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Nonlinear optics at excited states of exciton polaritons in two-dimensional atomic crystals
摘要： Exciton polaritons (EP) are partial-light partial-matter quasiparticles in semiconductors demonstrating striking quantum phenomena such as Bose-Einstein condensation and single-photon nonlinearity. In these phenomena, the governing process is the EP relaxation into the ground states upon excitation, where various mechanisms are extensively investigated with thermodynamic limits. However, the relaxation process becomes drastically different and could significantly advance the understanding of EP dynamics for these quantum phenomena, when excited states of EP are involved. Here, for the first time, we observe nonlinear optical responses at the EP excited states in a monolayer tungsten disulphide (WS2) microcavity, including dark excited states and dynamically metastable upper polariton band. The nonlinear optics leads to unique emissions of ground states with prominent valley degree of freedom (DOF) via anomalous relaxation process, which is applicable to a wide range of semiconductors from monolayer transition metal dichalcogenides (TMDs) to emerging halide perovskites. This work promises possible approaches to challenging experiments such as valley polariton condensation. Moreover, it also constructs a valley-dependent solid state three-level system for terahertz photonics and stimulated Raman adiabatic passage.
关键词： excited states,exciton-polaritons,relaxation dynamics,Nonlinear optics,monolayer transition metal dichalcogenide
更新于2025-09-16 10:30:52
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Rapid, facile, reagentless, and room-temperature conjugation of monolayer MoS2 nanosheets with dual-fluorophore-labled flares as Nanoprobes for ratiometric sensing of TK1 mRNA in living cells
摘要： Direct loading of fluorophore-labeled DNA molecules (named as flares) on gold nanoparticles (AuNPs) is a controllable and straightforward approach for intracellular imaging of target DNA molecules. However, the modification of AuNPs with flares requires a tedious and time-consuming procedure, additional reagents, or adenosine-rich DNA molecules. Here, we developed a rapid, simple, reagentless, and room-temperature approach for the modification of monolayer molybdenum disulfide nanosheets (M-MoS2 NSs) with dual-fluorophore-labeled flares, which were implemented for ratiometric imaging of TK1 mRNA in living cells. The duplexes were prepared by hybridizing thiolated single-stranded DNA (ssDNA) to 6-carboxyfluorescein (FAM)- and 5-carboxytetramethylrhodamine (TAMRA)-labeled flares. Fabrication of the nanoflares was conducted by conjugating the formed duplexes to the surface sulfur vacancy sites of the M-MoS2 NSs. The time for preparing the nanoflares was found to be completed within 1 h. In the nanoflares, FAM stays away from TAMRA, leading to inefficient fluorescence resonance energy transfer (FRET). The presence of perfectly matched DNA (DNApm) molecules induces the liberation of the flares from the nanoflares. The liberated flares fold into hairpin-shaped structures, causing high FRET efficiency from FAM to TAMRA and efficient FAM-TAMRA static quenching. Following this mechanism, the nanoflares provided an effective platform for ratiometric sensing of DNApm molecules with the limit of detection (at a signal-to-noise ratio of 3) of 8 nM and the linear range of 25?500 nM. Confocal microscopy experiments demonstrated that the nanoflares can be used to ratiometrically image TK1 mRNA in HeLa and MCF-7 cells.
关键词： ratiometric sensing,monolayer MoS2 nanosheets,TK1 mRNA,dual-fluorophore-labeled flares,living cells
更新于2025-09-16 10:30:52
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Full Activation of Boron in Silicon Doped by Self-assembled Molecular Monolayers
摘要： The self-assembled molecular monolayer (SAMM) doping has great potential in state-of-the-art nanoelectronics with unique features of atomically precision and non-destructive doping on complex 3D surfaces. However, it was recently found that carbon impurities introduced by the SAMM significantly reduced the activation rate of phosphorus dopants by forming majority carrier traps. Developing a defect-free SAMM doping technique with a high activation rate for dopants becomes critical for reliable applications. Considering that susbstitutional boron does not interact with carbon in silicon, herein we employ Hall measurements and secondary ion mass spectrometry (SIMS) to investigate boron activation rate, and then deep level transient spectroscopy (DLTS) and minority carrier transient spectroscopy (MCTS) to analyze defects in boron-doped silicon by the SAMM technique. Unlike the phosphorus dopants, the activation rate of boron dopants is close to 100%, which is consistent with the defect measurement results (DLTS and MCTS). Only less than 1% boron dopants bind with oxygen impurities, forming majority hole traps. Interestingly carbon-related defects in form of CsH and CsOH act as minority trap states in boron-doped silicon which will only capture electrons. As a result, the high concentration of carbon impurities have no impact on the activation rate of boron dopants.
