Antimicrobial activity of functionalized single‐walled carbon nanotube with herbal extract of Hempedu bumi

The primary purpose of this study was to determine the antimicrobial activity of functionalized single‐walled carbon nanotube (SWNT) using an extract of the herb, Hempedu bumi. H bumi extract and H bumi extract complexed SWNT were evaluated for biological activities against Bacillus sp., (pathogen) Escherichia coli (opportunistic pathogen), and Aspergillus niger (pathogen). The formation of inhibition zones of these 3 microbes was measured to be evident for the functionalized SWNT with H bumi. Further, morphological and structural analyses were conducted to investigate the functionalized SWNT with H bumi using scanning electron microscopy, atomic force microscopy, X‐ray photoelectron spectroscopy, X‐ray powder diffraction, and Fourier transform infrared spectroscopy, well supporting the intact and crystalline nature of the SWNT. Fourier transform infrared spectroscopy result shows the highest peak at 3371.48 cm⁻¹, representing an andrographolide group from the plant extract. An apparent clear zone has been noticed with SWNT conjugated H bumi extract, displaying a zone of inhibition larger than 1.0 cm against the tested microbes. The results indicate that SWNT has the potential for use as a carrier of components from plant extracts.     

H2 adsorption on Ag‐nanocluster/single‐walled carbon nanotube composites: A molecular dynamics study on the effects of nanocluster size,diameter, and chirality of nanotube

The H₂ physisorption on Ag_N (with N = 32, 108, 256, 500, and 864)/carbon nanotube (CNT; in armchair and zigzag structures with diameters between 0.54 and 2.98 nm) composites were studied by molecular dynamic simulation to investigate the effect of nanocluster size, diameter, and chirality of nanotube on the adsorption phenomena. The calculations indicate that the effects of nanocluster properties are more important than those of the nanotube, in such a way that increase of nanocluster size, decreases the H₂ adsorption. Also, the diameter and chirality of CNTs have considerable influence on the adsorption phenomena. As the diameter of nanotube is increased, the amount of adsorption is decreased. Moreover, H₂ molecules have more tendencies to those nanoclusters located on the armchair nanotubes than the zigzag ones. Another important result is the reversibility of H₂ adsorption on these materials in which the structure of composite in vacuum and after reduction of H₂ pressure to zero, is not changed, considerably. © 2015 Wiley Periodicals, Inc.     

Grafting of aldehyde structures to single‐walled carbon nanotubes for application in phenolic resin‐based composites

Grafting of aldehyde structures to single‐walled carbon nanotubes (SWNTs) has been carried out to endow the nanotubes with appropriate wettability. The results of Fourier transform infrared (FTIR) spectroscopy, ultraviolin‐visible‐near infrared (UV‐VIS‐NIR) spectroscopy, and Raman spectroscopy provide the supporting evidence of aldehyde structures covalently attached to SWNTs. The improved wettability of aldehyde‐functionalized SWNTs (f‐SWNTs) was demonstrated by their good dispersion in organic medium, namely, ethanol and phenolic resin. The prospective covalent bonding between aldehyde structures on the surfaces of f‐SWNTs and phenolic resin makes it possible to prepare an integrated composite with the enhanced‐interfacial adhesion. The f‐SWNT composites, therefore, show much higher average values of dσ/dW_CNT and dE/dW_CNT (i.e., tensile strength and Young's modulus per unit weight fraction) compared with the composites filled with pristine SWNTs or MWNTs. The respective maxima are 9680 MPa and 320 GPa. It is thus feasible for f‐SWNTs to prepare the moderately enhanced but lightweight phenolic composites. Furthermore, the incorporation of f‐SWNTs does not limit the application of phenolic resin as insulation material. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6135–6144, 2009     

Electrocatalytic and selective determination of d‐penicillamine in the presence of tryptophan using a benzoylferrocene‐modified carbon nanotube paste electrode

Two amino acids – d ‐penicillamine (D‐PA) and tryptophan (TRP) – could be simultaneously determined in an aqueous solution (pH 7.0) using a novel benzoylferrocene‐modified carbon nanotube paste electrode. The results indicate that the electrode is efficient in terms of its electrocatalytic activity for the oxidation of D‐PA, leading to an overpotential reduction by more than 155 mV. Using square wave voltammetry, measurement of D‐PA and TRP in one mixture could be done independently from each other with a potential difference of about 205 mV. The proposed electrochemical sensor exhibited a linear calibration plot ranging from 1.0 × 10^?6 to 8.0 × 10^?4 m with a detection limit of 1.3 × 10^?7 m for D‐PA. Finally, the proposed method was applied to the determination of D‐PA in a D‐PA capsule. Copyright © 2012 John Wiley & Sons, Ltd.     

