Abstract
Surface-enhanced Raman scattering (SERS) spectroscopy has attracted tremendous interests as a highly sensitive label-free tool. The local field produced by the excitation of localized surface plasmon resonances (LSPRs) dominates the overall enhancement of SERS. Such an electromagnetic enhancement is unfortunately accompanied by a strong modification in the relative intensity of the original Raman spectra, which highly distorts spectral features providing chemical information. Here we propose a robust method to retrieve the fingerprint of intrinsic chemical information from the SERS spectra. The method is established based on the finding that the SERS background originates from the LSPR-modulated photoluminescence, which contains the local field information shared also by SERS. We validate this concept of retrieval of intrinsic fingerprint information in well controlled single metallic nanoantennas of varying aspect ratios. We further demonstrate its unambiguity and generality in more complicated systems of tip-enhanced Raman spectroscopy (TERS) and SERS of silver nanoaggregates.
Highlights
Surface-enhanced Raman scattering (SERS) spectroscopy has attracted tremendous interests as a highly sensitive label-free tool
We choose a first set of five gold nanorods with different aspect ratios for the following experiments, which are marked in the dark-field image (Fig. 2a) and characterized by scanning electron microscope (SEM) (Fig. 2b)
The PL and scattering spectra of the five nanorods were excited with a 633 nm continuous wave (CW) laser and a white source, respectively, and were collected through the same objective using a home-built combined dark-field microscope and Raman microscope system (See schematic diagram of the system in Supplementary Fig. 2)
Summary
Surface-enhanced Raman scattering (SERS) spectroscopy has attracted tremendous interests as a highly sensitive label-free tool. The local field produced by the excitation of localized surface plasmon resonances (LSPRs) dominates the overall enhancement of SERS Such an electromagnetic enhancement is accompanied by a strong modification in the relative intensity of the original Raman spectra, which highly distorts spectral features providing chemical information. Localized surface plasmon resonances (LSPRs)[1] in metallic nanostructures can confine incident light into a nanoscale volume characterized by strongly enhanced optical fields These hot-spots can dramatically enhance the Raman scattering[2,3,4,5], fluorescence[6,7], infrared absorption[8], or nonlinear optical signal[9], leading to a family of plasmon-enhanced spectroscopies. We use single-gold nanorods as nanoantennas, which are resonant at different wavelengths but show the same chemical properties, to demonstrate such concept of correction We carefully correlate their morphology, LSPR scattering, PL, SERS background and relative intensity of the SERS peaks (Fig. 1). The generality of the proposed method is further supported by the results from more complex plasmonic systems including gap-mode TERS configurations and silver nanoaggregates
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