有序银纳米方块阵列的SERS活性及其对有机污染物的痕量检测

Melamine, polychlorinated biphenyls (PCBs), and pesticide residues belong to organic pollutants that threaten human health and the ecosystem.The project aims at target capture and rapid detection of such organic pollutants at low concentrations by using cyclodextrin decorated Ag nanocube (AgNC) arrays,basing on the techniques such as liquid chemistry and interfacial self-assembly. The Ag nanocube arrays demonstrate high surface-enhanced Raman scattering (SERS) sensitivity, excellent SERS signal reproducibility, as well as good selective encapsulation ability of pollutant molecules owing to the hydrophobic cavity of cyclodextrin molecule. In the project, we firstly studied the correlation between the Ag nanoparticles shape, size and the corresponding electromagnetic enhancement. Subsequently, we investigated the influence of parameters (precursor, reductant, temperature, corrodent) on the particle shape, studied the assembly effect of AgNC either with DNA or at the solvent/air interface, to finally achieve edge length controllable and orderedly arranged AgNC arrays at micron scale. Lastly, we focused on the capture mechanism and SERS response of cyclodextrin decorated AgNC toward the organic pollutants at varied concentrations, and realize rapid detection of trace organic pollutants. The implementation of the project not only opens a door for the development of target enrichment and rapid detection of trace organic pollutants, but also demonstrates important application significance.

三聚氰胺、多氯联苯和农药残留等有机污染物，对人类健康和环境具有严重危害。本项目拟采用液相化学法、界面自组装等技术，构筑经环糊精修饰的尺寸可控的Ag纳米方块（简称AgNC）阵列，利用阵列的高表面增强拉曼（SERS）活性、均匀性以及环糊精对污染物分子良好的选择性捕获，实现靶向富集并痕量、快速检测三聚氰胺等有机污染物的目标。项目实施中，首先利用离散偶极子近似法拟合出具有最佳电磁场增强效果的Ag纳米粒子（形状，尺寸），研究配方、还原剂、温度、腐蚀剂等参数对银纳米粒子的形态调控，探索DNA和溶剂/空气界面对Ag纳米粒子的组装行为，制备尺度可控、微米范围内排列有序的AgNC阵列。在此基础上，探究环糊精修饰的AgNC阵列对污染物分子的捕获机制及SERS响应规律，实现对污染物分子的痕量、快速检测。开展本项目，对于发展新型有机污染物的富集、痕量、快速检测方法不仅具有重要科学意义，而且具有重要的使用价值。

农药等有机物的大量使用对生态坏境和人类健康造成了严重威胁。为了对有机污染物进行有效治理，早期预警和快速检测十分重要。表面增强拉曼散射(Surface enhanced Raman Scattering，简称SERS)效应能够将吸附在粗糙贵金属表面物质的拉曼信号放大6~12 个数量级，拉曼光谱表征的是分子的指纹振动峰，且拉曼光谱的测量快速、简单，被公认是一种有前景的环境分析方法。利用SERS效应实现对待检物的快速痕量检测的前提是构筑一种高活性、且能对弱吸附性待检物有富集效应的SERS基底。本项目以典型的有机污染物（甲基对硫磷、三聚氰胺和多氯联苯）的快速、痕量SERS探测为目标，构筑了以金/银纳米结构（纳米方块、纳米棒）为主的SERS活性单元，在宏观尺度（厘米）上将些表面等离激元纳米结构组装起来，获得相应的银/金纳米棒阵列、银纳米方块阵列；同时，在这些SERS活性基底上修饰巯基-β-环糊精或聚丙烯酸钠，对前述污染物进行富集，降低检测浓度。最终，对三聚氰胺、甲基对硫磷、多氯联苯的SERS灵敏度分别达到1纳摩尔、0.1微摩尔和1微摩尔量级。进一步，为了探索污染物的实时、快速SERS检测，基于静电吸附原理将多种表面等离激元纳米结构组装到锥形光纤探针上，发展了一种稳定性好、便携易用的SERS光纤探针传感器，对水体中甲基对硫磷能够快速SERS识别，检测灵敏度低于1微摩尔。本项目的实施，水体中痕量污染物的快速、痕量SERS检测提供了关键敏感材料和污染物富集等相关技术，对SERS传感器的发展及环境保护具有重要的意义。