Single-walled carbon nanotubes wrapped poly-methyl methacrylate fiber optic sensor for ammonia, ethanol and methanol vapors at room temperature

Part of the outer layer of a commercial two-layer poly-methyl methacrylate optical fiber was mechanically removed and replaced with a coating of single-walled carbon nanotubes (SWCNT) by a dip-coating technique. The resulting fiber was used as a fiber optic sensor for the detection of ammonia, methanol and ethanol vapors in the concentration range 0–500 ppm at room temperature. Different thicknesses of the SWCNT layer on the fiber were prepared by repeated dip coating. All the sensors were found to show good response for all three vapors used even at lower vapor concentrations (<50 ppm). The results show that a lower SWCNT thickness is good for ammonia sensing whereas a higher thickness is good for alcohol sensing. The interaction between the analyte and SWCNT is responsible for the sensing of the volatile organic compounds.