Ultrathin 2D TiS2 Nanosheets for High Capacity and Long‐Life Sodium Ion Batteries

Sodium ion batteries are now attracting great attention, mainly because of the abundance of sodium resources and their cheap raw materials. 2D materials possess a unique structure for sodium storage. Among them, transition metal chalcogenides exhibit significant potential for rechargeable battery devices due to their tunable composition, remarkable structural stability, fast ion transport, and robust kinetics. Herein, ultrathin TiS₂ nanosheets are synthesized by a shear‐mixing method and exhibit outstanding cycling performance (386 mAh g^?1 after 200 cycles at 0.2 A g^?1). To clarify the variations of galvanostatic curves and superior cycling performance, the mechanism and morphology changes are systematically investigated. This facile synthesis method is expected to shed light on the preparation of ultrathin 2D materials, whose unique morphologies could easily enable their application in rechargeable batteries.     

Cancer’s camouflage: Microvesicle shedding from cholesterol-rich tumor plasma membranes might blindfold first-responder immunosurveillance strategies

Intermediary metabolism of tumors is characterized, in part, by a dysregulation of the cholesterol biosynthesis pathway at its rate-controlling enzyme providing the molecular basis for tumor membranes (mitochondria, plasma membrane) to become enriched with cholesterol (Bloch, 1965; Feo et al., 1975; Brown and Goldstein, 1980; Goldstein and Brown, 1990). Cholesterol enriched tumor mitochondria manifest preferential citrate export, thereby providing a continuous supply of substrate precursor for the tumor’s dysregulated cholesterogenesis via a “truncated” Krebs/TCA cycle (Kaplan et al., 1986; Coleman et al., 1997). Proliferating tumors shed elevated amounts of plasma membrane-derived extracellular vesicles (pmEV) compared with normal tissues (van Blitterswijk et al., 1979; Black, 1980). Coordination of these metabolic phenomena in tumors supports the enhanced intercalation of cholesterol within the plasma membrane lipid bilayer’s cytoplasmic face, the promotion of outward protrusions from the plasma membrane, and the evolution of cholesterol enriched pmEV. The pmEV shed by tumors possess elevated cholesterol and concentrated cell surface antigen clusters found on the tumor cells themselves (Kim et al., 2002). Upon exfoliation, saturation of the extracellular milieu with tumor-derived pmEV could allow early onset mammalian immune surveillance mechanisms to become “blind” to an evolving cancer and lose their ability to detect and initiate strategies to destroy the cancer. However, a molecular mechanism is lacking that would help explain how cholesterol enrichment of the pmEV inner lipid bilayer might allow the tumor cell to evade the host immune system. We offer a hypothesis, endorsed by published mathematical modeling of biomembrane structure as well as by decades of in vivo data with diverse cancers, that a cholesterol enriched inner bilayer leaflet, coupled with a logarithmic expansion in surface area of shed tumor pmEV load relative to its derivative cancer cell, conspire to force exposure of otherwise unfamiliar membrane integral protein domains as antigenic epitopes to the host’s circulating immune surveillance system, allowing the tumor cells to evade destruction. We provide elementary numerical estimations comparing the amount of pmEV shed from tumor versus normal cells.     

Scalable Water‐Based Production of Highly Conductive 2D Nanosheets with Ultrahigh Volumetric Capacitance and Rate Capability

Highly conductive and ultrathin 2D nanosheets are of importance for the development of portable electronics and electric vehicles. However, scalable production and rational design for highly electronic and ionic conductive 2D nanosheets still remain a challenge. Herein, an industrially adoptable fluid dynamic exfoliation process is reported to produce large quantities of ionic liquid (IL)‐functionalized metallic phase MoS₂ (m‐MoS₂) and defect‐free graphene (Gr) sheets. Hybrid 2D–2D layered films are also fabricated by incorporating Gr sheets into compact m‐MoS₂ films. The incorporated IL functionalities and Gr sheets prevent aggregation and restacking of the m‐MoS₂ sheets, thereby creating efficient and rapid ion and electron pathways in the hybrid films. The hybrid film with a high packing density of 2.02 g cm^?3 has an outstanding volumetric capacitance of 1430.5 F cm^?3 at 1 A g^?1 and an extremely high rate capability of 80% retention at 1000 A g^?1. The flexible supercapacitor assembled using a polymer‐gel electrolyte exhibits excellent resilience to harsh electrochemical and mechanical conditions while maintaining an impressive rate performance and long cycle life. Successful achievement of an ultrahigh volumetric energy density (1.14 W h cm^?3) using an organic electrolyte with a wide cell voltage of ≈3.5 V is demonstrated.     

