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- 实验方案
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Temporally Resolving Synchronous Degenerate and Nondegenerate Two-Photon Absorption in 2D Semiconducting Monolayers
摘要： Degenerate and nondegenerate two-photon absorption (TPA) in WS2 and MoSe2 monolayers are synchronously induced and temporally resolved by femtosecond laser pump-probe. Di?erential transmission signals in the ?rst 500 fs consist of negative and positive components, that originate from direct probe depletion via nondegenerate TPA and carrier accumulation via degenerate TPA, respectively. Temporal cross-correlation of pump and probe pulses allows us to fully decouple the ultrafast nondegenerate and degenerate TPA signals. Subsequently, degenerate and nondegenerate TPA coe?cients are calculated as a function of pump irradiance. Under nonresonant pumping, 100 ± 10 and 250 ± 25 cm GW?1 are obtained for degenerate and nondegenerate TPA coe?cients of monolayer WS2, respectively, which both present linearly decreasing trends as increasing pump irradiances. However, under resonant pumping of 2 p excitonic states in monolayer MoSe2, degenerate TPA coe?cients exponentially decrease from 800 to 80 cm GW?1 as increasing pump irradiances, due to the interplay between band-renormalization and band-?lling e?ects, while nondegenerate TPA coe?cient is about 650 ± 50 cm GW?1. For comparison, a trilayer MoSe2 is also investigated. These results set a foundation for precisely measuring TPA coe?cients and actively controlling nonlinear excitonic dynamics via TPA in 2D semiconducting monolayers.
关键词： 2D monolayer,transition metal dichalcogenide,femtosecond laser pump-probe,nondegenerate two-photon absorption,degenerate two-photon absorption
更新于2025-09-04 15:30:14
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Detuning-induced stimulated Raman adiabatic passage in two-level systems with permanent dipole moments
摘要： The detuning-induced stimulated Raman adiabatic passage (D-STIRAP) in two-level systems with permanent dipole moments (PDMs) is investigated. Based on a transformed Schr?dinger equation, we discuss the coherence generation under the one- and two-photon excitations, respectively. In the one-photon excitation, our analysis shows that the envelope of the pump pulse gets modulated in presence of the PDMs. The modulation becomes stronger while the difference between the PDMs of the two levels becomes larger. Gradually, the adiabatic process of the D-STIRAP fails to complete and the robustness of the technique disappears. Therefore, parameters have to be chosen with care if maximum coherence is desired in systems with large or giant difference between the PDMs. Similar results can also be found in the two-photon excitation, although the influence of the PDMs on the D-STIRAP seems weaker compared with that in the one-photon excitation case. Finally, we point out that the negative role of the PDMs can be effectively avoided by simply choosing longer pulses instead and the D-STIRAP can be safely applied in two-level systems with PDMs.
关键词： D-STIRAP,one-photon excitation,two-level systems,coherence generation,two-photon excitation,permanent dipole moments
更新于2025-09-04 15:30:14
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Rotational Efficiency of Photo-Driven Archimedes Screws for Micropumps
摘要： In this study, we characterized the rotational efficiency of the photo-driven Archimedes screw. The micron-sized Archimedes screws were fabricated using the two-photon polymerization technique. Free-floating screws trapped by optical tweezers align in the laser irradiation direction and rotate spontaneously. The influences of the screw pitch and the number of screw blades have been investigated in our previous studies. In this paper, the blade thickness and the central rod of the screw were further investigated. The experimental results indicate that the blade thickness contributes to rotational stability, but not to rotational speed, and that the central rod stabilizes the rotating screw but is not conducive to rotational speed. Finally, the effect of the numerical aperture (NA) of the optical tweezers was investigated through a demonstration. The NA is inversely proportional to the rotational speed.
关键词： two-photon polymerization,micropump,optical torque,Archimedes screw,optical tweezers
更新于2025-09-04 15:30:14
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AIEgen Nanoparticles of Arylamino Fumaronitrile Derivative with High Near-infrared emission for Two-photon Imaging and in vivo Cell Tracking
摘要： Developing of two-photon materials for live-cell imaging and in vivo analysis in-deep have been received great attention, and it is still urgent so that such microscopy technique could be promoted and advanced into new progress using the powerful probs. Herein, a new arylamino fumaronitrile derivative NPAPF was synthesized and transferred as aggregation-induced emission luminogen (AIEgen) fluorescent nanoparticles (AF-NPs) via assembly technique. This AF-NPs exhibited two-photon absorption cross-section at 2.6×106 GM with 19.5% of fluorescence quantum yield. Moreover, utilizing the great potential of AF-NPs, two-photon imaging of live cells with good cytocompatibility is realized upon two-photon microscopy. By in vivo long-term tracing studies of mesenchymal stem cells, we demonstrated the tremendous advantage of AF-NPs tracer in monitoring the stem cells transplant. Therefore, our unique AF-NPs provided an efficient two-photon-absorbing probe for investigating biological mechanism and behavior, and also opened a new avenue for spatiotemporal visualization of transplanted stem cells.
