Walls Of Multi-walled Carbon Nanotubes Research Articles

Flexible multiwalled carbon nanotubes/cellulose nanofibers membrane with rapid temperature increasing induced by interface strengthening

Towards advanced electrical heaters with superior Joule heating property, high electrical conductivity has always been critical issue. Herein, in addition to the commonly recognized factor of electrical conductivity, we proved that the composite interface poses significant effect on temperature increasing as electrical heaters. Specifically, direct fluorination utilizing F2/N2 was applied to selectively decorate the outer walls of multiwalled carbon nanotubes (MWCNTs) while keeping the inner tube intact, which was followed by compositing it with cellulose nanofibers (CNFs) to prepare F-MWCNTs/CNFs flexible membrane. Due to the enhanced electrostatic interaction at the interface and stronger phonon vibrational coupling, interfacial phonon diffusion was significantly improved, which facilitated a higher temperature increase rate in the F-MWCNTs/CNFs membrane compared to the unmodified MWCNTs/CNFs membrane when subjected to an electric field. This unique interfacial effect holds promise for the development of high-performance electrical heaters with rapid response.

Multiwalled carbon nanotubes as hard templates to yield advanced geopolymer-based self-assembled nanostructured ceramics

Novel multifunctional construction materials are needed to promote resilient infrastructure in the face of climate change and extreme weather. Nanostructured materials such as geopolymer reinforced with carbon-based nanomaterials are a promising way to reach that goal. In recent years, several studies have investigated the influence of nanomaterials on the physical properties of geopolymer composites such as compressive strength and fracture toughness. Yet, a fundamental understanding of the influence of nanomaterials on the nanoscale and micron-scale structure has been elusive so far. Our research objective is to understand how multiwalled carbon nanotubes (MWCNT) can help tailor the microstructure of geopolymers to yield architected multifunctional nanocomposites. We synthesized geopolymer nanocomposites reinforced with 50-nm thick multiwalled carbon nanotubes with mass fractions in the range of 0.1 wt%, 0.2 wt%, and 0.5 wt%. Our major finding is that MWCNTs act as hard templates that promote geopolymer formation via self-assembly. Geopolymer nanoparticle growth is observed along the walls of MWCNTs. A refinement in grain size is observed: increasing the fraction of MWCNTs by 0.5 wt% leads to a reduction in grain size by 54%. Similarly, increasing the mass fraction of MWCNTs leads to a densification of the geopolymer matrix as demonstrated by the Fourier transform infrared spectroscopy results and the statistical deconvolution analysis. Mercury intrusion porosimetry shows a nanoscale tailoring of the pore size distribution: a 26% decrease in porosity is observed as the fraction of MWCNTs is increased to 0.5 wt%. As a result of these nanoscale structural changes, a greater resistance to long-term deformation is observed for MWCNT-reinforced geopolymers, as the creep modulus increases both locally and macroscopically. At the macroscopic level, a 42% increase in the macroscopic logarithmic creep modulus is observed as the fraction of MWCNTs is increased to 0.5 wt%. These findings and the supporting methodology are important to understand how to manipulate matter below 100 nm. This research also paves the way for the design of resilient infrastructure materials with tailored microstructure and mechanical properties.

