Hydroxylated Carbon Nanotubes Research Articles

ZnO/CNT@Fe3O4 induces ROS-mediated apoptosis in chronic myeloid leukemia (CML) cells: an emerging prospective for nanoparticles in leukemia treatment

The advent of nanoparticles revolutionised the drug delivery systems in human diseases; however, their prominent role was highlighted in the cancer-based therapies, where this technology could specifically target cancer cells. Herein, we decided to combine two nanoparticles Fe3O4 and ZnO to fabricate a new anti-cancer nanocomposite. Noteworthy, hydroxylated carbon nanotube (CNT) was used to increase the water-solubility of the compound, improving its uptake by malignant cells. This study was designed to evaluate the anticancer property as well as the molecular mechanisms of ZnO/CNT@Fe3O4 nanocomposite cytotoxicity in CML-derived K562 cells. Our results outlined that ZnO/CNT@Fe3O4 decreased the proliferative capacity of K562 cells through induction of G1 arrest and induced apoptosis probably via ROS-dependent upregulation of FOXO3a and SIRT1. The results of qRT-PCR analysis also demonstrated that while ZnO/CNT@Fe3O4 significantly increased the expression of pro-apoptotic genes in K562 cells, it had no significant inhibitory effect on the expression levels of anti-apoptotic target genes of NF-κB; proposing an attenuating role of NF-κB signalling pathway in K562 cell response to ZnO/CNT@Fe3O4. Synergistic experiment showed that ZnO/CNT@Fe3O4 could enhance the cytotoxic effects of imatinib on K562 cells. Overall, it seems that pharmaceutical application of nanocomposites possesses novel promising potential for leukaemia treatment strategies.

In situ preparation of magnetic nickel-containing functionalized carbon nanotubes to support palladium as a catalyst for the Heck reaction

Magnetic and hydroxylated carbon nanotubes (NiCNTs-OH) were synthesized in situ via a green, facile, and efficient water-assisted chemical vapor deposition (H2O-CVD) method. Pd nanoparticles (NPs) were then anchored to the surfaces of the NiCNTs-OH and the resulting Pd/NiCNTs-OH were studied for their catalytic efficiency in the Heck reaction. Transmission electron microscopy images show that the prepared Pd/NiCNTs-OH consist of a CNT-based framework with Pd NPs of 2–4 nm and Ni NPs encapsulated by the tubes. Vibrating sample magnetometer measurements reveal that the catalysts are easily recycled by magnetic separation. Raman spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations suggest that defects and oxygen-containing groups are introduced by the H2O-CVD method, providing sufficient anchoring sites for Pd NP loading. Hence, the Pd/NiCNTs-OH exhibit excellent yields in the Heck reaction of various aryl iodides with methyl acrylate. This work thus demonstrates a green and facile method for the preparation of magnetic nano-catalysts that can be employed for various catalytic reactions.

Surface Modification of Multi-Walled Carbon Nanotubes Using Acetic Anhydride and its Effects on Poly(butylenesadipate-co-terephthalate) Based Composite

Hydroxyl carbon nanotubes were surface modified by acetic anhydride to reduce its polarity and then melt blended with biodegradable polyester poly(butylenesadipate-co-terephthalate) as a reinforcing filler. After surface modification, nanotubes show higher contact angle and uniformly dispersion in polymer matrix. Dynamic thermomechanical analysis was employed to investigate interfacial adhesion between nanotubes and polymer matrix, which proving that storage modulus of composites increased after adding acetic anhydride. In addition, hardness, Young’s modulus, yielding stress as well as thermal stability of composites are all elevated with the addition of acetic anhydride, which should contribute to their commercial application.

