ZIF-8@Fe_3O_4磁性固相萃取结合高效液相色谱法测定果汁中3种苯甲酰脲杀虫剂

发展了磁性沸石咪唑酯骨架材料(ZIF-8@Fe_3O_4)磁性固相萃取结合高效液相色谱-二极管阵列检测器,测定果汁中氟幼脲、四螨嗪和氟啶脲3种苯甲酰脲杀虫剂(BUs)的新方法。利用X射线衍射仪、傅立叶变换红外光谱仪、扫描电子显微镜和振动样品磁强计对合成的ZIF-8@Fe_3O_4吸附剂进行表征,考察了溶液pH值、吸附剂用量、吸附时间、洗脱溶剂种类和体积(单次洗脱体积×洗脱次数)对BUs萃取效率的影响。在最优实验条件下,氟幼脲和四螨嗪在2.0～200 ng/mL、氟啶脲在3.5～350 ng/mL范围内线性关系良好(相关系数r=0.999),检出限(S/N=3)和定量下限(S/N=10)分别为0.6～1.0 ng/mL和2.0～3.5 ng/mL。3个加标水平下的回收率为82.7%～98.6%,日内和日间(n=3)相对标准偏差(RSD)分别为1.2%～6.1%和1.3%～9.0%。当上样体积为10 mL时,ZIF-8@Fe_3O_4对果汁中3种BUs的富集倍数为43.4～48.1倍,吸附剂重复使用10次后,3种BUs回收率的RSD不大于8.8%。该方法灵敏、高效,可用于果汁样品中BUs的分析。     

磁固相萃取结合高效液相色谱检测农田灌溉水中4种苯甲酰脲类农药

采用溶剂热法制备了磁性金属有机骨架吸附剂Fe_3O_4-NH_2@MIL-101,通过电子显微镜、红外光谱、X射线衍射对吸附剂的形貌和组成进行了表征,磁强计对吸附剂的磁强度进行了测定。使用该吸附剂进行磁固相萃取,结合高效液相色谱-紫外检测,对农田灌溉水中4种苯甲酰脲类杀虫剂(氯吡脲、氟幼脲、氟铃脲和虱螨脲)进行分析。实验对吸附和洗脱条件进行了优化,包括吸附剂用量、吸附时间、pH值、离子强度、洗脱溶剂种类以及洗脱时间和体积。在最佳实验条件下,方法能够有效富集灌溉水中的苯甲酰脲类杀虫剂。4种苯甲酰脲类杀虫剂在0. 010～3. 0 mg/L浓度范围内线性关系良好,相关系数(r)均大于0. 999 5,检出限为0. 03～0. 09μg/L,定量下限为0. 10～0. 30μg/L。方法的加标回收率为81. 7%～95. 4%,RSD小于10%。该方法前处理操作简便,萃取用时不超过15 min,可用于农田灌溉水中苯甲酰脲类杀虫剂的检测。     

4(3H)-嘧啶酮及其类似物互变异构的理论研究

采用密度泛函理论,在B3LYP/6-311G**基组水平上,计算并考察了4(3H)-嘧啶酮及其类似物(5-氟-4(3H)-嘧啶酮、4-巯基嘧啶和5-氟-4-巯基嘧啶)醇式结构和酮式结构进行结构互变质子迁移过程中的2种可能途径:(a)分子内质子迁移;(b)水助质子迁移.计算结果表明,途经b所需要的活化能较小.研究还表明,氢键在降低反应活化能方面起着重要的作用.     

