基于金纳米粒子修饰碳纳米管阵列三维结构的光流控SERS微系统研究

There is an increasing demand for on-site detection of a variety of chemical and biological targets for many applications, including explosives for military and defense, sensitive detection of disease for health care, food contaminants, and toxins in our living environment. Surface-enhanced Raman scattering (SERS) is a sensing technique based on laser spectroscopy and plasmonic enhancement of metal nano structures.It has significant advantages compared to traditional Raman scattering. However, in spite of the tremendous power of SERS, it has had a limited impact outside of research laboratories due to the bulky and costly equipments and expensive substrates. Recently, the emergence of optofluidic approaches, defined the synergistic integration of photonics and microfluidics, prove to be effective for SERS performance while delivering the benefits of microsystems. However, these reported structures and systems require additional fabrication steps, utilizing a single nanochannel, complicated nanofabrication, less repeatable. In this project, we demonstrate an optofluidic SERS microsystem that utilizes three-dimensional gold nanoparticles decorated carbon nanotube arrays (CNTs/AuNP) as SERS substrate in a microfluidic channel to adsorb analyte. Carbon nanotube has huge surface area, leading to adsorb more gold nanoparticles as electromagnetic enhancement "hot spots", and more analyte molecules on the surface of gold nanoparticles to larger Raman scattering surface. Numerous micro/nano fluidic channels in CNTs/AuNP are formed, less clogging and high repeatability. A fiber optic cable is prealigned to the detection zone for excitation of the sample and collection of the scattered light, instead of alignment and focusing, simple, portable, high chip-to-chip repeatability. We will setup the theoretical model of three-dimensional CNTs/AuNP composite structure, including optical model, surface function model, surface-enhance Raman scattering model. Numerical analysis with three-dimension FDTD (Finite Difference Time Domain) will carried on, in order to gain optimized characteristics. The integration of the optofluidic micro system, three-dimension micro/nano structures and optical system will be discussed and analyzed, including the basic theory, design methods and key fabrication methods. Experimental studies will carry on for the detection of trace molecules. This combination of the optofluidic microsystem with three-dimension CNTs/AuNP without the need for complicated or costly fabrication will enable the system, to be low in cost and disposable, and to be applied in on-site detection.It has important scientific significance and application prospects.

面向痕量生物化学分子检测，以一种新型"金纳米粒子修饰碳纳米管阵列三维复合结构光流控表面增强拉曼散射微系统"为具体研究对象，创新提出将三维复合结构作为SERS增强基底，采用光纤耦合激励光和散射光的光流控微系统新思路。依据纳米光学、微纳电子学、光流控理论等研究三维复合结构的光学特性和表面增强拉曼散射增强机理；研究基于三维复合结构光流控SERS微系统设计原理、理论建模。依据光流控和微纳加工技术，研究三维复合结构、光纤耦合、光流控SERS微系统等三维一体化集成关键工艺和实现方法；开展其用于痕量化学生物分子等检测的实验研究。 该系统结合SERS和光流控技术，利用碳纳米管极大的比表面积、金纳米粒子电磁场增强"热点"、三维复合结构内在纳米通道、光纤耦合无需显微对准聚焦等特点，对实现高灵敏度、便捷式、在线式痕量分子检测具有重要研究价值和科学意义，在国防安全、食品安全、生命科学等领域具有广泛的应用前景。

以一种新型“金纳米粒子修饰碳纳米管阵列三维复合结构光流控SERS微系统”为具体研究对象，提出了以三维复合结构作为光流控SERS基底的创新思路，依据纳米光学、微纳电子基础理论、光流控理论等研究三维复合结构的光学特性和表面增强拉曼散射增强机理。主要创新工作有：（1）将碳纳米管与金属纳米粒子复合用于增强拉曼散射，从实验和理论仿真系统研究了CNTF-AgNPs复合结构SERS活性基底的表面形貌、拉曼增强特性、稳定性、均匀性等各种SERS性能。目前实现的指标：检测极限达到10^(-14) mol/L，增强因子达到10^10，有效寿命>1年，均匀性RSD<20%，具有一定的可重复利用性。（2）从实验和理论仿真上系统地对比研究了石墨烯/银纳米粒子的表面形貌、光学特性、拉曼增强特性、拉曼频移特性、均匀性（重复性）、稳定性和可重复利用性等，为提高SERS基底的灵敏度、重复性和稳定性等提供了一种简单、可靠、环保且低成本的方法。（3）研究了多种SERS基底（碳纳米管薄膜/AgNPs，石墨烯/ZnO，石墨烯/TiO2，石墨烯/ZnO/AgNPs，石墨烯/TiO2/AgNPs等）的光学特性、拉曼增强特性和拉曼探针测试实验等。采用化学合成方法将金属纳米粒子修饰到锥形光纤端面，制备光纤SERS探针；以R6G为待测分子，测试浓度低于10^(-9)Mol/L，增强因子10^8。（4）碳纳米管薄膜-银纳米颗粒复合基底集成到PDMS微通道内，采用简单的模塑法制备PDMS微通道，通过自然键合成完整的PDMS-玻璃微流控芯片。