Reduction Of Aryl Diazonium Salts Research Articles

Covalent electrografting of aryl groups on AA2060-T8 surfaces, and their modification with Ce(4OHcin)3 to incorporate additional anticorrosive activity

The aluminum alloys used in aerospace applications are susceptible to corrosion. This has led to the development of methodologies that ensure the durability of the parts and pieces of aircraft. These anticorrosive processes involve the use of coatings containing chromate-based corrosion-inhibitor compounds. Although these coatings provide an excellent solution to this problem, their use in protection protocols is restricted owing to their high toxicity and carcinogenic nature.This study evaluates a different process to protect aluminum alloy surfaces that incorporates the derivatization of organic compounds using potentiostatic techniques. The metallic surface was modified in situ by the potentiostatic reduction of aryl diazonium salts, leaving the surface covered with molecular grafts. The grafting of molecules onto the surface is modulated by the application of a potential that causes the formation of aryl radicals. The organic compound selected in this study was p-toluidine in protic medium. The derivatization process in the AA2060-T8 alloy was carried out at different pHs and potentials, observing from the potential/current responses in 0.1 M NaCl solution that the maximum optimization is obtained at pH 3 and -1 V.Likewise, the E/I and electrochemical impedance (EIS) responses of the electrografted samples modified and functionalized with cerium 4-hydroxycinnamate (Ce(4-OHcinn)3) revealed that the presence of this compound in the arylic structure significantly increased the protective capacity of the organic film electrografted on the aluminum alloy.The morphologies and characteristics of the modified surface were studied by SEM, TEM, and XPS. Furthermore, TEM examinations of ultramicrotomed sections of the electrografted specimens revealed the presence of a film approximately 10 nm thick on the AA2060-T8 surface.

Patterning organic layers on carbon surfaces using electro-labile protected aryl diazonium salts

The reduction of aryl diazonium salts is nowadays recognized as a powerful technique to functionalize many surfaces included carbon materials. However, efficient and easy-to-perform methods to pattern monolayers on carbon surfaces using aryl diazonium grafting are still missing. Herein, we described the synthesis and the use of a special aryl diazonium salt bearing an electro-labile protecting group. After electrochemical deprotection, it leads to the formation of a reactive benzoic acid layer that can be easily post-functionalized. This approach is successfully implemented in a scanning electrochemical cell microscopy (SECCM) experiment to achieve a facile patterning of an organic layer onto carbon surfaces.

Electrochemical performance of diazonium-generated carbon films for electrochemical double-layer capacitors (EDLCs)

Carbon-based electrode materials for energy storage systems have received considerable attention thanks to their excellent mechanical properties, large specific surface areas and moderate electrical conductivities. Here, diazonium-generated carbon films on the flexible carbon paper (CP) electrodes were prepared through electrochemical reduction of aryl diazonium salts bearing COOH, NO2, CH3 and H functional groups. The production of polymeric carbon films by diazonium modification method was preferred because it is a simple and effective process, and also the carbon-based films prepared by this method are covalently attached to the carbon electrode surfaces. The capacitive properties of the robust carbon films were assessed by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) in three-electrode and asymmetric device configurations. The results indicated that diazonium-generated carbon films on flexible substrates exhibited typical EDLC behavior with high specific capacitance values (237.6–446.9 F g−1 at 0.5 A g−1 current density), and also their capacitive performances were largely dependent upon the functional groups on the benzene ring. Overall, this work reveals that the diazonium modification method is a promising approach to create the carbon-based active electrode materials in advanced energy-storage systems.

Covalent Grafting of Dielectric Films on Cu(111) Surface via Electrochemical Reduction of Aryl Diazonium Salts.

Covalent grafting of dielectric films containing polyhedral oligomeric silsesquioxane (POSS) on the surface of Cu(111) is performed by a one-step electrochemical reduction of diazonium salts. This method is efficient and economic and performs in a proton-polar solvent of deionized water and tetrahydrofuran (THF), where the monomer employs an octavinylsilsesquioxane (OVS) containing a POSS core. The eight vinyl bonds contained in OVS are used to participate in aryl radical-initiated polymerization reactions to form films. The formed film is dense and covers the copper surface completely and uniformly. The thickness of the film can be controlled by adjusting the reaction time. The components of the films are mainly polynitrophenyl (PNP) or polyaminophenyl (PAP) as well as poly(octavinylsilsesquioxane) (POVS), and the POVS content could be adjusted by the applied voltage. The introduction of POSS prevents the copper surface from being oxidized and often gives the film good properties such as good dielectric properties, mechanical properties, and thermal properties. In addition, the presence of Cu-O-C and Cu-C bonds between the film and copper interface is confirmed at different film thicknesses by X-ray photoelectron spectroscopy (XPS), which allowed the construction of covalent bonds between metal and nonmetal, further enhancing the bonding between the film and copper. Organic films prepared by electrochemical reduction of diazonium salts using OVS as a monomer will have potential significance for the future development of the electronics industry.

