Fiber optic hydrogen sulfide gas sensors utilizing ZnO thin film/ZnO nanoparticles: A comparison of surface plasmon resonance and lossy mode resonance

Abstract

Fabrication and characterization of fiber optic sensors employing surface plasmon resonance (SPR) and lossy mode resonance (LMR) for the detection of hydrogen sulfide gas have been carried out. Three kinds of probes, two utilizing LMR technique and the one utilizing SPR technique, have been fabricated over unclad core of the fiber using zinc oxide (ZnO). The first LMR probe, named as LMR 1, has been fabricated by coating ZnO thin film with an over layer of ZnO nanoparticles while the second LMR probe, named as LMR 2, has a layer of ZnO nanoparticles over the unclad core of the fiber. The third probe, named as SPR probe, has been fabricated by coating silver film and a thin over layer of ZnO over unclad core of the fiber. The variation of peak absorbance/resonance wavelength with the concentration of the hydrogen sulfide gas has been used to calibrate all the three sensors having different platforms. The results show the maximum sensitivity to H2S gas for LMR 1 probe while the minimum for the SPR probe. In addition, the LMR 1 probe is highly selective to hydrogen sulfide gas in comparison to other two probes. This has been confirmed by performing experiments using different gases. The LMR 1 sensor probe has number of advantages, in addition to high sensitivity and selectivity, such as low cost, miniaturized probe, fast response, reusability of the probe, capability of online monitoring and remote sensing.