Uptake and toxicity of cerium dioxide nanoparticles with different aspect ratio.

Cerium dioxide nanoparticles (CeONPs) have been extensively applied in research for future energy development due to two common oxidation states on their surface. Considering that shape (aspect ratio) is a key determinant of NPs-induced toxicity, we compared the toxicity of hexagonal (H)- and rod-shaped (R)-CeONPs in mice. At 24 h after pharyngeal aspiration, both types of CeONPs recruited surrounding immune cells (monocytes and neutrophils) into the lung, and R-CeONPs induced a more severe pulmonary inflammatory response compared with H-CeONPs. To identify an indicator to predict pulmonary inflammatory responses at the cellular level, we also investigated their responses in alveolar macrophage cells. At 24 h after treatment, both types of CeONPs were mainly located within the vacuoles (partially, in the lysosome) in the cytoplasm. Mitochondrial damage, intracellular calcium accumulation, and increased NO production were observed in cells exposed to both types of CeONPs, ultimately resulting in a decrease in cell viability. More interestingly, both types of CeONPs formed multinucleated giant cells. Meanwhile, contrary to when suspended in deionized water, R-CeONPs were strongly aggregated with a negative charge in cell culture media, whereas H-CeONPs were relatively well-dispersed with a positive charge. R-CeONPs-induced lysosomal extension was also recovered by premix with negatively charged DNA, and even NPs suspended in cell culture media without cells were detected under the FACS system, suggesting interference by protein corona. Therefore, we suggest that shape (aspect ratio) is an important factor determining inhaled NPs-induced pathology and that the effect of the surface charge and protein corona should be carefully considered in interpreting results derived from in vitro tests. Furthermore, we propose that the relationship between the formation of multinucleated giant cells and the inflammatory response of inhaled CeONPs should be further studied.

Comparison of toxicity and cellular responses following pulmonary exposure to different types of nanofibers.

Pulmonary effects of inhaled microfibers are an emerging public health concern. In this study, we investigated toxicity following pulmonary exposure to synthetic polyethylene oxide fibroin (PEONF) and silk fibroin (SFNF) nanofibers and the cellular responses. When instilled intratracheally weekly for four weeks, body weight gain was significantly reduced in female mice exposed to the higher dose of SFNF when compared with the control group. The total number of cells in the lungs was more significant in all treated groups than in the control, whereas the relative portion of neutrophils and eosinophils increased significantly only in female mice exposed to SFNF. Both types of nanofibers induced notable pathological changes and increased pulmonary expression of MCP-1α, CXCL1, and TGF-ß. More importantly, blood calcium, creatinine kinase, sodium, and chloride concentration were affected significantly, showing sex- and material-dependent differences. The relative portion of eosinophils increased only in SFNF-treated mice. In addition, both types of nanofibers induced necrotic and late apoptotic cell death in alveolar macrophages after 24 h of exposure, with accompanying oxidative stress, increased NO production, cell membrane rupture, intracellular organelle damage, and intracellular calcium accumulation. Additionally, multinucleated giant cells were formed in cells exposed to PEONF or SFNF. Taken together, the findings indicate that inhaled PEONF and SFNF may cause systemic adverse health effects with lung tissue damage, showing differences by sex- and material. Furthermore, PEONF- and SFNF-induced inflammatory response may be partly due to the low clearance of dead (or damaged) pulmonary cells and the excellent durability of PEONF and SFNF.

Organogermanium Nanowire Cathodes for Efficient Lithium-Oxygen Batteries.

We report a technique for effectively neutralizing the generation of harmful superoxide species, the source of parasitic reactions, in lithium-oxygen batteries to generate stable substances. In organic electrolytes, organogermanium (Propa-germanium, Ge-132) nanowires can suppress solvated superoxide and induce strong surface-adsorption reaction due to their high anti-superoxide disproportionation activity. Resultantly, the effect of organogermanium nanowires mitigate toxic oxidative stress to stabilize organic electrolytes and promote good Li2O2 growth. These factors led to long duration of the electrolytes and impressive rechargeability of lithium-oxygen batteries.

Ultrafine α-Phase Molybdenum Carbide Decorated with Platinum Nanoparticles for Efficient Hydrogen Production in Acidic and Alkaline Media.

The development of efficient electrocatalysts is important to produce clean and sustainable hydrogen fuel on a large scale. With respect to cathodic reactions, Pt exhibits an overwhelming electrocatalytic capability in the hydrogen evolution reaction (HER) in comparison with other earth-abundant electrocatalysts, despite its rarity and high cost. So, a hybrid catalyst that combines a low-cost electrocatalyst with Pt would balance cost-effectiveness with catalytic activity. Herein, α-phase molybdenum carbide (MoC1- x ) nanoparticles (NPs) decorated with a small amount of Pt (MoC1- x /Pt-NPs) are designed to achieve high-performance hydrogen production in acidic and alkaline media. MoC1- x -NPs exhibit good electrocatalytic HER activity as well as stability and durability. They show favorable catalytic kinetics in an alkaline medium, suggesting an active water dissociation process. After Pt decoration, Pt-NPs that are 2-3 nm in diameter are well incorporated with MoC1- x -NPs. MoC1- x /Pt-NPs with a small amount of Pt (2.7-3 wt%) and are able to perform superior electrocatalytic HER activity, and possess stability and durability that is comparable to that of commercial Pt/C. Notably, they exhibit a higher intrinsic catalytic activity compared to that of Pt/C in an alkaline medium, indicating that they promote the sluggish catalytic kinetics of Pt in alkaline medium.

Single and polycrystalline CeO2 nanorods as oxygen-electrode materials for lithium-oxygen batteries.

Single and polycrystalline CeO2 nanorods (NRs) were prepared for application as oxygen-electrode electrocatalysts for lithium-oxygen batteries. The CeO2 NRs were prepared via a time-controlled hydrothermal process. At a high current rate of 1000 mA g-1, the single crystalline CeO2 NRs exhibited a higher reversibility and a lower voltage gap than polycrystalline CeO2 NRs. We compared the oxygen reduction and evolution kinetics of single and polycrystalline CeO2 NRs using electrochemical impedance spectroscopy.