Diazonium Reaction Research Articles

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.

Synthesis and Characterization of New Azo Dye Derived from Sulfamethaxolevia Diazonium Reaction and Study its Abilityas an Acid-base Indicator

Background: Most azo dyes are synthesized by diazotization of a primary amine, followed by conjugation with one or more electron-rich nucleophiles. Objective: This study presents the synthesis of a new azocompound by converting sulfamethoxazole to a diazonium salt. Methods: via reaction with hydrochloric acid and sodium nitrite at temperatures between 0 and 5 °C, the resulting salt is then coupled with a 4-methoxyphenol reagent in alkaline medium at the above temperatures to produce an azodye given the IUPAC name of (4-((2-hydroxy-5-methoxyphenyl)diazenyl)-N-(5-methylisoxazol-3yl)benzenesulfonamide). The azo dye precipitate was purified by crystallization methods using a solvent mixture of ethanol water. Characterization was done using different analytical methods such as IR, UV-Vis and H1-NMR in addition to measurements of physical properties. Results: The reddish-pink azo compound gave a maximum absorbance of 495 nm. Acid-base titrimetric analysis was conducted to examine the chemical indicator properties of the azo dye. Clear color differences were obtained between two spaces in the pH range 2-12, where a reddishpink color was obtained in the basic medium and a yellow color in the acidic medium. Conclusions: A new azo dye successfully presented its properties as an indicator.

Electrochemical performance of rGO/AFCNT composite and fabrication of supercapacitor electrode

An aqueous electrolyte-based supercapacitor electrode of graphene and amine-functionalized multiwall carbon nanotubes (AFCNT) is reported. Amine groups were covalently introduced on the surface of Carbon nanotubes (CNT) by diazonium reaction. In-situ reduction of graphene oxide over amine functionalized carbon nanotube template resulted the final composite. At current density of 1 A/g the electrode showed 384 F/g specific capacitance. The electrode had an energy density of 53.33 Wh/kg and power density of 499.13 W/kg. The electrode evinced almost 90% of capacitance retention even at elevated current density of 5 A/g. • Composite of Graphene/- NH 2 functioned MWCNT developed for supercapacitor electrode. • Composite shows specific capacitance of 384 F/g at a current density of 1 A/g. • Introduction of hydrophilic amine group prevents the restacking of graphene layers effectively. • The electrode shows retention of 90% capacitance at current density as high as 5 A/g.

Quantum Defects: What Pairs with the Aryl Group When Bonding to the sp2 Carbon Lattice of Single-Wall Carbon Nanotubes?

Aryl diazonium reactions are widely used to covalently modify graphitic electrodes and low-dimensional carbon materials, including the recent creation of organic color centers (OCCs) on single-wall carbon nanotube semiconductors. However, due to the experimental difficulties in resolving small functional groups over extensive carbon lattices, a basic question until now remains unanswered: what group, if any, is pairing with the aryl sp3 defect when breaking a C═C bond on the sp2 carbon lattice? Here, we show that water plays an unexpected role in completing the diazonium reaction with carbon nanotubes involving chlorosulfonic acid, acting as a nucleophilic agent that contributes -OH as the pairing group. By simply replacing water with other nucleophilic solvents, we find it is possible to create OCCs that feature an entirely new series of pairing groups, including -OCH3, -OC2H5, -OC3H7, -i-OC3H7, and -NH2, which allows us to systematically tailor the defect pairs and the optical properties of the resulting color centers. Enabled by these pairing groups, we further achieved the synthesis of OCCs with sterically bulky pairs that exhibit high purity defect photoluminescence effectively covering both the second near-infrared window and the telecom wavelengths. Our studies further suggest that these diazonium reactions proceed through the formation of carbocations in chlorosulfonic acid, rather than a radical mechanism that typically occurs in aqueous solutions. These findings uncover the unknown half of the sp3 defect pairs and provide a synthetic approach to control these defect color centers for quantum information, imaging, and sensing.

