Pure and Iso-Butyl Methyl Ketone Treated Multi-Walled Carbon Nanotubes for Ethanol and Methanol Vapor Sensing

Multi-walled carbon nanotubes (MWCNTs) coated intensity modulated fiber optic sensor for the detection of ethanol and methanol vapors at room temperature is reported. Pure, 30 and 60 min iso-butyl methyl ketone (IBMK) treated MWCNT were coated on cladding removed polymethyl methacrylate fiber by the dip coating technique. The pure and IBMK treated MWCNT coated fibers were used as sensors. Response of the sensors was studied by measuring the change in output light intensity for different methanol and ethanol vapor concentrations in the range of 0-500 ppm. The 60 min IBMK treated MWCNT coated sensor showed 2 and 3.4 fold increase in the sensitivity for methanol and ethanol vapors at 640 and 630 nm wavelengths light, respectively, compared with the pristine MWCNT coated sensor. Fourier transform infrared spectroscopy confirmed the attachment of C=O functional group in IBMK treated MWCNT. Thermogravimetry results reveal the functionalized nanotubes decomposed at 475 °C after the elimination of attached functional groups. The pristine nanotubes start to decompose at 540 °C. The randomly oriented nanotubes layer of average thickness 1.5 μm on the cladding modified fiber is observed from scanning electron microscope images.