Enhanced photocatalytic activity of Eu2O3/Ta2O5 mixed oxides on degradation of rhodamine B and 4-nitrophenol

Europium oxide/tantalum pentoxide (Eu₂O₃/Ta₂O₅) mixed oxides with different Eu₂O₃ dopings were prepared by a single-step sol–gel process via hydrolysis of tantalum pentachloride in the presence of europium nitrate. The products were in the amorphous and orthorhombic phase structures, respectively, based on the different calcination temperatures (200 and 500 °C). Composition, morphology, phase structure, Eu₂O₃-doping mode in the Ta₂O₅ matrix and optical absorption property of the products were characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), field emission scanning electron microscopy (FESEM), X-ray diffraction patterns (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (UV–vis/DRS). The UV-light photocatalytic activity of the products was evaluated by degradation of aqueous rhodamine B (RB) and 4-nitrophenol (4-NP). The results showed that the photocatalytic activity of as-prepared Eu₂O₃/Ta₂O₅ was higher than that of pure Ta₂O₅ regardless of their phase structures. Among the tested samples, Eu₂O₃/Ta₂O₅ with 0.49% Eu loading obtained with 200 °C exhibited the highest activity to degradation of the above two model molecules. The reasons of this enhanced photocatalytic activity were discussed.     

Aquabis(2-methyl-4-oxopyrido[1,2-a]pyrimidin-9-olato)cobalt (II): Crystal Structure and Spectroscopic Properties

Abstract  

The title cobalt complex, [Co(C₉H₇N₂O₂)₂H₂O]H₂O, has been synthesized by the reaction of ligand, 9-hydroxy-2-methyl-4H-pyrido[1,2-a]pyrimidine-4-one (HL), and cobalt nitrate. The synthesized complex was characterized by IR, elemental analysis (C, H and N), mass spectrometry and X-ray crystallography. The structure was solved in monoclinic, space group P2₁/c with a = 14.4584(13), b = 6.9385(8), c = 18.045(2) ?, β = 94.8440(10), V = 1803.8(3) ?³, Z = 4, and with R _int = 0.034. The Co(II) complex, as shown by the single-crystal structure determination, existed as a mononuclear complex with distorted square-pyramidal geometry. The mental center was coordinated by two molecules from the bidentate ligand (HL) and an O atom from the coordinated water molecule. The intermolecular aromatic π–π stacking interactions generate discrete dimers. Furthermore, these discrete dimers were connected via O–H···O hydrogen bond in complex to form three-dimensional networks. At room temperature, the complex can emit blue luminescence at 430 nm in the solid state, while it about 42 nm blue-shifted in ethanol solution. Compared with free ligand, the luminescence was greatly intensified.     

Di-ionizable calix[4]arene-1,3-crown-4 ligands in 1,3-alternate,cone, and partial-cone conformations: synthesis and metal ion extractions

Di-ionizable calix[4]arene-1,3-crown-4 compounds locked in 1,3-alternate, cone, and partial-cone conformations are synthesized for evaluation in metal ion separations. The ionizable functions include carboxylic acid and N-(X)sulfonyl carboxamide groups in which the acidity is tuned by variation of the electron-withdrawing ability of X. Similar synthetic routes were employed for preparation of the cone and 1,3-alternate ligand series. A different preparative route utilizing protection and deprotection was required to obtain the partial-cone analogues. Ligand conformations were confirmed by their proton and/or carbon NMR spectra. X-ray diffraction verified an unusual 1,2-alternate conformation in the solid-state for one synthetic intermediate. Effects of ligand conformation and ionizable group variations on competitive solvent extractions of alkali and alkaline earth metal cations from aqueous solutions into chloroform were assessed. Single species solvent extractions of Hg²⁺ and Pb²⁺ were also performed.     

CdTe/CdS量子点与丝裂霉素的相互作用及其应用

在水相中合成了硫普罗宁(Tiopronin,TP)修饰的CdTe/CdS量子点(TP-CdTe/CdS QDs).利用紫外-可见吸收光谱、荧光光谱研究了TP-CdTe/CdS QDs与丝裂霉素(mitomycin C,MMC)的相互作用机理.在pH=7.6的tris-HCl缓冲溶液介质中,TP-CdTe/CdS QDs与MMC相互作用,使TP-CdTe/CdS QDs的荧光发生猝灭,并且QDs的荧光强度与MMC的浓度有良好的线性关系(r=0.9991),线性范围4.7×10-9～1.2×10-8g/mL,检出限(3σ)为1.4×10-g/mL.此方法快速简便,用于尿样中丝裂霉素的测定,实验结果令人满意.     