关键词： boron-doped silicon,Full activation,molecular monolayer doping,carbon-related defects,minority carrier trap
更新于2025-09-12 10:27:22
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The effect of phenylboronic acid-based self-assembled monolayers on theperformance of organic field-effect transistors (OFETs)
摘要： The dielectric/semiconductor interface is one of the most important components strongly affecting the performance of organic field-effect transistors (OFETs). To improve OFET parameters, we applied a series of phenylboronic acid derivatives as self-assembly molecules between dielectric and organic semiconductor layers. Device performance parameters, especially threshold voltage, current on/off ratio, and subthreshold slope, were improved. To elucidate the mechanism, dielectric/semiconductor interfaces were analyzed using atomic force microscope and contact angle techniques.
关键词： self-assembled monolayer,Interface modification,organic field-effect transistor
更新于2025-09-12 10:27:22
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Mobility of charge carriers in self-assembled monolayers
摘要： We present a new approach to study charge transport within 2D layers of organic semi-conductors (OSCs) using atomic force microscopy (AFM)-based lithography applied to self-assembled monolayers (SAMs), fabricated from appropriate organothiols. The extent of lateral charge transport was investigated by insulating pre-defined patches within OSC-based SAMs with regions of insulating SAM made from large band gap alkanethiolates. The new method is demonstrated using a phenyl-linked anthracenethiolate (PAT), 4-(anthracene-2-ylethynyl)benzyl thiolate. I–V characteristics of differently shaped PAT-islands were measured using the AFM tip as a top electrode. We were able to determine a relationship between island size and electrical conductivity, and from this dependence, we could obtain information on the lateral charge transport and charge carrier mobility within the thin OSC layers. Our study demonstrates that AFM nanografting of appropriately functionalized OSC molecules provides a suitable method to determine intrinsic mobilities of charge carriers in OSC thin films. In particular, this method is rather insensitive with regard to influence of grain boundaries and other defects, which hamper the application of conventional methods for the determination of mobilities in macroscopic samples.
关键词： organic semiconductor,self-assembled monolayer,lateral charge transport,nanografting,conducting atomic force microscopy
更新于2025-09-12 10:27:22
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Study properties of monolayers with quantum dots of semiconductors A 2 B 6 and A 3 B 5
摘要： Experimental and theoretical study of semiconductor quantum dots on base multicomponent compounds such as A2B6 and A3B5 performed in the work. It was investigated the peculiarities of the electronic spectra of these nanoparticles by scanning tunneling microscopy. Analysis of results allowed us to estimate the position of the first three levels in the electron spectrum of studied nanosized objects. It was obtained good qualitative and quantitative agreement of experimental results with the theoretical estimate. Developed approach allows us to solve the inverse problem – to clarify the size of nanoscale objects when their chemical composition is precisely known.
关键词： electron energy,monolayer,current-voltage characteristics,quantum dot
更新于2025-09-12 10:27:22
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Synergistic Coassembly of Highly Wettable and Uniform Hole‐Extraction Monolayers for Scaling‐up Perovskite Solar Cells
摘要： All organic charge-transporting layer (CTL)-featured perovskite solar cells (PSCs) exhibit distinct advantages, but their scaling-up remains a great challenge because the organic CTLs underneath the perovskite are too thin to achieve large-area homogeneous layers by spin-coating, and their hydrophobic nature further hinders the solution-based fabrication of perovskite layer. Here, an unprecedented anchoring-based coassembly (ACA) strategy is reported that involves a synergistic coadsorption of a hydrophilic ammonium salt CA-Br with hole-transporting triphenylamine derivatives to acquire scalable and wettable organic hole-extraction monolayers for p–i–n structured PSCs. The ACA route not only enables ultrathin organic CTLs with high uniformity but also eliminates the nonwetting problem to facilitate large-area perovskite films with 100% coverage. Moreover, incorporation of CA-Br in the ACA strategy can distinctly guarantee a high quality of electronic connection via the cations’ vacancy passivation. Consequently, a high power-conversion-efficiency (PCE) of 17.49% is achieved for p–i–n structured PSCs (1.02 cm2), and a module with an aperture area of 36 cm2 shows PCE of 12.67%, one of the best scaling-up results among all-organic CTL-based PSCs. This work demonstrates that the ACA strategy can be a promising route to large-area uniform interfacial layers as well as scaling-up of perovskite solar cells.
