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Investigation on Near-Infrared Quantitative Detection based on Heteromorphic Sample Pool
摘要： To enhance the detection precision of samples with scattering characteristics by near infrared spectroscopy (NIRS), this study developed a heteromorphic sample pool and established the related 2D light intensity acquisition system, which can simultaneously acquire multi-path exit light adsorption and scattering information of the samples under test. The Intralipid-20% phantom solutions in 34 samples with different concentrations were detected, while one-dimensional (1D) exit light intensity distributions and two-dimensional (2D) exit light intensity distributions on the surface of the samples were analyzed and modeled using partial least squares. In contrast with the prediction results based on the modeling method of 1D exit light intensity distribution, the modeling method of 2D exit light intensity distribution exhibits more favorable results; specifically, correlation coefficient enhanced by 2.48%, while root mean square error reduced by 6.89%. The experimental results demonstrate that using heteromorphic sample pool can effectively achieve NIRS-based detection precision and speed of chemical components in the solutions with scattering characteristics, which can provide important references for high-throughput and high-precision detection of turbid media in analytical chemistry.
关键词： two-dimensional (2D) light intensity distribution,heteromorphic sample pool,near-infrared spectrum
更新于2025-09-23 15:22:29
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Electrochemical Polishing of Two-Dimensional Materials
摘要： Two-dimensional (2D) layered materials demonstrate their exquisite properties such as high temperature superconductivity, superlubricity, charge density wave, piezotronics, flextronics, straintronics, spintronics, valleytronics, and optoelectronics, mostly, at the monolayer limit. Following initial breakthroughs based on micromechanically exfoliated 2D monolayers, significant progress has been made in recent years towards the bottom-up synthesis of large-area monolayer 2D materials such as MoS2 and WS2 using physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques in order to facilitate their transition into commercial technologies. However, the nucleation and subsequent growth of the secondary, tertiary, and greater numbers of vertical layers poses a significant challenge not only towards the realization of uniform monolayers, but also to maintain their consistent electronic and optoelectronic properties which change abruptly when transitioning from the monolayer to multilayer form. Chemical or physical techniques which can remove the unwarranted top layers without compromising the material quality will have tremendous consequence towards the development of atomically flat, large-area, uniform monolayers of 2D materials. Here, we report a simple, elegant, and self-limiting electrochemical polishing technique which can thin down any arbitrary thickness of 2D material, irrespective of whether these are obtained using powder vapor transport (PVT) or mechanical exfoliation, into their corresponding monolayer form at room temperature within a few seconds without compromising their atomistic integrity. The effectiveness of this electrochemical polishing technique is inherent to 2D transition metal dichalcogenides (TMDCs) owing to the stability of their basal planes, enhanced edge reactivity, and stronger-than-van der Waals (vdW) interaction with the substrate. Our study also reveals that 2D monolayers are chemically more robust and corrosion resistant compared to their bulk counterparts in similar oxidative environments which enables electrochemical polishing of such materials down to a monolayer.
关键词： physical vapor transport,MoS2,WS2,monolayer,corrosion,two-dimensional (2D) materials,electrochemical polishing,electro-ablation
更新于2025-09-23 15:21:21
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Two-dimensional Hybrid Halide Perovskites: Principles and Prom-ises
摘要： Hybrid halide perovskites have become the “next big thing” in emerging semiconductor materials as the past decade witnessed their successful application in high-performance photovoltaics. This resurgence has seen enormous and widespread development of the three-dimensional (3D) perovskites, spearheaded by CH3NH3PbI3. The next generation of halide perovskites, however, is characterized by reduced dimensionality perovskites, emphasizing on the two-dimensional (2D) perovskite derivatives which expand as a more diverse subgroup of semiconducting hybrids that possesses even higher tunability and excellent photophysical properties. In this perspective, we begin with a historical flashback that traces back to early reports before the “perovskite fever” and we follow this original work to its fruition in the present day, where 2D halide perovskites are on the spotlight of current research, thriving on several aspects of high-performance optoelectronics. We approach the evolution of 2D halide perovskites from a structural perspective, providing a classification for the diverse structure-types of the materials, which largely dictate the unusual physical properties observed. We sort out the 2D hybrid halide perovskite based on two key components: the inorganic layers and their modification and the organic cation diversity. As these two heterogeneous components blend, either by synthetic manipulation (shuffling the organic cations or inorganic elements) or by external stimuli (temperature and pressure), the modular perovskite structure evolves to construct crystallographically defined quantum wells (QW). The complex electronic structure that arises is sensitive to the structural features that could be in turn used as a knob to control the dielectric and optical properties the QWs. We conclude this perspective with the most notable optoelectronic device achievements that have been demonstrated to date with an eye towards future material discovery and potential technological developments.
