Unzipping Of Multi-walled Carbon Nanotubes Research Articles

Synthesis of unzipped multi-walled carbon nanotube oxides coated polyurethane foam and its application in wastewater treatment

Unzipped multi-walled carbon nanotube oxides (UMCNOs) were prepared from multi-walled carbon nanotubes by using oxidative unzipping method. Different concentrations of UMCNOs were coated on polyurethane (PU) foam through dip coating method. Changes in the surface texture of the polyurethane foam after coating with UMCNOs was observed using SEM analysis. The UMCNOs- PU foam exhibited good hydrophobicity with a maximum water contact angle (WCA) of 128° for the PU sample coated with 2% (w/v) UMCNOs. The UMCNOs-PU foams were found to be effective absorbent for oil and organic solvents, with the absorption capacity, varies between 15 and 27 g/g. A maximum of 99.64% dye removal was observed in PU foam coated with 2% (w/v) UMCNOs as analyzed by UV-VIS analysis. Water contact angle of UMCNOs-2.0PU foam decreased after each recycle experiment and its characteristics were analyzed using FTIR.

Rational structure design for enhanced uranium(VI) capture and beyond: From carbon nanotubes to graphene oxide nanoribbons

Graphene oxide nanoribbons (GONRs) that are derived from chemical unzipping of multi-walled carbon nanotubes (MWCNTs) for uranium capture have been reported, but little is known about the complex chemical interactions between uranium(VI) and GONRs with different unzipping level. An unzipping process from MWCNTs to GONRs was identified using field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, X-ray powder diffraction (XRD), Fourier transformed infrared (Ft-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The uranium(VI) adsorption performances of GONRs with different unzipping level were investigated, and the enhanced U(VI) capture was closely related to their structures and surface oxygen-containing functional groups. The interaction mechanism at the molecular level demonstrated that UO22+ mainly complexed with carboxyl and hydroxyl groups at the edges of the GONRs. In addition, further functionalization has been proposed for expanding the potential applications of GONRs.

Partially unzipped multi-walled carbon nanotubes—promising material for oxygen electrodes of fuel cells

Partially unzipped multi-walled carbon nanotubes were used as an active layer of the oxygen electrodes. The obtaining of partially unzipped carbon nanotubes was confirmed by X-ray diffraction, transmission electron microscopy and Raman spectroscopy. An investigation of the electrocatalytic characteristics of such oxygen electrodes was carried out in a fuel half-cell with an alkaline electrolyte. Electrochemical studies have established that the obtained partially unzipped multi-walled carbon nanotubes are promising materials as a catalyst carrier for oxygen electrodes of fuel cells. The oxygen electrodes based on the electrochemically obtained carbon materials were stable for six months at a discharge current density of 200 mA cm−2.

Preparation and Electroactivity of Pt Catalysts on Unzipped Multi-Walled Carbon Nanotube and Graphene Oxide

We synthesize the Pt-carbon composite which is composed of unzipped multi-walled carbon nanotube (UMWCNT) and graphene oxide (GO). Graphite and multi-walled carbon nanotube (MWCNT) are oxidized by same method that modified Hummer's method for making GO and UMWCNT. 3D structure could be prepared by polyol process which contains simultaneously reduction GO and UMWCNT. The electrochemical and morphological property of Pt-carbon composites was investigated by Fourier Transform Infrared spectroscopy (FT-IR), Field Emission Scanning Electron Microscopy (FE-SEM), and Cyclic Voltammetry (CV). These results show that Pt-rGO/UMWCNT (8:2) hybrids exhibited high catalytic activity due to the enhanced surface area of carbon supports.

Unzipping carbon nanotubes to nanoribbons for revealing the mechanism of nonradical oxidation by carbocatalysis

Graphitic multi-walled carbon nanotubes (MWCNTs) are controllably unzipped into edge-rich graphene nanoribbons to reveal the roles of edges and defects in persulfate activation for bisphenol A (BPA) oxidation. Enriched carbon edges remarkably enhance the catalytic performance and can serve as hosting sites for heteroatom (N, S) doping to promote carbocatalysis. A sample (NS-2) presented a complete BPA removal in 20 min at a rate constant of 0.182 min-1. The rate constants were relating to the defect speciation in a negative correlation to an indicator (ID/ID’) from Raman spectra. Excessive edges induce defects and structure transformation of sp2 to sp3, resulting in deterioration of the organic oxidation. Furthermore, unzipped MWCNTs were clarified to follow a nonradical electron transfer pathway by radical screening tests, in situ Raman and electrochemical characterizations. The unveiled mechanism emphasizes the importance of an essential graphitic degree and conductivity in the edge-enriched carbocatalysts for better catalytic performance.

