Yu Qiaozhi, Yao Zhengjian, Zhang Haolin, Li Zhibin, Chen Zhixing, Xiong Hanqing
National Biomedical Imaging Center, College of Future Technology, Peking University, Beijing 100871, China.
Institute of Molecular Medicine, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking University, Beijing 100871, China.
J Am Chem Soc. 2023 Apr 12;145(14):7758-7762. doi: 10.1021/jacs.3c01995. Epub 2023 Mar 30.
The pursuit of better sensitivity has always been one of the central themes in Raman spectroscopy. Recently, all-far-field single-molecule Raman spectroscopy has been demonstrated by a novel hybrid spectroscopy that couples Raman scattering with fluorescence emission. However, such frequency-domain spectroscopy lacks efficient hyperspectral excitation methods and encounters intrinsic strong fluorescence backgrounds from electronic transitions, hindering its applications in advanced Raman spectroscopy and microscopy. Here we report the ultrafast time-domain spectroscopy counterpart named transient stimulated Raman excited fluorescence (T-SREF): excited by two successive broadband femtosecond pulse pairs (i.e., the pump and Stokes pulses) with time-delay scanning, strong vibrational wave packet interference is revealed on the time-domain fluorescence trace, resulting in background-free spectra of the corresponding Raman modes after the Fourier transform. T-SREF achieves background-free Raman spectra of electronic-coupled vibrational modes with sensitivity up to the level of a few molecules, which paves the way for supermultiplexed fluorescence detection and molecular dynamics sensing.
追求更高的灵敏度一直是拉曼光谱学的核心主题之一。最近，一种将拉曼散射与荧光发射相结合的新型混合光谱技术实现了全远场单分子拉曼光谱。然而，这种频域光谱缺乏高效的高光谱激发方法，并且会遇到来自电子跃迁的固有强荧光背景，这阻碍了其在先进拉曼光谱学和显微镜中的应用。在此，我们报道了一种超快时域光谱技术，称为瞬态受激拉曼激发荧光（T-SREF）：通过两个连续的宽带飞秒脉冲对（即泵浦脉冲和斯托克斯脉冲）进行时间延迟扫描激发，在时域荧光迹线上揭示了强烈的振动波包干涉，经过傅里叶变换后得到相应拉曼模式的无背景光谱。T-SREF实现了电子耦合振动模式的无背景拉曼光谱，灵敏度高达几个分子的水平，这为超多重荧光检测和分子动力学传感铺平了道路。
