The improvement in interfacial shear strength of wood fiber/epoxy composite by sizing with epoxy sizing agent containing MWCNTs

This paper discloses a feasible and high efficient strategy for wood fiber treatment to introducing multi‐wall carbon nanotubes (MWCNTs) to the surface of wood fibers for the aim of improving the interfacial shear strength of wood fiber/epoxy composite. Briefly, a layer of MWCNT was deposited on wood fibers through sizing wood fibers with epoxy sizing agent containing amine‐treated MWCNTs (MWCNT‐PEI). The surface functional groups, morphology, wettability, and interphase properties of MWCNTs on the surface of wood fiber were studied. The remarkable enhancements were achieved in interfacial shear strength of reinforced composites by dipping wood fiber in MWCNTCOOH suspension and wood fiber sizing containing MWCNT‐PEI.     

Darcy–Forchheimer 3D flow of carbon nanotubes with homogeneous and heterogeneous reactions

This article deals with Darcy–Forchheimer three dimensional (3D) flow of water-based carbon nanotubes (CNTs) with heterogeneous–homogeneous reactions. A bidirectional nonlinear extendable surface has been employed to create the flow. Flow in porous space is represented by Darcy–Forchheimer expression. Heat transfer mechanism is explored through convective heating. Equal diffusion coefficients are considered for both auto catalyst and reactants. Results for single-wall (SWCNT) and multi-wall (MWCNT) carbon nanotubes have been presented and compared. The diminishment of partial differential framework into nonlinear ordinary differential framework is made through suitable transformations. Optimal homotopy scheme is used for arrangements development of governing flow problem. Optimal homotopic solution expressions for velocities and temperature are studied through plots by considering various estimations of physical variables. Moreover the surface drag coefficients and heat transfer rate are analyzed through plots.     

Electrocatalytic Determination of Hydrazine and Phenol Using a Carbon Paste Electrode Modified with Ionic Liquids and Magnetic Core‐shell Fe3O4@SiO2/MWCNT Nanocomposite

A carbon paste electrode was modified with 2‐(4‐Oxo‐3‐phenyl‐3,4‐dihydroquinazolinyl)‐N′‐phenyl‐hydrazinecarbothioamide, magnetic core? shell Fe₃O₄@SiO₂/MWCNT nanocomposite and ionic liquid (n‐hexyl‐3‐methylimidazolium hexafluoro phosphate). The electro‐oxidation of hydrazine at the surface of the modified electrode was studied using electrochemical approaches. This modified electrode offers a considerable improvement in voltammetric sensitivity toward hydrazine, compared to the bare electrode. Square wave voltammetry (SWV) exhibits a linear dynamic range from 7.0×10^?8 to 5.0×10^?4 M and a detection limit of 40.0 nM for hydrazine. The diffusion coefficient and kinetic parameters (such as electron transfer coefficient and the heterogeneous rate constant) for hydrazine oxidation were also determined. The prepared modified electrode exhibits a very good resolution between the voltammetric peaks of hydrazine and phenol that makes it suitable for the detection of hydrazine in the presence of phenol in real samples.     

The defluoridation of drinking water using multi-walled carbon nanotubes

In this study, the potential sorption capacity of multi-walled carbon nanotubes (MWCNTs) was investigated as a means of removing fluoride from the drinking water of a number of regions in Iran and from experimental solutions. The test was conducted in both batch and continuous operation modes. Batch mode experiments were used to study the effect of parameters such as pH, contact time, ionic strength, adsorbent dose, adsorbent capacity, and the presence of foreign anions on the efficiency of fluoride removal. The results showed that the highest level of sorption occurs at pH 5 (about 94% at 18 min). The ionic strength of the solutions and the presence of co-anions such as chloride, nitrate, sulfate, hydrogen carbonate, perchlorate had a negligible effect on the sorption of F⁻ onto MWCNTs. Sorption capacity measurements revealed that MWCNTs have a saturation capacity of 3.5 mg of F⁻ per gram. Sorption data were best fitted with the Fruendlich sorption isotherm equation, which indicates that F⁻ tends to be adsorbed on MWCNTs in a multilayered manner. Experiments using Kohbanan city drinking water, which contains the highest level of F⁻ among the drinking water samples studied, showed that MWCNTs can remove over 85% of fluoride content.     

Novel Sensing Assembly Comprising Engineered Gold Dendrites and MWCNT‐AuNPs Nanohybrid for Acetaminophen Detection in Human Urine

A layered nanohybrid comprising of multi walled carbon nanotubes(MWCNT)‐gold nanoparticles (AuNPs) has been designed as a matrix for the development of Au dendritic nanostructures (AuDN) with enhanced catalytic activity. The developed sensor matrix was thoroughly characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), and energy dispersive X‐ray spectroscopy (EDX). The developed sensor probe MWCNT‐AuNPs/AuDN over glassy carbon electrode (GCE) was used for the label free detection of acetaminophen (AP), a commonly used drug associated with hepatotoxicity when overdosed, as a model molecule. The final sensor probe was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and differential pulse voltammetry (DPV). The sensor shows excellent analytical performances with a linear dynamic range (LDR) of 100 to 7500 nM, and a low limit of detection (LOD) of 2.12 (±0.03) nM, which is better than recently reported AP sensors. The practical application / clinical possibilities of the final sensor were evaluated by real sample analysis in human urine by spike and recovery method, where the AP recoveries were found in between 92 % to 96 %. The sensor probe shows negligible response towards co‐existing interfering molecules like glucose, urea, uric acid and various amino acids, which are commonly found in real samples (p<0.001, n=3). The shelf life of the sensor probe was evaluated and found to be stable for 8 weeks. The fabricated sensor probe using MWCNT‐AuNPs/AuDN is easy to fabricate, simple, robust, and able to detect AP in urine with high recoveries shows its possibilities to be used in clinical settings.     

