高氯酸溶液中激发态铀酰离子的发光衰减研究

本文以氮分子激光器为激发光源,研究了激发铀酰离子在高氯酸溶液中的发光衰减和时间分辨发光光谱.铀酰离子的发光衰减与铀浓度以及溶液的pH有关,当铀浓度Cu<10^-^3mol.dn^-^3时,溶液pH为1.5-4.0范围内,发光呈单一指数衰减;当Cu≥10^3^-mol.dm^-^3时,发现发光呈双指数衰减,即除了上述发光组份外,还观察到另一发光寿命较长的组份.用时间分辨方法测得的铀酰溶液的发光光谱表明,上述现象与激发态水合铀酰离子及其水解产物形成的发光体有关.     

铀酰离子发光双指数衰减的研究

本文系统地研究了铀酰离子发光双指数衰减时的时间分辨发光光谱, 测定和研究了相应条件下铀(Ⅵ)的激光拉曼光谱. 通过计算机对所得光谱进行定量的拟合分解表明, 铀(Ⅵ)的发光双指数衰减是两种发光体UO_2~(2+)和它的水解产物(UO_2)_2(OH)_2~(2+)发光叠加的结果。     

铀酰离子发光双指数衰减的研究

本文系统地研究了铀酰离子发光双指数衰减时的时间分辨发光光谱,测定和研究了相应条件下铀(Ⅵ)的激光拉曼光谱.通过计算机对所得光谱进行定量的拟合分解表明,铀(Ⅵ)的发光双指数衰减是两种发光体UO_2~(2+)和它的水解产物(UO_2)_2(OH)_2~(2+)发光叠加的结果。     

一种偕胺肟基纤维材料对模拟盐湖水中铀的吸附研究

本文采用预辐射接枝法在7 L固液接枝反应釜中批量制备了偕胺肟(AO)基的超高分子量聚乙烯(UHMWPE-g-(PAO-co-PAA))纤维吸附材料,用红外光谱和扫描电子显微镜表征了材料的功能基团和表观形貌,研究了该材料在模拟盐湖水中对铀酰离子的吸附行为,并考察了溶液矿化度(TDS)、铀酰离子初始浓度等因素对材料吸附行为的影响.在TDS、溶液pH 8.1和铀酰初始浓度与西藏达则错盐湖相当的模拟盐湖体系中,AO含量为6.0 mmol g~(-1)的材料在28 d后对铀的吸附量高达8.29 mg g~(-1).铀酰离子的吸附量随TDS增加而有所降低,在TDS相当于海水10倍的pH 8.1模拟盐湖水中,铀的吸附量仍然达到6.63 mg g~(-1).材料对铀酰离子的吸附量随其初始浓度的增加而增大,在pH 8.1的模拟盐湖水中当铀浓度由187增加到1639μg L~(-1),其吸附量由4.54增加到17.48 mg g~(-1).结果表明,UHMWPE-g-(PAO-co-PAA)纤维材料在盐湖体系铀的提取中具有很好的应用前景.     

CMPO-离子液体萃取分离铀(Ⅵ)体系的电化学性质

研究了辛基(苯基)-N,N-二异丁基胺甲酰基甲基氧化膦(CMPO)-离子液体(IL)从硝酸铀酰水溶液中萃取铀(Ⅵ)的电化学行为,离子液体(IL)为1-丁基-3-甲基咪唑双三氟甲基磺酰亚胺盐(C4mimNTf2).用等摩尔系列法测得萃取过程中CMPO与U(Ⅵ)形成摩尔比为3∶1的配合物.用循环伏安法研究了萃取液中U(Ⅵ)-CMPO配合物的电化学性质,结果表明,在C4mimNTf2中U(Ⅵ)-CMPO配合物经过准可逆还原生成U(Ⅴ)-CMPO配合物,U(Ⅵ)/U(Ⅴ)电对的表观氧化还原电势(E(-),vs Fc/Fc+)为(-0.885±0.008)V.对萃取液进行控制电位电解,发现在铂片上有沉淀析出.X射线光电子能谱(XPS)测试结果表明,沉积物中只含有U(Ⅵ)、U(Ⅳ)和氧,而CMPO和C4mimNTf2没有被夹带析出.     

