Low potential thiocholine oxidation at carbon nanotube-ionic liquid gel sensor

Low-potential thiocholine (TCh) detection was achieved at ionic liquid–multi-walled carbon nanotube (IL–MWCNT) modified electrodes. Cyclic voltammetry and amperometric characteristics of eight different thiocholine sensors were compared. With an oxidation potential between 0 and +50 mV (vs. Ag/AgCl) [EMIM][OTF]-, [EMIM][NTF2]-, [EMIM][TCB]- and [BMIM][BF4]–MWCNT gels offer a substantial decrease of the working potential comparing with other types of thiocholine sensors. Correlation between the physical properties and electrochemical behaviour of IL–MWCNT gels is also reported. Electrochemical impedance spectroscopy (EIS) and pH-dependence experiments suggest the existence of an electrostratic interaction between thiocholine and composite gels which favours the electrochemical reaction. The catalytical rate constant and the diffusion coefficient of thiocholine were calculated from chronoamperometric data. A very good sensitivity between 36 and 45 μA/mM cm2 was achieved for acetylthiocholine detection using selected gel-modified sensors.