低温凝胶燃烧法合成Y2O3∶Er3+，Yb3+纳米晶上转换发光材料

分别以柠檬酸和甘氨酸为燃烧剂,采用低温凝胶燃烧法合成了Er³⁺、Yb³⁺共掺Y₂O₃纳米晶粉体。通过TG-DSC、XRD、SEM等分析手段对两种燃烧剂所对应的反应过程及纳米晶粉体的物理性能进行了分析,结果表明甘氨酸法具有更高的反应效率、更好的粉体分散性及粒径均匀性。在980 nm激光二极管(LD)激发下,对甘氨酸法所得样品的上转换发光性能分析表明,绿光和红光发射谱带分别来自于Er³⁺的⁴S_3/2/ ²H_11/2→ ⁴I_15/2和⁴F_9/2→ ⁴I_15/2跃迁。此外,对Er³⁺和Yb³⁺掺杂浓度、粉体煅烧温度对纳米晶样品上转换发光性能的影响进行了讨论。     

两种3D微孔Zn-MOF对水溶液中Fe3+、Cr2O72-和丙酮分子的荧光传感

通过溶剂热法合成了2种三维微孔锌金属有机框架材料,其分子式为[Zn₃(DBA)(OH)(1,10-phen)₂]_n(1)和{[Zn₂(HDBA)(4,4''-bipy)_1.5]·H₂O}_n(2)(H₅DBA=3,5-二(2'',4''-对羧基苯基)苯甲酸;1,10-phen=1,10-菲咯啉;4,4''-bipy=4,4''-联吡啶)。结构分析表明,配合物1为三核锌基金属单元的三维微孔骨架,配合物2为双核锌基的微孔结构。与2相比,配合物1在水中具有较强的发光性能,可作为检测Fe³⁺、Cr₂O₇^2-和丙酮分子的发光传感器,具有较高的选择性和灵敏度。     

两个3d-4f杂核配合物[Fe(phen)3]2[FeLn(H2O)(tiron)3]·6H2O的合成、晶体结构和磁性(Ln=HoⅢ, YbⅢ)

Ln₂O₃、硝酸铁、邻菲罗啉和钛铁试剂(tiron)通过水热法自组装合成了2个异质同晶的3d-4f杂核配合物[Fe(phen)₃]₂[FeLn(H₂O)(tiron)₃]·6H₂O, 其中, Ln=Ho^Ⅲ (1)和Yb^Ⅲ (2)。X-射线单晶衍射分析表明, 晶体属立方晶系, P2₁3空间群。3个tiron^4-配体利用酚氧桥联Ln³⁺和Fe³⁺形成具有C₃对称性的[FeLn(H₂O)(tiron)₃]^6-异双核配位单元, 其中七配位的Ln³⁺呈现一种畸变的单帽反三棱柱配位构型。配阳离子[Fe(phen)₃]³⁺通过phen-phen之间的π-π相互作用和与配阴离子间的静电引力等作用组装成三维的超分子。在2~300 K温度范围内测试了配合物的变温磁化率, 结果表明, Ln(Ⅲ)-Fe(Ⅲ)之间存在反铁磁性相互作用。     

四种同构镧系金属有机框架的合成、结构和荧光传感Fe3+和盐酸环丙沙星

采用溶剂热法,以含氮四羧酸3,5-二(3′,5′-二羧苯)-1H-1,2,4-三唑(H₄BDT)为配体,成功合成了4种同构镧系金属有机框架(Ln-MOFs)：{[La₃(BDT)₂(HCOO)(H₂O)₅]·0.5H₂O·3DMF}_n (1)、{[Ce₃(BDT)₂(HCOO)(H₂O)₅]·3DMF}_n (2)、{[Pr₃(BDT)₂(HCOO)(H₂O)₅]·3DMF}_n (3)和{[Nd₃(BDT)₂(HCOO)(H₂O)₅]·3DMF}_n (4),并采用单晶X射线衍射、粉末X射线衍射、元素分析、热重、红外、N₂吸附实验和荧光光谱对其进行表征。结果表明,这些Ln-MOFs均为单斜C2/m空间群晶体,是双核为无机建筑单元的三维介孔结构。其中2可选择性荧光检测Fe³⁺离子和盐酸环丙沙星药物分子,检测限分别为4.59和0.77 μmol·L^-1。     

