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Implementation of continuous fast scanning detection in femtosecond Fourier-transform two-dimensional vibrational-electronic spectroscopy to decrease data acquisition time
摘要： Femtosecond Fourier transform two-dimensional vibrational-electronic (2D VE) spectroscopy is a recently developed third-order nonlinear spectroscopic technique to measure coupled electronic and vibrational motions in the condensed phase. The viability of femtosecond multidimensional spectroscopy as an analytical tool requires improvements in data collection and processing to enhance the signal-to-noise ratio and increase the amount of data collected in these experiments. Here a continuous fast scanning technique for the efficient collection of 2D VE spectroscopy is described. The resulting 2D VE spectroscopic method gains sensitivity by reducing the effect of laser drift, as well as decreasing the data collection time by a factor of 10 for acquiring spectra with a high signal-to-noise ratio within 3 dB of the more time intensive step scanning methods. This work opens the door to more comprehensive studies where 2D VE spectra can be collected as a function of external parameters such as temperature, pH, and polarization of the input electric fields.
关键词： Femtosecond Fourier transform,two-dimensional vibrational-electronic spectroscopy,laser drift,fast scanning,signal-to-noise ratio
更新于2025-09-10 09:29:36
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EXPRESS: Two-Dimensional Correlation Spectroscopy (2D-COS) for Analysis of Spatially Resolved Vibrational Spectra
摘要： The last two decades have seen tremendous progress in the application of two-dimensional correlation spectroscopy (2D-COS) as a versatile analysis method for data series obtained by a large variety of different spectroscopic modalities, including infrared (IR) and Raman spectroscopy. The analysis technique is applicable to a series of spectra recorded under the influence of an external sample perturbation. 2D-COS analysis is not only helpful to decipher correlations which may exist between distinct spectral features, but can be utilized also to obtain the sequence of individual spectral changes. The focus of this review article is on the application of 2D-COS for analyzing spatially resolved data with special emphasis on hyperspectral imaging (HSI) study. In this review, we briefly introduce the fundamentals of the generalized 2D-COS analysis approach, discuss specific points of 2D-COS application to spatially resolved spectra and demonstrate essential aspects of data pre-processing for 2D-COS analysis of spatially resolved spectra. Based on illustrative examples we show that 2D-COS is useful for spectral band assignment in HSI applications and demonstrate its utility for detecting subtle correlations between spectra features, or between features from different imaging modalities in the case of heterospectral (multimodal) HSI. Furthermore, a short overview on existing 2D-COS software tools is provided. It is hoped that this article represents not only a useful guideline for 2D-COS analyses of spatially resolved hyperspectral data but supports also further dissemination of the 2D-COS analysis method as a whole.
关键词： Spatially Resolved Vibrational Microspectroscopy,Multimodal Imaging,Two-Dimensional Correlation Spectroscopy (2D-COS),Hyperspectral Imaging
更新于2025-09-10 09:29:36
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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
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Photonic spin Hall effect of monolayer black phosphorus in the Terahertz region
摘要： As a two-dimensional (2D) material, black phosphorus (BP) has attracted significant attention owing to exotic physical properties such as low-energy band gap, high carrier mobility, and strong in-plane anisotropy. The striking in-plane anisotropy is a promising candidate for novel light-matter interaction. Here, we investigate the photonic spin Hall effect (PSHE) on a monolayer of BP. Due to the in-plane anisotropic property of BP, the PSHE is accompanied with Goos-H?nchen and Imbert-Fedorov effects, resulting in an asymmetric spin splitting. The asymmetric spin splitting can be flexibly tuned by the angle between the incident plane and the armchair crystalline direction of BP and by the carrier density via a bias voltage. The centroid displacements of two opposite spin components of the reflected beam along directions parallel and perpendicular to the incident plane can be considered as four independent channels for information processing. The potential application in barcode-encryption is proposed and discussed. These findings provide a deeper insight into the spin-orbit interaction in 2D material and thereby facilitate the development of optoelectronic devices in the Terahertz region.
关键词： in-plane anisotropy,two-dimensional material,black phosphorus,photonic spin Hall effect
更新于2025-09-10 09:29:36
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Coherent multidimensional spectroscopy of dilute gas-phase nanosystems
摘要： Two-dimensional electronic spectroscopy (2DES) is one of the most powerful spectroscopic techniques with unique sensitivity to couplings, coherence properties and real-time dynamics of a quantum system. While successfully applied to a variety of condensed phase samples, high precision experiments on isolated systems in the gas phase have been so far precluded by insufficient sensitivity. However, such experiments are essential for a precise understanding of fundamental mechanisms and to avoid misinterpretations. Here, we solve this issue by extending 2DES to isolated nanosystems in the gas phase prepared by helium nanodroplet isolation in a molecular beam-type experiment. This approach uniquely provides high flexibility in synthesizing tailored, quantum state-selected model systems of single and many-body character. In a model study of weakly-bound Rb2 and Rb3 molecules we demonstrate the method’s unique capacity to elucidate interactions and dynamics in tailored quantum systems, thereby also bridging the gap to experiments in ultracold quantum science.
关键词： Two-dimensional electronic spectroscopy,helium nanodroplet isolation,gas-phase nanosystems,ultracold quantum science,Rb2 and Rb3 molecules
更新于2025-09-10 09:29:36
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Review of photoresponsive properties at SrTiO <sub/>3</sub> -based heterointerfaces
摘要： The two-dimensional electron gas at SrTiO3-based heterointerfaces has received a great deal of attention in recent years owing to their potential for the exploration of emergent physics and the next generation of electronics. One of the most fascinating aspects in this system is that the light, as a powerful external perturbation, can modify its transport properties. Recent studies have reported that SrTiO3-based heterointerfaces exhibit the persistent photoconductivity and can be tuned by the surface and interface engineering. These researches not only reveal the intrinsic physical mechanisms in the photoresponsive process, but also highlight the ability to be used as a tool for novel all-oxide optical devices. This review mainly contraposes the studies of photoresponse at SrTiO3-based heterointerfaces.
