Composite optical waveguide sensor based on porphyrin@ZnO film for sulfide-gas detection

Composite optical waveguide sensors show immense potential for the trace-level detection of harmful gases owing to their high sensitivity. Herein, we prepared a highly sensitive ZnO film/K+ ion-exchanged composite optical waveguide sensor by fixing a thin ZnO film layer on the surface of a K+ ion-exchanged glass optical waveguide. To study the influence of the preparation method on the gas sensitivity of the sensing element, 5,10,15,20-tetrakis-(4-methoxyphenyl)porphyrin was used as a sensing layer on the surface of the ZnO film and fixed via the spin-coating and immersion methods. The gas sensitivity of the sensors prepared by the two methods was comparatively studied. The sensor elements prepared by the immersion method showed higher sensitivity than those prepared by the spin-coating method. Furthermore, the reasons for the difference in the gas sensitivity are discussed in detail. The experimental results show that the as-prepared sensor can detect ppt levels of H2S and SO2 gases and has potential application in the detection of trace levels of sulfide gases in the environment and in industrial production.