Search Results (66)

Two-dimensional (2D) material-based resistive random-access memory (RRAM) has emerged as a promising solution for neuromorphic computing and computing-in-memory architectures. Compared to conventional metal-oxide-based RRAM, the novel 2D material-based RRAM devices demonstrate lower power consumption, higher integration density, and reduced performance variability, benefiting from their atomic-scale thickness and ultra-flat surfaces. Remarkably, 2D layered metal oxides retain these advantages while preserving the merits of traditional metal oxides, including their low cost and high environmental stability. Through a multi-step dry transfer process, we fabricated a Pd-MoO₃-Ag RRAM device featuring 2D α-MoO₃ as the resistive switching layer, with Pd and Ag serving as inert and active electrodes, respectively. Resistive switching tests revealed an excellent operational stability, low write voltage (~0.5 V), high switching ratio (>10⁶), and multi-bit storage capability (≥3 bits). Nevertheless, the device exhibited a limited retention time (~2000 s). To overcome this limitation, we developed a Gr-MoO₃-Ag heterostructure by substituting the Pd electrode with graphene (Gr). This modification achieved a fivefold improvement in the retention time (>10⁴ s). These findings demonstrate that by controlling the type and thickness of 2D materials and resistive switching layers, RRAM devices with both high On/Off ratios and long-term data retention may be developed. Full article

Two-dimensional (2D) n-MoS₂ nanosheets (NSs) synthesized via the sol–gel method were deposited onto p-type heavily boron-doped diamond (BDD) film to form a n-MoS₂/p-degenerated BDD (DBDD) heterojunction device. The PL emission results for the heterojunction suggest strong potential for applications using yellow-light-emitting optoelectronic devices. From room temperature (RT) to 180 °C, the heterojunction exhibits typical rectification characteristics with good results for thermal stability, rectification ratio, forward current decrease, and reverse current increase. Compared with the n-MoS₂/p-lightly B-doped (non-degenerate) diamond heterojunction, the heterojunction demonstrates a significant improvement in both its rectification ratio and ideal factor. At 100 °C, the rectification ratio reaches the maximum value and is considered an ideal high temperature for achieving optimal heterojunction performance. When the temperature exceeds 140 °C, the heterojunction transforms into the Zener diode. The heterojunction’s electrical temperature dependence is due to the Fermi level shifting resulting in the weakening of the carrier interband tunneling injection. The n-MoS₂ NSs/p-DBDD heterojunction will broaden future research application prospects in the field of high-temperature consumption in future optoelectronic devices. Full article

Constructing an S-type heterojunction to promote photogenerated carrier separation is a valid method to ameliorate this problem. In this work, self-assembled perylenetetracarboxylic diimide (PDI) was modified on the surface of two-dimensional (2D) BiOBr nanosheets using a continuous ion layer adsorption method. To explore its microstructure, photoelectric properties, and other characteristics, the electron transport channel constructed between self-assembled PDI and BiOBr hinders photogenerated electron-hole recombination. Under visible light irradiation, when the rhodamine B (RhB) was 50 mg/L, the removal rate over 1/3 PDI/BiOBr reached 98% in 60 min, and the rate constant was 15.9 times that over self-assembled PDI and 13 times that over BiOBr. In degrading methyl orange (MO), the removal rate over 1/3 PDI/BiOBr was 65.8% in 60 min, and the rate constant was 5.7 times that over self-assembled PDI and 3.4 times over BiOBr. After the ESR test, O₂⁻ is proved to be the main active species in the reaction. Full article

