Surface Of Multi-walled Carbon Nanotubes Research Articles

Silver Nanoparticle-Decorated Multiwalled Carbon Nanotube Ink for Advanced Wearable Devices.

Silver nanoparticles of average size 12-13 nm were successfully decorated on the surface of multiwalled carbon nanotubes (MWCNTs) through a scalable wet chemical method without altering the structure of the MWCNTs. Employing this Ag@MWCNT, a multifunctional room-temperature curable conductive ink was developed, with PEDOT:PSS as the conductive binder. Screen printing of the ink could yield conductive planar traces with a 9.5 μm thickness and a conductivity of 28.99 S/cm, minimal surface roughness, and good adhesion on Mylar and Kapton. The versatility of the ink for developing functional elements for printed electronics was demonstrated by fabricating prototypes of a wearable strain sensor, a smart glove, a wearable heater, and a wearable breath sensor. The printed strain sensor exhibited a massive sensing range for wearable applications, including an impressive 1332% normalized resistance change under a maximum stretchability of 23% with superior cyclic stability up to 10 000 cycles. The sensor also exhibited an impeccable gauge factor of 142 for a 5% strain (59 for 23%). Furthermore, the sensor was integrated into a smart glove that could flawlessly replicate a human finger's gestures with a minimal response time of 225-370 ms. Piezoresistive vibration sensors were also fabricated by printing the ink on Mylar, which was employed to fabricate a smart mask and a smart wearable patch to monitor variations in human respiratory and pulmonary cycles. Finally, an energy-efficient flexible heater was fabricated using the developed ink. The heater could generate a uniform temperature distribution of 130 °C at the expense of only 393 mW/cm2 and require a minimum response time of 20 s. Thus, the unique formulation of Ag@MWCNT ink proved suitable for versatile devices for future wearable applications.

Cubic MnSe2 nanoparticles dispersed on multi-walled carbon nanotubes: A robust electrochemical sensing platform for chloramphenicol

A robust electrochemical sensor for chloramphenicol has been constructed by cubic MnSe 2 nanoparticles decorated on multi-walled carbon nanotubes. • MnSe 2 nanoparticles were firstly synthesized by a one-step hydrothermal process. • MnSe 2 /MWCNTs shows excellent synergistically catalytic properties towards CAP redox. • MnSe 2 /MWCNTs /GCE displays wide detection range for CAP sensing. • Detection of CAP in food and biological fluids was implemented. In this work, cubic MnSe 2 nanoparticles were firstly synthesized through a simple one-step hydrothermal procedure at low temperature using N 2 H 4 ·H 2 O as a reductant as well as MnCl 2 and Se powders as precursors. The crystalline structure, morphology, chemical composition, and element valence states of the synthesized samples were specifically investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray photoelectron spectra (XPS), and Raman spectroscopy. It was found that the MnSe 2 product mainly exists in a roughly cubic morphology with the sizes between 20 and 50 nm. In order to alleviate the aggregation, cubic MnSe 2 nanoparticles were further ultrasonically dispersed on the surface of multi-walled carbon nanotubes (MWCNTs) to achieve an improved stability structure denoted as MnSe 2 /MWCNTs. Compared with the single components, the MnSe 2 /MWCNTs composite displays enhanced electrochemical sensing signals for chloramphenicol (CAP) derived from the synergistic catalytic performance of the corresponding components. After optimization of electrochemical assay parameters, an assay range of 8.00–5000.00 μM and a limit of detection (LOD) with 2.00 μM for CAP were obtained using the MnSe 2 /MWCNTs-based sensor. Finally, the application of the resulting sensor for CAP detection in food and biological fluids was evaluated with recoveries between 94.70 and 106.70 %, demonstrating that MnSe 2 /MWCNTs could be served as a preeminent sensing platform. To the best of our knowledge, this is the first report on the fabrication of MnSe 2 -based composite for electrochemical sensing applications.

