Presence Of CNTs Research Articles

The Impact of Shear and Elongational Forces on Structural Formation of Polyacrylonitrile/Carbon Nanotubes Composite Fibers during Wet Spinning Process.

Wet spinning of polyacrylonitrile/carbon nanotubes (PAN/CNT) composite fibers was studied and the effect of spinning conditions on structure and properties of as-spun fibers influenced by the presence of CNTs investigated. Unlike PAN fibers, shear force had a larger effect on crystalline structure and physical and mechanical properties of PAN/CNT composite fibers compared to the elongational force inside a coagulation bath. Under shear force CNTs induced nucleation of new crystals, whereas under elongational force nucleation of new crystals were hindered but the already formed crystals grew bigger. To our knowledge, this key effect has not been reported elsewhere. At different shear rates, strength, Young’s modulus and strain at break of PAN/CNT as-spun fibers were improved up to 20% compared to PAN fibers. Application of jet stretch had less influence on physical and mechanical properties of PAN/CNT fibers compared to PAN fibers. However, the improvement of interphase between polymer chains and CNTs as a result of chain orientation may have contributed to enhancement of Young’s modulus of jet stretched composite fibers.

Ultra-light, high flexible and efficient CNTs/Ti3C2-sodium alginate foam for electromagnetic absorption application

Ultra-light carboxylic functionalized multi-walled carbon nanotubes (CNTs-COOH) and Ti3C2 MXene hybrids modified sodium alginate (CNTs/Ti3C2-SA) based composite foams were prepared through ice-templated freeze-drying method. The microstructure of the synthesized CNTs/Ti3C2 hybrids and CNTs/Ti3C2-SA foams is characterized by the presence of CNTs inserted between MXene layers which prevents their restacking. The resultant CNTs/Ti3C2 hybrids exhibit a unique sandwich-like hierarchical structure. Scanning electron microscopy (SEM) images show that the CNTs/Ti3C2-SA foam exhibits a heterogeneous anisotropic microstructure and CNTs/Ti3C2 hybrids are homogeneously dispersed in the skeleton of the porous foam. In case that the content of the hybrids amounts 40 mg/cm3, the CNTs/Ti3C2-SA foam possesses excellent electromagnetic (EM) absorption performance with a minimum reflection coefficient (RCmin) as low as -40.0 dB. In case of a sample thickness of 3.95 mm, the RCmin reaches -24.4 dB and the effective absorption bandwidth covers the whole X band from 8.2 to 12.4 GHz. A control test shows that, with the same absorbent content, the CNTs/Ti3C2-SA foam exhibits a far better EM performance than that of CNT-free Ti3C2-SA foam.

Electrically Conducting Nanocomposites of Carbon Nanotubes and Metal‐Organic Frameworks with Strong Interactions between the two Components

AbstractHighly integrated nanocomposites of Zr‐based metal‐organic frameworks (MOFs) of the UiO‐66 class and multi‐wall carbon nanotubes (MWCNTs) are prepared by direct crystallization of MOFs in the presence of CNTs. Powder samples with homogeneously distributed and strongly intergrown nanotubes and nanoparticles are obtained. Growth of the MOFs in the presence of CNTs deposited on glass slides yields open or compact coatings of the nanocomposites. The materials combine the high porosity and versatility of MOFs with the high electrical conductivities of CNTs. Upon increasing the amount of CNTs in the synthesis, the electrical conductivity shows a clear percolation behavior. Even with small amounts of CNTs, high conductivities are observed. SEM and TEM pictures show the strong intergrowth between the CNTs and the MOF nanoparticles. Crystallization times are shorter in the presence of CNTs, and CNTs run centrally through the MOF crystals. These facts indicate that the CNTs serve as heterogeneous nucleation centers for the formation of MOF nanocrystals. Sensing experiments performed on the coatings show significant changes in the electrical conductivities of the nanocomposite materials in the presence of different analytes, which are also discernable from the changes observed on bare CNTs. This is further proof for the close interaction between the components of the nanocomposites.

