Compared to rigid surface-enhanced Raman scatting (SERS) substrates, flexible SERS substrates offer significant advantages for the detection of pesticide residues on vegetable and fruit surfaces, primarily due to their convenient sampling process and shorter detection times. However, for paper-based SERS substrates, gold nanoparticles (AuNPs) are easy to form ineffective dispersion in the three-dimensional network structure of paper, resulting in unsatisfactory SERS enhancement. To address this challenge and achieve high-performance flexible SERS substrates, a novel sandwich structure is proposed. Specifically, AuNPs are aggregated on expanded graphite (EG) through a chemical enhancement process facilitated by LiCl. EG is found to improve the adsorption capacity of targeted molecules while preventing signal attenuation caused by filter papers. By employing an aggregating agent at specific concentrations, it is possible to significantly increase the amounts of hot spots to provide a more pronounced enhancement effect. Furthermore, the developed flexible SERS substrates are applied to qualitatively and quantitatively detect pesticide residues, including Thiram, Nitrofural and Dinotefuran. The flexible SERS substrates demonstrate high accuracy and robustness, making them easily storable and suitable for practical applications.

中文翻译：

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具有三明治结构的高灵敏度柔性SERS基底，用于快速检测痕量农药残留

与刚性表面增强拉曼散射（SERS）基底相比，柔性SERS基底在检测蔬菜和水果表面农药残留方面具有显着优势，这主要是由于其方便的采样过程和更短的检测时间。然而，对于纸基SERS基底来说，金纳米粒子（AuNPs）很容易在纸张的三维网络结构中形成无效的分散，导致SERS增强效果不理想。为了应对这一挑战并实现高性能柔性 SERS 基板，提出了一种新型夹层结构。具体来说，AuNP 通过 LiCl 促进的化学增强过程聚集在膨胀石墨 (EG) 上。研究发现，EG 可以提高目标分子的吸附能力，同时防止滤纸造成的信号衰减。通过使用特定浓度的聚集剂，可以显着增加热点的数量，从而提供更显着的增强效果。此外，开发的柔性SERS基质可用于定性和定量检测农药残留，包括福美双、呋喃西林和呋虫胺。柔性 SERS 基板具有高精度和坚固性，使其易于存储并适合实际应用。