Wang Shuo, Wei Youchao, Zheng Siyang, Zhang Zhaofu, Tang Xi, Liang Liangbo, Zang Zhigang, Qian Qingkai
Key Laboratory of Optoelectronic Technology and System (Ministry of Education), College of Optoelectronic Engineering, Chongqing University, Chongqing 400044, China.
The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China.
Anal Chem. 2024 Jun 18;96(24):9917-9926. doi: 10.1021/acs.analchem.4c01051. Epub 2024 Jun 5.
Two-dimensional (2D) materials have been extensively implemented as surface-enhanced Raman scattering (SERS) substrates, enabling trace-molecule detection for broad applications. However, the accurate understanding of the mechanism remains elusive because most theoretical explanations are still phenomenological or qualitative based on simplified models and rough assumptions. To advance the development of 2D material-assisted SERS, it is vital to attain a comprehensive understanding of the enhancement mechanism and a quantitative assessment of the enhancement performance. Here, the microscopic chemical mechanism of 2D material-assisted SERS is quantitatively investigated. The frequency-dependent Raman scattering cross sections suggest that the 2D materials' SERS performance is strongly dependent on the excitation wavelengths and the molecule types. By analysis of the microscopic Raman scattering processes, the comprehensive contributions of SERS can be revealed. Beyond the widely postulated charge transfer mechanisms, the quantitative results conclusively demonstrate that the resonant transitions within 2D materials alone are also capable of enhancing the molecular Raman scattering through the diffusive scattering of phonons. Furthermore, all of these scattering routines will interfere with each other and determine the final SERS performance. Our results not only provide a complete picture of the SERS mechanisms but also demonstrate a systematic and quantitative approach to theoretically understand, predict, and promote the 2D materials SERS toward analytical applications.
二维（2D）材料已被广泛用作表面增强拉曼散射（SERS）基底，可实现痕量分子检测，具有广泛的应用。然而，由于大多数理论解释仍基于简化模型和粗略假设，是现象学或定性的，因此对其机制的准确理解仍然难以捉摸。为了推动二维材料辅助SERS的发展，全面理解增强机制并对增强性能进行定量评估至关重要。在此，对二维材料辅助SERS的微观化学机制进行了定量研究。频率相关的拉曼散射截面表明，二维材料的SERS性能强烈依赖于激发波长和分子类型。通过分析微观拉曼散射过程，可以揭示SERS的综合贡献。除了广泛假设的电荷转移机制外，定量结果确凿地表明，仅二维材料内的共振跃迁也能够通过声子的扩散散射增强分子拉曼散射。此外，所有这些散射过程都会相互干扰并决定最终的SERS性能。我们的结果不仅提供了SERS机制的完整图景，还展示了一种系统的定量方法，用于从理论上理解、预测和推动二维材料SERS在分析应用中的发展。
