Carbon surface derivatization by electrochemical reduction of a diazonium salt in situ produced from the nitro precursor

Grafting Carbon Fibers with Graphene via a One-Pot Aryl Diazonium Reaction to Refine the Interface Performance of T1100-Grade CF/BMI Composites

In this study, a one-pot aryl diazonium reaction was used as a simple and mild method to graft graphene onto the smooth and inert surface of T1100-grade carbon fiber (CF) through covalent bonding without any damage on CF, to refine the interface performance of CF/bismaleimide (BMI) composites. XPS, SEM, AFM, and dynamic contact angle testing (DCAT) were used to characterize chemical activity, morphologies, and wettability on untreated and grafted CF surfaces. Meanwhile, the impact of the graft method on the tensile strength of CF was also examined using the monofilament tensile test. IFSS between CF grafted with graphene and BMI resin achieved 104.2 MPa after modification, increasing from 85.5 MPa by 21.8%, while the tensile strength did not decrease compared to the pristine CF. The mechanism of this interface enhancement might be better chemical bonding and mechanical interlock between CF grafted with graphene and BMI resin, which is generated from the high surface chemical activity and rough structure of graphene. This study may propose a simple and mild method to functionalize the CF surface and enhance the interface performance of composites without compromising the tensile properties of T1100-grade CF.

Effect of Electrochemical Aryl Diazonium Salt Modification on Interfacial Properties of CF/PEEK Composites

The interfacial properties between carbon fiber (CF) and thermoplastic resin are relatively weak, which can be problematic for composites in structural applications. Improving the surface roughness of CF is regarded as an effective way to enhance the interface of composites. However, most CF modifying methods are complex and time-consuming, which cannot meet the demand for industrial production. Therefore, it is of great significance to research a fast technique of CF surface modification to strengthen the interface of composites. Herein, a one-pot reaction based on the aryl diazonium salt modification was applied to enhance the interface between CF and poly ether ether ketone (PEEK) resin. Carbon nanotubes (CNTs) were linked to CF by p-phenylenediamine (PPD) via cyclic voltammetry (CV). The surface morphology, chemical characteristics and surface energy of modified CF illustrated the effectiveness of this method, and the interfacial properties of as-prepared modified CF/PEEK demonstrated the increased tendency. All the CF was treated within 5 min and the interfacial shear strength (IFSS) of CF/PEEK was increased to the maximum of 99.62 MPa by aryl diazonium salt modification. This work may shed some light on the industrialized application of CF reinforced high-performance engineering thermoplastic composites.

Boosted electrocatalytic oxidation of organophosphorus pesticides by a novel high-efficiency CeO2-Doped PbO2 anode: An electrochemical study, parameter optimization and degradation mechanisms

This article presents a novel and highly efficient electrocatalytic degradation method for two significant organophosphorus pesticides, fenitrothion (FEN), and methyl parathion (MPN), using a Ti/β-PbO2-CeO2 modified anode (indirect oxidation). A comprehensive electrochemical investigation was also carried out to gain new insight into the redox behavior and destruction pathway of these pesticides (direct oxidation). The study also explores the effects of various operating parameters, such as initial solution pH, applied current density, and initial pesticides concentration, on the conversion-paired electrocatalytic removal process. To further enhance the degradation efficiency, a new configuration of the electrochemical cell was designed, employing two types of electrodes and two independent power supply devices. The conversion paired electrocatalytic degradation process of these pesticides involves first the direct reduction of FEN (or MPN) on a graphite cathode and then the indirect oxidation of reduced FEN (or MPN) by hydroxyl radicals electro generated on the Ti/β-PbO2-CeO2 anode. The synergism of these two processes together will effectively lead to FEN (or MPN) degradation. The degradation percentages of 98% for FEN and 95% for MPN at the optimal conditions for the electrochemical degradation of these pesticides were achieved at pH = 7, initial concentration 50 mg L-1, with a current density of 90 mA cm-2 for direct reduction and 11 mA cm-2 for indirect oxidation. Overall, this study presents a promising and efficient approach for the remediation of organophosphorus pesticide-contaminated environments, offering valuable insights into the electrochemical degradation process and highlighting the potential for practical application in wastewater treatment and environmental protection.

Electrochemical modification of carbon nanotube fibres

Covalent modification of the surface of carbon nanotube fibres (CNTFs) through electrochemical reduction of para-substituted phenyldiazonium salts and electrochemical oxidation of an aliphatic diamine is described. Following these strategies, diverse surface functionalities have been introduced while preserving the fibre bulk properties. The corresponding modified CNTFs were fully characterised by Raman spectroscopy, X-ray photoelectron spectroscopy, energy dispersive X-Ray, scanning electron microscopy and electrochemical impedance spectroscopy, exhibiting different surface properties from those of the unmodified CNTFs.

