Dithienylpyrrole Electrografting on a Surface through the Electroreduction of Diazonium Salts

Abstract

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.

Electrochemical and Plasmon‐induced Grafting of n‐Dopable π‐Conjugated Oligomers

“…Sweeping the potential from −0.4 to 1.1 V also shows no electrochemical signal and underlines the strong homogeneity of the layer with no significant pinholes. This behavior is in marked contrast with those observed on grafted layers incorporating thiophene, pyrrole, EDOT or aniline [27,47–50,63] . Indeed, on these electrodes the probe is irreversibly oxidized.…”

“…This behavior is in marked contrast with those observed on grafted layers incorporating thiophene, pyrrole, EDOT or aniline. [27,[47][48][49][50]63] Indeed, on these electrodes the probe is irreversibly oxidized. This diode-like signal is the signature of a conductive switch of the grafted layer, and indicates that the oligomers can be p-doped at potentials below 1 V/SCE.…”

“…[43][44][45][46] Diazonium salts can be generated in situ from many amino aromatic precursors, and a wide variety, bearing various functionalities, has been used. When they incoporate thiophene, [47,48] ethylenedioxythiophene, [49] pyrrole [50] or aniline [27] moieties, π-conjugated oligomers, incorporating these electron-rich aromatic units, covalently grafted on surfaces, are obtained. The grafted layers are electroactive at positive potential and the oligomers can be easily p-doped at potentials which depend on their molecular structure.…”

Electrochemically deposited molecular thin films on transparent conductive oxide substrate: combined DC and AC approaches for characterization

“…[26][27][28] One can control the thickness of the molecular layer by varying various grafting conditions such as concentration of diazonium salts, cyclic voltammetry scan rate, number of cycles, onset, and final potential, etc. [29][30][31] In this context, the McCreery group and others have also successfully demonstrated the utility of this technique in forming the ultra-thin film and its further applications in molecular electronics. [32][33][34][35][36] So far, the reported literature of e-chem grafting of aryl diazonium is more concentrated to glassy carbon, sp 2 conducting carbon, Au, copper, and iron; very few reports are present with ITO.…”