Molecule bridged graphene/Ag for highly conductive ink

Printing is a method of additive manufacturing that can reduce material costs and environmental contamination during the fabrication process. Ag ink is commonly used in printed electronics, such as interconnects, inductors, and antennas. However, the high cost of noble Ag restricts its massive applications. To reduce the cost of the state-of-the-art Ag ink and realize large-scale manufacturing, we develop a molecule-bridged graphene/Ag (MB-G/A) composite to produce highly conductive and cost-effective paper-based electronics. Graphene can be used to substitute part of Ag nanoparticles to reduce costs, form a conducive percolation network, and retain a reasonable level of conductivity. We adopt cysteamine as a molecular linker, because it anchors on the surface of graphene via the diazonium reaction. Additionally, the thiol functional group on the other end of cysteamine can bond to a Ag atom, forming a molecular bridge between graphene and Ag and promoting electron transport between Ag and graphene. As a result, the maximum conductivity of MB-G/A inks can reach 2.0 × 105 S m−1, enabling their successful application in various printable electronics. In addition, the optimum MB-G/A ink costs less than half as much as pure Ag inks, showing the great potential of MB-G/A ink in commercial electronic devices.

Demonstration of Molecular Tunneling Junctions Based on Vertically Stacked Graphene Heterostructures

We demonstrate the fabrication and complete characterization of vertical molecular tunneling junctions based on graphene heterostructures, which incorporate a control series of arylalkane molecules acting as charge transport barriers. Raman spectroscopy and atomic force microscopy were employed to identify the formation of the molecular monolayer via an electrophilic diazonium reaction on a pre-patterned bottom graphene electrode. The top graphene electrode was transferred to the deposited molecular layer to form a stable electrical connection without filamentary damage. Then, we showed proof of intrinsic charge carrier transport through the arylalkane molecule in the vertical tunneling junctions by carrying out multiprobe approaches combining complementary transport characterization methods, which included length- and temperature-dependent charge transport measurements and transition voltage spectroscopy. Interpretation of all the electrical characterizations was conducted on the basis of intact statistical analysis using a total of 294 fabricated devices. Our results and analysis can provide an objective criterion to validate molecular electronic devices fabricated with graphene electrodes and establish statistically representative junction properties. Since many of the experimental test beds used to examine molecular junctions have generated large variation in the measured data, such a statistical approach is advantageous to identify the meaningful parameters with the data population and describe how the results can be used to characterize the graphene-based molecular junctions.

SYNTHESIS OF NEW SUBSTITUTED PROCAINE HYDROCHLORIDE COMPOUNDS AND THEIR USE IN SPECTROPHOTOMETRIC DETERMINATION OF TETRACYCLINE HYDROCHLORIDE THROUGH DIAZOTIZATION-COUPLING REACTIONS

Background: Tetracycline is one of the most important antibiotics. It is used to treat many different bacterial infections. It is often used in treating severe acne, or sexually transmitted diseases such as syphilis, gonorrhea, or chlamydia. In some cases, tetracycline is used when penicillin or another antibiotic cannot be used to treat serious infections such as the ones caused by Bacillus anthracis, Listeria, Clostridium, Actinomyces. Aim: synthesized a new novel reagent used to determine TCH spectrophotometrically by using diazonium and coupling reaction. Methods: Four new substituted procaine derivatives were prepared by simple organic methods using aniline derivatives. A spectrophotometric approach was established for the micro-determination of TCH. The stoichiometry was investigated using mole ratio and continuous variation methods, and the stability constant was also estimated. The ΔG, ΔH, and ΔS were determined as thermodynamic parameters for evaluating the effect of temperature on the reaction. Results: Substituted procaine derivatives were prepared, and o-hydroxy procaine seems to be the best reagent used to determine TCH by diazotization and coupling reaction. The result was a yellow water-soluble dye with a maximum absorbance of 380 nm. The reaction conditions were studied and optimized. Beers law was obeyed over a concentration range (2.5–50) μg.mL-1 for TCH. The molar absorptivity was (14.4669.103) L.mol-1.cm-1, and the detection limit was (0.5052) μg.mL-1. The stoichiometry of the formed product was found 1:1 (o-hydroxyprocaine: TCH). The stability constant indicated that the product formed was stable, and the thermodynamic parameters showed that the diazonium salt reaction was preferred to occur at a low temperature. Conclusions: a simple, accurate, and fast method was developed to determine TCH in pure form and pharmaceuticals by coupling the TCH with a newly synthesized procaine derivative reagent (o-hydroxy procaine) in a basic medium.

