In Situ XPS Investigation of Transformations at Crystallographically Oriented MoS2 Interfaces

Three-dimensionally structured MoS2@biochar breaks through the bottleneck in antibiotic wastewater treatment: Greater efficiency and self-motivated oxidation pathway

Two-dimensional (2D) MoS2 has been widely used to remove antibiotics. However, low selectivity for antibiotic pollutants, dependence on applied energy and oxidant, and secondary contamination are still the bottlenecks of this system for treating antibiotic wastewater. In this study, we proposed a three-dimensional (3D) material (3MoS2/BMBC@MF) based on MoS2 and biochar with melamine sponge as the backbone. Compared with the 2D material (MoS2/BMBC), 3MoS2/BMBC@MF performed significantly better in enrofloxacin (ENR) removal, with an increase in the removal degree from 60.8 % to 88.1 %, and acted mainly through the degradation pathway rather than relying solely on the adsorption effect. It was shown that the direct oxidation process (DOP) behind the 3D materials is the key to the self-activated oxidation pathway. The three-dimensional structure enhances the generation and transfer pathways of persistent free radicals (PFRs) and electrons, realizing a multi-dimensional activation mechanism through its unique three-dimensional network, which greatly improves the redox capacity of the material. Upon exposure to pollutants, 3MoS2/BMBC@MF generates carbon-centered radicals of PFRs, which degrade ENR through mediated electron transfer. Coupled with the three-dimensional structure that contributes to the homogeneous dispersion of the active substances, dense steric active centers are formed in the grid skeleton by redox cycling of Mo ions to degrade antibiotics via DOP. Meanwhile, 3MoS2/BMBC@MF possesses good recyclability and maintains high efficiency in recycling. The structural design of this material not only enhances the removal efficiency and reduces the environmental impact, but also provides new potentials and solutions for practical water treatment of antibiotic contaminants.

Characterizing Electrode Materials and Interfaces in Solid-State Batteries

Solid-state batteries (SSBs) could offer improved energy density and safety, but the evolution and degradation of electrode materials and interfaces within SSBs are distinct from conventional batteries with liquid electrolytes and represent a barrier to performance improvement. Over the past decade, a variety of imaging, scattering, and spectroscopic characterization methods has been developed or used for characterizing the unique aspects of materials in SSBs. These characterization efforts have yielded new understanding of the behavior of lithium metal anodes, alloy anodes, composite cathodes, and the interfaces of these various electrode materials with solid-state electrolytes (SSEs). This review provides a comprehensive overview of the characterization methods and strategies applied to SSBs, and it presents the mechanistic understanding of SSB materials and interfaces that has been derived from these methods. This knowledge has been critical for advancing SSB technology and will continue to guide the engineering of materials and interfaces toward practical performance.

Interfacial Elemental Analysis of Slanted Edge-Contacted Monolayer MoS2 Transistors via Directionally Angled Etching

Edge contacts offer a significant advantage for enhancing the performance of semiconducting transition metal dichalcogenide (TMDC) devices by interfacing with the metallic contacts on the lateral side, which allows the encapsulation of all of the channel material. However, despite intense research, the fabrication of feasible electrical edge contacts to TMDCs to improve device performance remains a great challenge, as interfacial chemical characterization via conventional methods is lacking. A major bottleneck in explicitly understanding the chemical and electronic properties of the edge contact at the metal-two-dimensional (2D) semiconductor interface is the small cross section when characterizing nominally one-dimensional edge contacts. Here, we demonstrate a directional angled etching technique that enables the characterization of the interfacial chemistry at the metal-MoS2 junction when in an edge-contact configuration. The slanted edge structure provides a substantial cross section for elemental analysis of the edge contact by conventional X-ray photoemission spectroscopy, in which a simple chemical environment and sharp interface were revealed. Facilitated by the well-characterized contact interface, we realized slanted edge-contacted monolayer MoS2 transistors encapsulated by hexagonal boron nitride. The transport characteristics and photoluminescence of these transistors allowed us to attribute the efficient carrier injection to direct and Fowler-Nordheim tunneling, validating the distinct Au-MoS2 interface. The established method represents a viable approach to fabricating edge contacts with encapsulated 2D material devices, which is crucial for both the fundamental study of 2D materials and high-performance electronic applications.

Investigating the Effect of Carbon Nanotubes Decorated SmVO4-MoS2 Nanocomposite for Energy Storage Enhancement via VARTM-Fabricated Solid-State Structural Supercapacitors Using Woven Carbon Fiber

Traditional supercapacitors are cumbersome and need separate enclosures, which add weight and reduce space efficiency. In contrast, structural supercapacitors combine energy storage with load-bearing materials, optimizing space and weight for automotive and aerospace applications. This study investigates the synthesis of SmVO4-MoS2 and SmVO4-MoS2-CNT nanocomposites, focusing on optimizing CNT concentration in SmVO4-MoS2-CNT for high-performance supercapacitors. The optimal concentration of SmVO4-MoS2-CNT is identified and used to fabricate structural supercapacitor devices via the vacuum-assisted resin transfer molding (VARTM) technique. The results indicate that the specific capacitance of Sm-Mo-C5, using a three-electrode system, reached 1.01 F cm-2 at a current density of 2.187 mA cm-2. The performance improvement is attributed to the synergistic interaction among SmVO4, MoS2, and CNTs, collectively enhancing conductivity and active site availability. The practical application of this study is demonstrated by synthesizing Sm-Mo-C5 on woven carbon fiber (WCF) and subsequently fabricating a structural supercapacitor device (SSD) using the VARTM. The SSD, produced via VARTM, exhibited a specific capacitance of 0.287 F cm- 2 at a current density of 2 A cm-2. The device showcased exceptional cyclic stability, maintaining 72.5% of its initial capacitance after 50,000 charge-discharge cycles. Additionally, it achieved a maximum energy density of 79.86 Wh kg-1 at a power density of 1017.69 W kg-1.

Da Silva L, Luo Y, Lu Y, Huang C, Härk E, Fleming J, Chenevier P, Cabot A, Bai Y, Botifoll M, Black AP, An Q, Amietszajew T, Arbiol J. Mechanistic Insights and Technical Challenges in Sulfur-Based Batteries: A Comprehensive In Situ/Operando Monitoring Toolbox

Batteries based on sulfur cathodes offer a promising energy storage solution due to their potential for high performance, cost-effectiveness, and sustainability. However, commercial viability is challenged by issues such as polysulfide migration, volume changes, uneven phase nucleation, limited ion transport, and sluggish sulfur redox kinetics. Addressing these challenges requires insights into the structural, morphological, and chemical evolution of phases, the associated volume changes and internal stresses, and ion and polysulfide diffusion within the battery. Such insights can only be obtained through real-time reaction monitoring within the battery's operational environment, supported by molecular dynamics simulations and advanced artificial intelligence-driven data analysis. This review provides an overview of in situ/operando techniques for real-time tracking of these processes in sulfur-based batteries and explores the integration of simulations with experimental data to provide a holistic understanding of the critical challenges, enabling advancements in their development and commercial adoption.

