Monodisperse conducting colloidal dipoles with symmetric dimer structure for enhancing electrorheology properties

This study introduces an electrorheological (ER) approach that allows us to obtain remarkably enhanced ER properties by using monodisperse colloidal dimer particles. Two sets of colloidal particles, which are spheres and symmetric dimers, were synthesized employing the seeded polymerization technique. The aspect ratio of dimer particles was ~1.43. Then, the surface of the particles was coated with polyaniline by using the chemically oxidative polymerization method. After preparation of the particle suspensions having the same particle volume and concentration, their ER behavior was investigated with changing the electric field strength. At the same experimental condition, both shear stress and shear yield stress of the dimer particle suspension remarkably increased, compared with those of the spherical particle suspension. This attributes to the fact that the shape anisotropy of suspending particles effectively led to increase in the dipole moment under the electric field, thus resulting in formation of a well-structured colloidal chains between the electrodes.     

Sesquiterpenes and other constituents from Dendranthema zawadskii var. latilobum

Six new germacranolides, zawadskinolides A-F (1-6), and a new eudesmane glucoside, chrysantiloboside (7) were isolated from the aerial parts of Dendranthema zawadskii var. latilobum, along with thirteen known constituents. Their structures were elucidated by means of spectroscopic evidence. Bioassay showed that flavonoids such as apigenin (9), (-)-eriodictyol (10) and nepetin (12), as well as the sesquiterpene lactone, zawadskinolide F (6), inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells with IC50 values of 66.15, 132.55, 35.44, and 91.32?μM, respectively.     

Estimation of second-order derivative thermodynamic properties using the crossover cubic equation of state

In this research, we apply the crossover cubic equation of state (XCubic EOS) [1] to the calculations of thermodynamic second-order derivative properties (isochoric heat capacity, isobaric heat capacity, isothermal compressibility, thermal expansion coefficient, the Joule–Thomson coefficient, and speed of sound). This equation of state is used to calculate those properties of pure systems (carbon dioxide, normal alkanes from methane to propane). We show that, over a wide range of states, the equation of state yields each property with a much better accuracy than the original PT equation of state and near the critical region, represents the singular behaviour well.     

Determination of spinetoram in leafy vegetable crops using liquid chromatography and confirmation via tandem mass spectrometry

Spinetoram is a second-generation member of the spinosyn class, all members of which have been shown to be effective in insect control via a novel mode of action. Spinetoram is a mixture of 3'-O-ethyl-5, 6-dihydro spinosyn J (XDE-175-J) and 3'-O-ethyl spinosyn L (XDE-175-L). In order to establish a determination method for the analysis of spinetoram residues in crops, commercial product (5% suspension concentrate spinetoram) was applied to two leafy vegetables (Garland chrysanthemum and Aster scaber) on different spraying schedules. The analytical method used herein was based on a reversed-phase separation on a C(18) column, isocratic elution and UV detection. The analytes were confirmed via tandem mass spectrometry. The method was linear over a concentration range of 0.05-10 ppm with a correlation coefficient in excess of 0.9998. The recoveries of XDE-175-J and XDE-175-L from the two vegetables ranged between 86.04 and 98.87% at spiking levels of 1 and 5 ppm. The relative standard deviations were no more than 7% for all recovery tests conducted herein. The calculated limits of detection and quantification were 0.01 and 0.03 ppm for both XDE-175-J and XDE-175-L. The levels of residues in two vegetables treated under a fixed schedule in the greenhouse were 6.21-0.55 ppm (maximum residue limit (MRL) = 7 ppm). In sum, this method constitutes an easy and reliable technique for the determination of spinetoram in leafy vegetables.     

Unambiguous identification of Möbius aromaticity for meso-aryl-substituted [28]hexaphyrins(1.1.1.1.1.1)

meso-Aryl-substituted [28]hexaphyrins(1.1.1.1.1.1) have been examined by (1)H, (13)C, and (19)F NMR spectroscopies, UV-vis absorption spectroscopy, magnetic circular dichroism spectroscopy, and single-crystal X-ray diffraction analysis. All of these data consistently indicate that [28]hexaphyrins(1.1.1.1.1.1) in solution at 25 degrees C exist largely as an equilibrium among several rapidly interconverting twisted M?bius conformations with distinct aromaticities, with a small contribution from a planar rectangular conformation with antiaromatic character at slightly higher energy. In the solid state, [28]hexaphyrins(1.1.1.1.1.1) take either planar or M?bius-twisted conformations, depending upon the meso-aryl substituents and crystallization conditions, indicating a small energy difference between the two conformers. Importantly, when the temperature is decreased to -100 degrees C in THF, these rapid interconversions among M?bius conformations are frozen, allowing the detection of a single [28]hexaphyrin(1.1.1.1.1.1) species having a M?bius conformation. Detailed analyses of the solid-state M?bius structures of compounds 2b, 2c, and 2f showed that singly twisted structures are achieved without serious strain and that cyclic pi-conjugation is well-preserved, as needed for exhibiting strong diatropic ring currents. Actually, the harmonic-oscillator model for aromaticity (HOMA) values of these structures are significantly large (0.85, 0.69, and 0.71, respectively), confirming the first demonstration of stable M?bius aromatic systems consisting of free-base expanded porphyrins without the assistance of metal coordination.     

