氢氧化铯催化端炔氢硒化:高立体区域选择性合成(E)-1-芳硒基烯烃

在催化量氢氧化铯存在下,端炔与硒酚在N,N-二甲基甲酰胺(DMF)中、室温、氮气保护下,发生亲核加成反应,高收率、高立体选择性合成一系列(E)-1-芳硒基烯.反应机理为氢氧化铯与硒酚反应产生的芳硒化铯,随后对端炔进行亲核加成,形成的烯基负离子水解得到产物.这方法为不活泼端炔氢硒化提供了一条新的和简便途径.

H_2^(80)Se分子的26个振动带转动结构的全拟合分析

阐述了全拟合分析方法的理论基础，通过对Ｈ２８０Ｓｅ分子２４个已知转动结构振动带的３５１６个上态能级的全拟合分析，得到１１２个基本光谱参数，拟合偏差为１０．６×１０－３ｃｍ－１。用这套基本光谱参数精确预言了首次记录的Ｈ２８０Ｓｅ分子（５００，Ａ１）和（４０１，Ｂ２）局域模振动带的转动结构，并在简正模和局域模下分别拟合得到有效振转光谱参数。将归属得到的Ｈ２８０Ｓｅ分子（５００，Ａ１）和（４０１，Ｂ２）振动带的２５２个上态能级并入全拟合中，得到１１４个基本光谱参数，拟合偏差为９．６２×１０－３ｃｍ－１。

Preparation of high pure tellurium from raw tellurium containing Cu and Se by chemical method

High pure tellurium was prepared from raw tellurium containing copper and selenium by chemical method containing oxidation with concentrated nitric acid, leaching with hydrochloric acid, reducing with sulfur dioxide and treating in hydrogen atmosphere at high temperature. Removal ratio of Cu in raw tellurium reaches 99% after raw tellurium is oxidized and leached with HNO3（69%） under the following conditions： 0.96 times stoichiometric quantity of concentrated nitric acid, 4：1 of ratio of liquid to solid, 20 °C of reaction temperature and 30 min of reaction time. Leaching ratio of Te reaches 99% after Te is leached with hydrochloric acid under the following conditions： 1.67 times stoichiometric quantity of hydrochloric acid, 4：1 of ratio of liquid to solid, 20 °C of reaction temperature and 30 min of reaction time. Tellurium powder（99.95%） is obtained when Te（IV） in leachate is reduced with sulfur dioxide. The purity of tellurium increases from 99.954% to 99.999 6% after tellurium（99.95%） is treated in hydrogen atmosphere at 723.15 K for 30 min.

Selenium-catalyzed oxidative carbonylation of 2-aminobenzyl alcohol to give 1,4-dihydro-2H-3,1-benzoxazin-2-one

An efficient,economical,and phosgene-free approach was developed for the preparation of l,4-dihydro-2H-3,l-benzoxazin-2-one from 2-aminobenzyl alcohol.In terms of its key features,this reaction uses the cheap and recyclable non-metal selenium as a catalyst instead of the noble metal palladium;carbon monoxide as a carbonylation agent instead of virulent phosgene or one of its derivatives;and oxygen as an oxidant.The selenium-catalyzed oxidative carbonylation reaction of2-aminobenzyl alcohol proceeded efficiently in a single pot in the presence of triethylamine to afford l,4-dihydro-2H-3,l-benzoxazin-2-one in 87%yield.Furthermore,the selenium catalyst was readily recovered and recycled,affording a product yield of 80%after five cycles.

Selenium(Ⅵ) removal from caustic solution by synthetic Ca-Al-Cl layered double hydroxides

To extract selenium(Ⅵ)from the highly caustic leachate of copper anode slime,the Ca-Al-Cl layered double hydroxides(Ca-Al-Cl-LDHs)with a formula of Ca2 Al(OH)6 Cl·2 H2 O by three co-precipitation methods were synthesized.A plate-like morphology and hexagonal crystal structure with typical mineral phases and functional groups were identified by the FESEM,XRD,FTIR,BET and XPS analysis.The forward feeding sample exhibits the best adsorption capacity of Se(Ⅵ).The factor experiments then reveal a favorable adsorption process with low temperature,low NaOH concentration and high adsorbent dosage.Furthermore,the adsorption kinetics and isotherm parameters can be well described by the Langmuir isotherm and the pseudo-second-order models,respectively.Accordingly,the maximum adsorption amount of Se(Ⅵ)onto Ca-Al-Cl-LDHs reaches188.6 mg/g at 50 ℃.

Metal selenides for photocatalytic Z-scheme pure water splitting mediated by reduced graphene oxide

Exploration of novel narrow bandgap semiconductors for overall water splitting is vital for the realization of practical solar H2 production. In the work, solid solutions of zinc selenide and copper gallium selenide with absorption edge wavelengths ranging from 480 to 730 nm were developed. Using these metal selenides as H2-evolving photocatalysts, CoOx/BiVO4 as the O2-evolving photocatalyst, and reduced graphene oxide as the electron mediator, all-solid-state Z-scheme overall pure water splitting systems were constructed. The rate of photocatalytic H2 evolution from aqueous solutions containing Na2S and Na2SO3 as the electron donors was evaluated while employing these selenide photocatalysts at various Zn/(Zn+Cu) and Ga/Cu molar ratios. The data demonstrate that efficient Z-scheme overall water splitting was significantly correlated to the photoelectrochemical performance of the selenide photocatalysts acting as photocathodes, rather than the photocatalytic activities of these materials during the sacrificial H2 evolution.