Graphene Oxide Nanoribbons in Chitosan for Simultaneous Electrochemical Detection of Guanine, Adenine, Thymine and Cytosine.

Herein, graphene oxide nanoribbons (GONRs) were obtained from the oxidative unzipping of multi-walled carbon nanotubes. Covalent coupling reaction of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxy succinimide (NHS) with amine functional groups (-NH2) of the chitosan natural polymer (CH) was used for entrapping GONRs on the activated glassy carbon electrode (GCE/GONRs-CH). The nanocomposite was characterized by high-resolution transmission electron microscopy (HRTEM), and field-emission scanning electron microscopy (FESEM). In addition, the modification steps were monitored using FTIR. The nanocomposite-modified electrode was used for the simultaneous electrochemical determination of four DNA bases; guanine (G), adenine (A), thymine (T) and cytosine (C). The nanocomposite-modified GCE displayed a strong, stable and continuous four oxidation peaks during electrochemistry detection at potentials 0.63, 0.89, 1.13 and 1.27 V for G, A, T and C, respectively. The calibration curves were linear up to 256, 172, 855 and 342 μM with detection limits of 0.002, 0.023, 1.330 and 0.641 μM for G, A, T and C, respectively. The analytical performance of the GCE/GONRs-CH has been used for the determination of G, A, T and C in real samples and obtained a recovery percentage from 91.1%–104.7%. Our preliminary results demonstrated that GCE/GONRs-CH provided a promising platform to detect all four DNA bases for future studies on DNA damage and mutations.

A facile and scalable approach to develop electrochemical unzipping of multi-walled carbon nanotubes to graphene nanoribbons

Unzipping of multi-walled carbon nanotubes (MWCNTs) is a promising strategy for scalable preparation of graphene nanoribbons (GNRs).

Facile synthesis of SnO2 nanoparticle intercalated unzipped multi-walled carbon nanotubes via an ultrasound-assisted route for symmetric supercapacitor devices

SnO2 nanoparticle intercalated unzipped multi-walled carbon nanotubes via an ultrasound-assisted route for symmetric supercapacitor devices.

OBTAINING PARTIALLY UNZIPPED CARBON NANOTUBES FOR OXYGEN ELECTRODES

Various methods for unzipping carbon nanotubes are described, which differ only in the method of acting on multi-walled carbon nanotubes which leads to obtain a partial unzipped carbon nanotubes or the creation of a defective hybrid structure in carbon nanotubes.
 By electrochemical anodic oxidation in 80 % sulfuric acid of multi-walled carbon nanotubes synthesized partially unzipped nanotubes and shows the results of the study. Using the methods of X-ray phase analysis, electron microscopy, and Raman spectra, it has been established that, as a result of electrochemical anodic oxidation, partially unzipped multi-walled carbon nanotubes are obtained. Two-layer oxygen electrodes were made, where synthesized materials were used as an active layer. Studies of the electrocatalytic characteristics of oxygen electrodes from partially unzipped multi-walled carbon nanotubes were carried out in a mock up of fuel cell with alkaline electrolyte. It is established that the degree of unzipping of multi-walled carbon nanotubes depends on the time of electrochemical oxidation. It has been suggested that it is possible to control the process of synthesis of partially unzipped nanotubes. It has been established that one of the methods for estimating the degree of unzipping of multi-walled carbon nanotubes can be studies the electrochemical characteristics of oxygen electrodes based on these materials.
 Electrochemical investigation has established that the obtained samples of partially unzipped multi-walled carbon nanotubes are promising materials as catalysts carrier for oxygen electrodes of fuel cells. The developed method synthesis of partially unzipped multi-walled carbon nanotubes allows obtaining electrode materials for chemical current sources. Oxygen electrodes, based on such electrochemically produced materials, were stable for six months at a discharge current density of 200 mA/cm2. Partially unzipped multi-walled carbon nanotubes are promising catalyst carrier for electrodes of chemical current sources, as well as a material for hybrid nanocomposites with predetermined characteristics.

