Ultrasensitive detection of trace substances holds significant importance in chemical analysis and biochemical sensing. As an exceptionally robust spectroscopic technique, surface-enhanced Raman spectroscopy offers significant advantages in the trace detection of analytes on various plasmonic noble-metal substrates. The recent integration of plasmonic nanostructures with nonplasmonic microcavities has emerged as a promising approach to enhance the sensitivity of Raman detection further. In this work, we developed an ultrasensitive scanning microsphere-coupled surface-enhanced Raman spectroscopy system and applied it to detect trace dye molecules. We found that based on conventional surface-enhanced Raman substrates with Au nanostructure films, the enhancement factor of Raman intensity can reach the level of ∼10⁹ through optimizing conditions. By incorporating a scanning silica dielectric microsphere, the Raman signals can be further enhanced by two orders of magnitude, resulting in an enhancement factor as high as ∼10¹¹ and corresponding to a detection limit of 10^–13 M for an aqueous crystal violet solution. Note that the detection limit reached the best performance ever recorded. The enhancement mechanism of dielectric microspheres is explained well by theoretical simulations. Additionally, our technique allows the spectroscopic imaging of trace analytes over a region, providing a facile strategy to fabricate hybrid Raman enhancers for ultrasensitive, highly efficient, and cost-effective sensing applications.

中文翻译：

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基于扫描微球耦合表面增强拉曼光谱的染料分子超灵敏痕量检测


痕量物质的超灵敏检测在化学分析和生化传感中具有重要意义。作为一种极其可靠的光谱技术，表面增强拉曼光谱在各种等离子体贵金属基底上的分析物痕量检测中具有显着的优势。最近，等离子体纳米结构与非等离子体微腔的集成已成为进一步提高拉曼检测灵敏度的有前途的方法。在这项工作中，我们开发了一种超灵敏扫描微球耦合表面增强拉曼光谱系统，并将其应用于检测痕量染料分子。我们发现，基于传统的带有Au纳米结构薄膜的表面增强拉曼基底，通过优化条件，拉曼强度的增强因子可以达到∼10 ⁹ 的水平。通过加入扫描二氧化硅介电微球，拉曼信号可以进一步增强两个数量级，增强因子高达~10 ¹¹ ，对应的检测限为10 ^–13