Engineered MoSe2‐Based Heterostructures for Efficient Electrochemical Hydrogen Evolution Reaction

2D transition metal‐dichalcogenides are emerging as efficient and cost‐effective electrocatalysts for the hydrogen evolution reaction (HER). However, only the edge sites of their trigonal prismatic phase show HER‐electrocatalytic properties, while the basal plane, which is absent of defective/unsaturated sites, is inactive. Herein, the authors tackle the key challenge of increasing the number of electrocatalytic sites by designing and engineering heterostructures composed of single‐/few‐layer MoSe₂ flakes and carbon nanomaterials (graphene or single‐wall carbon nanotubes) produced by solution processing. The electrochemical coupling between the materials that comprise the heterostructure effectively enhances the HER‐electrocatalytic activity of the native MoSe₂ flakes. The optimization of the mass loading of MoSe₂ flakes and their electrode assembly via monolithic heterostructure stacking provides a cathodic current density of 10 mA cm^?2 at overpotential of 100 mV, a Tafel slope of 63 mV dec^?1, and an exchange current density (j₀) of 0.203 µA cm^?2. In addition, thermal and chemical treatments are exploited to texturize the basal planes of the MoSe₂ flakes (through Se‐vacancies creation) and to achieve in situ semiconducting‐to‐metallic phase conversion, respectively, thus they activate new HER‐electrocatalytic sites. The as‐engineered electrodes show a 4.8‐fold enhancement of j₀ and a decrease in the Tafel slope to 54 mV dec^?1.     

Liquid Exfoliated Co(OH)2 Nanosheets as Low‐Cost,Yet High‐Performance,Catalysts for the Oxygen Evolution Reaction

Identifying cheap, yet effective, oxygen evolution catalysts is critical to the advancement of water splitting. Using liquid exfoliated Co(OH)₂ nanosheets as a model system, a simple procedure is developed to maximize the activity of any oxygen evolution reaction nanocatalyst. First the nanosheet edges are confirmed as the active areas by analyzing the catalytic activity as a function of nanosheet size. This allows the authors to select the smallest nanosheets (length ≈50 nm) as the best performing catalysts. While the number of active sites per unit electrode area can be increased via the electrode thickness, this is found to be impossible beyond ≈10 µm due to mechanical instabilities. However, adding carbon nanotubes increases both toughness and conductivity significantly. These enhancements mean that composite electrodes consisting of small Co(OH)₂ nanosheets and 10 wt% nanotubes can be made into freestanding films with thickness of up to 120 µm with no apparent electrical limitations. The presence of diffusion limitations results in an optimum electrode thickness of 70 µm, yielding a current density of 50 mA cm^?2 at an overpotential of 235 mV, close to the state of the art in the field. Applying this procedure to a high‐performance catalyst such as NiFeO_x should significantly surpass the state of the art.     

Effect of acidosis on bilirubin-induced toxicity to human erythrocytes

Unconjugated bilirubin binds to erythrocytes, eliciting crenation, lipid elution and hemolysis. The present work attempts to establish the role of acidosis on bilirubin-induced toxicity to human erythrocytes. To this end, pH values ranging from 7.0–8.0 were used to induce a different representation of acid and anionic bilirubin species, respectively. Erythrocytes from healthy donors were incubated with bilirubin and albumin (3:1, molar ratio), during 4 h. Erythrocyte-bound bilirubin was evaluated by albumin or chloroform extraction in an attempt to assess either mono- and dianion bilirubin adsorbed on the cell surface or colloidal aggregates, respectively. Cytotoxicity indicators, such as the morphological index, and the extent of phospholipids and hemoglobin release were also determined. The results showed that as pH drops from 8.0–7.0, less bilirubin is removed by albumin and more become recovered by chloroform. The data corroborate the predominance of anionic and non-aggregated bilirubin species at pH 8.0 with dimers and precipitates occurring at 7.0. In accordance, crenation and cell lysis were four times increased at acidic pH. In contrast, elution of phospholipids was 1.5 times less evident at the same pH, thus suggesting that formation of bilirubin complexes with membrane phospholipids may have contributed to prevent their release. In conclusion, both anionic and acid bilirubin species interact with human erythrocytes leading to cytotoxic alterations that may determine definitive lesions. Nevertheless, increased vulnerability to crenation and hemolysis are more likely to occur in acidic conditions pointing to the bilirubin precipitates as the main candidates of bilirubin-induced toxicity to erythrocytes.