Functionalization of Self-supporting Graphene with a High Grafting Yield for Hydrophilicity Improvement

Abstract The functionalization of self-supporting graphene (SSG) which in-situ grows on a flexible graphite sheet is performed by an electrochemical exfoliation in a HCl solution and then a diazonium reaction using p-aminobenzenesulfonic acid. The functionalized SSG is defined as F-SSG. The grafting yield of benzenesulfonic acid groups on F-SSG is up to 7.5%. The conductivity of the F-SSG is 502.7 S/cm. The water contact angle of F-SSG is only 28.6°, which is much smaller than that of SSG, displaying good hydrophilicity.

Modification of Renewable Cardanol onto Carbon Fiber for the Improved Interfacial Properties of Advanced Polymer Composites.

A facile in situ polymerization was developed for grafting renewable cardanol onto the carbon fiber (CF) surfaces to strengthen the fiber–matrix interface. CFs were chemically modified with hydroxyl groups by using an aryl diazonium reaction, and then copolymerized in situ with hexachlorocyclotriphosphazene (HCCP) and cardanol to build cardanol-modified fibers (CF-cardanol). The cardanol molecules were successfully introduced, as confirmed using Raman spectra and X-ray photoelectron spectroscopy (XPS); the cardanol molecules were found to increase the surface roughness, energy, interfacial wettability, and activity with the matrix resin. As a result, the interlaminar shear strength (ILSS) of CF-cardanol composites increased from 48.2 to 68.13 MPa. In addition, the anti-hydrothermal ageing properties of the modified composites were significantly increased. The reinforcing mechanisms of the fiber–matrix interface were also studied.

Effect of surface bonding of FePC with electrospun carbon nanofiber on electrocatalytic performance for aprotic Li-O2 batteries

The bifunctional catalysts assist the complete reversible cycle of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with low polarization of a lithium-oxygen (Li-O2) battery were known to be critical cathode components. In this work, electrospun nitrogen-doped carbon nanofibers (N-CNFs) were prepared to use as supports to anchor iron phthalocyanine (FePc) bifunctional catalyst for oxygen (O2) electrode in Li-O2 batteries. By using FePc and N-CNFs, two different bonding composites were fabricated via diazonium reaction by refluxing and physical mixing methods which were resulting into covalent linkage via pyridine (Py) (denoted as FePc/Py/N-CNFs) and noncovalent interaction via π-π stacking (denoted as FePc/N-CNFs). The systematic characterizations confirmed that the spun carbon nanofibers were functionalized by pyridine and the anchored FePc molecule donated the axial ligand for the iron (Fe) center in the FePc/Py/N-CNFs composite. The FePc were embedded in the N-CNFs composites combining the electrocatalytic activity of the FePc with ORR/OER processes and N-CNFs with a three-dimensional (3D) interconnected porous network structure through a connecting link of one-dimensional (1D) porous and N-doping carbon nanofiber which exhibited a high performance when acting as the cathode in Li-O2 batteries. However, the FePc/Py/N-CNFs composite showed the higher catalytic activity and prominent structural stability due to the FePc being strongly interlinked with the N-CNFs through the Py connection, which could avoid the deformation and agglomeration of FePC molecules during cycling and thus possessed the high electrochemical performance of the composite. This study demonstrated the unique design of FePc/Py/N-CNFs composite structure in this work would be found as a promising O2 electrode material with enhanced electrochemical performance in rechargeable Li-O2 batteries.

