Xiong Hanqing, Qian Naixin, Miao Yupeng, Zhao Zhilun, Min Wei
Department of Chemistry , Columbia University , New York , New York 10027 , United States.
J Phys Chem Lett. 2019 Jul 5;10(13):3563-3570. doi: 10.1021/acs.jpclett.9b01289. Epub 2019 Jun 13.
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 of several nanometers. The results not only establish the generality of SREF spectroscopy for a wide range of molecules but also reveal a tight window of proper electronic preresonance for the stimulated Raman pumping process. Our theoretical modeling and further experiments on newly synthesized dyes also support the obtained insights, which would be valuable in designing and optimizing future SREF experiments for single-molecule vibrational spectroscopy and supermultiplex vibrational imaging.
荧光光谱法和拉曼光谱法是物理化学中两类主要的光谱方法。最近，受激拉曼激发荧光（SREF）已被证明（熊华等人，《自然·光子学》，2019年，第13卷，412 - 417页）是一种新的混合光谱技术，它将拉曼光谱的振动特异性与荧光光谱的超高灵敏度（低至单分子水平）结合起来。然而，这项概念验证研究受到商用激光源的可调谐性和近红外区域可激发分子可用性的限制。因此，SREF光谱的通用性仍未得到解决，并且对关键的电子预共振条件缺乏了解。在这项工作中，我们构建了一个改进的激发源，以探索可见光区域的SREF光谱。利用大量的红色染料，我们以几纳米的精细光谱间隔，系统地研究了十几种不同情况下的SREF光谱。结果不仅确立了SREF光谱对多种分子的通用性，还揭示了受激拉曼泵浦过程中合适电子预共振的狭窄窗口。我们对新合成染料的理论建模和进一步实验也支持了所获得的见解，这对于设计和优化未来用于单分子振动光谱和超多重振动成像的SREF实验将是有价值的。
