Surface Modification Of Multi-walled Carbon Nanotubes Research Articles

Surface Modification of Multi-Walled Carbon Nanotubes with Polysaccharides

Multi-walled carbon nanotubes (MWCNTs) are known as efficient drug carriers. To improve their interaction with other materials, surface modification of MWCNTs is necessary. In this work, MWCNTs were functionalized with acid and polysaccharides (chitosan and gelatin). The functionalization process was done via modification with acid solutions of nitric acid, sulfuric acid, and a mixture of nitric acid-sulfuric acid first, followed by functionalization with chitosan and gelatin. To achieve the optimum condition of MWCNTs functionalization, the reaction time, temperature, and acid ratio were varied. Furthermore, the effect of chitosan and gelatin addition into MWCNTs was studied at various mass ratios. The synthesized materials were characterized by Fourier transform infrared spectrophotometer, Boehm titration, and dispersion test. The Boehm titration results showed that the acid functional groups had been attached successfully to MWCNTs surface. The amount of acid functional groups increased along with reaction time. The highest amount of acidic group obtained from the data was 2.33 mmol/g. It was achieved when MWCNTs reacted with nitric acid for 24 hours. Temperature and acid ratio variations on the MWCNTs functionalization did not provide significant results. From the FTIR data, sharp peaks at 3480 cm-1 and 1040 cm-1 indicates a -CONH bond, which shows that chitosan and gelatin have been successfully grafted onto MWCNTs surface via an amide linkage. Moreover, the dispersion test showed that the functionalized materials were stable for 48 hours.

Green Synthesis, Characterization, and Catalytic Activity of Amine-multiwalled Carbon Nanotube for Biodiesel Production

An amine-functionalized multiwalled carbon nanotube (MWCNT) was prepared for use as a basic heterogeneous catalyst for the conversion of Cocos nucifera (coconut) oil and Hibiscus cannabinus (kenaf) oil to biodiesel. The 3-aminopropyltrimethoxysilane (3-APTMS) was chosen to form an amine-reactive surface to bind with hydroxyl (−OH) and carboxyl (−COOH) groups of oxidized MWCNT. Silanization took place using a green surface modification method in which supercritical carbon dioxide fluid was utilized under the following conditions: 55 °C, 9 MPa, and 1 h. The synthesized catalyst was characterized using Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), Field emission scanning electron microscopy–energy dispersive x-ray (FESEM-EDX), Time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray powder diffraction (XRD), and Brunauer–Emmett-Teller (BET). Transesterification of coconut oil using 10 wt% NH2-MWCNT catalyst (3 wt% APTMS), 12:1 molar ratio of methanol and oil at 63 °C for 1 h resulted in a >95% conversion. On the other hand, the same catalyst was used in the transesterification of kenaf oil, and formation of ammonium carboxylated salt was observed. The effects of temperature, pressure, and silane concentration on surface modification of MWCNT were evaluated in terms of the catalyst’s basic site density and fatty acid methyl ester conversion. The results indicate that reaction temperature and silane concentration had the most significant effects. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Influence of ratio of multi-walled carbon nanotubes and graphene on microstructure and mechanical properties of copper-graphite composites fabricated by spark plasma sintering

ABSTRACT Copper-graphite composites synergetic reinforced by nano-carbon (multi-walled carbon nanotubes (MWCNTs), graphene nanoplatelets (GNPs)) and ceramic particle reinforced phases (Al2O3 particles and hexagonal boron nitride (HBN)) with alloying elements were fabricated through Spark Plasma Sintering for friction material. The surface modification of MWCNTs and GNPs treated with gallic acid and rutin solutions with ultrasonic treatment can improve the dispersibility. The interfacial bonding between the matrix and the reinforcing phase in the composites was mainly mechanical, and the diffusion layer can be observed. The content of MWCNTs and GNPs remained 1 wt.%; as the proportion of MWCNTs increased, the mechanical properties of nano-carbon and ceramic particles reinforced Cu-graphite composites gradually increased. With the content of 0.8 wt.%MWCNTs-0.2 wt.%GNPs, the composites had the best performance, and the relative density, hardness and compressive strength were 96.01%, 42.75 HV and 202.37 MPa, respectively. According to the morphology of compression fracture, the fracture type was a brittle fracture. It can be determined that the strengthening mechanisms of the composites were mainly load transfer, particle strengthening and fine grain strengthening.

