Dispersion of Carbon Nanotubes with “Green” Detergents

Solubilization of carbon nanotubes (CNTs) is a fundamental technique for the use of CNTs and their conjugates as nanodevices and nanobiodevices. In this work, we demonstrate the preparation of CNT suspensions with “green” detergents made from coconuts and bamboo as fundamental research in CNT nanotechnology. Single-walled CNTs (SWNTs) with a few carboxylic acid groups (3–5%) and pristine multi-walled CNTs (MWNTs) were mixed in each detergent solution and sonicated with a bath-type sonicator. The prepared suspensions were characterized using absorbance spectroscopy, scanning electron microscopy, and Raman spectroscopy. Among the eight combinations of CNTs and detergents (two types of CNTs and four detergents, including sodium dodecyl sulfate (SDS) as the standard), SWNTs/MWNTs were well dispersed in all combinations except the combination of the MWNTs and the bamboo detergent. The stability of the suspensions prepared with coconut detergents was better than that prepared with SDS. Because the efficiency of the bamboo detergents against the MWNTs differed significantly from that against the SWNTs, the natural detergent might be useful for separating CNTs. Our results revealed that the use of the “green” detergents had the advantage of dispersing CNTs as well as SDS.

Sessile droplets containing carbon nanotubes: a study of evaporation dynamics and CNT alignment for printed electronics

A study of evaporation dynamics of the CNT suspensions and CNT alignment via sessile drop experiments on a flexible substrate.

Effects of Various Carbon Nanotube Suspensions on A549, THP-1, and Peritoneal Macrophage Cells

The effects of iron content, fiber length, and stability of carbon nanotube (CNT) suspension on cells were examined. Five kinds of single-wall carbon nanotube (SWCNT) suspensions were prepared: with catalytic iron, without iron, long SWCNTs (stable), short SWCNTs (stable), and short SWCNT (unstable). These suspensions were applied to A549, THP-1, and mouse peritoneal macrophage cells. After a 24-h exposure, the mitochondrial activity, cell membrane damage, intracellular oxidative stress, and expression of cytokine genes were determined. Among these properties of SWCNTs, stability of CNT suspension had the most influence on the cells, whereas the effects of iron content and fiber length were small. The unstable SWCNT suspension caused a substantial increase in intracellular ROS levels. Additionally, the cellular effects of stable multi-wall carbon nanotubes (MWCNTs) were examined. The MWCNT suspension did not show any cellular effects. Overall, influences of CNT suspension on mitochondrial activity and cell membrane damage were small. These results suggest that the physical properties of CNT suspension are important factors for their cellular effects. Thus, CNT suspensions prepared with the same material but having different physical properties would differ in the cellular effects they exert, including cytotoxicity. Therefore, physical characterization of CNT suspensions is essential to the evaluation of CNT toxicity. In particular, stability of CNT suspension notably influenced the intracellular ROS level.

Direct Filament Formation of Biological Carbon Nanotube Suspensions

In this study, aqueous carbon nanotube (CNT) suspensions were prepared using biological surfactant of sodium deoxycholate (NaDC). The influence of NaDC concentration on the NaDC self-association in water and the rheological responses of the NaDC-CNT-water system were investigated. It has been found that the yield stress of the suspension increased with NaDC concentration, which was strongly related to the NaDC self-association of lyotropic liquid crystals. Due to the enhanced rheological properties at high NaDC concentration (30%), it allowed the shear-induced filament formation in which the CNTs were aligned along to the shear direction. This filament formation may be attractive for transferring aligned CNTs on substrates in a controlled manner.