一种用于检测罗红霉素和B4O72-的高稳定性Cd(Ⅱ)配位聚合物

在溶剂热条件下,成功合成了一种稳定的配位聚合物[Cd₂(L)(bpb)(H₂O)₄]·0.5H₄L (1)(H₄L=1,1''-乙烷基联苯-3,3'',5,5''-四羧酸,bpb=1,4-二(4-吡啶基)苯)。1在不同的有机溶剂和水中表现出优异的稳定性。1可通过荧光猝灭检测水中的罗红霉素(ROX)和B₄O₇^2-,检测限分别为0.21和1.59 μmol·L^-1。1可成功用于延河水中ROX和B₄O₇^2-的测定。此外,分析讨论了其传感机理。     

一种用于检测罗红霉素和B4O72-的高稳定性Cd(Ⅱ)配位聚合物

在溶剂热条件下,成功合成了一种稳定的配位聚合物[Cd₂(L)(bpb)(H₂O)₄]·0.5H₄L(1)(H₄L=1,1''-乙烷基联苯-3,3'',5,5''-四羧酸,bpb=1,4-二(4-吡啶基)苯)。1在不同的有机溶剂和水中表现出优异的稳定性。1可通过荧光猝灭检测水中的罗红霉素(ROX)和B₄O₇^2-,检测限分别为0.21和1.59μmol·L^-1。1可成功用于延河水中ROX和B₄O₇^2-的测定。此外,分析讨论了其传感机理。     

双帽Keggin型杂多阴离子[H4As3Mo12O40]-和Keggin型杂多酸H3PM12O40 (M＝Mo, W)质子化的DFT研究

选用B3LYP方法在LanL2MB水平下, 对双帽α-Keggin型杂多阴离子[H₄As₃Mo₁₂O₄₀]^-的电子结构和质子的定位进行了密度泛函理论(DFT)研究. 结果表明, 双帽的形成大大影响了杂多阴离子[As₃Mo₁₂O₄₀]^5－的电子结构和性质, NBO分析显示参与成帽的三桥氧上的电子密度比双桥氧上的要大, 简单地从电荷密度来看, 质子将首先在三桥氧上定域成键, 但通过比较质子定域在几种桥氧上质子化稳定化能的大小, 发现[H₄As₃Mo₁₂O₄₀]^-中的四个质子将在八个双桥氧中的其中四个氧原子上定位, 而不是如文献中报道的在四个三桥氧上定域成键. 对杂多酸H₃PM₁₂O₄₀ (M＝Mo, W)中质子的定位也进行了理论计算并与文献进行了比较, 结果显示, H₃PMo₁₂O₄₀中质子是定位在双桥氧上; 而H₃PW₁₂O₄₀中质子将优先在双桥氧上定位, 但也可在端氧上定位; 这一结果与文献报道的相一致.     

N2O活化的Fe/ZSM-5表面活性氧的表征(英)

Temperature-programmed reduction (H₂-TPR) was employed to quantitatively characterize the active oxygen species generated from a high Fe-loading Fe/ZSM-5 catalyst exposed to N₂O at 250 ℃. [Fe-O-Fe]²⁺ dimer was determined as the active iron complex for N₂O decomposition to produce the active oxygen. Reduction of Fe³⁺ to Fe²⁺ by H₂ in the dimer and removal of OH^- groups from Fe²⁺ dimer by heating Fe/ZSM-5 to 700 ℃ were the prerequisites for the formation of this active Fe complex. A linear correlation with a slope of 1.0 between the amount of [Fe-O-Fe]²⁺ and that of active oxygen species was observed. Maximum amount of active oxygen species can be generated by reducing Fe/ZSM-5 catalyst with H₂ at the temperatures over 500 ℃ and then heating the resulting product in Ar to 700 ℃, followed by N₂O exposure at 250 ℃. The ratio of the total number of oxygen atoms (Ode) deposited by interaction of [Fe-O-Fe]²⁺ with N₂O to the amount of [Fe-O-Fe]²⁺ was 2. However, not all the deposited oxygen atoms were active oxygen (O_a); the ratio of O_a and O_de was 0.5. The iron dimer complex composing active oxygen is a five-atom ion [Fe₂O₃]²⁺; the most probable structure is as follows:     

