Reduction Of Diazonium Salts Research Articles

Determination of carcinoembryonic antigen (CEA) by surface plasmon resonance-enhanced total internal reflection ellipsometry (SPRe-TIRE)

A surface plasmon resonance-enhanced total internal reflection ellipsometric (SPRe-TIRE) aptasensor is reported for the determination of the carcinoembryonic antigen (CEA). A gold nanofilm-coated SF10 glass slide was modified with electrochemical diazonium salt reduction and gold nanoparticles (AuNPs) to form a sensor. Next, a specific aptamer for CEA was immobilized on the AuNPs via self-assembly. The platform was characterized by X-ray photoelectron spectroscopy, ellipsometry, and cyclic voltammetry for each step of the preparation of the sensor. CEA aptamers with different affinities were used. SPRe-TIRE employed total internal reflection geometry and AuNPs to enhance plasmon resonance for the sensitive and selective determination of CEA in human serum. The working range of the aptasensor was from 0.01 to 500 ng/mL with an optimum detection limit of 0.1 pg/mL.

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.

Kinetic studies on the extraction of oil from a new feedstock (Chukrasia tabularis L. seed) for biodiesel production using a heterogeneous catalyst.

This study has identified a new feedstock Chukrasia tabularis L. (C. tabularis) seed for the production of biodiesel. Oil was extracted from the seeds with and without autoclave-assisted ultrasonic homogenization (AUH) pretreatment using different solvents. The solvent n-hexane with AUH pretreatment yielded a maximum oil yield of 32 wt%. The kinetics and thermodynamics of the extraction process were studied in a batch. The data showed that extraction followed first-order kinetics with a rate constant of 1.4 × 10-4min-1, activation energy of 63.604kJmol-1 and pre-exponential factors of 66.66 × 104s-1. The physiochemical properties of the oil were determined from which it was identified that C. tabularis oil has high free fatty acid (FFA) content, requiring a single-step esterification cum transesterification reaction to produce biodiesel economically. The modified aryl diazonium salt reduction process was used to synthesize a heterogeneous acid catalyst (HAC) from activated carbon precursor and was used to catalyze biodiesel reaction. Furthermore, HAC was characterized by different analytical techniques and it was found that it had an acid site density of 1.02mmolg-1 and a specific surface area of 602 m2g-1. The parameters affecting the biodiesel process were studied to obtain a maximum biodiesel conversion of 98.5% at 6 wt% catalyst loading, 15:1 methanol to oil molar ratio, 120min reaction time, 70 ºC reaction temperature, and 500rpm stirring rate. Reusability studies were performed which showed that HAC can be recycled up to five cycles with a conversion above 90% in the fifth cycle. Moreover, the fuel properties of biodiesel were determined using standard methods and were compared with ASTM D6751 and EN14241 standards.

The Surface Potential of Zero Charge Controls the Kinetics of Diazonium Salts Electropolymerization

AbstractOne of the central fundamental properties of solid/liquid interfaces is the potential of zero charge (pzc), where no excess charge prevails at the electrode surface. Applying potential on either side of the pzc can control adsorption of molecules on surfaces and is paramount for any interfacial process. However, the impact of pzc on electrode processes has been only demonstrated for reactions involving the adsorption of inorganic ions and gases. Here, the direct relationship between the pzc and electropolymerization rate of a small organic molecule was reported. The electrochemical reduction of diazonium salts, which are the most commonly used molecules to form thin films of molecules on electrode surfaces, was tested. The kinetics of the surface reaction and the reduction potential in electrochemical measurements depended on the pzc of the surface following the order of gold>platinum>carbon>indium‐tin‐oxide>fluorine‐doped tin‐oxide>silicon hydride. The immediate consequence of this finding was that the concentration of the diazonium salt molecules became critical in defining the electrochemical reduction mechanism. At higher concentrations, the mechanism was pzc‐controlled adsorption‐dominated inner‐sphere electron transfer whereas at lower concentrations, diffusion‐based outer‐sphere electron transfer dominated.

