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Ab initio model for the chlorophyll-lutein exciton coupling in the LHCII complex
摘要： 2A_g^- state of lutein plays a crucial role in photoprotection of higher plants. Due to its multiconfigurational nature, accurate description of this electronic state and respective transition properties is a formidable task. In this paper, applicability of various CASSCF and RASSCF formulations for description of the 2A_g^- state is discussed. It is shown that inclusion of the entire π-system of lutein into the active space is required for accurate calculation of transition properties. Exciton coupling in the chlorophyll-lutein dimer involved in non-photochemical quenching in the LHCII complex was calculated to provide a connection between pigment interactions and non-photochemical quenching regulation.
关键词： non-photochemical quenching,MCSCF,Xanthophyll,lutein,exciton coupling,LHCII
更新于2025-09-23 15:23:52
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Collective strong light-matter coupling in hierarchical microcavity-plasmon-exciton systems
摘要： Polaritons are compositional light-matter quasiparticles that arise as a result of strong coupling between the vacuum field of a resonant optical cavity and electronic excitations in quantum emitters. Reaching such a regime is often hard, as it requires materials possessing high oscillator strengths to interact with the relevant optical mode. Two-dimensional transition metal dichalcogenides (TMDCs) have recently emerged as promising candidates for realization of strong coupling regime at room temperature. However, these materials typically provide coupling strengths in the range of 10-40 meV, which may be insufficient for reaching strong coupling with low quality factor resonators. Here, we demonstrate a universal scheme that allows a straightforward realization of strong coupling with 2D materials and beyond. By intermixing plasmonic excitations in nanoparticle arrays with excitons in a WS2 monolayer inside a resonant metallic microcavity, we fabricate a hierarchical system with the collective microcavity-plasmon-exciton Rabi splitting exceeding ~500 meV at room temperature. Photoluminescence measurements of the coupled systems show dominant emission from the lower polariton branch, indicating the participation of excitons in the coupling process. Strong coupling has been recently suggested to affect numerous optical- and material-related properties including chemical reactivity, exciton transport and optical nonlinearities. With the universal scheme presented here, strong coupling across a wide spectral range is within easy reach and therefore exploring these exciting phenomena can be further pursued in a much broader class of materials.
关键词： TMDC,Strong plasmon-exciton coupling,collective Rabi splitting,monolayer WS2
更新于2025-09-23 15:21:21
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Correlative Study of Enhanced Excitonic Emission in ZnO Coated with Al Nanoparticles using Electron and Laser Excitation
摘要： Recently, metal nanoparticle surface coatings have been found to significantly enhance the ultra-violet luminescence intensity from ZnO, providing a viable means to mitigate optical losses and improve LED performance. Although there is general agreement that resonantly excited Localized Surface plasmons (LSps) in metal nanoparticles can directly couple to excitons in the semiconductor increasing their spontaneous emission rate, the exact mechanisms involved in this phenomenon are currently not fully understood. In this work, LSP-exciton coupling in bulk and nanostructured ZnO coated with a 2 nm Al nanoparticle layer is investigated using correlative photoluminescence and depth-resolved cathodoluminescence and time-resolved photoluminescence spectroscopy. Temperature-resolved cathodoluminescence and photoluminescence measurements from 10 K to 250 K show free exciton (FX) emission enhancement factors up to 12x at 80 K, and reveal that the FX couple more efficiently to the LSPs compared to the localized donor-bound excitons. A strong polarization dependence between the LSPs and FX is observed where FX transitions are more strongly enhanced when polarized in the same direction as the electric field of the incident excitation, which is different for laser and electron beam sources. This result indicates that selective enhancement of the excitonic emission peaks in the ZnO coated with Al nanoparticles can be achieved by choosing the appropriate ZnO substrate orientation.
关键词： Localized Surface plasmons,metal nanoparticle,ZnO,exciton coupling,luminescence
更新于2025-09-23 15:21:01
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Excitonically Coupled Cyclic BF2 Arrays of Calix[8]a?? and Calix[16]phyrin as Neara??IRa?? Chromophores
摘要： A pair of giant calix[n]phyrin derivatives namely calix[8]- (4) and calix[16]phyrin (5), involving two and four BF2 units, respectively, were prepared via the condensation of bis-naphthobipyrrolylmethene-BF2 complex with pentafluorobenzaldehyde. Both systems and precursor 3 were fully characterized, including via single crystal X-ray diffraction analyses. Calix[n]phyrins 4 and 5 display extremely high extinction coefficients (3.67 and 4.82 105 M-1cm-1, respectively) in the near-IR region. This observation was taken as initial evidence for strong excitonic coupling within these cyclic multi-chromophoric systems. Detailed insights into the effect of excitonic coupling dynamics on the electronic structure and photophysical properties of the macrocycles came from fluorescence, time-correlated single-photon counting (TCSPC) and transient absorption (TA) measurements. Support for the experimental findings came from theoretical studies. Taken in concert this combination of theory and experiment served to confirm that the coupling between the excitons depends on the specifics of the calix[n]phyrin structure, not just its size.
