Surface Of Multi-walled Carbon Nanotubes Research Articles

A new method of grafting multi-walled carbon nanotubes on carbon fibers for improving the mechanical and thermal properties of woven fabric composites

A new method of grafting multi-walled carbon nanotubes (MWCNTs) onto carbon fiber surface to improve the thermo-mechanical properties of woven carbon fabric reinforced composites was proposed. In this method, both carbon woven fabrics and MWCNTs were oxidized by sulfuric acid to generate carboxyl groups on their surfaces, respectively. Then silane coupling agent was used to react with the carboxyl groups to graft MWCNTs onto the carbon fiber surfaces of the woven fabric. The untreated, acid treated and MWCNTs grafted carbon woven fabrics were separately combined with polypropylene films to form composite plates by thermal-stamping. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were conducted to estimate the changes of element contents and functional groups on surfaces of carbon fibers and MWCNTs. Atomic force microscope was used to estimate the roughness of carbon fiber surfaces. Scanning electron microscopy, differential scanning calorimeter, dynamic mechanical thermal analysis and tensile tests were carried out to analyze the surface morphology, thermal, and mechanical properties of carbon fabrics and their composites. Testing results showed that MWCNTs could be successfully grafted onto the carbon fibers by using silane as an intermediate bridge. Compared with the untreated and acid treated composites, the in-plane shearing stiffness and fracture strength of the composites were increased significantly by MWCNTs grafting. In terms of thermal properties, acid treatment and MWCNTs grafting have little effect on melting point of composites. MWCNTs can promote the recrystallization process of the PP and reduce the numbers of imperfect crystals. As for thermo-mechanical properties, acid treatment deteriorated the bending storage modulus of the composite, while MWCNTs grafting could compensate it.

Pd-decorated CNT as sensitive material for applications in hydrogen isotopes sensing - Application as gas sensor

Applicability of multiwall carbon nanotubes (MWCNTs) decorated with palladium nanoparticles as sensitive layer in a resistive microsensor for identification of hydrogen isotopes, Deuterium (2H) and Protium (1H), has been demonstrated. Palladium nanoparticles were anchored on the MWCNTs surface via a chemical process involving micellization, from a precursor chloride solution, in high ultrasonic density field. Pd-MWCNTs are quasi-aligned between the interdigitated gold electrodes of a SiO2 substrate by drop casting and di-electrophoretic alignment in Tetrahydrofuran (THF) and Nafion solution. The morphostructural characterization of the sensitive material has been carried out through SEM, TEM and Raman spectroscopy and its gas sensing properties were evaluated using electrical measurements performed on a series of isotope concentrations (ranging from 0.1% up to 1%, and from 1% to 4%, value to which hydrogen becomes explosive) diluted in argon, to observe the evolution of the sensor sensibility. The two hydrogen isotopes have different behaviors related to the adsorption on the Pd-MWCNT, which is well observed in the resistance change. Therefore, the sensor based on Pd-MWCNTs could be a viable solution to be integrated in systems for hydrogen leakage detection.

Preparation of a novel flame retardant based on diatomite/polyethyleneimine modified MWCNT for applications in silicone rubber composites

A new flame retardant, DM/PEI/MWCNT, was prepared by self-assembly method based on non-covalent interactions between hydroxyl and amino groups on the surface of hydroxyl multi-walled carbon nanotubes (MWCNT), polyethyleneimine (PEI) and diatomite (DM). The flame-retardant composites were prepared by adding DM/PEI/MWCNT to room-temperature vulcanisated silicone rubber (RTV-silicone). The structure of the flame retardant and composites was characterised by polarising light microscope, scanning electron microscopy and Fourier-transform infrared spectroscopy. The flame retardancy of composites was studied by limited oxygen index and cone calorimeter measurement. Results showed that RTV-silicone composites with DM/PEI/MWCNT owned better flame retardancy. In addition, DM/PEI/MWCNT exhibited better compatibility in silicone rubber than that of unmodified DM, and the tensile properties of RTV-silicone/DM/PEI/MWCNT composites were improved compared to pure RTV-silicone.