多级结构Mg3B2O6:Eu3+花状微球的制备、表征及其发光性能

以硝酸镁(Mg(NO₃)₂·6H₂O)和硼砂(Na₂B₄O₇·10H₂O)为原料,稀土元素Eu³⁺为激活剂,采用聚乙烯吡咯烷酮(PVP)辅助共沉淀法得到前驱体,并通过焙烧制备了多级结构Mg₃B₂O₆:Eu³⁺花状微球。通过XRD、SEM、TEM以及荧光光谱等手段分别对前驱体煅烧产物的结构、形貌、组成和荧光特性进行了表征。实验表明,在波长为393 nm激发光的激发下,所得到的产品在612 nm处有明显的特征发射峰,对应于Eu³⁺的(⁵D₀→⁷F₂)特征跃迁发射。这一荧光性质使得该材料在荧光灯、显示系统和光电设备应用中具有广阔的前景。同时我们还探讨了微球的形态、Eu³⁺的掺杂量及焙烧温度对花状微球荧光性能的影响。     

用于痕量监测Zr4+、Cr2O72-、Fe3+、HPO42-和指纹识别的功能化Eu3+/Tb3+配位聚合物荧光探针的构筑

采用芳香族π共轭及含氮原子有机连接剂,合成同构铽、铕发光配位聚合物(CPs){[Eu(PLIA)_1.5(H₂O)₂]·H₂O}_n (1)和{[Tb(PLIA)_1.5(H₂O)₂]·H₂O}_n (2),其中H₂PLIA=5-((吡啶-4-基甲基)氧基)苯-1,3-二甲酸。对合成的配合物进行了结构测定、表征和荧光痕量识别实验研究。2个同构配合物具有理想的三维框架结构,π…π堆积及氢键等弱相互作用增强了其化学稳定性;表征显示配位聚合物1和2具有良好的荧光性质、结晶性、热力学稳定性及结构完整性,可作为荧光传感的材料。1和2对水溶液中的Zr⁴⁺、Cr₂O₇^2-和Fe³⁺、HPO₄^2-具有选择性好、灵敏度高的荧光识别能力,其检出限分别为0.139 μmol·L^-1(1,Zr⁴⁺)、0.626 μmol·L^-1(1,Cr₂O₇^2-)、0.430 μmol·L^-1(2,Fe³⁺)、1.36 μmol·L^-1(2,HPO₄^2-)。探究了1和2作为探针的荧光猝灭机理。更有趣的是,1和2具有指纹识别性能,其荧光指纹纹路清晰连贯,细节明显,可被清晰观察。     

稀土掺杂Lu3Al5O12荧光粉的发光特性及能量传递

采用高温固相法制备了Ce、Sm共掺Lu₃Al₅O₁₂荧光粉。通过X射线衍射分析、荧光光谱分析研究了样品的结构、发光特性,并通过理论计算研究了能量传递效率、能量传递的临界距离以及能量传递方式。X射线衍射分析表明所制备的荧光粉具有单一的石榴石结构;荧光光谱分析表明,在464 nm蓝光激发下,Sm³⁺的引入可增加Lu₃Al₅O₁₂：Ce,Sm发射光谱中红光成分,并且随着Sm³⁺浓度的增加,Ce³⁺发光强度逐渐减弱。计算出Ce³⁺、Sm³⁺之间的能量传递效率高达77.42%,确定了Ce³⁺、Sm³⁺之间的能量传递机制为偶极-偶极相互作用。     

Comparison between electron-phonon coupling strengths of U and Nd ions doped in LaCl3 and U in LaBr3 single crystals