Effect of MWCNTs surface functionalization group nature on the thermoelectric power factor of PPy/MWCNTs nanocomposites

This work aims to put forward the role of multiwalled carbon nanotubes (MWCNTs) surface functionalization on the enhancement of thermoelectric (TE) power factor of new nanocomposite-based polypyrrole/surface modified multiwalled carbon nanotubes (PPy/MWCNTs), prepared by a facile in-situ oxidative polymerization process. In fact, MWCNTs’ content was fixed to ∼11 wt%, and their surfaces were respectively modified with different functional groups (benzoic acid (-D1), benzene tricarboxylic acid (-D3), -O, -COOH, -NH2 and -SH). After running all the required, spectral, structural, morphological, and thermoelectrical characterizations, it is revealed that the nanocomposites-based functionalized MWCNTs remarkably increase the Seebeck coefficient, and thus enhancing the material’s power factor. This improvement of TE power factor was attributed to the coating homogeneity and the good interaction between PPy and MWCNTs mainly through π–π stacking between the polymer chains and the nanotubes as well as electrostatic, hydrogen bonding, and electrons donor/acceptor groups interactions due to the functional groups grafted on the nanotube’s sidewall. The highest power factor value (0.51 μWm−1K−2) was obtained with PPy/MWCNTs-SH, which means an enhancement of 8 folds compared to pure PPy. Considering the content of MWCNTs and the ease of preparation process, these results might help to develop future TE materials and devices.

Electrochemical properties and electrocatalytic activity of novel iron and manganese tribenzopyrazinoporphyrazine complexes

Two novel tribenzopyrazinoporphyrazines with peripheral 4-methoxyphenyl substituents were synthesized to evaluate the effect of the centrally coordinated transition metal cation (4 – Mn3+ or 5 – Fe3+) on their electrochemical properties. The obtained complexes were characterized by UV–vis spectrophotometry, mass spectrometry, and NMR techniques. The electrochemical measurements, involving the CV and DPV voltammetry, were performed and revealed four or six redox processes in researched compounds with one related to the reduction of the central metal cation. The HOMO-LUMO electrochemical band gaps of the synthesized porphyrazines were estimated, and the obtained values were in a good agreement with the optical band gaps calculated from UV–vis. The empirical studies were accompanied by the theoretical ones including linear response time-dependent density function theory (LR TD-DFT) calculations. In both porphyrazines, the HOMOs presented similar shapes. The electrochemical sensing properties of porphyrazines were studied after their deposition on the surface of multi-walled carbon nanotubes (MWCNT). The obtained hybrid materials were embedded on glassy carbon electrodes (GC) using the drop and dry technique. The functionalized electrodes were studied for electrocatalytic reduction of diclofenac sodium salt revealing the superior performance of the GC/MWCNT/5 electrode.

Abnormal magnetic behavior of prussian blue analogs modified with multi-walled carbon nanotubes

This work examines the origin of the abnormal magnetism exhibited by CuMnFe–PBAs modified with multi-walled carbon nanotubes (MWCNTs). The system of CuMnFe–PBAs@MWCNTs coexists with both large and small clusters. CuMnFe–PBAs clusters have an average particle size of 28 nm, and some of the smaller particles are adsorbed on the surface of MWCNTs. Surprisingly, the magnitude of magnetization increases linearly with decreasing temperature. When above the Curie temperature, the magnitude of magnetization is significantly greater than that of PBAs without being modified. This phenomenon can be attributed to magnetostatic interactions between ultra-fine magnetic nanoparticles adsorbed on the surface of MWCNTs. Using the Monte Carlo method, we simulated the magnetostatic interaction of cylindrical adsorbed particles, and the simulation results are almost identical to those observed experimentally. The results indicate that 0.089 CuMnFe–PBAs clusters per 1 nm2 can be adsorbed onto the surface area of MWCNTs. We demonstrate that MWCNTs adsorbing magnetic particles exhibit magnetic behavior, and suggest a method for producing ultrafine materials. It also introduces a new method of calculating the adsorption efficiency of carbon nanotubes, offering theoretical guidance for future research on nanomaterials with enhanced adsorption efficiency.

Surface modification of MWCNT to improve the mechanical and thermal properties of natural rubber nanocomposites

AbstractIn this study, we focused on the synergistic effect between carbon black (CB) and multiwall carbon nanotube (MWCNT) hybrid fillers. In particular, the surface modification of pristine MWCNT (P‐MWCNT) via an acid (oxidation) treatment was used to improve their dispersion, as well as the mechanical and thermal properties of their corresponding natural rubber (NR)‐based nanocomposites. Fourier‐transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were carried out to determine the presence of functional groups on the oxidized MWCNT (O‐MWCNT). After vulcanization, dynamic mechanical analysis (DMA), tensile properties, hardness, thermal conductivity, swelling behaviour in toluene and SEM characterizations were performed on both NR/CB/P‐MWCNT‐ and NR/CB/O‐MWCNT‐based nanocomposites. The results showed the positive effect of MWCNT surface oxidation on the fillers' dispersion and nanocomposites' properties.

