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Electrochemical Exfoliation of MoS <sub/>2</sub> Crystal for Hydrogen Electrogeneration
摘要： Transition metal dichalcogenides (TMDs) have recently emerged within the group of 2D materials due to their electrical, catalytic and optical properties significantly enhanced and useful when down-sized to single layer. In particular, MoS2 has attracted much attention due to its semiconducting nature with a useful band gap when present as single layer, the enhanced photoluminescence, but also importantly the excellent catalytic properties towards the electrochemical hydrogen evolution. We present here the preparation of thin layers MoS2 nanosheets with enhanced catalytic properties towards the hydrogen evolution reaction by means of an easy and fast electrochemical top-down exfoliation procedure in aqueous solution from a naturally occurring MoS2 crystal. After structural and chemical characterization with STEM, AFM, XPS and Raman spectroscopy electrochemical investigations were performed to test catalytic properties in acidic solution for the electrogeneration of hydrogen and compare it to MoS2 nanosheets obtained through the widely employed chemical Li intercalation/exfoliation. Electrochemically exfoliated MoS2 shows lower Tafel slope than its counterpart obtained with chemical exfoliation.
关键词： hydrogen evolution reaction,molybdenum sulfide,electrochemistry,layered compound,exfoliation
更新于2025-09-23 15:21:01
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Liquid Phase Exfoliated Indium Selenide Based Highly Sensitive Photodetectors
摘要： Layered semiconductors of the IIIA–VIA group have attracted considerable attention in (opto)electronic applications thanks to their atomically thin structures and their thickness-dependent optical and electronic properties, which promise ultrafast response and high sensitivity. In particular, 2D indium selenide (InSe) has emerged as a promising candidate for the realization of thin-film field effect transistors and phototransistors due to its high intrinsic mobility (>102 cm2 V?1 s?1) and the direct optical transitions in an energy range suitable for visible and near-infrared light detection. A key requirement for the exploitation of large-scale (opto)electronic applications relies on the development of low-cost and industrially relevant 2D material production processes, such as liquid phase exfoliation, combined with the availability of high-throughput device fabrication methods. Here, a β polymorph of indium selenide (β-InSe) is exfoliated in isopropanol and spray-coated InSe-based photodetectors are demonstrated, exhibiting high responsivity to visible light (maximum value of 274 A W?1 under blue excitation 455 nm) and fast response time (15 ms). The devices show a gate-dependent conduction with an n-channel transistor behavior. Overall, this study establishes that liquid phase exfoliated β-InSe is a valid candidate for printed high-performance photodetectors, which is critical for the development of industrial-scale 2D material-based optoelectronic devices.
关键词： photodetectors,2D semiconductors,indium selenide,field effect transistors,liquid phase exfoliation,spray coating,solution processed
更新于2025-09-23 15:19:57
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Liquid phase exfoliation of MoS2 and WS2 in aqueous ammonia and their application in highly efficient organic solar cells
摘要： Simple, scalable and cost-effective synthesis of quality two-dimensional (2D) transition metal dichalcogenides (TMDs) is critical for fundamental investigations but also for the widespread adoption of these low-dimensional materials to an expanding range of device applications. Here, we report on the liquid-phase exfoliation (LPE) of molybdenum disulfide (MoS2) and tungsten disulfide (WS2) in aqueous ammonia (NH3 (aq)) as a greener alternative to commonly used but less environmentally friendly solvents. The synthesized nanosheets can be prepared in high concentrations (0.5-1 mg mL-1) and exhibit excellent stoichiometric and structural quality with a semiconducting character. These characteristics makes them ideal for application in organic optoelectronics, where optical transparency and suitable energetics are two important prerequisites. When MoS2 and WS2 are used as the sole hole transport layer materials in organic photovoltaics, cells with power conversion efficiency of 14.9 and 15.6%, respectively, are obtained highlighting the potential of the aqueous ammonia-based LPE method for the preparation of high quality TMDs. The method could potentially be extended to other TMDs.
关键词： aqueous ammonia,MoS2,liquid-phase exfoliation,organic solar cells,WS2
更新于2025-09-23 15:19:57
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A self-powered photodetector based on two-dimensional boron nanosheets
摘要： Owing to their intriguing characteristics, the ongoing pursuit of emerging mono-elemental two-dimensional (2D) nanosheets beyond graphene is an exciting research area for next-generation applications. Herein, we demonstrate that highly crystalline 2D boron (B) nanosheets can be efficiently synthesized by employing a modified liquid phase exfoliation method. Moreover, carrier dynamics has been systematically investigated by using femtosecond time-resolved transient absorption spectroscopy, demonstrating an ultrafast recovery speed during carrier transfer. Based on these results, the optoelectronic performance of the as-synthesized 2D B nanosheets has been investigated by applying them in photoelectrochemical (PEC)-type and field effect transistor (FET)-type photodetectors. The experimental results revealed that the as-fabricated PEC device not only exhibited a favourable self-powered capability, but also a high photoresponsivity of 2.9–91.7 μA W?1 in the UV region. Besides, the FET device also exhibited a tunable photoresponsivity in the range of 174–281.3 μA W?1 under the irradiation of excited light at 405 nm. We strongly believe that the current work shall pave the path for successful utilization of 2D B nanosheets in electronic and optoelectronic devices. Moreover, the proposed method can be utilized to explore other mono-elemental 2D nanomaterials.