Structural properties and mechanical behavior of SWCNTs and MWCNTs reinforced Al2O3 fabricated by spark plasma sintering

Abstract Carbon nanotubes due to their structural and mechanical properties are good candidates as the second phase to improve the mechanical properties of alumina-based ceramics. In the present study, the effects of single wall and multi-wall carbon nanotubes on structural and mechanical properties of alumina were investigated. SWCNTs and MWCNTs were dispersed in alumina powder via a conventional method using 1 wt % PVA water solution as media. Sintering process for two different composite powders, alumina-2 wt. % SWCNTs and alumina 2 wt % MWCNTs was performed by spark plasma sintering technique at 1500 °C and 20 MPa for 10 min. Results showed that the presence of CNTs in alumina caused a considerable amount of porosity in final bodies. SEM images of fracture surfaces revealed the agglomeration of SWCNTs which played a dominant role in the deterioration of mechanical properties. MWCNTs reinforced alumina obtained higher Vickers hardness and bending strength values (12.91 GPa and 291 MPa, respectively) compared to that of SWCNTs (9.18 GPa and 276 MPa, respectively), due to sever agglomerate of SWCNTs throughout sintered composites. Typical load-displacement (P/h) curves were obtained from bending strength test and discussed. It was concluded that the addition of MWCNTs to alumina represented better densification and mechanical properties compared to SWCNTs.

Enhancing the water desalination and electricity generation of a microbial desalination cell with a three-dimensional macroporous carbon nanotube-chitosan sponge anode

Microbial desalination cells (MDCs) are promising bioelectrochemical systems that are being investigated for simultaneous seawater desalination, electricity generation, and wastewater treatment. Anode materials play an important role in determining the performance of MDCs. In this study, a three-dimensional (3D) macroporous sponge was coated with compatible and conductive carbon nanotube-chitosan (CNT-CS) as a composite electrode for MDCs. Experimental results showed that the flexible CNT-CS sponge exhibited a high capacitance (159.4F/g at 20mVs−1), good cycling stability (96% specific capacitance retention after 1000 cyclic voltammetry cycles) and low resistance. Moreover, the MDC with a CNT-CS sponge anode generated a high power density of 1776.6mW/m2 (per electrode area) and desalination rate of 16.5mgh−1, which are significantly higher than those of commercial carbon felt electrodes under the same conditions. The improved MDC performance can be attributed to the continuous 3D macroporous structure of the sponge anode promoting the bacterial loading capacity on the electrode surface. Moreover, the presence of CNTs also further enhances extracellular electron transfer. Our results demonstrate that an MDC operating with a 3D CNT-CS sponge anode offers an effective means for manufacturing high-performance MDCs with wide applicability to bioelectrochemical systems.

Fabrication of pristine-multiwalled carbon nanotubes/cellulose acetate composites for removal of methylene blue

Here, we report the effect of mixing different amounts of pristine-multiwalled carbon nanotubes (p-MWCNTs) with the cellulose acetate (CA) on dye removal. The p-MWCNTs loadings of the composites were varied from 0 to 1.0 wt%, and the non-solvent-induced phase separation methodology was used to fabricate the composite membranes, which were extensively characterized. The rheological tests confirmed that with 1.0 wt% of p-MWCNTs there was a classical filler effect in the viscoelastic behavior of the composite solution, but with no percolation of CNTs. The ATR-FTIR spectra identified specific interactions between CNTs and acetate groups of CA. SEM images showed a top dense layer sustained by a porous support layer consisting of a sponge-like structure in the middle layer. Aggregates of CNTs were seen at higher loadings of CNTs (> 0.1 wt%). The XRD diffractograms of composite membranes showed peak shifts compared to CA membranes due to the presence of CNTs into the CA structure, and their thermal stability was effective up to 320 °C. From the water permeability experiments, the calculated values of the membrane hydraulic resistance (Rm) of the composites were higher since a dense top layer and reduced pore size were achieved. Among all the composite membranes, M7 and M8 had the most desirable antifouling properties due to the high surface hydrophilicity imparted by the CNTs, and also showed an improvement in the removal of methylene blue (MB).

