MEDIA | ARTICLES

Functionalizing Gold Nanoparticles with Calix[4]arenes Monolayers for Enhancing Selectivity and Stability in ORR Electrocatalysis

Herein we describe the ORR activity of gold nanoparticles functionalized with a covalently-bound monolayer of calix[4]arenes. These nanocatalysts show i) enhanced selectivity and stability compared to their citrate-stabilized counterparts, ii) excellent activity with a dominant 4-electron reduction of O2 with good electrocatalytic performances along with a high robustness under operation.

Ready-to-use germanium surfaces for the development of FTIR-based biosensors for proteins

Herein we report on the use of a calix[4]arene–tetradiazonium salt decorated with four oligo(ethylene glycol) chains and a terminal reactive carboxyl group for the development of sensitive and selective FTIR-based biosensors devoted to the detection of proteins.

Strategies for the formation of monolayers from diazonium salts: unconventional grafting media, unconventional building blocks

In this mini review, we briefly describe the different strategies that have been developed to prepare well-ordered monolayers. We especially focus on the use of calixarenes by taking benefit of their pre-organized structure. This review highlights the potential of aryldiazonium grafting as competitive alternative to SAMs of alkythiols.

Read More : Front. Chem. 2020, 8:559.

Robust Hydrophobic Gold, Glass and Polypropylene Surfaces Obtained Through a Nanometric Covalently Bound Organic Layer

Here, we describe the grafing of polyfluorinated calix[4]arenes on gold, polypropylene and glass. For all surfaces, contact angles higher than 110° were recorded even after 18 months. The results presented herein thus present an attractive and sustainable strategy for bringing hydrophobic properties at the interface of a wide range of materials.

Read More : RSC Adv. 2020, 10, 13553-13561.

Use of calixarenes bearing diazonium groups for the development of robust monolayers with unique tailored properties

In this review, the recent advances of the use of calixarenes diazonium derivatives for the formation of robust and compact monolayers are presented. The use of these tailored surfaces for applications such as anti-biofouling, chemical sensing in water and the development of hydrophobic surfaces are discussed.

Synthesis of a Calix[4]arene-monodiazonium Salt for Surface Modification

Here, we report a calix[4]arene-monodiazonium salt that can be easily electrografted within a few minutes on GC electrodes by cyclic voltammetry or chronoamperometry. The study of the blocking properties of the calixarene-coated electrodes toward redox probes revealed that compact layers were formed upon electrografting.

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

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 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.

Read More : Langmuir 2018, 34, 6021-6027.

Controlled Functionalisation of Gold Nanoparticles with Mixtures of Calix[4]arenes revealed by Infra-red Spectroscopy

Here, we report a calix[4]arene-tetradiazonium decorated by four oligo(ethylene glycol) chains on the small rim, which upon grafting gave AuNPs with excellent stability thanks to the C–Au bonds. Mixtures of this calixarene and one with four carboxylate groups were grafted on AuNPs. This strategy opens the way to robustly protected AuNPs with well-defined numbers of functional or postfunctionalizable groups.

Read More : Langmuir 2017, 33, 8253-8259.

Immobilization of monolayers incorporating Cu funnel complexes onto gold electrodes. Application to the selective electrochemical recognition of primary alkylamines in water

The immobilization of a copper calix[6]azacryptand funnel complex on gold-modified electrodes is reported. One of the strategies relies on the electrografting of a calix[4]arene platform bearing diazonium functionalities. The Cu complex displays a well-defined quasi-reversible system in cyclic voltammetry associated with the Cu(II)/Cu(I) redox process. Remarkably, this redox process triggers a powerful selective detection of primary alkylamines in water at a micromolar level, based on a cavitary recognition process.

Controlled Modification of Polymer Surfaces Through Grafting of Calix[4]arene-Tetradiazoate Salts

An attractive methodology using calixarenes bearing diazonium groups has been developed for the surface modification of polymers such as polypropylene, polyethylene terephthalate, and polystyrene. The results highlighted the fact that the calix[4]arenes are grafted as a robust and uniform monolayer, allowing a fine control over surface modification. It opens real possibilities in the controlled immobilization on polymers of a wide variety of molecules such as biomolecules or chromophores and in the tailoring of polymer properties.

Extremely robust and post-functionalizable gold nanoparticles coated with calix[4]arenes via metal–carbon bonds

Gold nanoparticles stabilized with a thin layer of postfunctionalizable calix[4]arenes were prepared through the reductive grafting of a calix[4]arene‐tetra‐diazonium salt. These particles show exceptional stability towards extreme pH, F‐, NaCl, and upon drying. Post‐functionalization of the calix‐layer was demonstrated, opening the way to a wide range of applications.

One-Pot Electrografting of Mixed Mono-Layers with Controlled Composition

Herein, binary mixtures of calix[4]arene-tetra-diazonium salts are electrografted to form covalently bound monolayers. The distribution of the two calixarenes on the surface is directed by their relative molar fraction in the deposition solution. The strategy allows the control of the composition of mixed monolayers in a one-step approach. This study highlights the potential of diazonium salt electrografting as a competitive alternative to chemisorption strategies such as self-assembled monolayers of alkyl thiols in the field of surface functionalization.

Controlled functionalization of surfaces at the molecular scale

Herein, we describe an innovative and versatile surface modification approach using calix[4]arene bearing diazonium groups. This leads to the formation of highly robust and densely-packed monolayers on a large range of materials. Further, the introduction of functional objects can be performed with a fine spatial control at the molecular scale through adequate decoration of the calixarene platform.

Construction de surfaces modifiées par une monocouche de calix[4]arènes : contrôle chimique et spatial à l’échelle moléculaire

La fonctionnalisation de surfaces couvre un large champ d’applications tels que les traitements de surfaces (verres anti-salissures, revêtements antibactériens, peintures facilement lessivables..), les implants biocompatibles, l’électronique moléculaire, les nanomatériaux, les capteurs chimiques et biologiques. Depuis quelques années, ce domaine connaît un essor considérable avec comme but l’apport de nouvelles propriétés à la surface (mouillabilité, résistance à la corrosion, biocompatibilité, etc.) ....

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

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.

Read more : Nature Commun. 2012, 33, 1130.

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