Synthesis of 2-alkoxy 1,4-naphthoquinone derivatives as antiplatelet,antiinflammatory, and antiallergic agents

In our continuing search for novel antiplatelet, antiallergic, and antiinflammatory agents, 2-alkoxy derivatives of 1,4-naphthoquinone were prepared. Some of these compounds showed significant antiplatelet, antiallergic, and antiinflammatory activities. Among them, 2-propoxy-1,4-naphthoquinone and 2-butoxy-1,4-naphthoquinone exhibited potent inhibitory effect on neutrophil superoxide anion formation. These two compounds are worthy of further exploration.     

Numerical study of dispersing pollutant clouds in a built-up environment

In this paper, we study numerically the dispersion of a passive scalar released from an instantaneous point source in a built-up (urban) environment using a Reynolds-averaged Navier–Stokes method. A nonlinear k–? turbulence model [Speziale, C.G., 1987. On nonlinear k–l and k–? models of turbulence. J. Fluid Mech., 178, 459–475] was used for the closure of the mean momentum equations. A tensor diffusivity model [Yoshizawa, A., 1985. Statistical analysis of the anisotropy of scalar diffusion in turbulent shear flows. Phys. Fluids, 28, 3226–3231] was used for closure of the scalar transport equations. The concentration variance was also calculated from its transport equation, for which new values of Yoshizawa’s closure coefficients are used, in order to account for the instantaneous tracer release and the complex geometry. A new dissipation length-scale model, required for the modelling of the dissipation rate of concentration variance, is also proposed. The numerical results for the flow, the pollutant concentration and the concentration variance, are compared with experimental data. This data was obtained from a water-channel simulation of a full-scale field experiment of tracer dispersion through a large array of building-like obstacles known as the Mock Urban Setting Trial (MUST).     

New conjugated copolymers based on benzo[1,2‐b; 3,4‐b′]dithiophene and derivatives of benzo[g]quinoxaline for bulk heterojunction solar cells

A series of new low‐band gap copolymers based on dioctyloxybenzo[1,2‐b;3,4‐b′] dithiophene and bis(2‐thienyl)‐2,3‐diphenylbenzo[g]quinoxaline monomers have been synthesized via a Stille reaction. The effect of different functional groups attached to bis(2‐thienyl)‐2,3‐diphenylbenzo[g]quinoxaline was investigated and compared with their optical, electrochemical, hole mobility, and photovoltaic properties. Polymer solar cell (PSC) devices of the copolymers were fabricated with a configuration of ITO/ PEDOT: PSS/copolymers: PCBM (1:4 wt ratio)/Ca/Al. The best performance of the PSC device was obtained by using PbttpmobQ as the active layer. A power conversion efficiency of 1.42% with an open‐circuit voltage of 0.8 V, a short‐circuit current (JSC) of 5.73 mA cm⁻², and a fill factor of 30.9% was achieved under the illumination of AM 1.5, 100 mW cm⁻². © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Conformational Preferences and the Phase Stability of Fullerene Hexa‐adducts

Molecular conformation and the assembly structure determine the spatial arrangements of the constituent units and the functions of a molecule. Although, fullerene hexa‐adducts (FHAs) have been known as functional materials with great versatility, their conformational preferences and phase stability remain a complicate issue. By choosing bithiophene (T₂) and dodecyl bithiophene (C₁₂T₂) as the peripheral units of FHA, and using microscopic, scattering and diffraction characterizations, our study reveals how the intramolecular interaction and environmental stimulus affects the conformational preferences and phase stability of FHAs.     

Structure modification and annealing effect of polymer bulk heterojunction solar cells based on polyfluorene derivatives

Three low bandgap polyfluorene copolymers containing a donor–acceptor–donor moiety have been synthesized via Suzuki and Stille polymerization reactions. Their bandgaps and molecular energy levels (highest occupied molecular orbital and lowest unoccupied molecular orbital) varied with different polymerization methods. The molecular weight of the copolymer increased significantly through copolymerizing with a monomer having a long alkyl side chain. In order to investigate their photovoltaic properties, polymer solar cell devices based on the copolymers were fabricated with a structure of indium tin oxide/poly(styrene sulfonic acid)‐doped poly(ethylene dioxythiophene)/copolymers:[6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM)/LiF/Al under the illumination of AM 1.5G, 100 mW/cm². We found that the annealing temperature had a profound effect on the power conversion efficiency (PCE) of the devices with a blend of poly[9,9‐didodecylfluorene‐alt‐(bis‐thienylene) benzothiadiazole] (PF12‐TBT) and PCBM. The PCE of the solar cell based on PF12‐TBT/PCBM (1:4) annealing at 70 °C for 20 min was 4.13% with an open‐circuit voltage (V_oc) of 1.02 V, fill factor of 55.9%, and a short‐circuit current (J_sc) of 7.24 mA/cm². © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Optimum sol viscosity for stable electrospinning of silica nanofibres