Star-shaped electrochemiluminescent metallodendrimers with central polypyridyl Ru(II) complexes: Synthesis and their photophysical and electrochemical properties

Several dendritic bridging ligands were designed and synthesized to develop more sensitive and efficient electrochemiluminescent (ECL) polynuclear Ru(II) complexes. Various types of novel two-armed, four-armed and six-armed tris(bipyridyl)ruthenium core dendrimers were synthesized by coordinating dendritic polybipyridyl ligands with Ru(II) complexes, and the effect of the ligand and the dendritic network on the ECL characteristics were studied. Their electrochemical redox potentials, UV, photoluminescence (PL), and relative ECL intensities were also investigated in detail. The synthesized metallodendrimers exhibited strong metal-to-ligand charge transfer (MLCT) absorption at 428-451 nm and emission at 591-601 nm. Most of the newly synthesized metallodendrimers showed enhanced ECL intensities compared to the reference complex, [Ru(o-phen)₃](PF₆)₂. In particular, the ECL intensities of the six-armed heptanuclear ruthenium complexes were almost four times greater than that of [Ru(o-phen)₃]²⁺. These metallodendrimers could be utilized as efficient ECL materials and light emitting devices.     

Control of molecular weight of polystyrene using the reverse iodine transfer polymerization (RITP)-emulsion technique

The RITP-emulsion polymerization of styrene in the presence of molecular iodine has been successfully performed using potassium persulfate (KPS) as an initiator and 1-hexadecanesulfonate as an emulsifier under argon atmosphere at 80°C for 7 hrs in the absence of light. The effects of the iodine concentration, molar ratio between KPS and iodine, and solid contents on the molecular weight of polystyrene (PS) were studied. As the iodine concentration increased from 0.05 to 0.504 mmol under the fixed [KPS]/[I(2)] ratio at 4.5, the weight-average molecular weight of PS substantially decreased from 126,120 to 35,690 g/mol, the conversion increased from 85.0% to 95.2%, and the weight-average particle diameter decreased from 159 to 103 nm. In addition, as the ratio of [KPS]/[I(2)] increased from 0.5 to 6.0 at the fixed [I(2)] of 0.504 mmol, the weight-average molecular weight of PS decreased from 72,170 to 30,640 g/mol with high conversion between 81.7% and 96.5%. Moreover, when the styrene solid content increased from 10 to 40 wt.% at the fixed [KPS]/[I(2)] ratio of 4.5, the weight-average molecular weight of PS varied between 33,500 and 37,200 g/mol, the conversion varied between 94.9% and 89.7% and the weight-average diameter varied from 122 to 205 nm. Thus, the control of molecular weight of PS less than 100,000g/mol with high conversion (95%) and particle stability of up to 40 wt.% solid content were easily achieved through the usage of iodine with suitable ratio of [KPS]/[I(2)] in the RITP-emulsion polymerization technique, which is of great industrial importance.     

Artificial polymeric receptors on the cell surface promote the efficient cellular uptake of quantum dots

In our previous paper, secondary-amine appended cationic polymer 1 was used as a scaffold to display artificial receptors on a cell surface (R. Kamitani et al., ChemBioChem, 2009, 10, 230). This polymer can be retained on the cell surface for more than 30 min before being slowly internalized into the cells. In this study, our aim is to achieve the efficient internalization of quantum dots (QDs) into target cells via artificial receptors on the polymer. As a receptor molecule, N-acetylglucosamine (GlcNAc) moieties were introduced into the polymer, and GlcNAc binding protein-displaying QDs were used as a ligand. We found that ligand-presenting QDs could be internalized effectively into cells via polymer-mediated endocytosis, whereas QDs were not internalized into untreated cells. These data suggest that our method based on cell-surface engineering using polymers affords a new approach to the delivery of various poorly permeable nanoparticles into cells.