Aspartic acid tagged carbon nanotubols as a tool to deliver docetaxel to breast cancer cells: Reduced hemotoxicity with improved cytotoxicity

The present study aimed to explore the potential of hydroxylated carbon nanotubes (CNTnols) conjugated with aspartic acid for the delivery of docetaxel (DTX) to breast cancer cells. The conjugate was well-characterized by FT-IR, NMR, XRD and FE-SEM. The nanoconjugate offered a hydrodynamic diameter of 86.31 ± 1.02 nm, with a PDI of 0.113 and zeta potential of −41.6 ± 0.17 mV. The designed nanosystem offered a controlled & pH dependent release vouching release of drug in the cancerous cytosol, not in blood, assuring delivery of the pay-load to the site of action. The carriers offered substantial hemocompatibility and lower plasma protein binding, ensuring more drug available at the site of action. The in-vitro cell viability studies in MDA MB-231 cells inferred approx. 2.8 times enhancement in the cytotoxicity potential of the conjugate vis-à-vis plain drug. Pharmacokinetic studies also corroborated the superiority of the designed nanoconjugate in terms of enhanced bioavailable fractions, reduced clearance and longer bioresidence to that of plain docetaxel. The present studies, successfully provide a workable nanomedicine, loaded with a BCS class-IV drug, for improved efficacy and safety in breast cancer.

Carbon nanotubes affect the formation of trihalomethanes during chlorination of bisphenol A

Carbon nanotubes (CNTs) and trace contaminants often co-occur in natural waters and wastewaters, and they may become the precursors of disinfection byproducts (DBPs). However, the effects of CNTs on the formation of DBPs during chlorination of co-existed organic pollutants are unknown. This study compared the effects of three types of CNTs on the formation of DBPs during chlorination of bisphenol A (BPA). The results showed that, compared with the single system of BPA, CNTs significantly decreased the initial rate (Ri) and the second-order rate constant (k) of trihalomethanes (THMs) formation in the binary systems of CNTs and BPA. For example, Ri for the binary system (38.7–49.6 µg/(L·h)) was much lower than that for the single system of BPA (63.1 µg/(L·h)). Furthermore, the suppression effects depended not only on the type but also on the concentration of CNTs: the suppression of Ri and k by CNTs followed the order of pristine CNTs > hydroxyl CNTs > carboxylic CNTs, and increased with rising concentration of CNTs. The adsorption experiments and density functional theory (DFT) calculation further revealed that higher adsorption and stronger binding of BPA to CNTs resulted in greater suppression degree of Ri and k by CNTs.

Corrosion behavior of steel rebar embedded in hybrid CNTs-OH/polyvinyl alcohol modified concrete under accelerated chloride attack

This study evaluated the mono and hybrid effects of hydroxyl carbon nanotubes (CNTs-OH) and polyvinyl alcohol (PVA) on the corrosion behavior of steel rebars embedded in concrete under accelerated chloride attack by an impressed voltage technique. The contents of CNTs-OH and PVA were fixed at 0.5% and 1% by weight of cement, respectively. Mechanical tests showed that hybrid CNTs-OH/PVA improved the flexural strength and compressive strength by 20% and 9%, respectively. The Mercury Intrusion Porosimetry test showed that adding CNTs-OH/PVA reduced the total porosity and macro-pore content of concrete by 29.9% and 83.2% over the control concrete, respectively. The impressed voltage corrosion test indicated that hybrid CNTs-OH/PVA significantly delayed the deterioration progress of the steel rebar in concrete, as the corrosion level of the steel rebar decreased by 94% and the exposure time increased by 60% before the generation of the surface crack compared to those of the control concrete. The mechanisms for the hybrid effects of CNTs-OH and PVA on enhancing the steel corrosion resistance in concrete include: 1) uniform dispersion of CNTs-OH in PVA colloid; 2) pore-filling effect of both CNTs-OH and PVA; and 3) PVA coated CNTs-OH form electric capacitors to restraint the transport of free ions. The findings in this study reveal the potential of hybrid CNTs-OH/PVA modifiers to improve the corrosion resistance of steel rebars in concrete.