高效广谱复合光催化抗菌剂Ag-AgVO3/BiVO4的设计合成及抗菌机制

合成了一种具有树叶状形貌的Ag-AgVO₃/BiVO₄复合光催化抗菌剂, 并对其晶体结构、 形貌、 组成及光学性质等进行了表征. 研究结果表明, 以3,3',5,5'-四甲基联苯胺(TMB)的氧化反应为模型, Ag-AgVO₃/BiVO₄表现出优异的光响应类氧化酶活性. 光催化抗菌实验结果表明, Ag-AgVO₃/BiVO₄对金黄色葡萄球菌和大肠杆菌均具有良好的抗菌效果, 4 min内的抗菌效率可以达到99%以上. 采用多种实验方法系统研究了其抗菌机制: 活性物种捕获剂实验和细胞内活性氧荧光标记实验表明, 在可见光照射下, Ag-AgVO₃/BiVO₄所产生的电子与O₂反应生成的·O₂^?起主要作用; Live/Dead细胞的荧光实验、 扫描电子显微镜形貌观察实验以及处理前后细胞内外核酸和蛋白质含量的测定实验结果均证实了·O₂^?可以破坏细胞膜的完整性, 导致细胞内容物的破坏和流出, 从而造成细菌死亡. 另外, Ag-AgVO₃/BiVO₄对包括革兰氏阳性菌、 革兰氏阴性菌和真菌在内的9种致病菌均具有良好的抗菌效果, 说明其具有广谱抗菌性能.     

可控粒径及一维链状纳米Fe3O4的制备

采用氧化共沉淀相转化法, 控制适当的pH(9～11.5)和反应温度(20～100 ℃), 制备了不同粒径(20.6～45.0 nm)的纳米Fe₃O₄, 同时对纳米Fe₃O₄一维成链的影响因素进行了分析. 研究发现: 磁场强度和溶液的pH值对纳米Fe₃O₄一维成链有影响, 磁场强度在低于75 mT, pH值在9～11.5时, Fe₃O₄呈现一维链状排列, 且成链趋势随pH值的减小而增强. 纳米Fe₃O₄粒子的链状结构是由外部磁场和其表面电荷的协同效应影响的. 纳米Fe₃O₄均呈现出铁磁性行为, 一维链状纳米Fe₃O₄具有相对较大的矫顽力和剩磁.     

非贵金属助催化剂Ni3N修饰g-C3N4用于可见光催化产氢的研究

近年来,利用太阳光光解水制氢被认为是解决当前能源短缺和环境污染问题的重要途径之一.众所周知,助催化剂可以有效的降低光催化产氢反应的活化能,提供产氢反应的活性位点,有效的促进催化剂中光生载流子的传输与分离,从而提高光催化剂产氢体系的反应活性和稳定性.然而,鉴于贵金属助催化剂(Pt, Au和Pd等)储量低、成本高,极大地制约了其应用.因而,开发出适用于光催化水分解制氢的非贵金属助催化剂尤为重要.石墨相氮化碳(g-C_3N_4)因其具有热稳定性、化学稳定性高以及制备成本低廉等优点,成为光催化领域研究的热点.然而,由于g-C_3N_4的禁带宽度(Eg=2.7 eV)较宽,致使其对可见光的响应能力较弱,并且在光催化反应过程中其光生电子-空穴对易复合,从而导致其光催化产氢活性较低.因此,如何开发出含非贵金属助催化剂的g-C_3N_4高效、稳定的太阳光催化分解水制氢体系引起了人们极大的关注.本文通过水热法-高温氨化法首次将非贵金属Ni_3N作为助催化剂来修饰g-C_3N_4,增强其可见光光催化性能(l420 nm).采用XRD、SEM、EDS、Mapping、UV-Vis、XPS和TEM等手段对Ni_3N/g-C_3N_4光催化体系进行了表征.结果表明, Ni_3N纳米颗粒成功的负载到g-C_3N_4表面且没有改变g-C_3N_4的层状结构.此外,采用荧光光谱分析(PL)、阻抗测试(EIS)和光电流谱进行表征,结果显示, Ni_3N纳米颗粒可有效促进催化剂中光生载流子的传输与分离,抑制电子-空穴对的复合.同时,将功率为300 W且装有紫外滤光片(λ420 nm)的氙灯作为可见光光源进行光催化产氢实验结果表明,引入了一定量的Ni_3N可以极大提高g-C_3N_4的光催化活性,其中, Ni_3N/g-C_3N_4#3的产氢量为～305.4μmol·h-1·g-1,大约是单体g-C_3N_4的3倍.此外,在450nm单色光照射下, Ni_3N/g-C_3N_4光催化产氢体系的量子效率能达到～0.45%,表明Ni_3N/g-C_3N_4具有将入射电子转化为氢气的能力.循环产氢实验表明, Ni_3N/g-C_3N_4在光催化产氢过程中有着较好的产氢活性和稳定性.最后,阐述了Ni_3N/g-C_3N_4体系的光催化产氢反应机理.本文采用的原料价格低廉,性能优异,制备简单,所制材料在光催化制氢领域展现出重要前景.     

