Diazonium Salts: Versatile Molecular Glues for Sticking Conductive Polymers to Flexible Electrodes

Abstract

Adhesion of polymers to surfaces is of upmost importance in timely applications such as protective coatings, biomaterials, sensors, new power sources and soft electronics. In this context, this work examines the role of molecular interactions in the adhesion of polypyrrole thin films to flexible Indium Tin Oxide (ITO) electrodes grafted with aryl layers from various diazonium salts, namely 4-carboxybenzenediazonium (ITO-CO2H), 4-sulfonicbenzenediazonium (ITO-SO3H), 4-N,N dimethylbenzenediazonium (ITO-N(CH3)2), 4-aminobenzenediazonium (ITO-NH2), 4-cyanobenzenediazonium (ITO-CN) and 4-N-phenylbenzenediazonium (ITO-NHPh). It was demonstrated that PPy thin layers were adherent to these surfaces, whereas adhesion failure was noted on bare ITO, following simple solvent washing or sonication. Adhesion of the polypyrrole was investigated in terms of the hydrophilic/hydrophobic character of the underlying aryl layer as probed by contact angle measurements. It was found that sulfonic acid doped polypyrrole (PPy-BSA) thin films were preferably deposited on the most hydrophobic surfaces. More importantly, the redox properties and electrochemical impedance of PPy were closely related to the hydrophobic character of the aryl layers. This work demonstrates that diazonium compounds are unique molecular glues for conductive polymers, and permit to tune their interfacial properties. With diazonium-based robust, architectured interfaces, one can design high performance materials for e.g.sensors, printed soft electronics and flexible thermoelectrics.

A novel fluorescent sensor based on electrosynthesized benzene sulfonic acid‐doped polypyrrole for determination of Pb(II) and Cu(II)

“…Electrochemical experiments were performed in a single compartment three‐electrode glass cell at room temperature, using a SP‐150 scanning potentiostat (Bio‐Logic Science Instruments, Seyssinet‐Pariset, France). The working electrode was made of ITO (flexible, 25 μm thick ITO‐coated polyethylene naphthalate (PEN) sheets; ITO thickness 300 nm; sheet resistance of sheet resistance of 30‐50 Ω) . A stainless steel grid was used as counter‐electrode, and a saturated calomel electrode (SCE) was utilized as reference electrode.…”

Polypyrrole-Wrapped Carbon Nanotube Composite Films Coated on Diazonium-Modified Flexible ITO Sheets for the Electroanalysis of Heavy Metal Ions

“…We have previously reported the surface analysis of bare ITO and NH2-ITO electrodes [28,29,31]. Herein, we concentrate on CNT/NH2-ITO and PPy/CNT/NH2-ITO surfaces.…”

“…The main purpose of this work is to rationally modify flexible ITO electrodes with sensitive PPy films bearing embedded CNTs for the selective recognition of heavy metallic ions. We have previously demonstrated that excellent adhesion of PPy coating on flexible ITO required the use of coupling agents [28,29]. Otherwise, an immediate failure of the PPy coating occurred upon simple washing of the film with water.…”

Aldehyde-Mediated Protein-to-Surface Tethering via Controlled Diazonium Electrode Functionalization Using Protected Hydroxylamines

“…33 Methodologies to achieve a monolayer surface coverages from diazonium electro-grafting have been developed that are based on using sterically hindered aryl diazonium motifs, 34,35 radical scavengers, 36 and the application of short chronoamperometric pulses. 37,38 However, here, we utilize a phthalimide-deprotection approach that enables electrochemical functionalization of a variety of surfaces with a near-monolayer of hydroxylamine functionalities, as summarized in Scheme 3. The inspiration for this approach originates from the works of Hauquier 39 and Downard 40 et al, who reported the introduction of amine functionalities onto glassy carbon 39,40 and gold 39 electrodes via the immobilization of a diazonium molecule bearing a πcontaining protecting group on the amine moiety.…”