Flexible and wearable sensor for in situ monitoring of gallic acid in plant leaves

Gallic acid (GA) is one of the main phenolic components naturally occurring in many plants and foods and has been a subject of increasing interest owing to its antioxidant and anti-mutagenic properties. This study introduces a novel flexible sensor designed for in situ detecting GA in plant leaves. The sensor employs a laser-induced graphene (LIG) flexible electrode, enhanced with MXene and molybdenum disulfide (MoS2) nanosheets. The MXene/MoS2/LIG flexible sensor not only demonstrates exceptional mechanical properties, covering a wide detection range of 1-1000 μM for GA, but also exhibits remarkable selectivity and stability. The as-prepared sensor was successfully applied to in situ determination of GA content in strawberry leaves under salt stress. This innovative sensor opens an attractive avenue for in situ measurement of metabolites in plant bodies with flexible electronics.

Simultaneously Producing H2 and H2O2 by Photocatalytic Water Splitting: Recent Progress and Future

The solar-driven overall water splitting (2H2O→2H2 + O2) is considered as one of the most promising strategies for reducing carbon emissions and meeting energy demands. However, due to the sluggish performance and high H2 cost, there is still a big gap for the current photocatalytic systems to meet the requirements for practical sustainable H2 production. Economic feasibility can be attained through simultaneously generating products of greater value than O2, such as hydrogen peroxide (H2O2, 2H2O→H2 + H2O2). Compared with overall water splitting, this approach is more kinetically feasible and generates more high-value products of H2 and H2O2. In several years, there has been an increasing surge in exploring the possibility and substantial progress has been achieved. In this review, a concise overview of the importance and underlying principles of PIWS is first provided. Next, the reported typical photocatalysts for PIWS are discussed, including commonly used semiconductors and cocatalysts, essential design features of these photocatalysts, and connections between their structures and activities, as well as the selected approaches for enhancing their stability. Then, the techniques used to quantify H2O2 and the operando characterization techniques that can be employed to gain a thorough understanding of the reaction mechanisms are summarized. Finally, the current existing challenges and the direction needing improvement are presented. This review aims to provide a thorough summary of the most recent research developments in PIWS and sets the stage for future advancements and discoveries in this emerging area.

In-Situ Characterization Techniques for Mechanism Studies of CO2 Hydrogenation

The paramount concerns of global warming, fossil fuel depletion, and energy crises have prompted the need of hydrocarbons productions via CO2 conversion. In order to achieve global carbon neutrality, much attention needs to be diverted towards CO2 management. Catalytic hydrogenation of CO2 is an exciting opportunity to curb the increasing CO2 and produce value-added products. However, the comprehensive understanding of CO2 hydrogenation is still a matter of discussion due to its complex reaction mechanism and involvement of various species. This review comprehensively discusses three processes: reverse water gas shift (RWGS) reaction, modified Fischer Tropsch synthesis (MFTS), and methanol-mediated route (MeOH) for CO2 hydrogenation to hydrocarbons. Along with analysing the reaction pathways, it is also very important to understand the real-time evolvement of catalytic process and reaction intermediates by employing in-situ characterization techniques under actual reaction conditions. Subsequently, in second part of this review, we provided a systematic analysis of advancements in in-situ techniques aimed to monitor the evolution of catalysts during CO2 reduction process. The section also highlights the key components of in-situ cells, their working principles, and applications in identifying reaction mechanisms for CO2 hydrogenation. Finally, by reviewing respective achievements in the field, we identify key gaps and present some future directions for CO2 hydrogenation and in-situ studies.

In Situ Characterization Techniques for Electrochemical Nitrogen Reduction Reaction

The electrochemical reduction of nitrogen to produce ammonia is pivotal in modern society due to its environmental friendliness and the substantial influence that ammonia has on food, chemicals, and energy. However, the current electrochemical nitrogen reduction reaction (NRR) mechanism is still imperfect, which seriously impedes the development of NRR. In situ characterization techniques offer insight into the alterations taking place at the electrode/electrolyte interface throughout the NRR process, thereby helping us to explore the NRR mechanism in-depth and ultimately promote the development of efficient catalytic systems for NRR. Herein, we introduce the popular theories and mechanisms of the electrochemical NRR and provide an extensive overview on the application of various in situ characterization approaches for on-site detection of reaction intermediates and catalyst transformations during electrocatalytic NRR processes, including different optical techniques, X-ray-based techniques, electron microscopy, and scanning probe microscopy. Finally, some major challenges and future directions of these in situ techniques are proposed.

Molybdenum Sulfide Nanoflowers as Electrodes for Efficient and Scalable Lithium-Ion Capacitors

Hybrid supercapacitors (HSCs) bridge the unique advantages of batteries and capacitors and are considered promising energy storage devices for hybrid vehicles and other electronic gadgets. Lithium-ion capacitors (LICs) have attained particular interest due to their higher energy and power density than traditional supercapacitor devices. The limited voltage window and the deterioration of anode materials upsurged the demand for efficient and stable electrode materials. Two-dimensional (2D) molybdenum sulfide (MoS2) is a promising candidate for developing efficient and durable LICs due to its wide lithiation potential and unique layer structure, enhancing charge storage efficiency. Modifying the extrinsic features, such as the dimensions and shape at the nanoscale, serves as a potential path to overcome the sluggish kinetics observed in the LICs. Herein, the MoS2 nanoflowers have been synthesized through a hydrothermal route. The developed LIC exhibited a specific capacitance of 202.4 F g-1 at 0.25 A g-1 and capacitance retention of >90 % over 5,000 cycles. Using an ether electrolyte improved the voltage window (2.0 V) and enhanced the stability performance. The ex-situ material characterization after the stability test reveals that the storage mechanism in MoS2-LICs is not diffusion-controlled. Instead, the fast surface redox reactions, especially intercalation/deintercalation of ions, are more prominent for charge storage.

MoO3 with the Synergistic Effect of Sulfur Doping and Oxygen Vacancies: The Influence of S Doping on the Structure, Morphology, and Optoelectronic Properties

Molybdenum trioxide (MoO3) is an attractive semiconductor. Thus, bandgap engineering toward photoelectronic applications is appealing yet not well studied. Here, we report the incorporation of sulfur atoms into MoO3, using sulfur powder as a source of sulfur, via a self-developed hydrothermal synthesis approach. The formation of Mo-S bonds in the MoO3 material with the synergistic effect of sulfur doping and oxygen vacancies (designated as S-MoO3-x) is confirmed using Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR). The bandgap is tuned from 2.68 eV to 2.57 eV upon sulfur doping, as confirmed by UV-VIS DRS spectra. Some MoS2 phase is identified with sulfur doping by referring to the photoluminescence (PL) spectra and electrochemical impedance spectroscopy (EIS), allowing significantly improved charge carrier separation and electron transfer efficiency. Therefore, the as-prepared S-MoO3-x delivers a sensitive photocurrent response and splendid cycling stability. This study on the synergistic effect of sulfur doping and oxygen vacancies provides key insights into the impact of doping strategies on MoO3 performance, paving new pathways for its optimization and development in relevant fields.