A facile and convenient approach to fill carbon nanotubes with various nanoparticles

A facile and convenient approach was proposed to highly fill carbon nanotubes with various nanoparticles, such as Fe3O4 and CoO. Furthermore, in the case of Fe3O4 and CoO nanoparticles, the effect of reaction conditions on the filling quality and confinement of CNTs on the size and morphology of NPs were explored. The encapsulation procedure in our work can provide a valuable guidance for filling a variety of NPs into hollow structure apart from CNTs. In addition, as a proof-of-concept demonstration, the magnetic properties of Fe3O4 in the absence and presence of CNTs were measured to indicate that magnetization and the blocking temperature of superparamagnetic Fe3O4 can be adjusted, which is due to the confinement effect of CNTs.

Toughening effect of nanocomposite-wall microcapsules on the fracture behavior of epoxy

In this research the reinforcing effect of nanocomposite-wall microcapsules on the fracture toughness and fracture energy of epoxy under mode I was studied. The fracture specimens with the geometry of localized tapered double cantilever beam (TDCB) were used to take the advantage of crack length independent-measurement in determining the fracture properties. The crack length investigations were performed experimentally and numerically to extract the calibration parameters and also evaluate the optimal crack length of TDCB specimens. Three types of microcapsules including hollow microcapsule (CH), ethyl phenylacetate core microcapsule (CEPA) and NH2-CNT reinforced-wall microcapsule (CCNT) were synthesized and used as reinforcements. The scanning electron microscopy study of synthesized microcapsules proved the successful presence of CNTs in the shell and on the wall of CCNT microcapsules. The hollow capsule-loaded epoxy composite exhibited enhanced fracture properties as compared to the neat epoxy. Moreover, the SEM study of fracture surface of CH reinforced specimen revealed a characteristic crack tail toughening mechanism. The CEPA microcapsule decreased fracture properties of neat epoxy. The maximum improvement of fracture properties belonged to the specimen containing the CCNT microcapsules. It was observed that the composite-wall microcapsule was able to increase the fracture toughness and fracture energy of neat epoxy by 59% and 165%, respectively, due to the developments of considerable out-of-plane fracture and large plastic deformation.

Synergistic effect and degradation mechanism on Fe-Ni/CNTs for removal of 2,4-dichlorophenol in aqueous solution.

Fe-Ni bimetallic nanoparticles supported on CNTs (Fe-Ni/CNTs) were synthesized, characterized, and applied for removal of 2,4-dichlorophenol (2,4-DCP) in aqueous solution. The removal performance was enhanced drastically on Fe-Ni/CNTs with respect to monometallic Fe/CNTs. The synergistic effect between Fe-Ni nanoparticles and CNTs has been studied in detail. The research results indicated that the doping of Ni played an important role in promoting the catalytic degradation of 2,4-DCP. And the presence of CNTs not only could effectively reduce the aggregation of nanoparticles but also facilitate the mass transfer of 2,4-DCP and the formation of active atomic hydrogen during the catalytic process. In addition, the removal kinetics of 2,4-DCP by Fe-Ni/CNTs were in agreement with a pseudo-first-order model, and the rate constants were dependent on a number of factors including the initial concentration of 2,4-DCP, the dosage of Fe-Ni/CNTs, pH value of the solution, and doping amount of Ni. The degradation mechanism involved the adsorption by CNTs and catalytic reduction by Fe under the stimulating of Ni, and the preferred dechlorination followed the order of para-Cl > ortho-Cl. The study confirmed that Fe-Ni/CNTs had a potential to be a promising catalytic material for removal of chlorophenol and had a great prospect for practical application.