Light-Assisted Diazonium Functionalization of Graphene and Spatial Heterogeneities in Reactivity.

The reaction of monolayer graphene with aryl diazonium salts is a popular approach for functionalizing graphene under ambient conditions. We here apply interference reflection microscopy (IRM), a label-free optical technique, to study the in situ reaction dynamics of the representative diazonium reaction of graphene with 4-nitrobenzenediazonium tetrafluoroborate (4-NBD) at high spatiotemporal resolution and further correlate results with atomic force microscopy, Raman spectroscopy, and infrared scattering scanning near-field optical microscopy. Interestingly, we find the reaction to be significantly promoted by a low (0.5 W/cm2) level of blue visible light, whereas at the same intensity level, red light has negligible effects on reaction rate. We further report rich spatial heterogeneities for the reaction, including enhanced reactivity at graphene edges and an unexpected flake-to-flake variation in reaction rate. Moreover, we demonstrate direct photopatterning for the 4-NBD functionalization, achieving 400 nm patterning resolution.

P-Phenylenediamine-modified graphene oxide as a sorbent for solid-phase extraction of phenylurea herbicides, nitroimidazoles, chlorophenols, phenylurea insecticides and phthalates.

Graphene oxide was covalently modified with p-phenylenediamine via a diazonium reaction. The resulting material was employed as a sorbent for the solid-phase extraction of six phenylurea herbicides (metoxuron, monuron, chlortoluron, isoproturon, monolinuron, and buturon) from environmental water and lettuce leafs. Some key factors that influence the extraction efficiency were studied, including sample loading rate, sample pH, and desorption conditions. Following desorption with acetonitrile, the analytes were quantified by HPLC with UV detection. Under optimized conditions, response to phenylurea herbicides is linear in the 2.0-100ngmL-1 concentration range for water samples, and 5.0-100ngg-1 for leaf lettuces. The limits of detection are 0.10-0.25ngmL-1 for water samples, and 1.5-2.5ngg-1 for leaf lettuces. The sorbent was also applied to the preconcentration of organic compounds including nitroimidazoles, chlorophenols, phenylurea insecticides and phthalates. This shows that this sorbent has a large potential for the enrichment of organic pollutants. Graphical abstract A graphene oxide/p-phenylenediamine (GO@PA) composite was prepared via a simple and environmentally-friendly diazonium reaction between p-phenylenediamine diazonium salt and graphene oxide. It was used as the solid phase extraction (SPE) adsorbent to extract phenylurea herbicides with the extraction efficiency higher than that of commercial C18, multi-walled carbon nanotube and polystyrene polymer. The SPE method was combined with HPLC for simultaneous determination of six phenylurea herbicides in environment water and vegetable samples.

Facile preparation of hyperbranched polysiloxane‐grafted carbon fibers with improved interfacial strength of silicone resin composites

AbstractNew hybrid carbon fibers (CFs) were facilely prepared via in situ synthesizing hyperbranched polysiloxane with epoxy groups onto the fiber surface with the aim to enhance interfacial strength of composites. CFs were grafted with phenyl amine groups through an aryl diazonium reaction, and then modified with hyperbranched polysiloxane obtained by the sol‐gel polymerization of γ‐glycidyloxypropyltrimethoxysilane. Surface structures of different CFs were characterized by Raman spectroscopy and X‐ray photoelectron spectroscopy, indicating the successful modification. The introduced hyperbranched polysiloxane enhanced fiber roughness, polarity, wettability, and surface free energy. Hence, the interfacial shear strength and impact toughness of polysiloxane modified composites (CF‐g‐Polysiloxane) increased sharply compared with those of untreated composites. Moreover, Interfacial reinforcing and toughening mechanisms have also been studied, and polysiloxane modification maintained fiber tensile strength. The obvious improvement of anti‐hydrothermal aging behaviors after modification could be due to the introduction of strong SiOSi bonds at the interface.