关键词： hole-extraction monolayer,perovskite solar cells,scaling-up,modules,anchoring-based coassembly strategy
更新于2025-09-12 10:27:22
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Towards scalable fabrication of atomic wires in silicon by nano-patterning self-assembled molecular monolayers
摘要： Developing a scalable method to fabricate atomic wires is an important step for building solid-state semiconductor quantum computers. In this work, we developed a selective doping strategy by patterning the self-assembled monolayer to a few nanometers using standard nanofabrication processes, which significantly improves the lateral doping resolution of monolayer doping (MLD) from microscale to nanoscale. Using this method, we further explore the possibility to fabricate phosphorus wires in silicon by patterning self-assembled diethyl vinylphosphonate monolayers into lines with a width ranging from 500 nm to 10 nm. The phosphorus dopants are driven into silicon by rapid thermal annealing, forming dopant wires. Four-probe and Hall effect measurements are employed to characterize the dopant wires. The results show that the conductance is linear with the width for the wires, showing the success of the monolayer patterning process to nanoscale. To fabricate atomic wires made of one or a few lines of phosphorus atoms, we need to significantly shorten the thermal diffusion length and increase the dopant incorporation rate at the same time. Pulsed laser annealing may be a promising solution. The present work provides a promising pathway for mass fabrication of atomic wires in silicon that may find important applications in quantum computing.
关键词： atomic wires,semiconductors,nanoelectronics,Monolayer doping,self-assembled monolayers
更新于2025-09-12 10:27:22
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Optically Pumped Monolayer MoSe <sub/>2</sub> Excitonic Lasers from Whispering Gallery Mode Microcavities
摘要： Developing integrable, nanoscale, and low-energy-consumption lasers is a crucial step toward on-chip optical communications and computing technologies. The strong exciton-photon interaction emerged in monolayer transition metal dichalcogenides (TMDs) holds promise for engineering and integration. Herein we prepare the MoSe2/microsphere cavities excitonic lasers by placing SiO2 microspheres on top of monolayer MoSe2 film. By virtue of continuous wave exciting MoSe2/microsphere whispering-gallery-mode (WGM) cavities, we realize multiple excitonic WGM lasing in the emission wavelength range of ～750 nm to 875 nm at room temperature with tunable properties of free spectral range (FSR) and full width at half maximum (FWHM) by varying the microsphere size. Theoretical calculations based on finite element method (FEM) using COMSOL software were utilized to identify lasing modes and reveal the corresponding electric ?eld distribution. These findings help to deepen fundamental understanding of excitonic WGM lasing, and provide a promising research platform for integrable, scalable, and low-cost laser devices.
关键词： Whispering Gallery Mode Microcavities,Monolayer MoSe2,Optically Pumped,Excitonic Lasers
更新于2025-09-12 10:27:22
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Dimethylaniline functionalised pyrene fluorophores; dual colour pH switching in solution and self-assembled monolayers
摘要： A pyrene charge transfer fluorophore with three ionizable N,N-dimethylaniline moieties was explored as an interfacial pH switch. The parent carboxylate compound and the thiolated derivative were shown by spectroscopy combined with DFT calculation to be successively and reversibly protonated. Protonation leads to progressive decrease of intensity of the 550 nm centered N,N-dimethylaniline to pyrene charge transfer emission which on protonation of the third site, leads to extinction of this transition and evolution of an intense blue (450 nm) pyrene-centered emission. Concomitant loss of the charge transfer absorbance was observed and the changes are reversed on neutralization of pH. A self-assembled monolayer of the thiolated derivative was prepared on gold and found from voltammetry of ferricyanide/ferrocyanide probe to form close packed monolayers. The probe voltammetry, label-free electrochemical impedance spectroscopy of the film was monitored as a function of pH and progressive, but reversible protonation steps were reflected in decreasing film resistance. The Stokes shift of the probe prevents self-quenching so a broad, charge transfer fluorescence centered around 540 nm was recorded for the self-assembled monolayer where as per solution, progressive and reversible reduction in intensity was observed. The facile assembly, impedance and optical switching make these materials potentially interesting as on–off or two colour on–off–on fluorescence switches with potential applications in logic gates or in responsive surface applications.
关键词： DFT calculation,self-assembled monolayer,fluorescence,charge transfer,pH switch,pyrene
更新于2025-09-12 10:27:22