear photonics, while also providing a platform for fundamental studies of 2D semiconductor physics. In this work, we systematically investigate the linear and nonlinear optical (NLO) responses, as well as the linear electro-optical (LEO) properties, of MoS2/WS2 heterostructures with varying stack alignments using first-principles density functional theory and quasiparticle approximations. We observe a change in bandgap character between scalar and fully relativistic electronic band structures, which is preserved in both relativistic and quasiparticle band structures. We used quasiparticle band gaps and a scissors-correction method to calculate the second-harmonic generation (SHG) susceptibilities of these stackings. Our results show that the calculated SHG spectra of different stacking configurations are larger (in order of 10 3 pm V-1) in the visible-near-IR range, which is very high compared to the well-known commercial NLO materials, making these atomically thin stackings can be easily integrated with photonics and flexible electronics. The calculated LEO coefficients remain superior at similar to-3.5 pm V-1 in the low photon energy range and are significantly higher compared to those reported for the common semiconductors. These enhanced properties suggest the potential benefits of these van der Waals heterostructure stackings in nonlinear applications and demonstrate the amenability of MoS2/WS2 heterostructure stacking configurations to spectroscopic investigation.
Traditional photodetectors generally have the limitation of single-band detection, making it difficult to effectively distinguish multi-wavelength optical signals. In this study, by constructing a heterojunction structure of Cu2O and alpha-Ga2O3, a photodetection device with wavelength resolution capability was innovatively fabricated. Through the synergistic effect of the built-in electric field of the p-n junction and the semiconductor/electrolyte junction, this detector exhibits unique dual-wavelength response characteristics under 0 V. It generates photocurrents in opposite directions for ultraviolet (UV) light at 255 nm and 365 nm, respectively. Experimental data shows that the responsivity of this device reaches 3.6 mA W-1 under 255 nm UV light and -0.15 mA W-1 at 365 nm. Based on this bidirectional current characteristic, a differential signal encryption communication system was further designed and simulated, effectively avoiding the problem of signal interference in traditional optical communication. The research indicates that photodetectors composed of materials with different band gaps provide an effective way to distinguish different illumination bands, and their bidirectional current characteristics show broad application prospects in the fields of optical communication and optoelectronic devices.
In metal-oxide resistive gas sensors, conventional DC excitation often induces signal drift due to overheating, compromising long-term stability for hydrogen monitoring, particularly in humid environments. To overcome the inherent limitations of the DC mode, this study adopts pulsed excitation instead of DC excitation and applies it to a low-cost, screen-printed resistive sensor based on a platinum-modified indium oxide (Pt-In2O3) thin film for hydrogen detection at 50 degrees C. The Pt concentration and pulse duty cycle were optimized, and the dry and humid hydrogen sensing characteristics under both DC and pulsed excitation were systematically evaluated. Under pulsed excitation, the sensor achieved a detection limit of 2.63 ppm and exhibited a response to 0.1% hydrogen approximately twice that under DC conditions across a broad relative humidity range of 30%-70%. Moreover, the pulsed excitation effectively mitigated the detrimental effect of humidity on recovery kinetics. This phenomenon was explained by a proton current-dominated mechanism. This study establishes pulsed excitation as a simple yet powerful strategy to enhance the sensitivity, humidity tolerance, and stability of metal oxide semiconductor resistive hydrogen sensors, paving the way for their more reliable application in real-world conditions.
