Magnetic Multi-walled Carbon Nanotubes Research Articles

Magnetic carbon nanotubes: synthesis by a simple solvothermal process and application in magnetic targeted drug delivery system

In this study, a new synthesis technique of magnetic multiwall carbon nanotubes (MMWCNTs) was achieved and its application for drug-loading ability was assessed. MMWCNTs were prepared by a simple solvothermal process, which can easily alter the size (100–350 nm), location, and denseness of Fe3O4 beads fixed on MWCNTs as well as the MWCNTs structure via controlling the reaction parameters. The characteristics of MMWCNTs obtained were assessed by scanning electron microscopy, X-ray diffraction, and FTIR. The MMWCNTs were used as a drug carrier to load an anticancer molecule, epirubicin hydrochloride. In addition, its adsorption ability was also evaluated. The Freundlich adsorption model was successfully used to describe the adsorption process. The kinetic data was well fitted with a pseudo-second-order model. Due to its magnetic properties, high adsorption surfaces, and excellent adsorption capacities, the MMWCNTs synthesized in this study are suitable to be applied to a magnetic targeted drug delivery system.

Adsorption of bilirubin to magnetic multi-walled carbon nanotubes as a potential application in bound solute dialysis

Carbon nanotubes (CNTs) have excellent adsorption properties for a wide range of substances, but the leakage of CNTs into blood and the non-specific adsorption of plasma proteins are major issues in the application of CNTs in blood purification. To minimize these shortcomings, multi-walled carbon nanotubes (MWCNTs)/iron oxides magnetic composites were prepared and intended to be used in bound solute dialysis. Magnetic MWCNTs were characterized by FTIR, XRD, SEM, VSM and Boehm titration. Their adsorption characteristic for bilirubin (a prominent marker of liver failure disease) was measured in aqueous solutions. The magnetic MWCNTs that theoretically contained 50% of 4h-pre-treated MWCNTs and 50% of magnetite could meet the requirements for good dispersion ability, high adsorption capacity for bilirubin, and the convenience of magnetic separation. The magnetic MWCNTs showed a rapid rate for the uptake of bilirubin, and maximum adsorption capacity could reach 263.16mg/g at 30°C. Besides, the adsorption isotherm was well described by Langmuir model, and the adsorption process was thermodynamically favorable. The binding constant for the adsorption of bilirubin to magnetic MWCNTs was 1.8×105M−1 at 30°C. In bound solute dialysis, 35% of bilirubin could be removed from a solution of albumin without significant effect on the concentration of albumin. This study demonstrated that magnetic MWCNTs could offer a new type of adsorbent for removal of albumin bound toxins in bound solute dialysis.

Facile method to prepare magnetic multi-walled carbon nanotubes by in situ co-precipitation route

An effective method for preparing magnetic multi-walled carbon nanotubes (M-MWCNTs) was proposed by employing an in situ co-precipitation of ammonium ferrous sulfate hexahydrate and ammonium ferric sulfate dodecahydrate in a suspension of commercial MWCNTs. Microscopic and spectroscopic analyses could confirm the presence of magnetite, maghemite and hematite on the surface of M-MWCNTs. Negative charges on the surfaces of acid-treated MWCNTs would lead to the attachment of iron derivatives which possessed positive charge due to electrostatic attraction. As a result, the prepared M-MWCNTs were clearly responsive to a permanent magnetic while the pristine MWCNTs were not.

Fast microextraction of phthalate acid esters from beverage, environmental water and perfume samples by magnetic multi-walled carbon nanotubes

In this work, magnetic carbon nanotubes (CNTs) were prepared by mixing the magnetic particles and multi-walled carbon nanotubes dispersed solutions. Due to their excellent adsorption capability towards hydrophobic compounds, the magnetic CNTs were used as adsorbent of magnetic solid-phase extraction (MSPE) to extract phthalate acid esters (PAEs), which are widely used in many consumable products with potential carcinogenic properties. By coupling MSPE with gas chromatography/mass spectrometry (GC/MS), a rapid, sensitive and cost-effective method for the analysis of PAEs was established. Our results showed that the limits of detection (LODs) of 16 PAEs ranged from 4.9 to 38ngL−1, which are much lower compared to the previously reported methods. And good linearities of the detection method were obtained with correlation coefficients (R2) between 0.9821 and 0.9993. In addition, a satisfying reproducibility was achieved by evaluating the intra- and inter-day precisions with relative standard deviations (RSDs) less than 11.7% and 14.6%, respectively. Finally, the established MSPE-GC/MS method was successfully applied to the determination of PAEs from bottled beverages, tap water and perfume samples. The recoveries of the 16 PAEs from the real samples ranged from 64.6% to 125.6% with the RSDs less than 16.5%. Taken together, the MSPE-GC/MS method developed in current study provides a new option for the detection of PAEs from real samples with complex matrices.

