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- 实验方案
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Resolving Fine Electromechanical Structure of Collagen Fibrils via Sequential Excitation Piezoresponse Force Microscopy
摘要： Collagen is the main protein in extracellular matrix that is found in many connective tissues, and it exhibits piezoelectricity that is expected to correlate with its hierarchical microstructure. Resolving fine electromechanical structure of collagen, however, is challenging, due to its weak piezoresponse, rough topography, and microstructural hierarchy. Here we adopt the newly developed sequential excitation (SE) strategy in combination with piezoresponse force microscopy (PFM) to overcome these difficulties. It excites the local electromechanical response of collagen via a sequence of distinct frequencies, minimizing crosstalk with topography, followed by principal component analysis (PCA) to remove the background noise and simple harmonic oscillator (SHO) model for physical analysis and data reconstruction. These enable us to acquire high fidelity mappings of fine electromechanical response at the nanoscale that correlate with the gap and overlap domains of collagen fibrils, which show substantial improvement over conventional PFM techniques. It also embodies the spirit of big data atomic force microscopy (AFM) that can be readily extended into other applications with targeted data acquisition.
关键词： Principal component analysis,Sequential excitation,Simple harmonic oscillator model,Piezoresponse force microscopy,Collagen
更新于2025-09-19 17:15:36
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On the photo-activation of the S <sub/>0</sub> ?→?S <sub/>1</sub> transition in polyenes
摘要： The evidence provided in this work allows us to conclude that the electronic transition S0 → S1 either for the diphenylhexatriene molecule or for the diphenyloctatetraene molecule is dipole allowed and induced by one‐photon absorption. Consequently, the model to explain the photophysics of these polyenes does not need the existence of an underlying 21Ag excited electronic state, to the converse of what Hudson and Kohler proposed, that the transition S0 → S1 must be induced by two‐photon absorption.
关键词： two‐photon absorption,excitation spectra,photophysics of polyenes
更新于2025-09-19 17:15:36
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Nanostructured Al0.2Y1.8O3 Semiconductor Assisted Enhancement in PVOH Fortitude to
摘要： An appreciable enhancement in UV endurance of poly(vinyl alcohol) (PVOH) films has been achieved by using nanostructured Al0.2Y1.8O3 semiconductors. The effect of shorter wavelength UV radiations on physico-mechanical and opto-electronic behaviors were established by surface morphological, optical and mechanical characterizations. While, the enhancement in photo stabilities of PVOH/Al0.2Y1.8O3 nanocomposite films were accessed via optical and mechanical studies. The optical transmittance, fluorescence emission, tensile behaviors and contact angle behaviors of PVOH/Al0.2Y1.8O3 film remain almost unaltered upon UV irradiation, while there occurred detrimental changes in physico-mechanical and optical behaviors of pristine PVOH upon UV curing. The anti UV-ageing property of Al0.2Y1.8O3 reinforced PVOH NCs was achieved through deactivation of UV induced photo-oxidative deterioration through Al0.2Y1.8O3 nanofiller assisted energy drain in conjunction with photonic down conversion.
关键词： nanocomposites,PVOH,UV-ageing,photo-oxidation,photo-excitation
更新于2025-09-19 17:15:36
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Correlation functions with single-photon emitters under noisy resonant continuous excitation
摘要： To characterize the statistics and indistinguishability of a source, it is common to measure the correlation functions of the emitted field using various interferometers. Here, we present a theoretical framework for the computation of the correlation functions of a two-level system that is resonantly driven by a realistic noisy cw excitation laser. Analytic expressions of the first- and second-order autocorrelation functions are obtained where the various contributions of the noisy excitation source are correctly taken into account. We predict that, even in the low power regime, the noise source has a strong influence on the two-level system dynamics, which is not anticipated by simpler models. The characterization of photon indistinguishability in the pulsed excitation regime is usually done by measuring the value of the zero-delay intensity correlation obtained with a Hong-Ou-Mandel interferometer. We show that this figure is irrelevant in the cw excitation regime and we introduce the coalescence time window, a figure of merit based on a probabilistic interpretation of the notion of photon indistinguishability. We finally use the coalescence time window to quantify how noisy cw excitation influences photon indistinguishability.
关键词： Hong-Ou-Mandel interferometer,correlation functions,coalescence time window,noisy resonant continuous excitation,single-photon emitters
更新于2025-09-19 17:15:36
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Reduced-scaling approach for CIS and time-dependent DFT calculations using hybrid functionals
摘要： An approximation is presented which can efficiently decrease the computational expenses of configuration interaction singles (CIS) and time-dependent density functional theory (TDDFT) methods employing hybrid functionals. The approach is the adaptation of the local density fitting scheme developed for Hartree–Fock (HF) calculations for excited states and reduces the quartic scaling of the methods to cubic. It can also be applied to related methods, such as the time-dependent HF and Tamm–Dancoff approximation TDDFT approaches. Our benchmark calculations show that, for molecules of 50 to 100 atoms, average speedups of 2 to 4 can be achieved for CIS and TDDFT calculations at the expense of negligible errors in the calculated excitation energies and oscillator strengths, but for bigger systems or molecules of localized electronic structure significantly larger speedups can be gained. We also demonstrate that the approximation enables excited-state calculations on a single processor even for molecules of 1000 atoms using basis sets augmented with diffuse functions including more than 17000 atomic orbitals.