梯型BiVO4/Ag3VO4光催化剂的构建及其可见光光催化性能

近年来,有机污染物的问题变得越来越严重.为了解决该问题,人们研究和开发了许多有效的光催化剂.本工作采用水热法和化学沉积法合成了BiVO4/Ag3VO4梯型半导体材料,该复合材料在可见光下具有很强的氧化还原能力.其中40%BiVO4/Ag3VO4具有最佳的光催化降解性能,其降解速率为0.05588 min^-1,分别是BiVO4和Ag3VO4的22.76和1.76倍.并且其性能稳定,经过四次循环后其降解率仍可保持90%以上.BiVO4和Ag3VO4复合后,其催化性能得到增强,归因于形成了新型的梯型光催化机制,该方法促进了光生电荷的分离并延长了电荷的寿命,且通过PL测试和瞬态光电流响应证明了电荷的有效转移.X射线衍射(XRD)可以观察到Ag3VO4和BiVO4物相,没有其他成分.用扫描电子显微镜(SEM)和透射电子显微镜(TEM)进一步观察了该催化剂的结构和形貌,从SEM可以看出,Ag3VO4生长在BiVO4的上面,能谱分析也证明该催化剂仅包含Ag3VO4和BiVO4的各种元素,而不含其他杂质,TEM进一步证明了两种物质复合在一起,而不是机械混合.通过紫外-可见光漫反射光谱(UV-vis)测试可以得到BiVO4和Ag3VO4的吸收带边,进一步计算BiVO4的带隙和导带分别为2.41和0.455 eV,Ag3VO4的带隙和导带分别为2.20和0.04 eV,二者组成的异质结的带隙满足降解的条件.用荧光光谱(PL)和光电流研究了样品的光电特征,结果表明BiVO4/Ag3VO4光催化剂具有很高的载流子分离效率和很低的光电流电阻,这有助于光生载流子的运输.光催化降解甲基蓝实验表明,BiVO4/Ag3VO4具有很强的光催化降解速率(0.05588 min^-1),是BiVO4的22.6倍,Ag3VO4的1.76倍,而且经过四次循环后仍能保持很高的活性.通过XRD发现使用后的催化剂并没有发生变化,说明该催化剂具有良好的稳定性.高分辨X射线光电子能谱(XPS)不仅进一步说明了该催化剂成功复合后没有其他杂质元素,而且从各元素的结合能变化可以看出构成异质结后电子的流向,证实了光催化机制为梯型机制.光照射后,BiVO4和Ag3VO4产生电子空穴对,当催化剂受光激发后,电子从价带被激发到导带,并在价带留下空穴.当BiVO4和Ag3VO4复合后,在接触界面形成内电场,由于库仑相互作用,能带边缘弯曲等作用加速了Ag3VO4价带上某些空穴和BiVO4导带上电子的复合,从而阻止了Ag3VO4和BiVO4内部电子空穴对的复合,这有助于Ag3VO4导带上的电子和BiVO4价带上的空穴参与氧化还原反应.从捕获实验可以看出,本实验中空穴在光催化降解中起着最重要的作用,这与上述结论一致.     