Chemical warfare agents (CWAs) are known as poor man’s bombs because of their small lethal dose, cheapness, and ease of production. Therefore, the highly sensitive and rapid detection of CWAs at room temperature (RT = 25 °C) is essential. In this paper, we have developed a resistive semiconductor sensor for the highly sensitive detection of CWAs at RT. The gas-sensing material is SnS₂/rGO nanosheets (NSs) prepared by hydrothermal synthesis. The lower detection limits of the SnS₂/rGO NSs-based gas sensor were 0.05 mg/m³ and 0.1 mg/m³ for the typical chemical weapons sarin (GB) and sulfur mustard (HD), respectively. The responsivity can reach −3.54% and −10.2% in 95 s for 1.0 mg/m³ GB, and in 47 s for 1.0 mg/m³ HD. They are 1.17 and 2.71 times higher than the previously reported Nb-MoS₂ NSs-based gas sensors, respectively. In addition, it has better repeatability (RSD = 6.77%) and stability for up to 10 weeks (RSD = 20.99%). Furthermore, to simplify the work of later researchers based on the detection of CWAs by two-dimensional transition metal sulfur compounds (2D-TMDCs), we carried out calculations of the SnS₂ NSs-based and SnS₂/rGO NSs-based gas sensor-adsorbing CWAs. Detailed comparisons are made in conjunction with experimental results. For different materials, it was found that the SnS₂/rGO NSs-based gas sensor performed better in all aspects of adsorbing CWAs in the experimental results. Adsorbed CWAs at a distance smaller than that of the SnS₂ NSs-based gas sensor in the theoretical calculations, as well as its adsorption energy and transferred charge, were larger than those of the SnS₂ NSs-based gas sensor. For different CWAs, the experimental results show that the sensitivity of the SnS₂/rGO NSs-based gas sensor for the adsorption of GB is higher than that of HD, and accordingly, the theoretical calculations show that the adsorption distance of the SnS₂/rGO NSs-based gas sensor for the adsorption of GB is smaller than that of HD, and the adsorption energy and the amount of transferred charge are larger than that of HD. This regularity conclusion proves the feasibility of adsorption of CWAs by gas sensors based on SnS₂ NSs, as well as the feasibility and reliability of theoretical prediction experiments. This work lays a good theoretical foundation for subsequent rapid screenings of gas sensors with gas-sensitive materials for detecting CWAs. Full article

The photocatalytic conversion of ethanol and the simultaneous development of hydrogen technology play a role in solving the energy crisis and reducing environmental pollution. In this research, rod-like M-MoS₂ serves as a channel for charge transfer, leading to superior photocatalytic activity compared to H-MoS₂. Further, two-dimensional (2D) B-doped C₃N₄ (BCN) nanosheets were anchored on the one-dimensional (1D) rod-like M-MoS₂ surface to form a 1D/2D heterojunction, with M-MoS₂/BCN-0.08 (mass ratio of M-MoS₂:BCN of 0.08:1) exhibiting the highest photocatalytic performance. Under visible light irradiation, the ethanol conversion rate reached 1.79% after 5 h of photocatalytic reaction per gram of catalyst, while generating 421 μmol of 2,3-butanediol (2,3-BDO), 5460 μmol of acetaldehyde (AA), and 5410 μmol of hydrogen gas (H₂). This different characterization provides evidence that a significant amount of photoinduced electrons generated in BCN under illumination conditions rapidly transfer to the conduction band (CB) of M-MoS₂ through the rod-like structure of M-MoS₂, and finally transfer to Pt to promote the production of hydrogen gas. The photoinduced holes in the valence band (VB) of M-MoS₂ are rapidly consumed by ethanol upon transferring to BCN, effectively separating the photoinduced electron–hole pairs and resulting in superior photocatalytic performance. Full article

This article successfully synthesized a series of Bi₂MoO₆/Bi₄O₅Br₂ heterojunctions using a two-step solvothermal method followed by calcination, and the photocatalytic activity by degradation of tetracycline hydrochloride (TC) was investigated. Compared with pure Bi₄O₅Br₂ and Bi₂MoO₆, a series of Bi₂MoO₆/Bi₄O₅Br₂ heterojunctions exhibit higher photocatalytic activity, which can be attributed to the heterostructures with strong interfacial interaction, improving the charge separation. The 2% Bi₂MoO₆/Bi₄O₅Br₂ heterojunction shows the best photocatalytic activity under visible light irradiation, which is 1.9 times and 1.8 times that of Bi₂MoO₆ and Bi₄O₅Br₂, respectively. In addition, cyclic experiments have shown that 2% Bi₂MoO₆/Bi₄O₅Br₂ heterojunction has high stability, with a degradation efficiency only decreasing by 3% after 5 cycles. From the capture agent experiment and ESR test, it can be seen that ·O₂⁻ and h⁺ are the main active species. A possible photocatalytic mechanism of 2% Bi₂MoO₆/Bi₄O₅Br₂ heterojunction under visible light irradiation was proposed. Full article