The rational design of synthesis pathways plays a decisive role in regulating the phase composition, interfacial architecture, and charge-transfer behavior of heterojunction photocatalysts, thereby directly governing their photocatalytic performance. In this work, a systematic methodology-directed investigation is conducted to construct bismuth-gallium oxide heterojunctions within the Bi25GaO39-Bi2Ga4O9-Bi2O3 system using three representative fabrication routes: hydrothermal-annealing, precipitation-pyrolysis, and impregnation. By deliberately tailoring the synthesis strategy, pure-phase Bi25GaO39 and Bi2Ga4O9, binary heterojunctions (Bi25GaO39/Bi2O3 and Bi2Ga4O9/Bi2O3), and a ternary Bi2Ga4O9/Bi25GaO39/Bi2O3 heterojunction are successfully obtained. Comprehensive structural, spectroscopic, and photoelectrochemical characterizations reveal that the hydrothermal-annealing route facilitates the formation of well-crystallized nanostructures with intimate interfacial contact, which is highly favorable for interfacial charge transfer. Among all samples, the ternary heterojunction exhibits the most efficient charge-separation behavior, as evidenced by the lowest charge-transfer resistance and the highest photocurrent response, and achieves a high methylene blue degradation efficiency of 96.58% under visible-light irradiation, outperforming the corresponding binary and single-phase counterparts. Radical trapping experiments combined with density functional theory calculations indicate that the enhanced activity originates from a staggered band alignment consistent with a type-II-like charge-transfer mechanism, which promotes directional spatial separation of photogenerated electrons and holes. Furthermore, an auxiliary intelligent photocatalytic evaluation platform based on RGB color analysis is developed to enable rapid and non-destructive monitoring of dye degradation. This study highlights the critical role of synthesis methodology in heterojunction interface engineering and provides a rational strategy for designing high-performance multicomponent photocatalysts through methodology-guided optimization.
Hydrogen sulfide sensors are censoriously important for environmental monitoring, industrial safety, and biomedical applications due to the highly toxic and corrosive nature of H2S gas. We report indium sulfide (In2S3) flakes were grown via chemical vapor deposition (CVD) and functionalized with palladium (Pd) nanoparticles(NPs) to develop a high-performance chemiresistive H2S gas sensor. The pristine In2S3 flakes have a porous microstructure with abundance of active sites, however the addition of Pd NPs improves the gas sensing response through enhancing charge transfer interactions along with providing catalytic spillover sites. The Pd-functionalized In2S3 sensor demonstrated a increase in respone (1.4-fold) and selectivity towards H2S, attaining a sensing response of approximately 67.60% at 50 ppm concentration at 75 degrees C. The sensor demonstrated rapid kinetics with response and recovery times of 48 s and 260 s, respectively, and a remarkably low limit of detection of 59 ppb. Furthermore, the sensor confirmed high humidity tolerance up to 80% RH and excellent repeatability. Density functional theory calculations discovered an 8-fold increase in adsorption energy (-1.51 eV) and significant charge transfer (-0.086 e(-)) upon Pd decoration, correlating the electronic sensitization of the Schottky barrier to the observed ppb-level sensitivity. With the use of first-principles calculations that explain the underlying sensing process, this work presents a practical strategy to develop efficient H2S gas sensors through the use of CVD-grown sulfide semiconductors with decoration of noble metal NPs.
This study investigated exciton-photon coupling in monolayer MoS2 integrated with a nanocorrugated SiN dielectric cavity, which supports tunable guided-mode resonances near a quasi-bound state in the continuum. The cavity exhibited a high quality-factor (Q-factor) of up to 6300 and near-field enhancement of approximately 220-2. By engineering the SiN thickness and corrugation geometry, the cavity resonance was tuned across the MoS2 A-exciton, enabling a transition from weak-coupling regime to a pronounced polaritonic regime, as indicated by the emergence of two strong transmission dips. Full-wave finite-element simulations combined with Lorentz oscillator dispersion modeling revealed clear anti-crossing behavior and narrow spectral features with a high Q-factor of approximately 340. Depending on the corrugation amplitude, a Rabi splitting of approximately 27 meV was achieved in conjunction with high-Q polariton modes, confirming a strong coupling regime. Furthermore, the curvature-induced strain introduced an additional tuning mechanism by modulating the exciton energy and detuning, thereby enabling controllable polariton dispersion while maintaining robust coupling strength. Results revealed that a nanocorrugated dielectric cavity with a facile configuration can serve as a scalable platform for strong light-matter interactions in two-dimensional materials and for designing high-Q exciton-polariton quantum devices.