关键词： two-dimensional (2D) perovskite derivatives,optoelectronic devices,quantum wells (QW),Hybrid halide perovskites,semiconducting hybrids
更新于2025-09-23 15:21:01
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Complementary doping of van der Waals materials through controlled intercalation for monolithically integrated electronics
摘要： Doping control has been a key challenge for electronic applications of van der Waals materials. Here, we demonstrate complementary doping of black phosphorus using controlled ionic intercalation to achieve monolithic building elements. We characterize the anisotropic electrical transport as a function of ion concentrations and report a widely tunable resistivity up to three orders of magnitude with characteristic concentration dependence corresponding to phase transitions during intercalation. As a further step, we develop both p-type and n-type field effect transistors as well as electrical diodes with high device stability and performance. In addition, enhanced charge mobility from 380 to 820 cm2/(V·s) with the intercalation process is observed and explained as the suppressed neutral impurity scattering based on our ab initio calculations. Our study provides a unique approach to atomically control the electrical properties of van der Waals materials, and may open up new opportunities in developing advanced electronics and physics platforms.
关键词： nanoelectronics,two-dimensional (2D) materials and heterostructures,tunable properties,diode,black phosphorus,FET
更新于2025-09-23 15:19:57
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Layer-dependent signatures for exciton dynamics in monolayer and multilayer WSe2 revealed by fluorescence lifetime imaging measurement
摘要： Two-dimensional (2D) transition-metal dichalcogenide (TMD) materials have aroused noticeable interest due to their distinguished electronic and optical properties. However, little is known about their complex exciton properties together with the exciton dynamics process which have been expected to influence the performance of optoelectronic devices. The process of fluorescence can well reveal the process of exciton transition after excitation. In this work, the room-temperature layer-dependent exciton dynamics properties in layered WSe2 are investigated by the fluorescence lifetime imaging microscopy (FLIM) for the first time. This paper focuses on two mainly kinds of excitons including the direct transition neutral excitons and trions. Compared with the lifetime of neutral excitons (< 0.3 ns within four-layer), trions possess a longer lifetime (~ 6.6 ns within four-layer) which increases with the number of layers. We attribute the longer-lived lifetime to the increasing number of trions as well as the varieties of trion configurations in thicker WSe2. Besides, the whole average lifetime increases over 10% when WSe2 flakes added up from monolayer to four-layer. This paper provides a novel tuneable layer-dependent method to control the exciton dynamics process and finds a relatively longer transition lifetime of trions at room temperature, enabling to investigate in the charge transport in TMD-based optoelectronics devices in the future.