Highly stable magnetic multiwalled carbon nanotube composites for solid-phase extraction of linear alkylbenzene sulfonates in environmental water samples prior to high-performance liquid chromatography analysis

The magnetic multiwalled carbon nanotubes (MMWCNTs) have been successfully prepared using a one-pot chemical coprecipitation method, in which magnetic nanoparticles (MNPs) were deposited onto multiwalled carbon nanotubes (MWCNTs) by in situ high temperature decomposition of the magnetic precursor of iron(III) in ethylene glycol media. A novel procedure for extraction of linear alkylbenzene sulfonates (LAS) as a model compound was thus developed in an off-line extraction system with detection by HPLC. The procedure includes the separation and preconcentration of LAS homologues onto MMWCNTs at pH 7.0 and their subsequent detection after sonication elution, followed by the separation of the MMWCNTs from the aqueous phase by external magnetic field and washing with ultra pure water. With a sample volume of 500 mL and 100 mg MMWCNTs sorbents, an enrichment factor of about 500, and a detection limit of 0.013-0.021 μg L(-1) were obtained within a linear range of 0.5-100 μg L(-1), together with a correlation coefficient of 0.9938-0.9998 for four LAS homologues. A precision of 2.4-5.6% was obtained for six replicate determinations of 50 μg L(-1) LAS. The recoveries of LAS homologues spiked in environmental water samples ranged from 87.3 to 106.3%, demonstrating the utility of the MMWCNTs adsorbents in a series of water samples. Stability testing demonstrated that the MMWCNTs remained 95.0% recovery for the target LAS even after a run of 50 adsorption and desorption cycles, showing their super operational stability. The MMWCNTs are promising adsorbents, suitable for the long-term repetitive sorption/desorption of target compounds in environmental water samples.

Poly(lactide)-functionalized and Fe3O4 nanoparticle-decorated multiwalled carbon nanotubes for preparation of electrically-conductive and magnetic poly(lactide) films and electrospun nanofibers

Polymer-functionalized magnetic multiwalled carbon nanotubes (MWCNTs) have been prepared by a 2-step process. Fe3O4 nanoparticles are first decorated onto MWCNTs through Diels–Alder reaction. The resulting magnetic MWCNTs have been functionalized with polymers through an ozone-mediated process, which is able to incorporate kinds of matrix polymers to the magnetic MWCNTs. Poly(lactide)-functionalized magnetic MWCNTs (mCNT–PLA) have been prepared in this work for preparation of electrically-conductive and magnetic poly(lactide)/MWCNTs composite films and electrospun fibers. The magnetic and electrically-conductive feature of the functionalized MWCNTs helps to the formation of nanofibers in the electrospinning process of poly(lactide). The nanofibers possessing 0.3 wt% of mCNT–PLA exhibit a Young's modulus and an elongation at break of 25 MPa and 150%, respectively. Compared to the values of 9 MPa and 12% shown with the neat PLA electrospun fibers, the presence of mCNT–PLA not only strengthens but also toughens the PLA-based electrospun fibers.

Determination of bisphenol A, bisphenol F and their diglycidyl ethers in environmental water by solid phase extraction using magnetic multiwalled carbon nanotubes followed by GC-MS/MS

The magnetic multiwalled carbon nanotube (MWCNT-MNP) was successfully synthesized. MWCNT-MNP and gas chromatography-tandem mass spectrometry (GC-MS/MS) were used for rapid, simple and reliable determination of bisphenol A (BPA), bisphenol F (BPF), bisphenol F diglycidyl ether (BFDGE) and bisphenol A diglycidyl ether (BADGE) at trace levels in water. The major factors affecting the recovery efficiency, such as amount of MWCNT-MNP, pH of water sample and sample volume, were carefully investigated. The recovery of these compounds was in the range of 88.5–115.1% with relative standard deviation less than 10%. Good linearities (r2 > 0.995) were obtained. The limits of detection for BPA, BPF, BFDGE and BADGE were 0.001, 0.002, 0.06, and 0.05 μg L−1, respectively. Finally, the method was applied to tap water, river water and snow water, the results show that the developed method is suitable for monitoring trace BPA, BPF, and their diglycidyl ethers in environmental water samples.

