Properties of the perovskites, SrMn1−xFexO3−δ (x=1/3, 1/2, 2/3)

The SrMn_1−xFe_xO_3−δ (x=1/3, 1/2, 2/3) phases have been prepared and are shown by powder X-ray and neutron (for x=1/2) diffraction to adopt an ideal cubic perovskite structure with a disordered distribution of transition-metal cations over the six-coordinate B-site. Due to synthesis in air, the phases are oxygen deficient and formally contain both Fe³⁺ and Fe⁴⁺. Magnetic susceptibility data show an antiferromagnetic transition at 180 and 140 K for x=1/3 and 1/2, respectively and a spin-glass transition at 5, 25, 45 K for x=1/3, 1/2 and 2/3, respectively. The magnetic properties are explained in terms of super-exchange interactions between Mn⁴⁺, Fe^(4+δ)+ and Fe⁽³⁺⁾⁺. The XAS results for the Mn-sites in these compounds indicate small Mn-valence changes, however, the Mn-pre-edge spectra indicate increased localization of the Mn-e_g orbitals with Fe substitution. The Mössbauer results show the distinct two-site Fe⁽³⁺⁾+/Fe^(4+δ)+ disproportionation in the Mn- substituted materials with strong covalency effects at both sites. This disproportionation is a very concrete reflection of a localization of the Fe-d states due to the Mn-substitution.     

Synthesis,Structural Characterization and Biological Activity of Cu(II) Compounds Incorporating Pyrazole‐derived Ligand: Effect on Cell Growth in Human Colorectal Carcinoma

A series of Cu(II) compounds containing neutral multi‐dentate ligand [2,6‐diisopropylphenyl]‐bis[(1‐H‐pyrazol‐1‐yl)methyl]amine ( L₁ ) and pyrazole dimethoxethyl ligand [(1‐H‐pyrazol‐1‐yl)methyl]‐bis(2‐methoxyethyl)amine ( L₂ ) were synthesized. Reactions of L₁ and L₂ with copper(II) chloride generate L₁CuCl₂ ( 1 ) and L₂CuCl₂ ( 2 ), respectively. Compounds 1 and 2 have been characterized by elemental analysis and X‐ray single crystal diffractometry. The effects of compounds 1 and 2 on the cell viability of various human cancer cells (including A549, COLO 205, HT‐29, Hep3B, HepG2, Huh7, and PCL5 cells) were investigated. The results indicate that compound 2 has a strong inhibitory effect on cell growth in human colorectal carcinoma cells (COLO 205 cells and HT‐29 cells).     

Synthesis of substituted α-tetralones and substituted 1-naphthols via regioselective ring expansion of 1-acyl-1-indanol skeleton

Substituted 1-acyl-1-indanols were prepared using the corresponding readily commercially available substituted indanones as starting materials. Treatment of each 1-acyl-1-indanol derivative with sodium methoxide in hot methanol furnished a regiospecific 2-hydroxy-α-tetralone derivative, which was an α-keto rearrangement product. Each substituted 2-hydroxy-α-tetralone then underwent dehydration to afford the corresponding 1-naphthol derivative.     

Multi-wall carbon nanotubes (MWCNTs)-doped polypyrrole DNA biosensor for label-free detection of genetically modified organisms by QCM and EIS

In this paper, we describe DNA electrochemical detection for genetically modified organism (GMO) based on multi-wall carbon nanotubes (MWCNTs)-doped polypyrrole (PPy). DNA hybridization is studied by quartz crystal microbalance (QCM) and electrochemical impedance spectroscopy (EIS). An increase in DNA complementary target concentration results in a decrease in the faradic charge transfer resistance (R_ct) and signifying “signal-on” behavior of MWCNTs-PPy-DNA system. QCM and EIS data indicated that the electroanalytical MWCNTs-PPy films were highly sensitive (as low as 4 pM of target can be detected with QCM technique). In principle, this system can be suitable not only for DNA but also for protein biosensor construction.     