CVD Conditions for MWCNTs Production and Their Effects on the Optical and Electrical Properties of PPy/MWCNTs, PANI/MWCNTs Nanocomposites by In Situ Electropolymerization

In this work, the optimal conditions of synthesizing and purifying carbon nanotubes (CNTs) from ferrocene were selected at the first stage, where decomposition time, argon fluxes, precursor amounts, decomposition temperature (at 1023 K and 1123 K), and purification process (HNO3 + H2SO4 or HCl + H2O2), were modulated through chemical vapor deposition (CVD) and compared to commercial CNTs. The processing temperature at 1123 K and the treatment with HCl + H2O2 were key parameters influencing the purity, crystallinity, stability, and optical/electrical properties of bamboo-like morphology CNTs. Selected multiwalled CNTs (MWCNTs), from 1 to 20 wt%, were electropolymerized through in-situ polarization with conductive polymers (CPs), poly(aniline) (PANI) and poly(pyrrole) (PPy), for obtaining composites. In terms of structural stability and electrical properties, MWCNTs obtained by CVD were found to be better than commercial ones for producing CPs composites. The CNTs addition in both polymeric matrixes was of 6.5 wt%. In both systems, crystallinity degree, related to the alignment of PC chains on MWCNTs surface, was improved. Electrical conductivity, in terms of the carrier density and mobility, was adequately enhanced with CVD CNTs, which were even better than the evaluated commercial CNTs. The findings of this study demonstrate that synergistic effects among the hydrogen bonds, stability, and conductivity are better in PANI/MWCNTs than in PPy/MWCNTs composites, which open a promissory route to prepare materials for different technological applications.

Effect of functionalization on the electrochemical behavior of multi-walled carbon nanotube and parafilm nanocomposites

Soft, flexible and conductive interfaces are in high demand in wearable electronics where it can be used as electrode material integrated with commercial electronic components and living system. In the present study, we have developed flexible nanocomposites of multi-walled carbon nanotubes (MWCNTs) with parafilm (PF) thermoplastic. As the presence of carboxylic functionalization (─COOH groups) at MWCNT surface improves their dispersion properties, pristine MWCNTs (p-MWCNT) were oxidized to produce functionalized multi-walled carbon nanotubes (f-MWCNT) and it was further used as conductive filler. Characterization and comparison of morphological, physical, chemical and electrochemical properties of p-MWCNT, f-MWCNT, p-MWCNT-PF nanocomposite film and f-MWCNT-PF nanocomposite film was done using SEM, FTIR, RAMAN spectroscopy, TGA and electrochemical studies. The results suggest that chemical oxidation of p-MWCNT majorly generates carboxylic functions at the p-MWCNT surface which decreases as f-MWCNT embeds in the PF matrix. The f-MWCNT-PF nanocomposite films are thermally more stable as compared to p-MWCNT-PF nanocomposite films. Chemical oxidation treatment generates graphitic defects facilitating electron transfer process and higher conductivity at the f-MWCNT-PF nanocomposite film electrode surface. We believe that the comprehensive performance of soft and flexible f-MWCNT-PF nanocomposite films offers a unique and effective way to develop electrochemical platform for biosensor fabrication in wearable applications.

Multi-walled carbon nanotubes decorated with silver nanoparticles for antimicrobial applications

Great attention has been paid to antimicrobial agents' development to face and control infection transmission of infectious diseases spreading. Decorated multi-walled carbon nanotubes (MWCNTs) with silver nanoparticles (Ag NPs) are useful substances with antibacterial potency that might be used for a wide range of medical applications and water disinfection to limit the spreading of infectious diseases. In this work, silver nanoparticles were loaded on the surface of MWCNTs via the wet-impregnation technique followed by thermal treatment at 450 °C for 4 h in an inert atmosphere. Different ratios of Ag NPs (0, 3, 6, 12 and 24) were loaded on the surface of MWCNTs. The synthesized Ag-MWCNTs nanocomposites were characterized by XRD, XPS, and TEM. The antibacterial efficacy of Ag-MWCNTs nanocomposites was tested towards different microbial strains (bacteria and fungus); P. aeruginosa, E. coli, B. subtilis, S. aureus, C. albicans, and A. niger, which proved the wide spectrum of Ag-MWCNTs. The synthesized nanocomposite showed a higher antimicrobial capability against gram-positive than gram-negative bacteria. Biological studies indicated a large inhibition zone for each bacterial strain that reaches 18.5 mm. SEM and fluorescent microscopy were tested to examine the structural disruption in the outer membranes after incubation with the antibacterial agent. The nanocomposite firmly agglutinated to the surface of the bacterial cells, leading to cells' wrapping, morphology deterioration, and cell death. The inhibition ability of Ag-MWCNTs nanocomposite with a broad spectrum of microorganisms provides exciting opportunities to enhance and maximize potable water disinfection and medical applications to control infectious diseases spreading.

