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Chemical Enhancement and Quenching in Single-Molecule Tip-Enhanced Raman Spectroscopy |
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| Authors: | Dr. Ben Yang Dr. Gong Chen Dr. Atif Ghafoor Yu-Fan Zhang Dr. Xian-Biao Zhang Hang Li Xiao-Ru Dong Rui-Pu Wang Prof. Yang Zhang Prof. Yao Zhang Prof. Zhen-Chao Dong |
| Affiliation: | 1. Hefei National Research Center for Physical Sciences at the Microscale and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, 230026 China These authors contributed equally to this work.;2. Hefei National Research Center for Physical Sciences at the Microscale and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, 230026 China;3. Hefei National Research Center for Physical Sciences at the Microscale and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, 230026 China School of Physics and Department of Chemical Physics, University of Science and Technology of China Hefei, Anhui, 230026 China Hefei National Laboratory, University of Science and Technology of China, Hefei, 230088 China |
| Abstract: | Despite intensive research in surface enhanced Raman spectroscopy (SERS), the influence mechanism of chemical effects on Raman signals remains elusive. Here, we investigate such chemical effects through tip-enhanced Raman spectroscopy (TERS) of a single planar ZnPc molecule with varying but controlled contact environments. TERS signals are found dramatically enhanced upon making a tip–molecule point contact. A combined physico-chemical mechanism is proposed to explain such an enhancement via the generation of a ground-state charge-transfer induced vertical Raman polarizability that is further enhanced by the strong vertical plasmonic field in the nanocavity. In contrast, TERS signals from ZnPc chemisorbed flatly on substrates are found strongly quenched, which is rationalized by the Raman polarizability screening effect induced by interfacial dynamic charge transfer. Our results provide deep insights into the understanding of the chemical effects in TERS/SERS enhancement and quenching. |
| Keywords: | Chemical Enhancement Point Contact Raman Quenching Single Molecule Tip-Enhanced Raman Spectroscopy |