Functionalization Of Multi-walled Carbon Nanotubes Research Articles

Impedimetric Sensor for Pentoses Based on Electrodeposited Carbon Nanotubes and Molecularly Imprinted poly-o-phenylenediamine

Impedimetric D-Xylose and D-Arabinose sensors was development from composite electrodes of graphite and histological paraffin, modified with functionalized multi-walled carbon nanotubes (FMWCNTs) based on molecular imprinted poly-o-phenylenediamine (poly-o-PD). The contribution of this work was not only the development of a D-xylose and D-Arabinose MIP impedimetric sensor with good performance, but also the electrodeposition method for FMWCNTs onto surface of graphite composites electrodes with ease of control and reproducibility of the electrodeposition process. The sensors were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), field emission gun scanning electron microscopy (FEG-SEM) and RAMAN spectroscopy. The MIPs sensors for the pentoses have good selectivity, sensitivity in the concentration range of 1.0 × 10−11 to 1.0 × 10−10 mol l−1 with limit of detection (LOD) of 4.50 × 10−12 mol l−1 for D-Xylose and 4.25 × 10−12 mol l−1 for D-Arabinose. MIPs was applied to determination of pentoses in samples of sugarcane bagasse hydrolysates using the standard addition method and validated by recovery study, which presented satisfactory results between 92.9% and 115.5%.

Effect of Reaction Time on Modification of Multi-walled Carbon Nanotubes with HNO3

The functionalization of Multi-walled Carbon Nanotubes (MWCNTs) is addressed to improve its interaction capability with other materials for further applications. The oxidation of MWCNTs by nitric acid is one of the promising methods for its surface modifications. In this research, MWCNTs functionalization was carried out in several steps such as oxidation, filtration, washing, and drying. The optimization of reaction time for MWCNTs functionalization was conducted to achieve the optimum condition which efficiently functionalizes MWCNTs surface. The sample characterizations were investigated by Boehm titration, Fourier Transform Infrared (FTIR) Spectroscopy, Thermo Gravimetric Analysis (TGA), and dispersion test. As a result, carboxyl groups were successfully attached onto the MWCNTs surface and stable dispersion of MWCNTs was obtained after 12 hours. Oxidation with nitric acid for 12 hours at room temperature is the optimum treatment time for surface modification.

Aldehyde functionalized multiwalled carbon nanotubes to synthesize highly conducting polyaniline-MWNT thin films

Polyaniline (PANI) and its composites with other materials gains great attraction in the field of conducting polymers as their properties can be easily tuned to the desired level. Multiwalled Carbon nanotubes (MWNT) are such a promising material to make composites with PANI. Presence of MWNT in PANI composite enhances its conductivity and makes the composite thermally stable. But dispersivity of PANI-MWNT composite in solvents is very low while preparing thin film samples. To improve the solubility and processability of PANI-MWNT composite, MWNT has to be modified by attaching suitable functional groups to the side walls of carbon nanotubes without changing the composition of nanotubes. The functionalization of multi-walled carbon nanotubes was carried out using HCl treated MWNTs. MWNTs were reacted with formaldehyde and attached into methylol groups (–CH2OH). The presence of methylol group makes the carbon nanotubes more lyophilic than the pristine form and improves the processability of MWNTs and MWNT containing composites. Structural characterization is carried out by X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) techniques. Electrical characterization of the samples were carried using standard four point probe method. Pristine MWNT shows flat temperature response of DC electrical conductivity. The room temperature conductivity of pristine MWNT, PANI and PANI-MWNT composites are 9.5 S/cm, 2.27 S/cm and 11.8 S/cm respectively. In the present work, we have achieved significant dispersivity of PANI-MWNT composites as a result of the functionalization and the thin film sample shows electrical conductivity of 565.44 S/cm which is very high for conducting polymer composites. These composites show metallic character and its temperature coefficient of resistance (α) is found to be 0.0038 °C−1, which is less than that of copper.

