常温下高灵敏度SPR氮氧化物微量气体传感器研究

Recently, surface plasmon resonance(SPR) technology has attracted intensive interest due to its potential application in the enhancement of the sensitivity of gas sensors. However, the mechanisms to capture active gas molecules and to expand the interaction distance between surface plasmon waves (SPWs) and gas molecules have not been fully investigated. The overall aim of the proposed research is to design and fabricate a novel optical SPR gas sensor based on Kretschmann prism with a high sensitivity, which is able to operate at room temperature. The advantages of the sensor are based on the absorbance at visible spectra of porphyrin molecules with adsorption of nitrogen oxide compounds, the gas permeability of porous titanium dioxide (TiO2) thin films and the sensitivity of SPR to the change of the refractive index. Maxwell equations will be exactly solved to describe the process of the generation, propagation and decay of SPW on the interface of the hybrid nanostructures. Distribution of the electromagnetic field in the hybrid system will be then obtained. Furthermore, the influence of incident angle and wavelength of inputting light, thickness of porous thin film on the resonant reflection spectrum will be analyzed, especially in some unusual optical phenomena such as energy transfer, slow group velocity, and mode splitting. The proposed sensor chip will be fabricated by RF magnetron sputtering and sol-gel method. A variety of techniques will be utilized to characterize hybrid nanofilms, such as ultraviolet visible (UV-Vis) spectroscopy, Fourier-transform infrared (FT-IR) spectrum and scanning electron microscopy (SEM). The experimental optical path to evaluate the performance of this nitrogen oxide SPR sensor will be set up. It is expected to achieve a high angular sensitivity (400o/RIU) at room temperature.

表面等离子体共振(SPR)技术用于提高气体传感系统的灵敏度已成为研究热点，但在如何捕捉活跃气体分子与扩大表面等离子体波与气体分子的作用深度方面的相关机理尚未明确。本课题将卟啉对氮氧化物气体分子的强吸收、纳米二氧化钛多孔薄膜的气体渗透性和SPR对折射率的敏感性结合起来，利用Kretschmann棱镜耦合结构，设计并制备一种在常温下具有较高灵敏度的SPR低浓度氮氧化物气体传感器。理论方面，严格求解麦克斯韦方程组，描绘表面等离子体波在复合纳米结构界面的产生、传播和衰减过程，得到光波在多层膜内的分布情况，进而分析入射角度、入射光波长、多孔膜厚度对共振反射谱的影响，重点是能量转移、低群速度、模式分裂等异常光学现象。实验方面，利用磁控溅射、溶胶凝胶方法制备出传感器芯片，将吸收、散射谱的测量同近场表征相结合，搭建面向目标分子的气敏性实验装置，完成验证性测量并实现室温下角度灵敏度达到400o/RIU。

基于表面等离子体共振(SPR) 的传感器因为具备高灵敏度、自由标签、快速响应、实时监测等优点, 在世界范围内持续受到关注。本项目在使用矢量分析方法求解麦克斯韦方程组的基础上，借助于传统光学结构(波导、光栅)研究了提高SPR传感器灵敏度以及分辨率的方法；实验上采用溶胶—凝胶法获得了优质的多孔ZnO介质薄膜，为基于SPR气体传感器的制备提供了前提条件；采用电子束蒸发方法制备了TiO2薄膜，研究了相变与退火温度之间的关系，由于不同相的TiO2薄膜具有不同的光学带隙和折射率，而SPR对周围介质的折射率又非常敏感此结果对于获得更为稳定的Ag-TiO2复合薄膜及传感应用研究具有重要的指导意义；制备了Ag粒子与ZnO以及Au粒子与TiO2的复合薄膜，进行了样品表征并测量了光谱响应，探索了气体敏感性，为深入地研究这种复合薄膜的局域表面等离子体共振(LSPR)传感性质奠定了前期基础。