Capability Of Single-walled Carbon Nanotubes Research Articles

Comparison between the Effect of multi-walled carbon nanotubes and single walled carbon nanotubes in removing pb and cd in contaminated bio medical ash

Heavy metal contamination is a highly significant environmental issue. Primarily, this current study is focusing the application of developing Nano technologies which have capacity to remove or reduce toxins from the environment. The extraction and preconcentration abilities of both types of carbon nanotubes, multi-walled (MWCNTs) and single-walled (SWCNTs), were accomplished by using water-acid, acetate, and deghassed water acid EDTA solutions from neuteuche semi-total solid extract from anthropogenic and naturally in origine samples. The results of the study indicated that the adsorption rate was even faster when the solution temperatures were higher in both types of adsorbents. These increases were greater when multi-walled carbon was used. This may be due to the fact that in endothermic nature of adsorption the increase in temperature leads to a faster rate of adsorption. In order to understand the kinetics of Cadmium (II) and Lead(II) adsorption, analysis was executed utilizing the fractional power function model and Lagergren pseudo-first-order and pseudo-second-order methods. A pseudo-second-order model well described the adsorption kinetics of heavy metal ions onto both bioadsorbents. For both biosorbents, the adsorption capacity increased as the solution was heated. The percentage of Pb adsorbed on ultra-sonically assisted MWCNTs was 7.93%, for MWCNTs= 8.33%, 73.50% for swCNTs and 92.46% for amine-MWCNTs (Table 2). Similarly, the percentage of Cd adsorbed on ultra-sonically assisted MWCNTs was 67.92%, 29.30% for MWCNTs, 6.30% for swCNTs and 2.27% for amine-MWCNTs. As far as SWCNTs, they provided some interesting results in terms of adsorption capacity. For example, the adsorption capacity with respect to Pb was about 6.53% with SWCNTs 1, about 7.12% with SWCNTs 2, about 61.33% with SWCNTs 3, and about 79.31% with SWCNTs 4. Similarly, for Cd it was about 61.32% with SWCNTs 1, about 27.13% with SWCNTs 2, about 5.88% with SWCNTs 3, and about 1.53% with SWCNTs 4. The elution tests for single-walled carbon nanotubes and multiwalled carbon nanotubes have been carried out and the results have been shown as binding isotherms and pH effects in Figures 3 and 4. For the study of the adsorption capability of single-walled carbon nanotubes for metal ions, same order of binding to the metal ions has been observed for both the types of the carbon nanotubes-studied, lead (II) < cadmium (II). For multi-walled carbon nanotubes, however, the binding of metal ions was found to depend on the carbon nanotubes type and the binding order, as for carbon nanotubes, were found to be, lead (II) > cadmium (II). Nanotechnologies have facilitated the ability of researchers to address challenges more effectively. This research focuses on the development of Nanotechnologies for the purpose of remediating heavy metals, including cadmium and lead. These metals are considered highly toxic and require urgent attention.

Predictions of elastic properties of reinforced polymers accounting for the agglomeration of fillers

A micromechanics model for the prediction of elastic properties of reinforced polymers taking into account the agglomeration of fillers is developed. The influence of the shape of fillers on the results is discussed on the basis of a model developed earlier (Tandon and Weng in Compos. Sci. Technol. 27:111–132, 1986). The analysis is extended further for the consideration of possible agglomeration of fillers, and a micro-structure parameter \(\eta \) is accordingly introduced for its characterization. The values of the \(\eta \)-parameter are in the interval from zero to unity; higher value of \(\eta \) implies a greater degree of agglomeration of fillers. The applications of the model to some polymers reinforced with single-walled carbon nanotubes (SWNTs) are discussed; theoretical predictions are compared with experimental and numerical results available in the literature. It is concluded that the \(\eta \)-parameter increases with the volume fraction of fillers in current fabrication processes, and the agglomeration of fillers renders the reduction of the stiffness-enhancement capability of SWNTs.

Ultrasensitive detection of lead (II) based on fluorescent aptamer-functionalized carbon nanotubes

Lead contamination is a serious environmental problem with toxic effects in human. Here, we developed a simple and sensitive sensing method employing ATTO 647N/aptamer-SWNT ensemble for detection of Pb2+. This method is based on the super quenching capability of single-walled carbon nanotubes (SWNTs), high affinity of the aptamer toward Pb2+ and different propensities of ATTO 647N-aptamer and ATTO 647N-aptamer/Pb2+ complex for adsorption on SWNTs. In the absence of Pb2+, the fluorescence of ATTO 647N-aptamer is efficiently quenched by SWNTs. Upon addition of Pb2+, the aptamer binds to its target, leading to the formation of a G-quadruplex/Pb2+ complex and does not interact with SWNTs and ATTO 647N-aptamer starts fluorescing. This sensor exhibited a high selectivity toward Pb2+ and a limit of detection (LOD) as low as 0.42nM was obtained. Also this sensor could be applied for detection of Pb2+ ions in tap water and biological sample like serum with high sensitivity.