Функционализация многостенных углеродных нанотрубок в окислительных средах

Функционализация многостенных углеродных нанотрубок в окислительных средах

Synthesis of Multiwall Carbon Nanotubes by the Cvd Method and their Functionalization

Results of the functionalization of multiwall carbon nanotubes by an aqueous solution of nitric acid and a mixture of nitric and sulfuric acids with subsequent treatment of them by ultrasound are presented. The presence of functional groups on the surface of multiwall carbon nanotubes was determined with the use of IR spectroscopy.

Study on thermal property enhancement of MWCNT based polypropylene (PP) nanocomposites

In this work, Carbon nanotubes with surface treatment and Aluminium Hydroxide (ATH) nanoparticles are incorporated into the polypropylene matrix as Nanofillers to fabricate composites. Thermal properties are investigated by DSC and TGA. Functionalized Multiwall carbon nanotube with ATH nanoaprticles exhibited better thermal properties than individual nanofillers. This nanocomposite should be considered as the new alternative for fire retardant and other thermal properties. Surface treatment of MWCNT (SCNT) is accompanied by using 3 amino propyl tri-ethoxy silanes (APTES). Silanised MWCNT are homogeneously dispersed into the polymer matrix along with ATH. ATH concentration is varied up to 3% for fixed PP with fixed amount of Silanated Carbon Nanotube (SCNT) and the resultant composites were evaluated by DSC and TGA analysis. The results showed that interfacial bonding between Nanofillers, polymer matrix was improved by silane treatment of MWCNT and ATH, degradation rate can significantly be reduced, and thermal stability of polymers can be enhanced without compensating its physical and mechanical properties. Composites consisting of nano-sized inorganic compounds and organic polymers together demonstrating a new class of materials that could exhibit improved performance in all related fields compared to their microparticles counterparts.

An amplified electrochemical sensor employing a polymeric film and graphene quantum dots/multiwall carbon nanotubes in a deep eutectic solvent for sensitive analysis of paracetamol and 4-aminophenol

Herein, a nanocomposite consisting of graphene quantum dots, a deep eutectic solvent and carboxyl functionalized multiwall carbon nanotubes (GQDs + DES + MWCNTs-COOH) was prepared.

Quantum dot embedded N-doped functionalized multiwall carbon nanotubes boost the short-circuit current of Ru(ii) based dye-sensitized solar cells.

Here, we report zinc sulfide quantum dots, ZnS(QDs), moored on N-doped functionalized multiwall carbon nanotubes (MWCNTs) wrapped with reduced graphene oxide (rGO). The MWCNTs have a tangled network, a particular surface area, and a distinctive hollow structure that may be suitable for use as a counter electrode (CE) material. A ZnS@N.f-MWCNTs@rGO composite as the CE on a fluorine-doped tin oxide substrate in a dye-sensitized solar cell (DSSC) was fabricated using a doctor blade technique. The electrochemical performance showed that at the electrolyte/CE interface, the ZnS(QDs) and N-doped functionalized MWCNTs wrapped with rGO (ZnS@N.f-MWCNTs@rGO) electrode has a lower transfer charge resistance (Rct) and a greater catalytic capacity than naked ZnS(QDs). A power conversion efficiency (PCE) of 9.4% was attained for this DSSC gadget, which is higher than that of a DSSC gadget utilizing ZnS(QDs), ZnS@N.f-MWCNTs, ZnS@rGO and Pt. Also, the DSSC device using ZnS@N.f-MWCNTs@rGO had a fill factor (FF) that was better than the other counter electrodes. The cyclic voltammetry and electrochemical impedance spectra (EIS) electron transfer measurements showed that ZnS@N.f-MWCNTs@rGO films can provide fast electron transfer from the electrolyte to the CE and great electrocatalytic activity to reduce triiodide to a CE based on ZnS@N.f-MWCNTs@rGO in the DSSC.

Studies on the effects of different multiwalled carbon nanotube functionalization techniques on the properties of bio-based hybrid non-isocyanate polyurethane.