Supercapacitors have gained increased attention in recent years due to their significant role in energy storage devices; their impact largely depends on the electrode material. The diversity of energy storage mechanisms means that various electrode materials can provide unique benefits for specific applications, highlighting the growing trend towards nanocomposite electrodes. Typically, these nanocomposite electrodes combine pseudocapacitive materials with carbon-based materials to form heterogeneous structural composites, often requiring complex multi-step preparation processes. This study introduces a straightforward approach to fabricate a non-carbon-based Mo@MoO₂ nanosheet composite electrode using a one-step thermal evaporating vapor deposition (TEVD) method. This novel electrode features Mo at the core and MoO₂ as the shell and demonstrates exceptional electrochemical performance. Specifically, at a current density of 1 A g⁻¹, it achieves a storage capacity of 205.1 F g⁻¹, maintaining virtually unchanged capacity after 10,000 charge–discharge cycles at 2 A g⁻¹. The outstanding long-cycle stability is ascribed to the vertical two-dimensional geometry, the superior conductivity, and pseudocapacitance of the Mo@MoO₂ core-shell nanosheets. These attributes significantly improve the electrode’s charge storage capacity, charge transfer speed, and structural integrity during the cycling process. The development of the one-step grown Mo@MoO₂ nanosheets offers a promising way for the advancement of high-performance, non-carbon-based supercapacitor nanocomposite electrodes. Full article

Recently, a smart strategy for two-dimensional (2D) materials synthesis has emerged, namely space-confined chemical vapor deposition (CVD). Its extreme case is the microreactor method, in which the growth substrate is face-to-face stacked on the source substrate. In order to grow 2D transition metal dichalcogenides by this method, transition metal oxides, dispersed in very small amounts on the source substrate, are used as source materials in most of the published reports. In this paper, a colloidal dispersion of MoS₂ in saline solution is used and MoS₂ nanosheets with various shapes, sizes (between 5 and 60 μm) and thicknesses (2–4 layers) have been synthesized. Small MoS₂ flakes (regular or defective) are present on the surface of the nanosheets. Catalytic sites, undercoordinated atoms located at the edges of MoS₂ flakes and nanosheets, are produced in a high number by a layer-plus-island (Stranski–Krastanov) growth mechanism. Several double-resonance Raman bands (at 147, 177, 187, 225, 247, 375 cm⁻¹) are assignable to single phonon processes in which the excited electron is elastically scattered on a defect. The narrow 247 cm⁻¹ peak is identified as a topological defect-activated peak. These findings highlight the potential of defect engineering in material property optimization, particularly for solar water splitting applications. Full article

The low light absorption efficiency has seriously hindered the application of two-dimensional transition metal dichalcogenide (TMDC) nanosheets in the field of optoelectronic devices. Various approaches have been used to improve the performance of TMDC nanosheets. Preparation of one-dimensional TMDC nanoscrolls in combination with photoactive materials has been a promising method to improve their properties recently. In this work, we report a facile method to enhance the optoelectronic performance of TMDC nanoscrolls by wrapping the photoactive organic dye rhodamine (R6G) into them. After R6G molecules were deposited on monolayer TMDC nanosheets by the solution method, the R6G/MoS₂ nanoscrolls with lengths up to hundreds of microns were prepared in a short time by dropping a mixture of ammonia and ethanol solution on the R6G/MoS₂ nanosheets. The as-obtained R6G/MoS₂ nanoscrolls were well characterized by optical microscopy, atomic force microscopy, Raman spectroscopy, and transmission electron microscopy to prove the encapsulation of R6G. There are multiple type II heterojunction interfaces in the R6G/MoS₂ nanoscrolls, which can promote the generation of photo-induced carriers and the following electron–hole separation. The separated electrons were transported rapidly along the axial direction of the R6G/MoS₂ nanoscrolls, which greatly improves the efficiency of light absorption and photoresponse. Under the irradiation of an incident 405 nm laser, the photoresponsivity, carrier mobility, external quantum efficiency, and detectivity of R6G/MoS₂ nanoscrolls were enhanced to 66.07 A/W, 132.93 cm²V⁻¹s⁻¹, 20,261%, and 1.25 × 10¹² cm·Hz^1/2W⁻¹, which are four orders of magnitude higher than those of monolayer MoS₂ nanosheets. Our work indicates that the R6G/TMDC hybrid nanoscrolls could be promising materials for high-performance optoelectronic devices. Full article

