硫化物的快速分光光度法测定

提出了测定微量硫化物的快速亚甲蓝分光光度法，实验结果表明，在硫酸溶液中，Ｋ２Ｃｒ２Ｏ７＋对二甲氨基苯胺＋Ｓ＾－２迅速显色反应形成亚甲蓝，表现摩尔吸收系数为４．０６×１０＾４Ｌ．ｍｏｌ＾－１．ｃｍ＾－１；最大吸收波长为６６４ｎｍ；线性范围为０～０．８ｍｇ／Ｌ，实验了采用全差示光度法直接测定水中硫化物的条件，用于某江水中２１．６μｇ／Ｌ硫化物测定时，相对标准偏差为３．２％（ｎ＝６）；试样的标准加入回收     

Eu^3＋,Bi^3＋Me2Y8（SiO4）6O2中的发光特性与取代格位

在紫外光激发下，Ｅｕ＾３＋和Ｂｉ＾３＋在Ｍｅ２Ｙ８（ＳｉＯ４）６Ｏ２基质（Ｍｅ＝Ｍｇ，Ｚｎ，Ｃａ，Ｓｒ）中分别发射红光（＾５Ｄ０－＾７Ｆ２）和蓝光（＾３Ｐ１－＾１Ｓ０）．Ｅｕ＾３＋发光的红橙比随着激发波长和Ｍｅ＾２＋的不同而变化。荧光拉曼光谱表明，Ｅｕ＾３＋在四种基质中同时占据了４ｆ格位和６ｈ格位。依据Ｂｉ＾３＋发光的Ｓｔｏｋｅｓ位移推断，当Ｍｅ＝Ｃａ，Ｚｎ时，Ｂｉ＾３＋主要占据４ｆ格位，而当Ｍｅ     

2,6—二氯—4—溴偶氮胂光度法测定微量铀（Ⅵ）

本报道用了２，６－二氯－４－溴偶氮胂作显色剂测定微量铀（Ⅵ）的光度法。在Ｈ２ＳＯ４介质中，铀（Ⅵ与）２，６－二氯－４－溴偶氮胂形成１：２络合物，其λｍａｘ＝６４０ｎｍ；表观摩尔吸光系数为１．１×１０＾５Ｌ．ｍｏｌ＾－＾１．ｃｍ＾－＾１；铀的浓度在０．０－２２．０μｇ／ｍｌ内符合比耳定律。方法具有灵敏度高，选择性好，操作方便等特点并已用于废水及矿样中微量铀（Ⅵ）的测定。     

一种基于形成杂多核络合物的荧光增敏效应的研究：Ⅲ.锰（Ⅱ）,钴（…

本研究了Ｍｎ＾２＋和Ｃｏ＾２＋对７－（８－羟基－３，６－二磺基萘偶氮）－８－羟基喹啉－５－磺酸－硼砂反应体系的混合荧光增敏作用。实验条件下，荧光增敏强度满足线性加和关系的范围是：Ｍｎ＾２＋浓度０￣２．９×１０＾－７ｍｏｌ／Ｌ；Ｃｏ＾２＋浓度０￣８．８～１０＾－７ｍｏｌ／Ｌ；总浓度不超过１．０×１０＾－６ｍｏｌ／Ｌ。检出限量为Ｍｎ＾２＋４．５×１０＾－９ｍｏｌ／Ｌ和Ｃｏ＾２＋１．４×１０＾－８ｍｏ     

Eu^2＋和Mn^2＋在Sr3MgSi2O8中的光致发光研究

研究了Ｅｕ＾２＋和Ｍｎ＾２＋共激活的Ｓｒ３ＭｇＳｉ２Ｏ８的荧光性质。Ｅｕ＾２＋和Ｍｎ＾２＋在４６０ｎｍ和６９０ｎｍ的发射峰分别由Ｅｕ＾２＋的５ｄ→４ｆ跃迁和Ｍｎ＾２＋的＾４Ｔ１（＾４Ｇ）→＾６Ａ１ｇ（＾６Ｓ）跃迁产生。未观察到单掺杂Ｍｎ＾２＋的Ｓｒ３ＭｇＳｉ２Ｏ８的荧光发射，而掺入Ｅｕ＾２＋后则出现了Ｍｎ＾２＋的６９０ｎｍ光致发光峰，表明Ｅｕ＾２＋对Ｍｎ＾２＋有敏化作用。Ｅｕ＾２＋的荧光寿命也受Ｍ     

