以Au@Ag双金属纳米棒为核的温敏性复合微凝胶的可控制备与组装及其用于SERS基底的研究

Surface enhanced Raman spectroscopy (SERS) is a kind of analytical method with superhigh sensitivity, which can provide the information of molecular structure. However, two problems are existing for SERS method due to its substrate materials. One is poor reproducibility of its analysis results, and the other is that the analytes capable of being analyzing by SERS method are limited. For example, the compounds with hydroxy group, such as alcohols and phenols, are hard to be analyzed by SERS method. In order to address these problems, new types of substrate materials for SERS are designed and will be prepared in the project. Firstly, temperature sensitive core-shell composite microgels based on Au@Ag bimetallic nanorods as cores, with diameter polydispersity less than 10%, will be synthesized by seed precipitation polymerization method or surface initiated atom transfer radical polymerization method. Next, some reactive groups will be introduced on their surfaces by modification. Finally, the monolayer film with stable two-dimension ordered structure or the colloidal crystal with stable three-dimension ordered structure will be prepared by assembly of the composite microgels under suitable conditions, followed by post-crosslinking reaction. Using the monolayer film or colloidal crystal as substrate, the SERS method cabable of analyzing trace bisphenol A in aqueous solution qualitatively or quantitatively will be established. The scientific significance of the project lies in controllable preparation of multi-functional composite materials with highly ordered structure. Its practical value is reflected by potential applications of the established SERS method in conveniently and rapidly monitoring the bisphenol A concentration in environmental water samples.

表面增强拉曼光谱（SERS）是一种既有超高灵敏度，又能提供分子结构信息的分析方法。然而受基底材料所限，SERS方法目前存在两方面问题：一是分析结果的重复性差；二是适合分析的对象少，例如难以分析含羟基的醇类和酚类化合物。为解决这些问题，本项目设计并制备新型的SERS基底材料。首先通过种子沉淀聚合法或表面引发ATRP法合成以Au@Ag双金属纳米棒为核、粒径多分散性指数小于10%的温敏性核壳复合微凝胶，然后通过改性在其表面引入具有反应活性的基团，最后在适当条件下使复合微凝胶组装并经后交联反应形成具有稳定二维有序结构的单层膜或具有稳定三维有序结构的胶体晶体。以制得的单层膜或胶体晶体为基底，建立可定量分析水溶液中痕量双酚A的SERS方法。本项目的科学意义在于对具有高度有序结构的多功能复合材料实现可控制备，其实际价值在于：以研究的新型基底建立的SERS分析方法有望用于环境水样中双酚A的方便和快速检测。

本项目首先采用种子生长法合成了单分散的Au@Ag核壳复合双金属纳米棒（Au@AgNRs）。作为表面增强拉曼光谱（SERS）基底，它比常用的Au纳米棒和Au纳米球有更强的SERS活性，比常用的Ag纳米粒子（AgNPs）有更高的耐氧化性，检测结果重复性好，是一种具有优良综合性能的新型胶体贵金属纳米粒子SERS基底。为解决分散在水中的Au@AgNRs或AgNPs存在的胶体稳定性不高的问题，先后采用沉淀聚合法和静电纺丝技术将单分散的Au@AgNRs或AgNPs负载到温度响应性微凝胶或纳米纤维膜中，另外通过浸渍涂覆法将以Au@AgNR为核的温度响应性核壳复合微凝胶在处理过的硅片上组装形成了具有二维有序结构的单层膜，制备了另外七种新型SERS基底。由于这些SERS基底都是基于单分散的Au@AgNRs或AgNPs，因此它们不仅具有较高的SERS活性，而且测试结果具有良好的重复性，可用于定量检测，较好地解决了过去常用SERS基底难以用于定量检测的问题。除单独的Au@AgNRs外，其余SERS基底都是将单分散的Au@AgNRs或AgNPs负载到具有温度响应性的微凝胶及其形成的单层膜或温度响应性纳米纤维膜等温度响应性材料中，因此有些基底可通过温度变化引起的相转变捕捉水溶液中难以吸附在金属纳米粒子表面的待分析物，如1-萘酚等，另外还可通过升高检测温度来增强这些基底的SERS活性，从而提高了检测灵敏度。将单分散的Au@AgNRs或AgNPs负载到纳米纤维膜中，制得的柔性且无需支撑的SERS基底不仅解决了过去常用的胶体贵金属纳米粒子基底存在的胶体稳定性差的问题，而且具有宏观形状和机械强度，储存稳定，使用方便，并且可通过擦拭来收集固体样品表面的残留物来进行SERS检测，从而解决了过去用SERS基底和其它手段分析水果蔬菜表面农药残留需要复杂制样过程的缺点。另外通过研究还发现，采用同轴静电纺丝法并结合热处理和溶剂萃取等工艺制备的载Au@AgNRs温度响应性空心纳米纤维膜比单轴静电纺制备的载Au@AgNRs温度响应性纳米纤维膜和同轴静电纺制备的壳层载Au@AgNRs核壳复合纳米纤维膜有更高的SERS活性。本项目制得的八种新型SERS基底在环境监测、食品安全分析和毒品检测等领域有广阔的应用前景。