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Functionalized and oxidized silicon nanosheets: Customized design for enhanced sensitivity towards relative humidity
摘要： The use of completely oxidized two-dimensional (2D) silicon nanosheets (SiNSs) represents a novel approach for the application of 2D silicon-based materials in the nanoelectronics field. Densely stacked and highly porous oxidized SiNSs (OSiNSs) act as a sensitive layer for humidity detection. Due to the oxidation-caused porosity of the SiNSs and the possibility functionalize the 2D surface with hydrophilic groups, this hybrid material exhibits an extremely good sensitivity towards relative humidity (RH). In this work, precise tuning of the SiNSs’ sensing properties by their functionalization is demonstrated. In particular, the modification with methacrylic acid (MAA) groups, leading to SiNS-MAA, and the subsequent deposition on interdigitated electrodes double the capacitance value in the range of 20-85%RH. These values were achieved after the full oxidation of SiNS-MAA in ambient conditions. The mentioned changes in capacitance are extremely high compared to the response of the so far known common polymer humidity sensors. Contrary to that, this response is neutralized when the SiNSs are functionalized with tert-butyl acrylic acid (tBMA), a rather hydrophobic functional group. The fabricated devices show, how the specific functionalization of SiNSs serves as a reliable tool to provide sensitivity towards RH. Similar approach, based on tuning the functionality, can be applied to achieve e.g., sensor array selectivity. For this purpose, the functional groups on the surface of the nanomaterial can be further modified. Additional molecules with sensitivities towards various surrounding conditions could be attached. Furthermore, these functional molecules can be used for subsequent (bio)molecule immobilization, which can serve as sensitive molecular groups towards surrounding substrates and gases. However, one of the main challenges in sensor technology is to find a highly selective solution: a sensor system capable to differentiate among different vapor species. The described strategy can serve as an access towards new and promising solutions, which can help to face this issue in modern nanomaterials-based technology.
关键词： two-dimensional materials,porous silicon,functionalization,silicon nanosheets,hybrid systems,moisture content
更新于2025-11-21 11:20:48
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Valley and spin splitting in monolayer TX2/antiferromagnetic MnO (T=Mo, W; X=S, Se) van der Waals heterostructures
摘要： The electronic structure of monolayer MoS2, WS2, MoSe2 and WSe2 on top of antiferromagnetic MnO(111) is investigated systematically by first-principles calculations. It is found that the time-reversal symmetry is broken by the stacking on MnO that leads to the valley polarization. The valley splitting of MoS2/MnO, WS2/MnO, MoSe2/MnO and WSe2/MnO is 161, 193, 171 and 125 meV for K point, and 18 to 253 meV for K' point. The pattern of stacking also induces p- or n-type doping of MoS2, revealing that the conductivity of the heterostructues could be tuned by stacking on MnO. Besides, we also calculate electronic structures of WS2/MnO, MoSe2/MnO and WSe2/MnO heterostructures in the configuration of Mn-terminated (III), and find the spin splitting at K point is 553, 324 and 481 meV, and 215, 9 and 284 meV for K' point, respectively. Furthermore, the termination of MnO substrate can switch the spin splitting of monolayer MoS2, WS2, MoSe2 and WSe2. The spin splitting of MoS2/MnO for six possible interface configurations is varied from 24 to 291 meV for K point, and 18 to 253 meV for K' point. The results present a new type of novel heterostructure that has potential applications in the spintronic and valleytronic devices.
关键词： Two dimensional materials,Heterostructure,Transition metal dichalcogenides,First-principles calculations
更新于2025-09-23 15:23:52
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Analysis and Modeling of White Graphene Physical Properties for Sensor Applications
摘要： White graphene as a two-dimensional material has honeycomb lattice which is comprised of boron and nitrogen atoms. Its mechanical properties are similar to graphene, but its electrical properties are different because it has a large bandgap about 5.5 eV. Moreover, relaxation time plays a key role in its properties that affects on the electron transfer speed in this material. The white graphene is an insulator, but its dielectric polarization does not depend on the electric ?eld and also any external stress cannot change linear response of relaxation. In this research, some physical properties of white graphene and its relaxation time are investigated and modeled. Finally, acceptable results are reported which bring new hopes for the replacement of silicon oxide with white graphene as a one-monolayer insulator in future sensors applications.
