This critical review summarizes existing knowledge on the use of diazonium salts as a new generation of surface modifiers and coupling agents for binding synthetic polymers, biomacromolecules, and nanoparticles to surfaces. Polymer grafts can be directly grown at surfaces through the so-called grafting from approaches based on several polymerization methods but can also be pre-formed in solution and then grafted to surfaces through grafting onto strategies including “click” reactions. Several routes are also described for binding biomacromolecules through aryl layers in view of developing biosensors and protein arrays, while the use of aryl diazonium coupling agents is extended to the attachment of nanoparticles. Patents and industrial applications of the surface chemistry of diazonium compounds are covered. This review stresses the paramount role of aryl diazonium coupling agents in adhesion, surface and materials sciences (114 references).

Vitrimers, in stringent contrast to dissociative networks, involve associative covalent exchanges and remain fully cross-linked at all temperatures. However, we have previously reported on poly(1,2,3-triazolium) dynamic networks that exhibit linear rheological characterization indistinguishable from vitrimers although being based on a dissociative covalent exchange process, i.e., de-N-alkylation and re-N-alkylation reactions. Herein, we highlight the main features of dissociative and associative covalent adaptable networks (CANs) and discuss their respective linear rheological behaviors. After giving a detailed overview of the extent and potential of dynamic polymer networks having 1,2,3-triazolium cross-links in particular and CANs involving trans-N-alkylation exchanges in general, we perform a detailed rheological comparative characterization of previously described aliphatic 1,2,3-triazolium-based dynamic networks and a new bicomponent thermosetting system issued from the mixing of linear polystyrene chains having complementary benzyl iodide and 1,2,3-triazole pendent groups. We propose a simple but comprehensive rheological characterization methodology that enables proper comparison between all types of CANs, i.e., vitrimers and dissociative networks. Owing to the combination of a high glass transition temperature dynamic network and fast trans-N-alkylation exchanges in this new dissociative network, it is possible to characterize both glass transition and network relaxation with single rheological experiments. We provide clear experimental evidence that although located within a narrow temperature range, the temperature dependences of these two transitions are distinct and follow WLF and Arrhenius models, respectively.

Background: Carbon dots (CDs) are of particular interest in numerous applications. However, their efficiency for heavy metal removal from wastewater was not yet reported. Herein, we rationally synthesized CDs from petroleum coke waste via hydrothermal treatment in the presence of ammonia. Results: This drove the formation of outstanding photoluminescent, water-soluble, biocompatible, and high yield of monodispersed sub-5 nm CDs. The CDs are co-doped with high 10% of N and 0.2% of S. The as-prepared CDs possess unprecedented photoluminescent properties over broad pH range making these dots unique efficient pH sensor. Conclusions: Chitosan (CH)–CDs hybrid hydrogel nanocomposite film was further prepared as a platform membrane for the removal Cd²⁺ metal from wastewater. The as-prepared CH–CDs membranes show relatively good mechanical properties, based on stress resistance and flexibility to facilitate handling. The equilibrium state was reached within 5 min. Intriguingly, the UV-light illuminations enhanced the Cd²⁺ removal efficiency of the photoluminescent CDs substantially by four times faster under. It was found that adsorption followed pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity at 25 °C was found to be 112.4 mg g⁻¹ at pH 8. This work paves the way to new applications of CDs in water treatment.