关键词： two-dimensional boron nanosheets,optoelectronic devices,carrier dynamics,liquid phase exfoliation,photodetector
更新于2025-09-23 15:19:57
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Facile and controllable synthesis of Zn-Al layered double hydroxide/silver hybrid by exfoliation process and its plasmonic photocatalytic activity of phenol degradation
摘要： Photocatalysts have attracted interest in the applications of green technology due to its efficiency to eliminate detrimental substances under light irradiation. Various design strategies to enhance the efficiency of photocatalytic processes under solar irradiation is actively searched. Building on the idea to provide a better synthesis method of photocatalyst, this study explores an effective and simple synthesis strategy of Layered Double Hydroxide (LDH) silver hybrid for photocatalyst phenol degradation. Unlike the common photodeposition method that incorporates noble metal nanoparticle on the LDH surface, this study discovered a pathway of intercalation of Ag nanoparticle into LDH interlayer space by exfoliation route. Notably, the synthesized ZnAl LDH/Ag contents of several phases: Zn2.5Al(OH)6.5O0.5(DS)0.5Ag0.3, Zn2.5Al(OH)7(HDS)0.5(DS)1.5, Zn2.5Al (OH)6.32O0.68(CO3)0.16Ag0.03, Zn2Al(OH)5.32O0.68 (CO3)0.16. A preliminary demonstration of the concept was given by the efficient photocatalytic degradation of phenol with a resulting conversion ratio of phenol under light (Xe lamp, > 340-nm cut-off filter) irradiation by 80 % in 210 min. These findings provide a new strategy to incorporate noble metal nanoparticles into LDH interlayer space as a great potential for photocatalyst.
关键词： Silver nanoparticle,Photocatalyst,Surface plasmon resonance,Layered double hydroxide,Exfoliation
更新于2025-09-23 15:19:57
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Adhesion Behavior between Multilayer Graphene and Semiconductor Substrates
摘要： A high bonding strength between graphene and a semiconductor surface is significant to the performance of graphene-based Micro-Electro Mechanical Systems/Nano-Electro Mechanical Systems (MEMS/NEMS) devices. In this paper, by applying a series of constant vertical upward velocities (Vup) to the topmost layer of graphene, the exfoliation processes of multilayer graphene (one to ten layers) from an Si semiconductor substrate were simulated using the molecular dynamics method, and the bonding strength was calculated. The critical exfoliation velocities, adhesion forces, and adhesion energies to exfoliate graphene were obtained. In a system where the number of graphene layers is two or three, there are two critical exfoliation velocities. Graphene cannot be exfoliated when the Vup is lower than the first critical velocity, although the total number of graphene layers can be exfoliated when the Vup is in the range between the first critical velocity and second critical velocity. Only the topmost layer can be exfoliated to be free from the Si surface if the applied Vup is greater than the second critical velocity. In systems where the number of graphene layers is four to ten, only the topmost layer can be free and exfoliated if the exfoliation velocity is greater than the critical velocity. It was found that a relatively low applied Vup resulted in entire graphene layers peeling off from the substrate. The adhesion forces of one-layer to ten-layer graphene systems were in the range of 25.04 nN–74.75 nN, and the adhesion energy levels were in the range of 73.5 mJ/m2–188.45 mJ/m2. These values are consistent with previous experimental results, indicating a reliable bond strength between graphene and Si semiconductor surfaces.
关键词： adhesion force,bonding mechanism,adhesion energy,exfoliation behavior,MEMS/NEMS,molecular dynamics,graphene
更新于2025-09-23 15:19:57
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A Comparative Study of Particle Size Distribution of Graphene Nanosheets Synthesized by an Ultrasound-Assisted Method
摘要： Graphene-based materials are highly interesting in virtue of their excellent chemical, physical and mechanical properties that make them extremely useful as privileged materials in different industrial applications. Sonochemical methods allow the production of low-defect graphene materials, which are preferred for certain uses. Graphene nanosheets (GNS) have been prepared by exfoliation of a commercial micrographite (MG) using an ultrasound probe. Both materials were characterized by common techniques such as X-ray diffraction (XRD), Transmission Electronic Microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). All of them revealed the formation of exfoliated graphene nanosheets with similar surface characteristics to the pristine graphite but with a decreased crystallite size and number of layers. An exhaustive study of the particle size distribution was carried out by different analytical techniques such as dynamic light scattering (DLS), nanoparticle tracking analysis (NTA) and asymmetric flow field flow fractionation (AF4). The results provided by these techniques have been compared. NTA and AF4 gave higher resolution than DLS. AF4 has shown to be a precise analytical technique for the separation of GNS of different sizes.
