Functionalization Of Carbon Nanofibers Research Articles

Functionalization of Carbon Nanofibers with an Aromatic Diamine: Toward a Simple Electrochemical-Based Sensing Platform for the Selective Sensing of Glucose.

Despite a variety of glucose sensors being available today, the development of nonenzymatic devices for the determination of this biologically relevant analyte is still of particular interest in several applicative sectors. Here, we report the development of an impedimetric, enzyme-free electrochemical glucose sensor based on carbon nanofibers (CNFs) functionalized with an aromatic diamine via a simple wet chemistry functionalization. The electrochemical performance of the chemically modified carbon-based screen-printed electrodes (SPCEs) was evaluated by electrical impedance spectroscopy (EIS), demonstrating a high selectivity of the sensor for glucose with respect to other sugars, such as fructose and sucrose. The sensing parameters to obtain a reliable calibration curve and the selective glucose sensing mechanism are discussed here, highlighting the performance of this novel electrochemical sensor for the selective sensing of this important analyte. Two linear trends were noted, one at low concentrations (0-1200 μM) and the other from 1200 to 5000 μM. The limit of detection (LOD), calculated as the (standard error/slope)*3.3, was 18.64 μM. The results of this study highlight the performance of the developed novel electrochemical sensor for the selective sensing of glucose.

An experimental and theoretical approach to organic functionalization of carbon nanofibers using fresh neem leaves

Carbon nanofibers (CNF) are state-of-the-art materials that have been actively explored for several applications. In this study, we have given organic functionalization treatment to CNF using fresh neem leaves (FNL) following a simple ultrasonication methodology. The effects of dispersion treatment (using Triton X-100) on the functionalization of CNF are also investigated. The samples are characterized via FESEM, EDX, XPS, XRD, CHNS, XRF, and FTIR studies. The FESEM and XRD analyses confirm that the CNF morphology remains intact upon organic treatment. The EDX, XRF, CHNS, and FTIR studies reveal the functionalization of CNF with several heteroatoms (N: 7.41 at.%, O: 4.38 at.%, S: 0.027 at.%, P: 0.42 at.%, etc.), and nutrients present in the FNL. The electrocatalytic activity of the modified CNF is tested via cyclic voltammetry and linear sweep voltammetry studies in 0.1 M KOH electrolyte. The onset potential is −0.018 V, the half-wave potential is −0.35 V, and the limiting current density is 3.26 mA/cm2 for this sample. The oxygen reduction at FNL modified-CNF occurs via a four-electron pathway (n = 3.76) in the alkaline medium. The direct functionalization treatment of CNF is more effective for the observed intermolecular charge interactions between CNF and the FNL extract, however, the Triton X-100 coating on CNF acts as a mask to suppress these interactions. The simulation studies reveal that the upper and edge sites in the cup-stacked CNF are most active for ORR catalysis. It includes a detailed interaction study of the CNF-alanine molecule, which could be beneficial for designing novel biosensors.

Functionalization of CNFs surface with β-cyclodextrin and decoration of hematite nanoparticles for detection and degradation of toxic fungicide carbendazim

Fungicides are widely used across the globe in agricultural sector and their ubiquitous presence is a serious concern to ecology due to their hazardous nature. Hence, we report sensitive detection and degradation of the toxic fungicide carbendazim based on a novel dual-functional nanocomposite that consists of carbon nanofibers (CNFs), β-cyclodextrin (β-CD), and hematite (α-Fe2O3) nanoparticles. The surface functionalization of CNFs with the natural polymer β-CD and the subsequent decoration with α-Fe2O3 nanoparticles through a sonochemical method were detailed. Exceptional surface-controlled electrocatalytic activity has been achieved towards the detection of carbendazim, and we have confirmed this based on cyclic voltammetry and differential pulse voltammetry techniques. Furthermore, the excellent photocatalytic activity of the prepared nanocomposite towards carbendazim was verified by evaluating the degradation rate. Apart from very low limit of detection (LOD) of 1 nM and excellent sensitivity of 37.69 μA μM−1cm−2, outstanding anti-interference property, stability, reproducibility, and repeatability were also exhibited by the developed carbendazim sensor. Moreover, we detected carbendazim in real samples including apple, orange, tomato, and river water to evince excellent practical feasibility of the developed sensor.

