Stimulated Raman Excited Fluorescence Spectroscopy of Visible Dyes

Fluorescence spectroscopy and Raman spectroscopy are two major classes of spectroscopy methods in physical chemistry. Very recently, stimulated Raman excited fluorescence (SREF) has been demonstrated (Xiong, H.; et al. Nature Photonics, 2019, 13, 412−417) as a new hybrid spectroscopy that combines the vibrational specificity of Raman spectroscopy with the superb sensitivity of fluorescence spectroscopy (down to the single-molecule level). However, this proof-of-concept study was limited by both the tunability of the commercial laser source and the availability of the excitable molecules in the near-infrared. As a result, the generality of SREF spectroscopy remains unaddressed, and the understanding of the critical electronic preresonance condition is lacking. In this work, we built a modified excitation source to explore SREF spectroscopy in the visible region. Harnessing a large palette of red dyes, we have systematically studied SREF spectroscopy on a dozen different cases with a fine spectral interval ...