Determination of trace leaching phthalate esters in water by magnetic solid phase extraction based on magnetic multi-walled carbon nanotubes followed by GC-MS/MS

A magnetic solid phase extraction method coupled to gas chromatography–tandem mass spectrometry was proposed for the determination of phthalate esters at trace levels in drinking water. The magnetic multi-walled carbon nanotubes were prepared and applied as sorbents for magnetic solid phase extraction. The major factors affecting the recovery efficiency, such as the amount of magnetic multi-walled carbon nanotubes, pH of the water sample, desorption conditions and extracting time were carefully investigated. The recovery of these compounds was in the range of 86.6–100.2% with a relative standard deviation (RSD) value of less than 10%. Good linearities (r > 0.9993) were obtained. The limits of detection for phthalate esters were in the range of 0.009–0.032 μg L−1. The results show that the developed method is suitable for the monitoring of trace phthalate esters in drinking water samples.

PEG-conjugated highly dispersive multifunctional magnetic multi-walled carbon nanotubes for cellular imaging

We report synthesis of a highly versatile multicomponent nanosystem by covalently decorating the surface of multiwalled carbon nanotubes (CNTs) by magnetite nanoparticles (Fe(3)O(4)), poly(ethylene glycol) (PEG), and fluorophore fluorescein isothiocyanate (FITC). The resulting Fe(3)O(4)-PEG-FITC-CNT nanosystem demonstrates high dispersion ability in an aqueous medium, magnetic responsiveness, and fluorescent capacity. Transmission electron microscopy images revealed that Fe(3)O(4) nanoparticles were well anchored onto the surfaces of the CNT. In vitro time kinetic experiments using confocal microscopy demonstrated a higher uptake of the Fe(3)O(4)-PEG-FITC-CNT nanosystem localized at the perinuclear region of MCF7 cells compared to the free FITC. In addition, the CNT nanosystem demonstrated no evidence of toxicity on cell growth. Surface conjugation of multicomponents, combined with in vitro non-toxicity, enhanced cellular uptake for FITC and site specific targeting ability makes this fluorescent Fe(3)O(4)-PEG-FITC-CNT nanosystem an ideal candidate for bioimaging, both in vitro and in vivo.

Laccase biosensor using magnetic multiwalled carbon nanotubes and chitosan/silica hybrid membrane modified magnetic carbon paste electrode

A simple and rapid strategy to construct laccase biosensor for determination of catechol was investigated. Magnetic multiwalled carbon nanotubes (MMCNT) which possess excellent capability of electron transfer were prepared by chemical coprecipitation method. Scanning electron microscope (SEM) and vibrating sample magnetometer (VSM) were used to identify its surfacetopography and magnetization, respectively. Laccase was immobilized on the MMCNT modified magnetic carbon paste electrode by the aid of chitosan/silica (CS) hybrid membrane. Using current-time detection method, the biosensor shows a linear response related to the concentration of catechol in the range from 10−7 to 0.165×10−3 mol/L. The corresponding detection limit is 3.34×10−8 mol/L based on signal-to-noise ratios (S/N) ≥3 under the optimized conditions. In addition, its response current retains 90% of the original after being stored for 45 d. The results indicate that this proposed strategy can be expected to develop other enzyme-based biosensors.

Rapid Magnetic Solid-Phase Extraction Based on Magnetic Multiwalled Carbon Nanotubes for the Determination of Polycyclic Aromatic Hydrocarbons in Edible Oils

In this study, magnetic multiwalled carbon nanotubes were fabricated by a simple method and applied to magnetic solid-phase extraction (MSPE) of eight heavy molecular weight polycyclic aromatic hydrocarbons (PAHs) including chrysene, benzo[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, dibenzo[a,h]anthracene and benzo[g,h,i]perylene from edible oil samples. Several parameters affecting the extraction efficiency were investigated, including the type and volume of desorption solvent, extraction and desorption time, washing solution and the amount of sorbent. Under the optimized conditions, a simple and effective method for the determination of PAHs in edible oils was developed by coupling with gas chromatography-mass spectrometry (GC-MS). The whole pretreatment process was rapid, and it can be accomplished within 10 min. The limits of quantitation for the target PAHs were found to be 0.34-2.9 ng/g. The recoveries in oil sample were in the range 87.8-122.3% with the RSDs less than 6.8% (intraday) and 9.6% (interday). This method was successfully applied to the analysis of PAHs in seven kinds of edible oils from local markets.