硼掺杂多晶金刚石薄膜电极的电化学特性

用循环伏安法和恒电位法研究了硼掺杂多晶金刚石薄膜电极（ＤＦＥ）的若干电化学特性。电极面积４×４ｍｍ＾２。在０．１ｍｏｌ／Ｌ ＫＣｌ，ＮａＮＯ３，ＮａＯＨ和ＫＨ２ＰＯ４＋Ｎａ２ＨＰＯ４（ｐＨ＝６．８６）电解质溶液中电势窗口均为－５００￣＋８００ｍＶ；而在０．１ｍｏｌ／Ｌ ＨＣｌ和Ｈ２ＳＯ４溶液中电势窗口为－２００￣＋１１００ｍＶ．Ｋ３Ｆｅ（ＣＮ）６的氧化峰电位为＋５００ｍＶ，与Ｐｔ电极测量相同；校正     

不锈钢钝化膜在醛化液中自钝能力的研究

采用电偶极化和恒电位极化等电化学方法,评价１Ｃｒ１８Ｎｉ９Ｔｉ不锈钢阳极钝化膜和ＳＵＳ３６不锈钢原始钝化膜在７０℃的维尼维醛化液｛Ｈ２ＳＯ４（２４０ｇ／ｌ＋Ｎａ２ＳＯ４（７０ｇ／ｌ）＋ＨＣＨＯ（２５ｇ／ｌ）＋「Ｆｅ＾３＋」（３５．４＊１０＾－６）＋「Ｃｌ＾－」（２４０ｍｇ／ｌ）｝中的自钝能力,探讨醛化液组分、Ｆdisplay status     

酸性镀铜体系的交流阻抗研究

研究了基础溶液（０．３ｍｏｌ／ＬＣｕＳＯ４＋１．９４ｍｏｌ／ＬＨ２ＳＯ４）以及添加６０ｍｇ／ＬＣｌ＾－，３００ｍｇ／ＬＯＰ－２１，３０ｍｇ／ＬＰＥＧ－６０００，１０ｍｇ／Ｌ２－噻唑啉基－二硫丙烷酸钠（代号ＴＤＹ，自合成添加剂）后体系的阻抗行为，结果表明：１）Ｃｌ＾－在铜沉积中有增大阴极极化的作用；２）铜离子的放电为分步反应；即Ｃｕ＾２＋→Ｃｕ＾＋；Ｃｕ＾＋→Ｃｕ（吸附）→Ｃｕ（晶格），在含有Ｃｌ＾     

铜（Ⅱ）锌（Ⅱ）—氟哌酸体系电化学行为及示波极谱法研究

铜（Ⅱ）和锌（Ⅱ）分别在０．１ｍｏｌ／ＬＫＨ２ＰＯ４－Ｎａ２ＨＰＯ４缓冲溶液（ｐＨ６．５）和０．２５ｍｏｌ／ＬＮＨ４Ｃｌ溶液中，与氟哌酸形成良好的络合吸附波，峰电位分别为－０．２６Ｖ和－１．２８Ｖ（ｖｓ．ＳＣＥ），络合比分别为１：３和１：２，峰电流与铜（Ⅱ）和锌（Ⅱ）的浓度均在４．０×１０＾－７～５．０×１０＾－６ｎｏｌ／Ｌ范围内呈线性关系，检测限分别为７．０×１０＾－８和５．０×１０＾－８ｍｏｌ     

C4Om-4(m=0,1,2,3,4)的从头算研究 1.平衡几何和相对稳定性

在ＲＨＦ（基离子在ＵＨＦ和ＲＯＨＦ）／６－３１Ｇ,６－３１Ｇ和６－３１＋Ｇ水平优化得到Ｃ４Ｏ４＾ｍ－（ｍ＝０,１,２,３,４）的平衡几何构型,发现从中性分子（Ｃ４Ｏ４）到负４价离子（Ｃ４Ｏ４６４－）的经历了一个由非芳香性到芳香性再到反芳香性的结构变化过程,它们的相对稳定性为Ｃ４Ｏ４〉Ｃ４Ｏ４＾２－〉Ｃ４Ｏ４〉Ｃ４Ｏ４＾３－〉Ｃ４Ｏ４＾４－。     