Effect of in situ silanization of multiwalled carbon nanotubes on the properties of NBR/MWCNT-OH composites

ABSTRACTThis paper presents the preparation and properties of improved acrylonitrile-butadiene rubber (NBR) composites with hydroxylated carbon nanotubes (MWCNT-OH). A series of in situ modifications were performed using [3-(2-aminoethylamino)propyl]trimethoxysilane (APTS), vinyltrimethoxysilane (VTS) and (3-mercaptopropyl)trimethoxysilane (MPTS). The curing behavior, crosslink density, static and dynamic mechanical properties (DMTA), filler-filler interactions (Payne effect), thermal stability (TGA) and aging stability of the NBR nanocomposites were investigated, in addition to morphological studies (SEM/EDS). The experimental data prove that the most promising silane agent stongly affecting the properties of NBR/MWCNT-OH composite systems was APTS. The NBR vulcanizates showed increased torque, crosslink density, dynamic moduli and tensile strength.

Effect of different carbon fillers on the properties of nitrile rubber composites

ABSTRACTIn this paper, the influence of carbon fillers with different structures such as carbon black (spherical), carbon nanofibers (fibrous), carbon nanotubes (tubular) and hydroxylated carbon nanotubes on the performance of acrylonitrile-butadiene rubber (NBR) composites have been investigated. The studies prove the significant role of the filler’s structure, surface characteristics and filler-filler interactions for composite reinforcement. As part of this study, the cure behaviour, crosslink density, thermal stability, electrical conductivity and mechanical properties of the filled NBR compounds were measured. Furthermore, scanning electron microscopy (SEM) as well as dibutylphthalate absorption (DBPA) measurements were carried out to determine the nature of the tested materials. It has turned out that the greatest reinforcing activity was exhibited by the carbon nanotubes (CNTs). However, all the tested carbon fillers significantly affected the performance of the nitrile rubber composites, which make them attractive additives for elastomer composites.

The Inhibitory Effect of Hydroxylated Carbon Nanotubes on the Aggregation of Human Islet Amyloid Polypeptide Revealed by a Combined Computational and Experimental Study.

Fibrillar deposits formed by the aggregation of the human islet amyloid polypeptide (hIAPP) are the major pathological hallmark of type 2 diabetes mellitus (T2DM). Inhibiting the aggregation of hIAPP is considered the primary therapeutic strategy for the treatment of T2DM. Hydroxylated carbon nanoparticles have received great attention in impeding amyloid protein fibrillation owing to their reduced cytotoxicity compared to the pristine ones. In this study, we investigated the influence of hydroxylated single-walled carbon nanotubes (SWCNT-OHs) on the first step of hIAPP aggregation: dimerization by performing explicit solvent replica exchange molecular dynamics (REMD) simulations. Extensive REMD simulations demonstrate that SWCNT-OHs can dramatically inhibit interpeptide β-sheet formation and completely suppress the previously reported β-hairpin amyloidogenic precursor of hIAPP. On the basis of our simulation results, we proposed that SWCNT-OH can hinder hIAPP fibrillation. This was further confirmed by our systematic turbidity measurements, thioflavin T fluorescence, circular dichroism (CD), transmission electron microscope (TEM), and atomic force microscopy (AFM) experiments. Detailed analyses of hIAPP-SWCNT-OH interactions reveal that hydrogen bonding, van der Waals, and π-stacking interactions between hIAPP and SWCNT-OH significantly weaken the inter- and intrapeptide interactions that are crucial for β-sheet formation. Our collective computational and experimental data reveal not only the inhibitory effect but also the inhibitory mechanism of SWCNT-OH against hIAPP aggregation, thus providing new clues for the development of future drug candidates against T2DM.

