Single-molecule surface-enhanced Raman spectroscopy of nonresonant molecules.

Single-molecule surface-enhanced Raman scattering (SERS) detection of nonresonant molecules is demonstrated experimentally using the bianalyte SERS method. To this end, bianalyte SERS is performed at 633 nm excitation using the nonresonant molecule 1,2-di-(4-pyridyl)-ethylene (BPE) in combination with a benzotriazole derivative as a partner. The results are then extended to the even more challenging case of a small nonresonant molecule, adenine, using an isotopically substituted adenine as bianalyte SERS partners.

Bi-analyte SERS with isotopically edited dyes.

Isotopically substituted rhodamine dyes provide ideal probes for the study of single-molecule surface enhanced Raman scattering (SM-SERS) events through multiple-analyte techniques. Isotopic editing should, in principle, provide probes that have identical chemical properties (and surface chemistries); while exhibiting at the same time distinct Raman features which enable us to identify single-molecule SERS events. We present here a specific example of two-analyte SM-SERS based on the isotopic substitution of a methyl ester rhodamine dye.

Statistics of single-molecule surface enhanced Raman scattering signals: fluctuation analysis with multiple analyte techniques.

The mathematical background, based on a variation of the principal component analysis (PCA) method, is developed for the understanding of fluctuating multiple analyte single-molecule (SM) surface enhanced Raman scattering (SERS) signals; with emphasis on the bianalyte SERS technique developed recently. The method and its significance are presented to provide a systematic framework with which several aspects of the statistics of SM-SERS signals can be analyzed in general. We also apply the method to a concrete example of bianalyte statistics in silver colloidal solutions and discuss related topics around experimental issues and the interpretation of single-molecule SERS data.