Jean Pinson

Photografting enables the covalent modification of a wide variety of surfaces—including polymers, metals, carbons, and oxides—through irradiation of a deposited solution.

Controlling both the resorption rate and the formation of reactive oxygen species (ROS) of biodegradable iron (Fe) remains a central challenge for the fabrication of bioresorbable cardiovascular stents. Here, we introduce an innovative nanoengineered surface coating strategy to simultaneously accelerate Fe corrosion and suppress ROS generation without altering the bulk Fe materials. Aryl-diazonium salt chemistry (4-cyanobenzene diazonium tetrafluoroborate, DCN) was used to create robust polyaryl interphases that can immobilize gold nanoparticles (Au NPs) on Fe, establishing nanoscale microgalvanic and catalytic sites. Electrochemical analysis reveals that the coating increases the overall Fe corrosion rate while biasing the cathodic oxygen reduction reaction toward the four-electron pathway, thereby reducing peroxide/OH^• formation. This mechanism is supported by the remarkably reduced OH^• content detected by the terephthalate-probe assay. Corrosion metrics show a pronounced, controllable rate enhancement relative to bare Fe, and the postcorrosion exposure interfacial spectroscopy/microscopy verify the persistence of Au NPs, attributed to atomic Fe-FeO-Au interactions and anchoring by the DCN-derived polyaryl layer. Endothelial cell culture indicates favorable adhesion and viability, supporting cytocompatibility of the modified surface. This surface-chemistry-driven mechanism establishes a general interfacial principle for rate and pathway control of Fe biodegradation, offering a concise route to safer, faster resorbing Fe-based stents.

Understanding and controlling the reactivity of radical species remains a major challenge in many chemical reactions, with the goal of steering and precisely tuning key processes. Recognized as a simple and efficient method for the preparation of 2D nanomaterials, diazonium electrografting is a prime example of a functionalization technique that still requires deeper mastery to meet the demands of future bottom‐up approaches. In this work, supported by multiphysics simulations, we achieve an unprecedented understanding of the grafting mechanism involved in nitrobenzene diazonium electrografting and its impact on the resulting nanofilm composition. It is demonstrated that film growth arises from a competition between aryl and diazenyl radicals, leading to the incorporation of variable amounts of azo‐bridged nitrophenyl units. By implementing control strategies using radical scavengers and redox inhibitors, corroborated by simulations, we show that diazenyl radicals are preferentially grafted at the substrate/film interface rather than within the film structure itself. Finally, we demonstrate that selective trapping of aryl radicals over diazenyl radicals enables the formation of azo‐enriched films, thus opening the way for precise tuning of film composition and selective radical reactivity.

Arylazo sulfonates (Ar−N=N−SO₃Na) have been found to undergo photografting on gold surface through both Au−N_sp2− and Au−C_sp2− bond formation. The functionalized materials have been fully characterized by infrared reflection absorption spectroscopy (IRRAS), Raman, XPS, DFT calculations and UV‐Vis absorption spectroscopy. These methods permit to evidence aromatic substituents (IRRAS), the Au−N=N signature (Raman and XPS spectroscopy), and the bond dissociation energy values of the two linkages (DFT calculation). The grafting proceeds through two competitive paths, namely a stepwise reaction involving an aryl radical (for the formation of the Au−Ar bonds) and a concerted reaction on the surface of gold (for Au−N=N−Ar bond formation). The occurrence of an aryl radical upon irradiation has been fully evidenced by EPR spectroscopy. Finally,E/Zphotoisomerisation of the N=N bonds present on prepared few layer films has been observed by means of UV‐Vis absorption spectroscopy.

Historically, the irreversible reduction of aryldiazonium salts has provided a reliable method to modify surfaces, demonstrating a catalogue of suitable diazonium salts for targeted applications. This work expands the knowledge of diazonium salt chemistry to participate in surface electroinitiated emulsion polymerization (SEEP). The influence of concentration, electronic effects, and steric hindrance/regiochemistry of the diazonium salt initiator on the production of polymeric films is examined. The objective of this work is to determine if a polymer film can be tailored, controlling the thickness, density, and surface homogeneity using specific diazonium chemistry. The data presented herein demonstrate a significant difference in polymer films that can be achieved when selecting a variety of diazonium salts and vinylic monomers. A clear trend aligns with the electron-rich diazonium salt substitution providing the thickest films (up to 70.9 ± 17.8 nm) with increasing diazonium concentration and electron-withdrawing substitution achieving optimal homogeneity for the surface of the film at a 5 mM diazonium concentration.

The surface functionalization of silver nanoparticles (NPs) by Raman reporters has stimulated a wide interest in recent years for the design of Surface-Enhanced Raman Spectroscopy (SERS) labels. However, silver NPs are prone to oxidation and aggregation, which strongly limits their applications. The design of stable SERS tags based on Ag NPs still represents a major challenge for Raman bioimaging. We address this issue herein by taking advantage of aryl diazonium salt chemistry to obtain stable Ag NPs functionalized by multifunctional polyaryl layers bearing different Raman reporters (–NO₂, –CN, –CCH). The resulting SERS-encoded Ag NPs were characterized by UV-vis absorption, transmission electron microscopy (TEM) and SERS. The formation of multilayers at the surface of Ag NPs gives access to new spectrally distinguishable SERS codes thus broadening the library of available Raman tags. Proof-of-concept Raman imaging experiments were performed on cancer cells (HeLa) after NP uptake, highlighting the large potentials of diazonium salt chemistry to design Ag NPs-based SERS labels for Raman bioimaging.

Electrografting of different polymers on several materials is obtained without a primary layer attached to the surface (Surface-Polymer). This is achieved in the presence of a radical initiator, 2,6-dimethylbenzenediazonium, that is easily electrochemically reduced to an aryl radical, resulting in a simple one step process. In turn, IR, XPS, and electrochemical analysis provide proof of successful surface functionalization. The electrografting of carbon fibers is of particular interest as it permits improving the mechanical properties of carbon-epoxy composites. Different polymers were tested polymethyl methacrylate, poly1H,1H-perfluorooctyl methacrylate, polyglycidyl methacrylate, polyacrylic acid, poly(ethyleneglycol) diacrylate, vinylferrocene. The tensile strength and Young’s modulus are slightly improved and a 73% increase of the interfacial shear strength (IFSS) is observed with the fibers coated with PMMA.

We present two different molecular organizations obtained from octadecylamine (ODA) molecules on a highly oriented pyrolytic graphite (HOPG) surface: (i) self-organized physisorbed ODA molecules lying flat on the surface and (ii) a strongly electrografted compact crystalline monolayer of ODA molecules standing up on the surface. This new structure is obtained by combining the Langmuir–Blodgett transfer of an ODA Langmuir film onto HOPG with oxidative electrografting. The presence of an organic film on HOPG is characterized by attenuated total reflectance–infrared spectroscopy and Raman spectroscopy, while atomic force microscopy and scanning tunneling microscopy allow the observation of the two molecular organizations with adsorbed molecules lying flat on HOPG or strongly grafted in an upright position on the HOPG surface. Interestingly, the second molecular organization preserves a hexagonal symmetry and its lattice parameters are intermediate between those of ODA Langmuir films and that of the HOPG underlying surface. The functionalization of surfaces with organic films is a major issue in the design of sensors with biomedical applications or organic electronics and energy storage devices and these structures may find applications in these fields.