Surface Plasmon Resonance-Based Fiber Optic Methane Gas Sensor Utilizing Graphene-Carbon Nanotubes-Poly(Methyl Methacrylate) Hybrid Nanocomposite

Fabrication and characterization of a surface plasmon resonance (SPR)-based fiber optic sensor using graphene-carbon nanotubes/poly(methyl methacrylate) (GCNT/PMMA) hybrid composites for the detection of methane gas have been carried out. Four kinds of probes with different over-layers on the silver-coated unclad core of the fiber have been fabricated to achieve the best performance of the sensor. The over-layers used are of reduced graphene oxide (rGO), carbon nanotubes (CNT), reduced graphene oxide-carbon nanotubes (GCNT), and GCNT/PMMA hybrid nanocomposite. The sensing ability of all the probes has been tested for the following gases: methane, ammonia, hydrogen sulfide, chlorine, carbon dioxide, hydrogen, and nitrogen. The SPR spectra of all the probes for different concentrations of gases have been determined. A red shift in the resonance wavelength has been observed with increasing concentration of gases around the probes. Out of all the probes, the one with GCNT/PMMA hybrid nanocomposite over-layer has been found to be highly selective towards methane gas. For maximum sensitivity, the performance of the probe has been evaluated using different doping concentrations of GCNT in GCNT/PMMA nanocomposite. The doping concentration of 5 wt.% has been found to give maximum sensitivity of the sensor. Since the probe has been fabricated on optical fiber, apart from high selectivity and sensitivity, it has additional advantages such as miniaturized probe, low cost, capability of online monitoring and remote sensing, and immunity to electromagnetic field interference.