Structure model and synthesis of NdCl3-FeCl3-graphite intercalation compounds

The distribution of the elements and microstructure of NdCI3-FeCI3-graphite intercalation compounds (GICs) were shown by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results show that Nd element intercalates into graphite, forming NdCI3-FeCI3-GICs, and the distribution of Nd and Fe is nearly even. On the basis of the data, a structure model for RECI3-GICs was founded, and the characteristic layer distance and the index of interval energy were calculated. The calculated results agree with experimental ones, and the relative errors are ±2%. Thus it can be seen that the (111) face is optimal direction for intercalation reaction of TbCl3-LuCl3, and the (001) face is that for LaCl3-GdCl3, because of the lowest interval energy.     

Spectral properties of Nd-doped BiB3O6 crystal

Transparent Nd: BiB₃O₆ crystal has been grown by top-seeded method. The refraction indices of the crystal were measured and the parameters of chromatic dispersion were fitted. The room temperature absorption spectra of the crystal have been measured and compared with that of 0.2 mol/L NdCl₃ solution. According to Judd-Ofelt (JO) theory, the spectral strength parameters Ω₂ = 0.1776×10⁻²⁰ cm², Ω₄ = 0.1282−10⁻²⁰1 cm² and Ω₆ = 0.1357X10^-20 cm² of Nd³⁺ ion were fitted. The radiative transition probabilities A_J,J’, oscillator strengths f_J,J’, radiative lifetime rand the branching ratio β_J’ have all been calculated. Based on these parameters, the properties and application perspective are discussed.     

Spectral study of the complexation of Nd(III) with glutathione reduced (GSH) in the presence and absence of Zn(II) in aquated organic solvents

Studies on the difference in energy parameters and comparative absorption spectrophotometry involving 4f-4f transitions on Nd(III) and glutathione reduced (GSH) in the absence and presence of Zn(II) have been carried out in aquated organic solvents (50 : 50) like methanol, dioxane, acetonitrile and dimethylformamide. Variations in the spectral energy parameters — Slater-Condon (F _k ) factor, Lande spin-orbit coupling constant (ξ4f), nephelauxetic ratio (β), bonding parameter (b ^1/2 ) and percent covalency (δ) — are calculated and correlated with binding of Nd(III) with GSH in presence and absence of Zn(II).     

Ca9Y(PO4)7:Ce3+,Tb3+纳米荧光粉的制备及发光性能

采用水热法制备出Ca_9Y(PO4)7∶Ce~(3+),Tb~(3+)纳米荧光粉,通过XRD、SEM和荧光光谱等对样品进行了分析,研究在Ca_9Y(PO4)7基质中引入Ce~(3+),Tb~(3+)离子对发光性能的影响规律。研究发现因Tb~(3+)离子自身能量交叉驰豫的存在,使得单掺Tb~(3+)时,通过调节Tb~(3+)离子的浓度可以实现对发光颜色的控制。同时研究了Ce~(3+)-Tb~(3+)之间的能量传递为电多极相互作用的偶极-四极机制,Ce~(3+)-Tb~(3+)之间最大的能量传递效率为55.6%。Ca_9Y(PO4)7∶Ce~(3+),Tb~(3+)的发光颜色可以通过激活离子之间的能量传递和共发射得到可控调节。SEM分析表明荧光粉颗粒尺寸在100 nm左右,分散性好。     

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。     

Determination of dissociation degrees of K3NbF8 and K3TaF8 by thermodynamic analysis of subsystems of the KF-K2NbF7 and KF-K2TaF7 systems