Multifunctional modified carbon nanotubes as potential anti-tumor drug delivery

The main issues associated with antitumor chemotherapy are the nonspecific and systemic toxicity induced by different types of drugs. In the other hand, the ability of tumor cells to hinder the internalization and metabolism of chemotherapy drugs affects the efficacy of antitumoral therapies. In this context, our work hypothesizes that the development of novel drug delivery systems targeting alternative sites could serve as a strategy to deliver specific and effective antitumoral activity. This study focuses on the synthesis, chemical characterization and biological evaluation of a novel rational dual drug delivery system (DDS) based on non-covalent functionalization. The DDS employed multi-walled carbon nanotubes (MWCNT) as vectors, which are conjugated with folic acid (FA) to facilitate targeted delivery to tumor sites and enhance bioavailability. Additionally, digoxin (DGX) was incorporated as a cytotoxic agent. Several characterization techniques such as X-ray diffraction, thermogravimetric analysis, Raman and infrared spectroscopy were employed to identify the characteristics attributed to the carbon-based nanomaterials and the organic molecules attached on the MWCNT. Transmission electron microscopy analysis revealed the presence of adsorbed aggregates on the surface of the nanotubes. In silico molecular docking studies identified energetically favorable interaction modes between FA and DGX on the MWCNT walls. A drug release assay was performed to elucidate the mechanism of action of the dual drug delivery system. Subsequently, MWCNT, digoxin and the newly developed hybrids were incubated with HeLa cells (cervical cancer) to assess cell viability using the MTT reduction assay. Our findings demonstrated the absence of acute cytotoxicity associated with MWCNT, whereas the DDS exhibited significant cytotoxicity, reducing tumor cell viability at safe concentrations of digoxin. These results shed light on the design and advantages of novel rational drug delivery systems that explore the potential of MWCNT, repurposed antitumor drugs, and membrane tumor biomarkers. Importantly, the synthesis of a dual drug delivery system comprising digoxin and folic acid represents a pioneering achievement in the field to date.

Long-Chain Modification of the Tips and Inner Walls of MWCNTs and Their Nanocomposite Reverse Osmosis Membranes.

Multi-walled carbon nanotubes (MWCNTs) were modified on the tips and inner walls by 12-chloro-12-oxododecanedioic acid-methyl ester groups and then added to the polyamide composite membranes to prepare MWCNT-CH2OCOC12H23O2 membranes for desalination. The characterization results of transmission electron microscopy, Fourier transform, infrared transform, and thermogravimetric analysis showed that the 12-chloro-12-oxododecanedioic acid-methyl ester group was successfully grafted to the entrances and inner walls of the MWCNTs. The performance of the MWCNTs’ composite membranes was evaluated by scanning electron microscopy, contact angle, and filtration test. The modified membrane morphology is more uniform, and there is no structural damage. The grafting of carbon nanotubes with methyl 12-chloro-12-oxydodecyldicarboxylate could improve the hydrophilicity of the membrane. Under identical conditions, the water flux of MWCNT-CH2OCOC12H23O2 membranes was higher than that of the pristine carbon nanotube’s membrane, and the desalination rate was also slightly improved.

Manipulating MWCNT/TiO2 heterostructure morphology at nanoscale and its implications to NO2 sensing properties

Multi-walled carbon nanotubes (MWCNTs) based heterostructures were prepared by oxygen plasma treatment and atomic layer deposition (ALD) of TiO2 carried on MWCNTs. Different TiO2 structures (island, granular and continuous forms) on the nanotubes were obtained by varying the processing parameters. Chemical inertness of MWCNTs led to the ALD of TiO2 in an island form. Oxygen plasma treatment ensured deposition of a continuous TiO2 film, 5 nm in thickness. A granular form of TiO2 was obtained on oxygen plasma treated MWCNTs using shorter duration of Ti-precursor pulse. Different imaging modes in high resolution transmission electron microscopy visualized TiO2 nanostructures and defects in MWCNT walls. The latter were also confirmed by Raman spectroscopy. The morphology of TiO2 and oxygen plasma treatment of the MWCNTs highly affected the NO2 sensing behavior of chemiresistive heterostructure sensors at room and elevated temperatures. All investigated sensors exhibited a decrease in the resistance upon exposure to NO2 gas which implies a p-type sensor response. The granular TiO2/MWCNTs heterostructure showed the highest response towards NO2 gas as compared to the island and continuous forms.

