Amine-functionalized Carbon Nanotubes Research Articles

Characterization of Mixed Amine Functionalized Carbon Nanotube from Nigerian Sub Bituminous Coal

Characterization of Mixed Amine Functionalized Carbon Nanotube from Nigerian Sub Bituminous Coal

A molecular dynamics assisted insight on the enhancement of interfacial adhesion of carbon fiber with polypropylene matrix via a combination of surface functionalization and defect laden carbon nanotube coating

The low compatibility of traditional carbon fibers with thermoplastics results in an inferior interfacial interaction. Therefore, it prohibits full exploitation of low-cost thermoplastics like polypropylene in developing high-strength carbon fiber reinforced composites. In the present study, atomistic and mesoscopic molecular dynamics simulations are carried out to postulate enhancement in interfacial shear strength among amine terminated carbon fiber and polypropylene. Pristine and amine functionalized carbon nanotubes are coated to the amine terminated carbon fiber separately. The influence of Stone-Wales and Di-vacancy defects of carbon nanotubes, with their varying defect concentration, is investigated. Besides, maleic anhydride-grafted-styrene ethylene butylene styrene is used as a compatibilizer. Interaction energy among maleic anhydride-grafted-styrene ethylene butylene styrene and amine terminated carbon nanotubes increases with amine weight percentage over carbon nanotube. The highest optimal interaction energy is shown by carbon nanotube functionalized with 6 wt percent amine groups and having 3 Stone-Wales defects, which is ∼41% higher than that with pristine carbon nanotubes. The pull-out coarse-grain simulations of the amine terminated carbon fiber coated with such optimal carbon nanotubes displayed the highest interfacial shear strength of 31.11 MPa, and it was ∼106% higher than the composite reinforced with neat carbon fiber.

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.

Theoretical and experimental study on the fluidity performance of hard-to-fluidize carbon nanotubes-based CO2 capture sorbents

Carbon nanotubes-based materials have been identified as promising sorbents for efficient CO2 capture in fluidized beds, suffering from insufficient contact with CO2 for the high-level CO2 capture capacity. This study focuses on promoting the fluidizability of hard-to-fluidize pure and synthesized silica-coated amine-functionalized carbon nanotubes. The novel synthesized sorbent presents a superior sorption capacity of about 25 times higher than pure carbon nanotubes during 5 consecutive adsorption/regeneration cycles. The low-cost fluidizable-SiO2 nanoparticles are used as assistant material to improve the fluidity of carbon nanotubes-based sorbents. Results reveal that a minimum amount of 7.5 and 5 wt% SiO2 nanoparticles are required to achieve an agglomerate particulate fluidization behavior for pure and synthesized carbon nanotubes, respectively. Pure carbon nanotubes + 7.5 wt% SiO2 and synthesized carbon nanotubes + 5 wt% SiO2 indicates an agglomerate particulate fluidization characteristic, including the high-level bed expansion ratio, low minimum fluidization velocity (1.5 and 1.6 cms−1), high Richardson—Zaki n index (5.2 and 5.3 > 5), and low Π value (83.2 and 84.8 < 100, respectively). Chemical modification of carbon nanotubes causes not only enhanced CO2 uptake capacity but also decreases the required amount of silica additive to reach a homogeneous fluidization behavior for synthesized carbon nanotubes sorbent.

Development and characterization of surface functionalized hierarchical carbon fiber reinforced hybrid polypropylene composites

Light-weight hybrid composites of relevant industrial applications were prepared using surface functionalized hierarchical carbon fibers ( f-CF), silane treated hollow glass microspheres (HGM), and a blend of polypropylene (PP) and maleic anhydride-grafted-styrene ethylene butylene styrene as the base polymer matrix. The f-CF were prepared by coating amine functionalized carbon nanotubes onto silane treated CF using an ultrasonic assisted electrophoretic deposition technique to improve fiber-matrix interfacial adhesion. For hybrid composition of 20 wt.% f-CF and 10 wt.% HGM, the tensile strength and modulus improved by ∼141 and ∼536% over neat PP while flexural strength and modulus increased by ∼118% and ∼583% respectively. Impact strength of 11.06 kJ/m2 was obtained and uniform dispersion and distribution of f-CF and HGMs was observed in Scanning electron microscope (SEM) images. Desirable reduction in density and melt viscosity along with improvement in composite stiffness were observed due to addition of HGM filler. Compared to PP, the crystallization temperature increased by ∼12°C while a maximum decrease of ∼5°C in melting temperature was obtained for the hybrid composites. Crystallinity of the hybrid composites decreased with an evident β crystal formation brought in by the nucleation.

