Tubular microporous organic networks bearing imidazolium salts and their catalytic CO2 conversion to cyclic carbonates

Tubular microporous organic networks bearing imidazolium salts (T-IM) were prepared by Sonogashira coupling of tetrakis(4-ethynylphenyl)methane and diiodoimidazolium salts, which showed promising catalytic activities in heterogeneous conversion of CO(2) into cyclic carbonates.     

Facile synthesis route to highly crystalline mesoporous γ-MnO2 nanospheres

Hierarchical mesoporous γ-MnO₂ nanospheres with high crystallinity were prepared by a template-free self-assembly under applied ultrasonic waves, resulting in a solid spherical nanostructure with stacking of nanosized worm-like particles. This approach based on ultrasound exposure reduces the particle size and enhances the crystallinity of γ-MnO₂, leading to a large effective area for the active domains and a stable structural arrangement of the active materials. The applicability of γ-MnO₂ to high-power lithium batteries is demonstrated, based on improved capacity, excellent rate capability, and stable cyclability, which stem from the outstanding physical properties of the hierarchical mesoporous nanostructure.     

Synthesis and Preliminary In Vitro Biological Evaluation of 5-Chloro-2-(Substituted Phenyl)Benzo[d]Thiazole Derivatives Designed As Novel Antimelanogenesis Agents

We describe the design, synthesis, and biological activities of 5-chloro-2-(substituted phenyl)benzo[d]thiazole derivatives as novel tyrosinase inhibitors. Among them, 4-(5-chloro-2,3-dihydrobenzo[d]thiazol-2-yl)-2,6-dimethoxyphenol (MHY884) and 2-bromo-4-(5-chloro-benzo[d]thiazol-2-yl)phenol (MHY966) showed inhibitory activity higher than or similar to kojic acid, against mushroom tyrosinase. Therefore, we carried out kinetic studies on the two compounds with potent tyrosinase inhibitory effects. Kinetic analysis of tyrosinase inhibition revealed that all of these compounds are competitive inhibitors. MHY884 and MHY966 effectively inhibited tyrosinase activity and reduced melanin levels in B16 cells treated with ??-melanocyte stimulating hormone (??-MSH). These data strongly suggest that the newly synthesized compounds MHY884 and MHY966 could suppress production of melanin via inhibition of tyrosinase activity.     

Fabrication of a high lithium ion conducting lithium borosilicate glass

A lithium ion conducting glass, Li₂O-B₂O₃-SiO₂, is fabricated by the conventional melt and quenching technique from a mixture of Li₂CO₃, B₂O₃ and SiO₂ powders. It appears that B₂O₃ decreases the crystallization tendency of the Li₂O-SiO₂ binary glass, resulting in an expanded glass forming region in the Li₂O-B₂O₃-SiO₂ ternary glass. The maximum conductivity is 2 × 10^− 6 S cm^− 1 at 25 °C for the 50Li₂O-38B₂O₃-12SiO₂ glass sample. The observed high conductivity is due to the mixed former effect. The conductivity strongly depends on the Li₂O content, but not on K (SiO₂/B₂O₃) in the Li₂O-B₂O₃-SiO₂ ternary glass.     

Ultrafast intramolecular exciton splitting dynamics in isolated low-band-gap polymers and their implications in photovoltaic materials design

Record-setting organic photovoltaic cells with PTB polymers have recently achieved ~8% power conversion efficiencies (PCE). A subset of these polymers, the PTBF series, has a common conjugated backbone with alternating thieno[3,4-b]thiophene and benzodithiophene moieties but differs by the number and position of pendant fluorine atoms attached to the backbone. These electron-withdrawing pendant fluorine atoms fine tune the energetics of the polymers and result in device PCE variations of 2-8%. Using near-IR, ultrafast optical transient absorption (TA) spectroscopy combined with steady-state electrochemical methods we were able to obtain TA signatures not only for the exciton and charge-separated states but also for an intramolecular ("pseudo") charge-transfer state in isolated PTBF polymers in solution, in the absence of the acceptor phenyl-C(61)-butyric acid methyl ester (PCBM) molecules. This led to the discovery of branched pathways for intramolecular, ultrafast exciton splitting to populate (a) the charge-separated states or (b) the intramolecular charge-transfer states on the subpicosecond time scale. Depending on the number and position of the fluorine pendant atoms, the charge-separation/transfer kinetics and their branching ratios vary according to the trend for the electron density distribution in favor of the local charge-separation direction. More importantly, a linear correlation is found between the branching ratio of intramolecular charge transfer and the charge separation of hole-electron pairs in isolated polymers versus the device fill factor and PCE. The origin of this correlation and its implications in materials design and device performance are discussed.     

Migration of nitrogen in hexagonal Ge2Sb2Te5: An ab‐initio study

The migration barrier energies of the nitrogen atom and N₂ molecule, and the activation barriers for the dissociation and formation of N₂ in Ge₂Sb₂Te₅ were calculated by ab‐initio methods. Various transition and metastable states were found along the migration pathway. Migration barrier energies up to 1.19 eV for the nitrogen atom suggest that it is difficult for it to move from one site to any other site or diffuse out from Ge₂Sb₂Te₅ although doped nitrogen is energetically less stable with respect to N₂ in vacuum. N₂ in Ge₂Sb₂Te₅ was hardly expected to dissociate into nitrogen atoms and vice versa. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of nanoporous silica aerogel by ambient pressure drying

A crack-free silica aerogel monolith was fabricated from a cheap water glass derived silicic acid solution by adding glycerol, which served as a drying control chemical additive (DCCA). The OH surfaces of the wet gel with glycerol were modified using a TMCS/n-hexane mixture followed by solvent exchange from water to n-hexane. The obtained surface modified wet gel was dried at 75 °C under ambient pressure. The addition of glycerol appears to give the wet gel a more homogeneous microstructure (larger pore size and uniform size distribution) as well as enhanced stiffness. However, glycerol also retards surface modification and solvent exchange. The aerogel synthesized with glycerol added to the silica sol maintained a relatively low bulk density compared with the aerogels aged in a mixed ethanol (EtOH)/TEOS solution. The reproducibility of aerogel production was further improved in the aerogel synthesized with glycerol added to the silica sol and aged in a 70%EtOH/30%TEOS solution.