关键词： Honeycomb lattice,Graphene,Bandgap,Two-dimensional materials,White graphene
更新于2025-09-23 15:23:52
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Resonance Coupling in Heterostructures Composed of Silicon Nanosphere and Monolayer WS <sub/>2</sub> : A Magnetic-Dipole-Mediated Energy Transfer Process
摘要： Light?matter resonance coupling is a long-studied topic for both fundamental research and photonic and optoelectronic applications. Here we investigated the resonance coupling between the magnetic dipole mode of a dielectric nanosphere and 2D excitons in a monolayer semiconductor. By coating an individual silicon nanosphere with a monolayer of WS2, we theoretically demonstrated that, because of the strong energy transfer between the magnetic dipole mode of the nanosphere and the A-exciton in WS2, resonance coupling evidenced by anticrossing behavior in the scattering energy diagram was observed, with a mode splitting of 43 meV. In contrast to plexcitons, which involve plasmonic nanocavities, the resonance coupling in this all-dielectric heterostructure was insensitive to the spacing between the silicon nanosphere core and the WS2 shell. Additionally, the two split modes exhibited distinct light-scattering directionality. We further experimentally demonstrated the resonance coupling effect by depositing silicon nanospheres with different diameters onto a WS2 monolayer and collecting the scattering spectra of the resulting heterostructures under ambient conditions. We further demonstrated active control of the resonance coupling by temperature scanning. Our findings highlighted the potential of our all-dielectric heterostructure as a solid platform for studying strong light?matter interactions at the nanoscale.
关键词： magnetic dipole modes,two-dimensional materials,resonance coupling,two-dimension excitons,silicon nanospheres
更新于2025-09-23 15:23:52
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Highly Sensitive Polarization Photodetection Using a Pseudo-One-Dimensional Nb <sub/> (1– <i>x</i> ) </sub> Ti <sub/><i>x</i> </sub> S <sub/>3</sub> Alloy
摘要： Low-symmetry layered two-dimensional (2D) materials with strong in-plane optical anisotropy can potentially be applied for polarization photodetection. This is especially true for those 2D materials with a direct bandgap, who can efficiently absorb light with specific axial polarization. However, discovering such new anisotropic 2D materials with direct band structure is still extremely challenging. Here, we fabricate a photodetector using a pseudo-one-dimensional (pseudo-1D) Nb(1-x)TixS3 alloy device, and demonstrate that it is highly sensitive to the polarized light due to the strong in-plane optical anisotropy and direct bandgap of the alloy by combining the angle-resolved polarization Raman spectroscopy (ARPRS), azimuth-dependent reflectance difference microscopy (ADRDM), polarization-dependent absorption spectroscopy (PDAS), and hybrid functional theory calculations. As a consequence, the polarization photodetector of the Nb(1-x)TixS3 alloy shows a large photocurrent anisotropic ratio and a high photoresponse. The choice of low-symmetry layered pseudo-1D Nb(1-x)TixS3 alloy in polarization photodetection might open up new functionalities for novel optoelectronic device applications.
关键词： low-symmetry structure,in-plane optical anisotropy,pseudo-one-dimensional materials,Nb(1-x)TixS3 ternary alloy,polarization-sensitive photodetector
更新于2025-09-23 15:23:52
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From pentagonal geometries to two-dimensional materials
摘要： Hexagons are dominating building blocks in the atomic structures of existing and predicted two-dimensional (2D) materials. A wealth of properties possessed by numerous 2D materials are attributed to their hexagonal, structural units. Although many review articles exist for 2D hexagonal materials, this review focus on a less common building block, pentagon, of 2D materials. We start with introducing 15 types of convex pentagons that can tile an infinite plane without creating a gap. We connect one of these pentagonal geometries (type 2 pentagon) with 2D materials via density functional theory (DFT) calculations, resulting in predictions of 2D pentagonal materials that could be synthesized in experiments. We summarize the experimental and theoretical efforts in this burgeoning subfield of 2D materials research. We also suggest several issues that DFT calculations can continue to address to develop the subfield. We expect this brief review to stimulate further experimental and computational interests in synthesizing and designing new 2D pentagonal materials.
关键词： Density functional theory calculations,Pentagonal geometries,Two-dimensional materials
更新于2025-09-23 15:22:29
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Quantum Calligraphy: Writing Single-Photon Emitters in a Two-Dimensional Materials Platform
摘要： We present a paradigm for encoding strain into two dimensional materials (2DM) to create and deterministically place single photon emitters (SPEs) in arbitrary locations with nanometer-scale precision. Our material platform consists of a 2DM placed on top of a deformable polymer film. Upon application of sufficient mechanical stress using an atomic force microscope tip, the 2DM/polymer composite deforms, resulting in formation of highly localized strain fields with excellent control and repeatability. We show that SPEs are created and localized at these nanoindents, and exhibit single photon emission up to 60K, the highest temperature reported in these materials. This quantum calligraphy allows deterministic placement and real time design of arbitrary patterns of SPEs for facile coupling with photonic waveguides, cavities and plasmonic structures. In addition to enabling versatile placement of SPEs, these results present a general methodology for imparting strain into 2DM with nanometer-scale precision, providing an invaluable tool for further investigations and future applications of strain engineering of 2DM and 2DM devices.