The Effect of Surface Coating Treatment on the Properties of Carbon Nanotube Reinforced Copper Matrix Composites

Herein, the surface of multi‐walled carbon nanotubes (MWCNTs) is treated with HNO3 oxidation to carry on oxygen‐containing functional groups. Then, the pretreatment surface of MWCNTs are plated with copper to improve the low wettability of carbon nanotubes (CNTs). Finally, metal matrix composite blocks with excellent properties are prepared by spark plasma sintering (SPS). When the content of the reinforcing phase is 0.25 wt%, the tensile strength and hardness of Cu‐MWCNTs/Cu composite compared with pure copper are increased by 34.6% and 136.1%, respectively.

A high-sensitivity thin-film MWNT@PDA-AgNP nanocomposite sensor for acquiring microscopic deformations

Carbon nanomaterial/polymer-based flexible strain sensors form the foundations of many cutting-edge applications, e.g., personalized health monitoring, human-machine interaction, etc. However, achieving a high sensitivity to slight deformations remains a challenging task for the existing technologies. Herein, we immobilize silver nanoparticles (AgNPs) onto the surfaces of multi-wall carbon nanotubes (MWNTs) by a polydopamine (PDA)-assisted process, in order to fabricate a new nanocomposite sensor for capturing microscopic static deformations (strain: <1%) and microscopic high-frequency vibrations (strain: <0.001%, frequency: up to 100 s kHz). The material characterizations performed show that AgNPs are compounded, in their elemental state, with the PDA nanolayers on the surfaces of MWNTs, and help to lower the potential barriers between nanofillers. As such, the tunneling of electrons across adjacent nanofillers, which underpins the sensing of slight deformations, is promoted. The proposed nanocomposite sensor demonstrates a significantly higher sensitivity to both static (gauge factor: ∼38) and dynamic deformations, than control specimens that are fabricated from pure MWNTs or PDA-coated MWNTs. Moreover, the sensitivity of the new sensor to microscopic high-frequency vibrations is positively related to the mass of the AgNPs added. This study presents a promising surface modification approach for optimizing the sensitivities of carbon nanomaterial/polymer-based strain sensors to slight deformations.

Dual Matrix Influence on Ni(II) Rich Hybrid Catalyst for Electrochemical Methanol Oxidation Reaction

AbstractThe influence of two different surface matrices, that is, zeolite‐Y and multi‐walled carbon nanotubes (MWCNTs), on the electrocatalytic ability of Ni(OH)2 combined with MnO2 has been studied. The Ni and Mn loaded in different ratio exhibited different current density with respect to the change in the nature of support. The MnO2−Ni(OH)2 catalyst decorated like a fish in a net‐stock at the interface of the zeolite‐Y and the MWCNT with high Ni(II) content provided the highest current density of 3.8 Amg−1 and 3.6 Amg−1 with platinum and graphitic rod as counter electrode, respectively. The study revealed that both the concentration of the Ni(II) as well as the nature of the support influenced the electrochemical behaviour of MnO2−Ni(OH)2. The electrochemical surface area as well as the durability of the catalyst having two different supports showed higher values in comparison to those in single matrix. The plot of current density vs. square root of scan rate showed diffusion control methanol oxidation process. The results predicted that the MnO2−Ni(OH)2 catalyst containing both zeolite‐Y and MWCNT surface indicated that under the highly basic condition it can withstand for long period without significant loss in current density during the methanol oxidation reaction process.

Stabilization of Carbon Nanotubes and Graphene by Tween-80: Mechanistic Insights from Spectroscopic and Simulation Studies.