Electro-polymerization rates of diazonium salts are dependent on the crystal orientation of the surface

Electro-polymerization of diazonium salts is widely used for modifying surfaces with thin organic films. Initially this method was primarily applied to carbon, then to metals, and more recently to semiconducting Si. Unlike on other surfaces, electrochemical reduction of diazonium salts on Si, which is one of the most industrially dominant material, is not well understood. Here, we report the electrochemical reduction of diazonium salts on a range of silicon electrodes of different crystal orientations (111, 211, 311, 411, and 100). We show that the kinetics of surface reaction and the reduction potential is Si crystal-facet dependent and is more favorable in the hierarchical order (111) > (211) > (311) > (411) > (100), a finding that offers control over the surface chemistry of diazonium salts on Si. The dependence of the surface reaction kinetics on the crystal orientation was found to be directly related to differences in the potential of zero charge (PZC) of each crystal orientation, which in turn controls the adsorption of the diazonium cations prior to reduction. Another consequence of the effect of PZC on the adsorption of diazonium cations, is that molecules terminated by distal diazonium moieties form a compact film in less time and requires less reduction potentials compared to that formed from diazonium molecules terminated by only one diazo moiety. In addition, at higher concentrations of diazonium cations, the mechanism of electrochemical polymerization on the surface becomes PZC-controlled adsorption-dominated inner-sphere electron transfer while at lower concentrations, diffusion-based outer-sphere electron transfer dominates. These findings help understanding the electro-polymerization reaction of diazonium salts on Si en route towards an integrated molecular and Si electronics technology.

Direct electrochemical grafting of crystalline PAEK macromolecule on carbon fiber to enhance the interfacial properties of PEEK/CF composites

Electrochemical grafting of diazonium salts have been applied to improve interfacial properties of carbon fiber and matrix resin. However, these graft modifications are still limited to general-purpose carbon fiber reinforced resin matrix composites such as epoxy. In this research, the direct grafting of Poly (aryl ether ketone) (PAEK) macromolecule on carbon fiber was achieved with mild condition. Firstly, aniline was introduced into Poly (ether ether ketone) (PEEK) as pendent group to improve solubility and amino terminated group was introduced as precursor of diazonium salt. Then the graft was conduct through diazonium salt reduction. After modification, the aniline side group could be hydrolyzed off to recover crystallinity. To further analyze the graft, single molecular-force spectroscopy was introduced to investigate the surface of carbon fiber. Impressively, the extension curve suggested the PAEK macromolecule had been attached to surface through strong interaction. Combined this with XPS data, it was believed that the graft was a success. As a result, the grafted polymer along with the polymer that physically absorbed on carbon fiber in electrolyte can cooperate to strengthen the interface. The interfacial shear strength of the grafted carbon fiber and PEEK increased from 42.27 MPa to 97.33 MPa by 130.26%. The improvement mainly originated from the covalent bonding that connected the carbon fiber and the graft coating layer as well as the great compatibility between the graft coating layer and the matrix resin. These results also demonstrated the possibility to graft high performance polymers on carbon fiber through one-step modifications.

Confinement Effect of Plasmon for the Fabrication of Interconnected AuNPs through the Reduction of Diazonium Salts.

This paper describes a rapid bottom-up approach to selectively functionalize gold nanoparticles (AuNPs) on an indium tin oxide (ITO) substrate using the plasmon confinement effect. The plasmonic substrates based on a AuNP-free surfactant were fabricated by electrochemical deposition. Using this bottom-up technique, many sub-30 nm spatial gaps between the deposited AuNPs were randomly generated on the ITO substrate, which is difficult to obtain with a top-down approach (i.e., E-beam lithography) due to its fabrication limits. The 4-Aminodiphenyl (ADP) molecules were grafted directly onto the AuNPs through a plasmon-induced reduction of the 4-Aminodiphenyl diazonium salts (ADPD). The ADP organic layer preferentially grew in the narrow gaps between the many adjacent AuNPs to create interconnected AuNPs. This novel strategy opens up an efficient technique for the localized surface modification at the nanoscale over a macroscopic area, which is anticipated to be an advanced nanofabrication technique.

