Tailoring selectivity of sprayed carbon nanotube sensors (CNT) towards volatile organic compounds (VOC) with surfactants

The vapour sensing performances of various surfactant-carbon nanotube (CNT) sensors fabricated by spray layer by layer (sLbL) towards various VOC including eleven lung cancer biomarkers have been investigated. It is found that changing the surfactants' nature allows to efficiently tailor both the selectivity and the sensitivity of CNT vapour sensors to detect specifically some VOC biomarkers of lung cancer. An original boosting effect of chemo-resistive responses has also been evidenced and assumed to result from the combined expansion of surfactant molecules directly sheathing CNT at junctions and of those organised in micelles in the vicinity of CNT, upon analytes' diffusion. The performances of surfactant-CNT sensors, hierarchically structured by sLbL with sodium deoxycholate (DOC), sodium dodecylbenzenesulfonate (SDBS), 1-hexadecyl trimethyl ammonium bromide (CTAB), benzalkonium chloride (BnzlkCl), and triton (R) x-405 (TX405) were found to depend on the interactions of the surfactants with the analytes, on their supramolecular assembly with CNT but also on the initial resistance R-0 that can be adjusted by CNT content, surfactant: CNT ratio or the surfactant concentration over its CMC. CNT-DOC sensors were found sensitive to methanol and other alcohols but also water. TX405-CNT sensors were found sensitive to benzene, n-pentane and chloroform. SDBS-CNT sensors could detect ethanol, acetone, chloroform and water but not much biomarkers, excepted isopropanol. BnzlkCl-CNT sensors were sensitive to n-pentane, isoprene, acetone and ethanol. CTAB-CNT sensors were slightly sensitive to most VOC but did not show any strong selectivity, whereas pristine CNT sensors were found to be good to detect most aromatic VOC of the set. Moreover it is remarkable that the technique of fabrication used here is almost exclusively based on eco-friendly aqueous solutions of CNT. (C) 2015 Elsevier B.V. All rights reserved.