Ultrasensitive trace-detection of toxic and carcinogenic polycyclic aromatic hydrocarbons (PAHs) can ceaselessly propel the environmental surveillance in aqueous ecosystems. Due to the intrinsic nonadsorptive feature of PAHs, the promising technique of surface-enhanced Raman scattering (SERS) spectroscopy has been restricted to diverse functional ligands-based surface modifications of nano-substrates. However, it is not suitable for practical ultralow liquid analysis. Herein, we propose an extraordinary strategy to boost liquid-near infrared (NIR)-SERS activity of plasmonic Au/Ag nano-urchins (NUs) by introducing extra 808 nm laser-triggered an additional strong electromagnetic enhancement into routine 785 nm laser-Raman system. The synergistic double laser-excited NIR-SERS of colloidal Au/Ag NUs enables the Raman signals of crystal violet to be significantly enhanced, approaching a maximum of ∼34-fold increase than that of traditional bare 785 nm laser-excitation. More importantly, the improved liquid-NIR-SERS enables the in-situ detection limit of pyrene molecules in lake water to be achieved at ∼10−9 M, which is already better than many previous SERS results based on the complicated functionalized nano-substrates. The established double laser-boosted NIR-SERS can also be easily extended to the simultaneous trace-detection of three PAHs-contaminated mixtures, supporting well distinguishable capability. Undoubtedly, the present work opens a new versatile and innovative avenue for ultrasensitive NIR-SERS monitoring of nonadsorptive toxic pollutants in wastewater.

中文翻译：

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协同双激光束增强液体-NIR-SERS 用于湖水中非吸附性多环芳烃的超低检测

有毒和致癌多环芳烃 (PAHs) 的超灵敏痕量检测可以不断推动水生态系统的环境监测。由于 PAHs 固有的非吸附特性，表面增强拉曼散射 (SERS) 光谱的有前途的技术仅限于基于各种功能配体的纳米基材表面改性。但是，它不适用于实际的超低液分析。在此，我们提出了一种非凡的策略，通过在常规 785 nm 激光拉曼光谱中引入额外的 808 nm 激光触发的额外强电磁增强来提高等离子 Au/Ag 纳米海胆 (NUs) 的液体近红外 (NIR)-SERS 活性系统。胶体 Au/Ag NUs 的协同双激光激发 NIR-SERS 使结晶紫的拉曼信号显着增强，比传统的裸 785 nm 激光激发最大增加约 34 倍。更重要的是，改进的液体 NIR-SERS 使原位湖水中芘分子的检测限达到~10−9M，这已经比许多以前基于复杂功能化纳米基板的 SERS 结果更好。已建立的双激光增强 NIR-SERS 也可以轻松扩展到同时痕量检测三种 PAHs 污染的混合物，支持良好的区分能力。毫无疑问，目前的工作为废水中非吸附性有毒污染物的超灵敏 NIR-SERS 监测开辟了一条新的多功能和创新途径。