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- Gong, Zu-Yong, et al.
(författare)
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Harvesting of surface plasmon polaritons : Role of the confinement factor
- 2020
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 153:9
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Tidskriftsartikel (refereegranskat)abstract
- Surface plasmon polaritons (SPPs) are propagating waves generated at the interface of a metal (metamaterial) and a dielectric. The intensity of SPPs often exponentially decays away from the surface, while their wavelengths can be tuned by the confinement effect. We present here a computational method based on quantum-mechanical theory to fully describe the interaction between confined SPPs and adsorbed molecules at the interface. Special attention has been paid to the roles of the confinement factor. Taking a prototype dye sensitized solar cell as an example, calculated results reveal that with the increase in the confinement factor in metal/dielectric interfaces, the breakdown of the conventional dipole approximation emerges, which allows efficient harvesting of SPPs with low excitation energies and, thus, increases the efficiency of the solar energy conversion by dye molecules. Furthermore, at the metamaterial/dielectric interface, SPPs with large confinement factors could directly excite the dye molecule from its ground singlet state to the triplet state, opening an entirely new channel with long-living carriers for the photovoltaic conversion. Our results not only provide a rigorous theory for the SPP-molecule interaction but also highlight the important role played by the momentum of the light in plasmon related studies.
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| 3. |
- Gong, Zu-Yong, et al.
(författare)
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Optical Excitation in Donor-Pt-Acceptor Complexes : Role of the Structure
- 2016
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 120:20, s. 3547-3553
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Tidskriftsartikel (refereegranskat)abstract
- The optical properties of the Pt complexes in the form of donor-metal-acceptor (D-M-A) were studied at the first-principles level. Calculated results show that for the frontier molecular orbitals (MOs) of a D-M-A structure the energies of unoccupied frontier MO can be mainly determined by the interaction between M and A, whereas the M-A and M-D interactions both determine the energies of occupied frontier MO. By developing a straightforward transition dipole decomposition method, we found that not only the local excitations in D but also those in A can significantly contribute to the charge-transfer (CT) excitation. Furthermore, the calculations also demonstrate that by tuning the dihedral angle between D and A the transition probability can be precisely controlled so as to broaden the spectrum region of photoabsorption. For the D-M-A molecule with a delocalized pi system in A, the CT excitation barely affects the electronic structures of metal, suggesting that the oxidation state of the metal can be kept during the excitation. These understandings for the optical properties of the D-M-A molecule would be useful for the design of dye-sensitized solar cells, photocatalysis, and luminescence systems.
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| 4. |
- Qiu, Feifei, et al.
(författare)
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Optical Images of Molecular Vibronic Couplings from Tip-Enhanced Fluorescence Excitation SpectroscopyY
- 2022
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Ingår i: JACS Au. - : American Chemical Society (ACS). - 2691-3704. ; 2:1, s. 150-158
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Tidskriftsartikel (refereegranskat)abstract
- Tip-based photoemission spectroscopic techniques have now achieved subnanometer resolution that allows visualization of the chemical structure and even the ground-state vibrational modes of a single molecule. However, the ability to visualize the interplay between electronic and nuclear motions of excited states, i.e., vibronic couplings, is yet to be explored. Herein, we theoretically propose a new technique, namely, tip-enhanced fluorescence excitation (TEFE). TEFE takes advantage of the highly confined plasmonic field and thus can offer a possibility to directly visualize the vibronic effect of a single molecule in real space for arbitrary excited states in a given energy window. Numerical simulations for a single porphine molecule confirm that vibronic couplings originating from Herzberg-Teller (HT) active modes can be visually identified. TEFE further enables high-order vibrational transitions that are normally suppressed in the other plasmon-based processes. Images of the combination vibrational transitions have the same pattern as that of their parental HT active mode's fundamental transition, providing a direct protocol for measurements of the activity of Franck-Condon modes of selected excited states. These findings strongly suggest that TEFE is a powerful strategy to identify the involvement of molecular moieties in the complicated electron-nuclear interactions of the excited states at the single-molecule level.
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