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Correlation between Near-Field Enhancement and Dephasing Time in Plasmonic Dimers
摘要： Near-field enhancement and dephasing time play critical roles in several applications of localized surface plasmon resonance. Here, using an example gold dimer system, we reveal the correlation between the near-field enhancement and dephasing time via time-resolved photoemission electron microscopy. Compared with isolated particles, dimers with small gap sizes show stronger near-field enhancement and shorter dephasing times. These results are well reproduced by numerical simulations and further explained by a coupled dipole approximation model. The roles of near- and far-field coupling and plasmon localization in balancing near-field enhancement and dephasing time are also unveiled.
关键词： dephasing time,time-resolved photoemission electron microscopy,near-field enhancement,plasmonic dimers,coupled dipole approximation model
更新于2025-09-23 15:19:57
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Light-Induced Coalescence of Plasmonic Dimers and Clusters
摘要： The properties of nanoplasmonic structures depend strongly on their geometry, creating the need for high-precision control and characterization. Here, by exploiting the low activation energy of gold atoms on nanoparticle surfaces, we show how laser irradiation re-shapes nanoparticle dimers. Time-course dark-field micro-spectroscopy allows this process to be studied in detail for individual nanostructures. Three regimes are identified: facet growth, formation of a conductive bridge between particles, and bridge growth. Electromagnetic simulations confirm the growth dynamics and allow measurement of bridge diameter, found to be highly reproducible and also self-limiting. Correlations in spectral resonances for the initial and final states give insights into the energy barriers for bridge growth. Dark-field microscopy shows that coalescence of multiple gaps in nanoparticle clusters can be digitally triggered, with each gap closing after discrete increases in irradiation power. Such control is important for light-induced nanowire formation or trimming of electronic and optoelectronic devices.
关键词： nanoparticle coalescence,gold nanoparticles,optical spectroscopy,plasmonics,sintering,nanoparticle dimers
更新于2025-09-23 15:19:57
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Coherent Exciton Dynamics in Ensembles of Size-Dispersed CdSe Quantum Dot Dimers Probed via Ultrafast Spectroscopy: A Quantum Computational Study
摘要： Interdot coherent excitonic dynamics in nanometric colloidal CdSe quantum dots (QD) dimers lead to interdot charge migration and energy transfer. We show by electronic quantum dynamical simulations that the interdot coherent response to ultrashort fs laser pulses can be characterized by pump-probe transient absorption spectroscopy in spite of the inevitable inherent size dispersion of colloidal QDs. The latter, leading to a broadening of the excitonic bands, induce accidental resonances that actually increase the efficiency of the interdot coupling. The optical electronic response is computed by solving the time-dependent Schrodinger equation including the interaction with the oscillating electric field of the pulses for an ensemble of dimers that differ by their size. The excitonic Hamiltonian of each dimer is parameterized by the QD size and interdot distance, using an effective mass approximation. Local and charge transfer excitons are included in the dimer basis set. By tailoring the QD size, the excitonic bands can be tuned to overlap and thus favor interdot coupling. Computed pump-probe transient absorption maps averaged over the ensemble show that the coherence of excitons in QD dimers that lead to interdot charge migration can survive size disorder and could be observed in fs pump-probe, four-wave mixing, or covariance spectroscopy.
关键词： coherent electronic dynamics,pump-probe transient absorption spectroscopy,CdSe quantum dots dimers,exciton dynamics,size dispersion effects
更新于2025-09-23 15:19:57
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Effects of near-field electromagnetic coupling in dimers of nanoparticles with a silver core and a J-aggregate dye shell
摘要： We report a theoretical study of the plasmon – exciton coupling effect on the absorption spectra of pairs of closely spaced double-layer hybrid nanoparticles consisting of a metallic core and a J-aggregate dye shell. The effect of frequency conversion of plasmonic lines due to the near-field interaction between plasmons and Frenkel excitons of the organic shell is demonstrated. The effect leads to the appearance of additional spectral lines in the long-wavelength part of the spectrum of the system of hybrid particles. The shapes and the relative intensities of the additional lines exactly reproduce the specific features of the original spectrum of plasmonic absorption bands in uncoated metallic nanoparticles. The discovered phenomenon can be used to design new types of high-sensitivity nanosensors, based on plasmon – exciton effects and principles of near-field optics.
关键词： near-field electromagnetic coupling,nanophotonics,Frenkel excitons,dimers of metalorganic nanoparticles,plasmon – exciton interaction,molecular J-aggregates,localised plasmons,absorption spectra
更新于2025-09-19 17:15:36
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Zr <sub/>4</sub> -Substituted polyoxometalate dimers decorated by <scp>d</scp> -tartaric acid/glycolic acid: syntheses, structures and optical/electrochemical properties
摘要： In this article, two new tetra-Zr(IV)-substituted sandwich-type Keggin polyoxometalates functionalized by chiral D-tartaric acid and glycolic acid, K2H10[Zr4(H2O)2(μ-OH)(μ3-O)2(D-tartH)(GeW10O37)2]·27H2O (1, D-tartH4 = D-tartaric acid) and K2H10[Zr4(H2O)2(μ3-O)2(gly)2(GeW10O37)2]·32H2O (2, glyH2 = glycolic acid), have been synthesized under hydrothermal conditions and characterized by FT-IR spectra, elemental analysis, single-crystal X-ray structure analysis, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), ultraviolet-visible absorption spectroscopy (UV-vis) and cyclic voltammetry (CV). The structure analysis reveals that both 1 and 2 contain a [Zr4(H2O)2(μ3-O)2(GeW10O37)2] cluster. UV-vis spectra indicate that both compounds are a wide-gap semiconductor. In addition, compound 1 is a chiral Zr(IV)-substituted sandwich-type Keggin cluster because the D-tartH ligand is chiral and the Flack divisor of 1 is 0.00, showing non-linear optical properties. The cyclic voltammograms indicate that compounds 1 and 2 have good electrocatalytic activity in the reduction of H2O2.