High-efficient oil/water separation membrane based on MXene nanosheets by co-incorporation of APTES and amine functionalized carbon nanotubes

Membrane based separation technology has great prospects in the treatment of oily wastewater, which involves serious environmental and health concern. In the present investigation, 3-aminopropyltriethoxysilane (APTES) was used to modify MXene nanosheets and amine functionalized carbon nanotubes (ACNTs) was used to control the layer spacing of MXene followed by the fabrication of a series of APTES/MXene-ACNTs composite membranes supported on cellulose acetate (CA) by vacuum filtration. The surface morphology analysis by scanning electron microscope (SEM) and atomic force microscopy (AFM) revealed that, the composite membranes exhibited excellent hydrophilicity as well as high efficiency in oil/water emulsion separation. The rejection ratios of composite membranes for lubricating oil emulsion and vegetable oil emulsion were found to be more than 99%. Compared to the pure MXene membrane M1 (500.7 L·m−2·h−1·bar−1), the pure water flux of the best modified membrane APTES/MXene-ACNTs/CA (M4) reaches up to 2892.8 L·m−2·h−1·bar−1. Moreover, the modified membrane shows good anti-fouling and anti-swelling characteristics even after several cyclic consecutive cycles. This work demonstrates a new horizon in the applications of two-dimensional membrane materials.

Recyclable amine-functionalized carbon nanotubes for the separation of oily wastewater

In this work, a CNTs-NH2 demulsifier was prepared by grafting ethylenediamine on the surface of carbon nanotubes to break oily wastewater. The physicochemical and interfacial properties of CNTs-NH2 were characterized and analyzed. It showed that CNTs-NH2 had an eminent amphipathicity and high interfacial activity, which allows it to sharply migrates to the interface and effectively interacts with interfacial film by the combined action of π-π interaction and electrostatic attraction. The demulsification tests exhibited that CNTs-NH2 could effectively remove emulsified oil from the oily wastewater. It could be used at acidic and neutral conditions, and high salinity. Moreover, it could be recycled and still maintained its interfacial activity, thusly vastly enhancing the application scope. The light transmittance was up to 88.1% and the corresponding oil removal rate was 99.2% with 100 mg/L of CNTs-NH2 for 30 min. The oil removal rate of CNTs-NH2 remained above 97.8% after 6 cycles. This work provides a deep understanding on the design of demulsifier and its demulsification mechanism.

Ultrafine Pd nanoparticles on amine-functionalized carbon nanotubes for hydrogen production from formic acid

Formic acid is a promising hydrogen source and liquid organic hydrogen carrier because of its high hydrogen density. To produce hydrogen from formic acid, catalytic dehydrogenation of formic acid over Pd-based catalysts has been investigated. Here, a highly active catalyst is rationally designed. Carbon nanotubes without micropores were adopted as a support to facilitate the mass transport of reactants or products. Pd particles were made as small as possible to provide a large number of active sites and to alleviate the activation barrier for hydrogen desorption. Amine functional groups were introduced into carbon nanotubes to generate formate anions by capturing protons from formic acid. Based on this design, ultrafine Pd nanoparticles (1.76 nm) on amine-functionalized carbon nanotubes were successfully synthesized. This catalyst demonstrated remarkable activity for the formic acid dehydrogenation reaction, with a high turnover frequency value of 2560 h−1 at 30 °C.

Amine-functionalized carbon nanotubes supported NiAuPd nanoparticles as an efficient in-situ prepared catalyst for formic acid dehydrogenation

Hydrogen (H2) generation from formic acid (FA) decomposition is a promising route in practical application of hydrogen energy. As a promising H2 supplier, besides the advantage of high H2 content and excellent stability, FA can also be used as a mild reducing agent. Herein, an in-situ prepared NiAuPd nanoparticles (NPs) supported on amine-functionalized carbon nanotubes (NiAuPd/NH2-CNTs) with FA as the reducing agent is successfully developed at room temperature. The as-prepared NiAuPd/NH2-CNTs are directly used for the catalytic decomposition of FA, exhibiting excellent activity and 100% H2 selectivity with the initial turnover frequency (TOFinitial) value of 699.1 and 3006.1 mol H2 mol Pd-1 h-1 at 303 and 333 K, respectively. Moreover, the additive sodium formate (SF) can further facilitate the reduction process and enhance the catalytic performance, with the TOFinitial value of 4391.1 mol H2 mol Pd-1 h-1 at 333 K, which are comparable to most of the reported heterogeneous catalysts with the complicated post-treatment. The excellent catalytic performance of NiAuPd/NH2-CNTs is mainly attributed to the high dispersion of NPs and the boost effect of -NH2 group on O–H cleavage. This work provides a feasible strategy to design in-situ prepared catalysts for the efficient high-quality H2 generation from FA for fuel cells application.

