Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA.
J Chem Phys. 2022 May 7;156(17):174202. doi: 10.1063/5.0088435.
Fluorescence-encoded infrared (FEIR) spectroscopy is a vibrational spectroscopy technique that has recently demonstrated the capability of single-molecule sensitivity in solution without near-field enhancement. This work explores the practical experimental factors that are required for successful FEIR measurements in both the single-molecule and bulk regimes. We investigate the role of resonance conditions by performing measurements on a series of coumarin fluorophores of varying electronic transition frequencies. To analyze variations in signal strength and signal to background between molecules, we introduce an FEIR brightness metric that normalizes out measurement-specific parameters. We find that the effect of the resonance condition on FEIR brightness can be reasonably well described by the electronic absorption spectrum. We discuss strategies for optimizing detection quality and sensitivity in bulk and single-molecule experiments.
荧光编码红外（FEIR）光谱是一种振动光谱技术，最近已经证明了在没有近场增强的情况下在溶液中实现单分子灵敏度的能力。这项工作探索了在单分子和体相两种情况下成功进行 FEIR 测量所需的实际实验因素。我们通过对一系列具有不同电子跃迁频率的香豆素荧光团进行测量，研究了共振条件的作用。为了分析分子间信号强度和信号背景的变化，我们引入了一种 FEIR 亮度指标，该指标可以消除测量特定参数的影响。我们发现，共振条件对 FEIR 亮度的影响可以用电子吸收光谱很好地描述。我们讨论了在体相和单分子实验中优化检测质量和灵敏度的策略。
