Trace Carbon Monoxide Gas Sensor Based on PANI/Co3O4/CuO Composite Membrane-Coated Thin-Core Fiber Modal Interferometer

A novel fiber-optic carbon monoxide sensor based on a thin-core Mach-Zehnder fiber modal interferometer is presented and fabricated. This interferometer contains a short section of thin-core fiber spliced in two standard single-mode fibers, and the fast response to carbon monoxide is achieved via the construction of carbon monoxide sensing membrane on the outside surface of the thin-core fiber by using the dip-coating technique. The prepared sensing film is characterized by scanning electron microscopy, energy dispersion spectrum (EDS), spectroscopic analysis technology, and so on. Experimental results show that the thickness of the polyaniline (i.e., PANI)/Co ₃ O ₄ /CuO composite film, is about 360 nm with a compact and uneven appearance. The EDS indicates that the elements C, N, O, Cu, and Co are existed and agree well with the components of PANI/Co ₃ O ₄ /CuO. With the increasing concentration of carbon monoxide, the interference spectra appear blue shift. A high sensitivity of 2.87 pm/ppm and a good linear relationship are obtained within a measurement range from 0 to 70 ppm. In addition, there is an excellent selectivity for carbon monoxide. This interferometer has the advantages of high sensitivity and safety in flammable and explosive situations and could be used in the safety monitoring field of carbon monoxide gas.