关键词： two-dimensional (2D) WSe2,fluorescence lifetime,fluorescence lifetime imaging microscopy (FLIM),exciton dynamics,density functional theory (DFT)
更新于2025-09-23 15:19:57
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Tellurene Photodetector with High Gain and Wide Bandwidth
摘要： Two-dimensional (2D) semiconductors have been extensively explored as a new class of materials with great potential. In particular, black phosphorus (BP) has been considered to be a strong candidate for applications such as high-performance infrared photodetectors. However, the scalability of BP thin film is still a challenge, and its poor stability in the air has hampered the progress of the commercialization of BP devices. Herein, we report the use of hydrothermal-synthesized and air-stable 2D tellurene nanoflakes for broadband and ultrasensitive photodetection. The tellurene nanoflakes show high hole mobilities up to 458 cm2/V·s at ambient conditions, and the tellurene photodetector presents peak extrinsic responsivity of 383 A/W, 19.2 mA/W, and 18.9 mA/W at 520 nm, 1.55 μm, and 3.39 μm light wavelength, respectively. Due to the photogating effect, high gains up to 1.9 ×103 and 3.15×104 are obtained at 520 nm and 3.39 μm wavelength, respectively. At the communication wavelength of 1.55μm, the tellurene photodetector exhibits an exceptionally high anisotropic behavior, and a large bandwidth of 37 MHz is obtained. The photodetection performance at different wavelength is further supported by the corresponding quantum molecular dynamics (QMD) simulations. Our approach has demonstrated the air-stable tellurene photodetectors that fully cover the short-wave infrared band with ultrafast photoresponse.
关键词： air-stable,two-dimensional (2D),wide bandwidth,tellurene,photodetector,high gain
更新于2025-09-12 10:27:22
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Quantum Multibody Interactions in Halide-Assisted Vapor-Synthesized Monolayer WSe <sub/>2</sub> and Its Integration in a High Responsivity Photodetector with Low-Interface Trap Density
摘要： Among the two-dimensional (2D) transitional-metal dichalcogenides, monolayer (1L) tungsten diselenide (WSe2) has recently attracted a great deal of interest because of its direct band gap and tunable charge transport behavior, making it attractive for a variety of electronic and optoelectronic applications. Controlled and efficient synthesis of 1L WSe2 using chemical vapor deposition (CVD) is often challenging because of the high temperatures required to generate a steady flux of tungsten atoms in the vapor phase from the oxide precursors. Here, the use of halide-assisted low-pressure CVD with NaCl helps to reduce the growth temperature to ～750 °C, which is lower than the typical temperatures needed with conventional CVD for realizing 1L WSe2. Moreover, we experimentally probed the quantum multibody interactions in 1L WSe2 ascribed to excitons, trions, and other localized states by analyzing the temperature-dependent photoluminescence spectra, where such multibody interactions govern the intrinsic electronic and optoelectronic properties of 1L WSe2 for device platforms. The role of the metal?2D semiconductor interface is also critical to realize high-performance devices. In this study, a 1L WSe2-based photodetector was fabricated using Al contacts, which shows a high photoresponsivity, and the interface-state density Dit of the Al/WSe2 junction was computed to be the lowest reported to date ～3.45 × 1012 cm?2 eV?1. Our work demonstrates the tremendous potential of WSe2 to open avenues for state-of-the-art electronic, optoelectronic, and quantum-optoelectronic devices using scalable synthesis routes.
关键词： transitional-metal dichalcogenides,photodetector,tungsten diselenide (WSe2),two-dimensional (2D) materials,quantum multibody interactions,interface-state density,chemical vapor deposition (CVD)
更新于2025-09-11 14:15:04
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Single titanium-oxide species implanted in 2D g-C3N4 matrix as a highly efficient visible-light CO2 reduction photocatalyst
摘要： A visible-light-response, efficient and robust photo-catalyst for CO2 reduction is highly desirable. Herein, we demonstrate that single titanium-oxide species implanted in two-dimensional (2D) graphitic carbon nitride (g-C3N4) matrix (2D TiO-CN) can efficiently photo-catalyze the reduction of CO2 to CO under the irradiation of visible light. The synergistic interaction between single titanium oxide species and g-C3N4 in 2D TiO-CN not only enhances the separation of photo-excited charges, but also results in visible light response of single titanium-oxide species, realizing high activity of CO2 photo-reduction with extremely high CO generation rate of 283.9 μmol·h?1·g?1, 5.7, 6.8 and 292.2 times larger than those of TiO2/CN hybrid material, CN and commercial TiO2, respectively. Time-resolved fluorescence and electron spin resonance spectroscopy revealed the catalytic mechanism of the fabricated 2D TiO-CN photocatalysts for CO2 reduction.
