The effect of purification of single-walled carbon nanotube bundles on the alcoholsensitivity of nanocomposite Langmuir–Blodgett films for SAW sensing applications

Abstract

HiPco (high-pressure CO dissociation process) single-walled carbon nanotube (SWCNT)bundles containing Fe particles were purified in a two-step purification process by thermalannealing in oxygen and post-treatment in HCl. Nanocomposite films of pristine andpurified SWCNTs embedded in an organic matrix of cadmium arachidate (CdA) wereprepared by a Langmuir–Blodgett (LB) molecular engineering technique with a fixedweight filler content of 75 wt% onto a surface acoustic wave (SAW) transducer operatingas an oscillator at a frequency of 433 MHz. The raw and purified samples werecharacterized at various stages of the purification process using thermogravimetricanalysis (TGA), high-resolution transmission electron microscopy (HR-TEM), alongwith energy-dispersive x-ray spectroscopy (EDS), field emission scanning electronmicroscopy (FE-SEM) and x-ray diffraction (XRD). Functional characterizations of theSWCNT–nanocomposite-based SAW sensors were investigated towards methanol,isopropanol and ethanol, and demonstrated high sensitivity, reversibility, fastresponse and ppm level detection at room temperature. Results indicate that thesensitivity of the SAW sensors based on a nanocomposite film of oxygen-annealedSWCNTs is enhanced to the alcohols tested at room temperature. Purification of theSWCNTs in the nanocomposite film affects the SAW sensitivity to alcohol bymodulating the sensing properties. The sensing mechanisms are analysed anddiscussed.