关键词： organic nanoparticles,aggregation-induced emission,two-photon,in vivo imaging,mesenchymal stem cell
更新于2025-09-04 15:30:14
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A two-photon excited O2-Evolving Nanocomposite for Efficient Photodynamic Therapy against hypoxic tumor
摘要： This paper reported on a two-photon excited nanocomposite FCRH to overcome tumor hypoxia for enhanced photodynamic therapy (PDT). Through modified by ruthenium (Ⅱ) complex (Ru(bpy)3 2+) and hyperbranched conjugated copolymer with poly (ethylene glycol) arms (HOP), the water-splitting mediated O2 generation from iron-doped carbon nitride (Fe-C3N4) can be triggered via two-photon irradiation for the first time. While exposured to two-photon laser, Ru(bpy)3 2+ was activated to generate singlet oxygen (1O2) and Fe-C3N4 was triggered to split water for oxygen supply in the mean time. Owing to the injection of photoinduced electrons from excited Ru(bpy)3 2+ to Fe-C3N4, O2 generated by Fe-C3N4 was significantly accelerated. After accumulation of the nanocomposite by enhanced permeability and retention (EPR) effect, FCRH was demonstrated to alleviate the tumorous hypoxia and consequently enhance the antitumor efficacy of PDT. Furthermore, tumor metabolism evaluations explained the capability of the nanocomposite in reducing intratumoral hypoxia. Our results provide a new diagram for ameliorating the hypoxic tumor microenvironment and accelerating 1O2 generation under two-photon excitation, which will find great potential for spatiotemporally controlled tumor treatment in vivo.
关键词： two-photon,water splitting,oxygen generation,tumor hypoxia,photodynamic therapy
更新于2025-09-04 15:30:14
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A Two-Photon Ratiometric Probe for Hydrogen Polysulfide (H2Sn): Increase in Mitochondrial H2Sn Production in a Parkinson’s Disease Model
摘要： Hydrogen polysulfide (H2Sn, n>1), which is primarily generated during the crosstalk between H2S and reactive species (ROS and RNS), is receiving increasing attention in biochemical research. H2Sn is mostly generated in the mitochondria, and abnormal mitochondrial function and oxidative stress are directly related to many disorders including Parkinson's disease (PD). We now report a two-photon fluorescent probe (SPS-M1) for in situ detection of H2Sn and its application to a PD model to account the H2Sn levels. The probe exhibited selective and fast response to H2Sn along with a marked blue-to-green color change. SPS-M1 is sensitive enough to quantitative detection of endogenous H2Sn content in mitochondria using two-photon microscopy (TPM). Ratiometric TPM imaging of live neurons and brain slices using SPS-M1 revealed that H2Sn production is increased to a greater extent in the A53T α-synuclein (α-syn) overexpressing model than in the wild-type control. These findings suggest that the interactions of H2S and the increased ROS caused by α-syn overexpression may generate more H2Sn. By employing our recently published TP probe for mitochondrial H2S, we also found the relationship between the H2Sn and H2S; increased H2Sn and decreased H2S levels, indicating that H2S and H2Sn may play a significant role in the pathogenesis of PD. This result may be useful to biomedical studies, including PD.
