Selective acetate recognition and sensing using SWCNTs functionalized with croconamides

Abstract

Croconamides are a new class of dual-hydrogen bond donors that have attracted interest in anion recognition and sensing applications due to their strong H-bond donation capability. In this work, we report chemiresistive sensors for the detection of anions based on poly(4-vinylpyridine) (P4VP)-wrapped single-walled carbon nanotubes (SWCNTs) functionalized with croconamide-based selectors. Model structures of asymmetric N,Nsubstituted croconamide selectors with N,N-substitutional groups of alkyl cationic pyridinium and electronwithdrawing moieties such as aniline (6) and 3,5-bis(trifluoromethyl)phenyl (7) groups were synthesized and their binding affinities for various anions were characterized using UV-vis and 1H NMR titrations. Switchable binding of oxoanions was observed with selector 7, wherein HSO4- formed hydrogen bonding interactions and acetate (AcO-) induced deprotonation of the NH- protons of the croconamide. Large sensitivity transitions were obtained toward AcO- for both P4VP-6-SWCNT (S = 95.68 +/- 2.11 %) and P4VP-7-SWCNT (S =140.91 +/- 3.68 %) at 83.33 mM, which was attributed to deprotonation of the croconamide selectors upon addition of AcO-. Three serial sensors were assembled in a sensor array that rapid and selective screening of AcO- was demonstrated against other oxoanions such as HSO4- and H2PO4- in real-time.