High-selectivity electrochemical non-enzymatic sensors based on graphene/Pd nanocomposites functionalized with designated ionic liquids

Nano-sized Pd particles are uniformly dispersed on graphene nanosheets (GNSs) using a supercritical-fluid-assisted deposition technique to increase the electrochemical sensing properties. The incorporation of different kinds of ionic liquid (IL) can increase the electrode sensing current toward different analytes. Butylmethylpyrrolidinium-bis(trifluoromethanesulfonyl)imide (BMP-TFSI) IL is beneficial for glucose detection, whereas the electrode with butylmethylpyrrolidinium-dicyanamide (BMP-DCA) IL shows high sensitivity toward ascorbic acid (AA). The selective detection of glucose or AA from their mixture is for the first time demonstrated using a non-enzymatic electrode with the aid of an IL. Angle-resolved X-ray photoelectron spectroscopy analyses indicate that GNSs can create an aligned cation/anion orientation in the adsorbed IL film, with the anions preferentially occupying the topmost surface. As a result, the electrode sensitivity and selectivity are mainly determined by the IL constituent anions.