Defect-Driven MoS2 Nanosheets toward Enhanced Sensing Sensitivity

In this study, S-deficient MoS2 was prepared using proton irradiation and then applied as sensing materials for the detection of NO2 gas. First, bulk MoS2 was treated by ultrasonics to produce 2D nanosheets of MoS2, which were subsequently bombarded by a flux of high-energy protons, resulting in the appearance of structural defects throughout MoS2. The proton fluxes were adjusted to different densities of 1 × 1011, 1 × 1012, 1 × 1013, and 1 × 1014 ions/cm2. The effects of proton irradiation on the defects, also referred to as atomic vacancies, were systematically investigated using Raman measurements to locate the E1 2g and A1g modes and X-ray photoelectron spectroscopy to determine the binding energy of Mo 3d and S 2p orbitals. It was revealed that the density of proton irradiation greatly affects the degree of S atom vacancies in irradiated MoS2, while also enhancing the n-type semiconducting behaviors of MoS2. The vacancy-rich MoS2 was then demonstrated to exhibit a higher response to NO2 gas compared to that of nonirradiated MoS2, showing a 4-fold increase in response within a concentration range from 1 to 20 ppm. These results could pave the way for new approaches to fabricating sensing materials.

A Co-Reactive Immunosensor Based on Ti3C2Tx MXene@TiO2-MoS2 Hybrids Promoting luminol@Au@Ni-Co NCs Electrochemiluminescence for CYFRA 21-1 Detection

The construction of assays is capable of accurately detecting cytokeratin-19 (CYFRA 21-1), which is critical for the rapid diagnosis of nonsmall cell lung cancer. In this work, a novel electrochemiluminescence (ECL) immunosensor based on the co-reaction promotion of luminol@Au@Ni-Co nanocages (NCs) as ECL probe by Ti3C2Tx MXene@TiO2-MoS2 hybrids as co-reaction accelerator was proposed to detect CYFRA 21-1. Ni-Co NCs, as a derivative of Prussian blue analogs, can be loaded with large quantities of Au NPs, luminol, and CYFRA 21-1 secondary antibodies due to their high specific surface area. To further improve the sensitivity of the developed ECL immunosensor, Ti3C2Tx MXene@TiO2-MoS2 hybrids were prepared by in situ growth of TiO2 nanosheets on highly conductive Ti3C2Tx MXene, and MoS2 was homogeneously grown on Ti3C2Tx MXene@TiO2 surfaces by the hydrothermal method. Ti3C2Tx MXene@TiO2-MoS2 hybrids possess excellent catalytic performance on the electro-redox of H2O2 generating more O2·- and obtaining optimal ECL intensity of the luminol/H2O2 system. Under the appropriate experimental conditions, the quantitative detection range of CYFRA 21-1 was from 0.1 pg mL-1 to 100 ng mL-1, and the limit of detection (LOD) was 0.046 pg mL-1. The present sensor has a lower LOD with a wider linear range, which provides a new analytical assay for the early diagnosis of small-cell-type lung cancer labels.

Atomic Au3Cu Palisade Interlayer in Core@Shell Nanostructures for Efficient Kirkendall Effect Mediation

Plasmonic Cu@semiconductor heteronanocrystals (HNCs) have many favorable properties, but the synthesis of solid structures is often hindered by the nanoscale Kirkendall effect. Herein, we present the use of an atomically thin Au3Cu palisade interlayer to reduce lattice mismatch and mediate the Kirkendall effect, enabling the successive topological synthesis of Cu@Au3Cu@Ag, Cu@Au3Cu@Ag2S, and further transformed solid Cu@Au3Cu@CdS core-shell HNCs via cation exchange. The atomically thin and intact Au3Cu palisade interlayer effectively modulates the diffusion kinetics of Cu atoms as demonstrated by experimental and theoretical investigations and simultaneously alleviates the lattice mismatch between Cu and Ag as well as Cu and CdS. The Cu@Au3Cu@CdS HNCs feature exceptional crystallinity and atomically organized heterointerfaces between the plasmonic metal and the semiconductor. This results in the efficient plasmon-induced injection of hot electrons from Cu@Au3Cu into the CdS shell, enabling the Cu@Au3Cu@CdS HNCs to achieve high activity and selectivity for the photocatalytic reduction of CO2 to CO.

Mn-promoted MoS2 catalysts for CO2 hydrogenation: enhanced methanol selectivity due to MoS2/MnOx interfaces

Considering the alarming scenario of climate change, CO2 hydrogenation to methanol is considered a key process for phasing out fossil fuels by means of CO2 utilization. In this context, MoS2 catalysts have recently shown to be promising catalysts for this reaction, especially in the presence of abundant basal-plane sulfur vacancies and due to synergistic mechanisms with other phases. In this work, Mn-promoted MoS2 prepared by a hydrothermal method presents considerable selectivity for CO2 hydrogenation to methanol in comparison with pure MoS2 and other promoters such as K and Co. Interestingly, if CO is used as a carbon source for the reaction, methanol production is remarkably lower, which suggests the absence of a CO intermediate during CO2 hydrogenation to methanol. After optimization of synthesis parameters, a methanol selectivity of 64% is achieved at a CO2 conversion of 2.8% under 180 °C. According to material characterization by X-ray Diffraction and X-ray Absorption, the Mn promoter is present mainly in the form of MnO and MnCO3 phases, with the latter undergoing convertion to MnO upon H2 pretreatment. However, following exposure to reaction conditions, X-ray photoelectron spectroscopy suggests that higher oxidation states of Mn may be present at the surface, suggesting that the improved catalytic activity for CO2 hydrogenation to methanol arises from a synergy between MoS2 and MnOx at the catalyst surface.

Pseudocapacitance-Induced Synaptic Plasticity of Tribo-Phototronic Effect Between Ionic Liquid and 2D MoS2

Contact-induced electrification, commonly referred to as triboelectrification, is the subject of extensive investigation at liquid-solid interfaces due to its wide range of applications in electrochemistry, energy harvesting, and sensors. This study examines the triboelectric between an ionic liquid and 2D MoS2 under light illumination. Notably, when a liquid droplet slides across the MoS2 surface, an increase in the generated current and voltage is observed in the forward direction, while a decrease is observed in the reverse direction. This suggests a memory-like tribo-phototronic effect between ionic liquid and 2D MoS2 . The underlying mechanism behind this tribo-phototronic synaptic plasticity is proposed to be ion adsorption/desorption processes resulting from pseudocapacitive deionization/ionization at the liquid-MoS2  interface. This explanation is supported by the equivalent electrical circuit modeling, contact angle measurements, and electronic band diagrams. Furthermore, the influence of various factors such as velocity, step size, light wavelength and intensity, ion concentration, and bias voltage is thoroughly investigated. The artificial synaptic plasticity arising from this phenomenon exhibits significant synaptic features, including potentiation/inhibition, paired-pulse facilitation/depression, and short-term memory (STM) to long-term memory (LTM) transition. This research opens up promising avenues for the development of synaptic memory systems and intelligent sensing applications based on liquid-solid interfaces.