Preparation and Electrical Properties of Silicone Composite Films Based on Silver Nanoparticle Decorated Multi-Walled Carbon Nanotubes.

The electrical properties of silicone composite films filled with silver (Ag) nanoparticle-decorated multi-walled carbon nanotubes (MWNT) prepared by solution processing are investigated. Pristine MWNT is oxidized and converted to the acyl chloride-functionalized MWNT using thionyl chloride, which is subsequently reacted with amine-terminated poly(dimethylsiloxane) (APDMS). Thereafter, APDMS-modified MWNT are decorated with Ag nanoparticles and then reacted with a poly(dimethylsiloxane) solution to form Ag-decorated MWNT silicone (Ag-decorated MWNT-APDMS/Silicone) composite. The morphological differences of the silicone composites containing Ag-decorated MWNT and APDMS-modified MWNT are observed by transmission electron microscopy (TEM) and the surface conductivities are measured by the four-probe method. Ag-decorated MWNT-APDMS/Silicone composite films show higher surface electrical conductivity than MWNT/silicone composite films. This shows that the electrical properties of Ag-decorated MWNT-APDMS/silicone composite films can be improved by the surface modification of MWNT with APDMS and Ag nanoparticles, thereby expanding their applications.

Surface modification of MWCNT with cluster form of Fe2O3/Fe3O4 NPs for improving their microwave absorption performance

The Fe2O3/Fe3O4 nanoparticles (NPs) decorated on multi-walled carbon nanotubes (MWCNTs) by a three-step synthesis method as the following: (1) Fe2O3 was produced in polyethylene glycol (PEG) matrix; (2) PEG-Fe2O3 NPs covered with Fe3O4 to obtain Fe2O3/Fe3O4 NPs; (3) MWCNTs decorated by an optimum weight ratio of the Fe2O3/Fe3O4 NPs. The produced Fe2O3/Fe3O4/MWCNT nanocomposite, in which the clusters of Fe2O3/Fe3O4 NPs decorated on the MWCNT’s surface, exhibits an excellent absorption performance and a broad effective bandwidth. The strongest reflection loss and the broadest bandwidth reached to −72.17 dB and 8.80 GHz for 2.8 mm and 2.4 mm matching thicknesses, respectively.

Modified multi-walled carbon nanotubes assisted foam fractionation for effective removal of acid orange 7 from the dyestuff wastewater

In this study, multi-walled carbon nanotubes (MWCNTs) had been used to strengthen the removal of acid orange 7 (AO7) from the dyestuff wastewater by using foam fractionation. First, the surface modification of MWCNTs was performed by introducing hypochlorite groups (-OCl). The modified MWCNTs were characterized by using SEM, XRD, FTIR and Raman spectroscopy. Subsequently, the potential of modified MWCNTs as a novel collector for AO7 adsorption was examined. The adsorption conditions of modified MWCNTs towards AO7 were optimized by using response surface methodology (RSM) with a central composite design (CCD). The adsorption capacity of modified MWCNTs towards AO7 could reach 47.72 ± 0.79 mg·g−1 under the optimum conditions. The kinetics and the equilibrium adsorption data were analyzed by using different kinetic and isotherm models. According to the regression results, adsorption kinetics data were well described by pseudo-second order model, whereas adsorption isotherm data were best represented by Langmuir isotherm model. Finally, foam fractionation was performed with a batch mode. Under the suitable conditions of loading liquid volume 300 mL, modified MWCNTs dosage 180 mg, cetyltrimethylammonium bromide (CTAB) concentration 50 mg·L−1, AO7 concentration 30 mg·L−1, pore diameter of gas distributor 0.125 mm and air flow rate 100 mL·min−1, the removal percentage and enrichment ratio of AO7 were 91.23% and 6.17, respectively. The decolourization ratio of solution after foam fractionation was found to be 98.66%.