Spectrophotometric determination of the oxygen to uranium ratio in uranium oxides based on dissolution in sulphuric acid

The oxygen to uranium ratio in uranium oxides such as U(3)O(8), UO(2+x) powders and UO(2) fuel pellets has been determined by a new spectrophotometric method. The method can be used for determination of O/U ratio in UO(2) pellets and powders on a routine basis. In the described method, uranium oxides in the powder form are dissolved in 2M sulphuric acid containing a few drops of HF. The concentrations of U(IV) and U(VI) are directly determined by means of the absorbances of these species at different wavelengths. For determination of the O/U ratio in U(3)O(8) powder samples, 630 and 310 nm are the wavelengths chosen for U(IV) and U(VI), respectively. For UO(2+x) powder, where the O/U ratio lies between 2.04 to 2.15, U(IV) and U(VI) are determined at 630 and 300 nm respectively, whereas for UO(2) fuel pellets, where the O/U ratio is less than 2.01, 535 and 285 nm are used. The molar absorptivity of U(IV) at 630 and 535 nm is 21.4 and 6.8 l.mole(-1).cm(-1) and that of U(VI) at 310, 300 and 285 nm is 178.1, 278.6 and 585 l.mole(-1).cm(-1), respectively. Standard deviations of +/-0.002 O/U ratio units for pellets and +/-0.004 O/U ratio units for powders have been achieved.     

Cs2USi6O15: a tetravalent uranium silicate

A uranium(IV) silicate has been synthesized under high-temperature, high-pressure hydrothermal conditions. The structure consists of unbranched dreier single layers with the composition [Si(2)O(5)] that are connected by UO(6) octahedra to form a 3D framework with 7-ring channels where the Cs(+) cations are located. Each UO(6) octahedron spans four neighboring dreier single chains and, therefore, introduces a high degree of corrugation in the silicate layers. The U 4f X-ray photoelectron spectroscopy spectrum was measured to confirm the valence state of the uranium. A comparison of related metal silicate structures is made. After the synthesis of this compound, all members in the family of uranium silicates and germanates with oxidation states of uranium from 4+ to 6+ have been observed.     

Aqueous coordination chemistry and photochemistry of uranyl(VI) oxalate revisited: a density functional theory study

Using density functional theory (DFT) calculations, we revisited a classical problem of uranyl(VI) oxalate photochemical decomposition. Photoreactivities of uranyl(VI) oxalate complexes are found to correlate largely with ligand-structural arrangements. Importantly, the intramolecular photochemical reaction is inhibited when oxalate is bound to uranium exclusively in chelate binding mode. Previously proposed mechanisms involving a UO(2)(C(2)O(4))(2)(2-) (1:2) complex as the main photoreactive species are thus unlikely to apply, because the two oxalic acids are bound to uranium in a chelating binding mode. Our DFT results suggest that the relevant photoreactive species are UO(2)(C(2)O(4))(3)(4-) (1:3) and (UO(2))(2)(C(2)O(4))(5)(6-) (2:5) complexes binding uranium in an unidentate fashion. These species go through decarboxylation upon excitation to the triplet state, which ensues the release of CO(2) and reduction of U(vi) to U(v). The calculations also suggest an alternative intermolecular pathway at low pH via an electron transfer between the excited state *UO(2)(2+) and hydrogen oxalate (HC(2)O(4)(-)) which eventually leads to the production of CO and OH(-) with no net reduction of U(VI). The calculated results are consistent with previous experimental findings that CO is only detected at low pH while U(IV) is detected only at high pH.     