A novel synthesis method for multiwalled carbon nanotube (MWCNT) modified bio-based hybrid non-isocyanate polyurethane (HNIPU) is proposed in this paper. Modification methods for several properties of MWCNTs–HNIPU were systematically studied. MWCNTs were grafted with carboxyl and amino groups using a condensation reflux device. Au nanoparticles were synthesized on the surface of the MWCNTs via a reduction reaction and Fe3O4 particles were decorated on the MWCNTs using a hydrothermal method. FTIR, TEM, XRD, XPS and Raman techniques were employed to confirm the compositions and structures. Then, five different types of MWCNT were utilized for blending with non-isocyanate polyurethane (NIPU) via solution methods. After curing with epoxy resin E-51, the cross-linked composites were applied as coatings. A series of tests demonstrated that HNIPU composited with MWCNTs–COOH–Au had the highest Tg value, the best thermal, thermodynamic and mechanical properties, and excellent pencil hardness, adhesion, flexibility and impact strength, while HNIPU composited with MWCNTs–COOH–NH2 had the best water absorption and swelling properties. These results showed that the properties of hybrid non-isocyanate polyurethane can be adjusted via different MWCNT surface modification approaches or the addition of nanoparticles, so this kind of polyurethane has a vast development space for coating applications.

Decolorization of Rhodamine B dye by using multiwalled carbon nanotubes/Co\u2013Ti oxides nanocomposite and Co\u2013Ti oxides as photocatalysts

Functionalized multiwalled carbon nanotubes (F-MWCNTs)/Co–Ti oxide nanocomposites and neat Co–Ti oxide nanoparticles were synthesized by chemical reduction method. The scanning electron microscopy micrographs show that the bimetallic NPs in F-MWCNTs/Co–Ti are present in dispersed form while the neat Co–Ti nanoparticles were found in agglomerated form. The formation of nanocomposites and neat Co–Ti nanoparticles was also confirmed by energy-dispersive X-ray. Both types of nanocomposites were employed as photocatalyst for the photodegradation of Rhodamine B in aqueous medium under UV light irradiation. The photodegradation study was performed via UV–Vis spectrophotometer. The photodegradation results show that F-MWCNTs/Co–Ti oxide NPs degraded about 93.35% dye within 150 min irradiation time while the neat Co–Ti oxide NPs degraded about 91.76% dye within same irradiation time. The F-MWCNTs/Co–Ti can be easily removed and recycled due to its bulky composite nature as compared to neat Co–Ti oxide NPs. The effect of dye concentration, catalyst dosage, pH of medium and activity of recycled catalyst was also evaluated.

Switchable fluorescence sensor toward PAT via CA-MWCNTs quenched aptamer-tagged carboxyfluorescein

A quenching based apta-sensing platform was developed for the detection of Patulin. Three different aptamer sequences were studied to screen the aptamer with the maximum affinity towards Patulin. Carboxyfluorescein (CFL) was used as a fluorescent dye while –COOH functionalized multiwall carbon nanotubes (MWCNTs) were applied as novel nanoquenchers. Aptamer tagged at the 3′ end with 40 nucleotide bases exhibited the maximum affinity towards Patulin and caused substantial fluorescence recovery. Interestingly, the limit of detection (LOD) and limit of quantification (LOQ) were calculated as 0.13 μg L−1and 0.41 μg L−1 respectively. Commonly occurring mycotoxins in food were also tested to confirm the selectivity of apta-assay. The developed apta-assay was applied to a spiked apple juice sample and toxin recoveries were observed ranging from 96% to 98% (n = 3). These results demonstrated the potential of the developed apta-assay for the selective detection and quantification of Patulin in food samples.