空间分辨测量解析三(2,2'-联吡啶)钌(Ⅱ)电化学发光机理的研究进展

电化学发光(ECL)是由电化学反应引发,通过一系列化学反应产生激发态发光体进而辐射发光的过程,其产生的方式主要有湮灭型电化学发光和共反应剂型电化学发光.ECL是一种表面限域的发光过程,其发光层的厚度主要由反应中间体在电极表面的分布决定.空间分辨测量能够直接测得激发态发光体、共反应剂自由基等中间体在电极表面附近的分布,进...     

烷基膦酸功能型离子液体合成、表征及对铀(Ⅵ)的萃取性能

以咪唑和吡啶作为阳离子基体,设计合成了3种具有烷基膦酸功能基团的功能型离子液体,利用傅里叶变换红外(FTIR)光谱、核磁共振氢谱(1H NMR)和元素分析对离子液体的结构进行了确认,测定了离子液体的相转变温度、热稳定性、密度和黏度等物理性能,并对硝酸介质中萃取铀酰离子进行了研究.结果表明,所制备的功能离子液体可同时作为稀释剂和萃取剂,在室温环境下实现对铀(Ⅵ)的萃取,萃取率可达到90%以上.     

改性凹凸棒土对Mo(Ⅵ)的吸附性能研究

研究了改性凹凸棒土吸附Mo(Ⅵ)的性能和机理,探讨了Mo(Ⅵ)溶液的起始浓度、pH值、吸附时间以及温度对此吸附剂吸附Mo(Ⅵ)性能的影响,得出了适宜的吸附条件.用红外对适宜条件下的吸附产物进行了表征.结果表明:改性凹凸棒土吸附Mo(Ⅵ)的适宜条件为:Mo(Ⅵ)溶液初始浓度1.86 mg·L-1,pH值2.20,时间20 min,温度35 ℃.改性凹凸棒土与MoO42-离子间通过静电作用(化学吸附)以及物理吸附相结合.     

生物吸附剂菹草干粉对Cr(Ⅵ)的吸附性能

开发了高效去除重金属Cr(Ⅵ)污染的生物吸附剂,菹草(Potamogeton crispus)干粉吸附剂,通过单因素分析考察了吸附时间、吸附剂颗粒大小、溶液初始pH值、吸附剂用量、Cr(Ⅵ)初始浓度以及离子强度等对重金属离子Cr(Ⅵ)的吸附性能。 结果表明,对吸附效果影响显著的因素有Cr(Ⅵ)初始浓度、吸附剂颗粒大小、溶液初始pH值和离子强度;其吸附行为符合准二级动力学方程,相关系数为0.9998;菹草对Cr(Ⅵ)的吸附等温线符合Langmuir方程。     

BaFCl：Sm晶体的光激励发光和热释发光

研究了在X射线辐照及光激励发光和热释发光过程中,BaFCl:Sm晶体中钐离子的价态变化和F色心的产生和湮灭过程。提出了如下的BaFCl:sm晶体的光激励发光和热释发光过程:在X射线辐照下,晶体中产生F色心,同时一部分Sm~(3 )俘获空穴形成Sm~(4 ),还有少量的Sm~(3 )得到电子形成Sm~(2 )。在光激励发光和热释发光过程中,从F色心中电离出来的电子与Sm~(4 )复合转变成Sm~(3 )激发态,随后发出Sm~(3 )的特征光辐射。同时在热释发光中,Sm~(2 )还可以与空穴复合,转变成Sm~(3 )的激发态,也发出Sm~(3 )的光辐射。     

配位体SO2-4对激发态铀(VI)去活化的影响

The dependence of the luminescence decay of electronically excited uranyl ions on the concentrations of uranium and sulphate in aqueous solution has been investigated with a pulsed nitrogen laser as a light source and a programmable transient recorder for lifetime measurements. Single exponential decay of the Luminescence is observed. The deactivation process of the excited uranyl ions should include radiative, nonradiative, water quenching and uranium self quenching and the measured lumine-scenec lifetime inidcates the result of all these processes. The Luminescence lifetime of uranyl ions increases with increasing concentration of sulphate and becomes constant when the equilibrium concentration of sulphate reaches 3.0 mol·L~(-1). The dependence of the Luminesence lifetime is similar to that of the UO_2(SO_4)_3~(4-) formation. This phenomenon can be interpreted in terms of the fact that in aqueous solution uranyl ions exist as aquo-uranyl ions. As the concentration of sulphte increaes the water molecule of hydrated uranyl ions will be replaced by sulphate ions via complex formation, and the quenching of excited uranyl ions by water is reduced. The self quenccing and the water quenching rate constants of UO_2(H_2O)_6~(2+) and UO_2(SO_4)_3~(4-) are estimated. Based on the experimental results a model for the deactivation mechanism of excited uranyl ions in sulphate solution is proposed.     