Combing DNAzyme with single-walled carbon nanotubes for detection of Pb(ii) in water

A sensitive and simple assay for the detection of Pb(2+) in aqueous solutions is reported. It takes advantage of the high affinity between single-stranded DNA (ssDNA) and single-walled carbon nanotubes (SWCNT) as well as the capability of SWCNT in fluorescence quenching. Lead(II) catalyzes the cleavage of a fluorescently labeled DNA substrate by a DNAzyme, which releases the single-stranded product to be adsorbed onto a SWCNT. The decrease in fluorescence is proportional to the Pb(2+) concentration. Concentrations as low as 1 nM Pb(2+) in water could be detected and the detection range spans over 5 orders of magnitude. The unique combination of Pb-specific DNAzyme with SWCNT produces a universal, facile and cost-effective sensing platform for lead ions. The concept can be applied to the design of detection assays for other metal ions or small molecules.

Effect of Different Functional Groups on the Free Radical Scavenging Capability of Single-Walled Carbon Nanotubes

The effect of different functional groups on the free radical scavenging capability of single-walled carbon nanotubes (SWCNT) is investigated using density functional theory calculations. The reaction mechanism that is considered in this study is the radical adduct formation. The reactions of a •OH radical with eight different functionalized SWCNTs (armchair and zigzag) were studied. All of them were found to be exothermic and exergonic. Different sites of reaction were considered, and the increase on reactivity with respect to pristine tubes was found to be site-dependent. The presence of functional groups on the sidewalls of SWCNTs is predicted to increase their OH radicals scavenging activity. To enhance this property, the best functional groups are −CH2−OH for the armchair (3,3) SWCNT and −CONH−CH3 for the zigzag (5,0) fragment. The major conclusion from this work is that functionalized SWCNTs, in addition to be soluble in different media, are also very good free radical scavengers, being the armchair...

Influence of Point Defects on the Free-Radical Scavenging Capability of Single-Walled Carbon Nanotubes

The effect of point defects on the free-radical scavenging activity of armchair and zigzag single-walled carbon nanotubes (SWCNTs), through a radical adduct formation mechanism, has been studied using density functional theory calculations. SWCNTs with different vacancy (V), adatom (AA), and Stone−Wales (SW) defects have been considered, as well as their pristine partners. All the studied reactions were found to be significantly exothermic and exergonic, which supports their viability. The presence of point defects in the carbon lattice of SWCNTs is predicted to increase their free-radical scavenging activity. The AA and V point defects, involving C atoms with dangling bonds, are expected to cause a larger increase on the SWCNTs’ reactivity toward free radicals than the SW and vacancy defects without C atoms with dangling bonds. The studied Stone−Wales point defect shows the largest site-dependent effect on the free-radical scavenging activity of SWCNTs. The presence of nonpolar environments is not expected to change the proposed trends. Characteristic infrared bands in the 3300 and 900−1100 cm−1 regions have been assigned to the νO−H and νC−O vibrations of the OH radical adducts.

I-Motif Quadruplex DNA-Based Biosensor for Distinguishing Single- and Multiwalled Carbon Nanotubes

The increasing worldwide demand for carbon nanotubes (CNTs) and increasing concern regarding how to safely develop and use CNTs are requiring a low-cost, simple, and highly sensitive CNT detection assay for toxicological evaluation and environmental monitoring. However, this goal is still far from being achieved. All the current CNT detection techniques are not applicable for automation and field analysis because they are dependent on highly expensive special instruments and complicated sample preparation. On the basis of the capability of single-walled carbon nanotubes (SWNTs) to specifically induce human telomeric i-motif formation, we design an electrochemical DNA (E-DNA) sensor that can distinguish single- and multiwalled carbon nanotubes both in buffer and in cell extracts. The E-DNA sensor can selectively detect SWNTs with a direct detection limit of 0.2 ppm and has been demonstrated in cancer cell extracts. To the best of our knowledge, this is the first demonstration of a biosensing technique that can distinguish different types of nanotubes. Our work will provide new insights into how to design a biosensor for detection of carbon nanotubes.

Carbon Nanotubes as Molecular Transporters for Walled Plant Cells

We have investigated the capability of single-walled carbon nanotubes (SWNTs) to penetrate the cell wall and cell membrane of intact plant cells. Confocal fluorescence images revealed the cellular uptake of both SWNT/fluorescein isothiocyanate and SWNT/DNA conjugates, demonstrating that SWNTs also hold great promise as nanotransporters for walled plant cells. Moreover, the result suggested that SWNTs could deliver different cargoes into different plant cell organelles.