Synthesis of a uranium(VI)-carbene: reductive formation of uranyl(V)-methanides, oxidative preparation of a [R2C═U═O]2+ analogue of the [O═U═O]2+ uranyl ion (R = Ph2PNSiMe3), and comparison of the nature of U(IV)═C, U(V)═C, and U(VI)═C double bonds

We report attempts to prepare uranyl(VI)- and uranium(VI) carbenes utilizing deprotonation and oxidation strategies. Treatment of the uranyl(VI)-methanide complex [(BIPMH)UO(2)Cl(THF)] [1, BIPMH = HC(PPh(2)NSiMe(3))(2)] with benzyl-sodium did not afford a uranyl(VI)-carbene via deprotonation. Instead, one-electron reduction and isolation of di- and trinuclear [UO(2)(BIPMH)(μ-Cl)UO(μ-O){BIPMH}] (2) and [UO(μ-O)(BIPMH)(μ(3)-Cl){UO(μ-O)(BIPMH)}(2)] (3), respectively, with concomitant elimination of dibenzyl, was observed. Complexes 2 and 3 represent the first examples of organometallic uranyl(V), and 3 is notable for exhibiting rare cation-cation interactions between uranyl(VI) and uranyl(V) groups. In contrast, two-electron oxidation of the uranium(IV)-carbene [(BIPM)UCl(3)Li(THF)(2)] (4) by 4-morpholine N-oxide afforded the first uranium(VI)-carbene [(BIPM)UOCl(2)] (6). Complex 6 exhibits a trans-CUO linkage that represents a [R(2)C═U═O](2+) analogue of the uranyl ion. Notably, treatment of 4 with other oxidants such as Me(3)NO, C(5)H(5)NO, and TEMPO afforded 1 as the only isolable product. Computational studies of 4, the uranium(V)-carbene [(BIPM)UCl(2)I] (5), and 6 reveal polarized covalent U═C double bonds in each case whose nature is significantly affected by the oxidation state of uranium. Natural Bond Order analyses indicate that upon oxidation from uranium(IV) to (V) to (VI) the uranium contribution to the U═C σ-bond can increase from ca. 18 to 32% and within this component the orbital composition is dominated by 5f character. For the corresponding U═C π-components, the uranium contribution increases from ca. 18 to 26% but then decreases to ca. 24% and is again dominated by 5f contributions. The calculations suggest that as a function of increasing oxidation state of uranium the radial contraction of the valence 5f and 6d orbitals of uranium may outweigh the increased polarizing power of uranium in 6 compared to 5.     

Cs4UGe8O20: a tetravalent uranium germanate containing four- and five-coordinate germanium

A very rare tetravalent uranium germanate has been synthesized under hydrothermal conditions at 585 °C and 160 MPa. Its structure contains layers of single-ring Ge(3)O(9)(6-) germanate anions that are connected by UO(6) octahedra and dimers of edge-sharing GeO(5) trigonal bipyramids to form a three-dimensional framework with intersecting 6- and 7-ring channels. UV-visible, photoluminescence, and U 4f X-ray photoelectron spectroscopy were used to confirm the valence state of uranium.     

Dissolution Extraction of Uranium Oxides and Cerium Oxide with TBP-HNO3 Complex in Supercritical CO2

Dissolution extraction of uranium oxides, CeO2 and (U, Ce)O2 solid solution with TBP-HNO3 complex in supercritical CO2 (SC-CO2) was investigated. It is difficult to dissolve and extract directly UO2 pellets and CeO2 with TBP-HNO3 complex in SC-CO2. After UO2 pellets spontaneously turns into U3O8 powders under O2 flow and 600 °C, the extraction efficiency can reach more than 98%. For dissolution extraction of (U, Ce)O2 solid solution with TBP-HNO3 complex in SC-CO2 under 60 and 20 MPa, the extraction efficiency of U and Ce is 98.61% and 98.1% respectively.     

Computational study of analogues of the uranyl ion containing the -N=U=N- unit: density functional theory calculations on UO2(2+), UON+, UN2, UO(NPH3)3+, U(NPH3)2(4+), [UCl4[NPR3]2] (R = H, Me), and [UOCl4[NP(C6H5)3]