Optimization of self heating properties of Fe3O4 using PEG and amine functionalized MWCNT

An attempt has been made to bridge between the influence of surface modification at nanoscale and the biomedical applicability of multifunctional nanocomposite. Fe3O4 synthesized via solvothermal route has been made nanocomposite with Polyethylene glycol (PEG) and Amine functionalized Multiwall Carbon nanotube (MWCNT). Formation of Fe3O4 phase has been confirmed by X-ray diffraction (XRD). Functionalization of MWCNT with PEG and Amine has been recognized by Fourier transform infrared (FTIR) Spectra. Thermogravimetric analysis (TGA) discerned the adhesion of functional groups onto MWCNT and also the loading of functionalized MWCNT in the nanocomposite. Besides the visible evidence of interaction of spherical Fe3O4 onto walls of MWCNT provided by High-resolution transmission electron microscopy (HRTEM), there are other inferences led by the influence of this functionalized group. Crystallographic information from Rietveld analysis of the XRD pattern infers the impact of functionalized MWCNT on cation distribution in the Fe3O4 spinel structure. Vibrating sample magnetometer (VSM) studies revealed near superparamagnetic nature of as-synthesized samples, with 17% rise and 19% fall in the Coercivity of PEG-o-MWCNT/Fe3O4 and Amine-o-MWCNT/Fe3O4 than bare Fe3O4 respectively. A comparison of the Specific absorption rate suggested that under an oscillating magnetic field, nanocomposites are capable as an agent of heat generation as bare Fe3O4, even better at the higher field amplitude for tuning with magnetic anisotropy.

Synthesis and formation mechanism of novel double-thick-walled silicon carbide nanotubes from multiwalled carbon nanotubes

In this study, double-thick-walled (DTW) silicon carbide (SiC) nanotubes, the walls of which comprise connected disordered polycrystalline nanograins, were successfully synthesized for the first time via the reaction of multiwalled carbon nanotubes (MWCNTs) with Si powder. DTW SiC nanotubes are expected to exhibit novel properties unlike other SiC nanomaterials, owing to their intriguing geometries. The DTW SiC nanotubes had a wall thickness exceeding 20 nm, regardless of the external diameter, as indicated by transmission electron microscopy results. The DTW SiC nanotubes with a spacing of above 30 nm between the outer and inner nanotubes exhibited perfect double-walled structures. The inner and outer nanotubes were not connected in any region. When all the carbon was transformed into SiC, the volume of carbon increased to 2.2 times the initial value. These results reveal that DTW SiC nanotubes with perfect structures cannot be synthesized without an MWCNT wall thickness of at least 50 nm. Several types of DTW SiC nanotubes with different morphologies, such as diameter, end structure, and distance between the inner and outer nanotubes, were synthesized. The morphology of DTW SiC nanotubes can be controlled by changing the wall thickness and/or diameter of the original MWCNTs and the reaction conditions.

Nanocomposites of multi-walled carbon nanotubes with encapsulated cobalt

A new nanocomposite material involving multi-walled carbon nanotubes (MWCNTs) was synthesized using the traditional chemical vapor deposition (CVD) method. The objective of this investigation was to embed and encapsulate metal (cobalt) nanoparticles inside the MWCNTs in a one-step CVD process. The morphological and structural characterization of MWCNTs-based nanocomposites was performed using scanning electron micrscopy (SEM), high resolution transmission electron microscopy (HRTEM), thermal gravimetry analysis (TGA), Brunauer, Emmett and Teller theroy (BET surface area), and Raman spectroscopy. HRTEM confirmed the formation of Co encapsulated MWCNTs (Co@MWCNTs), whose average diameter was 27 nm. Surface area of the nanocomposites was determined by the BET method, which was found to be 40 m2 g−1 for the MWCNTs and 120 m2 g−1 for the Co@MWCNTs nanocomposite, respectively. The crystallinity of the MWCNTs and Co@MWCNTs was analyzed using Raman spectra, where the ratio of intensities of D and G band for the MWCNTs was 0.94 and 0.80 for the Co@MWCNTs, respectively. Electrochemical evaluation of the Co@MWCNTs nanocomposite was performed by cyclic voltammetry in 5 M KOH solution. The Co@MWCNTs nanocomposite displayed oxidation in alkaline media with onset potential at 0.55 V vs. SHE. This new approach of synthesizing nanocomposites where metal particles are encapsulated between the walls of MWCNTs could lead to the development of new, efficient and interesting electrocatalysts.