Lipase immobilized on magnetic multi-walled carbon nanotubes

Magnetic iron oxide nanoparticles were loaded onto the surfaces of multiwalled carbon nanotubes (MWNTs) by the impregnation method. The obtained magnetic nanotubes were characterized with high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Yarrowia lipolytica lipase was covalently immobilized on the magnetic MWNTs (M-MWNTs). M-MWNT-lipase was characterized with XPS spectra and XRD patterns. The structural change of the immobilized lipase was analyzed through circular dichroism spectroscopy. M-MWNT-lipase was utilized for the resolution of (R, S)-1-phenyl ethanol in the organic solvent of heptane. Compared to the native lipase, the lipase immobilized on M-MWNTs has significantly improved its enzymatic activity for the resolution of (R, S)-1-phenyl ethanol in heptane. M-MWNT-lipase can be easily recovered after catalysis. In addition, the effect of sonication time on the catalytic activity was also investigated. It is found that, up to 30min sonication, the catalysis by M-MWNT-lipase is almost not affected. While, the catalytic activity of the native lipase is decreased with sonication time.

Enhanced reflection loss and permittivity of self assembled Mg–Co–Zr substituted barium ferrite dot array on carbon nanotube

In this research work, magnetic multi-walled carbon nanotube (MWCNTs) nanocomposites have been created by the assembly of Mg–Co–Zr substituted barium ferrite film onto the surface of MWCNTs. Microwave absorption of the MWCNTs/doped barium ferrite nanocomposites is evidently enhanced compared to that of pure MWCNTs and substituted ferrites. The maximum reflection loss increased significantly with an increase in volume percentage of MWCNTs. Reflection loss evaluations indicated that nanocomposites display a great potential application as thinner and lighter wide-band electromagnetic wave absorbers.

Magnetic field-guided orientation of carbon nanotubes through their conjugation with magnetic nanoparticles

Low intensity magnetic fields (22mT) rendered by a pair of bar magnets have been used to achieve in situ precise orientation of multiwalled carbon nanotubes (MWCNTs) and their directional deposition on solid substrates. The nanotubes were imparted magnetic characteristics through Fe3O4 (magnetite) nanoparticles covalently attached to their surface. The side walls of nanotubes were first acid oxidized with H2SO4/HNO3 (3:1 v/v) mixture and amine-functionalized magnetic nanoparticles were then interfaced to ends and side walls of the nanotubes through covalent linkages in the presence of a zero length cross linker, 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide. Fourier transformed infrared spectroscopic investigations affirmed the functionalization of nanostructures and formation of a magnetic nanohybrid. Transmission electron microscopy results revealed the attachment of nanoparticles along the side walls of MWCNTs. A flow cell was utilized to orient magnetic nanohybrid in the desired direction and also to create thin films of aligned MWCNTs. Further, directional assembly of magnetic MWCNTs at different orientation angles on solid substrates was studied by field emission scanning electron microscopy and optical microscopy. The procedure can be scaled to align CNTs on large surface areas for numerous applications, e.g., nanosensors, field emitters, and composites.

Magnetic and Reflection Loss Characteristics of Substituted Barium Ferrite/Functionalized Multiwalled Carbon Nanotube

Magnetic multiwalled carbon nanotube (MWCNTs) nanocomposites have been created by the assembly of Mg-Ni-Ti substituted barium ferrite nanoparticles onto surface of MWCNTs. X-ray diffraction (XRD) and transmission electron microscope (TEM) were used to demonstrate the successful attachment of ferrite nanoparticles to MWCNTs. Vibrating sample magnetometer (VSM) confirms the relatively strong dependence of saturation of magnetization and coercivity with the volume percentage of MWCNTs. Reflection loss evaluations indicated that the nanocomposites display a great potential application as wide-band electromagnetic wave absorbers.

Dual targeted delivery of doxorubicin to cancer cells using folate-conjugated magnetic multi-walled carbon nanotubes

By combining the advantage of multi-walled carbon nanotubes (MWCNTs) and iron oxide magnetic nanoparticles (MNs), we develop a magnetic dual-targeted nanocarrier for drug delivery. MWCNTs were functionalized with poly(acrylic acid) through free radical polymerization, decorated with MNs, conjugated with a targeting ligand folic acid (FA), for loading of an anti-cancer drug doxorubicin (DOX). The proposed methodology provides dual targeted delivery of the anti-cancer drug to cancer cells under the guidance of a magnetic field and through ligand–receptor interactions. The chemico-physical properties of the nanocarrier were characterized, in addition to its drug loading efficiency and drug releasing characteristics. Doxorubicin could be loaded to MWCNTs with high efficiency via π–π stacking and hydrogen bonding and showed enhanced cytotoxicity toward U87 human glioblastoma cells compared with free DOX. From transmission electron microscopy and confocal laser scanning microscopy, we confirmed that DOX-FA-MN-MWCNT could be efficiently taken up by U87 cells with subsequent intracellular release of DOX, followed by transport of DOX into the nucleus with the nanocarrier left in the cytoplasm. These properties make the magnetic nanocarrier a potential candidate for targeted delivery of DOX for cancer treatment.

