Jean-François Bergamini

Electrografting of calix[4]arenediazonium salts to form versatile robust platforms for spatially controlled surface functionalization

An essential issue in the development of materials presenting an accurately functionalized surface is to achieve control of layer structuring. Whereas the very popular method based on the spontaneous adsorption of alkanethiols on metal faces stability problems, the reductive electrografting of aryldiazonium salts yielding stable interface, struggles with the control of the formation and organization of monolayers. Here we report a general strategy for patterning surfaces using aryldiazonium surface chemistry. Calix[4]tetra-diazonium cations generated in situ from the corresponding tetra-anilines were electrografted on gold and carbon substrates. The well-preorganized macrocyclic structure of the calix[4]arene molecules allows the formation of densely packed monolayers. Through adequate decoration of the small rim of the calixarenes, functional molecules can then be introduced on the immobilized calixarene subunits, paving the way for an accurate spatial control of the chemical composition of a surface at molecular level.

Vinylogous Tetrathiafulvalene Based Podands: Complexation Interferences on the Molecular Movements Triggered by Electron Transfer

Substituted vinylogous tetrathiafulvalenes (TTFVs) containing two freely moving polyoxyethyl chains were prepared. Investigations of their redox behaviors in organic solvent show that these TTFV could efficiently complex metallic dications such as Pb(2+) or Ba(2+), leading to considerable modifications of their electrochemical response. As main feature, the molecule senses the association between the TTFV core and the metallic dication through a modification of the molecular motion triggered by the electron transfer. The complexation creates a link between the two parts of the TTFV core, causing considerable changes in the nature of the molecular motion. The resulting behavior is totally unusual as the 2-positively charged TTFV(2+) appears to present the highest association constants with the metallic dication.

The cathodic behaviour of poly(alkyl) and (aryl) sulfones revisited. Mechanistic and theoretical approaches

A series of aromatic sulfones activated by 2, 3 or 4 sulfonyl groups were reduced electrochemically in aprotic media. The electrochemical behaviour is strongly directed by the nature and the number of the substituents bound to the aromatic ring. From the analyses of cyclic voltammetry experiments, the kinetics and thermodynamic parameters were evaluated for each system and a theoretical study at the B3LYP/6-31G* level was performed simultaneously to understand the reactivity of the radical anions stemmed from these aromatic sulfones.

Grafting of Oligo(ethylene glycol) Functionalized Calix[4]arene-tetra-diazonium Salts for Antifouling Germanium and Gold Surfaces

Biosensors that can determine protein concentration and structure are highly desired for biomedical applications. For the development of such biosensors, the use of Fourier transform infrared (FTIR) spectroscopy with the attenuated internal total reflection (ATR) configuration is particularly attractive, but it requires appropriate surface functionalization of the ATR optical element. Indeed, the surface has to specifically interact with a target protein in close contact with the optical element and must display antifouling properties to prevent nonspecific adsorption of other proteins. Here, we report robust monolayers of calix[4]arenes bearing oligo(ethylene glycol) (oEG) chains, which were grafted on germanium and gold surfaces via their tetradiazonium salts. The formation of monolayers of oEGylated calix[4]arenes was confirmed by AFM, IR, and contact angle measurements. The antifouling properties of these modified surfaces were studied by ATR-FTIR spectroscopy and fluorescence microscopy, and the nonspecific absorption of bovine serum albumin was found to be reduced by 85% compared to that of unmodified germanium. In other words, the organic coating by oEGylated calix[4]arenes provides remarkable antifouling properties, opening the way for the design of germanium- or gold-based biosensors.

Reductive electrografting of in situ produced diazopyridinium cations: Tailoring the interface between carbon electrodes and electroactive bacterial films

Carbon electrodes were functionalized through the reduction of diazopyridinium cations that are produced from in situ diazotization of 2-, 3- and 4-aminopyridine. Diazopyridinium salts were much more rarely employed for surface functionalization than other aryldiazonium derivatives. A study combining X-ray Photoelectron Spectroscopy (XPS), contact angle, ellipsometry, Atomic Force Microscopy (AFM) measurements and electrochemical analyses demonstrates that films obtained from 4-diazopyridinium cations are hydrophilic, dense, compact but sufficiently thin to preserve fast electronic transfer rate, being then relevant to efficiently tailor the interface between the anode surface and an electroactive biofilm. Microbial Fuels Cells (MFCs) with pyridine-functionalized graphite anodes exhibit faster development and improved performances than MFCs operating with bare graphite anodes.