Direct SECM Localized Electrografting of Vinylic Monomers on a Conducting Substrate

Localized electrografting of vinylic monomers in aqueous solution with micrometer resolution has been accomplished using scanning electrochemical microscopy (SECM). The SECM device was used in the direct mode, where the substrate acted as the cathodic working electrode and the ultramicroelectrode (UME) served as the anodic counter electrode in a classical three-electrode cell arrangement. The localized effect appeared when the protons reduction regime was obtained at the conducting substrate and in the same time when the oxidation of water was achieved at the UME. The different factors that determine the size and pattern of the electrografted coating were examined. The localization of the coatings, which were characterized by infrared spectroscopy in the reflection-absorption mode (IRAS), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and optical microscopy, was interpreted in terms of transportation modes of the reactive species, mainly supported by the migration effect rather than the diffusion effect. We have also demonstrated that the UME in the environment of a SECM device can be used as a pencil to direct the electrografting of organic film, which is of great interest for chemical, biological, or technical applications.