The preparation of 2H-phase MoS₂ thin nanosheets by electrochemical delamination remains a challenge, despite numerous efforts in this direction. In this work, by choosing appropriate intercalating cations for cathodic delamination, the insertion process was facilitated, leading to a higher degree of exfoliation while maintaining the original 2H-phase of the starting bulk MoS₂ material. Specifically, trimethylalkylammonium cations were tested as electrolytes, outperforming their bulkier tetraalkylammonium counterparts, which have been the focus of past studies. The performance of novel electrochemically derived 2H-phase MoS₂ nanosheets as electrode material for electrochemical energy storage in lithium-ion batteries was investigated. The lower thickness and thus higher flexibility of cathodically exfoliated MoS₂ promoted better electrochemical performance compared to liquid-phase and ultrasonically assisted exfoliated MoS₂, both in terms of capacity (447 vs. 371 mA·h·g⁻¹ at 0.2 A·g⁻¹) and rate capability (30% vs. 8% capacity retained when the current density was increased from 0.2 A·g⁻¹ to 5 A·g⁻¹), as well as cycle life (44% vs. 17% capacity retention at 0.2 A·g⁻¹ after 580 cycles). Overall, the present work provides a convenient route for obtaining MoS₂ thin nanosheets for their advantageous use as anode material for lithium storage. Full article

The combination of two-dimensional material MXene and one-dimensional metal oxide semiconductor can improve the carrier transmission rate, which can effectively improve sensing performance. We prepared a trimethylamine gas sensor based on MoO₃ nanofibers and layered Ti₃C₂T_x MXene. Using electrospinning and chemical etching methods, one-dimensional MoO₃ nanofibers and two-dimensional Ti₃C₂T_x MXene nanosheets were prepared, respectively, and the composites were characterized via XPS, SEM, and TEM. The Ti₃C₂T_x MXene–MoO₃ composite material exhibits excellent room-temperature response characteristics to trimethylamine gas, showing high response (up to four for 2 ppm trimethylamine gas) and rapid response–recovery time (10 s/7 s). Further, we have studied the possible sensitivity mechanism of the sensor. The Ti₃C₂T_x MXene–MoO₃ composite material has a larger specific surface area and more abundant active sites, combined with p–n heterojunction, which effectively improves the sensitivity of the sensor. Because of its low detection limit and high stability, it has the potential to be applied in the detection system of trimethylamine as a biomarker in exhaled air. Full article

In this review, we examine recent progress using boron nitride (BN) and molybdenum disulfide (MoS₂) nanostructures for electronic, energy, biomedical, and environmental applications. The scope of coverage includes zero-, one-, and two-dimensional nanostructures such as BN nanosheets, BN nanotubes, BN quantum dots, MoS₂ nanosheets, and MoS₂ quantum dots. These materials have sizable bandgaps, differentiating them from other metallic nanostructures or small-bandgap materials. We observed two interesting trends: (1) an increase in applications that use heterogeneous materials by combining BN and MoS₂ nanostructures with other nanomaterials, and (2) strong research interest in environmental applications. Last, we encourage researchers to study how to remove nanomaterials from air, soil, and water contaminated with nanomaterials. As nanotechnology proceeds into various applications, environmental contamination is inevitable and must be addressed. Otherwise, nanomaterials will go into our food chain much like microplastics. Full article

