The detection of 2,4,6-trinitrotoluene (TNT) is of significant importance for both security and environmental protection. TNT is among the most extensively utilized nitroaromatic explosives in military, mining, and industrial applications. Beyond its explosive characteristics, TNT and its reduction products exhibit toxic and carcinogenic properties, resulting in persistent contamination of soil and groundwater in areas associated with its manufacture and testing [1]. In recent years, ionic liquids (ILs) and poly(ionic liquid)s (poly(IL)s) have gained attention as electrolytes and membrane materials for explosives detection [2].
In this work, we explore a range of membranes based on ILs and poly(IL)s, with varying cation/anion combinations, for the electrochemical detection of TNT using gold thin-film electrodes. The influence of the IL anion/cation structure, as well as the incorporation of a polycation, on the TNT reduction behaviour was systematically examined through cyclic voltammetry (CV) measurements. Among the studied systems, [C2mim][TFSI]:p[DADMA][TFSI] and [C4mim][TFSI]:p[DADMA][TFSI], where [C2mim]+ = 1-ethyl-3-methylimidazolium, [C4mim]+ = 1-butyl-3-methylimidazolium, [TFSI]– = bis(trifluoromethylsulfonyl)imide and p[DADMA]+ = poly(diallyldimethylammonium), demonstrated an optimal balance between excellent electrochemical performance and high mechanical stability. Environmental studies under controlled oxygen (0-25 vol %) and humidity (up to 95% RH) environments revealed that the TNT response in real conditions is dependent on the membrane composition. These results highlight how ion-pair selection and environmental conditions jointly govern the charge transport and electrochemical behaviour in IL/poly(IL) membranes, providing key design principles for electrolytes in next-generation portable explosive sensors. The analytical performance of the sensing platform was evaluated using [C2mim][TFSI]:p[DADMA][TFSI] and [C4mim][TFSI]:p[DADMA][TFSI] membranes employing an ‘electrode surface-loaded with analyte’ detection strategy in which defined masses of TNT were deposited onto the electrode via solvent evaporation prior to performing electrochemical measurements.