Facile and efficient synthesis of magnetic fluorescent nanocomposites based on carbon nanotubes

Multifunctional nanomaterials composed of magnetic and fluorescent nanoparticles have been one of the most extensive pursuits because of the potential application in bio-research. In this paper, we demonstrated an efficient method by coupling CdSe/CdS/ZnS quantum dots (QDs) with Fe3O4 magnetic nanoparticles(MNPs) while functionalized multiwall carbon nanotubes (f-MWCNTs) were used as matrix to synthesize a kind of magnetic fluorescent nanocomposite. Compared with other matrix materials, carbon nanotubes have the advantages of high surface areas and good biocompatibility. The incorporation of f-MWCNTs supplies plenty of nucleation sites for the preferential growth of Fe3O4 nanoparticles, avoiding the agglomeration phenomenon of Fe3O4 MNPs in traditional co-precipitation method. Moreover, the un-reacted functional groups of f-MCNTs can further adsorb biological species and drugs, averting the decline of fluorescent intensity caused by the modification of biological species and drugs. The synthetic product maintains the unique properties of rapid magnetic response and efficient fluorescence, which shows a broad application prospect in fluorescent labeling, biological imaging, cell tracking and drug delivery.

Enhanced Strain Sensing Performance of Polymer/Carbon Nanotube‐Coated Spandex Fibers via Noncovalent Interactions

AbstractOver the past decade, flexible strain sensors have been of tremendous interest due to their wide application in robotics, medical diagnostics, human motion detection, and healthcare. Herein, a fiber strain sensor is fabricated by continuously coating a layer of ultrathin multi‐walled carbon nanotube (MWCNT)/thermoplastic polyurethane (TPU) nanocomposites onto the surface of commercial spandex fiber. The effect of noncovalent functionalization of MWCNTs using 1‐pyrenecarboxylic acid (PCA) on the electrical conductivity as well as the sensing performance of the fiber sensor is investigated. The low‐cost strain sensor possesses a large workable strain (up to 200% strain), high sensitivity (gauge factor is 14 191.5 under 170–200% strain), and excellent stability (up to 1000 cycles), and regular signal responses within a wide measuring frequency range of 0.01–1 Hz are achieved with the introduction of PCA via enhanced nanotube dispersion and polymer–nanofiller interactions. Additionally, the resistance response to strain is fitted with a model based on tunneling theory to understand the sensing mechanism, and to prove that the fitted results are in agreement with the experimental results. Furthermore, the developed sensor is successfully applied in human motion detection, such as joint movement, facial microexpressions, and speech recognition.

Silver-decorated multiwall carbon nanotubes: synthesis characterization and application in polymer composite-based devices

The present work reports a novel synthesis procedure to decorate multiwall carbon nanotubes (MWCNTs) by silver (Ag) nanoparticles (NPs) via silver nitrate (AgNO3) followed by incorporation of these decorated MWCNTs into polymers to form the nanocomposite. The samples of functionalized MWCNTs (FMWCNTs), Ag-decorated MWCNTs (Ag-MWCNTs) and polymer/Ag-MWNCT composites were investigated using various characterization techniques. The field-emission scanning electron microscope (FESEM) image of Ag-MWCTs reveals the uniform distribution of Ag nanoparticles over the surface of MWCNTs. Energy-dispersive X-ray spectroscopy (EDX), elemental mapping, X-ray diffraction (XRD) and Raman spectroscopy confirmed the successful formation of Ag-decorated MWCNTs. FESEM images and UV–Vis absorption spectra of polymer/Ag-MWNCTs composites clearly validates the development of polymer/Ag-MWCNT composites. Finally, the polymer/Ag-MWCNT-based devices were fabricated to compare the electrical performance with those comprising the pristine polymers. The 3D conducting pathways formed by MWCNT and extremely high conductivity of Ag contribute to the improved current levels and reduced cut-in voltage in the Ag-MWCNTs compared to the pristine devices. The electrical transport study also shows a significant modification in the dominant transport mechanism by addition of Ag-MWCNT in the polymer matrix. The present study could pave the path for the development of various cost-effective high-performance electronic devices based on Ag-MWCNT/polymer composites.