Potential window alignment regulating ion transfer in faradaic junctions for efficient photoelectrocatalysis

In the past decades, a band alignment theory has become a basis for designing different high-performance semiconductor devices, such as photocatalysis, photoelectrocatalysis, photoelectrostorage and third-generation photovoltaics. Recently, a faradaic junction model (coupled electron and ion transfer) has been proposed to explain charge transfer phenomena in these semiconductor heterojunctions. However, the classic band alignment theory cannot explain coupled electron and ion transfer processes because it only regulates electron transfer. Therefore, it is very significant to explore a suitable design concept for regulating coupled electron and ion transfer in order to improve the performance of semiconductor heterojunctions. Herein, we propose a potential window alignment theory for regulating ion transfer and remarkably improving the photoelectrocatalytic performance of a MoS2/Cd-Cu2ZnSnS4 heterojunction photocathode. Moreover, we find that a faradaic potential window, rather than the band position of the intermediate layer, is a criterion for identifying interface charge transfer direction. This finding can offer different perspectives for designing high-performance semiconductor heterojunctions with suitable potential windows for solar energy conversion and storage.

Nanoporous MoS2 Field-Effect Transistor Based Artificial Olfaction: Achieving Enhanced Volatile Organic Compound Detection Inspired by the Drosophila Olfactory System

Olfaction, a primal and effective sense, profoundly impacts our emotions and instincts. This sensory system plays a crucial role in detecting volatile organic compounds (VOCs) and realizing the chemical environment. Animals possess superior olfactory systems compared to humans. Thus, taking inspiration from nature, artificial olfaction aims to achieve a similar level of excellence in VOC detection. In this study, we present the development of an artificial olfaction sensor utilizing a nanostructured bio-field-effect transistor (bio-FET) based on transition metal dichalcogenides and the Drosophila odor-binding protein LUSH. To create an effective sensing platform, we prepared a hexagonal nanoporous structure of molybdenum disulfide (MoS2) using block copolymer lithography and selective etching techniques. This structure provides plenty of active sites for the integration of the LUSH protein, enabling enhanced binding with ethanol (EtOH) for detection purposes. The coupling of the biomolecule with EtOH influences the bio-FETs potential, which generates indicative electrical signals. By mimicking the sniffing techniques observed in Drosophila, these bio-FETs exhibit an impressive limit of detection of 10-6% for EtOH, with high selectivity, sensitivity, and detection ability even in realistic environments. This bioelectric sensor demonstrates substantial potential in the field of artificial olfaction, offering advancements in VOC detection.

Integrated Logic Circuits Based on Wafer-Scale 2D-MoS2 FETs Using Buried-Gate Structures

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) materials, such as molybdenum disulfide (MoS2), stand out due to their atomically thin layered structure and exceptional electrical properties. Consequently, they could potentially become one of the main materials for future integrated high-performance logic circuits. However, the local back-gate-based MoS2 transistors on a silicon substrate can lead to the degradation of electrical characteristics. This degradation is caused by the abnormal effect of gate sidewalls, leading to non-uniform field controllability. Therefore, the buried-gate-based MoS2 transistors where the gate electrodes are embedded into the silicon substrate are fabricated. The several device parameters such as field-effect mobility, on/off current ratio, and breakdown voltage of gate dielectric are dramatically enhanced by field-effect mobility (from 0.166 to 1.08 cm2/V·s), on/off current ratio (from 4.90 × 105 to 1.52 × 107), and breakdown voltage (from 15.73 to 27.48 V) compared with a local back-gate-based MoS2 transistor, respectively. Integrated logic circuits, including inverters, NAND, NOR, AND, and OR gates, were successfully fabricated by 2-inch wafer-scale through the integration of a buried-gate MoS2 transistor array.

Molybdenum disulfide-loaded multilayer AuNPs with colorimetric-SERS dual-signal enhancement activities for flexible immunochromatographic diagnosis of monkeypox virus

The sudden outbreak of monkeypox in 2022 suggests the importance of developing a rapid but sensitive virus detection technology. Herein, we report a colorimetric/surface-enhanced Raman scattering (SERS) dual-signal co-enhanced immunochromatographic assay (ICA) for the flexible, ultrasensitive, and accurate detection of monkeypox virus (MPXV) in various complex samples. A thickness-controlled polyethyleneimine interlayer (1 nm) is coated onto two-dimensional molybdenum disulfide (MoS2) nanosheet to enable the electrostatic adsorption of two layers of dense 30 nm AuNPs, which not only improves colorimetric ability but also creates numerous efficient SERS hotspots. Moreover, the SERS activity of film-like dual-signal tag (MoS2@Au-Au) is drastically enhanced by combining the chemical enhancement effect of MoS2 sheets and the electromagnetic enhancement effect of Au-Au hotspots. The introduction of MoS2@Au-Au greatly broadens the application range of existing ICA methods, in which the colorimetric signal supports the quick identification of the target virus and the SERS signal allows the quantitative detection of MPXV with detection limits of as low as 0.2 and 0.002 ng/mL. Given its rapid detection ability (< 20 min), high accuracy in real samples (RSD < 9.89 %), and superior sensitivity than traditional AuNP-based colorimetric ICA (> 500 times), the proposed assay has great potential for field application.

Synthesis of a large area ReS2 thin film by CVD for in-depth investigation of resistive switching: effects of metal electrodes, channel width and noise behaviour

The anisotropic crystal structure and layer independent electrical and optical properties of ReS2 make it unique among other two-dimensional materials (2DMs), emphasizing a special need for its synthesis. This work discusses the synthesis and in-depth characterization of a 1 × 1 cm2 large and few layered ReS2 film. Vibrational modes and excitonic peaks observed from the Raman and photoluminescence (PL) spectra corroborated the formation of a ReS2 film with a 1.26 eV bandgap. High resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) patterns inferred the polycrystalline nature of the film, while cross-sectional field emission scanning electron microscopy (FESEM) indicated planar growth with ∼10 nm thickness. The chemical composition of the film analysed through X-ray photoelectron spectroscopy (XPS) indicated the formation of a ReS2 film with a Re : S atomic ratio of 1 : 1.75, indicating a small amount of non-stoichiometric RexSy. Following the basic characterization studies, the ReS2 film was tested for resistive switching (RS) device application in which the effects of different metal electrodes (Pt/Au and Ag/Au) and different channel widths (200, 100, and 50 μm) were studied. The highest memory window equal to 108 was obtained for the Ag/Au electrode while Pt/Au showed a memory window of 102. RS for the former was ascribed to the formation of a conducting filament (CF) because of the migration of Ag+ ions, while defect mediated charge carrier transport led to switching in the Pt/Au electrode. Furthermore, the RHRS/RLRS ratio achieved in this work (108) is also of the highest magnitude reported thus far. Furthermore, a comparison of devices with Ag/Au electrodes but with different channel widths (50, 100 and 200 μm) gave insightful results on the existence of multiple resistance states, device endurance and retention. An inverse relationship between the retention time and the device's channel width was observed, where the device with a 50 μm channel width showed a retention time of 48 hours, and the one with a 200 μm width showed stability only up to 3000 s. Furthermore, low frequency noise measurements were performed to understand the effect of defects in the low resistance state (LRS) and the high resistance state (HRS). The HRS exhibited Lorentzian noise behaviour while the LRS exhibited Lorentzian only at low current bias which converged to 1/f noise at higher current bias.