Conceptual Developments of Aryldiazonium Salts as Modifiers for Gold Colloids and Surfaces.

Modified colloids and flat surfaces occupy an important place in materials science research due to their widespread applications. Interest in the development of modifiers that adhere strongly to surfaces relates to the need for stability under ambient conditions in many applications. Diazonium salts have evolved as the primary choice for the modification of surfaces. The term "diazonics" has been introduced in the literature to describe "the science and technology of aryldiazonium salt-derived materials". The facile reduction of diazonium salts via chemical or electrochemical processes, irradiation stimuli, or spontaneously results in the efficient modification of gold surfaces. Robust gold-aryl nanoparticles, where gold is connected to the aryl ring through bonding to carbon and films modified by using diazonium salts, are critical in electronics, sensors, medical implants, and materials for power sources. Experimental and theoretical studies suggest that gold-carbon interactions constructed via chemical reactions with diazonium salts are stronger than nondiazonium surface modifiers. This invited feature article summarizes the conceptual development of recent studies of diazonium salts in our laboratories and others with a focus on the surface modification of gold nanostructures, flat surfaces and gratings, and their applications in nanomedicine engineering, sensors, energy, forensic science, and catalysis.

In Memoriam of Jean‐Michel Savéant (1933–2020)

In Memoriam of Jean‐Michel Savéant (1933–2020)

Tuning the Covering on Gold Surfaces by Grafting Amino-Aryl Films Functionalized with Fe(II) Phthalocyanine: Performance on the Electrocatalysis of Oxygen Reduction.

Current selective modification methods, coupled with functionalization through organic or inorganic molecules, are crucial for designing and constructing custom-made molecular materials that act as electroactive interfaces. A versatile method for derivatizing surfaces is through an aryl diazonium salt reduction reaction (DSRR). A prominent feature of this strategy is that it can be carried out on various materials. Using the DSRR, we modified gold surface electrodes with 4-aminebenzene from 4-nitrobenzenediazonium tetrafluoroborate (NBTF), regulating the deposited mass of the aryl film to achieve covering control on the electrode surface. We got different degrees of covering: monolayer, intermediate, and multilayer. Afterwards, the ArNO2 end groups were electrochemically reduced to ArNH2 and functionalized with Fe(II)-Phthalocyanine to study the catalytic performance for the oxygen reduction reaction (ORR). The thickness of the electrode covering determines its response in front of ORR. Interestingly, the experimental results showed that an intermediate covering film presents a better electrocatalytic response for ORR, driving the reaction by a four-electron pathway.

Electrochemical modification at multiwalled carbon nanotube electrodes with Azure A for FAD- glucose dehydrogenase wiring: structural optimization to enhance catalytic activity and stability

Electrochemical grafting is a suitable technology for fabricating electrode surfaces with new chemical functionalities whilst maintaining the bulk properties of the electrode, and electrochemical amine oxidation and diazonium salt reduction are two widely used techniques to achieve this end. Herein, we report the electrochemical reductive grafting of Azure A onto multiwalled carbon nanotube (MWCNT) electrodes for the efficient wiring of flavin adenine dinucleotide (FAD) dependent glucose dehydrogenase. The diazonium salt of Azure A is formed in situ and subsequently grafted onto the electrode surface through electrochemical reduction. The formal potential of the resultant Azure-A-modified electrode shifted to −0.05 V vs. Ag/AgCl upon radical coupling to the MWCNT electrode. Electron transfer from FAD buried in the protein shell to the electrode via Azure A was then observed in the presence of glucose in the buffer solution. This study focused on the important effect of CNT mass loading on Azure-A loading as well as bioelectrocatalytic activity and storage stability. The three-dimensional porous structure of the MWCNT electrode was determined to be favorable for the immobilization of flavin adenine dinucleotide dependent glucose dehydrogenase and efficient electron transfer via the Azure-A functionalities. The optimized 300 µg CNT-loaded modified electrode on glassy carbon (3 mm diameter) retains its initial activity for 3 d and 25% of its initial activity after 10 d. Furthermore, we show that grafted Azure A is stably immobilized on the MWCNTs for 1 month; therefore, the limiting stability factor is enzyme leaching and/or deactivation.

