Highly sensitive and disposable screen-printed ionic liquid/graphene based electrochemical sensors

Abstract

In this work, a highly sensitive and disposable screen-printed ionic liquid-graphene electrode (SPIL-GE) was developed for electrochemical sensing. The paste for screen printing was facilely prepared by mixing IL with electrolytically exfoliated graphene in poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (GP/PEDOT/PSS) and carbon paste (CP) via ball milling. The IL-GP paste was then screen printed to form working and counter electrodes (WE & CE) followed by screen printing of Ag/AgCl reference electrode and insulator layer on a polyethylene substrate. Electrode geometries were optimized for electrochemical sensing, arriving at an optimal design with an overall electrode length of 25 mm, and CE and WE active areas of 15.70 and 12.57 mm2, respectively. SPIL-GEs employing six ILs with imidazolium and pyridinium cations were assessed for electrochemical sensing of K3Fe(CN)6. The pyridinium-type IL, namely 3-methyl-1-propylpyridinium bis(trifluoromethyl sulfonyl)imide (PMPlm), was found to exhibit the highest CV peak currents compared with other ILs at an optimal PMPlm content of 1.0% (w/w). Characterization with scanning electron microscopy and Fourier-transform infrared spectroscopy confirmed the presence of PMPlm, GP/PEDOT/PSS and CP in SPIL-GEs. The electrochemical performance of the optimal SPIL-GE towards the three common analytes including ferri/ferro cyanide (Fe(CN)6)3-/4- redox couple, dopamine and hydroquinone were compared with the screen-printed carbon and graphene electrodes (SPCE & SPGE). From the results, the SPIL-GE demonstrated larger anodic currents with lower oxidation potentials for the three analytes than SPGE and SPCE, respectively. Therefore, the SPIL-GE could be a potential candidate for advanced electrochemical sensing applications.