Polyoxyethylene sorbitan monooleate is commonly used to obtain stable dispersions of nanoparticles (NPs) such as carbon nanotubes (CNTs) and graphene. However, the mechanism underlying dispersion is poorly understood. The present study aimed at investigating the mechanism of stabilization of carbon NPs (CNPs), namely, single-walled CNTs (SWCNTs), multi-walled CNTs (MWCNTs), and graphene, by Tween-80 using attenuated total internal reflection-Fourier transform infrared and nuclear magnetic resonance (NMR) spectroscopy. Molecular dynamics (MD) simulations were performed to identify, at the atomic scale, the significant interactions that underlie the adsorption and the stabilizing effect of Tween-80 on CNPs, in this way corroborating the spectroscopy results. Spectroscopic analysis revealed that the alkyl chain tether to SWCNT, MWCNT, and graphene surface, presumably through π-π interactions between the carbon-carbon double bond in the alkyl chain and the aromatic rings of CNPs. The hydrophilic polyethoxylate chains extend into the aqueous environment and stabilize the suspension by steric hindrance. MD simulations also showed that Tween-80 molecules interact with the CNP surface via the alkyl chain, thus corroborating spectroscopy results. MD simulations additionally revealed that Tween-80 aggregates on the CNP surface shifted from planar to micelle-like with increasing Tween-80 ratios, underscoring concentration-dependent changes in the nature of these interactions.

Noncovalent Assembly and Catalytic Activity of Hybrid Materials Based on Pd Complexes Adsorbed on Multiwalled Carbon Nanotubes, Graphene, and Graphene Nanoplatelets.

Green catalysts with excellent performance in Cu-free Sonogashira coupling reactions can be prepared by the supramolecular decoration of graphene surfaces with Pd(II) complexes. Here we report the synthesis, characterization, and catalytic properties of new catalysts obtained by the surface decoration of multiwalled carbon nanotubes (MWCNTs), graphene (G), and graphene nanoplatelets (GNPTs) with Pd(II) complexes of tetraaza-macrocyclic ligands bearing one or two anchor functionalities. The decoration of these carbon surfaces takes place under environmentally friendly conditions (water, room temperature, aerobic) in two steps: (i) π–π stacking attachment of the ligand via electron-poor anchor group 6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxo-pyrimidine and (ii) Pd(II) coordination from PdCl42–. Ligands are more efficiently adsorbed on the flat surfaces of G and GNPTs than on the curved surfaces of MWCNTs. All catalysts work very efficiently under mild conditions (50 °C, aerobic, 7 h), giving a similar high yield (90% or greater) in the coupling of iodobenzene with phenylacetylene to form diphenylacetylene in one catalytic cycle, but catalysts based on G and GNPTs (especially on GNPTs) provide greater catalytic efficiency in reuse (four cycles). The study also revealed that the active centers of the ligand-Pd type decorating the support surfaces are much more efficient than the Pd(0) and PdCl42– centers sharing the same surfaces. All of the results allow a better understanding of the structural factors to be controlled in order to obtain an optimal efficiency from similar catalysts based on graphene supports.

Effect of MWNT Functionalization with Tunable-Length Block Copolymers on Dispersity of MWNTs and Mechanical Properties of Epoxy/MWNT Composites.

The dispersion level of carbon nanotubes (CNTs) and interface design are two of the most crucial roles in developing the superior mechanical performance of polymer/CNT nanocomposites. In this work, a series of azide-terminated poly(glycidyl methacrylate)-block-poly(hexyl methacrylate) (PGMA-b-PHMA) copolymers with different PHMA chain lengths and similar PGMA chain lengths were grafted on the surface of multiwall carbon nanotubes (MWNTs). PHMA length changes significantly impact the grafting density and solubility in organic solvents of as-prepared block copolymer functionalized MWNTs(bc@fMWNTs). Then, the bc@fMWNTs were introduced to epoxy, and the resulted epoxy/bc@fMWNT composites show better mechanical properties than neat epoxy and epoxy/p-MWNT composites. The results suggest that longer PHMA chains cause the two competitive and opposing effects on the dispersion state and soft interface. On the one hand, the longer PHMA chains on the surface of MWNTs would afford higher deformation for the matrix and enhanced mobility for MWNTs because of the soft and flexible nature of PHMA, enhancing the energy dissipation during strain. On the other hand, as the length of PHMA extends, the dispersion level of bc@fMWNTs in epoxy declines, which is harmful to the composite’s mechanical properties. Hence, epoxy/bc@fMWNTs composites with relatively short PHMA chains show the best tensile and fracture properties.

