Hydrogen Sulfide Gas Sensor Based on Copper/Graphene Oxide Composite Film-Coated Tapered Single-Mode Fibre Interferometer

Abstract A hydrogen sulfide (H 2 S) gas sensor based on copper (Cu) nanoparticle deposited graphene oxide (GO) composite membrane with two waist-enlarged tapers is proposed. Three segments of the single-mode fibres (SMFs) are sequentially fused to obtain two waist-enlarged bitapers of Mach–Zehnder interferometer (MZI). When the light of a broadband light source transmits through the first bitaper, some light enters the fiber cladding; the lights of core mode and cladding mode are coupled at the second taper and an MZI is successfully fabricated. The copper/graphene oxide (Cu/GO) composite sensing film is coated on the surface of the second SMF, and the effective refractive index of the coating is changed when the sensitive film adsorbs the target gas. The correlation between the gas concentration and the wavelength shift is achieved and the H 2 S can be measured effectively. The results show that a uniform Cu/GO film is successfully coated on the surface of the fiber, and when the thickness of the sensitive film is about 1.2 μm, the sensor has a sensitivity of 4.42 pm/ppm and a good linearity and selectivity for H 2 S in the range of 0–60 ppm, and the limit of detection is 2.79 ppm. The response time and recovery time are approximately 31 and 48 s, respectively. The sensor has the advantages of small volume, low cost, simple structure, and easy manufacture and so on, which is suitable for on-line monitoring of H 2 S.