Functionalization of Multiwalled Carbon Nanotubes using Cold Plasma Treatment and their Electrochemical Performances

Functionalization of Multiwalled Carbon Nanotubes using Cold Plasma Treatment and their Electrochemical Performances

Effect of microwave treatment exposure time on functionalization and purification of multi-walled carbon nanotubes (MWCNTs)

Carbon nanotube (CNT)-reinforced polymer composites are steadily replacing other materials and finding their applications in many structural components. This has been credited to their light weight, ease of processing and extraordinary thermal, mechanical and electrical properties. However, direct addition of CNTs into polymer leads to formation of agglomerates due to strong van der Waals’ force of attraction between individual nanotubes. These agglomerates then act as defects and hinder the properties of polymer/CNT composites. As a result, CNTs are functionalized in acids to minimize their tendency to agglomerate and improve dispersion in polymer matrix. The present study focuses on the microwave treatment of CNTs to achieve better functionalization as compared to the conventional ultra-sonication technique. The time of exposure of multi-walled carbon nanotubes (MWCNT) to the microwave radiation is optimized by investigating the structural integrity of different samples with Raman spectroscopy, infrared spectroscopy (FTIR), microscopy and purification effect by X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS). The mechanism of sidewall modification of MWCNTs after functionalization is elucidated schematically as well.

Fabrication of multiwalled carbon nanotubes/carrageenan-chitosan@ Ce and Sr substituted hydroxyapatite biocomposite coating on titanium: In vivo bone formation evaluations

Mineral substituted hydroxyapatite (MHAp) is one of the most significant bony mineral parts that have been broadly utilized as bony substitution matters as a result of its cytocompatible and bioactive properties. Though, the utilization of hydroxyapatite as bony inserts is confined because of its poor mechanical and fragile properties. To conquer this deformity and to produce appropriate bony embed substance; hydroxyapatite is joined with biocompatible macromoles (kappa-Carrageenan (KCG) and chitosan (CTS)). To improve the mechanical strength of the hydroxyapatite based biocomposite, functionalized multiwalled carbon nanotubes (FMWCNT) is joined to the biocomposite, which has for quite some time been considered for hard and delicate tissue implant because of its remarkable auxiliary and mechanical characteristic properties. It is outstanding that FMWCNT platform is the most-conspicuous substance for the hard tissues reproduction. We have developed a novel FMWCNT/KCG@MHAp nanocomposite on titanium (Ti) implant. The developed nanocomposite coatings implants were portrayed by different strategies (SEM, XRD, TEM). The outcomes show the arrangement and homogeneous conveyance of constituents in the nanocomposite coatings. Addition of FMWCNT and KCG into the MHAp nanocomposite altogether improves the attachment quality and flexible modulus of the scaffolds. Moreover, the reactions of mesenchymal stem cells (MSCs) culture onto the nanocomposite coating show that the suitability of cells was significantly high for FMWCNT and KCG consolidated MHAp than for MHAp. Animal model examinations demonstrate the nearness of delicate osteoblast and fibrous tissue development with no noteworthy provocative symptoms, which recommends that the Addition of FMWCNT and KCG encourage the great biochemical role of MHAp. For load-bearing applications, examine in different bony models is expected to substantiate the medical accessibility. In this manner, from the acquired outcomes, we propose that FMWCNT/KCG@MHAp nanocomposite can be considered as a prospective possibility for orthopedic applications.

Effects of hyperbranched polyesters covalent functionalized multi-walled carbon nanotubes on the mechanical and tribological properties of epoxy composites

