Efficient selection methods for black phosphorene nanoribbons.

Black phosphorene (BP) has shown anisotropic, electronic, mechanical, and thermal properties for various promising applications in recent years. To take full advantage of this unique anisotropy in its further functional design and application, it is of paramount importance to separate BP with well-defined chirality quickly and precisely. In this paper, we propose three efficient methods to separate BP ribbons with different chiralities by utilizing their strong chirality-dependent bending stiffness. Our results show that the bending stiffness in the zigzag direction is 4 times larger than that in the armchair direction. The mechanical anisotropy and bending-binding competition are used to realize chirality-dependent design. To fold, wrap or scroll the BP nanoribbons, it is necessary to overcome the bending stiffness by applying the binding energy between the BP nanoribbons and the contact surfaces. Due to the mechanical anisotropy, the BP nanoribbons could easily be folded, wrapped and scrolled along the armchair direction rather than the zigzag direction. Therefore, we introduce this characteristic in our chirality separation designs as, the self-folding model to fold up the armchair BP nanoribbons by nanoparticles, the suspension-bridge sieve model to pull down the armchair BP nanoribbons, and the nanorod-roller model to scroll up the armchair nanoribbons. Our separation methods in this research can be extended to other 2D materials with anisotropic mechanical properties. We hope our findings would offer a novel route for the manufacturing of BP-based electronic devices and self-assembly of nano-devices.

Inhibition effect of glyphosate on the acute and subacute toxicity of cadmium to earthworm Eisenia fetida.

The acute and subacute toxicities of cadmium (Cd) to earthworm Eisenia fetida in the presence and absence of glyphosate were studied. Although Cd is highly toxic to E. fetida, the presence of glyphosate markedly reduced the acute toxicity of Cd to earthworm; both the mortality rate of the earthworms and the accumulation of Cd decreased with the increase of the glyphosate/Cd molar ratio. The subcellular distribution of Cd in E. fetida tissues showed that internal Cd was dominant in the intact cells fraction and the heat-stable proteins fraction. The presence of glyphosate reduced the concentration of Cd in all fractions, especially the intact cells. During a longer period of exposure, the weight loss of earthworm and the total Cd absorption was alleviated by glyphosate. Thus, the herbicide glyphosate can reduce the toxicity and bioavailability of Cd in the soil ecosystems at both short- and long-term exposures.

Subacute toxicity of copper and glyphosate and their interaction to earthworm (Eisenia fetida).

Glyphosate (GPS) and copper (Cu) are common pollutants in soils, and commonly co-exist. Due to the chemical structure of GPS, it can form complexes of heavy metals and interface their bioavailability in soil environment. In order to explore the interactions between GPS and Cu, subacute toxicity tests of Cu and GPS on soil invertebrate earthworms (Eisenia fetida) were conducted. The relative weight loss and whole-worm metal burdens increased significantly with the increasing exposure concentration of Cu, while the toxicity of GPS was insignificant. The joint toxicity data showed that the relative weight loss and the uptake of Cu, as well as the superoxide dismutase, catalase and malondialdehyde activities, were significantly alleviated in the present of GPS, which indicated that GPS could reduce the toxicity and bioavailability of Cu in the soil because of its strong chelating effects.

Does glyphosate impact on Cu uptake by, and toxicity to, the earthworm Eisenia fetida?

Glyphosate (GPS) is a wildly-used pesticide throughout the world. It affects metal behaviors in soil-water system as its functional groups such as amine, carboxylate and phosphonate can react with metal ions to form metal complexes. The reaction will result in the decreasing of heavy metal bioavailability. A laboratory experiment was conducted to investigate the interactions between GPS and copper (Cu) on the acute toxicity of soil invertebrate earthworm (Eisenia fetida), which was exposed to aqueous solutions for 48 h with different mixing concentrations of Cu and GPS (technical-grade Gly acid). The mortality rates, Cu uptake by earthworm, and some biomarkers such as superoxide dismutase (SOD) activity, glutathione (GSH) content, and acetylcholinesterase (AchE) activity were measured. The mortality rates and whole-worm metal burdens increased significantly with the increasing Cu concentration in solution. However, toxicity of GPS to earthworms was not observed in this study. Furthermore, the presence of GPS could significantly reduce the acute toxicity of Cu to earthworms. The mortality rates decreased sharply and the uptake of Cu was nearly halted in the presence of GPS. In addition, the SOD activity, GSH content, and AchE activity almost declined to the levels of the control. These results demonstrate that GPS could control the toxicity as well as the bioavailability of heavy metals in soil solutions where both GPS and heavy metals often coexist.