Colloidal Behavior and Biodegradation of Engineered Carbon-Based Nanomaterials in Aquatic Environment

Raman Spectroscopy Unfolds the Fate and Transformation of SWCNTs after Abrasive Wear of Epoxy Floor Coatings

Nanomaterials are integrated within consumer products to enhance specific properties of interest. Their release throughout the lifecycle of nano-enabled products raises concerns; specifically, mechanical strains can lead to the generation of fragmented materials containing nanomaterials. We investigated the potential release of single-walled carbon nanotubes (SWCNTs-brand TUBALL™) from epoxy composite materials. A pin-on-disk-type tribometer was used for the accelerated mechanical aging of the nanocomposites. A pristine nanocomposite material, abraded material and debris obtained from the abrasion in the tribometer were analyzed by Raman spectroscopy. The airborne-produced particles were captured using particle collectors. Stat Peel's Identifier C2 system was used to monitor the SWCNT content of respirable particles produced during the abrasion test. The SWCNT amounts found were below the LoQ. The Raman spectra conducted on the Stat Peel filters helped identify the presence of free SWCNTs released from the epoxy matrix, although they were notably scarce. Raman spectroscopy has been proved to be a crucial technique for the identification, characterization and assessment of structural changes and degradation in SWCNTs that occurred during the abrasion experiments.

Toxicity and Biotransformation of Carbon-Based Nanomaterials in Marine Microalgae Heterosigma akashiwo

This work is related to the environmental toxicology risk assessment and evaluation of the possible transformation of carbon-based nanomaterials (CNMs) after contact with marine microalgae. The materials used in the study represent common and widely applied multi-walled carbon nanotubes (CNTs), fullerene (C₆₀), graphene (Gr), and graphene oxide (GrO). The toxicity was evaluated as growth rate inhibition, esterase activity, membrane potential, and reactive oxygen species generation changes. The measurement was performed with flow cytometry after 3, 24, 96 h, and 7 days. The biotransformation of nanomaterials was evaluated after 7 days of microalgae cultivation with CNMs by FTIR and Raman spectroscopy. The calculated toxic level (EC₅₀ in mg/L, 96 h) of used CNMs reduced in the following order: CNTs (18.98) > GrO (76.77) > Gr (159.40) > C₆₀ (414.0). Oxidative stress and membrane depolarization were the main toxic action of CNTs and GrO. At the same time, Gr and C₆₀ decreased the toxic action with time and had no negative impact on microalgae after 7 days of exposure even at the concentration of 125 mg/L. Moreover, C₆₀ and Gr after 7 days of contact with microalgae cells obtained structural deformations.

The Comparative Toxic Impact Assessment of Carbon Nanotubes, Fullerene, Graphene, and Graphene Oxide on Marine Microalgae Porphyridium purpureum

The growing production and application of carbon-based nanomaterials (CNMs) represent possible risks for aquatic systems. However, the variety of CNMs with different physical and chemical properties and different morphology complicate the understanding of their potential toxicity. This paper aims to evaluate and compare the toxic impact of the four most common CNMs, namely multiwalled carbon nanotubes (CNTs), fullerene (C60), graphene (Gr), and graphene oxide (GrO) on the marine microalgae Porphyridium purpureum. The microalgae cells were exposed to the CNMs for 96 h and measured by flow cytometry. Based on the obtained results, we determined no observed effect level (NOEL), and calculated EC10 and EC50 concentrations for growth rate inhibition, esterase activity, membrane potential, and reactive oxygen species (ROS) generation changes for each tested CNM. According to the sensitivity (growth rate inhibition) of P. purpureum, the used CNMs can be listed in the following order (EC50 in mg/L, 96 h): CNTs (2.08) > GrO (23.37) > Gr (94.88) > C60 (>131.0). The toxicity of CNTs was significantly higher than the toxic effect of the other used CNMs, and only this sample caused an increase in ROS generation in microalgae cells. This effect was apparently caused by the high affinity between particles and microalgae associated with the presence of exopolysaccharide coverage on P. purpureum cells.