Dispersion characteristics of hydroxyl and carboxyl-functionalized multi-walled carbon nanotubes in polyester nanocomposites

Abstract Multi-walled carbon nanotube (MWCNT) reinforced polyester-based composites were prepared by mixed blending in a solvent. Orthophthalic unsaturated polyester was blended individually with different types of non-functionalized and functionalized MWCNTs. Two types of functional groups: hydroxyl (-OH) and carboxyl (-COOH) were introduced with MWCNTs for the nanocomposites. The mechanical properties of the composites, like tensile, three-point bending and impact energy were evaluated. Fourier transform infrared spectroscopy was used for the functional group analysis. The dispersion characteristics of the samples were observed by transmission electron microscopy and field-emission electron microscopy. In addition, the thermal decomposition and melting behavior of the samples was assessed by differential scanning calorimetry and thermogravimetric analysis. The properties were varied due to the variation of the functional groups. The result analysis showed that the entangled agglomerations of hydroxyl-functionalized MWCNTs were destroyed to relatively smaller clusters. The hydroxyl-functionalized MWCNTs were more effective for homogeneous dispersion and contributed for better mechanical properties of the composites, compared to non-functionalized and carboxyl group-functionalized MWCNTs.

Resistance of Chlorides-Induced Corrosion of Steel Bar Embedded in CNTs-OH Modified Concrete

Aim of this paper is to evaluate the influence of hydroxyl carbon nanotubes (CNTs-OH) content (by 0.1-0.5% of cement weight) on the resistance of chlorides-induced corrosion of steel bar embedded in concrete. The corrosion process of concrete was monitored by using half-cell potential method (Ecorr, mv CSE). Test results show that the addition of CNTs-OH considerably increased the resistance of rebar chlorides induced corrosion of concrete, and the optimum content of CNTs was about 0.3% by mass of cement. Simultaneously, results also indicate that the measuring position impacted the corrosion potential value, in which the point on the water/air interface had the highest corrosion probability. In addition, the water absorption and SEM of concrete containing CNTs-OH were also investigated, and the pore-filling effect of CNTs-OH was observed to improve the properties of concrete.

Intercalation of rigid molecules between carbon nanotubes for adsorption enhancement of typical pharmaceuticals

A nucleophilic aromatic substitution reaction was proposed to synthesize porous carbon nanotubes (CNTs) to avoid their aggregation in solution. Hydroxylated carbon nanotubes (CNTs-OH) were reacted with different concentrations of rigid decafluorobiphenyl (DFB) to form the different CNTs-based adsorbents (CNT-DFB0.9, CNT-DFB1.8, CNT-DFB2.7 and CNT-DFB3.6). Among them, CNT-DFB1.8 exhibited the highest adsorption capacity for carbamazepine (CBZ) and tetracycline (TC) due to its higher specific surface area and pore volume than powdered CNTs. The proposed reaction was verified and the textural properties of the CNT-DFB adsorbent were characterized. The CNT-DFB1.8 adsorbent exhibited faster adsorption for CBZ than TC, and the maximum adsorption capacities for CBZ and TC were 403.0 and 456.5μmol/g respectively, according to the Langmuir fitting. With the increase of solution pH, TC adsorption on CNT-DFB1.8 decreased while CBZ adsorption increased. In addition, a simple thermal method was applied to regenerate the spent CNT-DFB1.8 by heating in air at 400°C, and the adsorption capacity changed little in the five adsorption cycles. This study provided a novel method to increase the dispersion of CNTs in the prepared adsorbent, showing the potential application for the removal of pharmaceuticals in water or wastewater treatment.

The physicochemical properties and catalytic performance of carbon-covered alumina for oxidative dehydrogenation of ethylbenzene with CO2

In order to correlate the physicochemical properties of carbon-covered alumina (CCA) materials with their catalytic performance for oxidative dehydrogenation of ethylbenzene with CO2 (CO2-ODEB), a series of CCA materials with diverse carbon contents (8.7–31.3wt%) and pyrolysis temperatures (600–800°C), which were synthesized via an impregnation method followed by pyrolysis, were applied. These catalytic materials were characterized by TGA, N2 physisorption, XRD, Raman spectroscopy and XPS techniques. It was found that the catalytic performance of these CCA materials highly depended on their physicochemical properties, and the optimum CCA catalyst exhibited much better catalytic stability than conventional hydroxyl carbon nanotubes. Below an optimum value of carbon content, the CCA catalyst preserved the main pore characteristics of the Al2O3 support and its catalytic activity increased with the carbon content. Excessive carbon loading resulted in significant textural alterations and thereby decreased both the ethylbenzene conversion and styrene selectivity. On the other hand, high pyrolysis temperature was detrimental to the ordered graphitic structure of the carbon species within the Al2O3 pore. The decreased ordered graphitic degree was found to be associated with the loss of the surface active carbonyl groups, consequently hampering the catalytic efficiency of the CCA catalyst.