Temperature-dependent line width and line shift measurements between 7 and 280 K have been performed for a number of absorption transitions in the 4000-21,000 cm⁻¹ energy range of the U³⁺:LaCl₃, Nd³⁺:LaCl₃ and U³⁺:LaBr₃ single crystal spectra. The values of the electron-phonon coupling parameter were determined for U³⁺:LaCl₃ and Nd³⁺:LaCl₃ by a fit of experimentally observed line widths to an equation containing the temperature dependent broadening due to the Raman two-phonon process. For both ions diluted in LaCl₃ the values of the parameters are considerably lower than in K₂LaCl₅, and the value of for U³⁺ in the LaCl₃ host is markedly larger as compared with that of Nd³⁺. Factors influencing these differences are discussed. With a temperature increase a blue shift of the absorption lines of the U³⁺ ions in LaCl₃ and LaBr₃ is observed. A comparison has been performed among the electron-phonon coupling parameters obtained from an analysis of the line widths of the U³⁺:LaCl₃ single crystal and those determined from temperature induced line shifts as well as between the magnitudes of the absolute increase in line width and line shifts in the 7-290 K temperature range for U³⁺ doped LaCl₃ and LaBr₃ crystals. The electron-phonon coupling is stronger for U³⁺ in the tribromide as compared with the trichloride host which is mainly due to a larger covalency of the first one.     

稀土掺杂Lu3Al5O12荧光粉的发光特性及能量传递

采用高温固相法制备了Ce、Sm共掺Lu_3Al_5O_(12)荧光粉。通过X射线衍射分析、荧光光谱分析研究了样品的结构、发光特性,并通过理论计算研究了能量传递效率、能量传递的临界距离以及能量传递方式。X射线衍射分析表明所制备的荧光粉具有单一的石榴石结构;荧光光谱分析表明,在464 nm蓝光激发下,Sm~(3+)的引入可增加Lu_3Al_5O_(12)∶Ce,Sm发射光谱中红光成分,并且随着Sm~(3+)浓度的增加,Ce~(3+)发光强度逐渐减弱。计算出Ce~(3+)、Sm~(3+)之间的能量传递效率高达77.42%,确定了Ce~(3+)、Sm~(3+)之间的能量传递机制为偶极-偶极相互作用。     

Role of Acid-Base Equilibria in the Reduction of Selenious(IV) Acid

ABSTRACT

Electroanalytical methods have been widely used for determination of Se(IV), but the nature of the reduction processes involved is not well understood. Polarographic reduction occurs in three waves (i₁, i₂, and i₃) the height of which changes with pH. We proved that in wave i₁, H₃SeO₃ ⁺ is reduced, in i₂ H₂SeO₃, and in i₃ HSeO₃ ^-. SeO₃ ^2? is not reducible. All reductions involve a transfer of six electrons and yield selenides. Limiting currents are controlled by the rate of protonation. As proton donors, in addition to H₃O⁺, the acid forms of the buffer present also act. Limiting currents increase markedly with increasing concentration of the buffer. Tenfold increase in buffer concentration can result in up to 200% increase in limiting current.     

The dependence of persistent phosphorescence on annealing temperatures in CaTiO3:Pr nanoparticles prepared by a coprecipitation technique

Red emitting phosphors of CaTiO₃:Pr³⁺ nanoparticles with size ranging from 6 to 95 nm have been prepared by a coprecipitation technique and structurally characterized by X-ray diffraction, energy dispersive spectroscopy and scanning electron microscopy. The fluorescence and phosphorescence of CaTiO₃:Pr³⁺ nanoparticles as a function of annealing temperature are investigated. It is found that fluorescence intensities monotonously increase with increasing temperature. However, a maximum in phosphorescence with the increase of annealing temperature occurs for the sample prepared at 700 °C. Based on the measurement of fluorescence emission, fluorescence excitation and reflectance spectra as well as time decay patterns of fluorescence and phosphorescence, it is demonstrated that the dependence of fluorescence and phosphorescence on annealing temperature originates from the decrease of surface defects with the increase of temperature.     

Polyol-mediated solvothermal synthesis and luminescence properties of CeF3, and CeF3:Tb nanocrystals

CeF₃ and CeF₃:Tb³⁺ nanocrystals were successfully synthesized through a facile and effective polyol-mediated route with ethylene glycol (EG) as solvent. Various experimental techniques including X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and photoluminescence (PL) spectra as well as decay dynamics were used to characterize the samples. The results indicated that the content of NH₄F and reactant concentrations were key factors in the product shape and size. Excessive NH₄F was necessary for the formation of hexagonal nanoplates. The specific morphology of product can be controlled by changing the NH₄F content and reactant concentrations. In addition, Tb³⁺ doped-CeF₃ sample shows strong green emission centered at 544 nm corresponding to the ⁵D₄-⁷F₅ transition of Tb³⁺. Due to the decrease of nonradiative decay rate, the lifetime of ⁵D₄ level of Tb³⁺ become longer gradually upon increasing the size of product.     

