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Macroscopic Au@PANI Core/shell Nanoparticle Superlattice Monolayer Film with Dual-responsive Plasmonic Switches
摘要： The self-assembled gold nanoparticles superlattice displays unusual but distinctive features such as highly mechanical and free-standing performance, electrical conductivity and plasmonic properties, which were widely employed in various applications especially in biological diagnostics and optoelectronic devices. Two-dimensional (2D) superlattice monolayer film composed of a given metal nanostructure, it is rather challenging to tune either its plasmonic properties or its optical properties in a reversible way, and it is not reported. It is therefore of significant value to construct free-standing 2D superlattice monolayer film of gold nanoparticles with intelligent response and desired functions. Herein, we developed an easy and efficient approach to construct gold nanoparticles superlattice film with a dual-responsive plasmonic switch. In this system, gold nanoparticles were firstly coated by polyaniline (PANI), and then interracially self-assembled into monolayer film at the air-liquid interface. PANI shell plays two important roles in superlattice monolayer film. Firstly, PANI shell acts as a physical spacer to provide a steric hindrance to counteract the van der Waals (vdWs) attraction between densely packed nanoparticles (NPs), resulting in the formation of superlattice by adjusting the thickness of the PANI shell. Secondly, PANI shells provide superlattice film with multiple stimuli such as electrical potential and pH change, leading to reversible optical and plasmonic responsive. Superlattice monolayer film can show a vivid color change from olive green to pink, or from olive green to violet by the change of corresponding stimuli. And the localized surface plasmonic resonance (LSPR) of superlattice monolayer film can be reversibly modulated by changing both local pH and applying electric potential. Notably, a significant plasmonic shift of superlattice monolayer film can be achieved to 157 nm, when PANI shell with the thickness of 35 nm and gold nanorods as core were used. The superlattice monolayer film with dual-responsive plasmonic switches is promising for a range of potential applications in optoelectronic devices, plasmonic and colorimetric sensors, and Surface enhanced Raman scattering (SERS).
关键词： plasmonic switching,dual-responsive,superlattice,2D monolayer film,core shell structure
更新于2025-09-19 17:13:59
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Tip-Enhanced Infrared Imaging with Sub-10 nm Resolution and Hypersensitivity
摘要： Here, we demonstrate sub-10 nm spatial resolution sampling a volume of ~360 molecules with a strong field enhancement at the sample-tip junction by implementing noble metal substrates (Au, Ag, Pt) in photo-induced force microscopy (PiFM). This technique shows versatility and robustness of PiFM, and is promising for application in interfacial studies with hypersensitivity and super spatial resolution.
关键词： hypersensitivity,molecular monolayer,Photo-induced force microscopy,super spatial resolution
更新于2025-09-19 17:13:59
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Chiral Second-Harmonic Generation from Monolayer WS <sub/>2</sub> /Aluminum Plasmonic Vortex Metalens
摘要： Two-dimensional spiral plasmonic structures have emerged as a versatile approach to generate near-field vortex fields with tunable topological charges. We demonstrate here a far-field approach to observe the chiral second-harmonic generation (SHG) at designated visible wavelengths from a single plasmonic vortex metalens. This metalens comprises an Archimedean spiral slit fabricated on atomically flat aluminum epitaxial film, which allows for precise tuning of plasmonic resonances and subsequent transfer of two-dimensional materials on top of the spiral slit. The nonlinear optical measurements show a giant SHG circular dichroism. Furthermore, we have achieved an enhanced chiral SHG conversion efficiency (about an order of magnitude greater than the bare aluminum lens) from monolayer tungsten disulfide (WS2)/aluminum metalens, which is designed at the C-exciton resonance of WS2. Since the C-exciton is not a valley exciton, the enhanced chiral SHG in this hybrid system originates from the plasmonic vortex field-enhanced SHG under the optical spin-orbit interaction.
关键词： optical spin-orbit interaction,Surface plasmonic vortex metalens,aluminum epitaxial film,chiral nonlinearity,second-harmonic generation,monolayer tungsten disulfide
更新于2025-09-19 17:13:59
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Controlled Synthesis of Large Scale Continuous monolayer WS2 Film by Atmospheric Pressure Chemical Vapor Deposition
摘要： Synthesis of monolayer transition metal dichalcogenides (TMDs) in large-size is crucial to their practical applications in electronics and optoelectronics. Here, large scale continuous monolayer WS2 film has been successfully grown by atmospheric pressure chemical vapor deposition (APCVD) method. By modulating three growth parameters, Ar gas flow rate, the temperature of WO3 precursor and the distance between substrate and WO3 precursor, WS2 film with different grain size can be obtained. At optimal processing condition, large-scale monolayer WS2 with lateral dimension can reach 1 millimeter above. This would pave the way for scale production of continuous monolayer TMDs film.
关键词： large scale,monolayer WS2,atmospheric pressure chemical vapor deposition,continuous film
更新于2025-09-16 10:30:52
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Monolayer MoSe <sub/>2</sub> /NiO van der Waals heterostructures for infrared light-emitting diodes
摘要： Nowadays monolayer transition metal chalcogenides (TMCs) have been widely researched due to their excellent optoelectronic properties. However, the preparation of large-sized monolayer TMCs and high-power TMC-based light-emitting diodes are still full of challenges, which limit their application in two-dimensional devices. Here, the large-sized monolayer single-crystalline MoSe2 was synthesized by chemical vapor deposition. The influence of the relative gas pressure ratio of MoO3 to Se on MoSe2 morphology is discussed. The TEM analysis confirmed the presence of 2H-phase monolayer MoSe2. A photoluminescence peak from the MoSe2 monolayer is detected at about 804 nm, illustrating an intrinsic energy bandgap of 1.54 eV. Importantly, a novel 2D/3D heterostructure, monolayer MoSe2/NiO van der Waals heterostructure, is constructed for a light-emitting diode (LED). The electroluminescence peaks of n-MoSe2/p-NiO LED locate at 812 nm, 848 nm and 918 nm, all of which are in the infrared light range. Interestingly, the electroluminescence peaks of our n-MoSe2/p-NiO LED are close to those of conventional air conditioner telecontrollers. So the n-MoSe2/p-NiO infrared LED is forward to be used in infrared remote sensing systems in the future.