One-step spontaneous grafting via diazonium chemistry for the fabrication of robust bionic multifunctional superhydrophobic fabric

Abstract A superhydrophobic cotton fabric with peanut leaf-like nanoplates, 3D flower-like and mulberry-like microstructure surface with varied water adhesion was fabricated via simple one-step spontaneous grafting method at room temperature. The spontaneous covalent grafting of 3,5-di(trifluoromethyl)phenyl functionalities to cotton fibers by the Fe0 reduction of the corresponding 3,5-di(trifluoromethyl)benzene diazonium salt has been studied in aqueous acid, which relates to the homolytic reduction of diazonium salts to produce radicals followed by grafting to the cotton fibers. We adjust the spontaneous grafting process by simply changing the molarity of HCl solutions to control the micro-nanostructures of β-FeOOH on the cotton fabric surfaces. Thus, the superhydrophobic surface adhesion forces to the water droplets can be effectively adjusted from 21.36 μN (lowest) to 159.35 μN (highest) via changing the surface architecture. The modified cotton fabric surface exhibited excellent superhydrophobicity with a water contact angle (WCA) of 167.2 ± 1.6°, sliding angle (WSA) of 1.8 ± 0.3° and superoleophilicity with the n-hexane contact angle (OCA) of 0°. Thus, the superhydrophobic cotton fabric can be used for self-cleaning and oil/water separation with an efficiency of as high as 98.9%, which has good recyclability, laundering and abrasion durability. Moreover, the movement of the superhydrophobic cotton fabric in water can be controlled by the orientation of a magnet without contact. Meanwhile, the micro-nanostructured rough surface with tunable adhesive force to water can be used to detect AgNO3 or NaOH in the aqueous solution, and so other potential applications in the droplet based microreactor can be found.

Three-color plasmon-mediated reduction of diazonium salts over metasurfaces.

Surface plasmon-mediated chemical reactions are of great interest for a variety of applications ranging from micro- and nanoscale device fabrication to chemical reactions of societal interest for hydrogen production or carbon reduction. In this work, a crosshair-like nanostructure is investigated due to its ability to induce local enhancement of the local electromagnetic field at three distinct wavelengths corresponding to three plasmon resonances. The structures are irradiated in the presence of a solution containing diazonium salts at wavelengths that match the resonance positions at 532 nm, 632.8 nm, and 800 nm. The resulting grafting shows polarization and wavelength-dependent growth patterns at the nanoscale. The plasmon-mediated reactions over arrays of the crosshair structures are further investigated using scanning electron microscopy and supported by finite domain time domain modelling revealing wavelength and polarization specific reactions. Such an approach enables nanoscale molecular printing using light source opening multiplexing applications where different analytes can be grafted under distinct opto-geometric conditions.