Fluorescent Gadolinium(III)‐Oligopeptide Complexes and Carbon Nanotube Composite as Dual Modality Anticancer Agents

AbstractIn search of non‐platinum based anticancer drugs, we have synthesized and characterized a new class of three gadolinium(III)‐oligopeptides [Gd(L1)2(NO3)2][NO3] (1, L1=l‐aspartyl(OMe)‐N‐boc‐l‐aspartyl‐l‐aspartyl (OMe)), [Gd(L2)2(NO3)2][NO3] (2, L2=N‐fmoc‐l‐arginyl‐(Pbf)‐glycyl‐l‐aspartyl(OMe)), [Gd(L3)(NO3)3] (3, L3=N‐fmoc‐l‐arginyl‐(Pbf)‐l‐arginyl(OMe) and a carbon nanotube composite, 1@CNT 4. The three oligopeptides, L1 – L3 were prepared in a novel synthetic route using tetramethyl benzotriazolyl uronium hexaflurophosphate (HBTU) as a peptide coupling reagent. Confocal microscopic analysis of the gadolinium(III)‐oligopeptides, 1, 2 and CNT composite, 1@CNT 4 indicate that they display white and green light emissions upon excitations at λ, 405 and 488 nm with characteristic patterns. The oligopeptides, L1 & L3 display in vitro anticancer activity on HeLa cells with IC50 values in one mM concentration whereas the IC50 of RGD‐based oligopeptide was found to be 1 μM. The IC50 of gadolinium(III)‐oligopeptide, 1 and the CNT composite, 4 were found to be 1 μM and 10 nM. The transmission electron microscopic investigation of the HeLa cells treated with the composite 4 confirm the cellular uptake and indicate the presence of CNTs in the cytoplasm and that CNTs appear like bullets carrying the gadolinium(III)‐triaspartate, 1.

Fabrication, Characterisation and Multiscale Modelling of an Epoxy Composite of Amine-Functionalized Carbon Nanotubes Included Three Stages of Carbon Fibre

The goal of this research is to analyse the effect that functionalization has on the material characteristics of multiscale carbon epoxy composites, in addition to determining how efficiently carbon nanotubes are distributed throughout the material (CNTs). As part of this experiment, carbon nanotubes, sometimes referred to as CNTs, were incorporated into an epoxy matrix. After that, carbon fibres were woven into the matrix in order to give it more strength. The resulting combination was used to construct unidirectional carbon fibre laminates. This procedure included infusing an epoxy matrix with a certain number of carbon nanotubes that had been amine-functionalized in the ideal manner. The inclusion of CNTs in the resin at a weight percentage of 1.1 had the impact of creating a significant rise in the Young's modulus. This was the result of the presence of CNTs. The flexural modulus showed observable signs of improvement as a direct result of this action. This event took place as a direct consequence of the presence of CNTs inside the system. However, the overall characteristics of the three-phase composites deteriorated when the epoxy resin was loaded with CNTs at a concentration of 1.6 weight percent. In order to do an examination of the mechanical characteristics of multiscale composites. The two different strategies were combined in order to get this result. The results of this investigation shed light on the disparities that exist between the values that were predicted and the values that were actually found in the data. It is hoped that the multiscale composites in question will be used in the aerospace and missile industries in order to investigate the possibility of structural applications.

Preparation of polypyrrole-decorated MnO2/reduced graphene oxide in the presence of multi-walled carbon nanotubes composite for high performance asymmetric supercapacitors

The present work demonstrates the preparation of polypyrrole-decorated MnO2/rGO by oxidative polymerization method as well as in the presence of CNTs composites. The as-prepared nanocomposites are investigated by XRD, ATR-IR, Raman, TGA, and TEM techniques. Results illustrate polypyrrole with spherical nanoparticles covering the surface of MnO2/rGO and CNTs in which CNTs are intercalated between MnO2/rGO layers (Py@MnG2). In the meantime, the electrochemical performances for the obtained samples are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) experiments at 2 M KCl aqueous electrolyte. Owing to the presence of CNTs as well as the synergistic effect between polypyrrole and MnO2/rGO layers, the electrochemical performance of Py@MnG2 shows high specific capacitance of 295.83 F g−1 in a three-electrode system. The asymmetric supercapacitor (ASC) is assembled with Py@MnG2 and microwave exfoliated graphite oxide (MrGO) as positive and negative electrode material respectively. The as-fabricated ASC device exhibits a high energy density of 11.22 Wh Kg−1 and power density of 807.67 W kg−1 at 1 A g−1 in the potential window of 0–1.6 V. Moreover, the ASC device shows good cycling stability (78.42%) after 1000 cycles at 200 mV s−1.