关键词： tungsten disulfide,atomic force microscopy,two-dimensional materials,single photon emitter,strain engineering
更新于2025-09-23 15:22:29
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Two-dimensional-related catalytic materials for solar-driven conversion of CO <sub/>x</sub> into valuable chemical feedstocks
摘要： The discovery of improved chemical processes for CO and CO2 hydrogenation to valuable hydrocarbon fuels and alcohols is of paramount importance for the chemical industry. Such technologies have the potential to reduce anthropogenic CO2 emissions by adding value to a waste stream, whilst also reducing our consumption of fossil fuels. Current thermal catalytic technologies available for CO and CO2 hydrogenation are demanding in terms of energy input. Various alternative technologies are now being developed for COx hydrogenation, with solar-driven processes over two-dimensional (2D) and 2D-related composite materials being particularly attractive due to the abundance of solar energy on Earth and also the high selectivity of defect-engineered 2D materials towards specific valuable products under very mild reaction conditions. This review showcases recent advances in the solar-driven COx reduction to hydrocarbons over 2D-based materials. Optimization of 2D catalyst performance demands interdisciplinary research that embraces catalyst electronic structure manipulation and morphology control, surface/interface engineering, reactor engineering and density functional theory modelling studies. Through improved understanding of the structure–performance relationships in 2D-related catalysts which is achievable through the application of modern in situ characterization techniques, practical photo/photothermal/photoelectrochemical technologies for CO and CO2 reduction to high-valuable products such as olefins could be realized in the not-too-distant future.
关键词： hydrocarbons,feedstocks,two-dimensional materials,solar-driven conversion,catalysis,COx reduction
更新于2025-09-23 15:22:29
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A Strategy toward New Low-Dimensional Hybrid Halide Perovskites with Anionic Spacers
摘要： The low-dimensional halide perovskites have received enormous attention due to their unique photovoltaic and optoelectronic performances. Periodic spacers are used to inhibit the growth of 3D perovskite and fabricate a 2D counterpart with layered structure, mostly based on organic/inorganic cations. Herein, by introducing organic anions (e.g., pentanedioic acid (PDA) and hexanedioic acid (HDA) simultaneously), leaf-shaped (Cs3Pb2Br5)2(PDA–HDA) microplates with low-dimensional structure are synthesized. They also exhibit significant photoluminescence (PL) centered at 540 nm with a narrow emission peak. The synthesis of single crystals of Pb(PDA) and Pb(HDA) allows to further clarify the crystal structure of (Cs3Pb2Br5)2(PDA–HDA) perovskite and its structural evolution mechanism. Moreover, the cooperative introduction of dicarboxylic acid pairs with appropriate lengths is thermodynamically favored for the low-dimensional perovskite crystallization. The temperature-dependent PL indicates a V-shaped Stokes shift with elevated temperature that could be associated with the localization of excitons in the inorganic layers between organic dicarboxylic acid molecules. This work demonstrates low-dimensional halide perovskite with anionic spacers, which also opens up a new approach to the growth of low-dimensional organic–inorganic hybrid perovskite crystals.
关键词： photoluminescence,low-dimensional materials,nanocrystals,halide perovskites
更新于2025-09-23 15:22:29
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Current Rectification in a Structure: ReSe2/Au Contacts on Both Sides of ReSe2
摘要： Schottky effect of two-dimensional materials is important for nanoscale electrics. A ReSe2 flake is transferred to be suspended between an Au sink and an Au nanofilm. This device is initially designed to measure the transport properties of the ReSe2 flake. However, a rectification behavior is observed in the experiment from 273 to 340 K. The rectification coefficient is about 10. The microstructure and elements composition are systematically analyzed. The ReSe2 flake and the Au film are found to be in contact with the Si substrate from the scanning electron microscope image in slant view of 45°. The ReSe2/Si and Si/Au contacts are p-n heterojunction and Schottky contacts. Asymmetry of both contacts results in the rectification behavior. The prediction based on the thermionic emission theory agrees well with experimental data.
关键词： Two-dimensional materials,Rectification,ReSe2
更新于2025-09-23 15:22:29