Qi Zhi-Mei, Honma Itaru, Zhou Haoshen
Light and Control Research Group, PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan.
Anal Chem. 2006 Feb 15;78(4):1034-41. doi: 10.1021/ac051380f.
Chemical gas sensors that employ integrated optical polarimetric interferometry were fabricated by the sol-gel synthesis of transparent mesoporous thin films of TiO2-P2O5 nanocomposite on tapered layers of TiO2 sputtered on tin-diffused glass waveguides. Atomic force microscopy images of the mesoporous thin film clearly show the open pore mouths on the film surface that favor rapid diffusion and adsorption of gas-phase analytes within the entire film. Adsorption of gas and vapor induces changes (Deltan) in the refractive index of the mesoporous thin film that lead to shifts in the phase difference between the fundamental transverse electric and magnetic modes simultaneously excited in the glass waveguide via single-beam incidence. Upon exposure to NH3 gas at concentrations as low as 100 ppb in dry air at room temperature, the sensor exhibits a reversible change in the phase difference with the response and recovery times of less than 60 and 90 s, respectively. It is unexpected that the sensor is unresponsive to either NO2 or C6H6 vapor, leading to a somewhat selective sensitivity to NH3. Determination of Deltan was carried out with a combination of the experimental results and the theoretical calculations. The sensor design represents a novel, effective, and easily accessible approach to mesoporous thin-film-based integrated optical chemical sensors.
通过在溅射在锡扩散玻璃波导上的TiO₂锥形层上溶胶 - 凝胶合成TiO₂ - P₂O₅纳米复合材料的透明介孔薄膜，制备了采用集成光学偏振干涉测量法的化学气体传感器。介孔薄膜的原子力显微镜图像清楚地显示了薄膜表面的开放孔口，有利于气相分析物在整个薄膜内的快速扩散和吸附。气体和蒸汽的吸附会引起介孔薄膜折射率的变化（Δn），这会导致通过单光束入射在玻璃波导中同时激发的基本横向电模和磁模之间的相位差发生偏移。在室温下干燥空气中暴露于低至100 ppb浓度的NH₃气体时，该传感器的相位差会发生可逆变化，响应时间和恢复时间分别小于60秒和90秒。出乎意料的是，该传感器对NO₂或C₆H₆蒸汽均无响应，从而对NH₃具有一定的选择性灵敏度。通过结合实验结果和理论计算来确定Δn。该传感器设计代表了一种基于介孔薄膜的集成光学化学传感器的新颖、有效且易于实现的方法。