Silica nanofibres have, due to their excellent properties, promising characteristics for multiple applications such as filtration, composites, catalysis, etc. Silica nanofibres can be obtained by combining electrospinning and the sol–gel process. To produce silica nanofibres most of the time organic solutions are applied containing a carrying polymer, which is afterwards removed by a thermal treatment to form pure ceramic nanofibres. Although electrospinning of the pure silica precursors without carrying polymer is preferred, the parameters influencing the stability of the electrospinning process are however largely unknown. In addition, this knowledge is essential for potential upscaling of the process. In this study, the optimum viscosity to electrospin in a stable manner is determined and the way to obtain this viscosity is evaluated. Sols with a viscosity between 120 and 200 mPa.s could be electrospun in a stable way, resulting in uniform and beadless nanofibres. Furthermore, this viscosity region corresponded with nanofibres having the lowest mean nanofibre diameters. Electrospinning with diluted sols was possible as well, but electrospinning of the fresh sols was more stable. These results illustrate the importance of the viscosity and degree of crosslinking of the sol for the stable electrospinning of silica nanofibres and demonstrate that upscaling of the electrospinning process of silica nanofibres is feasible.     

Direct‐current nanogenerator based on ZnO nanotube arrays

Due to the special structure of a nanotube (NT), the different potential from piezoelectricity can be naturally divided by the hollow of the tube when the NT is bent or deformed. Furthermore, both the bent/deformed inner and outer wall can form a steady voltage/current, which might enhance the output voltage/current. We demonstrate a direct‐current nanogenerator (NG) based on zinc oxide (ZnO) NT arrays driven by an ultrasonic wave. The average output voltage is ca. 0.10 mV and the current density is ca. 0.069 μA/mm². Our study shows that the maximum power output of the ZnO NT array NG is 0.112 nW and the power density is 1.4 nW/cm². The success of energy harvesting from ZnO NTs reveals the potential of using nanogenerators for tubular piezoelectric materials. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dendrimer-conjugated magnetic nanoparticles for removal of zinc (II) from aqueous solutions

Dendrimers are novel nanostructure materials that possess a unique three-dimensional molecular configuration. They have high adsorption capacities of heavy metals. Dendrimer-conjugated magnetic nanoparticles (Gn-MNPs) combining the superior adsorbent of dendrimers with magnetic nanoparticles (MNPs) have been developed for effective removal and recovery of Zn(II). In this study, the Gn-MNPs were synthesized, characterized, and examined as reusable adsorbents of Zn(II). Characterization conducted by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and elemental analysis revealed that dendrimers were successfully coated onto the surface of MNPs made of magnetite (Fe₃O₄). The pH effect studies indicate the Zn(II) adsorption with Gn-MNPs is a function of pH. The adsorption efficiency increases with increasing pH. At pH less than 3, Zn(II) is readily desorbed. Hence, the Gn-MNPs can be regenerated using the diluted HCl aqueous solution (0.1 M) where Zn(II) can be recovered in a concentrated form. It was found that the Gn-MNPs underwent 10 consecutive adsorption–desorption processes still retained the original removal capacity of Zn(II). The adsorption data were fitted well with both Langmuir and Freundlich isotherms. The maximum adsorption capacity determined by the Langmuir model is 24.3 mg/g at pH 7 and 25°C. A synergistic effect between the complexation reaction and the electrostatic interaction may account for the overall performance of Gn-MNPs.     

Ion-pair high-performance liquid chromatography of diaminopimelic acid in hydrolysates of physiological samples.

A method is reported for the determination of diaminopimelic acid (DAPA) in physiological samples. DAPA is derivatized with an o-phthaldialdehyde reagent solution, subjected to reversed-phase high-performance liquid chromatography and detected spectrofluorometrically. The method is a significant advance over previous methods because it uses the ion-pairing agent hexadecyltrimethylammonium bromide (HTMA) to facilitate DAPA measurement. Ion-pairing with HTMA avoids interference with co-eluting derivatives to provide simultaneous, sensitive, reproducible measurement of both DAPA peaks (DD,LL-DAPA and DL-DAPA).