弹力作用下柔性透光衬底上高密度SERS热点结构的构建及其在光纤传感检测中的应用

In order to improve the poor detection reliability of surface-enhanced Raman scattering (SERS) substrates arising from maldistribution of hot spots and based on the fact that resolution of costly lithography is limited, this project proposed a new fabrication route based on the participation of elastic and transparent substrate in construction process of high-density hot spots. The self-assembly behavior of nanoparticles confined in the narrow space of sinusoid wrinkle template and the controlling ability of stretched elastic substrate during the assembly process of nanostructure will be majorly investigated. The influence of period and amplitude of sinusoid wrinkle template, concertration, size and Zata potential of Au nanoparticles as well as tension of elastic substrate on periodic assembly of single or multiple chains is planned to be explored. On the basis of close packing of nanoparticles within chains realized by confinement of template, distance between chains are adjusted under the assist of uniformly contraction of elastic substrate and LSPR coupling between chains are consequently achieved, leading to successful construction of high-density hot spots in quasi-two-dimensions and acquisition of SERS substrates with both high sensitivity and uniformity. Such flexible and transparent substrates could be easily integrated into optical fiber Raman probes. By combining high signal collective efficiency of commercial fiber probe and huge enhancement effect of high-density hot spots together, this kind of efficient SERS optical fiber probes exhibit extensive application prospects in the field of in-situ and trace detection.

本项目针对表面增强拉曼散射（SERS）基底中普遍存在的因热点结构分布不均匀而导致检测可靠性差的问题，基于光刻法成本昂贵、受分辨率限制的现状，提出了弹性透光PDMS衬底参与高密度热点结构构建过程的制备新路径，重点研究在正弦形褶皱模板的窄小空间中纳米粒子的自组装规律及衬底的弹性拉伸对组装结构的调控能力。探索正弦形褶皱周期、振幅及Au胶浓度、尺寸、Zata电位和PDMS衬底拉伸量对Au纳米颗粒单链及多链周期组装的影响。在利用褶皱模板的空间限制作用实现链内颗粒致密排列的基础上，借助弹性衬底的均匀收缩对链间距进行调控，实现链之间的LSPR耦合，构建了准二维的高密度热点结构，获得兼具高灵敏度和高均匀性的SERS基底。该柔性透光基底可方便地集成到光纤拉曼探头上，将商用光纤探头的高信号收集效率和高密度热点结构巨大的拉曼增强作用相结合，构成高效的SERS光纤传感探头，在原位、痕量检测领域有广阔的应用前景。

表面增强拉曼散射（SERS）技术具有无损、高灵敏等优点，在分子检测领域受到了越来越多的关注。近年来，柔性透光基底因可贴附在任意形状物体的表面，解决了硬质基底原位检测适用性差、集成困难等问题，而成为SERS领域的热门研究对象之一。围绕柔性透光衬底上高密度SERS热点结构的均匀构建及其在光纤传感检测中的应用，本项目在具有周期结构的PDMS衬底表面通过原位生长、无电电镀置换、蒸镀、弹性收缩等多种方法制备Ag或Au纳米结构，获得具有高活性、高均匀性和高重复性的柔性透光基底，并结合光纤拉曼成功实现水果表面目标分子的原位检测。研究结果显示，基于正弦形褶皱结构PDMS制备的Ag纳米结构，因高密度热点结构和3D周期结构的共同作用，其均匀性可达RSD仅为4.16%，且分别在苹果和橘子的表面实现了结晶紫和孔雀石绿的原位检测。利用AAO模板制备由Ag纳米颗粒构成的花瓣状结构基底，检测限可达0.975×10-10 mol/L，同时该基底具有很好的重复性和稳定性，在保存30天之后，RSD仍只有8.95%。借助弹力作用缩短Ag纳米颗粒间距、构建高密度热点结构，通过对拉伸形变量、Ag胶浓度及吸附时间等实验条件的优化，基底的增强因子达到6.97×107。以上研究结果表明，本项目通过多种方案制备的柔性透光SERS基底，其中的高密度热点结构赋予了基底高灵敏度、高均匀性和可靠性，在目标分子的原位、痕量检测领域具有广泛的实际应用前景。