Quantitative Characterization of Oxygen-Containing Groups on the Surface of Carbon Materials: XPS and NEXAFS Study

The results of the comparative quantitative study of oxygen-containing groups adsorbed on the surface of carbonized sponge scaffold (CSS), highly oriented pyrolytic graphite (HOPG), fullerite C60 and multi-walled carbon nanotubes (MWCNTs) introduced into a high vacuum from the atmosphere without any pre-treatment of the surface are discussed. The studied materials are first tested by XRD and Raman spectroscopy, and then quantitatively characterized by XPS and NEXAFS. The research results showed the presence of carbon oxides and water-dissociation products on the surfaces of materials. It was shown that main source of oxygen content (~2%) on the surface of HOPG, MWCNTs, and C60 powder is water condensed from the atmosphere in the form of an adsorbed water molecule and hydroxyl group. On the CSS surface, oxygen atoms are present in the forms of carbon oxides (4–5%) and adsorbed water molecules and hydroxyl groups (5–6%). The high content of adsorbed water on the CSS surface is due to the strong roughness and high porosity of the surface.

Industrial block copolymer surfactants: Diversity of associative forms and interaction with carbon nanomaterial

• Upon copolymer micellization alteration of micelle shape and hydrodynamic size takes place. • Hypothesis about the double-stage nature of copolymer micellization was proposed. • Diversity of associative forms of MWCNT-block copolymer complexation was revealed. • Interaction of block copolymers can results in liquid crystal structuring. In this work, we studied self-association/micellization of several block copolymers based on PEO and PPO blocks – two poloxamers and reverse-sequential poloxamine in aqueous solutions and dispersions of multi-walled carbon nanotubes (MWCNTs). To study this process the number of NMR experiments was used, such as self-diffusion measurements and spectral analysis including alterations of chemical shift and resonance line width. The absence of strictly defined critical micelle concentration, when micelles of constant size start forming, was found. The obtained results proved that amphiphilic copolymers alter micelle shape and hydrodynamic size upon the growth of polymer concentration. The hypothesis about the double-stage nature of copolymer molecules association/micellization has been proposed. At the first stage the polymers hydrophobic blocks connect into cord-like associates/micelles and then these associates join into spherical micelles or liquid-crystalline domains. The transmission electron microscopy of block copolymers revealed a variety of their associative forms. The interaction peculiarities of various associates for different block copolymers with MWCNTs were considered. In poloxamers/MWCNTs dispersions the central hydrophobic blocks of poloxamers can be adsorbed on the hydrophobic surface of MWCNTs, isolating a part of the nanotube surface, thereby preventing their sticking. For the X-shaped diproxamine another mechanism of interaction with carbon surface was proposed, which makes it possible to explain the opposite NMR effects in the presence of MWCNTs. The transmission electron microscopy revealed a variety of associative forms of block copolymers studied.

Structure and magnetic properties of MWCNTs decorated by NiFe, CoFe, NiCo nanoparticles

The method of salt impregnation was applied to grow magnetic alloy nanoparticles (Ni20Fe80, Co93Fe07 or Ni20Co80) on multi-walled carbon nanotubes (MWCNTs). It was confirmed by SEM and XRD that the method gives nanopowders where the metal component is in the form of granules (20-40 nm in diameter) which are distributed over the surface and edges of the nanotubes. Measurements of magnetic properties confirmed that magnetic particles are small single-domain, randomly oriented assembly of spherical (or close to spherical) particles on the MWCNTs surface. Saturation magnetization of the investigated nanopowders weakly depends on temperature while coercive field increases under temperature decrease.

Oxygen‐coordinated low‐nucleus cluster catalysts for enhanced electrocatalytic water oxidation

AbstractThe oxygen evolution reaction (OER) activity of single‐atom catalysts (SACs) is closely related to the coordination environment of the active site. Oxygen‐coordinated atomic metal species bring about unique features beyond nitrogen‐coordinated atomic metal species due to the fact that the M–O bond is weaker than the M–N bond. Herein, a series of metal–oxygen–carbon structured low‐nucleus clusters (LNCs) are successfully anchored on the surface of multiwalled carbon nanotubes (M‐MWCNTs, M = Ni, Co, or Fe) through a foolproof low‐temperature gas transfer (300°C) method without any further treatment. The morphology and coordination configuration of the LNCs at the atomic level were confirmed by comprehensive characterizations. The synthetic Ni‐MWCNTs electrocatalyst features excellent OER activity and stability under alkaline conditions, transcending the performances of Co‐MWCNTs, Fe‐MWCNTs and RuO2. Density functional theory calculations reveal that the moderate oxidation of low‐nucleus Ni clusters changes the unoccupied orbital of Ni atoms, thereby lowering the energy barrier of the OER rate‐limiting step and making the OER process more energy‐efficient. This study demonstrates a novel versatile platform for large‐scale manufacturing of oxygen‐coordinated LNC catalysts.