A special form of the LeChatelier-Shreder equation describing the equilibrium between the crystalline phase and the melt in system A-AB in which the substance AB partially dissociates upon melting was applied to systems KF-K₃NbF₈, K₂NbF₇-K₃NbF₈ and to KF-K₃TaF₈, K₂TaF₇-K₃TaF₈ subsystems of the binary systems KF-K₂NbF₇ and KF-K₂TaF₇ in which the additive compounds K₃NbF₈ and K₃TaF₈ are formed. Using the phase diagram of the system KF-K₂NbF₇ determined by McCawley and Barclay (1971) and the values of the fusion enthalpy of K₃NbF₈ taken from literature, the intervals of the dissociation degree values of K₃NbF₈ for both branches of the liquidus curve of K₃NbF₈ were calculated. The calculated values of the dissociation degree depend on the coordinates of the liquidus curve of K₃NbF₈ of the pertinent phase diagram, on its used branch and section, and on the value of the fusion enthalpy of K₃NbF₈. For the measured fusion enthalpy of K₃NbF₈ (57 kJ mol⁻¹), a common interval of the dissociation degree values of K₃NbF₈ for both branches of the liquidus curve of K₃NbF₈ is 0.71–0.72. Similarly, intervals of the dissociation degree values of K₃TaF₈ for both branches of the liquidus curve of K₃TaF₈ were calculated using the phase diagram of the system KF-K₂TaF₇ determined by Boča et al. (2007) and the measured fusion enthalpy of K₃TaF₈ ((52 ± 2) kJ mol⁻¹). The error of the determination of the fusion enthalpy of K₃TaF₈, the common interval of the dissociation degree values of K₃TaF₈ for both branches of the liquidus curve of K₃TaF₈ is 0.68–0.69.     

全反式维甲酸合铜(II)配合物对DNA的切割和键合作用

以荧光法、粘度法、凝胶电泳和电化学方法研究了全反式维甲酸合铜(II)配合物与DNA的作用. 结果表明, 该配合物能在生理条件下有效切割质粒DNA, 加入H₂O₂后发现该配合物的切割活性增强, 说明该配合物对DNA的切割机理可能有两种: 氧化和水解. 同时可使DNA的粘度增加, 使EB-DNA体系的荧光强度降低. DNA的存在能导致该配合物氧化还原峰电流降低. 据此推断, 该配合物主要以嵌入方式与DNA作用.     

颜色可调Sr3Y（BO3）3∶Tm3+，Dy3+荧光粉的发光性能及能量传递

采用高温固相法制备了Sr_3Y(BO_3)_3:xTm~(3+),yDy~(3+)荧光粉,并通过XRD、SEM和荧光光谱仪对样品的物相、微观形貌、发光性能、能量传递机制和CIE色坐标进行了分析。结果表明:Sr_3Y(BO_3)_3:xTm~(3+)荧光粉在监测波长为359 nm时发射蓝光,Tm~(3+)的浓度淬灭点为x=0.08;在Sr_3Y(BO_3)_3:0.08Tm~(3+),yDy~(3+)荧光粉中,随着Dy~(3+)掺杂浓度的增加,Tm~(3+)的发光强度降低而Dy~(3+)发光强度却先增加后降低,Dy~(3+)的浓度淬灭点为y=0.1;通过改变Dy~(3+)掺杂浓度或改变激发光的波长,均可实现发射光的颜色可调;在Tm~(3+)-Dy~(3+)离子之间存在能量传递。当Dy~(3+)掺杂浓度(物质的量分数)为0.15时能量传递效率达75.14%,能量传递机制为电偶极-电偶极相互作用。     

Chromium(III) Hydroxide Solubility in the Aqueous K+-H+-OH?-CO2-HCO 3? -CO 32? -H2O System: A?Thermodynamic Model

Chromium(III)-carbonate reactions are expected to be important in managing high-level radioactive wastes. Extensive studies on the solubility of amorphous Cr(III) hydroxide solid in a wide range of pH (3–13) at two different fixed partial pressures of CO₂(g) (0.003 or 0.03 atm.), and as functions of K₂CO₃ concentrations (0.01 to 5.8 mol⋅kg⁻¹) in the presence of 0.01 mol⋅dm⁻³ KOH and KHCO₃ concentrations (0.001 to 0.826 mol⋅kg⁻¹) at room temperature (22±2 °C) were carried out to obtain reliable thermodynamic data for important Cr(III)-carbonate reactions. A combination of techniques (XRD, XANES, EXAFS, UV-Vis-NIR spectroscopy, thermodynamic analyses of solubility data, and quantum mechanical calculations) was used to characterize the solid and aqueous species. The Pitzer ion-interaction approach was used to interpret the solubility data. Only two aqueous species [Cr(OH)(CO₃)₂²⁻ and Cr(OH)₄CO₃³⁻] are required to explain Cr(III)-carbonate reactions in a wide range of pH, CO₂(g) partial pressures, and bicarbonate and carbonate concentrations. Calculations based on density functional theory support the existence of these species. The log ₁₀ K° values of reactions involving these species [{Cr(OH)₃(am) + 2CO₂(g)⇌Cr(OH)(CO₃)₂²⁻+2H⁺} and {Cr(OH)₃(am) + OH⁻+CO₃²⁻ ⇌Cr(OH)₄CO₃³⁻}] were found to be −(19.07±0.41) and −(4.19±0.19), respectively. No other data on any Cr(III)-carbonato complexes are available for comparisons.     

