Experimental and computational studies of the interactions between carbon nanotubes and ionic liquids used for detection of acetaminophen

Abstract

The interactions between multi-walled carbon nanotubes and different amounts of an ionic liquid (IL), as well as the interactions between this system (used as electrochemical sensor) and acetaminophen (ACOP), were investigated through both experimental and theoretical methodologies. Experiments indicated that there is an optimal concentration of ionic liquid for ACOP detection. A host of techniques and model systems were employed to investigate the adsorption and oxidation processes. To investigate the source of the increased electrochemical current in the presence of an IL, we computed the adsorption energy values of ACOP in the nanotube – IL system via Monte Carlo simulations and Density Functional Theory (DFT). DFT allowed us to explore the changes in adsorption energy due to oxidation. Our theoretical results support the experimental findings that moderate amounts of IL modulates ACOP/ACOP+ adsorption, pointing to a cooperative effect that tends to wane with increasing amounts of IL pairs. We observed that the IL favors desorption of the oxidized species and facilitates charge transfer from the ACOP to the nanotube. Therefore, our studies point towards multifactorial effects with clear physical basis that modulates binding leading to an optimal ratio to promote ACOP detection.