Kinetics and thermodynamics adsorption of Oxazepam drug on the multi‐walled carbon nanotube

AbstractNowadays, it is admitted to using of suitable carrier results in improving drug delivery such as nanotubes. So, multi‐walled carbon nanotube (MWCNTs) has been proposed as a carrier (adsorbent) to improve the neurological Oxazepam (OZ) drug delivery. Freundlich, Temkin, and Langmuir isotherm models have been used in order to do assay adsorption of the OZ on the MWCNT. The maximum value of the isotherm constant (b = 0.14 L/mg) at 303 K temperature indicates stronger (better) adsorption of the OZ on the MWCNT surface in low concentrations (20 mg/L) and acidic pH; in fact, increasing of pH led to decreasing adsorption (60 → 35.91 mg/g) and dehydrogenation of the OZ drug. Reaching to the equilibrium state after 90 min and negative value of the ∆H (−41.57 kJ/mol) shows that the OZ adsorption has fast kinetic and exothermic processes. These issues imply depending of the OZ adsorption on the OZ concentration and the weight of adsorbent in the adsorption process.

Non-enzymatic glucose sensor and photocurrent performance of zinc oxide quantum dots supported multi-walled carbon nanotubes

Hybrid nanocomposites consisting of carbon nanotubes (CNT)/nanomaterial heterostructure play a key part in the excellent performance of nano-devices by coupling different functionalities. In this study, a glucose sensor was fabricated by immobilizing zinc oxide quantum dots (ZnO QDs) on multiwall carbon nanotubes (MWCNTs) nanocomposites using ultrasonication in an ease and economical method. ZnO QDs with ~ 3–8 nm diameters were grown and anchored on the surface of MWCNTs. These nanocomposites were characterized using different spectroscopy and microscopy techniques. XRD reveals the wurtzite structure of ZnO. TEM confirmed that ZnO QDs were anchored onto MWCNTs. The synthesized nanocomposites were applied as a sensor for electrochemical detection of glucose and as a photoelectric effect for photoelectric current measurements. The electrochemical properties of the MWCNT/ZnO QDs nanocomposite were enhanced significantly for glucose sensing when compared to pristine ZnO and MWCNTs. Results showed that ZnO QDs anchored over MWCNTs have a sensitivity of 9.36 µA µM−1 with repeatable results. The detection limit was found to be 0.208 µM. By applying nanocomposites on the sensor, the linear range could be extended from 0.1 to 2.5 µM, which increases the response time to less than 3 s. Experimental results also indicate that the sensor response is unaffected by the common interference agents during glucose-sensing such as sucrose, ascorbic acid, dopamine and uric acid. The proposed sensor was successfully employed to detect glucose levels in human urine samples with satisfactory outcomes.

Clicked Bifunctional Dendrimeric and Cyclopeptidic Addressable Redox Scaffolds for the Functionalization of Carbon Nanotubes with Redox Molecules and Enzymes.

Carbon nanotube electrodes were modified with ferrocene and laccase using two different click reactions strategies and taking advantage of bifunctional dendrimers and cyclopeptides. Using diazonium functionalization and the efficiency of oxime ligation, the combination of both multiwalled carbon nanotube surfaces and modified dendrimers or cyclopeptides allows the access to a high surface coverage of ferrocene in the order of 50 nmol cm-2, a 50-fold increase compared to a classic click reaction without oxime ligation of these highly branched macromolecules. Furthermore, this original immobilization strategy allows the immobilization of mono- and bi-functionalized active multicopper enzymes, laccases, via copper(I)-catalyzed azide-alkyne cycloaddition. Electrochemical studies underline the high efficiency of the oxime-ligated dendrimers or cyclopeptides for the immobilization of redox entities on surfaces while being detrimental to electron tunneling with enzyme active sites despite controlled orientation.

