A room temperature methanol vapor sensor based on highly conducting carboxylated multi-walled carbon nanotube/polyaniline nanotube composite

摘要

A novel room temperature methanol vapor sensor was fabricated by employing carboxylated multi-walled carbon nanotube/polyaniline nanotube (c-MWCNT/PAniNT) composite as the sensing element. The compounds, prepared by chemical oxidation polymerization of aniline, were characterized by Fourier transform infra-red spectroscopy, UV-vis absorption spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The nanocomposite showed superior electrical conductivity, as was evident from four-probe measurements, current-voltage relationship and cyclic voltammetry. c-MWCNT/PAniNT was tested as methanol sensing element using a simple two probe configuration, and its response was compared to that of pristine PAniNT. When exposed to methanol vapors, PAniNT forms hydrogen bonds with the methanol molecules, leading to a change in its resistance. This change was correlated with the response of the sensing element. The presence of c-MWCNT in the nanocomposite led to its exceptional sensitivity towards methanol as compared to pure PAniNT. However, its response gradually weakened with the exposure to higher alcohols. The proposed concept of hydrogen bonding, and diminished sensitivity towards ethanol and propanol was verified by density functional theory study.