Ultrasensitive detection of cytotoxic food preservative tert-butylhydroquinone using 3D cupric oxide nanoflowers embedded functionalized carbon nanotubes

Accurate detection of cytotoxic food preservative tert-butylhydroquinone (TBHQ) has significant importance in maintaining food quality and safety. TBHQ is a chronic hazard to aquatic life and its use in applications involving direct human exposure and frequent release to environment makes its quantification critical to maintain safety. Hence, we report development of a sensitive electrochemical sensor for TBHQ determination at nanomolar level in commonly used edible oils and water sample. Novel cupric oxide (CuO) decorated amine functionalized carbon nanotubes (NH2-CNTs) were prepared for development of TBHQ sensor. 3D CuO nanoflowers and NH2-CNTs were synthesized using hydrothermal and ultrasound-assisted method respectively. Techniques such as SEM, elemental mapping, XRD, FTIR, micro Raman, XPS, EIS, and UV–Visible spectroscopy were taken to affirm significant characterizations of synthesized materials. We have observed outstanding electrocatalytic activity towards TBHQ detection using the sonochemically prepared nanocomposite modified screen printed carbon electrode (SPCE). The proposed sensor exhibited ultra-low detection limit at 3 nM and exceptional sensitivity at 37.7 μA μM−1 cm−2. Furthermore, TBHQ sensor showcased outstanding anti-interference, stability, reproducibility, and repeatability. The practical feasibility of TBHQ detection was validated using real sample analysis resulting in excellent recovery in the range 95.90–104.87% and a maximum RSD of mere 2.71%.

Evaluation of a quaternized polyethersulfone membrane enhanced with amine functionalized carbon nanotubes for forward osmosis application

Multiwall carbon nanotubes (CNTs) were quaternized with trimethylamine to form an anionic conductive CNTS (QCNTs) then blended with quaternized polyethersulfone membrane (QPES) by phase invasion method to obtain a composite membrane with higher permeation, improved rejection and enhanced antifouling properties for forward osmosis application. The membranes and QCNTs were characterized using SEM, TGA, NMR, Raman and FTIR. The fabricated composite membranes showed that addition of QCNTs can improve membrane basic properties when compared to commercial polyethersulfone membranes. This observed improvement could be attributed to the incorporated oxygen and amine functionalities in the CNTs. The 0.1 wt % QCNTs showed a contact angle of 64, reverse solute flux of 7.4 and 6.2 Lm-2h-1 for NaCl and MgSO4 respectively compared to an original pure water flux of 8.058 Lm-2h-1. Humic acid was used as a foulant, when the composited was fouled using humic acid, the 0.1wt.% QCNTs showed a reverse solute flux of 5.7 and 5.0 Lm-2h-1 respectively at room temperature.

Dynamic Characteristics of Functionalized Carbon Nanotube Reinforced Epoxy Composites: An Experimental Approach

The effects of amine functionalization of carbon nanotubes (CNTs) and CNTs weight percent (wt. %), on the first bending natural frequencies and damping properties of CNT/epoxy composites are investigated in this paper. CNTs and amine functionalized CNTs (AFCNTs), with two different weight percentages, are used to manufacture the beam shaped specimens. Epoxy, CNT/epoxy (0.25 and 0.5 wt. % of CNTs) and AFCNT/epoxy (0.25 and 0.5 wt. % of AFCNTs) were fabricated. Experimental vibrational test is utilized in order to study the free vibration behavior of specimens under clamped-free boundary conditions. Natural frequencies and damping ratios are extracted from the experimental time response graphs. Results indicated that adding AFCNTs (0.5 wt. %) into the matrix material has the most effect on the natural frequency of the beam. In this case, the damping ratio has the lowest value. Moreover, scanning electron microscopy (SEM) images of the fracture surface of the specimens are prepared. The images illustrate that amine functionalization of CNTs leads to better dispersion of CNTs into the epoxy matrix. Further, it can be observed that enhancement in the value of damping ratio is more dominant than enhancement in stiffness value by dispersing AFCNTs into the epoxy resin.

