Selective acetate detection using functional carbon nanotube fiber

Abstract

We developed a chemiresistive anion sensor using highly conductive carbon nanotube fibers (CNTFs) functionalized with anion receptors. Mechanically robust CNTFs were prepared via wet-spinning utilizing the nematic liquid crystal properties of CNTs in chlorosulfonic acid (CSA). For anion detection, polymeric receptors composed of dual-hydrogen bond donors, including thiourea 1, squaramide 2, and croconamide 3, were prepared and bonded non-covalently on the surface of the CNTFs. The binding affinities of the anion receptors were studied using UV–vis titrations. The results revealed that squaramide 2 exhibited the highest binding affinity toward AcO– , followed by thiourea 1 and croconamide 3. This trend was consistent with the chemiresistive sensing responses toward AcO– using functional CNTFs. Selective anion sensing properties were observed that CNTFs functionalized with squaramide 2 exhibited a response of 1.08% toward 33.33 mM AcO– , while negligible responses (<0.1%) were observed for other anions such as Cl– , Br–, and NO3–. The improved response was attributed to the internal charge transfer of dual-hydrogen bond donors owing to the deprotonation of the receptor upon the addition of AcO–