Antifouling performance and mechanism analysis of marine peptide modified aluminum alloy surface

Biofouling, the settlement of nuisance fouling organisms on underwater surfaces, seriously affects the performance of the ship and the development of the maritime industry. Using antimicrobial peptides to obtain antifouling performance is one of the most effective methods to solve this challenge. The present work assessed the peptide with the key amino acid residues and sequence (LWFYTMWH) of the marine microalgae Tetraselmis suecica as the antifoulants to aluminum alloy. The aluminum surface was introduced AlC bond through reduction of aryldiazonium salts. The peptides were grafted onto the surfaces by covalently binding the amino groups of peptides with the carboxyl groups on surfaces via 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) activation. The ATR-FTIR and XPS analyses confirmed the successful modification of peptides on the surfaces. The as-modified surfaces showed good antifouling capacity against the settlement of Gram-positive bacteria (Bacillus sp.) and Gram-negative bacteria (Escherichia coli) by destroying the cell membranes. The antibacterial mechanism of peptides was explained by coarse-grained molecular dynamics simulations and atomistic molecular dynamics simulations. It was revealed that the peptides mainly interacted with the phospholipid membranes through the amino residues at the carboxyl terminus, resulting in changes in the thickness and local curvature of the phospholipid membranes, eventually causing the membranes to rupture.

Examining the Role of Aryldiazonium Salts in Surface Electroinitiated Polymerization.

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.

Oxygen Interactions with Covalently Grafted 2D Nanometric Carboxyphenyl Thin Films—An Experimental and DFT Study

Surface modification is a hot topic in electrochemistry and material sciences because it affects the way materials are used. In this paper, a method for covalently attaching carboxyphenyl (PhCOOH) groups to a gold electrode is presented. These groups were grafted onto the electrode surface electrochemically via reduction of aryldiazonium salt. The resulting grafted surface was characterized using cyclic voltammetry (CV) before and after the functionalization procedure to validate the presence of the grafted layer. The grafting of PhCOOH groups was confirmed by analyzing electrode thickness and composition by ellipsometry and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) calculations indicated that the grafted layers provide a stable platform and resolved, for the first time, their interactions with oxygen.

Fluorine‐Free Nanoporous Low‐k Dielectric Film Covalently Grafted on Si via Aryldiazonium Chemistry

AbstractFluorine‐free nanoporous low‐k dielectric film containing polyhedral oligomeric silsesquioxanes (POSS) cage nanostructure is covalently grafted onto a p‐Si(100) surface via aryldiazonium chemistry, in an open environment without any inert gas protection. The method is based on two‐step reduction of aryldiazonium salts. First, 4‐nitrobenzene diazonium tetrafluoroborate (NBD) is reduced and a polynitrophenyl (PNP) passivation layer is formed on the p‐Si(100) surface, in an aqueous media with hydrofluoric acid being added. Second, NBD is reduced by electrons provided by external pulse power supply, and initiates octavinylsilsesquioxane polymerizing to form the film, which is composed of PNP and massive POSS cage, leading to a low k value. The average dielectric constant of the film is 2.12 at the range of 600 to 1700 nm wavelength, much lower than some low‐k materials reported by recent literature and traditional materials. The prepared films completely cover the Si substrate and are compact and thickness controllable. In particular, the k value can be controlled though the concentration of NBD. The low‐k properties imply they will be suitable to be utilized as high‐performance dielectric materials in future higher frequency communication field.

