Versatile Wafer-Scale Technique for the Formation of Ultrasmooth and Thickness-Controlled Graphene Oxide Films Based on Very Large Flakes.

We present a new strategy to form thickness-adjusted and ultrasmooth films of very large and unwrinkled graphene oxide (GO) flakes through the transfer of both hemispherical and vertical water films stabilized by surfactants. With its versatility in terms of substrate type (including flexible organic substrates) and in terms of flake density (from isolated flakes to continuous and multilayer films), this wafer-scale assembly technique is adapted to a broad range of experiments involving GO and rGO (reduced graphene oxide). We illustrate its use through the evaluation of transparent rGO electrodes.

Localized reduction of graphene oxide by electrogenerated naphthalene radical anions and subsequent diazonium electrografting.

Herein, we describe a new localized functionalization method of graphene oxide (GO) deposited on a silicon oxide surface. The functionalization starts with the reduction of GO by electrogenerated naphthalene radical anions. The source of reducers is a microelectrode moving close to the substrate in a typical scanning electrochemical microscopy (SECM) configuration. Then, the recovery of electronic conductivity upon reduction enables the selective electrochemical functionalization of the patterns. The illustrative example is the electrografting of reduced-GO with a diazonium salt bearing a protonated amino group that can further immobilize gold nanoparticles by simple immersion. This study opens new routes for the construction of multifunctional patterned surfaces.

Contactless surface conductivity mapping of graphene oxide thin films deposited on glass with scanning electrochemical microscopy.

The present article introduces a rapid, very sensitive, contactless method to measure the local surface conductivity with Scanning Electrochemical Microscopy (SECM) and obtain conductivity maps of heterogeneous substrates. It is demonstrated through the study of Graphene Oxide (GO) thin films deposited on glass. The adopted substrate preparation method leads to conductivity disparities randomly distributed over approximately 100 µm large zones. Data interpretation is based on an equation system with the dimensionless conductivity as the only unknown parameter. A detailed prospection provides a consistent theoretical framework for the reliable quantification of the conductivity of GO with SECM. Finally, an analytical approximation of the conductivity as a function of the feedback current is proposed, making any further interpretation procedure straightforward, as it does not require iterative numerical simulations any more. The present work thus provides not only valuable information on the kinetics of GO reduction in mild conditions but also a general and simplified interpretation framework that can be extended to the quantitative conductivity mapping of other types of substrates.