ZnO-Loaded Graphene for NO2 Gas Sensing.

This paper investigates the effect of decorating graphene with zinc oxide (ZnO) nanoparticles (NPs) for the detection of NO2. In this regard, two graphene sensors with different ZnO loadings of 5 wt.% and 20 wt.% were prepared, and their responses towards NO2 at room temperature and different conditions were compared. The experimental results demonstrate that the graphene loaded with 5 wt.% ZnO NPs (G95/5) shows better performance at detecting low concentrations of the target gas than the one loaded with 20 wt.% ZnO NPs (G80/20). Moreover, measurements under dry and humid conditions of the G95/5 sensor revealed that the material is very sensitive to ambient moisture, showing an almost eight-fold increase in NO2 sensitivity when the background changes from dry to 70% relative humidity. Regarding sensor selectivity, it presents a significant selectivity towards NO2 compared to other gas compounds.

Constant capacitance in nanopores of carbon monoliths.

The results obtained for binder-free electrodes made of carbon monoliths with narrow micropore size distributions confirm that the specific capacitance in the electrolyte (C2H5)4NBF4/acetonitrile does not depend significantly on the micropore size and support the foregoing constant result of 0.094 ± 0.011 F m(-2).

Toxicological assessment of pristine and degraded forms of graphene functionalized with MnOx nanoparticles using human in vitro models representing different exposure routes.

The development of novel advanced nanomaterials (NMs) with outstanding characteristics for their use in distinct applications needs to be accompanied by the generation of knowledge on their potential toxicological impact, in particular, that derived from different occupational risk exposure routes, such as inhalation, ingestion, and skin contact. The harmful effects of novel graphene-metal oxide composites on human health are not well understood, many toxicological properties have not been investigated yet. The present study has evaluated several toxicological effects associated with graphene decorated with manganese oxide nanoparticles (GNA15), in a comparative assessment with those induced by simple graphene (G2), on human models representing inhalation (A549 cell line), ingestion (HT29 cell line) and dermal routes (3D reconstructed skin). Pristine and degraded forms of these NMs were included in the study, showing to have different physicochemical and toxicological properties. The degraded version of GNA15 (GNA15d) and G2 (G2d) exhibited clear structural differences with their pristine counterparts, as well as a higher release of metal ions. The viability of respiratory and gastrointestinal models was reduced in a dose-dependent manner in the presence of both GNA15 and G2 pristine and degraded forms. Besides this, all NMs induced the production of reactive oxygen species (ROS) in both models. However, the degraded forms showed to induce a higher cytotoxicity effect. In addition, we found that none of the materials produced irritant effects on 3D reconstructed skin when present in aqueous suspensions. These results provide novel insights into the potentially harmful effects of novel multicomponent NMs in a comprehensive manner. Furthermore, the integrity of the NMs can play a role in their toxicity, which can vary depending on their composition and the exposure route.

Toxicology assessment of manganese oxide nanomaterials with enhanced electrochemical properties using human in vitro models representing different exposure routes.

In the present study, a comparative human toxicity assessment between newly developed Mn3O4 nanoparticles with enhanced electrochemical properties (GNA35) and their precursor material (Mn3O4) was performed, employing different in vitro cellular models representing main exposure routes (inhalation, intestinal and dermal contact), namely the human alveolar carcinoma epithelial cell line (A549), the human colorectal adenocarcinoma cell line (HT29), and the reconstructed 3D human epidermal model EpiDerm. The obtained results showed that Mn3O4 and GNA35 harbour similar morphological characteristics, whereas differences were observed in relation to their surface area and electrochemical properties. In regard to their toxicological properties, both nanomaterials induced ROS in the A549 and HT29 cell lines, while cell viability reduction was only observed in the A549 cells. Concerning their skin irritation potential, the studied nanomaterials did not cause a reduction of the skin tissue viability in the test conditions nor interleukin 1 alpha (IL- 1 α) release. Therefore, they can be considered as not irritant nanomaterials according to EU and Globally Harmonized System of Classification and Labelling Chemicals. Our findings provide new insights about the potential harmful effects of Mn3O4 nanomaterials with different properties, demonstrating that the hazard assessment using different human in vitro models is a critical aspect to increase the knowledge on their potential impact upon different exposure routes.