Polydopamine functionalization of flexible electrochemical devices
Surface nanofunctionalization is an important tool to bring new chemical functionalities to carbon-based electrodes. Since the discovery of polydopamine, it has been widely applied in materials science due to its simplicity and versatility. However, little attention has been given to prepare nanofunctionalized surfaces for flexible electrochemical paper-based devices. After fabricating the electrodes on paper substrates, polydopamine was formed over the surface of the working electrode using the chemical polymerization route. Polydopamine nanofilms (6 nm thick) on carbon were characterized by contact angle, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy (topography and electrical measurements) and electrochemical techniques. After the nanofunctionalization it was observed that the presence of polydopamine nanofilm introduces oxygen and nitrogen-rich functionalities (R-NH2 and R-C=O) that decrease the contact angle of the electrode (72° to 48°C). Moreover, polydopamine nanofilms did not block the heterogeneous electron transfer. In fact, in this work it was observed one of the highest standard heterogeneous rate constants for electrochemical paper-based electrodes (1,4 x 10-3 cm s-1). In addition, functionalized electrodes exhibited two redox peaks in the cyclic voltammograms that can be ascribed to catechol/quinone redox pair.