Electrochemical and Theoretical Study of π-π Stacking Interactions between Graphitic Surfaces and Pyrene Derivatives

In this study, the reversibility of pi-pi stacking interactions at graphite electrodes (GE) of pyrene, 1-aminopyrene, 1-pyrenecarboxylic acid, and doxorubicin hydrochloride (DOX) have been studied. The adsorption and desorption of these pi-orbital-rich molecules was characterized using X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The experimental investigations were complemented with a density functional theory study of the interaction between these it-orbital-rich molecules and graphite. It was demonstrated that the charged pyrene derivatives could be electrochemically desorbed from the graphitic surfaces, when a sufficiently high potential of the same charge as the pyrene derivative, was applied to the electrode. The duration of the applied potential, the pH and the magnitude of the applied potential during potential pulsing were found to be important with regards to the desorption efficiency. Up to 90% of charged pyrene derivatives could be removed from the electrode surface within 60 s via potential pulsing. However, these parameters produced insignificant effects on neutral pyrene bound to the graphite. A potential application of this electrochemically induced desorption of pi-rich species in drug delivery was demonstrated via the release of adsorbed doxorubicin (DOX).