Let It Catch: A Short‐Branched Protein for Efficiently Capturing Polysulfides in Lithium–Sulfur Batteries

AbstractUncovering the key contributions of molecular details to capture polysulfides is important for applying suitable materials that can effectively restrain the shuttle effect in advanced lithium–sulfur batteries. This is particularly true for natural biomolecules with substantial structural and compositional diversities strongly impacting their functions. Here, natural gelatin and zein proteins are first denatured and then adopted for fabrication of nanocomposite interlayers via functionalization of carbon nanofibers. From the results of experiment and molecular dynamic simulations, it is found that the lengths of the sidechains on the two proteins play critical roles. The short‐branched gelatin shows significantly stronger adsorption of polysulfides, as compared with zein comprising many long‐chain residues. The gelatin‐based interlayer, along with its good porous structures/electrical conductivity, greatly suppresses the shuttle effect and yields exceptional electrochemical performance. Furthermore, the implementation of proteins as functional binder additives further supports the finding that gelatin enables stronger polysulfide‐trapping. As a result, high‐loading sulfur cathodes (9.4 mg cm−2) are realized, which deliver a high average areal capacity of 8.2 mAh cm−2 over 100 cycles at 0.1 A g−1. This work demonstrates the importance of sidechain length in capturing polysulfides and provides a new insight in selecting and design of desired polysulfide‐binding molecules.

Novel insights into the dispersed and acid-mediated surface modification of the carbon nanofibers

Carbon nanofibers (CNF) are the state of art materials owing to their special morphological features. In the pristine form, they exhibit strong van der Waals interactions which keep them agglomerated. The actual potential of these nanofibers could be realized once these are unbundled. In this work, CNF have been dispersed with Triton X-100 during ultrasonication, and further functionalized using 3:1 mixture of H2SO4 and HNO3 via reflux method. The effects of different concentrations of Triton X-100 (1–3 ml) on the dispersion and functionalization of CNF have been studied. CNF have been functionalized with O, N and S functionalities. The results have been elicited using FESEM, EDS, FTIR and RAMAN techniques. Triton X-100 wrapping covers up many (if not all) of the reactive edge sites on CNF. Additionally, the Cloud point phenomenon has been observed owing to the temperature behavior of adsorbed Triton X-100 layers on to CNF. Direct functionalization of CNF has been observed to be destructive towards their morphology. Acid functionalized CNF are intended for the electrochemical, nanocomposites, ink-jet printing, sensing applications etc.

Electrocatalytic Performance of Palladium-Based Electrocatalysts Supported on Carbon Nanofibers for Formic Acid Oxidation