关键词： persistent photoconductivity (PPC),complex oxides,two-dimensional electron gas,LaAlO3/SrTiO3 heterointerfaces
更新于2025-09-10 09:29:36
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Tensile mechanical properties and fracture behavior of monolayer InSe under axial tension
摘要： Based on a newly developed interatomic potential, the mechanical properties and fracture behavior of monolayer InSe are investigated by using the classical molecular dynamics method. We ?nd that monolayer InSe exhibits excellent mechanical properties comparing with other two-dimensional materials. Especially, it can sustain an axial tensile strain of 27% in the zigzag direction at room temperature 300 K. Furthermore, the numerical results indicate that the monolayer InSe has an isotropy in the mechanical behaviors with the Youngs modulus being about 43 N/m both in the armchair and zigzag directions. We also discuss the e?ects of temperature and strain rate on the mechanical properties of monolayer InSe and ?nd the high temperature-sensitivity. It’s found that the mechanical properties signi?cantly decrease as the increasing temperature. In contrast, the mechanical properties has a relatively weak dependence on the strain rate. As the strain rate increases from 0.0002 to 0.0008 ps?1, Young’s modulus nearly keeps a constant. The fracture stress and strain in armchair direction only increase by 3.6% and 8.3%, respectively.
关键词： Tensile strain,Monolayer InSe,Molecular dynamics simulation,Two-dimensional materials,Mechanical property
更新于2025-09-10 09:29:36
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Biological interactions of biocompatible and water-dispersed MoS2 nanosheets with bacteria and human cells
摘要： Two dimensional materials beyond graphene such as MoS2 and WS2 are novel and interesting class of materials whose unique physico-chemical properties can be exploited in applications ranging from leading edge nanoelectronics to the frontiers between biomedicine and biotechnology. To unravel the potential of TMD crystals in biomedicine, control over their production through green and scalable routes in biocompatible solvents is critically important. Furthermore, considering multiple applications of eco-friendly 2D dispersions and their potential impact onto live matter, their toxicity and antimicrobial activity still remain an open issue. Herein, we focus on the current demands of 2D TMDs and produce high-quality, few-layered and defect-free MoS2 nanosheets, exfoliated and dispersed in pure water, stabilized up to three weeks. Hence, we studied the impact of this material on human cells by investigating its interactions with three cell lines: two tumoral, MCF7 (breast cancer) and U937 (leukemia), and one normal, HaCaT (epithelium). We observed novel and intriguing results, exhibiting evident cytotoxic effect induced in the tumor cell lines, absent in the normal cells in the tested conditions. The antibacterial action of MoS2 nanosheets is then investigated against a very dangerous gram negative bacterium, such as two types of Salmonellas: ATCC 14028 and wild-type Salmonella typhimurium. Additionally, concentration and layer-dependent modulation of cytotoxic effect is found both on human cells and Salmonellas.
关键词： antibacterial activity,biocompatibility,MoS2 nanosheets,two-dimensional materials,cytotoxicity
更新于2025-09-10 09:29:36
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-shell excitons studied using two-dimensional coherent spectroscopy
摘要： The dephasing mechanisms of p-shell and s-shell excitons in an InAs self-assembled quantum dot ensemble are examined using two-dimensional coherent spectroscopy (2DCS). 2DCS provides a comprehensive picture of how the energy level structure of dots affects the exciton dephasing rates and recombination lifetimes. We find that at low temperatures, dephasing of s-shell excitons is lifetime limited, whereas p-shell excitons exhibit significant pure dephasing due to scattering between degenerate spin states. At elevated temperatures, quadratic exciton-phonon coupling plays an important role in both s-shell and p-shell exciton dephasing. We show that multiple p-shell states are also responsible for stronger phonon dephasing for these transitions.
关键词： quantum dots,two-dimensional coherent spectroscopy,dephasing,InAs,exciton-phonon coupling
更新于2025-09-10 09:29:36
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A new two-dimensional semiconducting carbon allotrope: A first-principles study
摘要： A new two-dimensional carbon allotrope, which consists of 18 atoms in a hexagonal cell, is theoretically investigated by performing first-principle method. The allotrope displays a P6/mmm symmetry (termed as hP-C18 carbon). The new 2D carbon phase has an sp2-sp3 network, consisting of hexagons and octagons formed by near-by atoms. The calculations demonstrate that hP-C18 carbon is a metastable 2D carbon phase compared to graphene, but it is more energetically stable than penta-graphene. The dynamical, thermal and mechanical stabilities are demonstrated by phonon dispersion, ab inito MD simulations and elastic constants, respectively. The analysis of electronic band structure shows that hP-C18 is an indirect semiconductor with a band gap of 2.93 eV (HSE06). Besides, its buckled 3D structure, hP-C18-3D carbon, is also predicted. The stability of the new 3D phase is discussed by phonon dispersion and elastic constants. It is found that hP-C18-3D carbon is a super-hard indirect semiconductor with an indirect band gap of 2.24 eV (HSE06). Thus, hP-C18 carbon and its buckled 3D structure may possess not only potential electronic applications but also mechanical applications.
关键词： metastable,hP-C18 carbon,two-dimensional carbon allotrope,semiconducting,mechanical applications,first-principles study,electronic applications
更新于2025-09-10 09:29:36