Department of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan.
Research Center for Spectrochemistry, The University of Tokyo, Tokyo 113-0033, Japan.
J Phys Chem Lett. 2021 Aug 19;12(32):7859-7865. doi: 10.1021/acs.jpclett.1c01741. Epub 2021 Aug 12.
Fluorescence-encoded vibrational spectroscopy has become increasingly more popular by virtue of its high chemical specificity and sensitivity. However, current fluorescence-encoded vibrational spectroscopy methods lack sensitivity in the low-frequency region, which if addressed could further enhance their capabilities. Here, we present a method for highly sensitive low-frequency fluorescence-encoded vibrational spectroscopy, termed fluorescence-encoded time-domain coherent Raman spectroscopy (FLETCHERS). By first exciting molecules into vibrationally excited states and then promoting the vibrating molecules to electronic states at varying times, the molecular vibrations can be encoded onto the emitted time-domain fluorescence intensity. We demonstrate the sensitive low-frequency detection capability of FLETCHERS by measuring vibrational spectra in the lower fingerprint region of rhodamine 800 solutions as dilute as 250 nM, which is ∼1000 times more sensitive than conventional vibrational spectroscopy. These results, along with further improvement of the method, open up the prospect of performing single-molecule vibrational spectroscopy in the low-frequency region.
荧光编码振动光谱由于其具有高的化学特异性和灵敏度而变得越来越流行。然而，目前的荧光编码振动光谱方法在低频区域缺乏灵敏度，如果解决了这一问题，将进一步提高它们的性能。在这里，我们提出了一种用于高灵敏度低频荧光编码振动光谱的方法，称为荧光编码时域相干拉曼光谱（FLETCHERS）。通过首先将分子激发到振动激发态，然后在不同的时间将振动分子推向电子态，可以将分子振动编码到发射的时域荧光强度上。我们通过测量浓度低至 250 nM 的若丹明 800 溶液在较低的指纹区域的振动光谱，证明了 FLETCHERS 的灵敏低频检测能力，其灵敏度比传统的振动光谱高约 1000 倍。这些结果以及该方法的进一步改进，为在低频区域进行单分子振动光谱学研究开辟了前景。
