氧化石墨烯纳米空间层调控贵金属三明治复合结构及其高效SERS性能研究

Surface-enhanced Raman scattering as an ultrasensitive and nondestructive technique has great potential applications in many fields. Yet it is one of the most challenging steps to construct ideal SERS platform which simultaneously meet the requirements of high sensitivity, stability and excellent reproducibility. In recent years, graphene oxide has aroused extensive attention in the SERS field due to its exceptional physicochemical properties. This proposed work is aimed at developing a series of anisotropic silver and gold nanostructures with controlled size, morphology, and nanoscale spacer. A novel SERS-active substrates using GO as nanospacer will be fabricated wherein the GO films are embedded between two layers of plasmonic metal nanostructures. The effect of type, size, morphology of noble metal nanoparticles and the GO nanospacer on the plasmonic and SERS properties will be investigated; In combination theoretical simulations with experimental studies, the enhancement mechanism of SERS signal will be systematically investigated based on multi-dimensional coupling between the plasmonic metal nanoparticles on both horizontal and vertical directions; The sandwich structure-SERS performance relationship will be elucidated; We will further explore the rapid, direct and ultrasensitive SERS monitoring for trace persistent organic pollutants (polychlorinated biphenyls-PCBs) using GO embedded sandwich SERS substrates. This proposed project open up a new possibility of ultrasensitive detection on PCBs and widen potential application of SERS-based sensoring.

表面增强拉曼散射(SERS)技术作为一种高灵敏、快速无损的分子检测手段具有广阔的应用前景。然而传统贵金属SERS基底始终存在灵敏度、稳定性、重现性等多性能难以平衡优化的矛盾。近年来，氧化石墨烯(GO)以其独特的物理化学性质在SERS应用领域备受关注。本项目拟设计、合成系列尺寸、形貌与粒子纳米间隙可控的各向异性金银纳米结构，以GO薄膜作为纳米空间层，构筑高效贵金属/GO三明治复合SERS基底。研究金属粒子种类、尺寸、形貌与GO空间层对基底等离激元性质以及SERS性能的影响规律；结合理论计算，系统研究三明治结构层内金属粒子以及层间粒子间的多重等离子体共振耦合对检测灵敏度的增强作用，最终揭示基底结构与其SERS性能的内在联系；探索三明治复合SERS基底对痕量持久性有机污染物多氯联苯（PCBs）的快速、直接、高灵敏检测。该课题拓展了SERS技术应用领域，为制备新型高效SERS基底提供新的思路。

多氯联苯(PCBs)、多溴联苯醚(PBDEs)等典型持久性环境有机污染物（POPs）分子，具有毒性强、易生物富集、难降解等特点，严重威胁人类健康和生态环境。因此，针对POPs的高灵敏检测及有效治理十分迫切。本项目针对POPs分子与传统贵金属基底表面吸附性能弱，拉曼散射截面低，拉曼检测信号灵敏度和重现性差等问题，利用氧化石墨烯(GO)或还原氧化石墨烯(rGO)优异的化学增强、分子富集和钝化保护作用，以GO或rGO作为纳米空间层，与高度各向异性金纳米星(AuNSts)、花状银(AgNFs)粒子复合，设计与制备了AgNFs-GO-AuNSts、AuNSt-GO-AuNSt高活性三明治SERS基底。实现了各层内、层间贵金属纳米粒子的多重等离子共振耦合作用，显著提高了SERS基底的灵敏度、信号可重现性和稳定性。对R6G检测限低至10^-13M，增强因子高达2.59×10^7；基于GO/rGO纳米空间层优异的钝化保护和分子富集作用，大大提高了三明治基底信号可重现性和稳定性 (信号偏差<7%)。更重要的是，无需修饰分子“捕捉剂”，通过π-π共轭作用将PCBs分子直接高效富集在强磁热点处，实现了对弱吸附持久性有机污染物如多环芳烃、多氯联苯、多溴联苯醚等的直接、快速、高灵敏检测，检测限低至10^-6M，增强因子高达1.93×10^5。并且实现了对PCBs混合溶液的特征性鉴别。在此基础上，以GO或rGO为介导，进一步优化各结构单元，将各向异性贵金属纳米结构与光催化性能优异的金属氧化物半导体TiO2、Cu2O相结合, 制备了TiO2@Au-rGO, Cu2O-GO-AuNSts多功能自清洁三元复合SERS基底，显著提高了基底光催化降解自清洁性能，同时实现了对多溴联苯醚的直接高灵敏检测和基底自清洁循环利用。