Mechanical and piezo‐resistive properties of functionalized multi‐walled carbon nanotubes/styrene‐ethylene‐butadiene‐styrene composites

AbstractCarbon nanotube, owing to its excellent mechanical and electrical properties, is promising to be used in polymer composites towards both structural and functional applications. In this paper, one type of multi‐walled carbon nanotubes (MWNTs)/polystyrene‐b‐(ethylene‐co‐butylene)‐b‐polystyrene (SEBS) composite was fabricated. MWNTs were first surface functionalized with SEBS before blended with polymer matrix. The surface modification of MWNTs was characterized by various techniques including X‐ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis (TGA). Results indicated that MAH (maleic anhydride)‐g‐SEBS was successfully grafted onto MWNTs with grafting ratio 8.7 wt%. The SEBS composites containing functionalized MWNTs exhibited excellent mechanical and electrical properties, evidenced by tensile and electrical properties tests, owing to enhanced interfacial interaction between the SEBS‐g‐MWNTs and the SEBS matrix. SEBS‐g‐MWNTs/SEBS was also explored in terms of piezoresistivity. The composites exhibited excellent piezoresistivity after the percolation threshold (1.0 wt%) and good repeatability during multiple cycles. The rubbery behavior coupled with electrical properties make this type of composite promising in advanced soft electronics.

Surface modification of carbon nanotube: Effects on pulsating heat pipe heat transfer

The role of new nanofluid based on multi-walled carbon nanotube (MWCNT) on the heat transfer efficiency of a closed loop pulsating heat pipe (CLPHP) has been investigated in this research. For this purpose, surface modification of MWCNT was utilized to prepare uniform and stable nanofluids. Therefore, chemical surface modification and polymer wrapping treatment were conducted on the nanotubes, and then, the thermal conductivity of synthesized nanofluids was measured to investigate the effect of these Nano complexes on the thermal resistance of CLPHP system. In addition, the effect of other CLPHP parameters such as filling ratio, operating pressure and different working fluids were investigated. The results revealed that these nanofluids could enhance the heat transfer coefficient (HTC) of the system by up to 27% when they used as the working fluid in a CLPHP. Furthermore, these experiments indicated that the CLPHP increased the HTC by up to 30% compared to a copper fin that is known for its higher HTC among the metals.

Surface Modification of MWCNTs with Carboxylic-to-Amine and Their Superb Adsorption Performance

In this study, multi-walled carbon nanotubes (MWCNT) surface functionalization with amine group is studied for methyl orange (MO) dye removal from aqueous solution. The adsorbent was prepared using 1,2-ethylenediamine as amine via a microwave combination to functionalize the carbon nanotubes with carboxylic acid (–COOH) then converting to acyl chloride (–COCl) as intermediate using thionyl chloride. The prepared material shows a suburb adsorption performance of MO removal with a high adsorption capacity of 96 mg g−1. In addition, the equilibrium data are introduced by the Langmuir and Freundlich isotherms, and showed Langmuir is the best fit with the adsorption capacity of 25.73 mg g−1. Moreover, pseudo-second order is found to be the best kinetic model to fit the experimental data. According to kinetics results, the adsorption process involves chemisorption step. MWCNT–NH2 is an excellent candidate to be used as an effective adsorbent for pollution removal from the aqueous environment.

Influence of different functionalization methods of multi-walled carbon nanotubes on the properties of poly(L-lactide) based nanocomposites

This paper presents influence of the type of carbon nanotube functionalization on properties of poly(L-lactide) (PLLA) based nanocomposite materials. For this purpose surface modifications of multi-walled carbon nanotubes (MWCNTs) were performed by chemical and irradiation techniques, while thermo gravimetric analysis, UV-Visible and Fourier-transform infrared (FT-IR) spectroscopies confirmed successful covalent functionalization. Series of PLLA bionanocom-posites with different contents of functionalized MWCNTs (0.7; 1.6; 2.1 wt%), were synthesized via ring-opening solution polymerisation of L-lactide. FT-IR analysis confirmed that grafting of L-lactide, under controlled condition, is possible to perform starting from the surface of functionalized MWCNTs. From differential scanning calorimetry results it was concluded that even low contents of chemically and irradiation functionalized MWCNTs had a significant effect on thermal properties of the prepared nanocomposites, raising the values of melting and glass transition temperatures. Thermogravimetric analysis (TGA) has shown that the degradation onset temperature for composites with chemically functionalized MWCNTs, was much higher than that for the neat poly(L-lactide) sample and composites with irradiation functionalized MWCNTs. Morphology studies by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that poly(L-lactide) covered surfaces and separated functionalized MWCNTs. Good dispersion of carbon nanotubes in polymer matrix enabled conductivity of synthesized materials, as determined by conductivity tests.