关键词： hybrid functionals,local density fitting,excitation energies,TDDFT,reduced scaling,CIS
更新于2025-09-19 17:15:36
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MgF2-Based Luminescing Ceramics
摘要： Results of investigation at 300 K of photo- and cathodoluminescence of the high-temperature optical ceramics synthesized for the first time based on MgF2 activated tungsten oxide are presented.
关键词： luminescence,tungsten,ceramics,magnesium fluoride,excitation spectra,annealing
更新于2025-09-19 17:15:36
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Studying of photo-excitation dynamics and photodetector based on MoSe2 nanosheet
摘要： The photo-excitation dynamics occurring in the nanosheet of MoSe2 have been studied by employing the transient absorption. We find that four types of dynamic behaviors participate in the relaxation of excited MoSe2 nanosheet by global fitting, which corresponds to the exciton-exciton interaction, exciton capture by trapping state, exciton dissociation and free charge movement. Since many free charge has generated after photo-excitation, the photo-detector based on MoSe2 nanosheet is fabricated and the period- and voltage-dependent photocurrent is further clarified. In addition, nanosecond transient photocurrent test probes the dynamics of carrier and confirms that illumination intensity would accelerate the lifetime of carrier recombination to 1 μs at high intensity and enhance the corresponding loss of carrier. Moreover, it is also found that the bias voltage would linearly facilitate the yield of free carriers in photo-detector and the lifetime of carrier recombination would decrease to 4 μs at 60 V. The final results could help people to further understand the photo-physical property of MoSe2 nanosheet and facilitate its application in the opto-electronic devices.
关键词： Photo-excitation dynamics,MoSe2 nanosheet,Transient absorption,Photodetector
更新于2025-09-19 17:13:59
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Highly indistinguishable single photons from incoherently excited quantum dots
摘要： Semiconductor quantum dots with dimensions exceeding the free-exciton Bohr radius are appealing because of their high oscillator strengths. While this property has received much attention in the context of cavity quantum electrodynamics, little is known about the degree of indistinguishability of single photons consecutively emitted by such dots and on the proper excitation schemes to achieve high indistinguishability. A prominent example is represented by GaAs quantum dots obtained by local droplet etching, which recently outperformed other systems as triggered sources of entangled photon pairs. On these dots, we compare different single-photon excitation mechanisms, and we find (i) poor indistinguishability for conventional excitation via excited states and (ii) photon indistinguishablities above 90% for both strictly resonant and for incoherent phonon-assisted excitation. Among the explored excitation schemes, optical phonon-assisted excitation allows straightforward laser rejection and is thus worth of further investigation and optimization for quantum dots embedded in high-brightness photonic structures.
关键词： quantum dots,indistinguishability,single-photon emission,GaAs,phonon-assisted excitation
更新于2025-09-19 17:13:59
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Extraordinarily Large Third-Order Optical Nonlinearity in Au Nanorods under Nanowatt Laser Excitation
摘要： Size and operating energy are two key parameters that constrain the integration capability of a nonlinear optical device. Here, we report a 60-nm thin film made of randomly distributed gold nanorods that demonstrates extraordinarily large third-order nonlinear optical absorption under an excitation power as low as 100 nanowatts. Where the effective nonlinear optical absorption (NLA) coefficient is calculated to be 8x109 cm/GW with the corresponding optical susceptibility (Imχ(3)) of 7.6x10-2 esu, which is 3-4 orders larger than that of other metallic nanostructures. The sign of the NLA could be controlled by changing the excitation wavelength or varying the pump power. The optical Kerr effect measurement also shows that the intrinsic χ(3) of our sample is quite large compared to other nanostructures. Our work eliminates the requirements of strong operation power and large physical size of nonlinear optical materials and offers new opportunities for plasmonic nanostructures in applications of on-chip nonlinear optical devices.
关键词： Nanowatt Laser Excitation,and Hybrid Materials,Optical,Plasmonics,Magnetic,Au Nanorods,Third-Order Optical Nonlinearity
更新于2025-09-19 17:13:59
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Hermitian second-order methods for excited electronic states: Unitary coupled cluster in comparison with algebraica??diagrammatic construction schemes
摘要： Employing an intermediate state representation (ISR) approach, Hermitian second-order methods for the calculation of electronic excitation energies are presented and compared in detail. These comprise the algebraic–diagrammatic construction scheme for the polarization propagator, a hybrid second-order ISR scheme based on traditional coupled-cluster theory as well as two similar approaches based on a unitary coupled-cluster (UCC) ansatz. Although in a strict perturbation-theoretical framework all prove to be identical, differences emerge when the corresponding converged cluster amplitudes are used and depending on how the similarity-transformed UCC Hamiltonian is evaluated. The resulting excitation energies, however, do not significantly differ for systems well described by means of perturbation theory.
关键词： unitary coupled-cluster,electronic excitation energies,intermediate state representation,perturbation theory,Hermitian second-order methods,algebraic–diagrammatic construction scheme
更新于2025-09-19 17:13:59