关键词： van der Waals heterostructures,infrared light-emitting diodes,Monolayer MoSe2,chemical vapor deposition,NiO
更新于2025-09-16 10:30:52
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Influence of exciton energy on intersubband transition of chirped superlattice GaAs/AlGaAs quantum cascade laser
摘要： The influence of exciton energy on intersubband transition was simulated for a chirped supperlattice quantum cascade laser of GaAs/AlxGa1-xAs. Exciton energy was modelled as a function of QW width for alloys of various percentages of constituent elements. The results showed that the exciton energy decreased proportionally with increasing QW width. Models were also generated to study exciton energy as a function of the percent alloy contents of AlxGa1-xAs barriers for QWs of various widths. Exciton energy showed characteristics of higher discrete energy when QW width was narrower. Transition energy was also simulated from 1e and 2e to the 1s exciton state as functions of applied electric field at various QW widths. Our simulation results showed that the transition energy from 2e to the 1s exciton state increased proportionally to the increasing strength of the electric field. This transition energy was indicative of THz range radiation.
关键词： percent alloy contents,chirped superlattice quantum cascade laser,aluminum arsenide monolayer,THz radiation,transition energy
更新于2025-09-16 10:30:52
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CVD controlled growth of large-scale WS <sub/>2</sub> monolayers
摘要： Monolayer tungsten disulfide (WS2) with a direct band gap of ca. 2.0 eV and stable properties has been a hotspot in two-dimensional (2D) nanoelectronics and optoelectronics. However, it remains challenging to successfully prepare monolayer WS2. In this paper, we report the chemical vapor deposition (CVD) growth behavior of hexagonal WS2 monolayers by using WS2 powders and sodium triosulfate (Na2S2O3) as precursors. We observed the Na2S2O3 has a significant effect on the WS2 triangular and leaf-like shapes. In addition, based on proposed S-termination and W-termination theory, the growth mechanisms for different shapes of WS2 were discussed.
关键词： monolayer,WS2,CVD,growth mechanism,Na2S2O3
更新于2025-09-16 10:30:52
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2D alloying molybdenum tin-disulfide monolayers with fast photoresponse
摘要： Elemental alloying in monolayer, two-dimensional (2D) transition metal dichalcogenides (TMDs) promises unprecedented ability to modulate their electronic structure leading to the unique optoelectronic properties. MoS2 monolayer based photodetectors typically exhibit a high photoresponsivity but suffer from a low response time. Here we develop a new approach for Sn alloying in MoS2 monolayers based on the synergy of the customized chemical vapor deposition (CVD) and the effects of common salt (NaCl) to produce high-quality and large-size Mo1-xSnxS2 (x<0.5) alloy monolayers. The composition difference results in different growth behaviors; Mo dominated alloys (x<0.5) exhibit uniform and large size (up to 100 μm) triangular monolayers, while Sn dominated alloys (x>0.5) present multilayer grains. The Mo1-xSnxS2 (x<0.5) based photodetectors and phototransistors exhibit a maximum responsitivity of 12 mA/W and a minimum response time of 20 ms, which is faster than most reported MoS2 based photodetectors. This work offers new perspectives for precision 2D alloy engineering to improve the optoelectronic performance of TMD-based photodetectors.
关键词： photodetector,Mo1-xSnxS2 monolayer,chemical vapor depostion,NaCl,response time
更新于2025-09-16 10:30:52
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Electric Field Controlled Indirect-Direct-Indirect Band Gap Transition in Monolayer InSe
摘要： Electronic structures of monolayer InSe with a perpendicular electric field are investigated. Indirect-direct-indirect band gap transition is found in monolayer InSe as the electric field strength is increased continuously. Meanwhile, the global band gap is suppressed gradually to zero, indicating that semiconductor-metal transformation happens. The underlying mechanisms are revealed by analyzing both the orbital contributions to energy band and evolution of band edges. These findings may not only facilitate our further understanding of electronic characteristics of layered group III-VI semiconductors, but also provide useful guidance for designing optoelectronic devices.
关键词： Monolayer InSe,Electric field,Indirect-direct-indirect band gap transition
更新于2025-09-16 10:30:52
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Synthesis of Monolayer Blue Phosphorus Enabled by Silicon Intercalation
摘要： The growth of entirely synthetic two-dimensional (2D) materials could further expand the library of naturally occurring layered solids and provide opportunities to design materials with finely tunable properties. Among them, the synthesis of elemental 2D materials is of particular interest as they represent the chemically simplest case and serve as model system for exploring the on-surface synthesis mechanism. Here, a pure atomically-thin blue phosphorous (BlueP) monolayer is synthesized via silicon intercalation of the BlueP-Au alloy on Au(111). The intercalation process is characterized at the atomic scale by low-temperature scanning probe microscopy, and further corroborated by synchrotron radiation-based x-ray photoelectron spectroscopy measurements. The evolution of the band structures from BlueP-Au alloy into Si intercalated BlueP are clearly revealed by angle-resolved photoemission spectroscopy and further verified by density functional theory calculations.
关键词： MBE,STM,Si intercalation,monolayer blue phosphorus,ARPES
更新于2025-09-16 10:30:52