Versatile electrochemical approaches towards the fabrication of molecular electronic devices

We highlight state-of-the-art electrochemical approaches for diazonium electroreduction on various electrodes that may be suitable for flexible molecular electronic junctions.

Electrochemical Detection of pH-Responsive Grafted Catechol and Immobilized Cytochrome c onto Lipid Deposit-Modified Glassy Carbon Surface

The electrochemical systems of both grafted catechol as a pH-responsive electrophore and immobilized cytochrome c as a model redox protein are detected by cyclic voltammetry at an optimized lipid deposit-modified glassy carbon electrode. The catechol covalent grafting is successfully performed by the one-pot/three-step electrochemical reduction of 3,4-dihydroxybenzenediazonium salts generated in situ from 4-nitrocatechol. The resulting glassy carbon electrode electrochemically modified by grafted catechol species is evaluated as an efficient electrochemical pH sensor. The optimized molar ratio for the lipid deposit, promoting cytochrome c electrochemical activity in solution onto glassy carbon electrode, is reached for the lipid mixture composed of 75% 1,2-dioleoyl-sn-glycero-3-phosphocholine and 25% cardiolipin. Cytochrome c immobilization into the optimized supported lipid deposit is efficiently achieved by cyclic voltammetry (10 cycles) recorded at the modified glassy carbon electrode in a cytochrome c solution. The pH-dependent redox response of the grafted catechol and that of the immobilized cytochrome c are finally detected at the same lipid-modified glassy carbon electrode without alteration of their structure and electrochemical properties in the pH range 5-9.

Surface Characteristics of Microporous and Mesoporous Carbons Functionalized with Pentafluorophenyl Groups

The in situ diazonium reduction reaction is a reliable and well-known approach for the surface modification of carbon materials for use in a range of applications, including in energy conversion, as chromatography supports, in sensors, etc. Here, this approach was used for the first time with mesoporous colloid-imprinted carbons (CICs), materials that contain ordered monodisperse pores (10-100 nm in diameter) and are inherently highly hydrophilic, using a common microporous carbon (Vulcan carbon (VC)), which is relatively more hydrophobic, for a comparison. The ultimate goal of this work was to modify the CIC wettability without altering its nanostructure and also to lower its susceptibility to oxidation, as required in fuel cell and battery electrodes, by the attachment of pentafluorophenyl (-PhF₅) groups onto their surfaces. This was shown to be successful for the CIC, with the -PhF₅ groups uniformly coating the inner pore walls at a surface coverage of ca. 90% and allowing full solution access to the mesopores, while the -PhF₅ groups deposited only on the outer VC surface, likely blocking its micropores. Contact angle kinetics measurements showed enhanced hydrophobicity, as anticipated, for both the -PhF₅ modified CIC and VC materials, even revealing superhydrophobicity at times for the CIC materials. In contrast, water vapor sorption and cyclic voltammetry suggested that the micropores remained hydrophilic, arising from the deposition of smaller N- and O-containing surface groups, caused by a side reaction during the in situ diazonium functionalization process.

Self-Assembly under Confinement: Nanocorrals for Understanding Fundamentals of 2D Crystallization

Nanocorrals with different size, shape, and orientation are created on covalently modified highly oriented pyrolytic graphite surfaces using scanning probe nanolithography, i.e., nanoshaving. Alkylated diacetylene molecules undergo laterally confined supramolecular self-assembly within these corrals. When nanoshaving is performed in situ, at the liquid-solid interface, the orientation of the supramolecular lamellae structure is directionally influenced by the gradual graphite surface exposure. Careful choice of the nanoshaving direction with respect to the substrate symmetry axes promotes alignment of the supramolecular lamellae within the corral. Self-assembly occurring inside corrals of different size and shape reveals the importance of geometric and kinetic constraints controlled by the nanoshaving process. Finally, seed-mediated crystallization studies demonstrate confinement control over nucleation and growth principles.

Localized in situ generation of diazonium cations by electrocatalytic formation of a diazotization reagent

A new one-step electrochemical approach for the localized generation of diazonium cations in the diffusion layer of an electrode by taking advantage of the electrocatalytic properties of the electrode for the formation of the diazotization agent (nitrite) is proposed. Once nitrite anions are formed by electrocatalytic reduction of nitrate, they immediately react with an arylamine to produce the corresponding diazonium cations, which can be electrochemically readily reduced at the electrode surface. By this method, spontaneous modification of the electrode surface can be avoided. Furthermore, because the potential of the electrochemical nitrate reduction depends strongly on the nature of the electrode material, we also demonstrate that selective grafting can be achieved on a surface, which consists of two different materials: copper-gold or copper-glassy carbon substrates.