Composite Films from Polystyrene with Hydroxyl end Groups and Carbon Nanotubes

Composites from polystyrene with hydroxyl end groups and multiwall carbon nanotubes were fabricated to evaluate their properties. The Carbon Nanotubes (CNTs) were synthetized by chemical vapor deposition technique using ferrocene and benzene as precursors. Polystyrene with hydroxyl end groups was prepared by solution polymerization employing styrene as monomer, 2-mercaptoethanol as chain transfer agent and AIBN as initiator. Thin films were obtained by two methods: pouring into petri dishes and dip-coating slides. CNTs were characterized to identify morphology and characteristic spectroscopic signals. The polystyrene with hydroxyl end groups and composites were analyzed by SEM, FTIR, Raman and UV-vis spectroscopies, Vickers microhardness and electrical resistivity. Raman analysis demonstrated chemical interactions between CNTs and polystyrene. Results showed that resistivity and transparency decreased by increasing CNTs concentrations in composites; transmittance was about 80% with 0.8 wt% content of nanotubes. The highest Vickers hardness registered value was at 1.6 wt% CNTs concentration.

Condensed dewdrops self-ejecting on sprayable superhydrophobic CNT/SiO2 composite coating

We report a type of novel condensed dewdrops self-ejecting coating from sprayable paint, which was prepared by a self-assembly process of SiO2 nano-particles on hydroxylated carbon nano-tubes with subsequent chemical modification.

Transparent conducting oxide-free nitrogen-doped graphene/reduced hydroxylated carbon nanotube composite paper as flexible counter electrodes for dye-sensitized solar cells

Abstract Three-dimensional nitrogen-doped graphene/reduced hydroxylated carbon nanotube composite aerogel (NG/CNT-OH) with unique hierarchical porosity and mechanical stability is developed through a two-step hydrothermal reaction. With plenty of exposed active sites and efficient multidimensional transport pathways of electrons and ions, NG/CNT-OH exhibits great electrocatalytic performances for I − /I 3 − redox couple. The subsequent compressed NG/CNT-OH papers possess high electrical conductivity and good flexibility, thus generating high-performance flexible counter electrodes (CEs) with transparent conducting oxide free (TCO-free) for dye-sensitized solar cells (DSSCs). The flexible NG/CNT-OH electrodes show good stability and the DSSCs with the optimized NG/CNT-OH CE had higher short-circuit current density (13.62 mA cm −2 ) and cell efficiency (6.36%) than DSSCs using Pt CE, whereas those of the DSSCs using Pt CE were only 12.81 mA cm −2 and 5.74%, respectively. Increasing the ratio of hydroxylated carbon nanotubes (CNT-OH) to the graphene oxide (GO) in the reactant would lead to less content of doped N, but better diffusion of electrolyte in the CEs because of more complete GO etching reaction. The design strategy presents a facile and cost effective way to synthesis three-dimensional graphene/CNT composite aerogel with excellent performance, and it can be potentially used as flexible TCO-free CE in other power conversion or energy storage devices.

Deposition of Carbon Nanotube Films on Polyamide and Polypropylene Substrates: A Computer Simulation Approach

In this work we study hydroxylated carbon nanotube (CNT) assembly on polyamide (PA) and polypropylene (PP) polymers activated by UV radiation from a theoretical and experimental perspective. Molecular computer simulation was done to understand the stable conformations and bulk properties (molecular dynamics) of the polymers before and after exposure to UV radiation at the molecular level. Our experiments suggest that PA presents more -OH active groups, producing a more hydrophilic surface, whereas PP exhibits less potential UV activation. These results suggest that it is possible a facile covalent functionalization method to tune organic polymer surface properties through SWCNT anchoring for nanotechnological applications requiring defined surface roughness and chemical functionality on inexpensive polymers.