Electrochemical Synthesis Partially Unzipped Multi-Walled Carbon Nanotubes as Electrode Materials for Fuel Cells

Results of electrochemical anodic oxidation of multi-walled carbon nanotubes in 80% sulfuric acid are presented. Using X-ray diffraction analysis, electron microscopy, and Raman spectra, it has been proven that, as a result of anodic oxidation, partially unzipped multi-walled carbon nanotubes were obtained by anodic oxidation. It is shown that the degree of unzipping multi-walled carbon nanotubes depends on the time of electrochemical oxidation of these materials. Using the oxygen electrode as testing electrodes was shown the dependence of the electrochemical characteristics of these materials of the degree of unzipping the multi-walled carbon nanotubes. It is suggested that the controlled synthesis of partially unzipping nanotubes is possible. It is also suggested that it is possible to estimate the degree of unzipping the nanotube based on the study of the electrochemical characteristics of oxygen electrodes. By the electrochemical method obtained partially unzipped multi-walled carbon nanotubes which are promising electrode materials.

Unzipped carbon nanotubes for aluminum battery

As low-cost commercial materials, the application of carbon nanotubes (CNTs) in the aluminum battery is limited by the lack of active intercalation sites. Herein, a flexible unzipped multi-walled carbon nanotubes (UCNTs) film consisting of graphene nanoribbons and a carbon nanotube backbone is prepared via a simple, low-cost and scalable method for high-performance aluminum battery positive electrode. In the nanostructure, the neonatal graphene nanoribbons provide numerous active intercalation sites to store AlCl4− anions, while the internal core CNTs are responsible for the rapid transportation of electrons to the active sites. Fast transportation of electrons and anions in UCNT film are simultaneously achieved, promoting the kinetics in the aluminum battery. Thus the UCNT-Al battery exhibits a high storage performance with a capacity as high as 100 mA h g−1 (current density: 2000 mA g−1) and a long cycle life of 5600 cycles with a capacity of 75 mA h g−1 (Coulombic efficiency: 98%) at 5000 mA g−1. Furthermore, the excellent flexibility and fast charging and variable discharging performance are beneficial for the development of portable devices. This work effectively tackles bottleneck caused by the lack of active sites for CNT-based aluminum batteries and accelerates the development of aluminum batteries.

Thorium adsorption on graphene oxide nanoribbons/manganese dioxide composite material

A functional graphene oxide nanoribbons/manganese dioxide composite material (MnO2-GONRs) was synthesized by hydrothermal method using graphene oxide nanoribbons (GONRs) as raw material which were formed by longitudinal unzipping of multi-walled carbon nanotubes with KMnO4 and H2SO4. The microstructure of MnO2-GONRs was characterized by SEM and FT-IR. The various factors affecting the adsorption of Th(IV) in aqueous solution such as pH, solid–liquid ratio, contact time, initial concentration and temperature were investigated by batch static adsorption experiments, and the adsorption mechanism is also discussed. The results showed that MnO2-GONRs had a good adsorption effect on Th(IV) with a maximum adsorption of 166.11 mg/g.

Synthesis of magnetic graphene oxide nanoribbons composite for the removal of Th(IV) from aqueous solutions

Functionalized magnetic graphene oxide nanoribbons (MGONRs) composite material was synthesized by hydrothermal treatment method using graphene oxide nanoribbons as raw material, which was formed by longitudinal unzipping of multi-walled carbon nanotubes in oxidizing environment. The morphology and structural properties of MGONRs were characterized by SEM, FT-IR, XRD and VSM and thorium adsorption behavior on MGONRs was investigated. The results showed that thorium adsorption on MGONRs was pH-dependent, endothermic and spontaneous. The adsorption process followed pseudo-second order and Freundlich isotherm model with rapid solid–liquid separation. MGONRs could have practical application in separation and recovery of thorium from aqueous solutions.