Lengthy Rod Formation from a Poly(oxyalkylene)amine‐Intercalated Smectite Clay by a Self‐Aligning Mechanism

Summary: A micrometer rod morphology was produced by self‐assembly of poly(oxypropylene)amine (POP‐amine) modified montmorillonite. The requisite primary structure was prepared by intercalation of the layered clay with POP‐amine salts. During the drying process, the primary units self‐assemble into micro‐rods that are 100–800 nm wide and 2–40 μm long. The stacking process may involve two complimentary forces – the POP hydrophobic effect and the silicate ionic interaction – acting in separate directions.

Lengthy rod formation from Poly(oxyalkylene)amine‐intercalated smectite clay.     

Photooxidation of Methane over TiO2

Fourier‐transform infrared spectroscopy has been employed to investigate the adsorption and photo‐oxidation of CH₄ over powdered TiO₂. The interaction between the CH₄ and TiO₂ surface is weak. It is found that no CH₄ molecules are adsorbed on the surface at 35 °C in a vacuum. Under UV irradiation, CH₄ decomposes to form CO_(a), CO_2(g), H20_(a), and HCOO_(a) in the presence of O₂. The photoreaction rate is retarded and only small amounts of CO_(a) and HCOO_(a) are formed in the absence of O₂. It is observed that the oxygen atoms of O₂ are incorporated into these photoproducts as ¹⁸O₂ is used. The major ¹⁸O‐containing products are C¹⁸O_(a), C¹⁸O_2(g), H₂ ¹⁸O_(a), HC¹⁶O¹⁸O_(a), and HC¹⁸O¹⁸O_(a) after 180 min UV irradiation. However, the extent of ¹⁸O incorporating into the adsorbed formate is dependent on UV irradiation time. In the early stage of UV irradiation HC¹⁶O¹⁶O_(a) is the major formate form indicating the involvement of TiO₂ lattice oxygens for its formation, but HC¹⁸O¹⁸O_(a) becomes the major one after 180 min indicating the involvement of ¹⁸O₂. Formate on TiO₂ further photodecomposes to CO_2(g), but not to CO_(a). CO_(a) formation is directly from CH₄ photodecomposition with the participation of TiO₂ lattice oxygens and O₂.     

Comparison of electrospray ionization,atmospheric pressure chemical ionization and atmospheric pressure photoionization for determining estrogenic chemicals in water by liquid chromatography tandem mass spectrometry with chemical derivatizations

This study compared the sensitivities and matrix effects of four ionization modes and four reversed-phase liquid chromatographic (LC) systems on analyzing estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-ethinylestradiol (EE2), 4-nonylphenol (NP), 4-tert-octylphenol (OP), bisphenol A (BPA) and their derivatives of dansyl chloride or pentafluorobenzyl bromide (PFBBr) in water matrixes using a triple-quadrupole mass spectrometer with selected reaction monitoring (SRM). The four probes were electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), atmospheric pressure photoionization (APPI) and APCI/APPI; the four LC systems were ultra-performance liquid chromatography (UPLC) with or without post-column split, a mixed-mode column and two-dimensional LC (2D-LC). Dansylated compounds with ESI at UPLC condition had the most intense signals and less matrix effects of the various combinations of ionization and LC systems. The on-column limits of detection (LODs) of dansylated estrogens by SRM were 0.05–0.20 pg, and the LODs in sewage treatment plant effluent and in river water were 0.23–0.52 and 0.56–0.91 ng/L, respectively. The LODs using selected ion monitoring (SIM) reached low ng/L levels in real samples and measured concentrations were comparable with those of SRM.     

Absorption and distribution of lupeol in CD‐1 mice evaluated by UPLC–APCI+–MS/MS

Lupeol is a dietary triterpene that shows limited water solubility, which affects its bioavailability. It is well known that poor oral bioavailability is one of the major causes of therapeutic variability. Lupeol has been reported to have multiple biological activities; however, there are no reports about its bioavailability. Therefore, the objective of this research was to evaluate the systemic bioavailability of lupeol. An experimental strategy with three groups of female CD‐1 strain mice was proposed (control, olive oil and lupeol in olive oil), at six experimental times (0.5, 2, 4, 8, 12 and 24 h) with four animals per experimental point. Mice were sacrificed for organs, urine, feces and blood collection. Lupeol was extracted from samples and analyzed by UPLC–APCI⁺–MS/MS, obtaining the pharmacokinetics parameters time to peak concentration 6.444 ± 0.851 h and peak concentration 8.071 ± 2.930 μg/mL. Study of direct digestion and absorption in various organs showed important concentrations of lupeol at earlier post‐administration times (stomach, 137.25 ± 19.94 ng/mg and small intestine, 99.00 ± 12.99 ng/mg). The main excretion route was fecal, with a peak at 12 h post‐administration (163.28 ± 9.83 μg/mg). Absorption of lupeol by the animals was better than expected despite its nonpolar nature (extent of absorption F = 0.645 ± 0.0581).     

Stable second‐order nonlinear optical poly(amide–imide)/inorganic materials via simultaneous sequential self‐repetitive reaction and sol–gel process

A series of thermally stable organic/inorganic second‐order nonlinear optical (NLO) composites via sequential self‐repetitive reaction (SSRR) and sol–gel process has been developed. This SSRR is based on carbodiimide (CDI) chemistry. The difunctional azo chromophores (2,4‐diamino‐4′‐(4‐ nitrophenyl‐diazenyl)azobenzene (DNDA)) was reacted with excessive amount of 4, 4′‐methylene‐ diphenylisocyanate (MDI) to form poly‐CDI, and subsequently trimellitic anhydride (TMA) was added to obtain poly(N‐acylurea). The organic/inorganic composites containing prepolymer of phenyltriethoxysilane (PTEOS) and poly(N‐acylurea) in different weight ratios (10:90, 30:70, 50:50, 70:30, 90:10 wt%) were prepared, respectively. The moderate glass transition temperature (T_g) characteristic of the poly(N‐acylurea) allows the NLO‐active polymer to achieve high poling efficiency. After in situ poling and curing process, the T_gs of the composites were elevated, and higher than that of the pristine poly(amide–imide) sample. Electro‐optical (EO) coefficients (r₃₃) of about 5.5 ～ 18.0 pm/V at 830 nm were obtained. Excellent temporal stability at 100°C, and waveguide characteristics (3.1–4.2 dB/cm at 830 nm) were also obtained for these composites. Copyright © 2008 John Wiley & Sons, Ltd.     

Stability of Parathion-Methyl,Methiocarb, DDT and 2,4-D in Solid-Phase Extraction Precolumns Packed with a Polymeric Reversed Phase

Abstract

The stability of parathion-methyl, methiocarb, DDT and 2,4-D, adsorbed on the polymeric PLRP-S phase packed in small stainless steel precolumns was examined, with a view to propose the use of these precolumns as alternative means for the transport of water samples. First, water samples spiked with the studied pesticide at low μg/l concentration levels were extracted and preconcentrated in the precolumns, using appropriate conditions for a total recovery. Then, the precolumns were stored at room temperature (15—20°C) or at 35°C for different time periods. At the end of the respective period each precolumn was coupled to an HPLC column via a switching valve and was on-line analyzed by reversed phase chromatography with UV detection. The four pesticide recoveries after one week in the precolumn at room temperature were higher than 90%. The same was true at 35°C except for DDT, which suffered a 30% degradation in one week. Further studies showed that DDT and parathion-methyl were stable at least for five weeks in precolumns stored at room temperature. Methiocarb also was stable for this period but storing the precolumns at 4°C.