Preparation and photoluminescence properties of RE:Na3La9O3(BO3)8 (RE=Er, Yb) crystals

Using Na₂CO₃-H₃BO₃-NaF as fluxes, transparent RE:Na₃La₉O₃(BO₃)₈ (abbr. RE:NLBO, RE=Er, Yb) crystals have been grown by the top seed solution growth (TSSG) method. The X-ray powder diffraction analysis shows that the RE:NLBO crystals have the same structure with NLBO. The element contents were determined by molar to be 0.64% Er³⁺ in Er:NLBO, 2.70% Yb³⁺ in Yb:NLBO, respectively. The polarized absorption spectra of RE:NLBO have been measured at room temperature and show that both Er:NLBO and Yb:NLBO have a strong absorption bands near 980 nm with wide FWHM (Full Wave at Half Maximum) (21 nm for Er:NLBO and 25 nm for Yb:NLBO). Fluorescence spectra have been recorded. Yb:NLBO has the emission peaks at 985 nm, 1028 nm and 1079 nm and the emission peak of Er:NLBO is at 1536 nm. Spectral parameters have been calculated by the Judd-Ofelt theory for Er:NLBO and the reciprocity method for Yb:NLBO, respectively. The calculated values show that Er:NLBO is a candidate of 1.55 μm laser crystals and Yb:NLBO is a candidate for self-frequency doubling crystal.     

Theoretical sstudy on the Co2+OH2+/Co3+OH2+ electron transfer reactivity

This paper presents a contact distance dependence analysis scheme and an abinitio calculation application for the electron transfer (ET) reactivity of Co²⁺OH₂/Co³⁺OH² reacting pair. The applicability of these schemes and the corresponding models has been discussed. The contact distance (R _CoCo) dependence of the relevant quantities has been analyzed. The results indicate that the activation energy from the accurate PES method agrees well with that from the anharmonic potential method, and they are obviously better than that from the harmonic potential method. The pair distribution function varies from 10⁻² to 10⁻⁵ along withR _CoCo changing from 1.20 to 0.35 nm. The coupling matrix element exponentially decays along with the increase ofR _CoCo, and the effective electronic coupling requiresR _CoCo smaller than 0.75 nm. In the range from 0.50 to 0.75 nm forR _CoCo, the corresponding electronic transmission coefficient falls within 1.0—10⁻⁶. The local ET rate also exponentially decays along with the increase ofR _CoCo due to the electronic factor. Since the contribution from the pair distribution function to the total ET rate is an inverse measure of that from the electronic factor, the variation of the spherically averaged local ET rate along withR _CoCo exhibits a parabola with a maximum at 0.50 nm ofR _CoCo. This maximum is close to the overall observed ET rate value. For this mono-hydrated transition metal ionic system, the ET rate generally is about 10⁶ L·mol⁻¹·s⁻¹ in gaseous process. Further, since it is impossible to experimentally determine the structures and their PESs of these hydrated systems, especially for the unstable intermediate species,ab initio calculations can play an effective auxiliary role in discussing the ET reactivities of these kinds of reacting systems.     

Photoacoustic spectra of Nd(TFA)3 · 2H2O and Nd(HFA)3 · 2H2O

A new synthesis of trisfluoroacetylactone (TFA) and hexafluoroacetylactone (HFA) Nd complexes: Nd(TFA)₃ · 2H₂O and Hd(HFA)₃ · 2H₂O is reported. The photoacoustic (PA) spectra in the 300–800 nm region of the compounds NdCl₃ · 6H₂O, Nd(TFA)₃ · 2H₂O and Nd(HFA)₃ · 2H₂O are reported. The PA absorption bands are assigned and their relative intensities represented by intensity branching vectors are calculated. The perturbation of the ligand on the energy levels of Nd³⁺ ion is discussed and a model of the relaxation process of Nd(HFA)₃ · 2H₂O is proposed based on its PA and absorption spectra.     

