DJL

2D molybdenum disulfide (MoS₂) has distinct optical and electronic properties compared to aggregated MoS₂, enabling wide use of these materials for electronic and biomedical applications. However, the hazard potential of MoS₂ has not been studied extensively. Here, a comprehensive analysis of the pulmonary hazard potential of three aqueous suspended forms of MoS₂—aggregated MoS₂ (Agg-MoS₂), MoS₂ exfoliated by lithiation (Lit-MoS₂), and MoS₂ dispersed by Pluronic F87 (PF87-MoS₂)—is presented. No cytotoxicity is detected in THP-1 and BEAS-2B cell lines. However, Agg-MoS₂ induces strong proinflammatory and profibrogenic responses in vitro. In contrast, Lit- and PF87-MoS₂ have little or no effect. In an acute toxicity study in mice, Agg-MoS₂ induces acute lung inflammation, while Lit-MoS₂ and PF87-MoS₂ have little or no effect. In a subchronic study, there is no evidence of pulmonary fibrosis in response to all forms of MoS₂. These data suggest that exfoliation attenuates the toxicity of Agg-MoS₂, which is an important consideration toward the safety evaluation and use of nanoscale MoS₂ materials for industrial and biological applications.

The pulmonary hazard potential of three forms of MoS₂—aggregated (Agg-MoS₂), lithiation-exfoliated (Lit-MoS₂), and Pluronic F87 dispersed MoS₂ (PF87-MoS₂)—is studied. Although Agg-MoS₂ induces profibrogenic responses in vitro and acute lung inflammation in vivo, Lit- and PF87-MoS₂ have no such effect. These data suggest that exfoliation attenuates Agg-MoS₂’s toxicity, which is important toward its industrial and biological applications.

They’re coming! From Feynman to ribosome mimics, the evolution of artificial molecular machines is told in terms of key inventions and the questions the field continues to face, including design philosophies and what to make and why.

The concept of multifunctional transform­ation-dc devices is proposed and verified experimentally. The functions of dc metamaterials can be remotely altered by illuminating with visible light. If the light-induced dc illusion effect is activated, the electrostatic behavior of the original object is perceived as multiple equivalent objects with different pre-designed geo­metries. The experimental verification of the functional device makes it possible to control sophisticated transformation-dc devices with external light illumination.

Exfoliation of two-dimensional materials is key to obtaining high-performance properties. We present a simple kinetic model for exfoliation that is readily solved analytically. Random and irreversible sheet separation is postulated in the presence of highly effective stabilizers. This model appears to quantitatively fit graphene exfoliation data, and it illuminates mechanistic aspects of exfoliation. Thicker sheets exfoliate much faster than trilayer and bilayer sheets. Exfoliation follows highly activated diffusion-controlled intercalation of stabilizer into inter-sheet galleries. Application to the most concentrated graphene exfoliation data available supports these assumptions and provides insight for practical treatment regimens.

Splitting sheets: A simple kinetic model for exfoliation is presented that postulates random and irreversible sheet separation in the presence of highly effective stabilizers. This model appears to quantitatively fit graphene exfoliation data, and it illuminates mechanistic aspects of exfoliation: Thicker sheets exfoliate much faster than trilayer and bilayer sheets.

New layered anisotropic infrared semiconductors, black arsenic–phosphorus (b-AsP), with highly tunable chemical compositions and electronic and optical properties are introduced. Transport and infrared absorption studies demonstrate the semiconducting nature of b-AsP with tunable bandgaps, ranging from 0.3 to 0.15 eV. These bandgaps fall into the long-wavelength infrared regime and cannot be readily reached by other layered materials.

Chemical oxidation of under-charged Pb atoms reduces the density of trap states by a factor of 40 in films of colloidal PbS quantum dots for devices. These emissive sub-bandgap states are a byproduct of several standard ligand-exchange procedures. X-ray photoelectron spectro­scopy measurements and density function theory simulations demonstrate that they are associated with under-charged Pb.