Grafting of active carbon nanotubes onto carbon fiber using one-pot aryl diazonium reaction for superior interfacial strength in silicone resin composites

Abstract A novel and effective method was proposed for grafting carbon nanotubes (CNTs) with amino groups onto the surface of carbon fibers (CFs) by using one-pot aryl diazonium reaction in mild, eco-friendly conditions. Based on the diazonium reaction, CNTs were grafted with phenyl amino groups, and then functionalized CNTs (CNT-NH2 ) were modified onto the fiber surface to enhance fiber surface roughness and wettability , which could potentially increase interfacial strength of composites. Homogeneous multi-scale structures with different concentrations of CNTs were achieved. Interfacial properties of hybrid composites were closely dependent on the grafting density. The resulting hierarchical reinforcements improved composites interfacial strength significantly by the enhanced mechanical interlocking and the formed chemical bonding at the interface.

Effect of graphene treated with cyclohexyl diamine by diazonium reaction on cure kinetics, mechanical, thermal, and physical properties of natural rubber/graphene nanocomposite foam

The influence of functionalization of cyclohexyl diamine onto the graphene surface via diazonium reaction on the cure kinetics as well as morphology, mechanical, thermal and physical properties of natural rubber (NR)/graphene nanocomposite foam was investigated. The surface functionalization of graphene was confirmed by Fourier transform infrared spectroscopy, Raman spectroscopy, and thermogravimetric analysis (TGA). Without an addition of blowing agent, the vulcanized NR composites containing cyclohexyl amine‐treated graphene showed not obvious different dispersion of graphene nanoplatelets than those containing untreated graphene as confirmed by transmission electron microscopy micrographs. Although the addition of untreated graphene could accelerate the sulfur vulcanization rate of NR nanocomposite foam due to the high thermal conductivity of graphene particle, and the remaining oxygen functional groups on the surface of graphene, the amines from cyclohexyl diamine on the treated graphene could react with carboxylic and epoxide group on the surface of graphene leading to a reduction of reactive oxygen functional groups on graphene surface and in turn slowed vulcanization rate. The fast vulcanization rate in untreated graphene system led to small bubble size in the NR nanocomposite foams. In contrast, the treated graphene system showed high tensile strength and low thermal expansion coefficient owing to low cell density. Finally, the defect on the graphene surface after functionalization was detected by Raman spectroscopy; this resulted in poor thermal conductivity for the treated graphene composite system. POLYM. COMPOS., 40:E1766–E1776, 2019. © 2018 Society of Plastics Engineers

Reduction of carbon dioxide to methanol on the surface of adenine functionalized reduced graphene oxide at a low potential

In this study, the surface of reduced graphene oxide (rGO) was modified with adenine via diazonium reaction. Then, to prepare Pt@Adenine-rGO, Pt was deposited on the surface of adenine-rGO, using cyclic voltammetry in the range of −0.30 to +1.30 V at a scan rate of 100 mV s−1 in a solution containing Pt salt. Afterward, it was characterized by various techniques such as scanning electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. Electrochemical studies showed the efficient electrocatalytic behavior of Pt@Adenine-rGO for the reduction of CO2 to methanol at −0.30 V. The products formed on the surface of Pt@Adenine-rGO were monitored using different techniques including Raman spectroscopy, gas chromatography, gas chromatography-mass spectrometry, and 13C NMR spectroscopy. Our findings indicated that methanol with a reasonably high Faradaic efficiency up to 85% and a current density of 0.5 mA cm−2 as the main product of CO2 reduction on the surface of Pt@Adenine-rGO.

