Spectroelectrochemical operando method for monitoring a phenothiazine electrografting process on amide functionalized C-nanodots/Au hybrid electrodes

Phenothiazine derivatives are extensively explored dye molecules, which present interesting electrochemical and optical properties. In recent years, the possibility of transforming some phenothiazines in their aryl diazonium salt derivatives has been proved, what allows them to be electrochemically reduced and electrografted onto conductive surfaces. This is a smart way to modify these surfaces and enable them with specific functionalities. In order to better comprehend the electrografting process and consequently have a higher control of it, in this work we have carried out an exhaustive study by operando UV-Vis spectroelectrochemistry of the electrografting of a phenothiazine aryl diazonium salt onto amide carbon nanodots. As a model of phenothiazine dye we have chosen Azure A. The electrografting onto carbon nanodots has been stablished by comparison with the results obtained on bare gold electrodes in this novel study. The presence of carbon dots improves the reversibility of the electrochemical process as derived from the results obtained by operando UV-Vis spectroelectrochemistry. In addition, to asses that the electrochemical process studied corresponds to the electrografting, the results have been compared to those obtained for the simple Azure A adsorption. This study shows the advantages of obtaining simultaneously the electrochemical and the spectroscopic evolution of an electron-transfer process in a single experiment, in a particular electrochemical reaction. This work could be the starting point for the study of the electrografting on other nanomaterials. (C) 2018 Elsevier Ltd. All rights reserved.