期刊
NANO LETTERS
卷 18, 期 1, 页码 262-271出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.7b04052
关键词
Surface-enhanced Raman scattering; plasmonics; vibrational spectroscopy
类别
资金
- BioNano Health-Guard Research Center - Ministry of Science, ICT & Future Planning (MSIP) of Korea [H-GUARD_2013M3A6B2078950]
- NRF [2016R1A2B2011160, NRF-2016M3A7B4909776]
- Nano RD program
The existence of sub-nanometer plasmonic hot spots and their relevance in spectroscopy and microscopy applications remain elusive despite a few recent theoretical and experimental evidence supporting this possibility. In this Letter, we present new spectroscopic evidence suggesting that Angstrom-sized hot-spots exist on the surfaces of plasmon-excited nanostructures. Surface-enhanced Raman scattering (SERS) spectra of 4,4'-biphenyl dithiols placed in metallic junctions show simultaneously blinking Stokes and anti-Stokes spectra, some of which exhibit only one prominent vibrational peak. The activated vibrational modes were found to vary widely between junction sites. Such site-specific, single-peak spectra could be successfully modeled using single-molecule SERS induced by a hot-spot with a diameter no larger than 3.5 angstrom, located at the specific molecular sites. Furthermore, the model, which assumes the stochastic creation of hot-spots on locally flat metallic surfaces, consistently reproduces the intensity distributions and occurrence statistics of the blinking SERS peaks, further confirming that the sources of the hot-spots are located on the metallic surfaces. This result not only provides compelling evidence for the existence of Angstrom-sized hot-spots but also opens up the new possibilities for the vibrational and electronic control of single-molecule photochemistry and real-space visualization of molecular vibration modes.
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