Stability and dispersibility of microplastics in experimental exposure medium and their dimensional characterization by SMLS, SAXS, Raman microscopy, and SEM.

The plastic production that contributes to the global plastic reservoir presents a major challenge for society in managing plastic waste and mitigating the environmental damage of microplastic (MP) pollution. In the environment, the formation of biomolecular corona around MPs enhance the stability of MP suspensions, influencing the bioavailability and toxicity of MPs. Essential physical properties including MP stability, dispersibility, agglomeration, and dimensional size must be precisely defined and measured in complex media taking into account the formation of a protein corona. Using static multiple light scattering (SMLS), small angle X-ray scattering (SAXS), Raman microscopy, and scanning electron microscopy (SEM), we measured the particle size, density, stability, and agglomeration state of polyethylene and polypropylene MPs stabilized in aqueous suspension by BSA. SEM analysis revealed the formation of nanoplastic debris as MP suspensions aged. Our results suggest that protein adsorption favors the formation of secondary nanoplastics, potentially posing an additional threat to ecosystems. This approach provides analytical methodologies by integrating SEM, SMLS, and SAXS, for characterizing MP suspensions and highlights the effect of the protein corona on size measurements of micro/nanoplastics. Our analysis demonstrates the detectability of secondary nanoplastics by SEM, paving the way for monitoring and controlling human exposure.

Graphene oxide incorporating carbon fibre-reinforced composites submitted to simultaneous impact and fire: Physicochemical characterisation and toxicology of the by-products.

The toxicological profile of particulates released from carbon fibre-reinforced composites (CFC) incorporating nanoadditives, under impact and fire conditions (e.g. aircraft crash), is unknown to date. Our aim was to investigate the effects of simultaneous impact and fire on the physicochemical features of the particles released from CFCs produced from a graphene oxide (GO)-reinforced epoxy resin and the consequences on its toxicological profile. CFC samples with (CFC + GO) or without GO (CFC) were subjected to simultaneous impact and fire through a specific setup. Soot and residues were characterised and their toxicity was compared to that of virgin GO. Virgin GO was not cytotoxic but induced pro-inflammatory and oxidative stress responses. The toxicity profile of CFC was similar for soot and residue: globally not cytotoxic, inducing a pro-inflammatory response and no oxidative stress. However, an increased cytotoxicity at the highest concentration was potentially caused by fibres of reduced diameters or fibril bundles, which were observed only in this condition. While the presence of GO in CFC did not alter the cytotoxicity profile, it seemed to drive the pro-inflammatory and oxidative stress response in soot. On the contrary, in CFC + GO residue the biological activity was decreased due to the physicochemical alterations of the materials.

Dimensional measurement of TiO2 (Nano) particles by SAXS and SEM in powder form.

The market for nano-additive materials has been growing exponentially since 2012, with almost 5040 consumer products containing nanoparticles in 2021. In parallel, the increasing recommendations, definitions and legislations underline the need for traceability of manufactured nanoparticles and for methods able to identify and quantify the "nano" dimensional character in manufactured product. From a multi-technic approach, this paper aims to compare the mesurands extracted from SAXS/BET (specific surface area) and SEM (diameter equivalent to a projected surface area) on different TiO2 powder issued from referenced, synthesized materials, raw materials (additives) and extracted materials from manufactured products. The influence of various parameters such as the anisotropic factor, the interaction between particles, the size distribution and the extraction steps are discussed to illustrate their impact on the diameter values issued from two different measurands. These results illustrate the difficulties in (nano)particles characterization. SEM and SAXS are complementary techniques depending on the level of dimensional characterization required.

A DFT study on the initial stage of thermal degradation of Poly(methyl methacrylate)/carbon nanotube system.

DFT calculations, with VWN exchange correlation functional and double numeric basis set, were used to evaluate the energies required for the scission reactions taking place in the initial stage of the thermal degradation of Poly(methyl methacrylate) (PMMA) in the presence of a carbon nanotube (CNT). Side group and main chain scissions were investigated. The results averaged from five configurations of pure PMMA (DP=5) were used as references and compared to the results obtained for the five same configurations of PMMA grafted on three carbon nanotubes of similar diameter (1.49 nm). The bond dissociation energies (BDE) of main chain scission evaluated for grafted PMMA was 4 % less endothermic than for pure PMMA. These results seemed independent of the tested chirality (11,11); (12,10) and (16,5) of the carbon nanotubes. Comparisons with the BDE of the weakest bonds due to intrinsic defaults (head to head and unsaturated end chain) were performed.