The high theoretical capacity of metal vanadates is often negated by rapid capacity decay and inferior electrochemical response due to their structural reconstruction during lithiation. Herein, a Cu2V2O7 nanoflake architecture assembled on a conductive, doped graphitic carbon scaffold is synthesized via a coupled hydrothermal-annealing process, and the influence of varied thermal treatments on its morphology and lithium storage behavior is systematically investigated. Such synthesis spontaneously generates a multifunctional secondary CuO phase, which serves multiple purposes. It retards the single-step amorphization of Cu2V2O7 during initial discharge and establishes a heterophase interface with Cu2V2O7 to accelerate the Li-storage kinetics while contributing additional redox-active sites for extra capacity. Consequently, the C@Cu2V2O7 hybrid anode delivers a reversible capacity of 997.4 mAh g(-1) after 150 cycles at 0.1 A g(-1), and remarkably, even under a high current density of 2 A g(-1), it sustains a capacity of 366.07 mAh g(-1) over 2000 cycles with a capacity retention of 56.36% after 8000 cycles. These findings collectively endorse the in situ growth of a protective oxide layer as a potent design principle for high-performance metal vanadate-based anodes.
This paper presents a novel work function modulated Fin-channel schottky barrier diode (WFM-Fin-SBD) with optimized electrical characteristics. The architecture incorporates Ti as the Schottky metal on the Fin top surface to reduce the turn-on voltage (Von) and mitigate forward conduction loss. Simultaneously, Ni is selectively deposited on the Fin sidewalls and trenches bottom. This configuration ensures effective carrier depletion within the fin channel under both zero-bias and reverse-bias conditions, thereby suppressing reverse leakage current and enhancing the breakdown voltage. As a result, the WFM-Fin-SBD achieves superior performance metrics, including a low Von of 0.35 V, a specific on-resistance (Ron,sp) of 6.25 m Omega & centerdot;cm2, and a current density of 598 A cm-2 at 6 V. Under reverse bias, the enhanced depletion effect at the Ni/Ga2O3 interface effectively pinches off the conductive channel, which suppresses the leakage current and enables a breakdown voltage of -241 V, which is approximately 5.5 times that of conventional Ti-SBDs. Furthermore, frequency-dependent conductance measurements reveal that the interface trap density (Dit) of the WFM-Fin-SBD is situated between those of the Ti-SBD and the Ni-SBD. The slightly elevated Dit compared to the Ni-SBD is mainly attributed to the presence of Ti at the Fin top. Meanwhile, TCAD simulations elucidate the underlying physical mechanisms. The proposed WFM-Fin-SBD demonstrates superior performance, positioning it as a promising candidate for high-efficiency power electronics.
Heavy metal (HM) contamination from mining poses a long-term threat to agricultural soils. This study assessed the impacts of long-term HM exposure on soil microbial communities by comparing contaminated and uncontaminated agricultural soils from northwestern China. Using physicochemical analyses and high-throughput amplicon sequencing of bacterial and fungal communities, we assessed impacts on microbial community composition, co-occurrence networks, and predicted functions. HM contamination significantly reduced fungal α-diversity and altered the composition of both bacterial and fungal communities. The relative abundances of Actinobacteria, Acidobacteria, and Chloroflexi increased significantly in contaminated soils. Fungal communities were markedly enriched in Mortierellomycota. Notably, HM contamination substantially reduced the complexity of microbial co-occurrence networks, as indicated by fewer nodes, edges, and keystone taxa. Predictive functional profiling suggested an increased predicted abundance of functions related to HM resistance and detoxification, alongside shifts in core nutrient cycling potentials. Specifically, carbon and nitrogen metabolic pathways were altered, and the proportion of saprotrophic fungi increased, suggesting changes in organic matter decomposition dynamics. In conclusion, long-term HM stress is associated with a shift toward a simplified state, characterized by taxonomic restructuring, less complex co-occurrence networks, and a functional shift toward stress resistance and altered nutrient cycling.
