Browsing by Author "Li, Jie"

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Dual Strong Couplings Between TPPS J-Aggregates and Aluminum Plasmonic States
(2016-07-21)
Li, Jie
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Ueno, Kosei
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Uehara, Hiyori
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Guo, Jingchun
;
Oshikiri, Tomoya
We report on the spectral properties of strong coupling between the localized surface plasmon resonances (LSPRs) of aluminum (Al) nanostructures and tetraphenylporphyrin tetrasulfonic acid hydrate (TPPS) J-aggregates. Because of their wide spectral range of LSPR bands from ultraviolet to near-infrared wavelengths by controlling structural size, Al nanodisks can realize strong coupling with different excitons of TPPS J-aggregates. The Rabi splitting energies of the excitons based on Soret and Qbands are 300 and 180 meV, respectively. In addition to extinction spectrum, we have also measured an excitation spectrum to determine the essential absorption of the hybrid states and successfully confirmed a shoulder peak corresponding to a lower branch of hybrid states. In Al nanorod systems, strong coupling with two excitons can also be selectively induced by merely rotating the polarization of the incident light, which constituted a simple platform for the dynamic control of exciton/plasmon coupling states.
Efficient Hot-Electron Transfer under Modal Strong Coupling Conditions with Sacrificial Electron Donors
(2019-08-01)
Cao, Yanfeng
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Oshikiri, Tomoya
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Shi, Xu
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Ueno, Kosei
;
Li, Jie
The Front Cover of this special issue illustrates an investigation into hot-electron transfer efficiency under the modal strong coupling conditions. Photocurrent generation on the plasmonic photoanode was monitored with a sacrificial electron donor that consumes hot-holes efficiently. The average internal quantum efficiency at wavelengths from 500 to 800 nm reached 3%. It is emphasized, furthermore, that the Fermi level shift was observed during the hot-electron transfer involving water oxidation by the in-situ spectroelectrochemical measurements at the first time, and successfully resolve the Fermi level shift by the addition of the sacrificial electron donor. More information can be found in the Full Paper by Hiroaki Misawa et al.
Exotic Mode Suppression in Plasmonic Heterotrimer System
(2019-01-17)
Song, Hanfa
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Sun, Quan
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Li, Jie
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Yang, Fan
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Yang, Jinghuan
We investigate the far- and near-field properties of plasmonic heterotrimers with small detuning of the eigenfrequency numerically, theoretically, and experimentally. In our simulations, we find that the dipolar mode of the middle nanorod in the trimer system is greatly suppressed in both far and near fields. This phenomenon is confirmed by our subsequent experiments. The far-field suppression can be interpreted by the destructive interference due to the antiphase dipolar response of the respective nanorod. To deeply understand the underlying physics, an analytical model considering both the near-field-mediated direct coupling and radiative-field-mediated indirect coupling is adopted. We determine that the radiative field coupling, which is stronger in the trimer system with a smaller detuning, plays an essential role in mode suppression in the near field. Our work will provide new thoughts on the fundamental mechanisms of plasmon coupling and plasmon-based applications.
Exploring the Near-Field of Strongly Coupled Waveguide-Plasmon Modes by Plasmon-Induced Photocurrent Generation Using a Gold Nanograting-Loaded Titanium Dioxide Photoelectrode
(2017-10-05)
Guo, Jingchun
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Ueno, Kosei
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Yang, Jinghuan
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Shi, Xu
;
Li, Jie
Near-field spectrum measurement techniques, including near-field scanning optical microscopy, electron energy loss spectroscopy, and multiphoton photoemission electron microscopy, are powerful means to investigate near-field interactions directly on closely spaced metallic nanoparticles or a metallic nanostructure coupled with optical modes, such as whispering gallery mode and waveguide mode, which are called coupled plasmonic systems. In the present study, we have successfully measured the near-field spectra of coupled plasmonic systems using a simple photoelectrochemical measurement based on plasmon-induced water oxidation. Coupling was explored between the localized surface plasmon resonance (LSPR.) mode and waveguide mode of periodic gold nanogratings patterned on a thin titanium dioxide waveguide film. It is known that the far-field reflection spectrum of this waveguide-LSPR coupling system shows a complicated shape with multiple peaks, and the coupling has been explored by numerical electromagnetic simulations so far. However, in this study, it was clearly elucidated that an internal quantum efficiency (IQE) spectrum observed in the plasmon-induced photocurrent generation has successfully reproduced the near-field spectrum predicted by electromagnetic simulations under the coupling conditions. The photocurrent generation based on the plasmon-induced charge separation is due to the near-field effect, and it can be considered that the IQE spectrum corresponds to the near-field spectrum. This study paves a new way to indirectly measure the near-field spectrum of plasmonic systems.
Kruppel-Like Factor 4 Regulation of Cholesterol-25-Hydroxylase and Liver X Receptor Mitigates Atherosclerosis Susceptibility
(2017-10-03)
Li, Zhao
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Martin, Marcy
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Zhang, Jin
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Huang, Hsi-Yuan
;
Bai, Liang
BACKGROUND: Atherosclerosis is a multifaceted inflammatory disease involving cells in the vascular wall (eg, endothelial cells [ECs]), as well as circulating and resident immunogenic cells (eg, monocytes/macrophages). Acting as a ligand for liver X receptor (LXR), but an inhibitor of SREBP2 (sterol regulatory element-binding protein 2), 25-hydroxycholesterol, and its catalyzing enzyme cholesterol-25-hydroxylase (Ch25h) are important in regulating cellular inflammatory status and cholesterol biosynthesis in both ECs and monocytes/macrophages. METHODS: Bioinformatic analyses were used to investigate RNA-sequencing data to identify cholesterol oxidation and efflux genes regulated by Kruppel-like factor 4 (KLF4). In vitro experiments involving cultured ECs and macrophages and in vivo methods involving mice with Ch25h ablation were then used to explore the atheroprotective role of KLF4-Ch25h/LXR. RESULTS: Vasoprotective stimuli increased the expression of Ch25h and LXR via KLF4. The KLF4-Ch25h/LXR homeostatic axis functions through suppressing inflammation, evidenced by the reduction of inflammasome activity in ECs and the promotion of M1 to M2 phenotypic transition in macrophages. The increased atherosclerosis in apolipoprotein E-/-/Ch25h(-/-)mice further demonstrates the beneficial role of the KLF4-Ch25h/LXR axis in vascular function and disease. CONCLUSIONS: KLF4 transactivates Ch25h and LXR, thereby promoting the synergistic effects between ECs and macrophages to protect against atherosclerosis susceptibility.