Optimized protocol for the preparation of multi-walled carbon nanotube:polystyrene transducers for electrochemical sensing

A practical method is presented to prepare films of a composite material constituted of multi-walled carbon nanotubes (MWCNTs) and polystyrene (PS) that are used for transduction applications. The method, which can be carried out by employing usual lab equipment, is simple, low-cost, rapid, and nonpolluting. Furthermore, it is compatible with microelectronic fabrication technology and is scalable for mass production. For designing this method, we studied how the number of drop-casted composite layers, the temperature used for curing the samples, and the duration of this thermal treatment influence on the electrochemical performance of a Si/SiO2/Au/MWCNT:PS electrode. The optimum electrochemical responses of the Si/SiO2/Au/MWCNT:PS electrode were obtained with films prepared with four layers of MWCNT:PS composite, each cured at 80 °C for 15 min. Under these conditions, the MWCNT walls are exposed and readily accessible for subsequent functionalization.

Preliminary study on immobilization of plant esterase on functionalized multi-walled carbon nanotubes (MWCNTs) for biosensor application

The functionalization of multi-walled carbon nanotubes (MWCNTs) is extremely important to increase their solubility. This study reported the efficient functionalization of MWCNTs via acid treatment introducing carboxyl group at the side wall of MWCNTs by mixing the concentrated nitric and sulfuric acid. Plant esterase enzyme extracted from wheat flour called alpha naphthyl acetate esterase (ANAE) was immobilized onto functionalized MWCNTs via covalent attachment of amine group in ANAE and carboxyl group of functionalized MWCNTs. In order to characterize the functionalization of MWCNTs and immobilization of enzyme, Fourier transform infrared (FTIR) spectroscopy have been used to confirm the existence of these functional groups. The FTIR spectrums revealed that the several peaks formed at 1992.39, 2324.14, 2880.85 and 3029.51 cm−1 which can be assigned to the C=O symmetric stretching, O−H stretch from strongly hydrogen-bonded –COOH, H−C stretch modes of H−C=O in the carboxyl group, and O-H stretch from carboxyl groups (O=C−OH and C−OH) respectively. The immobilization of ANAE on functionalized MWCNTs confirmed by observation of the peak at 3646.81 cm−1 and 3850.91 cm−1 introduced the strong amide linkages between carboxylic acid groups and amine group on the MWCNTs. This proposed framework can be applied for fabrication of screen printed electrode as biosensor for detection of pesticide.

Synthesis and property of novel gas mixed-matrix membrane with carbon nanotubes

Mixed matrix membranes (MMMs) were fabricated by incorporating carboxylated multi-walled carbon nanotubes (MWCNTs) into a poly (arylene fluorene ether ketone) that contained amino groups (Am-PAFEK) matrix to improve CO2 separation performance. The combination of MWCNTs and Am-PAFEK exerted a favorable synergistic effect on the permeability and selectivity of membranes. The extraordinary smooth wall of MWCNTs acts as a highway through which gas passes, providing better permeability. The Am-PAFEK matrix itself has a dense internal structure that provides high gas selectivity. MWCNTs particles evenly distributed among the Am-PAFEK membrane due to the non-covalent bond interaction between the amino and carboxyl group. Efficient CO2 transport pathways were constructed by homogeneous dispersion of MWCNTs with in MMMs, leading to maintained good selectivity and enhanced permeability. When the amount of carbon nanotubes added was 3 wt.%, that increased by above 60% in comparison to the Am-PAFEK membrane permeability, the CO2/CH4 and CO2/N2 selectivity of the Am-PAFEK/MWCNTs-3% membrane achieved 35.02 and 30.09, respectively. Therefore, the strategy of blending MWCNTs with Am-PAFEK exhibited a promising approach for improving gas permeability.

Surface Engineering on Nickel-Ruthenium Nanoalloys Attached Defective Carbon Sites as Superior Bifunctional Electrocatalysts for Overall Water Splitting.