Improved Catalytic Performance of Pt Supported on Multi‐Wall Carbon Nanotubes as Cathode for Direct Methanol Fuel Cell Applications Prepared by Dual‐Stepped Surface Thiolation Processes

This study develops a simple surface modification process for modifying the MWCNT surface by thiolation reaction after the conventional nitric acid treatment for strong interface attachment of Pt NPs and improved dispersion onto MWCNTs. The thiolated MWCNTs (Pt/MWCNTs) showed significant improvement of methanol electro‐oxidation activity compared with that treated only by nitric acid solution. The prepared electrode with thiolated MWCNTs was used as the cathode for assembling MEA for DMFC single‐cell applications. Testing results indicate that the thiolated MWCNT cathode can improve the power density of MEA by more than 300% (from 4.6 to 20.6 mW cm^?2) compared with that treated only by conventional nitric acid reactions. The dual‐step modification process for MWCNT surface treatment showed significant improvement over the convention nitric acid treatment and can be successfully used in DMFC applications.     

Characterisation of carbonaceous materials using Raman spectroscopy: a comparison of carbon nanotube filters,single‐ and multi‐walled nanotubes,graphitised porous carbon and graphite

Multi‐walled carbon nanotube (MWCNT) filters have been recently synthesised which have specific molecular filtering capabilities and good mechanical strength. Optical and scanning electron microscopy (SEM) reveals the formation of highly aligned arrays of bundles of carbon nanotubes having lengths up to 500 µm. The Raman spectra of this material along with four other carbonaceous materials, commercially available single‐walled carbon nanotubes (SWCNTs) and MWCNTs, graphitised porous carbon (Carbotrap) and graphite have been recorded using two‐excitation wavelengths, 532 and 785 nm, and analysed for band positions and shape with special emphasis paid to the D‐, G‐ and G′‐bands. A major difference between the different MWCNT varieties analysed is that G‐bands in the MWCNT filters exhibit almost no dispersion, whereas the other MWCNTs show a noticeable dispersive behaviour with a change in the excitation wavelength. Spectral features similar to those of the MWCNT filter varieties were observed for the Carbotrap material. From the line shape analysis, the intensity ratio, I_D/I_G, of the more ordered MWCNT filter material using the integral G‐band turns out to be two times lower than that of the less ordered MWCNT filter product at both excitation wavelengths. This parameter can, therefore, be used as a measure of the degree of MWCNT alignment in filter varieties, which is well supported also by our SEM study. Copyright © 2008 John Wiley & Sons, Ltd.     

Thiazoline-Iridium (III) Complexes and Immobilized Nanomaterials as Selective Catalysts in N-Alkylation of Amines with Alcohols

In this research, a new series of thiazoline-iridium (III) complexes ( 4 – 7 ) derived from cysteine were prepared and fully characterized by conventional methods. The molecular structure of complex 5 was also determined by single-crystal X-ray diffraction. These complexes were evaluated as catalysts for hydrogen-borrowing reactions of amines with alcohols. In particular, complex 5 showed the best activity as catalyst. Various amines have been alkylated with alcohols affording moderate to good yield (33–99%). Moreover, the immobilized nanomaterials ( M _1,2 ) were fabricated by sonication process from the best catalyst 5 with the multi-walled carbon nanotubes (MWCNTs) and graphene oxide (GO), respectively, and characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) spectroscopy, and inductively coupled plasma-mass spectrometry (ICP-MS). The M _1,2 nanomaterials were also tested as catalysts in model catalytic reaction for N-alkylation. The M ₁ nanomaterial showed significantly higher activity than the M ₂ nanomaterial. The M ₁ catalyst was recovered by filtration and reused for four catalytic cycles with high conversion (99%, 97%, 96%, and 86%).     

Multi‐Walled Carbon Nanotubes (MWCNT)‐Ionic Liquid‐Modified Carbon Paste Electrode: Probing FurazolidoneDNA Interactions and DNA Determination

The interactions of furazolidone (Fu) with double‐stranded calf thymus DNA (dsDNA) on the multi‐walled carbon nanotubes‐ionic liquid‐modified carbon paste electrode (MWCNT‐IL‐CPE) have been studied by cyclic voltammetry. In the presence of DNA, the cathodic peak current of Fu decreased and the peak potential shifted to a positive potential, indicating the intercalative interaction of Fu with DNA. The binding constant of Fu with DNA and stoichiometric coefficient has been determined according to the Hill's model. This electrochemical method was further applied to the determination of DNA. Two linear calibration curves were obtained for DNA detection in the concentration ranges of 0.03–0.10 and 0.10–4.0 μg l^?1 with a detection limit of 0.027 μg l^?1. The method was successfully applied to analyze Fu in serum samples.