STUDY OF LUMINESCENT FORMS OF THE URANYL ION

Luminescence spectra and luminescence decay kinetics of uranyl sulphate water and uranyl nitrate acetone solutions of different concentrations have been studied. Similar experiments have been done with uranyl sulphate powder under vacuum. It has been experimentally shown that the hydrolysis of uranyl sulphate in water takes place, and under low salt concentrations (0.1-4.0 times 10^-4 M) a luminescence of a basic form of the photoexcited ion with a tentative structure of UO₂OH⁺* has been observed. The luminescence of the acidic form UO⁺* has been observed under higher salt concentrations (1–4 times 10^-2 M) in water and under any salt concentration in acetone. The acidic form has the characteristic emission spectrum possessing vibrational structure. The luminescence concentrational quenching of both photoexcited uranyl forms and exciplex emission have not been observed. The effect of a number of organic quenchers and molecular oxygen on uranyl luminescence has been studied. There is no luminescence quenching by O₂ up to 2 times 10⁶ Pa (20 atm) pressure. The low effectiveness of energy transfer from the photoexcited uranyl forms has been explained in terms of strong steric screening of 5f-uranium (VI) orbital by oxygen atoms and by external filled up uranium electronic shells.     

Luminescent kinetic determination of uranium mass fraction in plutonium

Measurement of lifetime along with measurement of intensity allow to determine both uranium and plutonium concentrations. If exciting light absorption is taken into account and temperature correction is introduced the intensity of uranyl limunescence extrapolated to zero time is a function of uranium and the ratior ₀/r-a function of plutonium concentration. Stadi of characteristics of uranyl luminescence was performed using a spectrometer interfased with a microcomputer. Luminescence was excited by nitrogen laser.     

Photochemical reduction of uranyl ion with ditertiary phosphines in dry acetone

Time-resolved transient absorption spectra have been observed using monochromatic light (=347.1 nm) from a 25 ns pulsed ruby laser. Collision between optically excited uranyl ion and ditertiary phosphines lead to photochemical reduction of uranyl ion to uranium(V) in non-aqueous medium. Stern-Volmer constants measured from lifetime measurement and quantum yields for uranium(V) formation reveal that electron transfer phenomenon competes with photophysical deactivation because of the presence of phenyl groups. Since ditertiary phosphines have two electron donating phosphorus atoms, are better reductant than monodentate phosphines in non aqueous medium.     

Probing the local coordination environment and nuclearity of uranyl(VI) complexes in non-aqueous media by emission spectroscopy

We describe the synthesis, solid state and solution properties of two families of uranyl(VI) complexes that are ligated by neutral monodentate and anionic bidentate P=O, P=NH and As=O ligands bearing pendent phenyl chromophores. The uranyl(VI) ions in these complexes possess long-lived photoluminescent LMCT (3)Π(u) excited states, which can be exploited as a sensitive probe of electronic structure, bonding and aggregation behaviour in non-aqueous media. For a family of well defined complexes of given symmetry in trans-[UO(2)Cl(2)(L(2))] (L = Ph(3)PO (1), Ph(3)AsO (2) and Ph(3)PNH (3)), the emission spectral profiles in CH(2)Cl(2) are indicative of the strength of the donor atoms bound in the equatorial plane and the uranyl bond strength; the uranyl LMCT emission maxima are shifted to lower energy as the donor strength of L increases. The luminescence lifetimes in fluid solution mirror these observations (0.87-3.46 μs) and are particularly sensitive to vibrational and bimolecular deactivation. In a family of structurally well defined complexes of the related anion, tetraphenylimidodiphosphinate (TPIP), monometallic complexes, [UO(2)(TPIP)(thf)] (4), [UO(2)(TPIP)(Cy(3)PO)] 5), a bimetallic complex [UO(2)(TPIP)(2)](2) (6) and a previously known trimetallic complex, [UO(2)(TPIP)(2)](3) (7) can be isolated by variation of the synthetic procedure. Complex 7 differs from 6 as the central uranyl ion in 7 is orthogonally connected to the two peripheral ones via uranyl → uranium dative bonds. Each of these oligomers exhibits a characteristic optical fingerprint, where the emission maxima, the spectral shape and temporal decay profiles are unique for each structural form. Notably, excited state intermetallic quenching in the trimetallic complex 7 considerably reduces the luminescence lifetime with respect to the monometallic counterpart 5 (from 2.00 μs to 1.04 μs). This study demonstrates that time resolved and multi-parametric luminescence can be of value in ascertaining solution and structural forms of discrete uranyl(VI) complexes in non-aqueous solution.     