Effect of gamma irradiation on the physical properties of MoS2 monolayer

Two-dimensional transition metal dichalcogenides (2D-TMDs) have been proposed as novel optoelectronic materials for space applications due to their relatively light weight. MoS2 has been shown to have excellent semiconducting and photonic properties. Although the strong interaction of ionizing gamma radiation with bulk materials has been demonstrated, understanding its effect on atomically thin materials has scarcely been investigated. Here, we report the effect of gamma irradiation on the structural and electronic properties of a monolayer of MoS2. We perform Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) studies of MoS2, before and after gamma ray irradiation with varying doses and density functional theory (DFT) calculations. The Raman spectra and XPS results demonstrate that point defects dominate after the gamma irradiation of MoS2. DFT calculations elucidate the electronic properties of MoS2 before and after irradiation. Our work makes several contributions to the field of 2D materials research. First, our study of the electronic density of states and the electronic properties of a MoS2 monolayer irradiated by gamma rays sheds light on the properties of a MoS2 monolayer under gamma irradiation. Second, our study confirms that point defects are formed as a result of gamma irradiation. And third, our DFT calculations qualitatively suggest that the conductivity of the MoS2 monolayer may increase after gamma irradiation due to the creation of additional defect states.

Lithium-Induced Reorientation of Few-Layer MoS2 Films

Molybdenum disulfide (MoS2) few-layer films have gained considerable attention for their possible applications in electronics and optics and also as a promising material for energy conversion and storage. Intercalating alkali metals, such as lithium, offers the opportunity to engineer the electronic properties of MoS2. However, the influence of lithium on the growth of MoS2 layers has not been fully explored. Here, we have studied how lithium affects the structural and optical properties of the MoS2 few-layer films prepared using a new method based on one-zone sulfurization with Li2S as a source of lithium. This method enables incorporation of Li into octahedral and tetrahedral sites of the already prepared MoS2 films or during MoS2 formation. Our results discover an important effect of lithium promoting the epitaxial growth and horizontal alignment of the films. Moreover, we have observed a vertical-to-horizontal reorientation in vertically aligned MoS2 films upon lithiation. The measurements show long-term stability and preserved chemical composition of the horizontally aligned Li-doped MoS2.

Room-Temperature Photoluminescence Mediated by Sulfur Vacancies in 2D Molybdenum Disulfide

Atomic defects in monolayer transition metal dichalcogenides (TMDs) such as chalcogen vacancies significantly affect their properties. In this work, we provide a reproducible and facile strategy to rationally induce chalcogen vacancies in monolayer MoS₂ by annealing at 600 °C in an argon/hydrogen (95%/5%) atmosphere. Synchrotron X-ray photoelectron spectroscopy shows that a Mo 3d_5/2 core peak at 230.1 eV emerges in the annealed MoS₂ associated with nonstoichiometric MoS_x (0 < x < 2), and Raman spectroscopy shows an enhancement of the ∼380 cm^-1 peak that is attributed to sulfur vacancies. At sulfur vacancy densities of ∼1.8 × 10¹⁴ cm^-2, we observe a defect peak at ∼1.72 eV (referred to as LX_D) at room temperature in the photoluminescence (PL) spectrum. The LX_D peak is attributed to excitons trapped at defect-induced in-gap states and is typically observed only at low temperatures (≤77 K). Time-resolved PL measurements reveal that the lifetime of defect-mediated LX_D emission is longer than that of band edge excitons, both at room and low temperatures (∼2.44 ns at 8 K). The LX_D peak can be suppressed by annealing the defective MoS₂ in sulfur vapor, which indicates that it is possible to passivate the vacancies. Our results provide insights into how excitonic and defect-mediated PL emissions in MoS₂ are influenced by sulfur vacancies at room and low temperatures.

A Wafer-Scale Nanoporous 2D Active Pixel Image Sensor Matrix with High Uniformity, High Sensitivity, and Rapid Switching

2D transition-metal dichalcogenides (TMDs) have been successfully developed as novel ubiquitous optoelectronics owing to their excellent electrical and optical characteristics. However, active-matrix image sensors based on TMDs have limitations owing to the difficulty of fabricating large-area integrated circuitry and achieving high optical sensitivity. Herein, a large-area uniform, highly sensitive, and robust image sensor matrix with active pixels consisting of nanoporous molybdenum disulfide (MoS₂ ) phototransistors and indium-gallium-zinc oxide (IGZO) switching transistors is reported. Large-area uniform 4-inch wafer-scale bilayer MoS₂ films are synthesized by radio-frequency (RF) magnetron sputtering and sulfurization processes and patterned to be a nanoporous structure consisting of an array of periodic nanopores on the MoS₂ surface via block copolymer lithography. Edge exposure on the nanoporous bilayer MoS₂ induces the formation of subgap states, which promotes a photogating effect to obtain an exceptionally high photoresponsivity of 5.2 × 10⁴ A W^-1 . A 4-inch-wafer-scale image mapping is successively achieved using this active-matrix image sensor by controlling the device sensing and switching states. The high-performance active-matrix image sensor is state-of-the-art in 2D material-based integrated circuitry and pixel image sensor applications.

Hydrothermally Grown MoS2 as an Efficient Electrode Material for the Fabrication of a Resorcinol Sensor

Recently, the active surface modification of glassy carbon electrodes (GCE) has received much attention for the development of electrochemical sensors. Nanomaterials are widely explored as surface-modifying materials. Herein, we have reported the hydrothermal synthesis of molybdenum disulfide (MoS₂) and its electro-catalytic properties for the fabrication of a resorcinol sensor. Structural properties such as surface morphology of the prepared MoS₂ was investigated by scanning electron microscopy and phase purity was examined by employing the powder X-ray diffraction technique. The presence of Mo and S elements in the obtained MoS₂ was confirmed by energy-dispersive X-ray spectroscopy. Finally, the active surface of the glassy carbon electrode was modified with MoS₂. This MoS₂-modified glassy carbon electrode (MGC) was explored as a potential candidate for the determination of resorcinol. The fabricated MGC showed a good sensitivity of 0.79 µA/µMcm² and a detection limit of 1.13 µM for the determination of resorcinol. This fabricated MGC also demonstrated good selectivity, and stability towards the detection of resorcinol.