关键词： two-photon microscopy,fluorescent probe,Parkinson’s disease,Hydrogen polysulfide,mitochondria
更新于2025-09-04 15:30:14
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Hybridization of an unoccupied molecular orbital with an image potential state at a lead phthalocyanine/graphite interface
摘要： The interaction of a molecular orbital with a surface state is important to understand the spatial distribution of the wave function at the molecule/substrate interface. In this study, we focus on hybridization of an unoccupied state of lead phthalocyanine (PbPc) with the image potential state (IPS) on a graphite surface. The hybridization modifies the energy-momentum dispersions of the IPS on PbPc films as observed by angle-resolved two-photon photoemission. On the PbPc 1 monolayer film, the IPS band forms a band gap and back-folding appears at the first Brillouin zone boundary due to the periodic potential by the adsorbate lattice. The modification of the dispersion is accompanied by the intensity enhancement of the IPS. We attributed the origin of the modified dispersion and intensity enhancement to a hybridization of the IPS with a molecule-derived unoccupied level. From the photon energy-dependent measurement on multilayer films, we have found the diffuse unoccupied molecular level in the vicinity of the IPS. The tail part of the IPS wave function in the substrate is enhanced by the hybridization with the unoccupied state, and thus strengthens the transition from the occupied substrate band to the hybridized IPS.
关键词： organic ultrathin films,image potential states,two-photon photoemission spectroscopy,unoccupied states,hybridization
更新于2025-09-04 15:30:14
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Bismuth Ferrite Second Harmonic Nanoparticles for Pulmonary Macrophage Tracking
摘要： Recently, second harmonic generation (SHG) nanomaterials have been generated that are efficiently employed in the classical (NIR) and extended (NIR-II) near infrared windows using a multiphoton microscope. The aim was to test bismuth ferrite harmonic nanoparticles (BFO-HNPs) for their ability to monitor pulmonary macrophages in mice. BFO-loaded MH-S macrophages are given intratracheally to healthy mice or BFO-HNPs are intranasally instilled in mice with allergic airway inflammation and lung sections of up to 100 μM are prepared. Using a two-photon-laser scanning microscope, it is shown that bright BFO-HNPs signals are detected from superficially localized cells as well as from deep within the lung tissue. BFO-HNPs are identified with an excellent signal-to-noise ratio and virtually no background signal. The SHG from the nanocrystals can be distinguished from the endogenous collagen–derived SHG around the blood vessels and bronchial structures. BFO-HNPs are primarily taken up by M2 alveolar macrophages in vivo. This SHG imaging approach provides novel information about the interaction of macrophages with cells and the extracellular matrix in lung disease as it is capable of visualizing and tracking NP-loaded cells at high resolution in thick tissues with minimal background fluorescence.
关键词： two-photon-laser scanning microscopy,macrophages,third harmonic generation,nanoparticles,second harmonic generation
更新于2025-09-04 15:30:14
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A stage-scanning two-photon microscope equipped with a temporal and a spatial pulse shaper: Enhance fluorescence signal by phase shaping
摘要： Here, we present a stage-scanning two-photon microscope (2PM) equipped with a temporal pulse shaper and a spatial light modulator enabling full control over spectral and spatial phases of the exciting laser pulse. We demonstrate the capability of correcting wavefronts and temporal pulse distortions without cross-dependencies induced by optical elements at the same time enhancing the fluorescence signal. We implemented phase resolved interferometric spectral modulation for temporal pulse shaping and the iterative feedback adaptive compensation technique for spatial pulse modulation as iterative techniques. Sample distortions were simulated by cover glass plates in the optical path and by chirping the exciting laser pulses. Optimization of the spectral and spatial phases results in a signal increase of 30% and nearly complete recovery of the losses. Applying a measured spatial compensation phase within a real leaf sample shows the enhancement in contrast due to wavefront shaping with local fluorescence increase up to 75%. The setup allows full independent control over spatial and spectral phases keeping or improving the spatial resolution of our microscope and provides the optimal tool for sensitive non-linear and coherent control microscopy.
关键词： two-photon microscopy,wavefront shaping,spatial light modulator,fluorescence signal enhancement,temporal pulse shaping
更新于2025-09-04 15:30:14
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Desenvolvimento de um obturador de feixe óptico utilizando um disco rígido de computador
摘要： This work demonstrates the development of an optical shutter from a computer hard disk. The electrical current control of the device is made by pulse width modulation, a technique that allows varying current/voltage levels by adjusting the pulse width of a digital signal. This control is made in order to minimize the power dissipated into the device, thus raising its lifetime. The main unit of the control circuit is Arduino Uno, a low cost and ease of programming microcontroller board, extensively used as a platform for electronic prototyping. As an example, we present the use of an optical shutter developed in a microfabrication setup via two-photon polymerization, in which it plays an important role.
关键词： Optical shutter,Arduino Uno,pulse width modulation,two-photon polymerization
更新于2025-09-04 15:30:14