关键词： Zr4-Substituted polyoxometalate dimers,optical properties,electrochemical properties,structures,syntheses,D-tartaric acid,glycolic acid
更新于2025-09-19 17:15:36
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Ligand-Assisted Reconstruction of Colloidal Quantum Dots Decreases Trap State Density
摘要： Increasing the power conversion efficiency (PCE) of colloidal quantum dot (CQD) solar cells has relied on improving the passivation of CQD surfaces, enhancing CQD coupling and charge transport, and advancing device architecture. The presence of hydroxyl groups on the nanoparticle surface, as well as dimers—fusion between CQDs—has been found to be the major source of trap states, detrimental to optoelectronic properties and device performance. Here, we introduce a CQD reconstruction step that decreases surface hydroxyl groups and dimers simultaneously. We explored the dynamic interaction of charge carriers between band-edge states and trap states in CQDs using time-resolved spectroscopy, showing that trap to ground-state recombination occurs mainly from surface defects in coupled CQD solids passivated using simple metal halides. Using CQD reconstruction, we demonstrate a 60% reduction in trap density and a 25% improvement in charge diffusion length. These translate into a PCE of 12.5% compared to 10.9% for control CQDs.
关键词： trap states,dimers,surface defects,photovoltaics,Quantum dots
更新于2025-09-19 17:13:59
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Enabling highly efficient photocatalytic hydrogen generation and organics degradation <i>via</i> a perovskite solar cell-assisted semiconducting nanocomposite photoanode
摘要： The halogenase gene spmH was putatively involved in the biosynthesis of spiroindimicins/indimicins (SPMs/IDMs), a group of chlorinated tryptophan dimers (TDs) from deep-sea-derived Streptomyces sp. SCSIO 03032. Inactivation of spmH led to six deschloro-analogues of TDs, including four new compounds SPMs G (1) and H (2), and IDMs F (3) and G (4). The structures and absolute configurations of 1–4 were unambiguously determined by the combination of extensive spectroscopic analysis, single-crystal X-ray diffraction and quantum chemical ECD calculations. Compounds 1 and 2 exhibited moderate cytotoxic activities against four cancer cell lines. Additionally, SpmH was biochemically characterized in vitro as an L-tryptophan 5-halogenase.
关键词： L-tryptophan 5-halogenase,biosynthesis,tryptophan dimers,cytotoxic activities,halogenase
更新于2025-09-11 14:15:04
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Imaging of Receptor Dimers in Zebrafish and Living Cells via Aptamer Recognition and Proximity-induced Hybridization Chain Reaction
摘要： On cell membrane surfaces, receptor protein dimers play a fundamental role in many signaling pathways, which are crucial for normal biological processes and cancer development. Efficient and sensitive analysis of receptor dimers in the native environment is highly desirable. Herein, we present a strategy for amplified imaging of receptor dimers in zebrafish and living cells, which relies on aptamer recognition and proximity-induced hybridization chain reaction. Taking advantages of specific aptamer recognition and enzyme-free signal amplification, this strategy is successfully applied to amplified visualize c-Met receptor dimers in the HGF-independent or -dependent manner. Therefore, the developed imaging strategy paves the way for further investigation of protein dimerization or oligomerization state of cell surface receptors and corresponding activation processes in zebrafish and living cells.
关键词： aptamer recognition,zebrafish,living cells,receptor dimers,hybridization chain reaction
更新于2025-09-10 09:29:36
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Reactive optical matter: light-induced motility in electrodynamically asymmetric nanoscale scatterers
摘要： From Newton’s third law, which is known as the principle of actio et reactio, we expect the forces between interacting particles to be equal and opposite for closed systems. Otherwise, “nonreciprocal” forces can arise. This has been shown theoretically in the interaction between dissimilar optically trapped particles that are mediated by an external field. As a result, despite the incident external field not having a transverse component of momentum, the particle pair experiences a force in a direction that is transverse to the light propagation direction. In this letter, we directly measure the net nonreciprocal forces in electrodynamically interacting asymmetric nanoparticle dimers and nanoparticle structures that are illuminated by plane waves and confined to pseudo one-dimensional geometries. We show via electrodynamic theory and simulations that interparticle interactions cause asymmetric scattering from heterodimers. Therefore, forces are actually a consequence of momentum conservation. Our study demonstrates that asymmetric scatterers exhibit directed motion due to the breakdown of mirror symmetry in their electrodynamic interactions with external fields.
关键词： momentum conservation,nonreciprocal forces,optical binding,electrodynamic interactions,nanoparticle dimers
更新于2025-09-09 09:28:46
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Breakdown of the Spectator Concept in Low-Electron-Energy Resonant Decay Processes
摘要： We suggest that low-energy electrons, released by resonant decay processes, experience substantial scattering on the electron density of excited electrons, which remain a spectator during the decay. As a result, the angular emission distribution is altered significantly. This effect is expected to be a common feature of low-energy secondary electron emission. In this Letter, we exemplify our idea by examining the spectator resonant interatomic Coulombic decay of Ne dimers. Our theoretical predictions are confirmed by a corresponding coincidence experiment.
关键词： low-energy electrons,spectator electron,resonant decay processes,Ne dimers,interatomic Coulombic decay,angular emission distribution
更新于2025-09-04 15:30:14