A Study of Effects of Different Surface Modifications of MWCNTs on their Adsorption Capacity of Benzene and Toluene

Multi-Walled Carbon Nanotubes (MWCNTs) surfaces were serially modified by the annealing treatment under Helium flow at 1000oC, the nitric acid treatment and again the annealing treatment under same conditions and their maximum adsorption capacities for benzene and toluene were measured and analyzed. The unmodified and modified MWCNTs werecharacterized by Fourier Transform InfraRed (FT-IR) and Raman spectroscopy techniques and Brunauer–Emmett–Teller (BET) specific surface area measurements. The results revealed that the nitric acid treatment leads to form the functional groups and defects on the MWCNTs surfaces and increase their specific surface areas while the annealing treatments remove the functional groups and defects and therefore improve the structural integrity of the MWCNTs and enhance the p-p ­interaction between the MWCNTs and the toluene/benzene. According to the measurements of the maximum adsorption capacities, both acid and annealing treatments increased the adsorption capacity of the MWCNTs for both the benzene and toluene. It can be finally concluded that the adsorption capacity of the carbon nanotubes for the aromatic organic adsorbates such as benzene and toluene not only depends on their specific surface area but also is influenced by the structural integrity of the carbon nanotubes.

Honeycomb structured porous films prepared from arborescent graft polystyrenes via the breath figures method

Highly ordered honeycomb films were produced from arborescent graft polystyrene (AGPS) solutions using breath figures (BF). The structure of the BF pattern (whether single layered or multilayered) of pores depended on several factors such as the type of solvent used (CS2 or CHCl3), the length of the side chains, the generation number and the concentration of the polymer. When solutions of AGPS with shorter side chains (Mw ∼ 5000 g/mol) were used for the BF process, arborescent polymers generated a multilayer pore structure. However, when polymers with longer side chains (Mw ∼ 30,000 g/mol) were used, monolayer pore structures were mostly generated. The regularity and surface quality of the honeycomb pattern became worsened as the multilayered structures formed. The polymer concentration (ϕ) also played a critical role in determining the morphology of the BF films. Higher ϕ led to a multilayer pore structure while lower ϕ resulted in a monolayer pore structure. In general, the regularity of top layer pores was found to decrease with increasing generation number. The introduction of multiwall carbon nanotubes (MWCNTs) into AGPS solutions and application of the BF process using the solution blends yielded patterned hybrid films. SEM images showed that some CNTs were loaded into the honeycomb pattern of AGPS, but that most MWCNTs precipitated to form the bottom layer. In this work, the influence of concentration and surface modification of MWCNTs on the BF patterns obtained is discussed.

Aramid–multiwalled carbon nanotube nanocomposites: effect of compatibilization through oligomer wrapping of the nanotubes

AbstractAramid–multiwalled carbon nanotube (MWCNT) nanocomposites with different CNT loadings were prepared by the solution‐blending technique. Aramid oligomeric chains having reactive amine end‐groups were covalently grafted and wrapped over the surface of acid‐functionalized MWCNTs. The presence of functional groups and surface modification of MWCNTs were studied using Raman, Fourier transform infrared and X‐ray photoelectron spectroscopic and transmission/scanning electron microscopic techniques. Addition of these MWCNTs resulted in a homogeneous dispersion throughout the aramid matrix. Dynamic mechanical thermal analysis showed an increase in the storage modulus and the glass transition temperature involved with α‐relaxations on CNT loading. The coefficient of thermal expansion (CTE) of aramid was reduced on loading with such CNTs. Strong interfacial interactions of the matrix with the surface‐modified CNTs reduced the stress‐transfer problem in the composite material and resulted in higher modulus of 4.26 GPa and a glass transition temperature of 338.5 °C, whereas the CTE was reduced to 101.8 ppm °C−1 on addition of only 2.5 wt% CNTs in the aramid matrix. © 2016 Society of Chemical Industry

Effect of surface modification on multi-walled carbon nanotubes for catalytic oxidative dehydrogenation using CO2 as oxidant