In the last decades, fuel cells have been considered as an alternative power source for electric portable devices. Direct formic acid fuel cells (DFAFC) have attracted particular interest, since formic acid is safe, environmentally-friendly and non toxic. Also, it exhibits high-energy density and fast oxidation kinetics compared with other fuels, such as methanol and ethanol [1]. Palladium electrocatalysts supported on different carbon materials have been widely used for the formic acid oxidation reaction (FAOR). However, further research is still necessary as Pd deactivates during the FAOR. In order to overcome this limitation, Pd-Metal alloys have been proposed [3-5]. Pd, and PdFe nanoparticles supported on the carbon nanofibers with and without functionalization (NFC and NFCox) have been used for the FAOR in acid media. Electrocatalysts were synthesized by the borohydride reduction method with a metal loading of 20 wt.%. The morphology, composition and structural properties of the electrocatalysts were studied by transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive X-ray (SEM-EDX) and X-ray diffraction (XRD). The ROAF was evaluated in acid media in a conventional three-electrode cell by means of cyclic voltammetry (VC) and chronoamperometry (CA). The electrochemical behavior of Pd-based electrocatalysts for the FAOR showed that the functionalization of carbon nanofibers (NFCox) increased the electrocatalytic activity of Pd and PdFe electrocatalysts compared with the same electrocatalysts supported on NFC, as shown in Figure 1. X. Yu, P. Pickup, Journal of Power Sources,. 182(124-132) (2008)K. Jiang, H. Xuan, S. Zou, W. Bin, Phys. Chem. Chem. Phys., 16(20360-20376) (2014)H. Meng, F. Xie, J. Chen, P. Kang, Journal of Materials Chemistry., 21(11352-11358) (2011)D. Morales, J. Ledesma, L. Godinez, H. Rodríguez, L. Álvarez, L. Arriaga, Journal of Power Sources., 195(461-465) (2010)L. Zhang, L. Wan, Y. Ma, Y. Chen, Y. Zhou, Y. Tang, T. Lu, Applied Catalyst B: Environmental., 138-139(229-235) (2013). Figure 1

A highly conducting flower like Au nanoparticles interconnected functionalized CNFs and its enhanced electrocatalytic activity towards hydrazine through direct electron transfer

Abstract A numerous number of carbon-based nanomaterials have been developed for various technological applications, nevertheless a degree of accessibility is very less. Notably, carbon nanofibers (CNFs) based materials are insufficiently studied compare to CNT and graphene due to their inaccessibility in aqueous dispersion. Here we have functionalized the CNF by using acid treatment for further modification. Functionalization of CNF was confirmed by different characterization techniques like FT-IR, RAMAN, and XRD. To increase the electrical conductivity of F-CNFs, flower-like Au nanoparticles were electrodeposited onto the F-CNFs. Optimization study for electrodeposition of Au nanoparticles was performed with Au precursor's concentration and deposition cycle number. As the result, the optimal electrochemical active surface area (EASA) of the modified electrode is obtained to be 1.67 cm2 for 20 cycles which are higher than that of the previously reported Au nanoparticles based literature. The developed material was used as an electrode modifier for the detection of hydrazine. As expected, the amperometric hydrazine sensor shows a very low detection limit of 8 nM with a high sensitivity of 7.5 µA µM−1 cm−2. The excellent analytical parameters of the F-CNF@Au/GCE modified electrode over the various related modified electrodes suggest that the electrode can be useful for use in trace level detection of hydrazine in several industrial and pharmaceutical applications.

Synthesis of Carbon Nanofibers with Maghemite via a Modified Sol-Gel Technique

Carbon nanohybrid material (CNF/γ-Fe2O3) was obtained via a modified sol-gel technique consisting of two steps: functionalization of carbon nanofibers (CNF) in H2SO4/HNO3 followed by synthesis using Fe(NO3)3∙9H2O. As a result, the iron content of the CNF/γ-Fe2O3 was increased by more than twice from about 40% to about 87% mass percent, compared to the pristine CNF and oxidized CNF specimens, as proved by energy dispersive X-ray fluorescence. Scanning electron microscopy images exhibited “cumulus” on the CNF/γ-Fe2O3 specimen surface, which showed the highest iron mass percentage, proved by energy dispersive X-ray spectroscopy. Transmission electron microscopy images confirmed attachment of γ-Fe2O3 cumulus to the inner and outer surfaces of the CNF walls after synthesis. The characteristic peaks of Fe 2p3/2 and Fe 2p1/2 appeared in the XPS spectra obtained on CNF/γ-Fe2O3. In addition, X-ray diffraction (XRD) results indicated formation of γ-Fe2O3 during the synthesis process. The Raman spectrum of the CNF/γ-Fe2O3 sample displays peaks with positions close to characteristic peaks of highly crystalline and monodisperse maghemite nanocrystallites. The synthesis of CNF/γ-Fe2O3 leads to an increase in the hydrophilicity of CNF and magnetic properties at room temperature.