Preparation and characterization of nematic polyazomethine/single‐walled carbon nanotube composites prepared by in situ polymerization

The synthesis and characterization of a series of nematic SWNT‐polyazomethine composites are described. The composites were prepared by in situ polymerization in the presence of 1 wt % of chemically modified SWNTs in such a way that they were either dispersed or covalently bonded to the polymeric matrix. The presence of the SWNTs did not alter the thermal behavior of the polymer matrix and, therefore, highly oriented fibers could be melt‐extruded from the composites at moderate temperatures, as revealed by structural and morphological studies. Preliminary tests on tensile properties indicate that strength and stiffness were improved when compared with fibers without CNTs, particularly when SWNTs were covalently bonded to the polymeric matrix. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2361–2372, 2009     

Preconcentration and analysis of Rhodamine B in water and red wine samples by using magnesium hydroxide/carbon nanotube composites as a solid‐phase extractant

A convenient and accurate analysis approach that combined solid‐phase extraction and high‐performance liquid chromatography was developed to determine the amount of Rhodamine B in red wine and Xiang‐jiang river water samples. A novel composite, magnesium hydroxide/carbon nanotube composites, was synthesized and used as the solid‐phase extractant for the preconcentration/analysis of Rhodamine B. Magnesium hydroxide/carbon nanotube composites, which combined the merits of carbon nanotubes and magnesium hydroxide, exhibited acceptable adsorption and desorption efficiencies for Rhodamine B. The linear range of the proposed solid‐phase extraction with high‐performance liquid chromatography method for Rhodamine B was 0.05–20.0 mg/L, with a limit of detection of 3.6 μg/L. The precision and reproducibility of the developed solid‐phase extraction with high‐performance liquid chromatography method and the batch‐to‐batch reproducibility of the solid‐phase extractant were also validated at spiking levels of 0.5 and 2.0 mg/L. The recovery of Rhodamine B was 94.33–106.7%, and the recovery relative standard deviations of the intra‐ and interday precisions were ≤ 3.83 and ≤ 6.01%, respectively. The relative standard deviation of the batch‐to‐batch reproducibility was ≤ 7.98%.     

Temperature dependence of radiation effects in polyethylene: Cross‐linking and gas evolution

High‐density polyethylene (HDPE) and low‐density polyethylene (LDPE) were irradiated in vacuo at 30–220 and 30–360°C, respectively, with γ‐rays at doses of 10–400 kGy. Temperature dependence of cross‐linking and gas evolution was investigated. It was found that cross‐linking was the predominant process up to 300°C and the gel point decreased smoothly with temperature. The increase of G(x) with temperature was likely attributed to the temperature effect on addition of radicals to the double bonds present in the polymer. Above 300°C, the gel fraction at a given dose decreased remarkably with temperature and turned to zero at 360°C. The molecular weight variation determined with gel permeation chromatography (GPC) indicated the enhanced degradation at 360°C by radiation. G‐values of H₂ increased with temperature and varied with dose. The compositions of the C₁–C₄ hydrocarbons evolved depended on the structures of side branches. Raising the temperature favored the formation of unsaturated hydrocarbons, and the yield of unsaturated relative to saturated hydrocarbons decreased with dose. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1541–1548, 1999     

Electron smearing in DFT calculations: A case study of doxorubicin interaction with single‐walled carbon nanotubes

To address the choice of an appropriate value of electron smearing to facilitate self‐consistent field (SCF) convergence, we studied the interaction of doxorubicin with short armchair and zigzag single‐walled carbon nanotube models with closed caps, at the PWC/DNP level of density functional theory. By gradually reducing the electron smearing value from a large and most commonly used one of 0.005 Ha to zero (Fermi occupation), we monitored the changes in close contacts between the interacting species, total energy of the molecular system, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy and isosurfaces, HOMO‐LUMO gap energy, and plots of electrostatic potential. It became evident that the commonly used smearing values of ≥0.001 Ha can alter the results significantly (for example, by one order of magnitude for HOMO–LUMO gap energy). We suggest the setting of electron smearing value at 0.0001 Ha, which does not imply too high computation cost and can guarantee the results close to the ones obtained with Fermi occupation. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Temperature effects on spreading of water nano‐droplet on poly(methyl methacrylate): A molecular dynamics simulation study

In this article, the effect of temperature on the spreading behavior of a water nano‐droplet on poly(methyl methacrylate) substrate is investigated. The contact angle analysis illustrates that the spreading process occurs in a stage‐like manner and the increase in temperature causes a regime change from partial to total wetting. The interaction energy distributions show that there exist sites on the surface which could trap water molecules and provide a better path for other molecules to overcome the asperities. Estimations of the coefficients of self‐diffusivity suggest that temperature has a major effect in the reorientation stage, which results in the formation of the interfacial layer. In the second stage of spreading, temperature affects the process by providing sufficient energy for water molecules to overcome the interactions with the substrate. Therefore, this stage is controlled by the movement of water molecules on the surface and is highly influenced by their interaction with the surface asperities, strong interaction sites, and the carbonyl groups. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1532–1541