The Effect of Multiwalled Carbon Nanotubes on the Thermal Conductivity and Cellular Size of Polyurethane Foam

Polyurethane (PU) foam is known as the popular material for the applications in many fields of industry and life. To improve the mechanical and thermal properties of this material, in this research, PU foam was reinforced with aniline-modified multiwalled carbon nanotubes (MWCNTs). Fourier transform infrared FTIR spectrum of modified MWCNTs showed the aniline was grafted on the surface of MWCNTs through the appearance of –NH2 stretches. The effect of MWCNTs with and without modification on the density, porosity, compressive strength, and heat conductivity of PU/MWCNT foam nanocomposites was investigated. The dispersibility of MWCNTs in the PU matrix was enhanced after modification with aniline. Compressive strength of PU nanocomposite reached the highest value after adding 3 wt.% of modified MWCNTs into PU foam. Besides, the water uptake of PU nanocomposites using 3 wt.% of MWCNTs was decreased to 13.4% as compared to that using unmodified MWCNTs. The improvement in thermal conductivity of PU/aniline-modified MWCNT nanocomposite was observed due to the change in the cellular size of PU foam in the presence of MWCNTs as shown by SEM images.

Influence of dispersion technique/time on dispersion stability, aspect ratio and morphology of multi-walled carbon nanotubes

Current interest in nanoscience and nanotechnology has motivated a remarkable research effort in carbon nanotubes (CNTs), which has addressed a variety of issues and produced several new findings. The uniform and stable dispersion of CNTs in solvents/nanocomposites is often a necessity for their effective use in advanced materials. In this study, the dispersion states of multiwalled carbon nanotubes (MWCNTs) in numerous solvents were analysed by UV-vis spectroscopy and visual observations (photographic images). Furthermore, the influence of sonication and ball milling time on the MWCNT morphology and dispersion was analysed through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that the MWCNT was highly dispersible in DMF, isopropanol, chloroform and acetone, and the dispersion state of MWCNT in these solvents can be classified as dispersed. The obtained results indicate that the oxidation incorporates oxygen-containing groups on the surface of MWCNTs, which establish the electrostatic stability needed for long-period stable dispersion in solvents. Morphological investigation of MWCNTs shows less than 20 min of dispersion is insufficient to achieve untangled CNTs with good dispersion, while 20-60 min of dispersion demonstrates CNTs bonding, intersections, junctions and number of defects on MWCNTs due to high energy involved. Apart from this, significant MWCNT shortening has been observed for the dispersion period of 90 min-6 h. The investigation of the dispersibility of MWCNTs in different solvents and the effect of sonication and ball milling time on the MWCNT morphology and dispersion are important for enhancing the comprehensive understanding of its applications.

Effect of nanofillers on the crystalline and mechanical properties of EVACO polymer nanocomposites

In this work, the effect of different fillers on the crystalline and mechanical properties of the poly(ethylene-co-vinyl acetate-co-carbon monoxide) (EVACO) terpolymer composite is studied systematically. Alumina trihydrate nanoparticles (nano-ATH), halloysite nanotubes (HNTs), and the multiwalled carbon nanotubes (MWCNTs) are the representative fillers used in the present study. The surface of MWCNTs are decorated using carbonyl, however, nano-ATH and HNTs are used without any surface treatment. The mechanical properties of the composites are evaluated using a tensile test and the improvement in the mechanical properties can be correlated to the improvement in the crystallinity in the composite. The presence of nanofillers in the EVACO matrix significantly influenced the crystallinity, which was determined by X-ray diffraction. The fractography studies reveal the presence of agglomerates at high filler loading results in the subsequent reduction in the tensile properties. Interestingly, the MWCNTs at very low filler loading significantly enhances the tensile properties of EVACO.

Molecular dynamics simulation of contact behaviors between multiwall carbon nanotube and metal surface

The interfacial contact configuration and contact intensity between carbon nanotube and metal surface play an important role in the electrical performance of carbon nanotube field effect transistors and nanoscale carbon nanotube robotic manipulation. In this paper, we investigate numerically the contact configuration and the contact intensity between multiwall carbon nanotube with open ends or capped ends and various metal surfaces in carbon nanotube field effect transistor assembly by the molecular dynamics simulation. The simulation results show that the change in the position and shape of multiwall carbon nanotube on the metal surface are mainly due to the decrease of van der Waals energy reduction: the decrement of van der Waals energy is converted into the internal energy and kinetic energy of carbon nanotubes. Moreover, the binding energy between multiwall carbon nanotube and metal surface is negative, which indicates that multiwall carbon nanotube adheres to the metal surface. In addition, the contact intensity of multiwall carbon nanotube in horizontally contacting metal surface is influenced by initial distance, contact length and metal materials. The final equilibrium distance is around ~0.3 nm when the initial distance is less than ~1 nm. And the contact intensity increases with the augment of contact length between carbon nanotube and metal. The contact intensity between platinum and carbon nanotube is larger than that between tungsten and aluminum, therefore, platinum-coated probe is generally utilized for picking carbon nanotube up. The contact intensity of the carbon nanotubes with the open ends and closed ends in the vertical contact with the metal surface are both lower than those in the horizontal contact. The interfacial contact configuration of carbon nanotube and metal materials mainly include the displacement and geometric deformation of carbon nanotube. The displacement and geometric deformation of multiwall carbon nanotube with open ends on the metal surface finally result in its radial nanoscale ribbon structure. But the closed-end three-wall carbon nanotube has the small axial geometric deformation through comparing the concentration profiles between the initial carbon nanotube and the collapsed carbon nanotube. In a carbon nanotube field effect transistor, the collapsed multiwall carbon nanotube forms the ribbon structure like a single wall carbon nanotube. And the distance between carbon nanotube walls and between the outermost carbon nanotube wall and the metal electrode are both about ~0.34 nm. The atomic scale spacing ensures that electrons tunnel from the metal to the outermost carbon nanotube wall and migrate radially between the inner carbon nanotube walls.