关键词： exfoliation,graphene nanosheets,nanoparticle tracking analysis,asymmetric flow field flow fractionation,particle size distribution
更新于2025-09-19 17:15:36
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17% Efficient Organic Solar Cells Based on Liquid Exfoliated WS <sub/>2</sub> as a Replacement for PEDOT:PSS
摘要： The application of liquid-exfoliated 2D transition metal disulfides (TMDs) as the hole transport layers (HTLs) in nonfullerene-based organic solar cells is reported. It is shown that solution processing of few-layer WS2 or MoS2 suspensions directly onto transparent indium tin oxide (ITO) electrodes changes their work function without the need for any further treatment. HTLs comprising WS2 are found to exhibit higher uniformity on ITO than those of MoS2 and consistently yield solar cells with superior power conversion efficiency (PCE), improved fill factor (FF), enhanced short-circuit current (JSC), and lower series resistance than devices based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and MoS2. Cells based on the ternary bulk-heterojunction PBDB-T-2F:Y6:PC71BM with WS2 as the HTL exhibit the highest PCE of 17%, with an FF of 78%, open-circuit voltage of 0.84 V, and a JSC of 26 mA cm?2. Analysis of the cells’ optical and carrier recombination characteristics indicates that the enhanced performance is most likely attributed to a combination of favorable photonic structure and reduced bimolecular recombination losses in WS2-based cells. The achieved PCE is the highest reported to date for organic solar cells comprised of 2D charge transport interlayers and highlights the potential of TMDs as inexpensive HTLs for high-efficiency organic photovoltaics.
关键词： liquid exfoliation,2D transition metal disulfides,nonfullerene organic solar cells,hole transport layers,MoS2,WS2
更新于2025-09-19 17:13:59
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One‐Pot Exfoliation of Graphitic C <sub/>3</sub> N <sub/>4</sub> Quantum Dots for Blue QLEDs by Methylamine Intercalation
摘要： Here, a simplified synthesis of graphitic carbon nitride quantum dots (g-C3N4-QDs) with improved solution and electroluminescent properties using a one-pot methylamine intercalation–stripping method (OMIM) to hydrothermally exfoliate QDs from bulk graphitic carbon nitride (g-C3N4) is presented. The quantum dots synthesized by this method retain the blue photoluminescence with extremely high fluorescent quantum yield (47.0%). As compared to previously reported quantum dots, the g-C3N4-QDs synthesized herein have lower polydispersity and improved solution stability due to high absolute zeta-potential (?41.23 mV), which combine to create a much more tractable material for solution processed thin film fabrication. Spin coating of these QDs yields uniform films with full coverage and low surface roughness ideal for quantum dot light-emitting diode (QLED) fabrication. When incorporated into a functional QLED with OMIM g-C3N4-QDs as the emitting layer, the LED demonstrates ≈60× higher luminance (605 vs 11 Cd m?2) at lower operating voltage (9 vs 21 V), as compared to the previously reported first generation g-C3N4 QLEDs, though further work is needed to improve device stability.
关键词： graphitic carbon nitride,quantum dot light-emitting diodes,metal-free semiconductors,hydrothermal exfoliation
更新于2025-09-19 17:13:59
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Molybdenum Disulfide Nanosheet/Quantum Dot Dynamic Memristive Structure Driven by Photoinduced Phase Transition
摘要： MoS2 2D nanosheets (NS) with intercalated 0D quantum dots (QDs) represent promising structures for creating low-dimensional (LD) resistive memory devices. Nonvolatile memristors based 2D materials demonstrate low power consumption and ultrahigh density. Here, the observation of a photoinduced phase transition in the 2D NS/0D QDs MoS2 structure providing dynamic resistive memory is reported. The resistive switching of the MoS2 NS/QD structure is observed in an electric field and can be controlled through local QD excitations. Photoexcitation of the LD structure at different laser power densities leads to a reversible MoS2 2H-1T phase transition and demonstrates the potential of the LD structure for implementing a new dynamic ultrafast photoresistive memory. The dynamic LD photomemristive structure is attractive for real-time pattern recognition and photoconfiguration of artificial neural networks in a wide spectral range of sensitivity provided by QDs.
关键词： neuromorphic computing,photoinduced phase transition,2D crystals and QDs,dynamic photomemristors,liquid phase exfoliation
更新于2025-09-19 17:13:59