关键词： Cyclic BODIPY,Boron,Exciton Coupling,Porphyrinoids,NIR Dye,Calix[n]phyrin
更新于2025-09-23 15:19:57
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Excitonically Coupled Cyclic BF2 Arrays of Calix[8]a?? and Calix[16]phyrin as Neara??IRa?? Chromophores
摘要： A pair of giant calix[n]phyrin derivatives namely calix[8]- (4) and calix[16]phyrin (5), involving two and four BF2 units, respectively, were prepared via the condensation of the bis-naphthobipyrrolylmethene-BF2 complex with pentafluorobenzaldehyde. Both systems and precursor 3 were fully characterized, including via single crystal X-ray diffraction analyses. Calix[n]phyrins 4 and 5 display extremely high extinction coefficients (3.67 and 4.82 105 M-1cm-1, respectively) in the near-IR region. This observation was taken as initial evidence for strong excitonic coupling within these cyclic multi-chromophoric systems. Detailed insights into the effect of excitonic coupling dynamics on the electronic structure and photophysical properties of the macrocycles came from theoretical studies. Taken in concert this combination of theory and experiment served to confirm that the coupling between the excitons depends on the specifics of the calix[n]phyrin structure, not just its size.
关键词： Cyclic BODIPY,Boron,Exciton Coupling,Porphyrinoids,NIR Dye,Calix[n]phyrin
更新于2025-09-23 15:19:57
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Colloidal Assembly of Aua??Quantum Dota??Au Sandwiched Nanostructures with Strong Plasmona??Exciton Coupling
摘要： Strong plasmon-exciton coupling could occur in hybrid metal-dye/semiconductor nanostructures, where the fast energy exchange between plasmons and excitons leads to two new eigenmodes of the system, known as Rabi splitting. In experiment, strongly coupled nanosystems are difficult to obtain because they require some strict conditions, such as low plasmonic damping, small plasmon mode volume, and good spectral overlap. This work demonstrates strongly coupled metal-semiconductor nanostructures can be constructed using colloidal assembly. Specifically, sandwiched Au-QD-Au nanostructures were created through the assembly of Au nanoparticles and colloidal quantum dots (QDs). The sizes of the QDs and the assembly conditions were varied to control the mode volume of the plasmonic cavity formed between the two Au nanoparticles. With decreased gap size, Rabi splitting was observed in both dark-field scattering and fluorescence spectra of single Au-QD-Au nanostructures. Theoretical simulations revealed that the strong coupling occurred between the excitons and the octupolar plasmon modes.
关键词： Au-QD-Au nanostructures,Rabi splitting,octupolar plasmon modes,plasmon-exciton coupling,colloidal assembly
更新于2025-09-19 17:13:59
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Plasmon-Enhanced Fluorescence in Gold Nanorod-Quantum Dot Coupled Systems
摘要： Plasmon-exciton coupling is of great importance to many optical devices and applications. One of the coupling manifestations is plasmon-enhanced fluorescence. Although this effect is demonstrated in numerous experimental and theoretical works, there are different particle shapes for which this effect is not fully investigated. In this work electrostatic complexes of gold nanorods and CdSe/CdZnS quantum dots were studied. Double-resonant gold nanorods have an advantage of the simultaneous enhancement of the absorption and emission when the plasmon bands match the excitation and fluorescence wavelengths of an emitter. A relationship between the concentration of quantum dots in the complexes and the enhancement factor was established. It was demonstrated that the enhancement factor is inversely proportional to the concentration of quantum dots. The maximal fluorescence enhancement by 10.8 times was observed in the complex with the smallest relative concentration of 2.5 quantum dots per rod and approximately 5 nm distance between them. Moreover, the influence of quantum dot location on the gold nanorod surface plays an important role. Theoretical study and experimental data indicate that only the position near the nanorod ends provides the enhancement. At the same time, the localization of quantum dots on the sides of the nanorods leads to the fluorescence quenching.
关键词： quantum dot fluorescence,gold nanorod-quantum dot complexes,plasmon-enhanced fluorescence,plasmon-exciton coupling,gold nanorods
更新于2025-09-11 14:15:04