Microwave-assisted Synthesis of Functionalized Multiwalled Carbon Nanotube–Titanium Dioxide Hybrid Structure and Photodegradation

Decoration of a functionalized multiwalled carbon nanotube (f-MWCNT) surface with titanium dioxide (TiO2) was designed to improve its photocatalytic degradation performance. Structural decoration was achieved by microwave heating at various mass ratios (1:2; 1:4; 1:8; 1:16 wt.%) of titanium (IV) isopropoxide as precursor. The hybrid structure of TiO2/f-MWCNT was characterized by scanning electron microscope and transmission electron microscope (TEM). The crystallite form of the TiO2 nanoparticles was further studied by X-ray diffraction (XRD) and HR–TEM. We report the conformation of high-density TiO2 coated on an f-MWCNT surface at a mass ratio of 1:16 wt.%. XRD analysis revealed a structural transformation from mixture phase (anatase–brookite) at mass ratios of 1:2 and 1:4 wt.% to fully anatase phase for mass ratios of 1:8 and 1:16 wt.%. The transformation was also confirmed by selected area electron diffraction (SAED) and HR–TEM analysis. Our results showed that anatase phase plays a significant role in photodegradation activity.

Excellent Photonic and Mechanical Properties of Macromorphic Fibers Formed by Eu3+-Complex-Anchored, Unzipped, Multiwalled Carbon Nanotubes.

The macromorphic properties of carbon nanotubes perform poorly because of their size limitations: nanosize in diameters and microsize in length. In this work, to realize these dual purposes, we first used an electrochemical method to tear the surface of multiwalled carbon nanotubes (MWCNTs) to anchor photonic Eu3+-complexes there. Through the polar reactive groups endowed by the tearing, the Eu3+-complexes coordinate at the defected structures, obtaining the Eu3+-complex-anchored, unzipped, multiwalled carbon nanotubes (E-uMWCNTs). The controllable surface-breaking retains the MWCNTs’ original, excellent mechanical properties. Then, to obtain the macromorphic structure with infinitely long fibers, a wet-spinning process was applied via the binding of a small quantity of polyvinyl alcohol (PVA). Thus, the wet-spun fibers with high contents of E-uMWCNTs (E-uMWCNT-Fs) were produced, in which the E-uMWCNTs took 33.3 wt%, a high ratio in E-uMWCNT-Fs. On the other hand, due to the reinforcing effect of E-uMWCNTs, the highest tensile strength can reach 228.2 MPa for E-uMWCNT-Fs. Meanwhile, the E-uMWCNT-Fs show high-efficiency photoluminescence and excellent media resistance performance due to the embedding effect of PVA on the E-uMWCNTs. Therefore, E-uMWCNT-Fs can exhibit excellent luminescence properties in aqueous solutions at pH 4~12 and in some high-concentration metal-ion solutions. Those distinguished performances promise outstanding innovations of this work.

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.

Immuno-probed multiwalled carbon nanotube surface for abdominal aortic aneurysm biomarker analysis.

Abdominal aortic aneurysm (AAA), a medical complication, occurs when the aortic area becomes swollen and very large. It is mandatory to identify AAA to avoid the breakdown of aneurysms. C-reactive protein (CRP) has been recognized as one of the biomarkers for identifying AAA due to the possibility of CRP produced in vascular tissue, which contributes to the formation of an aneurysm, and it is elevated in patients with a ruptured AAA. This research work was designed to develop an immunosensor on a multiwalled carbon nanotube (MWCNT)-modified surface to quantify the CRP level. Anti-CRP specificity was constructed on the MWCNT surface through a silane linker to interact with CRP. The detection limit of CRP was calculated as 100 pM with an R2 (determination coefficient) value of 0.9855 (y = 2.3446x - 1.9922) on a linear regression graph. The dose-dependent linear pattern was registered from 200 to 3000 pM and attained the saturation level during binding at 3000 pM. Furthermore, serum-spiked CRP showed a clear increase in the current response, proving the specific recognition of CRP in biological samples. This designed biosensor identifies CRP at a lower level and can help diagnose AAA.