Diazonium Electrografting vs. Physical Adsorption of Azure A at Carbon Nanotubes for Mediated Glucose Oxidation with FAD‐GDH

AbstractThe electrochemical reduction of aryldiazonium salts is a versatile and direct route to obtain robust covalently modified electrodes. We report here a comparative study of Azure A modified carbon nanotube electrodes prepared by diazonium electrografting and by physical adsorption for bioelectrocatalytic glucose oxidation with fungal FAD‐glucose dehydrogenase from Aspergillus sp. The electrografted and adsorbed electrodes exhibited different reversible electroactivity consistent with polymer‐type and monomer‐type phenothiazine surface assemblies, respectively. The electrografted Azure A electrodes exhibited superior mediated bioelectrocatalysis compared to the adsorbed Azure A electrodes. A more than 10‐fold higher catalytic current up to 2 mA cm−2 at 0.2 V vs. Ag/AgCl together with a similarly low onset potential of −0.05 V vs. Ag/AgCl was observed at the electrografted electrodes. Faster estimated electron transfer kinetics and a +200 mV potential shift for the polymer‐type redox couple vs. the adsorbed monomer‐type couple underlines the favourable driving force for mediated electron transfer with the buried FAD active site for the diazonium‐derived bioelectrode.

Expanding the Scope of Surface Grafted Polymers Using Electroinitiated Polymerization.

The ability to rapidly modify the surface of materials is a powerful means of tailoring interfaces and interphases for a variety of applications. In this work, we demonstrate the extensive scope of an electrochemically mediated surface modification technique, able to install a range of surface grafted polymers of varying polarity and functionality. The irreversible reduction of aryldiazonium salts initiates polymer growth and provides a "priming layer" for the polymers to attach to, covalently anchoring them to the surface. We show the broad applicability of this technique through polymerization of 19 acrylate monomers, as well as a noncarbonyl bearing monomer species, styrene. Surface bound films were characterized using FT-IR, ellipsometry, and water contact angle.

Nanostructured Mixed Layers of Organic Materials Obtained by Nanosphere Lithography and Electrochemical Reduction of Aryldiazonium Salts

In this work, we have combined nanosphere lithography with electrochemical reduction of aryldiazonium salts to elaborate nanostructured mixed layers of organic materials. The strategy consists first in the deposition of a close-packed hexagonal monolayer of microbeads used as a mask for the electroreduction of a first aryldiazonium salt. After removing the beads, an ultrathin organic layer with holes remains. Then, a second aryldiazonium salt is electrochemically reduced selectively inside the holes. The relative thickness of the two deposited materials can be changed, leading to mixed layers of different topographies. Moreover, using diazoniums with complementary redox properties, a modified bifunctional electrode acting as a filter for electron transfer with a low potential gap has been obtained. Such layers are similar to low-band-gap organic semiconductors that can be easily n or p doped. Despite this analogy, the oxidation and reduction of redox probes in solution on such nanostructured surfaces occur on completely separated areas of the mixed layer.

Impact Mechanisms of Carboxyl Group Modified Cathode on Acetate Production in Microbial Electrosynthesis Systems

Microbial electrosynthesis systems (MESs) can convert carbon dioxide into added value compounds using microorganisms as catalyst, which is expected to help achieve conversion of greenhouse gases into resources. However, the synthetic efficiency of MESs is far behind the industry requirements. In this study, carbon cloth surfaces were bonded with carboxyl groups by electrochemical reduction of aryl diazonium salts and then used as a cathode in MESs reactors. The results showed that the hydrophilicity of the carbon cloth surfaces improved after the carboxyl groups were modified. However, weaker current of cyclic voltammetry was obtained in the modified cathode. Significant differences were observed between modified (CA-H, CA-M, CA-L) and non-modified cathode (CK) during the start-up period. After 48h, the hydrogen production rate of CA-H, CA-M, CA-L was 21.45, 28.60, and 22.75 times higher than CK. After 120h, the acetate accumulation concentration of CA-H, CA-M, CA-L was 2.01, 2.43, and 1.44 times higher than CK. After 324h, there was little difference in the electrochemical activity of cathodic biofilm and protein content (about 0.47 mg·cm-2) in all groups. The analysis of the community structure of cathodic biofilm showed that, in the genus level, Acetobacterium, Norank_p_Saccharibacteria, and Thioclava were the dominant species, accounting for 59.6% to 82.1%. There was little difference in the relative abundance of Acetobacterium in all groups (31.3% to 40.1%). However, the relative abundance of norank_p_Saccharibacteria in CA-H, CA-M, CA-L, and CK were 16.1%, 24.6%, 31.1%, and 37.5%, respectively. The carboxyl modified cathode had a great influence on the start-up stage of MESs, which could be a new idea for the rapid start-up of MESs.

Steric and Electronic Effects of Electrochemically Generated Aryl Radicals on Grafting of the Graphite Surface.