Adsorption and bioaccessibility of phenanthrene on carbon nanotubes in the in vitro gastrointestinal system

Adsorption and bioaccessibility of phenanthrene on graphite and multiwalled carbon nanotubes (CNTs) were investigated in simulated gastrointestinal fluid using a passive dosing system. The saturated adsorption capacity of phenanthrene on different adsorbents follows an order of hydroxylated CNTs (H-CNTs)>carboxylated CNTs (C-CNTs)>graphitized CNTs (G-CNTs)>graphite, consistent with the order of their surface area and micropore volume. The change of phenanthrene adsorption on the adsorbents is different with the presence of pepsin (800mg/L) and bile salts (500mg/L and 5000mg/L, abbreviated as BS500 and BS5000). Both solubilization of phenanthrene by pepsin and bile salts and their competition with phenanthrene for the adsorption sites play a role. In addition, the large increase of the maximum adsorption capacity in BS5000 solution indicates an enhanced dispersion of CNTs or an exfoliation of graphite by bile salts, which consequently increases the exposed surface area. The bioaccessibility increases in pepsin and BS500 solution with a growing free phenanthrene concentration. Although the bioaccessibility of phenanthrene stalls or slightly decreases in the middle range of free phenanthrene concentration in BS5000 solution, the bioaccessibility overall is much higher than that in pepsin and BS500 solution at the same phenanthrene level. It is impossible to separate the effect of competition from dispersion (or exfoliation) at this stage, but the relative contribution of solubilization to phenanthrene desorption in pepsin and BS500 solutions was quantified, which improves our understanding of the mechanisms on bioaccessibility of adsorbed pollutants on CNTs.

Ultrastrong Chemiluminescence Activity of Nanocarbon Materials after Ozonation and Their Effects on Different Chemiluminescent Systems.

Ozonized nanocarbon materials with different dimensionalities, structures, and components exhibited significantly different chemiluminescence (CL) activities. The ozonation time and the weight ratio of hydroxyl carbon nanotubes (d≈8 nm, hyCNTs-8) and graphene oxide (GO) strongly affected the CL activity of ozonized hybrids. Among GO, hyCNTs-8, and GO/hyCNTs-8, the GO/hyCNTs-8 hybrids exhibited the strongest CL-enhancing properties toward the luminol/H2 O2 system, in contrast to previous reports. This study provides new understanding of the CL activity and CL-enhancing properties of nanocarbon materials in signal-enhanced analytical and biomedical fields.

Effect of different nanofillers on non-isothermal crystallization kinetics and electric conductivity of dynamically-vulcanized PP-EPDM Blends

In this study, nanofillers composed of hydroxylated carbon nanotubes (h-CNT), carbon nanotubes (CNT) and graphene (GR) were separately added into the dynamically-vulcanized polypropylene (PP)/ethylene-propylenediene monomer (EPDM) blend. Differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and electrical resistivity measurements were employed to study the effect of nanofillers on the melt behavior, non-isothermal crystallization behavior and electrical conductivity of the prepared composites. WAXD results showed that h-CNT had a better induction effect of β-PP in the nanocomposites. The sequence of the activity in inducing the formation of β-PP was h-CNT>GR>CNT. However, the total crystallinity of the nanocomposites nearly remained constant. Non-isothermal crystallization kinetic analysis indicated that the presence of nanofillers improved the crystallization rate of the nanocomposites. The consequence of nucleation activity was as follows: CNT>GR>h-CNT. Although EPDM hindered the macromolecular motion of PP, interestingly it could increase the crystallization rate to an extent. Besides, the influence of nanofillers on enhancing the conductive property of the nanocomposites can be ranked as follow: CNT>GR>h-CNT.