Polyimide (PI) has been widely used in cable insulation, thermal insulation, wind power protection, and other fields due to its high chemical stability and excellent electrical insulation and mechanical properties. In this research, a modified PI composite film (MoS₂@PDA/PI) was obtained by using polydopamine (PDA)-coated molybdenum disulfide (MoS₂) as a filler. The low interlayer friction characteristics and high elastic modulus of MoS₂ provide a theoretical basis for enhancing the flexible mechanical properties of the PI matrix. The formation of a cross-linking structure between a large number of active sites on the surface of the PDA and the PI molecular chain can effectively enhance the breakdown field strength of the film. Consequently, the tensile strength of the final sample MoS₂@PDA/PI film increased by 44.7% in comparison with pure PI film, and the breakdown voltage strength reached 1.23 times that of the original film. It can be seen that the strategy of utilizing two-dimensional (2D) MoS₂@PDA nanosheets filled with PI provides a new modification idea to enhance the mechanical and electrical insulation properties of PI films. Full article

As one of the key features of two-dimensional (2D) layered materials, stacking order has been found to play an important role in modulating the interlayer interactions of 2D materials, potentially affecting their electronic and other properties as a consequence. In this work, ultralow-frequency (ULF) Raman spectroscopy, electrostatic force microscopy (EFM), and high-resolution atomic force microscopy (HR-AFM) were used to systematically study the effect of stacking order on the interlayer interactions as well as electrostatic screening of few-layer polymorphic molybdenum disulfide (MoS₂) and molybdenum diselenide (MoSe₂) nanosheets. The stacking order difference was first confirmed by measuring the ULF Raman spectrum of the nanosheets with polymorphic stacking domains. The atomic lattice arrangement revealed using HR-AFM also clearly showed a stacking order difference. In addition, EFM phase imaging clearly presented the distribution of the stacking domains in the mechanically exfoliated nanosheets, which could have arisen from electrostatic screening. The results indicate that EFM in combination with ULF Raman spectroscopy could be a simple, fast, and high-resolution method for probing the distribution of polymorphic stacking domains in 2D transition metal dichalcogenide materials. Our work might be promising for correlating the interlayer interactions of TMDC nanosheets with stacking order, a topic of great interest with regard to modulating their optoelectronic properties. Full article

Graphene and graphene-like two-dimensional layered nanomaterials-based photoelectrochemical (PEC) biosensors have recently grown rapidly in popularity thanks to their advantages of high sensitivity and low background signal, which have attracted tremendous attention in ultrahigh sensitive small molecule detection. This work proposes a non-enzymatic and visible-light-sensitive PEC biosensing platform based on ZIF-67@MoS₂/rGO composite which is synthesized through a facile and one-step microwave-assisted hydrothermal method. The combination of MoS₂ and rGO could construct van der Waals heterostructures, which not only act as visible-light-active nanomaterials, but facilitate charge carriers transfer between the photoelectrode and glassy carbon electrode (GCE). ZIF-67 anchored on MoS₂/rGO heterostructures provides large specific surface areas and a high proportion of catalytic sites, which cooperate with MoS₂ nanosheets, realizing rapid and efficient enzyme-free electrocatalytic oxidation of glucose. The ZIF-67@MoS₂/rGO-modified GCE can realize the rapid and sensitive detection of glucose at low detection voltage, which exhibits a high sensitivity of 12.62 μAmM⁻¹cm⁻². Finally, the ZIF-67@MoS₂/rGO PEC biosensor is developed by integrating the ZIF-67@MoS₂/rGO with a screen-printed electrode (SPE), which exhibits a high sensitivity of 3.479 μAmM⁻¹cm⁻² and a low detection limit of 1.39 μM. The biosensor’s selectivity, stability, and repeatability are systematically investigated, and its practicability is evaluated by detecting clinical serum samples. Full article