Quantification Of Multiwall Carbon Nanotubes Research Articles

Quantification of MWCNTs incorporated into PBTh matrix composite obtained by electrochemical polymerization and their effect on the conductive properties and structure

This paper describes the use of elemental combustion analysis for the simple quantification of multiwalled carbon nanotubes (MWCNT’s) inside a composite of polybithiophene (PBTh) matrix obtained by electrochemical polymerization. The obtained percentage in weight of MWCNT’s inside PBTh composites prepared was found between 15 % and 32 % depending on the different electropolymerization scan rates and CNTs proportion present at the polymerization solution. PBTh and PBTh/MWCNT composite properties were evaluated by in-situ electrochemical conductance method. The presence of the MWCNT’s causes a decrease in the hysteresis value (ΔEG ≈ 100 mV), and a faster charge exchange mainly in the charged-discharged transition, improving the conducting and electron transfer properties. Atomic force microscopy (AFM) scanning electronic microscopy (SEM) and X-ray diffraction (XRD) analysis let to distinguish unambiguously the presence of CNT’s and in the composite a nano fibrous structure was observed, which may explain the improvement of the electrochemical properties.

Development of a Novel Shallow Liquid Interface Exposure System for MWCNT Toxicity Assessment.

Increasing applications of multiwalled carbon nanotubes (MWCNT) lead to significant occupational exposure and potential health concerns. Toxicity of MWCNT should be carefully elucidated since the conventional (CON) method with fully immersed condition fails to mimic the air-liquid interface (ALI) in airways. Additionally, quantification of MWCNT in cells was a real challenge. Currently available ALI exposure devices are costly, posing problems to conducting in vitro evaluations for emerging nanomaterials. A novel system, consisting of a shaker fluidized-bed atomizer (SFA) and electrostatic shallow liquid interface (ESLI) exposure chamber, has been developed for investigating nanotoxicity of well-dispersed pristine-MWCNT (pMWCNT) and carboxylized-MWCNT (cMWCNT). After 24-h exposure, LDH, MCP-1, IL-1β, IL-6, and TNF-α releases were determined, and cell uptakes were quantified according to the molybdenum content in cells. Biological responses triggered by SLI exposure are obviously more sensitive compared with those caused by CON exposure at equivalent doses. Exposure dose-dependent release of LDH and IL-6 was highlighted in A549 cells, indicating higher cytotoxicity and inflammatory responses of cMWCNT attributed to its shorter length, smaller size, and higher cell uptake. Cell-associated dose-dependent release of LDH and IL-6 was highlighted in RAW264.7 cells, revealing the higher adverse health risk of pMWCNT due to frustrated phagocytosis and its much higher molybdenum content. These results suggest that inherent characteristics of cells and distinct physicochemical properties of pMWCNT and cMWCNT lead to either exposure dose-dependent or cell-associated dose-dependent responses. Notably, the SLI is superior to the CON exposure method and well suited for nanotoxicity assessment of different MWCNTs.

Rapid and versatile pre-treatment for quantification of multi-walled carbon nanotubes in the environment using microwave-induced heating

The concerns regarding potential environmental release and ecological risks of multi-walled carbon nanotubes (MWCNTs) rise with their increased production and use. As a result, there is the need for an analytical method to determine the environmental concentration of MWCNTs. Although several methods have been demonstrated for the quantification of well-characterized MWCNTs, applying these methods to field samples is still a challenge due to interferences from unknown characteristics of MWCNTs and environmental media. To bridge this gap, a recently developed microwave-induced heating method was investigated for the quantification of MWCNTs in field samples. Our results indicated that the microwave response of MWCNTs was independent of the sources, length, and diameter of MWCNTs; however, the aggregated MWCNTs were not able to convert the microwave energy to heat, making the method inapplicable. Thus, a pre-treatment process for dispersing bundled MWCNTs in field samples was crucial for the use of the microwave method. In the present paper, a two-step pre-treatment procedure was proposed: the aggregated MWCNTs loaded environmental samples were first exposed to high temperature (500°C) and then dispersed by using an acetone-surfactant solution. A validation study was performed to evaluate the effectiveness of the pre-treatment process, showing that an 80-120% recovery range of true MWCNT loading successfully covered the microwave-measured MWCNT mass.

Emerging investigator series: quantification of multiwall carbon nanotubes in plant tissues with spectroscopic analysis

A rapid widely accessible spectroscopic analysis was developed for quantification of carbon nanotubes in plant tissues.

Digestion Coupled with Programmed Thermal Analysis for Quantification of Multiwall Carbon Nanotubes in Plant Tissues

The rapidly growing application of carbon nanotubes (CNTs) for industry and consumer products will inevitably lead to their accumulation in the environment. Protection of food safety from contamination by CNTs and best-practice management of agricultural application of CNTs require quantification of CNTs in agricultural plants. Herein, a novel method of digestion coupled with programmed thermal analysis (PTA) was developed for quantitative analysis of multiwall CNTs (MWCNTs) in plant (lettuce) tissues. MWCNT-bound carbon was linearly correlated with elemental carbon (EC) detected by PTA, including EC1 (58.5%) (evolved at 580 °C) and EC2 (41.5%) (evolved at 740 °C), corresponding to less stable and stable carbon, respectively. The background plant materials could interfere with EC quantification of CNTs, as a substantial fraction of the plant biomass was charred during the thermal analysis. Sequential digestion with concentrated nitric acid (HNO3) and sulfuric acid (H2SO4) effectively minimized the interference caused by the lettuce tissues, reducing the background EC generated from leaf tissues to 10.73 ± 10.26 μg of C/g. Via the coupling of digestion with PTA, a detection limit of 64.9 μg of CNT-C/g of plant tissues was achieved. This method can be applied for unambiguous quantification of CNTs in plant tissues at low concentrations and provide critical information for evaluating the risk of exposure to CNTs through crops and optimizing applications of CNTs in agriculture.

Capabilities of asymmetric flow field-flow fractionation coupled to multi-angle light scattering to detect carbon nanotubes in soot and soil

Analytical detection and quantification of multi-walled carbon nanotubes (MWCNTs) in complex matrices such as soils is very challenging. In an initial approach to this task, we identify MWCNTs by making use of their different (e.g., rod-like) shape compared to other (native) soil particles and in particular soot, which is ubiquitously present in soils. A shape factor ρ, determined using asymmetric flow field-flow fractionation coupled to multi-angle light scattering (aF4-MALS), was used to discriminate MWCNTs of different aspect ratios, as well as mixtures of soot and MWCNTs, in pure suspensions. MALS results were additionally confirmed using automated electron microscopy image analysis. We then analyzed different soil types which consistently showed ρ-values that differed from pure MWCNTs. To test the performance of the method for MWCNT detection in such complex matrices, we conducted standard additions of a MWCNT as well as soot to an agricultural soil. Extracts from these MWCNT-spiked soils showed increased ρ-values compared to soot-spiked or native soil. The method detection limit for the MWCNT was 1.6 to 4.0 mg g−1 soil and lies within the range of commonly used black carbon quantification methods, but is much higher than any currently predicted environmental concentration. Additionally, the method is currently limited by a relatively narrow dynamic range of ρ. Despite these limitations, our results suggest that aF4-MALS provides specific shape information that may be linked to an actual MWCNT presence in soils. Further method improvement potential is outlined along different steps of the workflow.