Herein, we report a novel catalyst of nickel-ruthenium alloy nanoparticles (NPs) homogeneously enriched in the wall of multiwalled carbon nanotubes (denoted as NiRu@MWCNTs) via a facile plasma reduction method. The NiRu@MWCNTs exhibits remarkable electrocatalytic activity and stability for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The required overpotentials to drive a current density of 10 mA cm-2 (η10) over NiRu@MWCNTs are only 14 and 240 mV, corresponding to Tafel slopes of 32 and 55 mV dec-1 for the HER and OER in alkaline medium, respectively. Furthermore, the NiRu@MWCNTs electrolyzer shows low η10 of 330, 380, and 280 mV in acidic, neutral, and alkaline media, respectively. Density functional theory (DFT) calculations and experimental results reveal that the NiRu alloy NPs attached to the defective and nondefective carbon are the key active sites for the HER and OER, respectively, thus resulting in superior isolated synergistic bifunctional active sites for overall water splitting. Our work provides a promising strategy for efficient synthesis of robust catalysts with specific bifunctional active sites for overall water splitting in a wide pH range, along with deep insight into the catalytic mechanism.

Flame retardancy of epoxy resin nanocomposite with a novel polymeric nanoflame retardant

A wrapped nanoflame retardant, designated as polyhedral oligomeric silsesquioxane (POSS)‐poly(4‐bromostyrene) (PBS)‐carbon nanotubes (CNTs), was synthesized via π‐π stacking interactions between the walls of multiwalled carbon nanotubes and the silicon‐bromine containing hybrid copolymer (designated as POSS‐PBS) that was copolymerized by 4‐bromostyrene and acryloyloxyisobutyl polyhedral oligomeric silsesquioxane. The POSS‐PBS‐CNTs exhibited good dispersibility in epoxy resin (EP) without obvious aggregation. Furthermore, the fire behaviors of this flame‐retardant EP (FR‐EP) nanocomposites were examined via limited oxygen index (LOI) and cone calorimeter (CONE) tests. The FR‐EP had an ideal LOI value of 35.3% and its residual char yield obtained from CONE test was significantly enhanced from 5.9% to 15.3% with the incorporation of 4 wt% POSS‐PBS‐CNTs and 1.33 wt% Sb2O3 into EP matrix. Additionally, the addition of 4 wt% POSS‐PBS‐CNTs or POSS‐PBS can efficiently decrease the peak heat release rate (PHRR) of EP matrix by 41.0% or 45.6%, respectively.

Synthesis of Gold Nanoparticles Decorated with Multiwalled Carbon Nanotubes (Au-MWCNTs) via Cysteaminium Chloride Functionalization

Gold nanoparticles (AuNPs) decorated CNTs are promising materials for photocatalytics and biosensors. However, the synthesis of AuNPs chemically linked to the walls of MWCNTs is challenging and toxic products such as thionylchloride (SOCl2) or [1-ethyl-3(dimethyl-amino) propyl] carbodiimide hydrochloride (EDAC) need to be used. This work reports a new approach to prepare gold nanoparticles decorated multiwalled carbon nanotubes (MWCNTs) by using cysteaminium chloride via the formation of a Zwitterionic acide-base bond. The grafting process consists of 3 mains steps: oxidation, thiolation and decoration of AuNPs on the surface of MWCNTs. The completion of each step has been verified out by both spectroscopic (Raman, UV-Vis, FT-IR) and Scanning Electron Miscroscopy (SEM). The chemical bonding states of synthesized products have been proven by X-ray photoelectron spectroscopy (XPS).