In order to improve the mechanical and tribological properties of epoxy composites, the hyperbranched polyesters with terminal carboxyl (HBP) were used for covalent functionalization of multi-walled carbon nanotubes (MWCNTs). The dispersibility and wettability of functionalized MWCNTs (HBP-NH2-MWCNTs) in epoxy resin (EP) were analyzed. The HBP-NH2-MWCNTs reinforced EP composites (HBP-NH2-MWCNTs/EP) were prepared. The microhardness and fracture toughness of HBP-NH2-MWCNTs/EP were tested, and the tribological behavior and mechanism under dry friction conditions were investigated. The results show that the hyperbranched polyesters coated on the surface of MWCNTs forms a physical barrier layer, blocking the van der Waals force between MWCNTs, effectively reducing the agglomeration phenomenon and significantly improving its dispersibility and wettability. Meanwhile, The flexible hyperbranched polyester on the surface of MWCNTs alleviates the stress concentration of the interface and improves the load transfer efficiency, which greatly improves the microhardness and fracture toughness. Under dry friction conditions, the friction coefficient and wear loss of HBP-NH2-MWCNTs/EP composites showed a trend of decreasing first and then increasing as the content of HBP-NH2-MWCNTs increased from 0.3 phr to 1.2 phr. When the content of HBP-NH2-MWCNT is 0.6 phr, the composites has the lowest friction coefficient and the wear loss, and the wear mechanism is mainly characterized by slight fatigue wear.

Experimental investigation of stability and thermal conductivity of phase change materials containing pristine and functionalized multi-walled carbon nanotubes

The biggest challenge in dispersion of nanoparticles in phase change materials (PCMs) is the physical stability of these particles in PCM. Numerous studies have evaluated the effect of different parameters on the stability of nanoparticles in PCM, but the effect of PCM polarity has rarely been investigated. In this study, the stability of functionalized and pristine multi-walled carbon nanotubes (MWCNTs) in three different PCMs with various polarity levels was investigated. The utilized PCMs were paraffin wax (nonpolar), stearic acid (partially polar), and polyethylene glycol (polar). Two different methods of functionalization of MWCNTs, with stearic acid and hexadecyl amine, were used to compare their stability in PCMs. The FTIR analysis and FESEM images reveal that the surface modification reactions were done thoroughly and MWCNTs are well dispersed in PCM. The results showed that pristine MWCNT is more stable in nonpolar PCMs (paraffin and stearic acid), while the samples containing functionalized MWCNT or surfactant had higher stability in polyethylene glycol. The three most stable samples were used to measure their thermal conductivity and heat release/storage capability. The addition of nanoparticles to all kinds of PCMs led to higher rate of heat storage and release. Moreover, the thermal conductivity of all PCMs improved by the introduction of nanoparticles. In both liquid and solid phases, nanoenhanced PCM had higher thermal conductivity compared to pure PCM with stearic acid containing 1 mass% of pristine MWCNT having the highest rate of enhancement at 16.82% for solid phase.

An insight into the novel covalent functionalization of multi-wall carbon nanotubes with pseudopeptide backbones for palladium nanoparticles immobilization: A versatile catalyst towards diverse cross-coupling reactions in bio-based solvents

Materials functionalization with multicomponent reactions (MCRs) has grabbed a lot of attention nowadays due to the integration of outstanding features of MCRs with materials domains. Herein, we put the spotlight on the isocyanides and Meldrum’s acid-based MCRs route for the one-pot covalent functionalization of multi-wall carbon nanotubes (MWCNTs) which led to pseudopeptide-decorated MWCNTs with the ability to immobilized palladium nanoparticles and serve as a neoteric catalytic system. Characterization of the synthesized nanocatalyst was carried out by FT-IR, 1H NMR, XRD, SEM, TEM, EDX and TGA. The catalytic activities of the nanocatalyst for diverse carbon-carbon cross-coupling reactions were examined in bio-based solvents. The results showed the catalytic performance of the nanocatalyst for the formation of Csp2-Csp2, Csp-Csp2 and Csp-Csp bonds through homocoupling and intermolecular Ullmann, CH arylation, Mizoroki-Heck, Sonogashira and Glaser coupling reactions with considerable improvements in the yield, reaction times, bio-based media and chemoselectivity of the procedures. Additionally, this method demonstrated a high potential for recycling of heterogeneous catalysts by maintaining their initial performances without any evidence of the Pd leaching.