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- 摘要
- 关键词
- 实验方案
- 产品
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Ultrafast dynamics of solvated electrons at anatase TiO<sub>2</sub>/H<sub>2</sub>O interface
摘要： Solvated electrons are known to be the lowest energy charge transfer pathways at oxide/aqueous interface and the understanding of the electron transfer dynamics at the interface is fundamental for photochemical and photocatalytic processes. Taking anatase TiO2/H2O interface as a prototypical system, we perform time-dependent ab initio nonadiabatic molecular dynamics (NAMD) calculations to study the charge transfer dynamics of solvated electrons. For the static electronic properties, we find that the dangling H atoms can stabilize solvated electrons. A solvated electron band can be formed with one monolayer H2O adsorption. The energies of the solvated electron band minimum decrease when H2O adsorbs dissociatively. Moreover, the surface oxygen vacancies are also helpful for stabilizing the solvated electron band. For the dynamics behaviour, we find that the ultrafast charge transfer from solvated electron band minimum to anatase TiO2(101) surface at 100 K is mainly contributed by nonadiabatic mechanism. Comparing with rutile TiO2(110) surface, the lifetime of solvated electron on anatase TiO2 (101) surface is longer, suggesting a better photocatalytic properties. Our results provide essential insights into the understanding of the charge transfer dynamics and the possible photocatalytic mechanism at oxide/aqueous interface.
关键词： nonadiabatic molecular dynamics,solvated electron,oxide/aqueous interface
更新于2025-09-23 15:23:52
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Wetting Transition from the Cassie–Baxter State to the Wenzel State on Regularly Nanostructured Surfaces Induced by an Electric Field
摘要： When droplets are placed on hydrophobic textured surfaces, different wetting state Cassie-Baxter (CB) state or Wenzel (W) state may occur depending on materials and structures of surfaces, types and sizes of droplets, thermal fluctuations, and external stimuli. The wetting transition from the CB to the W state and the opposite process have attracted a great deal of attention due to their primary importance for designing and fabricating textured surfaces. In this work, molecular dynamics (MD) simulations are employed to understand the mechanism behind the CB-to-W transition for a nanoscale water film placed on a surface decorated with a single nanogroove when an external electric field is applied. The free energy variation during the transition process is computed on the basis of the restrained MD simulations. Water intrusion into the groove is observed by simulation snapshots, which provides a direct evidence for the electric-field-induced CB-to-W transition. In the previous experiments, however, only a sharp reduction in the apparent contact angle is employed to judge whether the transition takes place. The free energy curves reveal that there are two energy barriers separating the CB and W states (?E1) as well as separating the W and CB states (?E2). Owing to the presence of ?E1, although the CB state has a higher free energy than the W state, it cannot spontaneously convert to the W state. When the external energy input exceeds ?E1, the CB-to-W transition can be triggered, otherwise the transition will stop, and the water film will return to the CB state. Moreover, it is found that the maximum of free energy always occurs after the film touches the groove bottom. Thus, the requirement of the film touching the groove bottom is responsible for the presence of the energy barrier ?E1. Finally, the dependences of the two energy barriers on the electric field strength, groove aspect ratio, and intrinsic contact angle of the groove are also discussed.
关键词： Cassie-Baxter state,wetting transition,Wenzel state,energy barrier,free energy,molecular dynamics simulations.
更新于2025-09-23 15:23:52
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Structure/Function/Dynamics of Photosystem II Plastoquinone Binding Sites
摘要： Photosystem II (PSII) continuously attracts the attention of researchers aiming to unravel the riddle of its functioning and efficiency fundamental for all life on Earth. Besides, an increasing number of biotechnological applications have been envisaged exploiting and mimicking the unique properties of this macromolecular pigment-protein complex. The PSII organization and working principles have inspired the design of electrochemical water splitting schemes and charge separating triads in energy storage systems as well as biochips and sensors for environmental, agricultural and industrial screening of toxic compounds. An intriguing opportunity is the development of sensor devices, exploiting native or manipulated PSII complexes or ad hoc synthesized polypeptides mimicking the PSII reaction centre proteins as biosensing elements. This review offers a concise overview of the recent improvements in the understanding of structure and function of PSII donor side, with focus on the interactions of the plastoquinone cofactors with the surrounding environment and operational features. Furthermore, studies focused on photosynthetic proteins structure/function/dynamics and computational analyses aimed at rational design of high-quality bio-recognition elements in biosensor devices are discussed.