Membraneless biofuel cells using new cathodic catalyst including hemin bonded with amine functionalized carbon nanotube and glucose oxidase sandwiched by poly(dimethyl-diallylammonium chloride)

A new cathodic catalyst is developed for improving the performance of membraneless enzymatic biofuel cell (EBC) by enhancing overall oxygen reduction reaction (ORR). In this catalyst, both hemin and glucose oxidase (GOx) are considered as enzymatic catalysts to facilitate H2O2 reduction reaction (HRR) and partial oxygen reduction reaction (PORR), respectively. Hemin is attached to amine group functionalized carbon nanotube (Amine-CNT) to form amide bond, and GOx is conjugated with two poly(dimethyl-diallylammonium chloride) (PDDA) layers to form sandwich-like structure. As a result, [Amine-CNT/Hemin]/PDDA/GOx/PDDA catalyst is completed. This catalyst plays a role in reducing the amount of GOx leached out and preserving the mass transfer of fuels, and finally, increasing the catalytic activity for cathodic reactions. According to electrochemical estimation, its onset potential reaches 0.4V vs. Ag/AgCl and current density significantly increases to 323μAcm−2. When the performance of membraneless EBC adopting this catalyst is measured, maximum power density is 24.1±0.61μWcm−2 and its activity preserves 82.1% after four weeks. This excellent result is because PORR and HRR are promoted by the rigid connection of GOx and hemin, which is mainly induced by the sandwich effect of GOx by PDDA layers.

Mechanically strong and tough polyimide aerogels cross-linked with amine functionalized carbon nanotubes synthesized by fluorine displacement reaction

Polyimide aerogels generally face problems of shrinkage and collapse of pore structure during preparation, resulting in poor macro-structural integrity and mechanical properties. Towards these problems, polyimide composite aerogels with three-dimensional porous network structure, outstanding mechanical and thermal properties have been synthesized by utilizing high grafting ratio of amino-functionalized carbon nanotubes (CNTs) prepared by fluorine displacement reaction in this study. All aerogel samples exhibited the network structure composed of highly interconnected nanofibers. Most importantly, the compression modulus of the PI aerogel reached to 47.3 MPa with the addition of amino-functionalized CNTs, which was 1126% higher than that of the linear PI aerogel. The prepared PI/CNT-NH2 composite aerogels can still maintain the original compressive modulus of 96% under high temperature conditions. These results indicate that the PI composite aerogels could exhibit great potential in aerospace applications as high-performance and lightweight porous materials.

Binding Capacity and Selectivity of Functionalized and Un-functionalized Carbon Nanotubes for Development of Copper-Detecting Printable Sensor.

Carbon nanotubes (CNTs) have unique properties which can be modified through surface functionalization. The ability of several functionalized and un-functionalized CNTs to bind copper was investigated as a first step toward developing a printable CNT-based sensor to detect copper in aqueous systems. Binding capacity and specificity were shown to vary by functionalization and vendor. CNTs from two vendors were tested, and the equilibrium binding data was fitted using two isotherm models. Calculated qmax (mg/g) values indicated one vendor's carboxyl-functionalized CNTs had the greatest binding capacity (94-115mg/g), while other carboxyl-functionalized CNTs and amine-functionalized CNTs had similar capacities to un-functionalized CNTs (15-30mg/g). Hydroxyl-functionalized CNTs had the lowest copper binding capacity (7-8mg/g) of the CNTs tested. Freundlich isotherms showed no obvious trends in binding affinity, but suggested that binding was primarily due to chemisorption. Variations in CNT size, functionalization percentage, and purity could explain, partially, the observed adsorption differences.

Amine functionalized carbon nanotube (ACNT) filled in sulfonated poly(ether ether ketone) membrane: Effects of ACNT in improving polymer electrolyte fuel cell performance under reduced relative humidity

Amine functionalized carbon nanotube (ANCT) is applied as an inorganic potential proton conducting material embedded in a sulfonated poly(ether ether ketone) (SPEEK) matrix. The morphological, structural, thermomechanical, physiochemical and electrochemical properties of SPEEK/ACNT composite were investigated and compared to obtained results from bare SPEEK. The synthesized ACNT-incorporated SPEEK membrane have uniform and dense morphology and exhibit improved properties as proton exchange membrane (PEM); for example, SPEEK/ACNT possessed higher thermal stability and tensile strength than SPEEK alone. The amine functionalized structure of ACNT is assumed to be one of critical factors resulting in higher performance of SPEEK/ACNT membrane, since it can induce acid-base conducting networks between ACNT and SPEEK matrix, which would improve water uptake and proton conductivity while lowering ion exchange capacity of membrane. When used in 20% relative humidity, a polymer electrolyte fuel cell (PEFC) with SPEEK/ACNT membrane is found to exhibit much higher performance than a PEFC with bare SPEEK, suggesting the potential use of SPEEK/ACNT membrane as PEM.