Covalent bonding of sulfur nanoparticles to unzipped multiwalled carbon nanotubes for high-performance lithium–sulfur batteries

The use of sulfur as a cathode material for lithium−sulfur (Li−S) batteries has attracted significant attention due to its high theoretical specific capacity (1675 mA h g−1); however, practicality is hindered by a number of obstacles, including the shuttling effect of polysulfides and the low electrical conductivity of sulfur. Herein, ball milling sulfur with unzipped multiwalled carbon nanotubes (UMWNTs) was found to covalently immobilize sulfur nanoparticles to the UMWNTs and resulted in composites (designated as S@UMWNTs) with high electrical conductivity. The unzipping degree of MWNTs was first controlled to optimize the immobilization of sulfur nanoparticles to UMWNTs and the electrochemical performance of the resulting Li−S batteries. The presence of C−S covalent bonds between the UMWNTs and sulfur nanoparticles was verified using x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, and the formation of C−S bonds was ascribed to the reactions between the mechanically-induced sulfur radicals and the functional groups of UMWNTs. As a result, when used as a cathode material for Li−S batteries, the S@UMWNTs exhibited excellent electrochemical performance, including a good long-term cycling stability and low capacity decay (e.g., ca. 0.09% per cycle over 500 charge/discharge cycles at 1 C) due to the suppression of the shuttling effect by the C−S covalent bonds.

Synthesis of UMCNOs from MWCNTs and analysis of its structure and properties for wastewater treatment applications

Multi-walled carbon nanotubes (MWCNTs) are non-polar carbon tubes having poor dispersion capability in different solvents. To overcome this limitation, the oxidative unzipping of MWCNTs was done and results in the preparation of unzipped multi-walled carbon nanotube oxide (UMCNOs). The UMCNOs was characterized using field-emission scanning electron microscope, Fourier transformed infrared spectrophotometer, and X-ray diffractometer. The hybrid structure was able to improve the accessible areas significantly due to the availability of both outer and inner walls of MWCNTs. UMCNOs-cotton sponge was prepared by dipping commercial cotton in unzipped carbon nano-oxide dispersion and drying in a vacuum oven. UMCNOs-Cot sponge exhibits hydrophilic and hydrophobic properties at different conditions showed its amphiphilic nature. Hydrophobic properties of UMCNOs lower the interfacial energy of the coated cotton surface with a maximum water contact angle of 145° and super-oleophilicity showed the absorption capacity of oil from an oil/water mixture. These UMCNOs-Cot sponges were applied for the separation of oils, organic solvents with absorption capacities in the range of 21–43 times as compared to its weight. A significant loss of bacterial cell viability up to 99% was also achieved with this UMCNOs-Cot sponge.

Revisiting the Mechanism of Oxidative Unzipping of Multiwall Carbon Nanotubes to Graphene Nanoribbons.

Unzipping multiwall carbon nanotubes (MWCNTs) attracted great interest as a method for producing graphene nanoribbons (GNRs). However, depending on the production method, the GNRs have been proposed to form by different mechanisms. Here, we demonstrate that the oxidative unzipping of MWCNTs is intercalation-driven, not oxidative chemical-bond cleavage as was formerly proposed. The unzipping mechanism involves three consecutive steps: intercalation-unzipping, oxidation, and exfoliation. The reaction can be terminated at any of these three steps. We demonstrate that even in highly oxidative media one can obtain nonoxidized GNR products. The understanding of the actual unzipping mechanism lets us produce GNRs with hybrid properties varying from nonoxidized through heavily oxidized materials. We answer several questions such as the reason for the innermost walls of the nanotubes remaining zipped. The intercalation-driven reaction mechanism provides a rationale for the difficulty in unzipping single-wall and few-wall CNTs and aids in a reevaluation of the data from the oxidative unzipping process.