关键词： two-dimensional (2D) photocatalysts,graphitic carbon nitride,visible-light,single atom catalyst,CO2 reduction
更新于2025-09-11 14:15:04
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Direct, transfer-free growth of large-area hexagonal boron nitride films by plasma-enhanced chemical film conversion (PECFC) of printable, solution-processed ammonia borane
摘要： Synthesis of large-area hexagonal boron nitride (h-BN) films for two-dimensional (2D) electronic applications typically requires high temperatures (~1000 oC) and catalytic metal substrates which necessitate transfer. Here, analogous to plasma-enhanced chemical vapor deposition, a non-thermal plasma is employed to create energetic and chemically-reactive states such as atomic hydrogen and convert a molecular precursor film to h-BN at temperatures as low as 500 oC directly on metal-free substrates – a process we term plasma-enhanced chemical film conversion (PECFC). Films containing ammonia borane as a precursor are prepared by a variety of solution processing methods including spray deposition, spin coating, and ink-jet printing, and reacted in a cold-wall reactor with a planar dielectric barrier discharge operated at atmospheric pressure in a background of argon or mixture of argon and hydrogen. Systematic characterization of the converted h-BN films by micro Raman spectroscopy shows that the minimum temperature for nucleation on silicon-based substrates can be lowered from 800 to 500 oC by the addition of a plasma. Furthermore, the crystalline domain size, as reflected by a decrease in the full-width-half-maximum, increased by more than 3 times (>40 cm-1 to ~13 cm-1). To demonstrate the potential of the h-BN films as a gate dielectric in 2D electronic devices, molybdenum disulfide field-effect transistors were fabricated and the field effect mobility was found to be improved by up to four times over silicon dioxide. Overall, PECFC allows h-BN films to be grown at lower temperatures and with improved crystallinity than CVD, directly on substrates suitable for electronic device fabrication.
关键词： two-dimensional (2D) material,plasma,chemical vapor deposition (CVD),boron nitride (BN)
更新于2025-09-11 14:15:04
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Janus Group-Ⅲ Chalcogenide Monolayers and Derivative Type-Ⅱ Heterojunctions as Water Splitting Photocatalysts with Strong Visible Light Absorbance
摘要： Search for two-dimensional (2D) water splitting photocatalysts is crucial to solve energy crises and environmental problems. In this research, we study the electronic and photocatalytic properties of single-layer Ga2X1X2 (Ga2SeTe, Ga2STe and Ga2SSe) and newly proposed α-Ga2S3/Ga2SSe-A, α-Ga2S3/Ga2SSe-B and α-Ga2S3/Ga2SSe-C van der Walls heterojunctions using first-principles calculations. Theoretical results indicate Ga2X1X2 monolayers present suitable band edges. 2D α-Ga2S3/Ga2SSe-B and α-Ga2S3/Ga2SSe-C belong to type-Ⅱ heterojunctions, and under biaxial strains embody suitable band edges. Comparisons of the valence band maximum (VBM) charge and electric dipole of α-Ga2S3/Ga2SSe-A and α-Ga2S3/Ga2SSe-B demonstrate it is possible to achieve suitable band edges for water splitting by switching electric dipoles. Especially, the three Ga2X1X2 monolayers, α-Ga2S3/Ga2SSe-B and α-Ga2S3/Ga2SSe-C heterojunctions absorb a large amount of visible light, promising they are photocatalysts for water splitting. More importantly, we find the optical absorption coefficients of 2D monolayers and heterojunctions in previous calculations are several times underestimated because the effective volume is not taken into consideration. To obtain reliable absorption coefficients, the real and imaginary parts of dielectric function must be renormalized.
关键词： visible light absorbance,van der Waals heterojunctions,two-dimensional (2D) materials,Janus group-Ⅲ chalcogenide monolayers,water splitting photocatalysts,first-principles calculations
更新于2025-09-10 09:29:36