La_7O_6(BO_3)(PO_4)_2∶Eu~(3+)/Tb~(3+)荧光材料的制备及其光致发光性能

采用优化的高温固相方法制备了稀土离子Eu~(3+)和Tb~(3+)掺杂的La_7O_6(BO_3)(PO_4)_2系荧光材料,并对其物相行为、晶体结构、光致发光性能和热稳定性进行了详细研究。结果表明,La_7O_6(BO_3)(PO_4)_2∶Eu~(3+)材料在紫外光激发下能够发射出红光,发射光谱中最强发射峰位于616 nm处,为5D0→7F2特征能级跃迁,Eu~(3+)的最优掺杂浓度为0.08,对应的CIE坐标为(0.610 2,0.382 3);La_7O_6(BO_3)(PO_4)_2∶Tb~(3+)材料在紫外光激发下能够发射出绿光,发射光谱中最强发射峰位于544 nm处,对应Tb~(3+)的5D4→7F5能级跃迁,Tb~(3+)离子的最优掺杂浓度为0.15,对应的CIE坐标为(0.317 7,0.535 2)。此外,对2种材料的变温光谱分析发现Eu~(3+)和Tb~(3+)掺杂的La_7O_6(BO_3)(PO_4)_2荧光材料均具有良好的热稳定性。     

Direct dynamics studies for the reactions of CF3CHFCF3 and CF3CF2CHF2 with H atoms

The rate constants of the hydrogen abstraction reactions of CF₃CHFCF₃ + H (R1) and CF₃CF₂CHF₂ + H (R2) have been calculated by means of the dual-level direct dynamics method. Optimized geometries and frequencies of stationary points and extra points along the minimum-energy path (MEP) are obtained at the MPW1K/6-311+G(d,p) level, and the classical energetic information is further corrected with the interpolated single-point energy (ISPE) approach by the G3(MP2) level of theory. Using the canonical variational transition state theory (CVT) with small-curvature tunneling corrections (SCT), the rate constants are evaluated over a wide temperature range of 200-2000 K. The calculated CVT/SCT rate constants are in good agreement with available experimental values. It is found that the variational effect is very small and almost negligible over the whole temperature region. However, the small-curvature tunneling correction plays an important role in the lower temperature range. Furthermore, the heats of formation of species CF₃CF₂CHF₂ (SC₁ or SC₂) and CF₃CF₂CF₂ are studied using isodesmic reactions to further elucidate the thermodynamic properties.     

反式2-甲基-2-丁烯酸甲酯与臭氧反应机理的计算研究

采用G3B3方法构建反式2-甲基-2-丁烯酸甲酯与O3反应体系以及后续Criegee自由基有、无水分子参与下异构化反应的势能面剖面.结果表明,反式2-甲基-2-丁烯酸甲酯与O3反应首先生成一个稳定的五元环中间体,此中间体按断键位置不同后续裂解反应存在两条路径,分别生成产物P1(CH3CHOO+CH3OC(O)C(CH3)O)和P2(CH3CHO+CH3OC(O)C(CH3)OO).利用经典过渡态理论(TST)并结合Wigner矫正模型计算了200-1200 K温度区间内标题反应的速率常数kTST/W.计算结果显示,294 K时,该反应速率常数为7.55×10-18cm3molecule-1s-1,与Bernard等对类似反应所测实验值非常接近.生成的Criegee自由基(CH3CHOO和CH3OC(O)C(CH3)OO)可分别与水分子发生α-加成及β-氢迁移反应,其中Criegee自由基与水的α-加成反应较其与水的β-氢迁移反应具有优势.另外与无水分子参与CH3CHOO和CH3OC(O)C(CH3)OO异构化反应相比,水分子的参与使得异构化反应较为容易进行.     

