Highly sensitive, selective, and rapid fluorescence Hg2+ sensor based on DNA duplexes of poly(dT) and graphene oxide

Coupling T base with Hg(2+) to form stable T-Hg(2+)-T complexes represents a new direction in detection of Hg(2+). Here a graphene oxide (GO)-based fluorescence Hg(2+) analysis using DNA duplexes of poly(dT) that allows rapid, sensitive, and selective detection is first reported. The Hg(2+)-induced T(15)-(Hg(2+))(n)-T(15) duplexes make T(15) unable to hybridize with its complementary A(15) labelled with 6'-carboxyfluorescein (FAM-A(15)), which has low fluorescence in the presence of GO. On the contrary, when T(15) hybridizes with FAM-A(15) to form double-stranded DNA because of the absence of Hg(2+), the fluorescence largely remains in the presence of GO. A linear range from 10 nM to 2.0 μM (R(2) = 0.9963) and a detection limit of 0.5 nM for Hg(2+) were obtained under optimal experimental conditions. Other metal ions, such as Al(3+), Ag(+), Ca(2+), Ba(2+), Mg(2+), Zn(2+), Mn(2+), Co(2+), Pb(2+), Ni(2+), Cu(2+), Cd(2+), Cr(3+), Fe(2+), and Fe(3+), had no significant effect on Hg(2+) detection. Moreover, the sensing system was used for the determination of Hg(2+) in river water samples with satisfactory results.     

Mixed hemimicelles solid-phase extraction of chlorophenols in environmental water samples with 1-hexadecyl-3-methylimidazolium bromide-coated Fe3O4 magnetic nanoparticles with high-performance liquid chromatographic analysis

In this paper, 1-hexadecyl-3-methylimidazolium bromide (C₁₆mimBr)-coated Fe₃O₄ magnetic nanoparticles (NPs) as an adsorbent of mixed hemimicelles solid-phase extraction was investigated for the preconcentration of two chlorophenols (CPs) in environmental water samples prior to HPLC with UV detection at 285 nm. The high surface area and excellent adsorption capacity of the Fe₃O₄ NPs after modification with C₁₆mimBr were utilized adequately in the SPE process. By the rapid isolation of Fe₃O₄ NPs through placing a strong magnet on the bottom of beaker, the time-consuming preconcentration process of loading large volume sample in conventional SPE method with a column can be avoided. A comprehensive study of the adsorption conditions such as the zeta-potential of Fe₃O₄ NPs, added amounts of C₁₆mimBr, pH value, standing time and maximal extraction volume were also presented. Under optimized conditions, two analytes of 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) were quantitatively determined. The method was then used to determine the two CPs in real environmental water samples. The accuracy of method was evaluated by recovery measurements on spiked samples. Good recovery results (74–90%) were achieved. It is important to note that satisfactory preconcentration factors and extraction recoveries for the two CPs were obtained with only a small amount of Fe₃O₄ NPs (40 mg) and C₁₆mimBr (24 mg).     

Synthesis and Crystal Structures of 4-Chloro-<Emphasis Type="Italic">N′</Emphasis>-(4-hydroxy-3-nitrobenzylidene)benzohydrazide monohydrate and 4-Chloro-<Emphasis Type="Italic">N′</Emphasis>-(4-hydroxy-3-methoxybenzylidene)benzohydrazide monohydrate

Abstract  

Two new hydrazone compounds, 4-chloro-N′-(4-hydroxy-3-nitrobenzylidene)benzohydrazide monohydrate (1) and 4-chloro-N′-(4-hydroxy-3-methoxybenzylidene)benzohydrazide monohydrate (2), were synthesized and characterized by physico-chemical methods and single crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic space group P2₁/c with unit cell parameters a = 23.257(3) ?, b = 4.829(1) ?, c = 12.763(2) ?, β = 96.017(2)°, V = 1425.5(5) ?³, Z = 4, R ₁ = 0.0525, and wR ₂ = 0.1120. Compound 2 crystallizes in the monoclinic space group P2₁/c with unit cell parameters a = 8.103(3) ?, b = 21.321(3) ?, c = 10.594(3) ?, β = 120.281(2)°, V = 1580.5(8) ?³, Z = 4, R ₁ = 0.0480, and wR ₂ = 0.1078. Both compounds contains a hydrazone molecule and a water molecule. The crystals of the compounds are stabilized by N–H···O, O–H···O, and O–H···N hydrogen bonds.     