Enhancing Photodetection Ability of MoS2 Nanoscrolls via Interface Engineering

Van der Waals semiconductors have been really confirmed in two-dimensional (2D) layered systems beyond the traditional limits of lattice-matching requirements. The extension of this concept to the 1D atomic level may generate intriguing physical functionalities due to its non-covalent bonding surface. However, whether the curvature of the lattice in such rolled-up structures affects their optoelectronic features or the performance of devices established on them remains an open question. Here, MoS₂-based nanoscrolls were obtained by virtue of an alkaline solution-assisted method and the 0D/1D (BaTiO₃/MoS₂) strategy to tune their optoelectronic properties and improve the light sensing performance was explored. The capillary force generated by a drop of NaHCO₃ solution could drive the delamination of nanosheets from the underlying substrate and a spontaneous rolling-up process. The package of BaTiO₃ particles in MoS₂ nanoscrolls has been evident by TEM image, and the optical characterizations were mirrored via micro-Raman spectroscopy and photoluminescence. These bare MoS₂ nanoscrolls reveal a reduced photoresponse compared to the plane structures due to the curvature of the lattice. However, such BaTiO₃/MoS₂ nanoscrolls exhibit a significantly improved photodetection (R_hybrid = 73.9 A/W vs R_only = 1.1 A/W and R_2D = 1.5 A/W at 470 nm, 0.58 mW·cm^-2), potentially due to the carrier extraction/injection occurring between BaTiO₃ and MoS₂. This study thereby provides an insight into 1D van der Waals material community and demonstrates a general approach to fabricate high-performance 1D van der Waals optoelectronic devices.

Band Alignments, Electronic Structure, and Core-Level Spectra of Bulk Molybdenum Dichalcogenides (MoS2, MoSe2, and MoTe2)

A comprehensive study of bulk molybdenum dichalcogenides is presented with the use of soft and hard X-ray photoelectron (SXPS and HAXPES) spectroscopy combined with hybrid density functional theory (DFT). The main core levels of MoS₂, MoSe₂, and MoTe₂ are explored. Laboratory-based X-ray photoelectron spectroscopy (XPS) is used to determine the ionization potential (IP) values of the MoX₂ series as 5.86, 5.40, and 5.00 eV for MoSe₂, MoSe₂, and MoTe₂, respectively, enabling the band alignment of the series to be established. Finally, the valence band measurements are compared with the calculated density of states which shows the role of p-d hybridization in these materials. Down the group, an increase in the p-d hybridization from the sulfide to the telluride is observed, explained by the configuration energy of the chalcogen p orbitals becoming closer to that of the valence Mo 4d orbitals. This pushes the valence band maximum closer to the vacuum level, explaining the decreasing IP down the series. High-resolution SXPS and HAXPES core-level spectra address the shortcomings of the XPS analysis in the literature. Furthermore, the experimentally determined band alignment can be used to inform future device work.

A novel Fe/Mo co-catalyzed graphene-based nanocomposite to activate peroxymonosulfate for highly efficient degradation of organic pollutants

A novel 3D α-FeOOH@MoS₂/rGO nanocomposite was successfully fabricated by a simple in situ hydrothermal method. It is a highly efficient heterogeneous catalyst in activation of peroxymonosulfate (PMS) for rapid degradation of rhodamine B (RhB), with 99.9% of RhB removed within 20 min. The introduction of rGO contributes to uniform dispersion and sufficient contact of α-FeOOH and MoS₂ nanosheets. Highly active Mo(IV) enhances the reduction of Fe(III), improves Fe(III)/Fe(II) conversion and promotes the generation of O₂1, which ensures an improved catalytic activity. MoS₂/rGO hybrid can effectively solve the problem of material reunion and make α-FeOOH exhibit excellent catalytic performance. The α-FeOOH@MoS₂-rGO/PMS system is a co-catalytic system based on the active components of α-FeOOH and MoS₂. The main reactive oxygen species in the α-FeOOH@MoS₂-rGO/PMS system are O₂1, SO₄^.- and ⋅O₂^-, which contribute to a high reactivity over a wide range of pH (5-9). Besides, this system is highly resistant to anions (Cl^-, SO₄^2-) and natural organic matter (humic acid), and can be widely used for degradation of common organic pollutants. The α-FeOOH@MoS₂/rGO is a promising Fenton-like catalyst for refractory organic wastewater treatment.

Active pixel sensor matrix based on monolayer MoS2 phototransistor array

In-sensor processing, which can reduce the energy and hardware burden for many machine vision applications, is currently lacking in state-of-the-art active pixel sensor (APS) technology. Photosensitive and semiconducting two-dimensional (2D) materials can bridge this technology gap by integrating image capture (sense) and image processing (compute) capabilities in a single device. Here, we introduce a 2D APS technology based on a monolayer MoS₂ phototransistor array, where each pixel uses a single programmable phototransistor, leading to a substantial reduction in footprint (900 pixels in ∼0.09 cm²) and energy consumption (100s of fJ per pixel). By exploiting gate-tunable persistent photoconductivity, we achieve a responsivity of ∼3.6 × 10⁷ A W^-1, specific detectivity of ∼5.6 × 10¹³ Jones, spectral uniformity, a high dynamic range of ∼80 dB and in-sensor de-noising capabilities. Further, we demonstrate near-ideal yield and uniformity in photoresponse across the 2D APS array.

Ultrasensitive and Selective Field-Effect Transistor-Based Biosensor Created by Rings of MoS2 Nanopores

The ubiquitous field-effect transistor (FET) is widely used in modern digital integrated circuits, computers, communications, sensors, and other applications. However, reliable biological FET (bio-FET) is not available in real life due to the rigorous requirement for highly sensitive and selective bio-FET fabrication, which remains a challenging task. Here, we report an ultrasensitive and selective bio-FET created by the nanorings of molybdenum disulfide (MoS₂) nanopores inspired by nuclear pore complexes. We characterize the nanoring of MoS₂ nanopores by scanning transmission electron microscopy, Raman, and X-ray photoelectron spectroscopy spectra. After fabricating MoS₂ nanopore rings-based bio-FET, we confirm edge-selective functionalization by the gold nanoparticle tethering test and the change of electrical signal of the bio-FET. Ultrahigh sensitivity of the MoS₂ nanopore edge rings-based bio-FET (limit of detection of 1 ag/mL) and high selectivity are accomplished by effective coupling of the aptamers on the nanorings of the MoS₂ nanopore edge for cortisol detection. We believe that MoS₂ nanopore edge rings-based bio-FET would provide platforms for everyday biosensors with ultrahigh sensitivity and selectivity.

Melting, Crystallization, and Alloying Dynamics in Nanoscale Bismuth Telluride

It is critical to understand the transformation mechanisms in layered metal chalcogenides to enable controlled synthesis and processing. Here, we develop an alumina encapsulation layer-based in situ transmission electron microscopy (TEM) setup that enables the investigation of melting, crystallization, and alloying of nanoscale bismuth telluride platelets while limiting sublimation in the high-vacuum TEM environment. Heating alumina-encapsulated platelets to 700 °C in situ resulted in melting that initiated at edge planes and proceeded via the movement of a sharp interface. The encapsulated melt was then cooled to induce solidification, with individual nuclei growing to form single crystals with the same basal plane orientation as the original platelet and nonequilibrium crystal shapes imposed by the encapsulation layer. Finally, heating platelets in the presence of antimony caused alloying and lattice strain, along with heterogeneous phase formation. These findings provide new insight into important transformation processes in layered metal chalcogenide materials.

