Chandran Aruna, Camden Jon P
Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States.
ACS Nano. 2024 Aug 13;18(32):20827-20834. doi: 10.1021/acsnano.4c06429. Epub 2024 Aug 1.
In this Perspective, we provide a historical overview of the surface-enhanced hyper-Raman scattering (SEHRS) effect, describe its essential components, highlight the close connection between theory and experiment in several vignettes, and discuss recent analytical applications. SEHRS, the two-photon analog of surface-enhanced Raman scattering (SERS), is a spontaneous nonlinear scattering exhibited by molecules in a plasmonic field. Hyper Raman provides distinctive information on the molecular vibrations and electronic excited states of analytes. A 40-year old mystery surrounding the SEHRS spectra of R6G is used to illustrate the power of SEHRS to explore excited electronic states, revealing how non-Condon effects can influence the two-photon molecular properties. The exceptionally large enhancement factors (>10) obtained from SEHRS enable the analysis of single molecules and molecules at very low concentrations. This high sensitivity is further augmented by an increased sensitivity to chemical effects, allowing SEHRS to probe changes in the local environment and the orientation of surface ligands. As most SEHRS experiments employ near-infrared (NIR) and short-wave infrared (SWIR) light, it also holds promise for bioimaging studies. Before concluding, we discuss future directions and challenges for the field as it moves forward.
在这篇综述中，我们提供了表面增强超拉曼散射（SEHRS）效应的历史概述，描述了其基本组成部分，通过几个实例突出了理论与实验之间的紧密联系，并讨论了近期的分析应用。SEHRS是表面增强拉曼散射（SERS）的双光子类似物，是分子在等离子体场中表现出的一种自发非线性散射。超拉曼散射提供了关于分析物分子振动和电子激发态的独特信息。围绕R6G的SEHRS光谱存在了40年的谜团被用来阐明SEHRS探索激发电子态的能力，揭示了非康登效应如何影响双光子分子性质。从SEHRS获得的异常大的增强因子（>10）使得能够对单分子和极低浓度的分子进行分析。对化学效应的更高灵敏度进一步增强了这种高灵敏度，使SEHRS能够探测局部环境的变化和表面配体的取向。由于大多数SEHRS实验采用近红外（NIR）和短波红外（SWIR）光，它在生物成像研究方面也具有前景。在结束之前，我们讨论了该领域在向前发展时的未来方向和挑战。