Characterization of hydroxyapatite/carbon nanotubes coatings on Ti6Al4V

AbstractCarbon nanotubes (CNTs) possess excellent mechanical properties for their role playing in reinforcement as imparting strength to hydroxyapatite (HAp) coating. This work reports the electrodeposition of HAp/CNTs coatings on Ti6Al4V substrate at scanning potentials range of 0÷‐2.0 V/SCE, 5 mV/s, 5 scans at 45°C with the different functionalized CNTs concentration. The characterizations of the coatings were investigated. The amount of functionalized CNTs was determined using thermal gravimetric analysis. The X‐ray diffraction results showed that HAp/CNTs nanocomposite coatings were composed of HAp and CNTs. The diffraction peak with the highest intensity found at 2θ about 32o corresponding to the (2 1 1) HAp crystal and the peak at 26.3o can be assigned to (0 0 2) plane of CNTs. The HRTEM image confirmed the presence of CNTs in the coatings and CNTs amount of 7.25 % by TGA result.

Manipulation of thermo-mechanical, morphological and electrical properties of PP/PET polymer blend using MWCNT as nano compatibilizer: A comprehensive study of hybrid nanocomposites

In this paper, the electrical resistivity, morphology and dynamic mechanical properties of in-situ reinforced microfibrillar composites (MFNC-C) based on polypropylene reinforced with polyethylene terephthalate (PET)-multiwalled carbon nanotubes (MWCNT) fibres have been investigated. Influence of various factors such as the effect of the morphology, CNT composition and the nano compatibilizer effect of CNT on the in-situ reinforced microfibrillar nanocomposites, have been analysed. The dynamic mechanical analysis (DMA) showed that the storage modulus microfibrillar composites are precisely related to the fibrils morphology and composition of CNT. It is found that the presence of CNTs on the fibrils surface has improved the storage modulus as well as normalized storage modulus. The results of four probe analysis showed that by increasing CNTs content, the resistivity remarkably decreased with respect to the morphology of the of nanocomposites. Also, scanning electron microscopy images likewise revealed that the preferential localization of MWCNT on to the PET microfibrils enhanced the compatibility between PET fibrils and PP matrix. Hence, The in –situ formation of fibrillar morphology along with MWCNTs is highly useful in terms of mechanical and electrical performance of the resultant nanocomposites. We assume that the optimized results of this work may open an alternative path for the production of commercially important polymer nanocomposite based on the incompatible immiscible blends.

Investigation of wear behavior of as-plated and plasma-nitrided Ni-B-CNT electroless having different CNTs concentration

In the present study, the wear behavior of as-plated and plasma-nitrided Ni-B-CNT coatings was taken into investigation. Ni-B-CNT composite was deposited on AISI 4140 steel using different concentration of CNTs ranging from 0.2 to 1 g·L−1, in an electroless bath. After the plating process, all samples were plasma nitrided in an atmosphere comprising of 25%N2-75% H2, at 400 °C, for 4 h. The friction and wear behavior of the composite coatings were evaluated using a pin on disk method at an applied load of 10 N. The samples were then characterized by means of XRD, FESEM, microhardness and surface roughness measurements. Worn surfaces were further analyzed by FESEM and EDS spectroscopy. Microhardness results revealed that the maximum hardness of 1550HV was obtained for Ni-B 0.6 g·L−1 CNT plasma-nitrided sample. According to the results, increasing the CNTs concentration caused the as-plated Ni-B amorphous structure to change to semi-crystalline. Furthermore, the crevices formed during the hydrogen evolution reaction were observed to be filled up. Presence of CNTs not only decreased the grain size in the plasma-nitrided samples but also prevented excessive heat generation during the wear test, and thus the friction coefficient was declined during the test. Moreover, image of the worn surface of Ni-B 0.6 g·L−1 CNT plasma-nitrided sample indicated the smoothest wear trace with no apparent cracks and the highest wear resistance among all the samples was achieved. While, in Ni-B-1 g·L−1 CNT sample, agglomeration created asperities as well as large particles weakly bonded to the Ni matrix which ultimately led to an increase in the specific wear rate.