Microwave assisted fast fabrication of Fe 3O 4-MWCNTs nanocomposites and their application as MRI contrast agents

Uniform Fe 3O 4 nanoparticles with diameters of 3–5 nm are successfully decorated onto the external walls of multiwall carbon nanotubes (MWCNTs) by in situ high-temperature decomposition of Fe(acac) 3 in polyol solution under the irradiation of microwave. With this method, reaction time of forming Fe 3O 4-MWCNTs nanocomposites has been significantly shortened to 15 min. The resulting Fe 3O 4-MWCNTs nanocomposites show superparamagnetic property at room temperature and can be remained as stable aqueous dispersion for 2 months. Longitudinal relaxivity (r 1) and transverse relaxivity (r 2) of the magnetic MWCNTs are 8.34 Fe mM −1 S −1 and 146 Fe mM −1 S −1 respectively. The much higher r 2 value and the obvious change in the gray scale of MR images confer the Fe 3O 4-MWCNTs nanocomposites as potential candidates for T 2-weighted MRI contrast agents.

Magnetic multi-walled carbon nanotubes assisted dispersive solid phase extraction of nerve agents and their markers from muddy water

The multi-walled carbon nano-tubes (MWCNT) were magnetized with iron oxide nanoparticles and were characterized by SEM and EDX analyses. These magnetized MWCNT (Mag-CNT) were used as sorbent in dispersive solid phase extraction (DSPE) mode to extract nerve agents and their markers. Mag-CNT were dispersed in water and collected with the help of an external magnet. From Mag-CNT, the adsorbed analytes were eluted and analyzed by GC-FPD in phosphorus mode. DSPE was found to be advantageous over conventional solid phase extraction (SPE) in terms of operational simplicity, speed, handling of large sample volume and recoveries. Extraction parameters such as eluting solvent, sorbent amount, pH and salinity of aqueous samples were optimized. Optimized extraction conditions included 40mg of Mag-CNT as sorbent, chloroform as eluent, pH 3–11 and salinity 20%. Under the optimized conditions, recoveries from distilled water ranged from 60 to 96% and were comparable in tap and muddy water. Limits of quantification and limits of detection of 0.15ng/ml and 0.05ng/ml, respectively, were achieved. Superiority of Mag-CNT over conventional C18 SPE was also established.

Enabling electrochemical studies of chemically-modified carbon nanotubes in non-aqueous electrolytes using superparamagnetic nanoparticle-nanotube composites co-modified by diazirine molecular “tethers”

Multiwalled carbon nanotubes (MWCNTs) were covalently modified with polymer-coated superparamagnetic Fe 3O 4 nanoparticles via amide bond formation to surface oxo-groups located predominantly at the ends of the nanotubes to form “magnetic MWCNTs”. The sidewalls of the magnetic MWCNTs were then selectively covalently modified with ferrocenyl groups via the photolysis of 3-[3-(trifluoromethyl) diazirin-3-yl] phenyl ferrocene monocarboxylate, which uses an aryldiazirine moiety as a molecular “tether”. We demonstrate that the assembly of the chemically-modified magnetic MWCNTs onto the surface of a magnetic carbon electrode enables one to obtain stable voltammetric signals of chemically-modified carbon nanotubes in non-aqueous electrolytes even under vigorous hydrodynamic conditions of stirring at 3000 rpm for up to twenty minutes. In contrast, non-magnetic chemically modified MWCNTs are removed from the electrode surface within the first two minutes of stirring.

Remarkable influence of carbon nanotubes on microwave absorption characteristics of strontium ferrite/CNT nanocomposites

In this research work, magnetic multi-walled carbon nanotube (MWCNT) nanocomposites have been created by the assembly of Zn–Sn substituted strontium ferrite film onto the surface of MWCNTs. X-ray diffraction and transmission electron microscopy were used to demonstrate the successful attachment of ferrite films to MWCNTs. Mössbauer spectroscopy indicates that the Zn–Sn ions preferentially occupy the 2b and 4f2 sites. Vibrating sample magnetometry confirms the relatively strong dependence of saturation magnetization with the volume percentage of MWCNTs. Microwave absorption of the MWCNTs/doped strontium ferrite nanocomposites is evidently enhanced compared to that of pure MWCNTs and ferrite. The maximum reflection loss increased significantly with an increase in volume percentage of MWCNTs in nanocomposites. Reflection loss evaluations indicated that the nanocomposites display a great potential application as wide-band electromagnetic wave absorbers.