n-Type gas sensing characteristics of chemically modified multi-walled carbon nanotubes and PMMA composite

Multi-walled carbon nanotubes (MWCNTs) were chemically modified with hydroxylamine hydrochloride salt and formed a composite with poly(methyl methacrylate) (PMMA). The morphology observations by scanning electron microscopy (SEM) showed that MWCNTs were well dispersed in the PMMA film. The electrical responses of the composite to methanol vapor were investigated. The composite exhibited a decreased resistivity upon exposure to the reducing methanol vapor, denoting an n-type response which was fast, reversible and reproducible at room temperature. In addition, the response was free from the interference of humidity. It is proposed that the n-type, instead of the usually observed p-type, response of the MWCNT based composite, which is supported by its decreased resistivity in the reducing NH3 vapor, is related to the modification of MWCNTs by the chemical treatment.