Visible-light-driven peroxymonosulfate activation in photo-electrocatalytic system using hollow-structured Pt@CeO2@MoS2 photoanode for the degradation of pharmaceuticals and personal care products

In this study, we constructed an innovative photo-electrocatalysis-assisted peroxymonosulfate (PEC/PMS) system to degrade pharmaceuticals and personal care products (PPCPs). A hollow-structured photoanode (i.e., Pt@CeO₂@MoS₂) was specifically synthesized as a photoanode to activate PMS in the PEC system. As proof of concept, the Pt@CeO₂@MoS₂ photoanode exhibited superior degradation performance toward carbamazepine (CBZ) with PMS assistance. Specifically, the kinetic constant of PEC/PMS (k = 0.13202 min^-1) could be enhanced about 87.4 times compared to that of the PEC system (0.00151 min^-1) alone. The PMS activation mechanism revealed that the synergistic effect between the hollow material and the change of surface valence states (Ce³⁺ to Ce⁴⁺) and (Mo⁴⁺ to Mo⁶⁺) contribute to enhancing the degradation efficiency of the visible-light-driven PEC/PMS process. The scavenger testing and EPR showed that ¹O₂, O₂^•-, SO₄^•- and •OH play dominant roles in the SR-AOPs. Furthermore, the applicability of Pt@CeO₂@MoS₂ used in SR-AOPs was systematically investigated regarding of the reaction parameters and identification of intermediates and dominant radicals as well as the mineralization rate and stability. The outcomes of this study can provide a new platform for environmental remediation.

Roadmap and Direction toward High-Performance MoS2 Hydrogen Evolution Catalysts

MoS₂ intrinsically show Pt-like hydrogen evolution reaction (HER) performance. Pristine MoS₂ displayed low HER activity, which was caused by low quantities of catalytic sites and unsatisfactory conductivity. Then, phase engineering and S vacancy were developed as effective strategies to elevate the intrinsic HER performance. Heterojunctions and dopants were successful strategies to improve HER performance significantly. A couple of state-of-the-art MoS₂ catalysts showed HER performance comparable to Pt. Applying multiple strategies in the same electrocatalyst was the key to furnish Pt-like HER performance. In this review, we summarize the available strategies to fabricate superior MoS₂ HER catalysts and tag the important works. We analyze the well-defined strategies for fabricating a superior MoS₂ electrocatalyst, propose complementary strategies which could help meet practical requirements, and help people design highly efficient MoS₂ electrocatalysts. We also provide a brief perspective on assembling practical electrochemical systems by high-performance MoS₂ electrocatalysts, apply MoS₂ in other important electrocatalysis reactions, and develop high-performance two-dimensional (2D) dichalcogenide HER catalysts not limited to MoS₂. This review will help researchers to obtain a better understanding of development of superior MoS₂ HER electrocatalysts, providing directions for next-generation catalyst development.

Dissolution of 2D Molybdenum Disulfide Generates Differential Toxicity among Liver Cell Types Compared to Non-Toxic 2D Boron Nitride Effects

2D boron nitride (BN) and molybdenum disulfide (MoS2 ) materials are increasingly being used for applications due to novel chemical, electronic, and optical properties. Although generally considered biocompatible, recent data have shown that BN and MoS2 could potentially be hazardous under some biological conditions, for example, during, biodistribution of drug carriers or imaging agents to the liver. However, the effects of these 2D materials on liver cells such as Kupffer cells (KCs), liver sinusoidal endothelial cells, and hepatocytes, are unknown. Here, the toxicity of BN and MoS2 , dispersed in Pluronic F87 (designated BN-PF and MoS2 -PF) is compared with aggregated forms of these materials (BN-Agg and MoS2 -Agg) in liver cells. MoS2 induces dose-dependent cytotoxicity in KCs, but not other cell types, while the BN derivatives are non-toxic. The effect of MoS2 could be ascribed to nanosheet dissolution and the release of hexavalent Mo, capable of inducing mitochondrial reactive oxygen species generation and caspases 3/7-mediated apoptosis in KUP5 cells. In addition, the phagocytosis of MoS2 -Agg triggers an independent response pathway involving lysosomal damage, NLRP3 inflammasome activation, caspase-1 activation, IL-1β, and IL-18 production. These findings demonstrate the importance of Mo release and the state of dispersion of MoS2 in impacting KC viability.

MoS2 Nanocomposite Films with High Irradiation Tolerance and Self-Adaptive Lubrication

Although nanostructures and oxide dispersion can reduce radiation-induced damage in materials and enhance radiation tolerance, previous studies prove that MoS₂ nanocomposite films subjected to several dpa heavy ion irradiation show significant degradation of tribological properties. Even in YSZ-doped MoS₂ nanocomposite films, irradiation leads to obvious disordering and damage such as vacancy accumulation to form lamellar voids in the amorphous matrix, which accelerates the failure of lubrication. However, after thermal annealing in vacuum, YSZ-doped MoS₂ nanocomposite films exhibit high irradiation tolerance, and their wear duration remains unchanged and the wear rate was nearly three orders of magnitude lower than that of the as-deposited films after 7 dpa irradiation. This successful combination of anti-irradiation and self-adaptive lubrication mainly results from the manipulation of the nanosize and the change of composition by annealing. Compared with the smaller nanograins in as-deposited MoS₂/YSZ nanocomposite films, the thermally annealed MoS₂ nanocrystals (7-15 nm) with fewer intrinsic defects exhibited remarkable stabilization upon irradiation. Abundant amorphous nanocrystal phases in ion-irradiated thermally annealed films, where each has advantages of their own, greatly inhibit accumulation of voids and crack growth in irradiation; meanwhile, they can be easily self-assembled under induction of friction and achieve self-adaptive lubrication.

Fabrication of an Au25 -Cys-Mo Electrocatalyst for Efficient Nitrogen Reduction to Ammonia under Ambient Conditions

Electrocatalysts for efficient production of ammonia from nitrogen reduction reaction (NRR) under ambient conditions are attracted growing interest in recent years, which demonstrate a great potential to replace the Haber-Bosch method which suffers the problems of the huge energy consumption and massive CO₂ production. In this work, a novel electrocatalyst of Au₂₅ -Cys-M is fabricated for NRR under ambient conditions, with transition metal ions (e.g., Mo⁶⁺ , Fe³⁺ , Co²⁺ , Ni²⁺ ) atomically decorated on Au₂₅ nanoclusters via thiol bridging. The Au₂₅ -Cys-Mo catalyst exhibits the highest Faradaic efficiency (26.5%) and NH₃ yield (34.5 µg h^-1  mg_cat ^-1 ) in 0.1 m HCl solution. X-ray photoelectron spectroscopy analysis and high angle annular dark field image-scanning transmission electron microscopy characterization reveal that the electronic structure of Mo is optimized by forming the structure of Au-S-Mo and Mo acts as active sites for activating the nitrogen to promote the electrochemical production of ammonia. This work provides a new insight into the precise fabrication of efficient NRR electrocatalysts.