红外热像法研究屋顶绿化对热环境的影响

该研究应用红外热像法测量绿化屋顶的表面温度,进而分析屋顶绿化对热环境的影响。通过采集斜坡屋顶绿化、轻型屋顶绿化和蓄水覆土屋顶绿化在阴天、雨后一天、晴天三种天气条件下的红外热像图,分析对比三种绿化屋顶在同一天内及三种不同天气条件下的温度变化。结果表明绿化屋顶表面温度的变化主要受太阳辐射和气温的影响,而蓄水覆土绿化屋顶的表面温度还受到其含水量的影响;屋顶绿化在夏季天气条件下可有效降低屋顶的表面温度、减小温度波动幅度,有利于改善城市热环境。     

A stannum-bismuth composite film electrode for simultaneous determination of zinc(II) and cadmium(II) using differential pulse anodic stripping voltammetry

The development and use of 'green' electrode materials is extremely attractive for the routine use of disposable metal sensors. Bismuth is an environmentally-friendly element and a bismuth film electrode was proposed as an alternative to mercury film electrodes. Compared with bismuth, stannum is a more 'environmentally friendly' material. The stannum-bismuth composite film electrode prepared by the in situ electrodeposition of stannum and bismuth on the glassy carbon substrate is reported for the first time. Compared with bismuth film and stannum film electrodes, the stannum-bismuth composite film electrode revealed better electroanalytical performance, and can be used as a possible alternative electrode for electrochemical stripping analysis of trace heavy metals.     

带负顾客的Geom/Geom/1单重休假排队(英文)

本文研究了正负顾客到达均服从几何分布,服务台在工作休假期以较低的服务速率运行的 Geom/Geom/1休假排队.运用嵌入马尔科夫链和矩阵分析法,得到了系统中等待队长和稳态队长的概率母函数,并从证明过程和结果中,分别得到了服务台在闲期、忙期、工作休假期、正规忙期的概率.     

几种黄酮类化合物荧光光谱的量子化学研究

采用量子化学半经验方法AM1对3种黄酮类化合物的荧光光谱进行了理论研究。在B3LYP/6-311G水平下优化了3种化合物的几何构型,在振动分析中,均未出现虚频率。在此基础上,采用单激发组态相互作用方法(CIS)计算其荧光光谱,计算结果与实验值基本吻合。本文对黄酮类化合物的开发与应用具有一定的理论参考价值。     

高铁酸钾降解苯并芘的荧光光谱研究

在优化的反应条件下, 研究了高铁酸钾与苯并芘(BaP)的降解反应过程, 通过联合应用同步, 三维(EEM), 时间扫描及荧光光度定量等多种荧光光谱分析方法所提供的多角度的荧光光谱信息, 揭示了BaP分子在降解过程中浓度随时间变化规律, 尤其高铁酸钾与BaP作用过程的动力学特征。同步荧光和三维荧光光谱共同揭示出, 高铁酸钾在20 s内能降解91%的BaP, 60 s以后反应趋于缓慢的变化规律; 由时间扫描荧光光谱结合发射和同步两种荧光光度定量方法, 便捷地获得了高铁酸钾与BaP的反应过程中的动力学方程: ln(F₀/F_t)=0.563 2t+0.171 2, (R2=0.994 2), 由此推测高铁酸钾与BaP的反应过程符合一级反应动力学规律。为研究高铁酸钾降解其他污染物反应过程的机理提供了十分有益的参考。     

联用多种荧光光谱研究高铁酸钾对荧蒽的降解

应用多种荧光光谱追踪了高铁酸钾对荧蒽的降解过程, 包括发射, 同步, 三维(EEM), 时间扫描及光度定量所提供丰富的关于整个降解反应的信息, 探讨了高铁酸钾对荧蒽分子的降解特性及其随时间变化规律; 分别对该降解过程中的不同时段(20, 40, 70 s)的时间扫描荧光曲线进行拟合,并由此推测了高铁酸钾降解荧蒽的动力学特征。结果显示, 相同的反应时段, 各荧光光谱反映的高铁酸钾对荧蒽分子的降解率非常接近: t=10 s约55%; t=25 s约81%; t=40 s约91%。各时段的降解过程中均未出现新的荧光特性; t≤20 s, 为该降解反应的决定性阶段, 此阶段的降解过程最为接近线性关系; t>20 s, 降解过程偏离线性关系越来越远。整个降解过程可以近似地用一级反应动力学规律描述。     

氨基多元膦酸水处理剂的合成及性能分析

以N.N-二甲基甲酰胺、三氯化磷为主要原料合成了氨基多元膦酸水处理剂-二甲基甲叉二膦酸.并对其缓蚀阻垢能力进行了考察.试验表明:二甲基甲叉二膦酸具有很好的缓蚀效果,在与Zn2+复配或采用预膜处理后其缓蚀性能更为优越.对碳酸钙、硫酸钙和磷酸钙具有很好的抑制能力,即使在Ca2+浓度较高体系也有较好的阻垢效果.