Electrocatalytic dimeric inactivation mechanism by a porphyrinic molecular-type catalyst: integration in a glucose/O2 fuel cell

We report a chemical inactivation/redox reactivation process (IAP) based on the surface-confined rhodium–porphyrinic catalyst on a multi-walled carbon nanotube surface which presents an excellent and stable electron transfer.

Simple Wet Chemical Route for Decoration of Multi-walled Carbon Nanotubes with Nickel Nanoparticles

Due to high specific area and chemical stability, carbon nanotubes (CNTs) are considered to be an excellent support for metal nanoparticles. Carbon nanotube supported metal nanoparticles have applications in different fields. There are different techniques to attached metal nanoparticles on the surface of CNTs. This paper reports a simple wet chemical route to decorate the surface of oxidized multi-walled carbon nanotube (MWCNT) with nickel nanoparticles (NiNPs). The NiNPs decorated MWCNTs have different applications in different fields such as sensors, photocatalytic activity, hydrogen gas production, catalyst, to produce metallic nanowire etc. MWCNT was treated with nitric acid for purification and oxidation. Purification removes the impurities found in MWCNT and oxidation adds different oxygen functional groups. Raman spectroscopy shows the oxidation and attachment of nickel nanoparticles with the help of intensity, position and area ratio of D and G band. The introduction of an oxygen functional group on the surface of MWCNT after oxidation was studied by Infrared spectroscopy. Thermal analysis (thermogravimetric analysis; TGA and differential thermal analysis; DTA) revealed different thermal behavior of pristine, oxidized, and Ni decorated MWCNTs. TGA showed that the decomposition temperature decreased after oxidation and decoration with NiNPs. TGA also confirmed the purification of MWCNTs as well as the presence of nickel with the MWCNTs. Energy dispersive spectroscopy (EDS) also confirmed the presence of nickel in the sample.

Electrically activated chemical bath deposition of CdS on carbon nanotube arrays

Electrically stimulated depositions of CdS nanoparticles on the surface of aligned multi-walled carbon nanotube (CNT) arrays were investigated by applying a voltage of 3 V to the electrodes placed into a chemical bath with an aqueous ammonium solution of CdCl2 and thiourea. The CNT arrays were fixed on positive, negative, and neutral electrodes. Morphology, composition and structure of CdS-CNT hybrids were studied using scanning electron microscopy, Raman scattering and X-ray photoelectron spectroscopy. CdS nanocrystallites in the hybrids were found to exhibit synthesis-dependent luminescence properties. S-vacancy enriched CdS grown on the positively charged CNT array possessed red photoluminescence (PL). Purple emission was attributed to small-size CdS nanocrystals synthesized on the negatively charged CNTs. The CNT array located on a neutral electrode was uniformly covered by CdS nanoparticles with a highly intense blue PL. Our results indicate a promising effect of the electrical field for enhancement of the growth rate of CdS nanocrystals.

