SPR based fibre optic ammonia gas sensor utilizing nanocomposite film of PMMA/reduced graphene oxide prepared by in situ polymerization

Abstract

Surface plasmon resonance (SPR) based fibre optic gas sensors using nanocomposite film based on poly(methyl methacrylate) [PMMA], reduced graphene oxide (rGO) and PMMA/rGO nanocomposites having varying amounts of rGO are presented. The sensing probes were prepared by depositing copper film onto unclad portion of the optical fibre followed by coating of PMMA, PMMA/rGO nanocomposite over-layer. The sensing abilities of the probes were tested for gases like ammonia, hydrogen sulphide, chlorine, hydrogen and nitrogen. The SPR rGO and spectra of all the three types of the sensors for different concentrations of gases were determined using wavelength interrogation technique. Experimental results of SPR spectra showed a red shift in the resonance wavelength on increase in the concentration of gases in the chamber. It was found that the probes were more sensitive to ammonia gas. Further, the probe having PMMA/rGO nanocomposite over-layer coating was found to be more sensitive than the other two. For achieving maximum sensitivity, the performance of the probe with different doping concentrations of reduced graphene in the nanocomposite was evaluated. The sensor has the advantages of high sensitivity, wider operating range, reusability and reproducibility of results which make the sensor compatible for practical applications. Further, the probe was fabricated on optical fibre and hence it has additional advantages such as probe miniaturization, low cost, capability of online monitoring and remote sensing and immunity to electromagnetic field interference.