Plasma Functionalization of Carbon Nanofibers with Vapors of Ammonia/Water

The plasma treatment and characterization of carbon nanofibers (CNFs) using vapors of ammonia/water (NH3/H2O) is reported. CNFs were treated at an input power of 20 and 40 W for 60 min using an inductive RF plasma of 13.56 MHz. During the plasma treatment, the ions were measured in situ using an optical emission spectrometer. Changes in the chemical composition, morphology and percent of functional groups grafted onto the CNFs were studied by infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and thermogravimetrical analysis. As a result of the treatment, a higher oxygen and nitrogen concentration on the surface of CNFs has been obtained, resulting in a good dispersion of the treated CNFs in water and acetone. The emission spectra indicated the formation of ions of CO, which are associated with the purification of the CNFs as indicated by an increase of the sp2/sp3 ratio from 4.3 to 7.5. The fibrillar structure of the treated CNFs was not damaged by the NH3/H2O plasma treatment.

A facile route to carboxylated carbon nanofibers and their functionalization by robust octasilsesquioxanes via conjugated linkage

We describe here a facile two-step synthesis of hybrid nanocomposites based on one-dimensional carbon nanofibers (CNFs) decorated with cubic octasilsesquioxane (T8). The functionalization of CNFs with oxalyl chloride, via Friedel–Crafts acylation reaction in the presence of aluminum chloride, was first demonstrated as an efficient way to introduce carboxyl acid groups onto the nanofiber sidewalls. Octa-aminophenylsilsesquioxane (OASQ) was then covalently attached to the carboxylated nanocarbon CNF–(COOH)n through amide linkage. The CNFs were characterized by a set of material characterization methods including FTIR, Raman, solution 1H NMR spectroscopy, Auger electron spectroscopy (AES), thermogravimetric analysis and transmission electron microscopy (TEM) at each step of the functionalization. The results clearly show that the formation of the conjugated carboxylic acid moiety, due to the nature of the substitution, occurs at defect sites on the carbon nanofibres and the carboxylation degrees can be controlled by variation of the reaction conditions. High-resolution TEM observations and physisorption data reveal that OASQ domains are uniformly distributed on the surface with an average particle size of 5 nm and T8 cage probably remains intact during the decoration process.

Polycarboxylation of carbon nanofibers under Friedel–Crafts condition: A simple route to direct binding of carboxylic functionalities to graphitic π-system

The functionalization of carbon nanofibers (CNFs) with oxalyl chloride, via Friedel–Crafts reaction in the presence of aluminum chloride, was first demonstrated as an efficient way to introduce carboxyl groups onto the nanofiber sidewalls. Octa-aminophenylsilsesquioxane (OASQ) was then covalently attached to the carboxylated nanocarbon CNF–(COOH)n through amide linkage. Taking into account the nature of the electrophilic aromatic substitution, this chemical functionalization may involve formation of conjugated carboxylic acid moiety. Structural analysis combined with electron microscopy observation of the robust octasilsesquioxane species show that carboxyl groups are uniformly distributed on the nanofibers surface.

Efficient Synthesis of Pt Nanoparticles Supported on Hydrophobic Graphitized Carbon Nanofibers for Electrocatalysts Using Noncovalent Functionalization

AbstractAs an alternative to the oxidative acid treatment, a noncovalent π–π interaction method is employed to deposit Pt electrocatalysts on highly hydrophobic carbon nanofibers (CNFs) for the application of polymer electrolyte membrane (PEM) fuel cells. Three different functionalization agents, namely benzyl mercaptan (BM), 1‐aminopyrene (AP), and 1‐pyrenecarboxylic acid (PCA), are used to functionalize CNFs and the effect of these groups on the electrochemical properties is examined. While the BM and AP act as a poison to Pt catalyst, the functionalization of CNF with PCA improves the distribution and loading of Pt as well as reducing the sintering of Pt particles. From the carbon corrosion test, unlike the oxidative acid treatment, the PCA treatment sustains the corrosion resistance of CNFs because it preserves the intrinsic properties of CNFs without damaging their surface structure. Therefore, the PCA treatment is a very effective way to prepare catalysts for PEM fuel cells and also extended to the fabrication of graphitized‐carbon‐supported catalysts of other precious metal for various applications.