可见光响应的CO3(PO4)2/Ag3PO4纳米复合光催化剂的制备及表征

采用简单的化学偏聚法合成出Ag3PO4纳米颗粒、磷酸钴(Co3(PO4)2,CoP)纳米片以及它们两者的纳米复合结构(CoP/Ag3PO4),同时还比较了它们的可见光催化活性.采用场发射扫描电镜(FESEM)、X射线衍射(XRD)、紫外-可见(UV-Vis)吸收光谱以及光致发光谱等手段对其形貌、结构、光学以及可见光催化性能等进行表征.结果表明,CoP/Ag3PO4复合纳米结构的可见光降解甲基橙(MO)的速率和循环稳定性均明显优于其它两种物质.这表明CoP应该起着共催化剂的作用,它能够抑制光生电子与空穴之间的复合,并且提供大量高活性的光生空穴.此外,我们还发现CoP/Ag3PO4降解另一种阳离子型染料——罗丹明B(RhB)的能力则远不如纯Ag3PO4,这可能是与光催化剂的表面性质发生改变有关,造成更低的RhB吸附能力.本文提供了一种廉价制备高效可见光催化剂的新方法.     

可见光响应的Co3(PO4)2/Ag3PO4纳米复合光催化剂的制备及表征

采用简单的化学偏聚法合成出Ag3PO4纳米颗粒、磷酸钴(Co3(PO4)2,CoP)纳米片以及它们两者的纳米复合结构(CoP/Ag3PO4),同时还比较了它们的可见光催化活性.采用场发射扫描电镜(FESEM)、X射线衍射(XRD)、紫外-可见(UV-Vis)吸收光谱以及光致发光谱等手段对其形貌、结构、光学以及可见光催化性能等进行表征.结果表明,CoP/Ag3PO4复合纳米结构的可见光降解甲基橙(MO)的速率和循环稳定性均明显优于其它两种物质.这表明CoP应该起着共催化剂的作用,它能够抑制光生电子与空穴之间的复合,并且提供大量高活性的光生空穴.此外,我们还发现CoP/Ag3PO4降解另一种阳离子型染料——罗丹明B(RhB)的能力则远不如纯Ag3PO4,这可能是与光催化剂的表面性质发生改变有关,造成更低的RhB吸附能力.本文提供了一种廉价制备高效可见光催化剂的新方法.     

NH4VO3在NH4H2PO4-H2O和(NH4)3PO4-H2O体系中的溶解度

采用等温溶解法测定了偏钒酸铵(NH₄VO₃)在NH₄H₂PO₄-H₂O和(NH₄)₃PO₄-H₂O体系中T = 298.15-328.15 K时的溶解度以及溶液的密度和pH值。结果表明, NH₄VO₃的溶解度随着(NH₄)₃PO₄或NH₄H₂PO₄溶液浓度的增大,先降低后升高,这是由于同离子效应、化学反应平衡及离子活度的共同作用。比较T = 298.15K时, NH₄VO₃分别在NH₄H₂PO₄-H₂O、(NH₄)₂HPO₄-H₂O和(NH₄)₃PO₄-H₂O体系中溶解度,发现在相同的磷酸盐浓度下, NH₄VO₃的溶解度在NH₄H₂PO₄-H₂O体系中最大,在(NH₄)₃PO₄-H₂O体系中居中,在(NH₄)₂HPO₄-H₂O体系中最小。进一步地,在T = 298.15 K和磷酸盐浓度C = 0.5 mol·kg^-1时,结合pH值和反应溶度积常数K_SP等计算三个体系中的平均离子活度系数(γ_±),发现γ_±值在(NH₄)₂HPO₄-H₂O体系中最大,在(NH₄)₃PO₄-H₂O体系中居中,在NH₄H₂PO₄-H₂O体系中最小,与溶解度规律一致。     

PPh4[As3S3Cl4] und PPh4[As3S3Br4]

