Rapid quantification of total microcystins in cyanobacterial samples by periodate-permanganate oxidation and reversed-phase liquid chromatography

Microcystins (MCs) comprise a family of more than 80 related cyclic hepatotoxic heptapeptides. Oxidation of MCs causes cleavage of the chemically unique C-20 beta-amino acid (2S, 3S, 8S, 9S)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid (Adda) amino to form 2-methyl-3-methoxy-4-phenylbutanoic acid (MMPB), which has been exploited to enable analysis of the entire family. In the present study, the reaction conditions (e.g. concentration of the reactants. temperature and pH) used in the production of MMPB by oxidation of cyanobacterial samples with permanganate-periodate were optimized through a series of well-controlled batch experiments. The oxidation product (MMPB) was then directly analyzed by high-performance liquid chromatography with diode array detection. The results of this study provided insight into the influence of reaction conditions on the yield of MMPB. Specifically, the optimal conditions, including a high dose of permanganate (>= 50 mM) in saturated periodate solution at ambient temperature under alkaline conditions (pH similar to 9) over 1-4 h were proposed, as indicated by a MMPB yield of greater than 85%. The technique developed here was applied to determine the total concentration of MCs in cyanobacterial bloom samples, and indicated that the MMPB technique was a highly sensitive and accurate method of quantifying total MCs. Additionally, these results will aid in development of a highly effective analytical method for detection of MMPB as an oxidation product for evaluation of total MCs in a wide range of environmental sample matrices, including natural waters, soils (sediments) and animal tissues. (C) 2009 Elsevier B.V. All rights reserved.

CaS:M (M=Ce~(3+), Dy~(3+), Eu~(2+), Cu)和Cas:Ce~(3+), M (M=Dy~(3+), Cu)的合成及其光致发光和热释发光性质研究

本文研究了Ce~(3+), Dy~(3+), Eu~(3+), Cu离子以及它们的共掺杂在硫化钙基质中的光致发光和热释发光性质，并用顺磁共振方法研究了磷光体中缺陷的性质及其对磷光体光致发光的影响。在CaS:Ce~(3＋)磷光体的稳定性影响因素，并经包膜后稳定性有所提高。计算了新的热释发光峰的陷阱参数。确定了热释发光的动力学级数。在Cas: Dy~(3+)磷光体中，研究了合成条件对磷光体发光性质的影响，讨论了新的热释发光峰的陷阱参数，确定了热释发光的动力学级数。在CaS:Dy~(3+)磷光体中，发现基质对Dy~(3+)离子具有敏化作用，讨论了黄兰比随Dy~(3+)离子浓度变化出现最大值的原因。计算了热释发光峰的陷阱参数，确定了热释发光的动力学级数。在CaS:Ce~(3+)，Dy~(3+)磷光体中，研究了Ce~(3+)离子的发光随Dy~(3+)离子浓度的变化，可能具有Dy~(3+) → Ce~(3+)的能量传递。计算了热释发光峰的陷阱参数，确定了热释发光的动力学级数。在CaS:Cu磷光体中，确定了不同Cu~+离子格位所产生的发射峰。根据磷光体中缺陷的转化过程解释了光致发光和热释发光性质随Cu离子浓度增加所呈现的规律性变化。通过实验证明磷光体有可能用作紫外剂量材料。本文还首次研究了CaS:Cu磷光体在UV（3bb nm)辐照下，发生Cu~+→Cu~(2+)的光氧化反应，通过EPR实验证明在Cu'_(Ca)→Cu_i~+处发生光氧化反应。在CaS:Ce~(3+),Cu磷光体中，观察到了Cu离子对Ce~(3+)离子的能量传递现象。在CaS:Eu~(2+)光体中，发光强度随Eu~(2+)离子浓度变化，显示浓度猝灭特性。本文还研究了CaS:Ce~(3+), CaS:Dy~(3+), CaS:Cu以及CaS:Ce~(3+), Cu磷光体中缺陷的性质，在CaS:Ce~(3+)中存在V_S~(2+)空位，并根据这一空位的性质，解释了发光光谱，并且选择适当的助熔剂使发光效率提高。在CaS:Dy~(3+)磷光体中，存在V_S~(2+)-V_(Ca)~(2-)空位对；在CaS:Cu和CaS:Ce~(3+), Cu磷光体中，存在V_S~(2+)空位和Cu'_(Ca)缺陷。

Unique properties of Ir/ZSM-5 catalyst for NO reduction with CO in the presence of excess oxygen

The reduction of NO with CO in the presence of excess oxygen was investigated over different noble metal catalysts for probing the relationship between catalytic properties and adsorption behaviors. Among the four precious metal catalysts investigated, Ir/ZSM-5 was found to be the only active one for NO reduction with CO under lean conditions. With the decreasing of the Ir content, higher NO conversion and CO selectivity was obtained. Temperature-programmed reaction (TPR) studies of NO/H-2/O-2 and NO/CO/O-2 showed that the Pt/ZSM-5 was active when H-2 was used as the reductant, whereas, the Ir/ZSM-5 was active when CO was the reducing agent. This difference is due to the different mechanisms of the two reactions. Temperature-programmed desorption (TPD) of NO, CO and O-2 showed that NO could dissociate more easily over the Ir/ZSM-5 than on the Pt/ZSM-5, while the oxidation of CO by O-2 proceeded more rapidly on the Pt/ZSM-5 than on the Ir/ZSM-5. The presence of excess O-2 inhibited drastically the dissociation of NO, which is considered as the key step for the NO-CO reaction. The high dissociation rate of NO over the Ir/ZSM-5 is visualized as the key factor for its superior high activity in NO reduction with CO under lean conditions. (C) 2002 Elsevier Science B.V. All rights reserved.