QUENCHING OF THE FLUORESCENCE OF 8-METHOXYPSORALEN BY PROTONS

Abstract— The quenching of 8-methoxypsoralen (8-MOP) fluorescence by protons was observed to occur at the diffusion controlled rates in aqueous solutions at room temperature. Enhanced basicity of 8-MOP in the excited state compared to the ground state is expected on theoretical grounds. The fluorescence yield. which we determined as 6.3 × 10^--⁴ at pH 1 is surprisingly low and indicative of extremely fast radiationless decay pathways. The fluorescence lifetime of 8-MOP in neutral aqueous solution is on the order of 1–2 ns.     

GA-KBrO3-H2SO4体系化学振荡的研究

研究了GA(没食子酸)-KBrO_3-H_2SO_4体系的诱导期τ、振荡周期T_2与反应物起始浓度的依赖关系, 302 K时的经验式为τ=22.8 c~(-2.23)_(H_2SO_4) c~(-2.17)_(KBrO_3) c~(0.795)_(GA) (mol.dm~(-3))~(4.25)·sT_2=0.84 c~(-2.28)_(H_2SO-4)c~(-1.97)_(KBrO_3) exp{(0.000147(mol.dm~(-3))~2/c~2_(GA)}(mol.dm~(-3))~(4.25)·sτ及T_2都随~CGA的增加而增长, 这与B-Z反应中关于有机物的结论不同。用循环伏安法研究该体系的结果表明, GA在诱导期结束时就基本上都被氧化为中间物, GA并不象前人所认为的是维持振荡的物种, 实际参与振荡的是由GA生成的物质。本文还研究了Fe(Phen)_3~(2+)对GA-KBrO_3-H_2SO_4体系振荡的影响, 发现Br~-振荡行为随Fe(Phen)_3~(2+)的浓度而变。低~CFe(phen)_3~(2+)时,Br~-的振荡行为与GA-KBrO_3-H_2SO_4体系的基本相似, 其特征是每个振荡周期内, Br~-振荡脉冲发生前是逐渐积累的。随着~CFe(phen)_3~(2+)的增大, Br~-出现另一特征的振荡行为, 在每个振荡周期内, Br~-振荡脉冲发生前是逐渐减小。我们认为, GA-KBrO_3-H_2SO_4-Fe(Phen)_3~(2+)体系的振荡不能单一地用OKN机理加以解释, 它可能是两套振荡机理耦合的振荡。     

Photoluminescence of Uranium(VI): Quenching Mechanism and Role of Uranium(V)

The photoluminescence of uranium(VI) is observed typically in the wavelength range 400–650 nm with the lifetime of several hundreds μs and is known to be quenched in the presence of various halide ions (case A) or alcohols (case B). Here, we show by density functional theory (DFT) calculations that the quenching involves an intermediate triplet excited state that exhibits uranium(V) character. The DFT results are consistent with previous experimental findings suggesting the presence of photoexcited uranium(V) radical pair during the quenching process. In the ground state of uranyl(VI) halides, the ligand contributions to the highest occupied molecular orbitals increase with the atomic number (Z) of halide ion allowing larger ligand‐to‐metal charge transfer (LMCT) between uranium and the halide ion. Consequently, a larger quenching effect is expected as Z increases. The quenching mechanism is essentially the same in cases A and B, and is driven by an electron transfer from the quencher to the UO₂²⁺ entity. The relative energetic stabilities of the triplet excited state define the “fate” of uranium, so that in case A uranium(V) is oxidized back to uranium(VI), while in case B uranium remains as pentavalent.     

Na-β氧化铝/NaOH水溶液界面电势的测定

测定了Na-β氧化铝管在NaOH、NaOH-KOH、NaOH-(CH_3)_4NOH以及NaOH-NaCl四种溶液的浓差电池体系中的电动势, 求得Na-β氧化铝与NaOH水溶液之间的界面电势Δφ。结果表明: 在NaOH、NaOH-NaCl水溶液中, Δφ与loga_2(Na~+)/a_1(Na~+)之间的关系服从Nernst公式; K~+离子的存在影响Δφ值, 而OH~-、(CH_3)_4N~+贴无影响。探讨了用β氧化铝在高浓碱性Na~+水溶液中做Na~+离子选择性电极的可能性。