PPh₄[As₃S₃Cl₄] and PPh₄[As₃S₃Br₄] When As₂S₃ reacts with PPh₄X and HX in 1,2-C₂H₄X₂ (X = Cl, Br), the title compounds are obtained as minor products; the main products are PPh₄[As₂SX₅]. Their crystal structures were determined by X-ray diffraction. PPh₄[As₃S₃Cl₄]: a = 1187.7, b = 1090.9, c = 1191.8 pm, α = 82.91, β = 88,93, γ = 88.52°; twins with twin plane (100); R = 0.109 for 1618 observed reflexions of one twin crystal. PPh₄[As₃S₃Br₄]: a = 1119.7, b = 1177.5, c = 1204.1 pm, α = 81.59, β = 85.88, γ = 88.25°; R = 0.061 for 2331 observed reflexions. Both compounds crystallize in the space group P1 , Z = 2, and can be considered to be isotypic. Nevertheless, PPh₄[As₃S₃Br₄] does not form twins as PPh₄[As₃S₃Cl₄]. The crystals consist of PPh₄⁺ and [As₃S₃X₄]^? ions. In the anions, the three As atoms of an As₃S₃ ring in the chair conformation are commonly joined to an X atom and each As atom is bonded to one further terminal X atom. Cations and anions are packed in alternating layers.     

Synthese der isomeren 3, 4-Dimethyl-4-phenyl-3, 4-dihydro-carbostyrile

Cyclisation of 2-methyl-3-phenyl-but-3-en-anilide (III) with polyphosphoric acid gave cis-3, 4-dimethyl-4-phenyl-3, 4-dihydro-carbostyril (VII) in 61% yield together with a small amount of 2, 3-dimethylindenone (VIII), whereas with AlCl₃ a phenyl group was split off to give 3, 4-dimethylcarbostyril (VI). The anilide III isomerises to cis- and trans-2, 3-dimethyl-cinnam-anilide (IV resp. V) under basic conditions. The anilides IV and V gave only small yields of the dihydrocarbostyril VII with polyphosphoric acid. Chlorination of VII in position 3 using PCl₅ yielded IX which, on splitting out HCl, gave 3-methylene-4-methyl-4-phenyl-3, 4-dihydro-carbostyril (X). X was converted to trans-3, 4-dimethyl-4-phenyl-3, 4-dihydro-carbostyril (XI) by catalytic hydrogenation.     

Polythermal section Sn4P3-Sn4As3

The T-x diagram of the polythermal section Sn₄P₃-Sn₄As₃ of the Sn-P-As system was constructed using the results of X-ray powder diffraction and differential thermal analyses. A continuous series of solid solutions (Sn₄P₃) _x (Sn₄As₃)_{1 ? x} was found to exist. The section is not quasi-binary; in a Sn₄As₃-rich region, this section intersects the peritectic part of the three-phase volume (L + SnAs + α) of the ternary diagram.     

Konzentrationen von Isomeren des Typs P m As4−m X 3 in P4S3-As4S3- und P4Se3-As4Se3-Mischungen

The reactions of P₄S₃ with As₄S₃ and of P₄Se₃ with As₄Se₃ in the molten state yields molecules of the type P _m As_4–m S₃ and P _m As_4–m Se₃, respectively. A method was developed to separate the different components by the HPLC technique, and to determine their concentrations. The identification of the isomers in the HPLC pattern was achieved with the aid of the LC-MS method. In the selenium system, the distribution of the different species is statistical. In the system P₄S₃-As₄S₃, the formation of PAs₃S₃ with one phosphorus atom in the apical position is favoured.