Unique electrochemiluminescence behavior of Ru(bpy)(3)(2+) in a gold/Nafion/Ru(bpy)(3)(2+) composite

The unique electrochemiluminescence (ECL) behavior of tris(bipyridine) ruthenium(II) (Ru(bpy)(3)(2+) immobilized in a gold/Nafion/Ru(bpy)(3)(2+) composite material was investigated. In this composite, the Ru(bpy)(3)(2+) ECL was found mainly occurred at 0-0.4 V during the cathodic scan process and the ECL peak was at about 0.1 V, which was quite different to the reported Ru(bpy)(3)(2+) ECL. Similar to the generally observed Ru(bpy)(3)(2+) ECL, the present ECL also could be enhanced by tri-n-propylarnine (TPA). It is also unique that in the presence of TPA, another ECL peak at about 0.38 V occurred.

A Unique Mn2Gd2 Tetranuclear Compound of p-tert-Butylthiacalix[4]arene

A calixarene complex with tetragonal (Mn2Gd2III)-Gd-II tetranuclear units was synthesized in solvothermal conditions, where the addition of a small amount of water was crucial for the formation of the target compound. In the structure, two tail-to-tail p-tert-butylthiacalixarenes are located in a C-shaped mode with a dihedral angle of 14.29 degrees but not in the conventional antiparallel arrangement and form a sandwich-like subunit with an in-between Mn2Gd2 unit. Both calixarenes assume similar cone shapes of C-2v symmetry but are pinched to different extents.

Unique structure and photoluminescence of Au/CdTe nanostructure materials

Unique nanostructure materials with highly ordered spherical aggregates have been obtained by self-organization of single CdTe nanocrystals using gold nanoparticles as seeds, and a red shift of the photoluminescence peak was observed.

Formation of a unique crystal morphology for the poly(ethylene glycol)-poly(epsilon-caprolactone) diblock copolymer

The crystallization behaviors of the poly(ethylene glycol)-poly(epsilon-caprolactone) diblock copolymer with the PEG weight fraction of 0.50 (PEG(50)-PCL50) was studied by DSC, WAXD, SAXS, and FTIR. A superposed melting point at 58.5 degrees C and a superposed crystallization temperature at 35.4 degrees C were obtained from the DSC profiles running at 10 degrees C/min, whereas the temperature-dependent FTIR measurements during cooling from the melt at 0.2 degrees C/min showed that the PCL crystals formed starting at 48 degrees C while the PEG crystals started at 45 degrees C. The PEG and PCL blocks of the copolymer crystallized separately and formed alternating lamella regions according to the WAXD and SAXS results. The crystal growth of the diblock copolymer was observed by polarized optical microscope (POM). An interesting morphology of the concentric spherulites developed through a unique crystallization behavior. The concentric spherulites were analyzed by in situ microbeam FTIR, and it was determined that the morphologies of the inner and outer portions were mainly determined by the PCL and PEG spherulites, respectively. However, the compositions of the inner and outer portions were equal in the analysis by microbeam FTIR.

Study of energy transfer between rare earth ions in CaS host by photoluminescence spectra

When CaS:Sm3+, Eu2+ is excited at 476.5 nm (Ar+), the emission spectra taken at room temperature and at 77 K are different, indicating that there are two competitive energy transfer processes-Sm3+ --> Eu2+ and Eu2+ --> Sm3+ with phonon participation. So, the luminescence intensity of Sm3+ increases first, and then decreases as the concentration of Eu2+ is increasing. (C) 2001 Elsevier Science Ltd. All rights reserved.

Photochromism in CaS : Sm

The photochromism in CaS:Sm (from white to pink) was observed for the first time by exposing it to ultraviolet light. The experiments results show that the absorption intensity of Sm2+ in the range of 500 similar to 600nm was strongly increased after irradiation. This reveals that there is the valence changing of Sm. If the sample was excited by visible light again, the pink color turned to white, indicating that CaS:Sm has potential application in the field of storage material.

CaS:Cu~+的热释发光性质

近年来对一些稀土和重金属离子在碱土金属硫化物的热释发光有过研究,,如CaS: Ce~(3+)和CaS:Bi~(3+)体系。N.Singh et al.(3)研究了CaS:Cu,Al以及CaS:Cu,Cl在UV辐照下热释发光峰值温度分别为80℃和75℃。我们用二甲亚砜硝酸钙为原料合成的CaS :Cu~+磷光体,在UV(366nm)辐照下,热释发光峰值温度大于100℃,峰值温度随铜离子浓度变化。