Pd-catalyzed decarboxylative couplings of arenecarboxylic acids with aryl iodides

The combination of palladium chloride with BINAP shows high efficiency in the decarboxylative cross-coupling reactions of arenecarboxylic acids with aryl iodides. The reactions proceed smoothly to generate the corresponding biaryl compounds in good to excellent yields.     

Extraction of pesticides in water samples using vortex-assisted liquid–liquid microextraction

A simple solvent microextraction method termed vortex-assisted liquid–liquid microextraction (VALLME) coupled with gas chromatography micro electron-capture detector (GC-μECD) has been developed and used for the pesticide residue analysis in water samples. In the VALLME method, aliquots of 30 μL toluene used as extraction solvent were directly injected into a 25 mL volumetric flask containing the water sample. The extraction solvent was dispersed into the water phase under vigorously shaking with the vortex. The parameters affecting the extraction efficiency of the proposed VALLME such as extraction solvent, vortex time, volumes of extraction solvent and salt addition were investigated. Under the optimum condition, enrichment factors (EFs) in a range of 835–1115 and limits of detection below 0.010 μg L⁻¹ were obtained for the determination of target pesticides in water. The calculated calibration curves provide high levels of linearity yielding correlation coefficients (r²) greater than 0.9958 with the concentration level ranged from 0.05 to 2.5 μg L⁻¹. Finally, the proposed method has been successfully applied to the determination of pesticides from real water samples and acceptable recoveries over the range of 72–106.3% were obtained.     

Nonexistence of solutions for singular elliptic equations with a quadratic gradient term

This paper concerns the nonexistence of solutions for singular elliptic equations with a quadratic gradient term. The main results complement and partly extend some works by Arcoya et al. (2009) [1]. As a by-product of the main results, we fill in a gap in one of their works.     

双热源复合换热器复合换热温差影响因素分析

空气-水双热源复合换热器是太阳能-空气双热源复合热泵系统的核心部件,空气-水双热源复合换热器的有效复合换热温差对空气-水双热源复合换热器的换热性能以及太阳能-空气双热源复合热泵的系统性能具有重要影响。建立了空气-水双热源复合换热器和太阳能-空气双热源复合热泵系统的数学模型,利用数学模拟的方法研究了空气-水双热源复合换热器结构参数,即内外管径、翅片间距对有效复合换热温差的影响。模拟结果表明:空气-水双热源复合换热器的有效复合换热温差随内管管径的减小、外管管径的增大以及翅片间距的减小而增大。     

Homogeneous time-resolved fluoroimmunoassay of 3,5,3'-triiodo-l-thyronine in human serum by using europium fluorescence energy transfer

A sensitive homogeneous time-resolved fluoroimmunoassay method for 3,5,3'-triiodo-l-thyronine (T3) based on the fluorescence resonance energy transfer (FRET) from a fluorescent Eu(3+) complex, {[(4,6-dichloro-1,3,5-triazin-2-yl)amino-biphenyl-4'-yl]-2,2':6',2'-terpyridine-6,6'-diyl}bis(methylenenitrilo) tetrakis(acetate)-Eu(3+) (DTBTA-Eu(3+)) (lambda(ex,max)=335nm, lambda(em,max)=615nm), to an organic fluorescence dye Cy5 has been developed. The new assay system combined the use of DTBTA-Eu(3+)-labeled T3-bovine serum albumin (BSA) conjugate and Cy5-labeled anti-T3 monoclonal antibody for a competitive-type immunoassay. After the competitive reactions of DTBTA-Eu(3+)-labeled T3-BSA and T3 sample with Cy5-labeled anti-T3 antibody, the T3 concentration was measured with a time-resolved mode by monitoring the sensitized emission of Cy5 derived from FRET in a homogeneous format. The method gives the detection limit of 0.26ng/ml. The coefficient variations of the method are less than 2.0% and the recoveries are in the range of 80-111% for serum sample measurement. The concentrations of T3 in 30 human serum samples were determined, and the results were compared with those of the independently determined by a radio-immunoassay method. A good correlation was obtained with a correlation coefficient of 0.989.