Multi-walled carbon nanotubes (MWCNTs) with surface modification are prepared by the introduction of different oxygenated groups and metal oxides. It is found that surface modification of MWCNTs can induce significant changes in Raman feature, redox capability and catalytic dehydrogenation performance of these MWCNT composites. Since oxygenated groups with lone electron pairs or carbon–oxygen double bond can form the conjugated structure with sp2-bonding surface carbon on MWCNTs and partially compensate the sp2 hybridized structure of their surface carbon, surface modification only with oxygenated groups for MWCNTs has a small influence of electronic structure state of surface carbon and show no obvious shift of Raman bands and similar high reduction temperature of MWCNTs except Raman intensity ratio and reductive peak area of MWCNTs. The catalytic dehydrogenation performance of these MWCNTs with surface modification is not determined by itself reactivity of surface carbon but the type of functional groups on surface carbon and the hydroxylation of MWCNTs, especially MWCNTs with artificial defects, are used to produce efficient active sites for dehydrogenation reaction to enhance their catalytic activities. Surface modification of CeO2 nanoparticles for MWCNTs can change characteristic Raman band and reduction capability of MWCNTs and CeO2 due to the presence of strong interaction and charge transfer between MWCNTs and CeO2. Simultaneously, π-electron deficient inner surface of MWCNTs can strongly interact with CeO2 to promote the further activation of CeO2. Therefore, CeO2-MWCNTs composites show the increased catalytic activities due to surface modification with CeO2 nanoparticles. Noticeably, CeO2 nanoparticles decorated on inner surface of MWCNT channels show higher catalytic efficiency than that on their outer surface.

Rheological properties of epoxy/MWCNT suspensions associated with the surface modification of MWCNT by physisorption of aromatic ionic salts

The multi-walled carbon nanotubes (MWCNTs) physisorbed by aromatic ionic salts such as 10-methyl-acridinium iodide (MAcI) were found to well disperse in diglycidyl ether of bisphenol-A epoxy resin. As they were subjected to the rheological study at 30 °C, the gelation of epoxy/MWCNT-MAcI suspension occurred at 0.75 wt% MWCNT-MAcI, which was less than that using pristine MWCNT. As to the viscosity measurements, the dilation effect that the viscosity of epoxy/MWCNT suspension increases with shear rate was found and more pronounced by incorporating MWCNT-MAcI. According to the Thomas-modified Einstein viscosity equation, the dilation effect was attributed to the excess amount of epoxy resin trapping in the aggregated domain of MWCNT. By increasing the shear rate to a certain point, the shear thinning effect that the viscosity decreases with shear rate was also observed. Interestingly, the transition point that the dilation effect changes to shear thinning effect shifted to lower shear rate as the content of MWCNT increased and/or MWCNT-MAcI was incorporated. Notably, better dispersion and less aggregated domains for the suspensions with MWCNT-MAcI compared to pristine MWCNT were further supported by small angle x-ray scattering and transmission electron microscopy.

Formation of homogenous copper film on MWCNTs by an efficient electroless deposition process

Abstract In this study, copper-coated multi-walled carbon nanotubes (MWCNTs) were prepared using electroless deposition process with an efficient bath composition. As-received MWCNTs underwent acid treatment and subsequent sensitization with tin and activation with palladium before the copper coating process. The electroless deposition process was performed in a bath, which contained copper sulphate pentahydrate as a copper precursor, potassium sodium tartrate as a complexing agent, and formaldehyde as a reducing agent. Surface modifications of MWCNTs were studied by Fourier transform infrared spectroscopy, imaging techniques (scanning electron microscopy, transmission electron microscopy), and X-ray diffraction. On the basis of the results, it was observed that the coating layer covers most surfaces of the nanotubes. Furthermore, copper oxide is also deposited on the surfaces of MWCNTs. The total amount of metals after each sensitization, activation, and metallization step was determined by thermo gravimetric method and induced coupled plasma atomic emission spectroscopy. Coating of MWCNTs was accomplished successfully through adjusting proper chemical ratios and concentrations. The calculated bath efficiency was about 99%.

Surface modification of MWCNTs with glucose and their utilization for the production of environmentally friendly nanocomposites using biodegradable poly(amide‐imide) based on N‐trimellitylimido‐S‐valine matrix

In the present investigation, the preparation, characterization, and surface morphology of poly(amide‐imide) (PAI)/multi‐walled carbon nanotubes (MWCNTs) bionanocomposites (BNCs) were the main goals of the study. At first, an optically active PAI based on S‐valine as a biodegradable segment was synthesized. Then, carboxyl‐modified MWCNTs were functionalized with glucose (f‐MWCNT) as a biological active molecule in a green method to achieve a fine dispersion of f‐MWCNT bundles in the PAI matrix. The existence of S‐valine in the PAI matrix and functionalized MWCNT with glucose resulted in a series of potentially biodegradable nanocomposites. The obtained BNCs were characterized by various techniques. Field emission scanning and transmission electron microscopy micrographs of the composites showed a fine dispersion of f‐MWCNTs in the polymer matrix because of hydrogen bonding and π–π stacking interaction between f‐MWCNTs and polymer functional groups and aromatic moieties. Adding f‐MWCNTs into polymer matrix significantly improved the thermal stability of BNCs because of the increased interfacial interaction between the PAI matrix and f‐MWCNTs and also good dispersion of f‐MWCNT in the polymer matrix. Copyright © 2015 John Wiley & Sons, Ltd.