Removal of Cd2+ from Aqueous Solution by Nickel Oxide/CNT Nanocomposites

The present work investigates the efficiency of the nickel oxide/carbon nanotube (NiO/CNT) nanocomposite for the removal of Cd2+ metal ions from an aqueous. The NiO/CNT nanocomposite was synthesized by the direct co-precipitation method in an aqueous media in the presence of CNTs. The resulting materials were characterized by FT-IR, XRD, SEM, N2 adsorption-desorption analysis. In order to optimize the adsorption of Cd2+ ions on NiO/CNT nanocomposite, the effects of the different parameters—namely pH, contact time, initial concentration of Cd2+, and adsorbent dosage—were also studied. Experimental data revealed that the Cd2+ ions adsorption of the NiO/CNT nanocomposite was through Langmuir and Temkin isotherm models rather than the Freundlich model. The kinetic data of adsorption of Cd2+ ions on the adsorbent was best described by a pseudo-second-order equation, indicating their chemical adsorption. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° were calculated. The obtained values showed that the adsorption was spontaneous and exothermic in nature. The reusability test showed that the Cd2+ could be easily removed from the surface site of NiO/CNT nanocomposite by a 0.1 M nitric acid solution as the adsorption capacity was maintained after 5 cycles of the adsorption/desorption process. This suggests that NiO/CNT nanocomposite can be reused through many cycles of water treatment and regeneration.

Novel Approach for Fabricating Transparent and Conducting SWCNTs/ITO Thin Films for Optoelectronic Applications

Single-walled carbon nanotubes (SWCNTs) incorporated in indium tin oxide (ITO) were developed to fabricate transparent conductive thin films via a sol–gel spin coating technique. The fabricated thin films were annealed at 350 °C. The effects of incorporating SWCNTs and varying film thickness on crystal structure were systematically investigated by X-ray diffraction (XRD), Raman shift, surface elemental compositions, surface topography and roughness, optoelectronic characteristics, and mechanical properties. XRD results confirmed the body-centered cubic structure of indium oxide polycrystalline phase, indicating that the structural properties of the ITO films were not significantly altered by incorporating CNTs. The presence of CNTs in the ITO matrix was confirmed by analyses of Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray spectroscopy (EDX). FESEM images revealed the formation of SWCNTs/ITO nanoparticles, and the average crystallite size increased along with incr...

Carbon nanotubes toughened immiscible polymer blends

Abstract The incorporation of CNTs into the immiscible blends are increasingly attractive because of high performance, its wide application and great prospects for development in the future. The objective of this review focuses on CNTs toughened immiscible polymer blends based on the selective localization of CNTs in the immiscible blends. Firstly, the thermodynamic and kinetic factors that determines the localization of CNTs are introduced. The former is relative to the wetting coefficient that can be applied to evaluate the favorable polymer component for CNTs; and the latter relates to the migration of CNTs in polymer blends. Combined with the morphology evolution accompanying with the incorporation of CNTs, the selective localization of CNTs can be distributed in dispersed phase, continuous phase or at the interface, exhibiting different unique properties. Among these properties, CNTs toughened the immiscible polymer blends can be found in these two cases: CNTs disperse in one phase (droplets or continuous) or CNTs disperse at the interface. With the presence of CNTs in immiscible blend, the toughening mechanisms involve: 1) the formation of percolative CNTs network; 2) formation of “cross-linked”-like structure; 3) morphology evolution; 4) compatibilization of immiscible blends; 5) nanobridge effect of CNTs at the interface. This review details recent works for the above mentioned selective localization of CNTs in immiscible blend and corresponding the toughening mechanisms of CNTs for immiscible blends, which is proposed to provide a guidance for the polymer toughening.