关键词： plastoquinone binding site,molecular dynamics simulations,plastoquinone,Molecular docking,protein dynamics,Photosystem II
更新于2025-09-23 15:22:29
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Numerical analysis of single-point spectroscopy curves used in photo-carrier dynamics measurements by Kelvin probe force microscopy under frequency-modulated excitation
摘要： In recent years, the investigation of the complex interplay between the nanostructure and photo-transport mechanisms has become of crucial importance for the development of many emerging photovoltaic technologies. In this context, Kelvin probe force microscopy under frequency-modulated excitation has emerged as a useful technique for probing photo-carrier dynamics and gaining access to carrier lifetime at the nanoscale in a wide range of photovoltaic materials. However, some aspects about the data interpretation of techniques based on this approach are still the subject of debate, for example, the plausible presence of capacitance artifacts. Special attention shall also be given to the mathematical model used in the data-fitting process as it constitutes a determining aspect in the calculation of time constants. Here, we propose and demonstrate an automatic numerical simulation routine that enables to predict the behavior of spectroscopy curves of the average surface photovoltage as a function of a frequency-modulated excitation source in photovoltaic materials, enabling to compare simulations and experimental results. We describe the general aspects of this simulation routine and we compare it against experimental results previously obtained using single-point Kelvin probe force microscopy under frequency-modulated excitation over a silicon nanocrystal solar cell, as well as against results obtained by intensity-modulated scanning Kelvin probe microscopy over a polymer/fullerene bulk heterojunction device. Moreover, we show how this simulation routine can complement experimental results as additional information about the photo-carrier dynamics of the sample can be gained via the numerical analysis.
关键词： Kelvin probe force microscopy,nanostructured photovoltaics,numerical simulations,photo-carrier dynamics,carrier dynamics,carrier recombination,carrier lifetime
更新于2025-09-23 15:22:29
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Composite modeling and parameter identification of broad bandwidth hysteretic dynamics in piezoelectric fast steering platform
摘要： Over a broadband range of frequencies, it is difficult to develop precise model of piezoelectric fast steering platforms (FSPs) due to the complex hysteretic and dynamic behaviors. This paper thus presents one approach of composite modeling and parameter identification by employing a composite hysteretic model. The proposed composite model consists of the Bouc-Wen hysteresis, electro-mechanical dynamics, creep dynamics and the high frequency mirror dynamics. Physical meanings can be found in the linear component which is beneficial to controller design and other further developments using the proposed model. A step-by-step approach is proposed to identify the composite hysteretic model. Finally, the FSP experiment is provided to validate the effectiveness of the proposed modeling and parameter identification approaches.
关键词： Electro-optical system,Creep effect,Hysteretic dynamics,Fast steering platform,Electro-mechanical dynamics,Piezoelectric actuator
更新于2025-09-23 15:22:29
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[Institution of Engineering and Technology 7th International Conference on Imaging for Crime Detection and Prevention (ICDP 2016) - Madrid, Spain (23-25 Nov. 2016)] 7th International Conference on Imaging for Crime Detection and Prevention (ICDP 2016) - Using keystroke and mouse dynamics for user identification in the online collaborative game League of Legends
摘要： The popularity of computer games has grown exponentially in the last few years. It is not uncommon to find players of online games who can dedicate their whole lives in order to became the best in their favourite game. The best players normally become celebrities and can even get sponsored to compete in game tourneys. It is accepted that each player should follow the his/her own path to increase level, so the experience reflected in the gamer's level is how proficient he/she is in the game. However, this increased popularity has also created a desire on some players to cheat (by paying others more experienced players to play for them) for the progress in the game and thus to improve their status. The companies that develop such games have very strict punishment for such breaking of the rules, but, it can be very difficult to identify when this 'account sharing' happens. This paper focus on the collection and analysis of a new online game database for continuous mouse dynamics and keystroke dynamics authentication in order to identify whether who is playing is really the account holder. Our very first results point to very interesting possibilities for security biometric-based applications in this new game analysis area.