Enhancing structural stability and physical properties of silver added iron-MWCNT composite prepared by high energy ball milling and spark plasma sintering

This paper reports the beneficial effect of silver addition (~0.1 wt%) on the structural stabilization of multiwalled carbon nanotube (MWCNT) reinforced in iron matrix by way of high energy ball milling (HEBM) and spark plasma sintering (SPS). Silver added Fe - x wt% MWCNT (x = 1, 2, 3 and 4) composites were prepared by HEBM followed by SPS. Structural characterization of silver bearing composite powder and its sintered mass was carried out by XRD. The structural damage of MWCNT after HEBM was assessed by Raman Spectroscopy. As a support, Fourier Transform Infrared (FTIR) spectroscopic study was used to look into the bonding characteristics. Detailed microstructural studies by optical, field emission scanning (FESEM) and high-resolution transmission electron microscopy were employed to further assess structural stabilization and evolution of micro constituents during processing. Finally, magnetic and electrical properties of the composites were determined.It was revealed that minor addition of silver aids in restoration of the structural integrity of MWCNT in iron matrix composite. Moreover, it was noted that silver added composite could achieve a contamination free matrix–reinforcement interface. It is propounded that silver atoms tether MWCNT surface and behave like coating over MWCNTs. Conductivity of silver doped iron-4 wt% MWCNT composites exhibited a conductivity value higher than that of electrical conductivity grade (EC grade) aluminum. Saturation magnetization of silver doped Fe-MWCNT composite was increased by 25% over pure iron at 3 wt% MWCNT. The observed improvement in properties of composite is ascribed to tethering of silver particles at MWCNT surface; this gave rise to better interfacial bonding and the physical properties.

Wear Behavior of Chemically Bonded Ceramic Coatings Reinforced by MWCNTs–ZnO Hybrid Material

Zinc oxide (ZnO) decorated multi-walled carbon nanotubes (MWCNTs) hybrid material was prepared to improve the tribological performance of chemically bonded ceramic coatings. TEM results reveal that ZnO has been successfully fabricated on the surface of MWCNTs. The tribological performance of the ceramic coatings with MWCNTs–ZnO hybrid material was investigated using a ball-on-disc method. The results show that the friction coefficient and wear rate of the ceramic coatings decrease with the increase of MWCNTs–ZnO hybrid material. The ceramic coatings with MWCNTs-ZnO hybrid material shows a smooth worn surface with less cracks and delamination. In addition, the worn surface of the counterpart ball shows a smaller worn area and a smooth surface. The excellent wear resistance of the ceramic coatings is attributed to the good bonding strength between MWCNTs–ZnO hybrid material and ceramic matrix.

MgFe2O4/CNTs nanocomposite: synthesis, characterization, and photocatalytic activity

Magnesium ferrite is a visible light absorber, and when combined with multiwall carbon nanotubes (MWCNTs), it can lead to low electron–hole recombination rates, thus improving its photocatalytic activity. In this work, a novel MgFe2O4/CNTs nanocomposite catalyst has been synthesized via anchoring MgFe2O4 nanoparticles onto MWCNTs surface by a sol–gel and microwave-assisted route. The prepared catalyst was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning and transmission electron microscopy, energy-dispersive X-ray analysis and vibrating scanning magnetometry. MgFe2O4 nanoparticles showed a cubic inverse spinel ferrite structure, while MgFe2O4/CNTs nanohybrids showed combinations of both structures. Morphology studies including Brunauer–Emmett–Teller (BET) analysis confirmed a 40 m2 g−1 specific surface area with narrow mesoporous size distribution for the MgFe2O4/CNTs nanocomposite. The photocatalytic performance of the new catalyst was assessed by photodegradation of methylene blue (MB). The experimental results demonstrated that MgFe2O4/CNTs exhibited strong photocatalytic activity, catalysing the photooxidation of about 98% of MB in 25 min under sunlight.

A Single-Molecule Label-Free Identification of Single-Nucleotide Colorectal-Cancer-DNA Polymorphism Using Impedance Spectroscopy of Self-Redox-Active Decorated Carbon Nanotubes

A novel label-free impedance assay which is based on self-redox active carbon nanotube arrays decorated by nanocyclic organometallic complex monolayer is offered to discriminate single-nucleotide polymorphism of colorectal-tumor genome. The assay is based on the following effects. A mass transfer for the multiwalled carbon nanotubes (MWCNTs) is testified by a Cole–Cole plot with Warburg impedance in dielectric spectra. Charging K(K')-point of graphene Brillouin zone is associated with the mass transfer for MWCNTs that leads to arising of charged MWCNT-end states. Plasma oscillations of charge carriers shield electric field of charged electrodes. Complementary hybridization of target deoxyribonucleic acid (DNA) with probe DNA on the MWCNT surface facilitates the penetration of single-stranded target DNA in the nanopores. Dielectric-band appearance and shielding effects testify the duplex formation.