Antifouling nanofiltration membrane via tetrathioterephthalate coating on aniline oligomers-grafted polyethersulfone for efficient dye and heavy metal ion removal

A novel antifouling tetrathioterephthalate coated-aniline oligomers functionalized polyethersulfone nanofiltration (T-AO functionalized PES NF) membrane was developed for dye rejection and heavy metal ion removal. First, the PES NF membrane was in situ functionalized by aniline oligomers grafting through aryl diazonium salt reduction reaction and then the resulting functionalized PES NF membrane was coated with tetrathioterephthalate and characterized in terms of surface hydrophilicity, surface morphology, overall porosity, active pore radius, pore radius distribution, surface roughness, zeta potential, and active layer thickness. FTIR and XPS analysis were also carried out to confirm the desired functional groups were successfully formed on the tetrathioterephthalate coated-aniline oligomers functionalized PES NF (T-AO functionalized PES NF) membrane. The pure water flux and the flux recovery ratio of the T-AO functionalized PES NF membrane increased about 500.30 and 175.06 %, respectively, in comparison to the PES membrane due to the presence of hydrophilic functional groups belong to the coating layer. The resultant membrane with high water flux provided impressive heavy metal ion and dye removal. Moreover, this type of PES membrane showed excellent antifouling behavior and long-term stability; this work introduces an antifouling membrane for potential application in heavy metal ion and dye removal.

Development of a label-free electrochemical aptasensor based on diazonium electrodeposition: Application to cadmium detection in water

In this study we have developed a new aptasensor for cadmium (Cd2+) detection in water. Gold electrode surface has been chemically modified by electrochemical reduction of diazonium salt (CMA) with carboxylic acid outward from the surface. This was used for amino-modified cadmium aptamer immobilization through carbodiimide reaction. Chemical surface modification was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). This latter was also used for Cd2+ detection. The aptasensor has exhibited a good linear relationship between the logarithm of the Cd2+ concentration and the impedance changes in the range from 10−3 to 10−9 M with a correlation R2 of 0.9954. A high sensitivity was obtained with a low limit of detection (LOD) of 2.75*10−10 M. Moreover, the developed aptasensor showed a high selectivity towards Cd2+ when compared to other interferences such as Hg2+, Pb2+ and Zn2+. The developed aptasensor presents a simple and sensitive approach for Cd2+detection in aqueous solutions with application for trace Cd2+ detection in spring water samples.

Long-Range Charge Transport in Diazonium-Based Single-Molecule Junctions.

Thin layers of cobalt and ruthenium polypyridyl-oligomers with thicknesses between 2 and 8 nm were deposited on gold by electrochemical reduction of diazonium salts. A scanning tunneling microscope was used to create single-molecule junctions (SMJs). The charge transport properties of the Au-[Co(tpy)2]n-Au (n = 1-4) SMJs do not depend markedly on the oligomer length, have an extremely low attenuation factor (β ∼ 0.19 nm-1), and do not show a thickness-dependent transition between two mechanisms. Resonant charge transport is proposed as the main transport mechanism. The SMJ conductance decreases by 1 order of magnitude upon changing the metal from Co to Ru. In Au-[Ru(tpy)2]n-Au and Au-[Ru(bpy)3]n-Au SMJs, a charge transport transition from direct tunneling to hopping is evidenced by a break in the length-dependent β-plot. The three different mechanisms observed are a clear molecular signature on transport in SMJs. Most importantly, these results are in good agreement with those obtained on large-area molecular junctions.

Preparation oaf polyaniline/diazonium salt/TiO2 nanotube arrays as supercapacitor electrode by electrochemical grafting and deposition

Polyaniline/diazonium salt/TiO2 nanotube arrays (PANI/DZ/TiO2 NAs), as a supercapacitor electrode material, are fabricated by two-step anodic oxidation of titanium foils, electrochemical grafting and reduction of diazonium salts, and electrochemical deposition of polyaniline. Surface morphology, crystallization, and chemical compositions of nanocomposites are characterized by SEM, EDX, XRD, and Raman. Electrochemical tests indicate that PANI/DZ/TiO2 NAs have excellent capacitance of 1108.5 F g−1 when the current density is 0.6 A g−1. With the current density increasing 20 times to 12 A g−1, the capacitance remains about 77.5%, demonstrating its good rate performance. Moreover, after 2000 charge–discharge cycles at 12 A g−1, the capacitance retains 83.7% of the initial value, showing its good cycling stability.