Modification of carbon nanotubes by an ion beam of argon

By Scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy has been studied the effect of an argon ion beam with energy of 5 keV and various fluences (1·1016 and 5·1016 ion/cm2) on the morphology, structure, and chemical state of multi-walled carbon nanotubes (MWCNTs). It has been established that irradiation of MWCNTs with argon ions leads to the formation of structural defects and functional oxygen-containing groups of various types (hydroxyl, carboxyl / carbonyl, ether, etc.). It is shown that an increase in the fluence of the beam leads to an increase in the number of functional groups fixed on the walls of the MWCNTs, without changing the types of oxygen-containing groups. It is shown that modification by ion-beam action is promising for increasing the chemical activity and changing the electronic properties of the outer walls of MWCNTs.

The Structure and Electrophysical Properties of Multiwall Carbon Nanotubes Subjected to Argon Ion Bombardment

The morphology, structure, and electrophysical characteristics of multiwall carbon nanotubes (MWCNTs), as affected by defects induced by ion bombardment, are studied using Raman spectroscopy and scanning and transmission electron microscopies. Annealing in an inert atmosphere results in partial recovery of the nanotube structure: the nanotube walls contain regions of recovered graphene structure and regions plagued with extended defects that result in corrugation of graphene layers comprising the walls of MWCNTs. These structural alterations result in a marked decrease in conductivity of the processed MWCNTs.

Структура и электрофизические свойства многостенных углеродных нанотрубок, подвергнутых облучению ионами аргона

AbstractThe morphology, structure, and electrophysical characteristics of multiwall carbon nanotubes (MWCNTs), as affected by defects induced by ion bombardment, are studied using Raman spectroscopy and scanning and transmission electron microscopies. Annealing in an inert atmosphere results in partial recovery of the nanotube structure: the nanotube walls contain regions of recovered graphene structure and regions plagued with extended defects that result in corrugation of graphene layers comprising the walls of MWCNTs. These structural alterations result in a marked decrease in conductivity of the processed MWCNTs.

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

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

Molecular modeling investigation on mechanism of phenol removal from aqueous media by single- and multi-walled carbon nanotubes

In this work, results of molecular and quantum chemical modeling are reported for the mechanism of phenol removal by single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs). First, the lowest energy sites of SWNTs and MWNTs were investigated using quantum mechanics/molecular mechanics methods by utilization Adsorption site locator module of Material Studio software. Then, the equilibrium adsorption capacities of SWNT and MWNTs (with 2 up to 19 walls) were calculated using the conductor-like screening models with segmented activity coefficients (COSMO-SAC) model following the local pseudo-thermodynamic equilibrium at the interface of carbon nanotubes and phenol-containing effluent. It was revealed that the MWNTs with 12 walls are mainly responsible for phenol removal as higher and better interactions were obtained which is coherent with a major probability of these MWNTs. In addition, the removal mechanism in SWNTs was found to be entirely physical trapping within the SWNT walls, while in MWNTs a combination of lateral surface adsorption and negligible physical trapping within MWNT walls was found as both the inner diameter and distance (gap) between walls are smaller than the size of phenol molecules. The contribution of adsorption onto the lateral surface increases as the number of walls increases while the contribution of physical trapping fades. The equilibrium adsorption capacity was calculated for phenol/water loading fractions of 0.01–0.33. Correlation of equilibrium adsorption capacities and phenol concentrations resulted in relationships as lnqe = 0.464 × ln Ce + 0.9596 and lnqe = 0.4979 × ln Ce + 0.9696, respectively for SWNTs and MWNTs from water effluents containing phenol of Ce concentration with regression value R2 > 0.99.

Electron irradiation induced wall-to-wall joining of multiwalled carbon nanotubes

In present work, wall-to-wall joining of two parallel multiwalled carbon nanotubes (MWCNTs) has been successfully demonstrated using electron beam inside high resolution transmission electron microscope. The used MWCNTs have been grown using cobaltocene and benzene as catalyst and carbon precursor, respectively via thermal CVD technique. We have proposed that in present case, irradiation induced joining is achieved if adequate balance between sputtered carbon atoms from the outer walls of MWCNTs and generation as well as migration of defects along the tube axis is obtained. Casimir effect is not found to play dominating role in the joining process. The proposed method can potentially be used for developing wall-to-wall interconnection between MWCNTs using electron beam.