Constructing MoS2/Lignin-derived carbon nanocomposites for highly efficient removal of Cr(VI) from aqueous environment

Effective removal of Cr(VI) pollution from aquatic environment is in pressing need because of the detrimental effect of Cr(VI) to human health. Herein, we report a facile two-step approach to synthesis MoS₂/Lignin-derived Carbon (MoS₂@LDC) nanocomposites for highly efficient elimination of Cr(VI) from aqueous solutions. The MoS₂@LDC exhibited outstanding removal efficient for Cr(VI) (198.70 mg/g at pH = 2.0, T = 298.15 K and C_Initial = 20.0 mg/L). 99.35% of Cr(VI) can be removed by the composites in 30 min. Thermodynamic and kinetic studies suggest the removal of Cr(VI) is through both adsorption and reduction. The performance of MoS₂@LDC can be further enhanced by hydrogen plasma treatments, which was attributed to the sulfur vacancies induced improvement in the reduction activity of MoS₂ layer. The results of this work can guide the rational design of high-performance nanocomposite for efficient remediation of heavy metals in aquatic environment.

Pd Nanocluster/Monolayer MoS2 Heterojunctions for Light-Induced Room-Temperature Hydrogen Sensing

Developing sensing approaches that can exploit visible light for the detection of low-concentration hydrogen at room temperatures has become increasingly important for the safe use of hydrogen in many applications. In this study, heterostructures composed of monolayer MoS₂ and Pd nanoclusters (Pd/MoS₂) acting as photo- and hydrogen-sensitizers are successfully fabricated in a facile and scalable manner. The uniform deposition of morphologically isotropic Pd nanoclusters (11.5 ± 2.2 nm) on monolayer MoS₂ produces a plethora of active heterojunctions, effectively suppressing charge carrier recombination under light illumination. The dual photo- and hydrogen-sensitizing functionality of Pd/MoS₂ can enable its use as an active sensing layer in optoelectronic hydrogen sensors. Gas-sensing examinations reveal that the sensing performance of Pd/MoS₂ is enhanced three-fold under visible light illumination (17% for 140 ppm of H₂) in comparison with dark light (5% for 140 ppm of H₂). Photoactivation is also found to enable excellent sensing reversibility and reproducibility in the obtained sensor. As a proof-of-concept, the integration of Pd nanoclusters and monolayer MoS₂ can open a new avenue for light-induced hydrogen gas sensing at room temperature.

Asymmetric 2D MoS2 for Scalable and High-Performance Piezoelectric Sensors

Piezoelectricity in two-dimensional (2D) transition-metal dichalcogenides (TMDs) has attracted significant attention due to their unique crystal structure and the lack of inversion centers when the bulk TMDs thin down to monolayers. Although the piezoelectric effect in atomic-thickness TMDs has been reported earlier, they are exfoliated 2D TMDs and are therefore not scalable. Here, we demonstrate a superior piezoelectric effect from large-scale sputtered, asymmetric 2D MoS₂ using meticulous defect engineering based on the thermal-solvent annealing of the MoS₂ layer. This yields an output peak current and voltage of 20 pA and 700 mV (after annealing at 450 °C), respectively, which is the highest piezoelectric strength ever reported in 2D MoS₂. Indeed, the piezoelectric strength increases with the defect density (sulfur vacancies), which, in turn, increases with the annealing temperature at least up to 450 °C. Moreover, our piezoelectric MoS₂ device array shows an exceptional piezoelectric sensitivity of 262 mV/kPa with a high level of uniformity and excellent performance under ambient conditions. A detailed study of the sulfur vacancy-dependent property and its resultant asymmetric structure-induced piezoelectricity is reported. The proposed approach is scalable and can produce advanced materials for flexible piezoelectric devices to be used in emerging bioinspired robotics and biomedical applications.

Molybdenum-containing polypyrrole self-supporting hollow flexible electrode for hydrogen peroxide detection in living cells

A flexible electrode based on polypyrrole-supported free-standing molybdenum oxide-molybdenum disulfide/polypyrrole nanostructure (MoO₃-MoS₂/PPy) was synthesized. The petal-like MoO₃-MoS₂ sheets grown on PPy were prepared step by step through simple electrodeposition and hydrothermal methods. The corresponding surface morphological and structural characterizations were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results showed that the prepared petal MoO₃-MoS₂ hybrid nanomaterials were uniformly distributed on the PPy skeleton and exhibited a three-dimensional porous network structure. The flexible electrode was used for non-enzymatic detection of hydrogen peroxide (H₂O₂), and the developed MoO₃-MoS₂/PPy nanomaterials exhibited high electrochemical sensing performance in the range of 0.3-150 μM, with the detection limit of 0.18 μM (S/N = 3). The excellent detection properties enabled the MoO₃-MoS₂/PPy flexible electrode to detect H₂O₂ released by living cells. The resulting MoO₃-MoS₂/PPy flexible electrode also has the advantages of customizable shape and adjustability, which provides a potential platform for constructing clinically diagnosed in vivo portable instruments and real-time environmental monitoring.

Novel magnetically retrievable In2O3/MoS2/Fe3O4 nanocomposite materials for enhanced photocatalytic performance

The current work involves synthesis of hybrid nanomaterial of In2O3/MoS2/Fe3O4 and their applications as photocatalysts for disintegration of esomeprazole under visible light illumination. The data emerged from various analyses testified to the successful construction of the desired nano-scaled hybrid photocatalyst. Tauc plot gave the band gap of In2O3/MoS2/Fe3O4 to be ~ 2.15 eV. Synergistic effects of the integrant components enabled efficacious photocatalytic performances of the nanocomposite. The nanohybrid photocatalyst In2O3/MoS2/Fe3O4 showed photodecomposition up to ~ 92.92% within 50 min. The current work realizes its objective of constructing metal oxide based hybrid nano-photocatalyst supported on MoS2 sheets for activity in the visible spectrum, which displayed remarkable capacity of disintegrating emerging persistent organic contaminants and are magnetically recoverable.

Te-S covalent bond induces 1T&2H MoS2 with improved potassium-ion storage performance

The modulation of the characteristics of an MoS2 anode via substitutional doping, particularly N, P and Se, is vital for promoting the potassium-ion storage performances. However, these traditional chalcogen doping can only take the place of a sulfur element and not essentially change the inherent electrical nature of MoS2. Herein, novel Te-MoS2 materials have been synthesized via a simple hydrothermal process under Te doping. A half-metallic Te occupies the position of an Mo atom to form Te-S bonds, which is different from the same group Se element. After theoretical modeling and electrochemical measurements, it was observed that the formation of Te-S bonds can increase the electrical conductivity (about 530 times increment) and mitigate the mechanical stress to ensure the whole structural stability during the repeated insertion/extraction of K-ions. Moreover, the insertion of Te into the lattice of MoS2 generated the fractional phase transformation from 2H to the 1T phase of MoS2 and 1T&2H in-plane hetero-junction. Benefiting from these advantages, the 1T&2H Te-MoS2 anode delivered high capacities of 718 and 342 mA h g-1 at 50 and 5000 mA g-1, respectively, and an ultra-stable cycling performance (88.1% capacity retention after 1000 cycles at 2 A g-1). Moreover, the potassium-ion full cell assembled with K2Fe[Fe(CN)6] as the cathode demonstrates its practical application.