Noncovalent Modification of Carbon Nanofibers Using 2-Naphthalenethiol for Catalyst Supports in PEM Fuel Cells

ABSTRACT: A new synthesis method for the preparation of Pt electrocatalysts on carbon nanofibers (CNFs) isreported. In this method, Pt electrocatalysts are loaded onto 2-naphthalenethiol (NT) functionalizedCNFs. The noncovalent functionalization of CNFs by NT is the effective way for better distributionof Pt particles and higher electrocatalytic activity in polymer electrolyte membrane fuel cells. It wasfound that the presence of NT acts as a poison to catalysts. Therefore, it is necessary to remove NTthrough the heat treatment at 400 o C.Keywords : 2-naphthalenethiol, Graphitized carbon, Non-covalent functionalization, PEM fuel cell Received December 13, 2010 : Accepted December 27, 2010 1. Introduction Carbon black (CB) is the typical catalyst supportmaterial for polymer electrolyte membrane (PEM) fuelcells. However, the intrinsic drawback in use of CBas catalyst support is electrochemical carbon corrosion.Many studies reported that electrochemical carbon cor-rosion occurring during fuel cell start-up and shut-downprocess is one of the major contributors to performancedegradation of PEM fuel cells.

Effect of amine functionalization of CNF on electrical, thermal, and mechanical properties of epoxy/CNF composites

This paper presents experimental results of the effect of amine functionalization of carbon nanofibers (CNF) on the electrical, thermal, and mechanical properties of CNF/epoxy composites. The functionalized and non-functionalized CNFs (up to 3 wt%) were dispersed into epoxy using twin screw extruder. The specimens were characterized for electrical resistivities, thermal conductivity (K), UTS, and Vicker’s microhardness. The properties of the nanocomposites were compared with that of neat epoxy. The volume conductivity of the specimens increased by E12 S/cm and E09 S/cm in f-CNF/epoxy and CNF/epoxy, respectively, at 3 wt% filler loading. The increase in K for former was 106% at 150 °C, while for the latter it was only 64%. Similarly, UTS increased by 61% vs. 45% and hardness 65% vs. 43%. Tg increased with increase in filler content. SEM examinations showed that functionalization resulted in better dispersion of the nanofibers and hence greater improvement in the studied properties of the nanocomposites.

Functionalization of carbon nanofibers through electron beam irradiation

Carbon nanofibers were oxidized in air at 350°C under the influence of a 3MeV electron beam at doses of 1000 and 3500kGy. XPS analysis showed that oxygen was readily incorporated on the surface: the ratio O 1s/C 1s increased approximately by a factor of three when the carbon nanofibers were irradiated at 3500kGy. The oxidized nanofibers exhibited better dispersion than as-received nanofibers when mixed with water/methanol (50% v/v). Raman spectroscopy revealed that the ID/IG ratios were statistically unchanged for all samples because the damage on the nanofiber surface was highly localized and did not lead to modifications on the bulk carbon nanofiber structure. On the other hand, SEM, TEM, and AFM images illustrated that cutting, welding, and collapse may occur on the structure of irradiated nanofibers. BET analysis showed that the surface area of irradiated samples did not significantly increase, probably because the radiation process may lead to micro-porosity formation. The temperature during irradiation had no effect on the nanofibers’ surface and the thermal stability of the irradiated samples was determined to be lower.