The electronic and geometric structures of the title species have been studied computationally using quasi-relativistic gradient-corrected density functional theory. The valence molecular orbital ordering of UO2(2+) is found to be pi g < pi u < sigma g < sigma u (highest occupied orbital), in agreement with previous experimental conclusions. The significant energy gap between the sigma g and sigma u orbitals is traced to the "pushing from below" mechanism: a filled-filled interaction between the semi-core uranium 6p atomic orbitals and the sigma u valence level. The U-N bonding in UON+ and UN2 is significantly more covalent than the U-O bonding in UON+ and UO2(2+). UO(NPH3)3+ and U(NPH3)2(4+) are similar to UO2(2+), UON+, and UN2 in having two valence molecular orbitals of metal-ligand sigma character and two of pi character, although they have additional orbitals not present in the triatomic systems, and the U-N sigma levels are more stable than the U-N pi orbitals. The inversion of U-N sigma/pi orbital ordering is traced to significant N-P (and P-H) sigma character in the U-N sigma levels. The pushing from below mechanism is found to destabilize the U-N f sigma molecular orbital with respect to the U-N d sigma level in U(NPH3)2(4+). The uranium f atomic orbitals play a greater role in metal-ligand bonding in UO2(2+), UN2, and U(NPH3)2(4+) than do the d atomic orbitals, although, while the relative roles of the uranium d and f atomic orbitals are similar in UO2(2+) and U(NPH3)2(4+), the metal d atomic orbitals have a more important role in the bonding in UN2. The preferred UNP angle in [UCl4(NPR3)2] (R = H, Me) and [UOCl4(NP(C6H5)3)]- is found to be close to 180 degrees in all cases. This preference for linearity decreases in the order R = Ph > R = Me > R = H and is traced to steric effects which in all cases overcome an electronic preference for bending at the nitrogen atom. Comparison of the present iminato (UNPR3) calculations with previous extended Hückel work on d block imido (MNR) systems reveals that in all cases there is little or no preference for linearity over bending at the nitrogen when R is (a) only sigma-bound to the nitrogen and (b) sterically unhindered. The U/N bond order in iminato complexes is best described as 3.     

An optical spectroscopic study of borate glasses containing uranium ions

An optical spectroscopic investigation has been performed on some borate glasses containing 1mol % UF(4), UO(2) and UO(3). The optical data confirm the presence of uranium ions in valence stages of +6, +5 and +4. The influence of the composition of the glass matrix and of the gamma-irradiation on the redox equilibrium of uranium ions was discussed.     

N(CH2CH2NH3)3][U3O2F13].2H2O: a novel organically templated mixed-valent uranium oxyfluoride with a hybrid network structure

The synthesis and characterization of a novel mixed-valent uranium oxyfluoride is described; the inorganic network consists of 2-D [U(2)F(10)](2)(-) sheets constructed from corner- and edge-sharing U(IV)F(9) tricapped trigonal prisms and 1-D [UO(2)F(3)](-) chains constructed from edge-sharing U(VI)O(2)F(5) pentagonal bipyramids with the organic cations and water molecules between the sheets. This is the first example with a hybrid network structure in the system of uranium fluoride or oxyfluoride. The variable-temperature magnetic susceptibility confirms the oxidation state of the uranium ions. Crystal data follow: C(6)H(25)N(4)O(4)F(13)U(3), monoclinic, space group P2(1) (No. 4); a = 8.6876(4) A, b = 7.3158(4) A, c = 16.3376(8) A, beta = 93.7285(9) degrees , V = 1036.2(2) A(3), and Z = 2.     

Determination of the equilibrium formation constants of two U(VI)-peroxide complexes at alkaline pH

The formation of uranyl-peroxide complexes was studied at alkaline media by using UV-Visible spectrophotometry and the STAR code. Two different complexes were found at a H(2)O(2)/U(VI) ratio lower than 2. A graphical method was used in order to obtain the formation constants of such complexes and the STAR program was used to refine the formation constants values because of its capacity to treat multiwavelength absorbance data and refining equilibrium constants. The values obtained for the two complexes identified were: UO(2)(2+) + H(2)O(2) + 4OH(-) UO(2)(O(2))(OH)(2)(2-) + 2H(2)O: log β°(1,1,4) = 28.1 ± 0.1 (1). UO(2)(2+) + 2H(2)O(2) + 6OH(-) UO(2)(O(2))(2)(OH)(2)(4-) + 4H(2)O: log β°(1,2,6) = 36.8 ± 0.2 (2). At hydrogen peroxide concentrations higher than 10(-5) mol dm(-3), and in the absence of carbonate, the UO(2)(O(2))(2)(OH)(2)(4-) complex is predominant in solution, indicating the significant peroxide affinity of peroxide ions for uranium and the strong complexes of uranium(VI) with peroxide.