SO42-改性后的TiO2(锐钛和/或金红石)表面上MoO3的分散性质研究

采用红外(IR)、拉曼(Raman)、X-射线衍射(XRD)、程序升温还原(TPR)等方法考察了经硫酸根改性后的金红石(SR)与锐钛矿(SA)的混合比例变化时的负载型催化剂，MoO₃ / TiO₂(SR+SA)，的一些物理化学性质(如活性组分MoO₃的分散行为、表面酸碱性、氧化还原性)的变化规律。结果表明：对于MoO₃ / TiO₂(SR+SA)样品，低含量MoO₃表面分散时倾向于优先与混合载体中的改性金红石(SR)发生作用；TiO₂载体表面SO₄^2-的存在，使得载体表面产生了新的酸性位，导致样品中表面分散的钼物种主要以聚合八面体状态存在。     

Synthesis and characterization of three new fluorovanadate complexes: N(C2H5)4[VOF4], N(CH3)4[VOF3Cl], N(C4H9)4[VOF3Br] and theoretical calculations of VOF4, VOF3Cl and VOF3Br ions

The reaction of VOF₃ with (C₂H₅)₄NF, (CH₃)₄NCl and (C₄H₉)₄NBr salts in anhydrous CH₃CN produced new complexes with the anion general formula [VOF₃X]⁻ in that (X = F⁻, Cl⁻, Br⁻). These were characterized by elemental analysis, IR, UV/Visible and ¹⁹F NMR spectroscopy. The optimized geometries and frequencies of the stationary point are calculated at the B3LYP/6-311G level of theory. Theoretical results showed that the VX (X = F, Cl, Br) bond length values for the [VOF₃X]⁻ in compounds 1-3 are 1.8247, 2.4031 and 2.5595 Å, respectively. Also, the VF₅ bond length values in [VOF₃X]⁻ are 1.824, 1.812 and 1.802 Å, respectively. These results reveal that the bond order for VX bonds decrease from compounds 1 to 3, while for VF₅ bonds, the bond orders increase. It can be concluded that the decrease of VX bonds lengths and the increase of VF₅ bond lengths in compounds 1-3 result from the increase of the hyperconjugation from compounds 1 to 3. Harmonic vibrational frequencies and infrared intensities for VOF₄⁻, VOF₃Cl⁻ and VOF₃Br⁻ are studied by means of theoretical and experimental methods. The calculated frequencies are in reasonable agreement with the experiment values. These data can be used in models of phosphoryl transfer enzymes because vanadate can often bind to phosphoryl transfer enzymes to form a trigonal-bipyramidal structure at the active site.     

Silver(I) ions-enhanced electrochemiluminescence of tris(2,2-bipyridyl)ruthenium(II)

In this paper, we demonstrate an electrochemiluminescence (ECL) enhancement of tris(2,2-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) by the addition of silver(I) ions. The maximum enhancement factor of about 5 was obtained on a glassy carbon electrode in the absence of co-reactant. The enhancement of ECL intensity was possibly attributed to the unique catalytic activity of Ag⁺ for reactions between Ru(bpy)₃³⁺ with OH. The higher enhancement was observed in phosphate buffer solutions compared with that from borate buffer solutions. This resulted from the fact that formation of nanoparticles with large surface area in the phosphate buffer solution exhibited high catalytic activity. The amount of Ag⁺, solution pH and working electrode materials played important roles for the ECL enhancement. We also studied the effects of Ag⁺ on Ru(bpy)₃²⁺/tripropylamine and Ru(bpy)₃²⁺/C₂O₄²⁻ ECL systems.     

CCl2(A 1B 1,a3B1)自由基被烷烃类分子猝灭动力学

用放电 LIF实验装置,对CCl4/Ar混合气体放电产生CCl2自由基,再用541.52 nm激光将电子基态CCl2激励到激发态A 1B1(0,4,0)振动能级上,通过检测激发态CCl2时间分辨荧光信号,测得室温下CCl2(A 1B1)被烷烃类分子猝灭的实验结果,用我们提出的三能级模型分析处理实验数据,获得CCl2(A 1B1)态和CCl2(a 3B1)态的碰撞猝灭速率常数kA和ka值.