关键词： Mouse dynamics,League of Legends,User identification,Online game,Keystroke dynamics
更新于2025-09-23 15:22:29
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Photo-induced lattice contraction in layered materials
摘要： Structural and electronic changes induced by optical excitation is a promising technique for functionalization of 2D crystals. Characterizing the effect of excited electronic states on the in-plane covalent bonding network as well as the relatively weaker out-of-plane dispersion interactions is necessary to tune photo-response in these highly anisotropic crystal structures. In-plane atom dynamics was measured using pump-probe experiments and characterized using ab initio simulations, but the effect of electronic excitation on weak out-of-plane van der Waals bonds is less well-studied. We use non-adiabatic quantum molecular dynamics to investigate atomic motion in photoexcited MoS2 bilayers. We observe a strong athermal reduction in the lattice parameter along the out-of-plane direction within 100 fs after electronic excitation, resulting from redistribution of electrons to excited states that have lesser anti-bonding character between layers. This non-trivial behavior of weakly bonded interactions during photoexcitation could have potential applications for modulating properties in materials systems containing non-covalent interactions like layered materials and polymers.
关键词： quantum molecular dynamics,layered materials,MoS2,photo-dynamics,van der Waals
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - A Doppler Centroid Estimator for Synthetic Aperture Radar Based on Phase Center Point Tracking
摘要： Heterogeneity is an important feature of multiagent systems. This paper addresses the consensus problem of heterogeneous multiagent systems composed of first-integrator and double-integrator agents. The dynamics of each agent switches between continuous-time and discrete-time dynamics. By using the graph theory and nonnegative matrix theory, we derive that the system can achieve consensus if and only if the fixed interaction topology has a directed spanning tree. For switching topologies, we get that the system can reach consensus if each interaction topology has a directed spanning tree. Simulation examples are provided to demonstrate the effectiveness of our theoretical results.
关键词： switching dynamics,nonnegative matrix theory,consensus,heterogeneous multiagent systems,graph theory
更新于2025-09-23 15:22:29
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Efficient separation of photo-generated charges in a ferroelectric molecular wire: nonadiabatic dynamics study on 3,5-dicyano-1,7-dimethylopyrrolo[3,2-f]indole trimer
摘要： In this work we propose and verify computationally a novel idea of spontaneous separation of charges photo-generated in a highly polar molecular 'wire'. The nuclear and electronic structure of the investigated system, so as the evolution of charge carriers, are characterized at the semi-empirical OM2/MRCI level of theory. Results point to the conclusion that 90% of optically prepared excitons break into charge carriers (holes and electrons) localized on the opposite monomeric units of the trimer on the time scale of 30 fs. Our findings can be helpful in design of photoactive and conducting components for molecular photovoltaic applications.
关键词： ferroelectric polymers,nonadiabatic molecular dynamics,molecular photovoltaics,photo-generated charge separation,molecular wire
更新于2025-09-23 15:22:29
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Dual frequency-comb spectroscopy of chromophores in condensed phases
摘要： Femtosecond time-resolved spectroscopy and frequency-comb spectroscopy have been individually developed to achieve better time and frequency resolutions, respectively. The two spectroscopic techniques have been developed for different systems, even though they use mode-locked laser in common. Recently, there was an interesting merge of the two techniques into a dual frequency-comb (DFC) spectroscopy, resulting in a new femtosecond spectroscopy with simple instrumentation and high data acquisition speed compared to conventional femtosecond spectroscopic techniques. By slightly detuning the repetition rates of two phase-locked frequency-comb lasers, both automatic time-delay scanning and parallel data recording with single point detectors are possible. Thus, we anticipate that the DFC spectroscopy would allow one to expand the application limits of the conventional femtosecond spectroscopic methods. In this Perspective article, we provide reviews of linear and nonlinear DFC spectroscopy theory and applications with a perspective on the development of coherent multidimensional frequency-comb spectroscopy.
关键词： nonlinear spectroscopy,optical frequency-comb,time-resolved spectroscopy,coherent two-dimensional spectroscopy,solvation dynamics,dual comb spectroscopy
更新于2025-09-23 15:22:29