Use of Selective Redox Cross-Inhibitors for the Control of Organic Layer Formation Obtained via Diazonium Salt Reduction.

The controlled electrochemical deposition of a series of four diazonium salts (4-bromobenzene, 4-iodobenzene, 4-methoxybenzene, and 4-diethylaminobenzene diazonium) on carbon surfaces has been achieved by exploiting the use of three redox mediators: 2,2-diphenyl-1-picrylhydrazyl, chloranil, and dichlone. The efficiency of the method rests on a fast redox cross-reaction in the diffusion layer between the diazonium compound and the reduced form of the selected inhibitor, characterized by an outer-sphere electron transfer. The effect of the inhibitor addition in the deposition solution was characterized using electrochemical techniques, X-ray photoelectron spectroscopy, and atomic force microscopy. Near-monolayers are obtained when the potential of the redox mediator is at least 100 mV lower than the reduction potential of the diazonium salt concerned. A judicious choice of the redox entity can allow, via a fine control of the experimental conditions, to modulate the thickness of organic layers by varying the grafting potential.

Functionalization of Cerium Oxide Nanoparticles to Influence Hydrophobic Properties.

Electroless functionalization of cerium oxide nanoparticles (NPs) based on the grafting of aryl groups from the reduction of diazonium salts is presented as a useful and facile method for enhancing the properties of the NPs. For this study, 4-methyl-, 4-ethyl-, and 4- n-butyl-benzene diazonium salts were used as model molecules to demonstrate the ability to change the hydrophobic properties of the cerium oxide (CeO2) NPs. The grafting reaction was investigated under two reducing environments: the addition of a chemical reducing agent and the use of cerium oxide's native reducing property. Spectroscopic evidence for the successful attachment of aryl groups to the CeO2 NPs was given by infrared and 13C SS-NMR, which clearly detect characteristic aryl C-C peaks and the alkyl chains. X-ray diffraction results confirmed that the NPs underlying the crystal structure was unaffected by the grafting process. Thermal gravimetric analysis of the NPs suggested that this method enables the formation of multilayers at the surface, as well as an increase in the hydrophobic character. Hydrophobic properties of the resultant NPs further examined with a water contact angle test on pressed pellets revealed increase in hydrophobicity with increasing alkyl chain length. This research opens up new possibilities for controlling the surface chemical composition of CeO2 NPs as well as other NPs using procedures operated in aqueous environments at room temperature.

Synthesis of 4-aminobenzenesulfonic acid functionalized carbon catalyst through diazonium salt reduction for biodiesel production

A series of carbon catalysts are synthesized through the arylation diazonium salt reduction approach from coal to catalyze esterification of oleic acid with methanol for biodiesel production. Under the activated carbon preparation temperature of 900 °C, mass ratio of 4-aminobenzenesulfonic acid to activated carbon of 6 and arylation temperature of 45 °C, the synthesized carbon catalyst gains the surface area and pore volume of 629.3 m2 g−1 and 0.29 cm−3 g−1, respectively. Besides, the carbon catalyst possesses abundant and strong active sites with the 4-sulfophenyl group density of 0.97 mmol g−1 and acid strength of 0.8 < pH < 3.3. Catalytic capability of the carbon catalyst, which is synthesized under the above optimized condition, in esterification is stronger than the commercial Amberlyst-15, where the maximum efficiency achieves 95.04% with the carbon catalyst added mass percentage of 12%, molar ratio of methanol to oleic acid of 10, esterification duration of 4 h and esterification temperature of 65 °C. Due to leaching of the 4-sulfophenyl groups, esterification efficiency declines to 77.63% for the fifth reused cycle of the carbon catalyst. Meanwhile, the regenerated carbon catalyst supplies the esterification efficiency of 86.05%. Chemical composition of the produced biodiesel is identical to pure methyl oleate and its fuel properties are in accordance with ASTM D 6751.