     

Ternary early-transition-metal palladium pnictides Zr3Pd4P3, Hf3Pd4P3, HfPdSb, and Nb5Pd4P4

Several ternary palladium pnictides of the early transition metals have been prepared by arc-melting of the elemental metals and the binary pnictides ZrP, HfP, HfSb2, or NbP, and their structures have been determined by X-ray diffraction methods. The phosphides M3Pd4P3 (M = Zr, Hf) adopt a new structure type (Pearson symbol oP40), crystallizing in the orthorhombic space group Pnma with Z = 4 and unit cell parameters of a = 16.387(2), b = 3.8258(5), and c = 9.979(1) A for Zr3Pd4P3 and a = 16.340(2), b = 3.7867(3), and c = 9.954(1) A for Hf3Pd4P3. The antimonide HfPdSb was identified by powder X-ray diffraction (orthorhombic, Pnma, Z = 4, a = 6.754(1) A, b = 4.204(1) A, and c = 7.701(2) A) and confirmed to be isostructural to ZrPdSb, which adopts the TiNiSi-type structure. The phosphide Nb5Pd4P4 adopts the Nb5Cu4Si4-type structure, crystallizing in the tetragonal space group I4/m with Z = 2, a = 10.306(1) A, and c = 3.6372(5) A. Coordination geometries of pentacapped pentagonal prisms for the early transition metal, tetracapped distorted tetragonal prisms for Pd, and tricapped trigonal prisms for the pnicogen are found in the three structures; tetracapped tetragonal prisms for Nb are also found in Nb5-Pd4P4. In common with many metal-rich compounds whose metal-to-nonmetal ratio is equal or close to 2:1, the variety of structures formed by these ternary palladium pnictides arises from the differing connectivity of pnicogen-filled trigonal prisms. Pnicogen-pnicogen bonds are absent in these structures, but metal-metal bonds (in addition to metal-pnicogen bonds) are important interactions, as verified by extended Hückel band structure calculations on Zr3Pd4P3.     

Raman spectra of (NH4)3ZnCl4NO3 and (ND4)3ZnCl4NO3 between 295 and 60 K

Raman spectra from polycrystalline samples of (NH4)3ZnCl4NO3 and (ND4)3ZnCl4NO3 have been studied in the temperature range 60-295 K. Internal modes of both nitrate and tetrachlorozincate ions show expected band narrowing and intensification at lower temperature but no significant changes in frequency. Two bands in the lattice region of both compounds, assigned to nitrate ion libration and rocking, show linear increases in frequency with lowering temperature. The intensity of the libration mode shows a linear decrease with lowering temperature, but the intensity of the rocking mode is relatively insensitive to temperature change. Ammonium ion bands show greater structure at low temperature, suggesting differentiation between the two crystallographically distinct types of cation. The observed spectral changes are interpreted on the basis of increasing ordering and effectiveness of hydrogen bonds between ammonium ions and nitrate ions at low temperatures. The Raman spectra give no evidence of discontinuous changes in frequency or intensity, which would signal temperature-dependent transitions of the crystal structure. Unlike the related single-anion compounds NH4NO3 and (NH4)2ZnCl4, the room-temperature structure of (NH4)3ZnCl4NO3 and (ND4)3ZnCl4NO3 appears to persist at least to 60 K, being stabilized by increasingly ordered hydrogen bonding.     

Tetraphenylphosphonium-tetraiodotrithiotriarsenat,PPh4[As3S3I4]

Tetraphenylphosphonium tetraiodotrithiotriarsenate, PPh₄[As₃S₃I₄] PPh₄[As₃S₃I₄] is formed along with PPh₄I₃ and other unidentified compounds by the reaction of As₂S₃, PPh₄I and HI in CH₂I₂ at 80°C. PPh₄[As₃S₃I₄] was characterized by its IR spectrum and an X-ray crystal structure determination (3684 unique observed reflexions, R = 0.083). Crystal data: a = 1390.3, b = 1548.9, c = 1505.4 pm, β = 91.08°, monoclinic, P2₁/c, Z = 4. The crystals are not isotypic with the corresponding chloro and bromo compounds, although the anion constitutions are of the same type. The [As₃S₃I₄]^? ion consists of an As₃S₃ ring in the chair conformation, the three As atoms are commonly linked to a bridging I atom and each As atom is bonded to one terminal I atom. Cations and anions are packed in alternating layers.     

Die Kristallstruktur von Ce4As3 und Pr4As3

Ohne Zusammenfassung