Novel core‐shell Ag@AgSe_(x)nanoparticle co‐catalyst:In situ surface selenization for efficient photocatalytic H_(2)production of TiO_(2)

Effective charge separation and rapid interfacial H_(2) production are imperative for the construction of efficient photocatalysts.Compared to Pt,the metallic Ag co‐catalyst with its strong electron‐trapping ability and excellent electronic conductivity typically exhibits an extremely limited photocatalytic H_(2-)evolution rate owing to its sluggish interfacial H_(2)‐generation reaction.In this study,amorphous AgSe_(x) was incorporated in situ onto metallic Ag as a novel and excellent H_(2)‐evolution active site to boost the interfacial H_(2)‐generation rate of Ag nanoparticles in a TiO_(2)/Ag system.Core‐shell Ag@AgSe_(x)nanoparticle‐modified TiO_(2)photocatalysts were prepared via a two‐step pathway involving the photodeposition of metallic Ag and the selective surface selenization of metallic Ag to yield amorphous AgSe_(x)shells.The as‐prepared TiO_(2)/Ag@AgSe_(x)(20μL)photocatalyst exhibited an excellent H_(2‐)production performance of 853.0μmol h^(-1)g^(-1),prominently outperforming the TiO_(2)and TiO_(2)/Ag samples by factors of 11.6 and 2.4,respectively.Experimental investigations and DFT calculations revealed that the enhanced H_(2‐)generation activity of the TiO_(2)/Ag@AgSe_(x)photocatalyst could be accounted by synergistic interactions of the Ag@AgSe_(x)co‐catalyst.Essentially,the metallic Ag core could quickly capture and transport the photoinduced electrons from TiO_(2)to the amorphous AgSe_(x)shell,whereas the amorphous AgSe_(x)shell provided large active sites for boosting the interfacial H_(2)evolution.This study offers a facile route for the construction of novel core‐shell co‐catalysts for sustainable H_(2)evolution.

Determination of Selenium in Marine Aquatic Products by Hydride Generation-atomic Fluorescence Spectrometry (HG-AFS)

A method for the analysis of selenium in marine aquatic products by HG-AFS has been investigated. The method is based on the reduction of inorganic selenium to volatile SeH2 which is bubbled out by carrier gas of pure argon, and then swept to Ar-H2 flame quarts atomizer to measure its fluorescence intensity. The hydride generation, transportation, atomization and some instrumental parameters were studied by a kind of orthogonal design. The optimum conditions selected are as follows： reactive acidity, 20% HC1; the amount of NaBH4, 4.9mL; gas flow of argon, 600mLmin^-1; atomizing temperature, 200 ℃ ; negative high voltage, - 300V; light current, 100 mA; integral time, 7s. The detection limit of the presented method is 0.072μgL^-1 for selenium. The calibration curve shows a satisfactory line inthe concentration range from 0.000 to 1.000μgL^-1 Se. The recovery is 95.8%-102.2%.

Microwave Digestion Sample Hydride Generation-Atomic Fluorescence Spectrometry Determines Trace Selenium of Mogroside

0.2000g mogroside sample is digested by 7.0ml nitric acid and 3.0ml hydrogen peroxide, and generated by coprecipitation enrichment hydride - atomic fluorescence spectrometry determines trace selenium in it. Under optimum experiment conditions, a standard curve was produced using selenium standard solution, the linear equation is Ise=2890.6c＋0.0012,compared wish the linear relaticnship is not by coprecipitation direct determination of standard series Ise=82.56c＋0.0018 Selenium detection sensitivity was increased by 35.01 times,the correlation coefficient of obtained linear regression equation is 0.9996, the detection limit is 0.0012~tg/L and the relative standard deviation is 0.76% （n=5）. Containing 0.1808pg.g-1 Se Luo Han Shen samples. Based on mogroside sample, add a certain of standard solution to do recovery experiment, the obtained recovery rate is in 95.8%-103.6% and the result is satisfactory.

Visible light-promoted, iodine-catalyzed selenoalkoxylation of olefins with diselenides and alcohols in the presence of hydrogen peroxide/air oxidant: an efficient access to α-alkoxyl selenides

Under iodine-catalyzed and visible light-irradiated aerobic conditions, selenoalkoxylation of olefins with diselenides and alcohols can be efficiently achieved to afford the useful α-alkoxyl selenides in the presence of only 0.5 equiv. of H_2O_2. Controlling the sub-stoichiometric H_2O_2 amount is crucial to avoid the non-selective over-oxidation of the diselenides that leads to the ineffective hyper-valent selenium compounds. Meanwhile, under visible light irradiation, the green, safe, and low-cost air can work as a supplemental mild oxidant in the reaction to ensure selective oxidation of the diselenides, full conversion of the reactants, and ultimately good yield of the products.