A New Strategy to Pretreat Carbon Nanofiber and Its Application in Determination of Dopamine

A novel sonochemical process, using hydrogen peroxide in a laboratory ultrasonic bath, was employed to pretreat the carbon nanofiber (CNF) for creating oxygen‐rich groups on the surface of CNF. After the sonochemical process, the CNF showed good hydrophilicity and high electrochemical activity. Compared to normal pretreatment process, this sonochemical process is timesaving and effective for dispersion and functionalization of CNF. The resulting CNF showed high catalytic activity toward the oxidation of DA. A carbon paste electrode modified by CNF (CPE‐CNF) was used to determine the dopamine (DA) in the presence of ascorbic acid (AA). The detection limit is 0.05 μM, with the linear range from 0.05 μM to 6.4 μM.

The Diels-Alder Cycloaddition Reaction in the Functionalization of Carbon Nanofibers

Carbon nanofibres were functionalized by a Diels-Alder cycloaddition reaction of 1,3-butadiene, generated in situ from sulfolene. The experimental conditions were selected on the basis of a differential scanning calorimetry (DSC) study on the reagents and the functionalization was confirmed by thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Analysis performed on the surface of the functionalized material by X-ray photoelectron spectroscopy (XPS) and FT-IR using the Attenuated Total Reflectance (ATR) technique indicates that the carbonyl and sulfoxide groups are present on the surface of the functionalized material. The acidic surface of the functionalized nanofiber suggests the presence of carboxylic acid and possibly sulfonic acid groups.

The functionalization of carbon nanofibers with 4,4′-diaminodiphenylmethane, a curing agent for epoxy resins

A functionalization technique for carbon nanofibers (CNFs) via acid is described. The integrity and chemical nature of the CNFs during the different stages of the applied treatment (oxidation, activation, and functionalization) were examined using different microscopic, chemical, and thermal analysis techniques. The treatment effect on the dispersion ability of the nanofibers in different solvents (tetrahydrofuran, chloroform, and acetone) was also evaluated. Results show that chloroform is the best medium to reach good dispersions and stability of the CNFs in a wide range of concentrations. Using this medium, the functionalization process using 4,4′-diaminodiphenylmethane (DDM) was adopted for the fabrication of reactive CNFs with linker molecules on their surface capable of binding covalently to thermosetting polymers, such as epoxy. The DDM surface derivatized CNFs have been used as reinforcement in epoxy matrix nanocomposites with improved thermomechanical properties in relation to non-treated carbon nanofibers.

Grafting of polystyrene on carbon nanofibers by introducing a methacrylate unit

BACKGROUND: To overcome the self-agglomeration of carbon nanofibers (CNFs), a number of studies have dealt with surface modification of CNFs to improve their wettability. In this work, a novel, simple and practical approach based on the introduction of methacrylate units to graft polymers onto the surface of CNFs is proposed. RESULTS: The functionalized CNF samples were characterized using Fourier transform infrared and Raman spectroscopy, thermal gravimetric analysis and transmission electron microscopy. The molecular weight of grafted polystyrene (PS) is influenced by the monomer feed ratio. The stabilities of various CNF dispersions were measured using an optical analyzer. When the content of grafted PS is 34.2%, the functionalized CNFs attain a stable dispersion in xylene. CONCLUSION: In the presence of methacrylate units, PS has been successfully grafted onto the surface of CNFs via an in situ polymerization. Moreover, the introduction of methacrylate units opens the functionalization of CNFs to other routes. Copyright © 2009 Society of Chemical Industry

Organic functionalization of carbon nanofibers for composite applications

AbstractThe present work reports the study of the effect of different chemical functionalization methods on the interfacial characteristics of the polymer composites formed. The chemically modified carbon nanofibers were blended with polypropylene (PP) and PP modified with maleic anhydride on a mini twin‐screw extruder. The functionalization methods were designed for minimum fiber damage and enhanced fiber/matrix interactions by chemical reaction of the functional groups introduced at the nanofibers surface with the maleic anhydride grafted at the PP. The degree of nanofiber functionalization was studied using thermogravimetric analysis. The composites were analyzed for nanofiber dispersion, mechanical properties, and electrical resistivity. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers