Sensitive determination of phenols in environmental water samples with SPE packed with bamboo carbon prior to HPLC

Bamboo carbon, an inexpensive, readily available material, has attracted great attention in recent years because of adsorptive properties. In this paper, the potential of bamboo carbon as a SPE adsorbent for the determination of phenols, was investigated. Phenols are important environmental contaminants that may adversely affect human health. Parameters influencing extraction efficiency, including type of eluent, eluent volume, amount of adsorbent, as well as sample pH, volume, and flow rate were investigated and optimized. The optimized results exhibited excellent linear relationships between peak area and phenol concentrations over the range of 2.0–100 ng/mL, with precision between 2.2–7.2%. The LODs were 0.06–0.4 ng/mL for the eight phenols tested. The proposed method has been successfully applied to the analysis of several real‐world environmental water samples. These results indicate that bamboo carbon may be used as a novel SPE adsorbent for the concentration and determination of phenols in real environmental water samples.     

A novel phosphorus‐containing thermotropic liquid crystalline poly(ester‐imide) with high flame retardancy

A novel phosphorus–nitrogen thermotropic liquid crystalline poly(ester‐imide) (PN‐TLCP) derived from p‐acetoxybenzoic acid (ABA), terephthalic acid (TPA), acetylated 2‐(6‐oxide‐6H‐dibenz<c,e><1,2>oxa phosphorin‐ 6‐yl)‐1,4‐dihydroxy phenylene (DOPO‐AHQ) and N,N'‐hexane‐1,6‐diylbis(trimellitimide) was prepared by melt transesterification. The chemical structure, the mesophase behavior, and the thermal properties of the copolymer were investigated with Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (¹H NMR), elemental analysis, wide‐angle X‐ray diffraction (WAXD), hot‐stage polarized light microscopy (PLM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). PN‐TLCP exhibited a nematic mesophase with a strong birefringence at a low and broad mesomorphic temperature ranging from 220 to 350°C, an initial flow temperature as low as about 190°C and a glass transition temperature of about 160°C. PN‐TLCP has also good thermal stability, high char residues and excellent flame retardancy (limiting oxygen index, LOI = 71 and UL‐94 V‐0 rating). Copyright © 2009 John Wiley & Sons, Ltd.     

Evaluation of lipid peroxidation inhibition and free radical scavenging abilities of 5,6,7-trimethoxy dihydroflavonols

Four naturally rare 5,6,7-trimethoxy-2,3-cis-dihydroflavonols(3-6) and two 5,6,7-trimethoxy-2,3-trans-dihydroflavonols(7-8) were designed and synthesized.Their antioxidative properties were evaluated by way of examining their scavenging capacities towards DPPH and O_2~(·-) free radicals,as well as by measuring their inhibitory ability against LPO.Both the 2,3-trans and the 2,3- cis conformers exhibited certain quenching abilities to DPPH and O_2~(·-) radicals,while most of the synthetic dihydroflavonols ...     

微波技术在Suzuki反应中的应用

与传统的加热方式相比,微波加热具有加热速度快、热效率高、节约能源、洁净、操作简单等优点,已成为重要的有机合成工具之一。钯催化的Suzuki反应提供了一种合成各种联芳烃的温和方法,具有较高的选择性。本文综述了近年来微波技术在Suzuki反应中的应用研究进展,涉及到各种不同的反应体系,重点讨论了KF/Al2O3负载钯和聚合物负载钯等非均相催化体系,对于均相反应则着重讨论无过渡金属和超低含量钯催化的Suzuki反应体系,还讨论了连续流动的微波反应器及Suzuki反应在有机合成中的应用。     

Photoelectrochemical kinetics of eosin y-sensitized zinc oxide films investigated by scanning electrochemical microscopy

Eosin Y is used as a sensitizer for nanoporous zinc oxide films for prospective applications in photoelectrochemical solar cells. The kinetics of the reduction of the intermittently formed photo-oxidized dye molecules by iodide ions in the electrolyte phase was investigated by using the feedback mode of scanning electrochemical microscopy (SECM). The bulk solution phase contained triiodide as electron transfer mediator, from which the ultramicroelectrode-generated iodide ions acted as electron donors for photo-oxidized Eosin Y molecules (D(+) (ads)) at the zinc oxide sample. Effective rate constants for the dye regeneration could be extracted from the SECM approach curves. The effective rate constants at different triiodide concentrations could be related to the rate constant for the reaction of the dissolved donor with photo-oxidized Eosin Y bound to ZnO, as well as to the overall rate of the photosensitization process. For the reaction D(+) (ads) + 1.5 I(-)-->D(ads) + 0.5 I(3) (-) a rate constant of k(ox) = (1.4+/-0.8)x10(8) cm(9/2) mol(-3/2) s(-1) was determined.     

Theoretical investigation of the decarbonylation of acetaldehyde by Fe+ and Cr+.

We report a comprehensive theoretical study on the decarbonylation of acetaldehyde by Fe+ and Cr+. Various intermediates, transition states, and products involved in the decarbonylation reactions are fully optimized at the B3LYP/6-311+G(2df,2pd) level of theory. The potential energy surfaces (PESs) corresponding to [M,O,C2,H4]+(M=Cr and Fe) are examined in detail using B3LYP and CCSD(T) methods, respectively. The validity of these theoretical methods is calibrated with respect to the available thermochemical data. Calculations suggest that the Cr+ mediated decarbonylation of acetaldehyde takes place in four steps on the sextet surface: encounter complexation, C-C activation, aldehyde H-shift, and nonreactive dissociation, in good accordance with the Co+ mediated decarbonylation of acetaldehyde [Zhao, Zhang, Guo, Wu, Lu, Chem. Phys. Lett. 2005, 414, 28], while for the Fe+/acetaldehyde system decarbonylation can occur on both the quartet and the sextet PESs. The quartet pathway, which experiences spin-orbit coupling between the two surfaces, is energetically more favorable; whereas along the sextet decarbonylation coordinate several high-energy barriers are revealed. The theoretical results are compared with the experimental product kinetic energy and angular distributions of decarbonylation of acetaldehyde by Fe+ and Cr+ measured using a crossed-beam technique [Sonnenfroh, Farrar, J. Am. Chem. Soc. 1986, 108, 3521].     

Colloidal woodpile structure: three-dimensional photonic crystal with a dual periodicity

With planar photolithography and self-assembly techniques, multilayer colloidal crystals with a woodpile structure were fabricated. They represent a new kind of photonic crystals, that is, three-dimensional (3D) photonic crystals with a dual periodicity; one comes from the face-centered cubic (fcc) structure within the colloidal crystal strips and the other one results from the periodic arrangement of the colloidal crystal strips.     

Surface enhanced Raman scattering based on silver dendrites substrate

A simple method of the reduction of AgNO3 by copper foil in aqueous medium was used to prepare silver dendrites, which can be used as a novel good reproducible surface enhanced Raman scattering (SERS) active substrate. The SERS spectra of 4-pyridinethiol on this novel substrate reflected the different SERS activities on the minuteness and strong Ag dendrites. The electromagnetic coupling enhancement and chemical enhancement mechanisms are used to explain the SERS effect.     

Synthesis of bridged and metallobridged bis(beta-cyclodextrin)s containing fluorescent oxamidobisbenzoyl linkers and their selective binding towards bile salts

A series of beta-cyclodextrin (beta-CD) dimers containing fluorescent 2,2'-oxamidobisbenzoyl and 4,4'-oxamidobisbenzoyl linkers--that is, 6,6'-[2,2'-oxamidobis(benzoylamino)]ethyleneamino-6,6'-deoxy-bis(beta-CD) (2), 6,6'-[2,2'-oxamidobis(benzoylamino)]diethylenediamino-6,6'-deoxy-bis(beta-CD) (3), 6,6'-[4,4'-oxamidobis(benzoylamino)]ethyleneamino-6,6'-deoxy-bis(beta-CD) (4), and 6,6'-[4,4'-oxamidobis(benzoylamino)]diethylenediamino-6,6'-deoxy- bis(beta-CD) (5)--were synthesized from the corresponding oxamidobis(benzoic acid)s through treatment with mono[6-aminoethyleneamino-6-deoxy]-beta-CD or mono[6-diethylenetriamino-6-deoxy]-beta-CD. Further treatment of 2-5 with copper perchlorate gave their Cu(II) complexes 6-9 in satisfactory yields. The conformation and binding behavior of 2-9 towards two bile salt guests--sodium cholate (CA) and sodium deoxycholate (DCA)--was comprehensively investigated by circular dichroism, 2D NMR spectroscopy, and fluorescence spectroscopy in Tris-HCl buffer solution (pH 7.2) at 25 degrees C. Thanks to the cooperative host-linker-guest binding mode, the stoichiometric 1:1 complexes formed by bis(beta-CD)s 2-5 with bile salts gave high stability constants (KS values) of up to 10(3)-10(4) M(-1). Significantly, benefiting from the intramolecular 1:2 or 2:4 binding stoichiometry, the resulting complexes of metallobis(beta-CD)s 6-9 with bile salts gave much higher KS values of up to 10(6)-10(7) M(-2). The enhanced binding abilities of bis(beta-CD)s and metallobridged bis(beta-CD)s are discussed from the viewpoints of induced-fit interactions and multiple recognition between host and guest.     

A theoretical study of the reaction of O(3P) with isobutene

The reaction of O((3)P) with isobutene ((CH(3))(2)C=CH(2)) is investigated using the unrestricted second-order M?ller-Plesset perturbation (UMP2) and complete basis set CBS-4M level methods. The minimum energy crossing point (MECP) between the singlet and triplet potential energy surfaces is located using the Newton-Lagrange method, and it is shown that the MECP plays a key role. The calculational results indicate that the site selectivity of the addition of O((3)P) to either carbon atom of the double bond of isobutene is weak, and the major product channels are CH(2)C(O)CH(3) + CH(3,) cis-/trans-CH(3)CHCHO + CH(3), (CH(3))(2)CCO + H(2), and CH(3)C(CH(2))(2) + OH, among which (CH(3))(2)CCO + H(2) is predicted to be the energetically most favorable one. The complex multichannel reaction mechanisms are revealed, and the observations in several recent experiments could be rationalized on the basis of the present calculations. The formation mechanisms of butenols are also discussed.