Electrically Controllable Single-Point Covalent Functionalization of Spin-Cast Carbon-Nanotube Field-Effect Transistor Arrays

Single-point-functionalized carbon-nanotube field-effect transistors (CNTFETs)have been used to sense conformational changes and binding events in protein and nucleic acid structures fromintrinsic molecular charge. The key to utilizing thesedevices as single-molecule sensors is the ability to attach a single probe molecule to an individual device. In contrast, with noncovalent attachment approaches such as those based on van der Waals interactions, covalent attachment approaches generally deliver higher stability but have traditionally been more difficult to control, resulting in low yield. Here, we present a single-point-functionalization method for CNTFET arrays based on electrochemical control of a diazonium reaction to create sp3 defects, combined with a scalable spin-casting method for fabricating large arrays of devices on arbitrary substrates. Attachment of probe DNA to the functionalized device enables single-molecule detection of DNA hybridization withcomplementary target, verifying the single-point functionalization. Overall, this method enablessingle-point defect generation with 80% yield.

Reduced graphene oxide decorated with thionine, excellent nanocomposite material for a powerful electrochemical supercapacitor

In this paper, reduced graphene was decorated with thionine to synthesize Th/rGO nanocomposite via diazonium reaction. The nanocomposite was identified using several techniques including SEM, EDX, XRD, XPS, and IR techniques. The behavior of the nanocomposite, as a supercapacitor electrode, was examined using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The results obtained demonstrated that the nanocomposite has an excellent specific capacitance of 1255 F/g at a current density of 0.5 A/g. Furthermore, the stability of the electrode was examined after 5000 cycles. The results showed that 93% of the initial capacity appears after 5000 cycles.

Tuning interfacial strength of silicone resin composites by varying the grafting density of octamaleamic acid-POSS modified onto carbon fiber

Octamaleamic acid-polyhedral oligomeric silsesquioxanes (OMA-POSS) were chemically modified onto the surface of carbon fibers (CFs) by a facile and high efficient two-step method. CF was grafted with hydroxyl groups via aryl diazonium reaction, and then covalently functionalized with OMA-POSS. The grafting density could be tuned through the concentration of OMA-POSS. Fiber surface structures were characterized by confirming the covalent bonding nature between OMA-POSS and CF. OMA-POSS was scattered on CF surface uniformly, and fiber polarity and roughness increased with the increased grafting density of OMA-POSS. Interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of the modified CFs composites enhanced as the grafting density grew, which could be ascribed to OMA-POSS interface with providing different degrees of chemical bonding and mechanical interlocking. Moreover, the hydrothermal aging resistance of composites is highly dependent on the amounts of the introduced OMA-POSS. The storage modulus and the glass transition temperature could increase by 8 GPa and 14 °C based on dynamic mechanical analysis testing. In addition, the interfacial reinforcing mechanisms have been also analyzed, and surface modification maintained fiber tensile strength.

NiO nanoparticles decorated at Nile blue-modified reduced graphene oxide, new powerful electrocatalysts for water splitting

New nanocomposites, containing nickel oxide nanoparticles (NiONPs) and Nile blue@reduced graphene oxide (NB/rGO), were synthesized. Nile blue was decorated on the surface of rGO by covalent bonds (using diazonium reaction). Then, NiONPs was immobilized on the surface of the functionalized rGO. The electrocatalytic and electrochemical behaviors of NiO@rGO and NiO@Nile/rGO nanocomposites for HER were investigated using cyclic voltammetry and electrochemical impedance spectroscopy in acidic and alkaline media. From them, NiO@rGO has shown long-term stability for HER in acidic solution at room temperature. The electrocatalytic activity of NiO@rGO (vs. NiO@Nile/rGO) for HER was greatly improved and its behavior was close to the behavior of platinum. In the next stage of our study, due to the importance of oxygen as an energy source, the production of oxygen molecules through electrochemical oxidation of water at NiO@rGO and NiO@Nile/rGO were studied too. For this purpose, the electrochemical behaviors of the nanocomposites for oxygen evolution reaction were investigated using cyclic voltammetry and electrochemical impedance spectroscopy in acidic and alkaline media. The results of them confirmed that NiO@Nile/rGO acts as an excellent electrocatalyst with good long-term stability for oxygen evolution reaction in 0.5 mol L−1 KOH solution at room temperature.Therefore, NiO@rGO and NiO@Nile/rGO can be used as powerful cathode and anode, respectively in an electrochemical cell for water splitting.