Synthesis of Single Crystalline ZnO Nanoparticles by Salt-Assisted Spray Pyrolysis

LiNO₃ was used as a shield in the preparation of single crystalline ZnO particles by a spray pyrolysis process in order to prevent agglomeration and enhance the crystallinity of the ZnO. LiNO₃ was added to a precursor solution of zinc acetate dihydrate prior to its atomization by means of an ultrasonic transducer. Agglomerate-free particles having a mean particle size of 26 nm were successfully obtained after washing the product. X-ray diffractometry, field-emission scanning electron micrograph and transmission electron micrograph data indicate that the size and morphology of ZnO were strongly influenced by the operating temperature used and the residence time of the particle in the reactor.     

Thermal intramolecular electron transfer reactions of [N,N′-ethylene-bis(salicylideneaminato)](2,4-pentanedionato)cobalt(III) complexes in the solid state

The title complexes with the formula Co(salen)L where L is a series of 2,4-pentanedionates underwent thermally induced one-electron transfer reactions from L to Co(III). The reaction left behind a stoichiometric amount of the crystalline Co^II(salen) complex which took up oxygen in a molar ratio of Co:O₂ = 2:1. The kinetic analyses showed that the electron transfer reaction rate was apparently dominated by activation entropy rather than by activation enthalpy.     

Total synthesis of (±)-obaberine [studies on the syntheses of heterocyclic compounds. Part CCCXLIX ]

Cyclization of one of two cyclic bisamides (III and IX), followed by reduction and successive methylation, gave our expected bis-coclaurine derivatives, one of which was identical with O-methyloxyacanthine, namely natural obaberine (I).     

Electrochemiluminescence of Ru(II) complexes immobilized on a magnetic microbead surface: distribution of magnetic microbeads on the electrode surface and effect of azide ion

The electrochemiluminescence (ECL) of magnetic microbeads modified with tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)3]2+) was studied in the presence of tri-n-propylamine (TPA) to develop highly sensitive ECL detection system, where the employed microbead has a diameter of 4.5 microm. The ECL signal of the [Ru(bpy)3]2+ derivative-modified magnetic microbeads was found to be affected by the geometrical distribution of the magnetic microbeads on the electrode surface. The ECL peak intensity increased with increasing the number of the beads on the electrode surfaces up to 1.6 x 10(6) beads cm(-2), although above 1.6 x 10(6) beads cm(-2), it decreased. The ECL decrease arises from the physical prevention of the ECL from reaching the photomultiplier tube by the excessive beads. The observed peak ECL signal of the [Ru(bpy)3]2+ derivative-modified magnetic microbeads in the presence of NaN3, which serves as a preservative substance, mainly appeared at a potential of +0.90 V vs Ag/AgCl where [Ru(bpy)3]2+ is hardly oxidized, whereas the ECL signal in the absence of NaN3 appeared at a potential of +1.15 V. The presence of NaN3 on the electrode surface retards formation of an oxide layer on the electrode surfaces and promotes TPA oxidation. The ECL response at +0.90 V was mainly attributed to ECL reaction of excited-state [Ru(bpy)3]2+* formed by oxidation of [Ru(bpy)3]+ with TPA radical cation, where the [Ru(bpy)3]+ was generated by reduction of [Ru(bpy)3]2+ with TPA radical.     

Simple one-step extraction and cleanup by pressurized liquid extraction for gas chromatographic-mass spectrometric determination of pesticides in green leafy vegetables

A simple one-step extraction and cleanup using a pressurized liquid extraction method was developed for the gas chromatographic-mass spectrometric determination of pesticides in vegetables. The pressurized liquid extraction conditions were optimized and cleanup agents were evaluated. The investigated pesticides included six insecticides, chlorpyrifos methyl, pirimiphos-methyl, malathion, chlorpyrifos, O-ethyl O-4-nitrophenylphenyl phosphonothioate (EPN) and permethrins, a fungicide, isoprothiolane, and a herbicides, thiobencarb. The cleanup agent and a mixture of the vegetable and anhydrous sodium sulfate were separately packed in an extraction vessel. A transparent and colorless extract was obtained using graphitized carbon as the cleanup agent. The overall recoveries were 71-103% and the relative standard deviations ranged from 5.6 to 24%. The limit of detection values were 3-8 microg kg(-1). This method was successfully applied to green leafy vegetables.     

Phthalocyanine-based fluorescence probes for detecting ascorbic acid: phthalocyaninatosilicon covalently linked to TEMPO radicals

We have applied phthalocyaninatosilicon (SiPc) covalently linked to one or two tetramethyl-1-piperidinyloxyl (TEMPO) radicals as fluorescence probes for detecting ascorbic acid in biological systems.     

Direct synthesis of cup-stacked carbon nanofiber microspheres by the catalytic pyrolysis of poly(ethylene glycol)

Uniformly sized microspheres tangled with cup-stacked carbon nanofibers (CSCNFs) were directly synthesized by the pyrolysis of poly(ethylene glycol) (PEG) with a nickel catalyst. A PEG/Ni membrane was prepared on a silicon wafer surface by heating it to 750 °C at a heating rate of 15 °C min(-1). The wafer was heated to a temperature of 400 °C and was held at that temperature for 1 h before raising the temperature to 750 °C for 10 min to form the CSCNF microspheres. The final CSCNF microspheres and the intermediates were evaluated using scanning electron microscopy, transmission electron microscopy, X-ray diffractometry, and Raman spectroscopy to elucidate the growth mechanism. Furthermore, the CSCNF microspheres were successfully dispersed and maintained their spherical shape in an aqueous solution containing 0.5% Nafion. The CSCNF microspheres have the potential to work as a sophisticated carrier with high adsorption and fast electron-transfer exchange properties based on the graphene edges of the nanofiber surface.     

Wave localization in randomly disordered layered three-component phononic crystals with thermal effects

In this paper, the propagation and localization of elastic waves in randomly disordered layered three-component phononic crystals with thermal effects are studied. The transfer matrix is obtained by applying the continuity conditions between three consecutive sub-cells. Based on the transfer matrix method and Bloch theory, the expressions of the localization factor and dispersion relation are presented. The relation between the localization factors and dispersion curves is discussed. Numerical simulations are performed to investigate the influences of the incident angle on band structures of ordered phononic crystals. For the randomly disordered ones, disorders of structural thickness ratios and Lamé constants are considered. The incident angles, disorder degrees, thickness ratios, Lamé constants and temperature changes have prominent effects on wave localization phenomena in three-component systems. Furthermore, it can be observed that stopbands locate in very low-frequency regions. The localization factor is an effective way to investigate randomly disordered phononic crystals in which the band structure cannot be described.     

Reconstruction of glycan chains of glycoprotein : Branching mannopentaoside and mannohexaoside

Synthetic routes to the branching mannopentaoside 4 and mannohexaoside 5 are described employing properly protected mannobioside 13 as a key intermediate.