Peptide and peptide-carbon nanotube hydrogels as scaffolds for tissue & 3D tumor engineering

The use of hybrid self-assembling peptide (EFK8)-carbon nanotube (SWNT) hydrogels for tissue engineering and in vitro 3D cancer spheroid formation is reported. These hybrid hydrogels are shown to enhance the attachment, spreading, proliferation and movement of NIH-3T3 cells relative to that observed using EFK8-only hydrogels. After five days, ∼30% more cells are counted when the hydrogel contains SWNTs. Also, 3D encapsulation of these cells when injected in hydrogels does not adversely affect their behavior. Compressive modulus measurements and microscopic examination suggest that SWNTs have this beneficial effect by providing sites for cell anchorage, spreading and movement rather than by increasing hydrogel stiffness. This shows that the cells have a particular interaction with SWNTs not shared with EFK8 nanofibers despite a similar morphology. The effect of EFK8 and EFK8-SWNT hydrogels on A549 lung cancer cell behavior is also investigated. Increasing stiffness of EFK8-only hydrogels from about 44 Pa to 104 Pa promotes a change in A549 morphology from spheroidal to a stretched one similar to migratory phenotype. EFK8-SWNT hydrogels also promote a stretched morphology, but at lower stiffness. These results are discussed in terms of the roles of both microenvironment stiffness and cell-scaffold adhesion in cancer cell invasion. Overall, this study demonstrates that applications of peptide hydrogels in vitro can be expanded by incorporating SWNTs into their structure which further provides insight into cell-biomaterial interactions. Statement of significanceFor the first time we used hybrid self-assembling peptide-carbon nanotube hybrid hydrogels (that we have recently introduced briefly in the “Carbon” journal in 2014) for tissue engineering and 3D tumor engineering.We showed the potential of these hybrid hydrogels to enhance the efficiency of the peptide hydrogels for tissue engineering application in terms of cell behavior (cell attachment, spreading and migration). This opens up new rooms for the peptide hydrogels and can expand their applications.Also our system (peptide and peptide-CNT hydrogels) was used for cancer cell spheroid formation showing the effect of both tumor microenvironment stiffness and cell-scaffold adhesion on cancer cell invasion. This was only possible based on the presence of CNTs in the hydrogel while the stiffness kept constant.Finally it should be noted that these hybrid hydrogels expand applications of peptide hydrogels through enhancing their capabilities and/or adding new properties to them.

Amine-functionalization of carbon nanotubes assisted by electrochemical generation of chlorine

Electrochemical functionalization methods suffer from long processing time and lower efficiency. In this work, a simple single-step functionalization process with relatively higher efficiency and lower processing time is introduced. Different analyses were used to study it including Ultraviolet–visible absorption spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Raman spectroscopy, energy dissipative spectroscopy (EDS) and transmission electron microscopy (TEM). The presence of chlorine produced by the electrochemical reactions on the surface of the CNTs was confirmed by EDS. In addition, UV–vis absorption of the chlorine decreases in the presence of CNTs probably because of chemisorption with CNTs, followed by the substitution of chlorine by ethylenediamine on the CNTs surface. Furthermore, the existence and amount of amine groups on the CNTs’ surface were confirmed and measured by FTIR and TGA, respectively. UV–vis and TGA analysis of the prepared samples showed that the amination efficiency and the dispersibility of CNTs were higher in this method. Moreover, TEM images revealed higher surface roughness comparing with pristine CNT. Such higher roughness could imply the partial damage of graphite structure due to functionalization.