The Adhesion and Diffusion of Saturate, Asphaltene, Resin and Aromatic (SARA) Molecules on Oxygenated and Hydrogenated Carbon Nanotubes (CNTs)

The interfacial adhesion between asphalt binder and carbon nanotubes (CNTs) depends on many nanoscopic properties such as diffusion of SARA molecules on CNTs surface. Functionalization of CNTs with Oxygens (O=CNTs), hydroxyl groups (HO–CNTs), and hydrogens (H–CNTs) has been an effective way to modify the surface properties of CNTs and ultimately the macroscopic properties of the CNT-composites. This paper presents the effect of different dosages of oxygenated and hydrogenated CNTs on the adhesion and diffusion of SARA molecules on CNTs’ surfaces. First, reactive molecular dynamics simulation is used to oxygenate and hydrogenate CNTs up to a certain dosage. Next, it is employed to model the interaction and diffusion of SARA molecules with the functionalized CNTs. We employ the steer molecular dynamic (SMD) and Einstein formula to calculate the adhesion and diffusion properties. The results demonstrate that hydrogenation has little effect on the adhesion energy, while oxygenation can increase adhesion energy up to 100% for 25% dosage. The diffusion coefficient dramatically drops for both oxygenated and hydrogenated CNTs, with lower values for the latter. We observe that for hydrogenated and oxygenated CNTs at different dosages, asphaltene, resin, aromatic, and saturate molecules have the highest to lowest values, respectively.

Low Kinetic Energy Oxygen Ion Irradiation of Vertically Aligned Carbon Nanotubes

Vertically aligned multiwalled carbon nanotubes (v-CNTs) were functionalized with oxygen groups using low kinetic energy oxygen ion irradiation. X-ray photoelectron spectroscopy (XPS) analysis indicates that oxygen ion irradiation produces three different types of oxygen functional groups at the CNTs surface: epoxide, carbonyl and carboxyl groups. The relative concentration of these groups depends on the parameters used for oxygen ion irradiation. Scanning electron microscopy (SEM) shows that the macroscopic structure and alignment of v-CNTS are not affected by the ion irradiation and transmission electron microscopy (TEM) proves tip functionalization of v-CNTs. We observed that in comparison to oxygen plasma treatment, oxygen ion irradiation shows higher functionalization efficiency and versatility. Ion irradiation leads to higher amount of oxygen grafting at the v-CNTs surface, besides different functional groups and their relative concentration can be tuned varying the irradiation parameters.

Abnormal Anionic Porphyrin Sensing Effect for HER2 Gene Related DNA Detection via Impedance Difference between MWCNTs and Single-Stranded DNA or Double-Stranded DNA

Human epidermal growth factor receptor 2 (HER2) is a key tumor marker for several common and deadly cancers. It is of great importance to develop efficient detection methods for its over-expression. In this work, an electrochemical impedance spectroscopy (EIS) method adjustable by anionic porphyrin for HER2 gene detection has been proposed, based on the impedance difference between multi-walled carbon nanotubes (MWCNTs) and DNA. The interesting finding herein is that with the addition of anionic porphyrin, i.e., meso-tetra(4-sulfophenyl)-porphyrin (TSPP), the impedance value obtained at a glass carbon electrode (GCE) modified with MWCNTs and a single stranded DNA (ssDNA), the probe DNA that might be assembled tightly onto MWCNTs through π-π stacking interaction, gets a slight decrease; however, the impedance value from a GCE modified with MWCNTs and a double stranded DNA (dsDNA), the hybrid of the probe DNA with a target DNA, which might be assembled loosely onto MWCNTs for the screening effect of phosphate backbones in dsDNA, gets an obvious decrease. The reason may be that on the one hand, being rich in negative sulfonate groups, TSPP will try to push DNA far away from CNTs surface due to its strong electrostatic repulsion towards DNA; on the other hand, rich in planar phenyl or pyrrole rings, TSPP will compete with DNA for the surface of CNTs since it can also be assembled onto CNTs through conjugative interactions. In this way, the “loosely assembled” dsDNA will be repelled by this anionic porphyrin and released off CNTs surface much more than the “tightly assembled” ssDNA, leading to a bigger difference in the impedance value between dsDNA and ssDNA. Thus, through the amplification effect of TSPP on the impedance difference, the perfectly matched target DNA could be easily determined by EIS without any label. Under the optimized experimental conditions, this electrochemical sensor shows an excellent linear response to target DNA in a concentration range of 2.0 × 10−11–2.0 × 10−6 M with a limit of detection (LOD) of 6.34 × 10−11 M (S/N = 3). This abnormally sensitive electrochemical sensing performance resulting from anionic porphyrin for DNA sequences specific to HER2 gene will offer considerable promise for tumor diagnosis and treatment.

Preparation and Characterization of Carbon Nanotubes/Al2O3 Inorganic Hybrid Material - A Bio-Inspired Poly(Dopamine) Approach

Carbon nanotubes/alumina (CNTs/Al2O3) nanocomposites were prepared by the poly (dopamine) assisted chemical liquid phase deposition (CLPD). The poly (dopamine) layers were firstly coated on the CNTs surface uniformly by the self-oxidative polymerization of dopamine in mild aqueous solution and then the Al2O3 nanoparticles formed on the poly (dopamine) coated CNTs surface by the CLPD. The hydrophilic poly (dopamine) layers on the CNTs surface can improve the dispersion of CNTs in aqueous solution. Moreover, it can be used as a key linker between the CNTs and Al2O3 because of the nitrogen-containing group in poly (dopamine) could coordinate with Al3+ ions. The as-prepared poly (dopamine) coated CNTs and CNTs/Al2O3 nanohybrids were characterized by X-ray photoelectron spectroscopy (XPS), X-radial diffractometer (XRD) and high resolution transmission electron microscopy (HRTEM). These results showed that the poly (dopamine) layers were coated on the surface of CNTs uniformly, and the Al2O3 nanoparticles embellished with the poly (dopamine) coated CNTs surface. Compared with pristine NR composites, the thermal conductivity of the as-prepared NR/CNTs@Al2O3 composites increased 17%.

REMOVAL OF O,M,P-XYLENE FROM AIR SAMPLES ON OXIDIZED CARBON NANOTUBES CARTRIDGES

Carbon nanotubes (CNTs) have been considered as an excellent adsorbent in environmental engineering, especially for treatment of volatile organic compounds (VOCs). The paper presents a new approach for the selective adsorption of Xylene isomers from air samples using nanomaterial based on oxidized multiwalled carbon nanotubes. In the first study, the functionalization of two oxidized MWCNTs was achieved with hydrogen peroxide and sodium hypochlorite. The characterization of functionalized CNTs (CNT-NaOCl, CNT-H2O2) was performed by Fourier transform infrared spectroscopy (FT-IR) and X-Ray diffractometer (XRD). Afterthat, the applications of pristine CNTs and oxidized CNTs for removal of three Xylene isomers from air samples were discussed. The results demonstrate that the correlation of CNTs and three isomers was significantly different with an affinity order o-Xylene > m-Xylene > p-Xylene. The oxidized CNTs with carbonyl groups increased significantly its adsorption capacity for these isomers. A comparison in term of adsorption performance shows that the framework distinguishes among these adsorbents due to the dispersive properties and the electrostatic interaction between the Xylene isomers and oxidized CNTs surface.