Role of oxidant in surface modification of carbon nanotubes for tyrosinase immobilization

Studies on the development of interface between biological molecules and novel nanomaterials have attracted research worldwide. Carbon nanotubes(CNTs) have become an important matrix for the fabrication of biomaterials due to its unique properties. Surface properties of the CNTs and the medium of immobilization are critical in the immobilization of biological molecules such as enzymes. In this study surface modification of multi-walled carbon nanotubes (MWCNTs) for carboxylic moieties attachment was accomplished by acid treatment and reaction with potassium permanganate. The effect of these two oxidants on the surface modification of MWCNTs for the purpose Tyrosinase immobilization was studied. Commercial MWCNTs were treated with either concentrated sulfuric acid and nitric acid mixture with ratio 3:1 or with 0.1 M potassium permanganate via reflux, stirring and ultrasonication. The resulting surface modified MWCNTs were characterized with FT-IR spectrophotometer, FESEM, and TGA analyzer. The immobilized Tyrosinase was tested for leaching assay. The FTIR spectra of functionalized MWCNTs showed a significant peak in the range of 1700 cm- 1 to 1729 cm-1 indicating the presence of carboxyl double bond, which confirmed the successful functionalization of MWCNTs by chemical oxidation. The carboxylic peak of MWCNTs treated with KMnO4- showed higher intensity as compared to acid-treated MWCNTs. The acid-treated MWCNTs displayed a sparkling crystalline-like particles while the KMnO4-modified MWCNTs consists of smooth powdery particles. Both treated MWCNTs also showed good dispersion in aqueous solution with different amount of acidic and basic site present.

Effect of p-type multi-walled carbon nanotubes for improving hydrogen storage behaviors

In this study, the hydrogen storage behaviors of p-type multi-walled carbon nanotubes (MWNTs) were investigated through the surface modification of MWNTs by immersing them in sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) at various ratios. The presence of acceptor-functional groups on the p-type MWNT surfaces was confirmed by X-ray photoelectron spectroscopy. Measurement of the zeta-potential determined the surface charge transfer and dispersion of the p-type MWMTs, and the hydrogen storage capacity was evaluated at 77K and 1bar. From the results obtained, it was found that acceptor-functional groups were introduced onto the MWNT surfaces, and the dispersion of MWNTs could be improved depending on the acid-mixed treatment conditions. The hydrogen storage was increased by acid-mixed treatments of up to 0.36wt% in the p-type MWNTs, compared with 0.18wt% in the As-received MWNTs. Consequently, the hydrogen storage capacities were greatly influenced by the acceptor-functional groups of p-type MWNT surfaces, resulting in increased electron acceptor–donor interaction at the interfaces.

Surface modification of MWCNTs by O2 plasma treatment and its exposure time dependent analysis by SEM, TEM and vibrational spectroscopy

In this paper, we report the efficient surface modification of multiwall carbon nanotubes (MWCNTs) by oxygen (O2) plasma treatment while in situ monitoring of its sidewall surface degradation as a function of plasma exposure time. The nanostructure and surface morphology of pre- and post plasma treated CNTs were investigated by using Field Emission Electron microscopy (FESEM), High resolution Transmission Electron microscopy (HRTEM), and Raman spectroscopy (RS). A systematic study was carried out by FTIR and surface energy measurements on the analysis of functional groups attached on the CNTs surface leading to the transformation of surface nature from hydrophobic to hydrophilic with the increase of plasma treatment time. The results confirmed that O2 plasma treatment time greatly enhanced oxygen content on CNTs surface, and modified structural properties while inducing more surface damages and defects. Surface defects are sometimes desirable for sensing purpose and it is shown that the extent of defect generation can be easily tuned with the plasma exposure time without damaging the integrity of the nanotubes pattern.