Facile longitudinal unzipped multiwalled carbon nanotubes incorporated overoxidized poly(p-aminophenol) modified electrode for sensitive simultaneous determination of dopamine, uric acid and tryptophan

In the present work, unzipped multiwalled carbon nanotube oxides (UMCNOs) was obtained from longitudinally unzipped multiwalled carbon nanotubes (MWCNTs) by the Hummers method. This hybrid structure could significantly improve the accessible area since both the outer and inner wall of MWCNTs are available. Then a novel strategy based on overoxidized poly(p-aminophenol) (pAPox) and UMCNOs copolymer modified electrode was proposed for the simultaneous determination of dopamine (DA), uric acid (UA), and tryptophan (Trp). Besides, the coexistence of ascorbic acid (AA) has no interference toward the detection of DA, UA and Trp. Also, scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), cyclic voltammetry (CV) and different pulse voltammetry (DPV) were employed to characterize the copolymer. Under the optimal conditions, two linear calibrations for DA and Trp were obtained over ranges of 15.0–95.0μM, 115.0–515.0μM and 5.0–185.0μM, 265.0–1265.0μM respectively with detection limit (S/N=3) of 0.33μM and 0.47μM. Three linear calibrations for UA were obtained over ranges of 7.0–57.0μM, 87.0–582.0μM and 752.0–2402.0μM with detection limit (S/N=3) of 0.40μM. In addition, satisfactory results were obtained using the modified electrode to detect DA, UA and Trp in samples via standard addition method.

Wiring of glucose oxidase with graphene nanoribbons: an electrochemical third generation glucose biosensor

A reagentless third generation electrochemical glucose biosensor was fabricated based on wiring the template enzyme glucose oxidase (GOx) with graphene nanoribbons (GN) in order to create direct electron transfer between the co-factor (flavin adenine dinucleotide, FAD) and the electrode. The strategy involved: (i) isolation of the apo-enzyme by separating it from its co-enzyme; (ii) preparation of graphene nanoribbons (GN) by oxidative unzipping of multi-walled carbon nanotubes; (iii) adsorptive immobilization of GNs on the surface of a screen printed carbon electrode (SPCE); (iv) covalent attachment of FAD to the nanoribbons; (v) recombination of the apo-enzyme with the covalently bound FAD to the holoenzyme; and (vi) stabilization of the bio-layer with a thin membrane of Nafion. The biosensor (referred to as GN/FAD/apo-GOx/Nafion/SPCE) is operated at a potential of +0.475 V vs Ag/AgCl/{3 M KCl} in flow-injection mode with an oxygen-free phosphate buffer (pH 7.5) acting as a carrier. The signals are linearly proportional to the concentration of glucose in the range from 50 to 2000 mg⋅L−1 with a detection limit of 20 mg⋅L−1. The repeatability (10 measurements, at 1000 mg⋅L−1 glucose) is ±1.4% and the reproducibility (5 sensors, 1000 mg⋅L−1 glucose) is ±1.8%. The biosensor was applied to the determination of glucose in human serum.

Unzipping of multi-wall carbon nanotubes with different diameter distributions: Effect on few-layer graphene oxide obtention

Few-layer graphene oxide (FLGO) was obtained by chemical unzipping of multi-wall carbon nanotubes (MWCNT) of different diameter distributions. MWCNT were synthesized by catalytic decomposition of methane using Fe‐Mo/MgO catalysts. The variation in the Fe/Mo ratio (1, 2 and 5) was very influential in MWCNT diameter distribution and type of MWCNT obtained, including textural, chemical, structural and morphological characteristics. MWCNT diameter distribution and surface defects content had a profound impact on the characteristics of the resulting FLGO. Thus, MWCNT obtained with the catalyst with a Fe/Mo: 5 and presenting a narrow diameter distribution centered at 8.6±3.3nm led to FLGO maintaining non-oxidized graphite stacking (according to XRD analysis), lower specific surface area and higher thermostability as compared to FLGO obtained from MWCNT showing wider diameter distributions. The presence of more oxygen-containing functionalities and structural defects in large diameter nanotubes promotes the intercalation of species towards the inner layers of the nanotube, resulting in an enhanced MWCNT oxidation and opening into FLGO, what improves both micro- and mesoporosity.

High density oxidative plasma unzipping of multiwall carbon nanotubes

Oxidative plasma-assisted unzipping of multiwall carbon nanotubes (MWCNTs) to transform them into petal like nano ribbons, releasing excessive strain with various plasma exposure times.