The Influence of Organic-Film Morphology on the Efficient Electron Transfer at Passivated Polymer-Modified Electrodes to which Nanoparticles are Attached

The cyclic voltammograms of tris (2,2′-bipyridyl) iron(II) ([Fe(bpy)3]2+) adsorbed in clay-modified electrodes made from a range of different smectites were recorded. In all cases, at low scan speed (1 mV/s), the initial anodic peak current was much larger than the initial cathodic peak current. Partial reduction of the clay structural iron further increased the initial anodic to cathodic current ratio, suggesting that the discrepancy between the charge transferred in the anodic and cathodic scans was due to a slow electron transfer between the clay structural Fe(II) and the oxidized bipyridyl cations. However, no clear quantitative relation was found between the measured FeO contents of the different clays and the observed excess anodic currents. In fact, of all the clays tested only one, montmorillonite SWy-1, contained enough Fe(II) for it to account for all of the excess anodic charge transferred in the initial scan.

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Dithienylpyrrole Electrografting on a Surface through the Electroreduction of Diazonium Salts

Electrochem ◽

10.3390/electrochem1010003 ◽

2020 ◽

Vol 1 (1) ◽

pp. 20-31

Author(s):

Thi Huong Le ◽

Van Quyen Nguyen ◽

Gaelle Trippe-Allard ◽

Jean-Christophe Lacroix ◽

Pascal Martin

Keyword(s):

Electron Transfer ◽

Redox Potential ◽

Diazonium Salts ◽

Organic Thin Film ◽

Organic Film ◽

Aniline Derivative ◽

Standard Redox Potential ◽

Key Issues ◽

Adhesion Process

The control of the interface and the adhesion process are key issues for the development of new application based on electrochromic materials. In this work the functionalization of an electrode’s surface through electroreduction of diazonium generated in situ from 4-(2,5-di-thiophen-2-yl-pyrrol-1-yl)-phenylamine (SNS-An) has been proposed. The synthesis of the aniline derivative SNS-An was performed and the electrografting was investigated by cyclic voltammetry on various electrodes. Then the organic thin film was fully characterized by several techniques and XPS analysis confirms the presence of an organic film based on the chemical composition of the starting monomer and allows an estimation of its thickness confirmed by AFM scratching measurements. Depending on the number of electrodeposition cycles, the thickness varies from 2 nm to 10 nm, which corresponds to a few grafted oligomers. In addition, the grafted film showed a good electrochemical stability depending on the scan rates up to 400 V/s and the electrochemical response of the modified electrode towards several redox probes showed that the attached layer acts as a conductive switch. Therefore, the electrode behaves as a barrier to electron transfer when the standard redox potential of the probe is below the layer switching potential, whereas the layer can be considered as transparent towards the electron transfer for redox probes with a redox potential above it.

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