In-situ polymerization and covalent modification on aramid fiber surface via direct fluorination for interfacial enhancement

Poor adhesive performance is considered to be a major disadvantage of aramid fibers in the fabrication of aramid fiber reinforced polymer composites, and it's a main drawback to restrict its wide application. In this paper, fluorine-related free radicals induced by direct fluorination were detected by Electron Paramagnetic Spectrum (EPR), which were considered as active spots to initiate copolymerization between acrylic acid (AA) and divinylbenzene (DVB), and the copolymer was chemically grafted onto AF surface, thus aramid fiber was covalently decorated by plenty of –COOH groups. Furthermore, amine-functionalized carbon nanotubes were devised to undergo the condensation reaction with the –COOH groups on fiber surface so that high density of carbon nanotubes could be chemically grafted on aramid fiber surface. Testing of mechanical properties showed that there was almost no damage to the mechanical property of aramid fibers, and interfacial shear strength of modified fiber increased by 53.1% and 69.1% after grafting polyacrylic acid-divinylbenzene copolymer and carbon nanotubes in sequence, respectively. Mathematical analysis for the changes and relationships between surface energy, surface roughness of fibers and their IFSS revealed that specific surface energy made a greater contribution to the enhancement of IFSS than surface roughness, which proved that surface energy was more helpful to the interfacial properties of the composites. Additionally, electric conductivity of organic aramid fiber improved obviously with a conductivity of 0.48 S/m.

Potential Bifunctional Filler (CeO2–ACNTs) for Nafion Matrix toward Extended Electrochemical Power Density and Durability in Proton-Exchange Membrane Fuel Cells Operating at Reduced Relative Humidity

Cerium oxide–anchored amine-functionalized carbon nanotubes (CeO2–ACNTs) are applied as radical scavengers as well as solid proton conductors to realize hybrids with Nafion (Nafion/CeO2–ACNTs) for ...

A Tough and Efficient Self-Healing Supramolecular Materials modulated with WCNT-NH2

Self-healing polymers crosslinked by solely reversible bonds are intrinsically weaker than common covalently crosslinked networks. In this work, a self-healing materials with excellent mechanical properties was synthesized by a new design strategy, wich is to introduce covalent into reversible networks to improve its mechanical properties. First, polyamidoamine dendrimer oligomers (PAMAM-Oligomers) was synthesized. Then amine functionalized carbon nanotubes (WCNT-NH2) reacted with PAMAM-Oligomers to form a polyamidoamine carbon nanotubes composite materials (PAMAM-WCNT-NH2). The synthesized materials behave as rubber and exhibit spontaneous self-healing behaviour at room temperature without external stimuli. The mechanical and self-healing properties are closely related to the content of WCNT-NH2. For 0.5wt% WCNT-NH2 in the materials, the strain of the material is 330% and tensile strength is 0.6 MPa. Importantly it can improve the self-healing efficiency to 98% of its original tensile strength in 2h.

Amine-functionalized carbon nanotubes as curing agent for polystyrene-modified novolac epoxy resin: synthesis, characterization and possible applications

A novel epoxy resin nanocomposite containing epoxidized novolac (ENR) and epoxidized polystyrene (EPSt) was fabricated through the curing with amine-functionalized multiple-walled carbon nanotubes (MWCNTs–NH2). The chemical structures of the synthesized samples were characterized using Fourier transform infrared and proton nuclear magnetic resonance (1H NMR) spectroscopies. The composition of ENR:EPSt:MWCNTs–NH2 nanocomposite was set as 75:20:5 wt%. The morphology and thermal stability of the fabricated nanocomposite were investigated using scanning electron microscopy (SEM) and thermogravimetric analysis, respectively. The SEM image revealed that the modified MWCNTs are well dispersed in the ENR–EPSt matrix without any agglomeration. The curing temperatures of the ENR, ENR–EPSt, and ENR–EPSt/MWCNTs nanocomposite were investigated using differential scanning calorimetric analysis. According to thermal property studies results, the addition of PSt as well as curing of mixture using amine-functionalized MWCNTs has synergistic effect on the thermal stability of the ENR resin.