Grafting of aryl radicals generated by electrochemical reduction of aryldiazonium salts has been extensively studied on various surfaces. However, there exists two unclear aspects; the first one is the generality of the blocking ability of simple functional groups toward multilayer growth, and the second one is the electronic impact of substituent groups of aryl radicals on grafting efficiency. To address these aspects, we have studied the electrochemical functionalization of graphite using aryldiazonium salts having electron-donating or electron-withdrawing groups at the 3,4,5-positions. Atomic force microscopy investigation of the functionalized surfaces revealed the formation of monolayers for all aryldiazonium salts, and thus, nitro, carboxy, ester, methyl, and methoxy groups at the 3,4,5-positions of the benzene ring suppress polyaryl growth. The degree of grafting estimated by scanning tunneling microscopy imaging and Raman spectroscopy of the functionalized surfaces depends on the electronic state of the aryl radicals, in which the radicals with electron-donating groups show a high degree of functionalization, whereas those with electron-withdrawing groups exhibit a low degree of functionalization. We discuss several possibilities that affect grafting density. Though there are several factors, we hypothesize that one factor to explain the observed reactivity trend is the electronic property of the aryl radicals, namely, the relative position of the singly occupied molecular orbital energy levels of the aryl radicals with respect to the graphite Fermi energy level.

Electrochemical DNA Biosensing via Electrochemically Controlled Reversible Addition-Fragmentation Chain Transfer Polymerization.

Sensitive and selective sensing of biological molecules is fundamental to disease diagnosis and infectious disease surveillance. Herein, an ultrasensitive and highly selective electrochemical DNA biosensor is described by exploiting the electrochemically controlled reversible addition-fragmentation chain-transfer (eRAFT) polymerization as a signal amplification strategy and the peptide nucleic acid (PNA) probes as the recognition elements. Specifically, the PNA probes with a thiol at their 5'-terminals are anchored to a gold electrode surface (via gold-sulfur self-assembly) for sequence-specific recognition of target DNA (tDNA) fragments, of which the phosphate sites serve as the anchorages for the targeted labeling (via the well-established phosphate-Zr4+-carboxylate chemistry) of the carboxyl-group-containing chain-transfer agents (CTAs) for the succedent eRAFT polymerization, wherein the initiating radicals are generated through electrochemical reduction of aryl diazonium salts under a potentiostatic condition. In the presence of ferrocenylmethyl methacrylate (FcCH═CH2) as the monomer, the grafting of polymer chains from the CTA-anchored sites as a result of the eRAFT polymerization brings numerous electroactive Fc tags to the electrode surface, outputting a high electrochemical sensing signal even in the presence of trace amounts of tDNA fragments. Under the optimized conditions, the linear range of the described electrochemical DNA biosensor spans from 10 aM to 10 pM ( R2 = 0.998), with an attomolar detection limit (4.1 aM) being achieved. Moreover, the described electrochemical DNA biosensor is highly selective and applicable to the sensing of tDNA fragments in complex serum samples. Given its high efficiency, easy operation, and low cost, this biosensor shows great promise in real applications.

Covalent functionalization of polycrystalline silicon nanoribbons applied to Pb(II) electrical detection

Although recent studies in the field of nanomaterials have allowed the realization of highly sensitive sensors, research regarding new types of functionalization of nanostructures to reach high selectivity are still missing. Here, a simple electronic device based on polycrystalline silicon (poly-Si) nanoribbons used for lead detection is presented. This device is functionalized by reduction of aryl diazonium salts in order to detect heavy metals. The effectiveness of the grafting process and thickness homogeneity of the coating layer were evaluated by XPS and NanoSIMS techniques. The preconcentration of lead (Pb2+) at the surface of the functionalized nanostructures was substantially verified. Finally, electrical characterization of the resistors based on the functionalized nanoribbons, showed that the sensitivity to these species is increased in the concentration ranging from 10−7 to 10−5 mol L−1. This technique could pave the way for use of complexing agents to enhance heavy metal detection.

Multi-functionalization of lithographically designed gold nanodisks by plasmon-mediated reduction of aryl diazonium salts.

Plasmon-driven surface functionalization of nanoparticles is receiving increasing attention as it allows locally tailored chemical reactivity to be generated on the nanoparticle surface. The extension to surface multi-functionalization still represents a major breakthrough in chemistry. We address this issue by triggering regiospecific surface double-functionalization under plasmon excitation, using diazonium salts as surface functionalization agents.

