Correct spectral conversion between surface-enhanced raman and plasmon resonance scattering from nanoparticle dimers for single-molecule detection.

Simultaneous measurement of surface-enhanced Raman scattering (SERS) and localized surface plasmon resonance (LSPR) in nanoparticle dimers presents outstanding opportunities in molecular identification and in the elucidation of physical properties, such as the size, distance, and deformation of target species. SERS-LSPR instrumentation exists and has been used under limited conditions, but the extraction of SERS and LSPR readouts from a single measurement is still a challenge. Herein, the extraction of LSPR spectra from SERS signals is reported and a tool for measuring the interparticle distance from Raman enhancement data by the standardization of the SERS signal is proposed. The SERS nanoruler mechanism incorporates two important aspects (the LSPR scattering peak shift and the Raman shift for measuring interparticle distance), and signifies their exact one-to-one correspondence after spectral correction. The developed methodology is applied to calculate the interparticle distance between nanoparticle dimers from SERS signals, to detect and quantify DNA at the single-molecule level in a base-pair-specific manner. It is also shown that the SERS nanoruler concept can be used in structural analysis for the specific detection of the interaction of immunoglobulin G (IgG) with its target from bianalyte Raman signals with identical shaping at single-molecule resolution. The SERS profile shaping approach not only offers a new detection mechanism for single molecules, but also has excellent potential for studying protein interactions and the intracellular detection of mRNA.