Mapping fluxes of radicals from the combination of electrochemical activation and optical microscopy.
The coating of gold (Au) electrode surfaces with nitrophenyl (NP) layers is studied by combination of electrochemical actuation and optical detection. The electrochemical actuation of the reduction of the nitrobenzenediazonium (NBD) precursor is used to generate NP radicals and therefore initiate the electrografting. The electrografting process is followed in situ and in real time by light reflectivity microscopy imaging, allowing for spatio-temporal imaging with sub-micrometer lateral resolution and sub-nanometer thickness sensitivity of the local growth of a transparent organic coating onto a reflecting Au electrode. The interest of the electrochemical actuation resides in its ability to finely control the grafting rate of the NP layer through the electrode potential. Coupling the electrochemical actuation with microscopic imaging of the electrode surface allows quantitative estimates of the local grafting rates and subsequently a real time and in situ mapping of the reacting fluxes of NP radicals on the surface. Over the 2 orders of magnitude range of grafting rates (from 0.04 to 4 nm s(-1)), it is demonstrated that the edge of Au electrodes are grafted -1.3 times more quickly than their centre, illustrating the manifestation of edge-effects on flux distribution at an electrode. A model is proposed to explain the observed edge-effect, it relies on the short lifetime of the intermediate NP radical species.
CNRS UMR7195, ESPCI ParisTech,10 rue Vauquelin, 75231 Paris Cedex 05, France.
Sorin
S
Munteanu
Institut Langevin CNRS UMR 7587, ESPCI ParisTech, 1 rue Jussieu, 75238 Paris Cedex 05, France.
Jean Paul
JP
Roger
CNRS UMR7195, ESPCI ParisTech,10 rue Vauquelin, 75231 Paris Cedex 05, France.
Yasmina
Y
Fedala
FEMTO-ST Institute, CNRS-UMR 6174/UFC/ENSMM/UTBM, 24 chemin de l'Epitaphe, 25030 Besançon, France.
Fabien
F
Amiot
CNRS UMR7195, ESPCI ParisTech,10 rue Vauquelin, 75231 Paris Cedex 05, France.
Catherine
C
Combellas
Institut Langevin CNRS UMR 7587, ESPCI ParisTech, 1 rue Jussieu, 75238 Paris Cedex 05, France.
Gilles
G
Tessier
CNRS UMR7195, ESPCI ParisTech,10 rue Vauquelin, 75231 Paris Cedex 05, France.
Frédéric
F
Kanoufi
D055664:Electrochemical Techniques / Q000379:methods*; D004566:Electrodes; D008853:Microscopy / Q000379:methods*