Graphene Interface for Detection of Resorcinol an Endocrine Disruptor in Solubilized Ionic Liquid System: Electrochemical and COSMO-RS Quantum Studies

We report synthesis, characterization and covalent fabrication of graphene nanosheets (GR) on Au electrode. The GR nanosheets were characterized by XRD, Raman spectroscopy, FESEM and TEM techniques. The GR nanosheets were functionalized by reduction of aryldiazonium salt (Cl−N2+–Ph–COOH) to produce GR–Ph–COOH. In another step, Au electrode was modified by cysteamine (Cyst) to form Au–S–CH2–CH2–NH2 surface. Finally, GR–Ph–COOH was covalently attached to Au–S–CH2–CH2–NH2 by carbodiimide chemistry. The GR–Cyst–Au interface was used for electrochemical determination of resorcinol (RS) in ionic liquid [C4mim] [Cl] system over a concentration range from 0.3 to 45.2 μM with a detection limit (LOD) of 0.02 μM. The faster electron transfers kinetics of RS in [C4 mim] [Cl] system was attributed to synergetic effects of GR nanosheets and [C4 mim] [Cl] medium. The GR–Cyst–Au interface was successfully applied for determination of RS in Garnier hair-color cream as a real sample analysis. Computational quantum approach i.e. COSMO-RS model was also used to study trend of interactions in a ternary mixture of water, RS and [C4 mim] [Cl] system for proposed RS sensor.

Interest of molecular functionalization for electrochemical storage

Despite great interests in electrochemical energy storage systems for numerous applications, considerable challenges remain to be overcome. Among the various approaches to improving the stability, safety, performance, and cost of these systems, molecular functionalization has recently been proved an attractive method that allows the tuning of material surface reactivity while retaining the properties of the bulk material. For this purpose, the reduction of aryldiazonium salt, which is a versatile method, is considered suitable; it forms robust covalent bonds with the material surface, however, with the formation of multilayer structures and sp3 defects (for carbon substrate) that can be detrimental to the electronic conductivity. Alternatively, non-covalent molecular functionalization based on π–π interactions using aromatic ring units has been proposed. In this review, the various advances in molecular functionalization concerning the current limitations in lithium-ion batteries and electrochemical capacitors are discussed. According to the targeted applications and required properties, both covalent and non-covalent functionalization methods have proved to be very efficient and versatile. Fundamental aspects to achieve a better understanding of the functionalization reactions as well as molecular layer properties and their effects on the electrochemical performance are also discussed. Finally, perspectives are proposed for future implementation of molecular functionalization in the field of electrochemical storage.

Electron transfer at microbe-humic substances interfaces: Electrochemical, microscopic and bacterial community characterizations

Soluble and colloidal humic substances (HSs) involved in microbial extracellular electron transfer (EET) have been extensively investigated. However, little is known regarding EET at HS adlayers that are bound or complexed to the surface of natural solids. Here, we investigated EET process on seven types of HS adlayers by forming electroactive biofilms (EABs) and monitoring the biocurrent generation. The HS immobilized surfaces were carried out by firstly modifying glassy carbon surfaces via electrochemical reduction of aryl diazonium salts to create amino-functionalized surfaces, and then various HSs were covalently bonded to these amino groups via linkage molecules. The results showed that the HS adlayers formed from Leonardite, Elliott Soil and Pahokee Peat humic acids (HAs) facilitated EET by forming more active EABs, whereas the Suwannee River and Aldrich HAs, Suwannee River and Pahokee Peat fulvic acids (FAs) hindered EET. The EET positively correlated with electron accepting capacity and wettability of the HSs, and negatively correlated with the polarity of the HSs, and only weakly correlated with electron donating capacity and zeta potential of the HSs. Microscopic images showed that the thickness and viability of the biofilms varied based on the HS properties. A microbial community structure analysis showed that all of the biofilms were dominated by Proteobacteria and selectively enriched in Firmicutes and Bacteroidetes. Our study indicated that the HS adlayers significantly affected microbial EET, and these results provide a more comprehensive understanding of the HSs involved biogeochemical and biotransformation processes.

Tailoring the fibre-to-matrix interface using click chemistry on carbon fibre surfaces

A convenient and effective strategy to control the surface chemistry of carbon fibres is presented, comprising electro-chemical reduction of aryl diazonium salts onto the surface, followed by ‘click chemistry’ to tether the desired surface characteristic of choice.