Crystal and molecular structures of the Rh[(C2H5O)2PS2]3 and Co[(C6H5O)2PS2]3 chelate compounds

The crystal structures of the Rh[(EtO)₂PS₂]₃ (I) and Co[(PhO)₂PS₂]₃ (II) chelate compounds were determined from X-ray diffraction (XRD) data (CAD-4 diffractometer, MoK _β radiation, 1193 F _hkl , R = 0.0516 for I and 513 F _hkl , R = 0.0305 for II). Crystals I are monoclinic: a = 14.233(3) Å, b = 13.570(3) Å, c = 14.272(3) Å; β = 90.66(3)°, V = 2756.3(10) ų, Z = 4, ρ_calc = 1.587 g/cm³, space group C2/c. Crystals II are trigonal: a = 15.149(2) Å, c = 30.306(6) Å; V = 6023.2(16) ų, Z = 6, ρ_calc = 1.493 g/cm³, space group R3ˉ. Structures I and II consist of discrete mononuclear molecules. The coordination polyhedra of the M atoms (M = Rh, Co) are distorted octahedra formed by six sulfur atoms of three cyclic bidentate (RO)₂ PS₂⁻ ligands. Original Russian Text Copyright ? 2008 by R. F. Klevtsova, L. A. Glinskaya, and S. V. Larionov __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 49, No. 2, pp. 330–334, March–April, 2008.     

Low temperature complete combustion of dilute propane over Mn-doped ZrO2 (cubic) catalysts

Combustion of dilute propane (0.9 mol%) over Mn-doped ZrO₂ catalysts prepared using different precipitating agents (viz. TMAOH, TEAOH, TPAOH, TBAOH and NH₄OH), having different Mn/Zr ratios (0.05—0.67) and calcined at different temperatures (500—800°C), has been thoroughly investigated at different temperatures (300—500°C) and space velocities (25,000–100,000 cm³ g⁻¹ h⁻¹) for controlling propane emissions from LPG-fuelled vehicles. Mn-doped ZrO₂ catalyst shows high propane combustion activity, particularly when its ZrO₂ is in the cubic form, when its Mn/Zr ratio is close to 0.2 and when it is prepared using TMAOH as a precipitating agent and calcined at 500—600°C. Pulse reaction of propane in the absence of free-O₂ over Mn-doped ZrO₂ (cubic) and Mn-impregnated ZrO₂ (monoclinic) catalysts has also been investigated for studying the relative reactivity and mobility of the lattice oxygen of the two catalysts. Both reactivity and mobility of the lattice oxygen of Mn-doped ZrO₂ are found to be much higher than that of Mnimpregnated ZrO₂. Propane combustion over Mn-doped ZrO₂ catalyst involves a redox mechanism     

Ag3PO4/Ag2S/g-C3N4复合光催化剂的制备与性能

通过沉积法和离子交换法成功地制备了Ag_3PO_4/Ag_2S/g-C_3N_4复合型光催化剂。利用X射线多晶粉末衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、N_2吸附-脱附等温线、紫外-可见漫反射光谱、荧光光谱等手段对样品进行了表征。通过降解罗丹明B考察其可见光催化活性及稳定性,研究了硫化钠与磷酸银物质的量的比值(n_(Na_2S)/n_(Ag_3PO_4))、g-C_3N_4添加量对所制备复合光催化材料性能的影响,同时对光催化机理进行了探讨。结果表明,随着n_(Na2S)/n_(Ag3PO4)的增加,所得复合催化材料活性先增加后降低;当n_(Na2S)/n_(Ag_3PO_4)为1.5%、g-C_3N_4与Ag_3PO_4的质量比为3∶7时制备的催化剂ASC1.5的光催化活性最好,在可见光照射下,40 min内可将罗丹明B完全降解,且5次循环使用后仍保持较高的催化活性。和Ag_3PO_4相比,Ag_3PO_4/Ag_2S/g-C_3N_4复合型光催化材料的活性与稳定性都得到明显提高,这主要归因于复合催化剂比表面积和孔结构的增加,载流子分离效率的提高。光催化机理研究表明,空穴(h~+)、超氧阴离子自由基(·O~(2-))和羟基自由基(·OH)都是光催化过程中的主要活性物种。三者作用大小依次为:h~+·O~(2-)·OH。     

Cr3+在不同基质Y3Ga5O12或Ga2O3中的荧光特性

以Ga_2O_3、Y_2O_3、Cr(NO_3)_3·9H_2O为原料,柠檬酸为配位剂,通过溶胶-凝胶高温固相合成法制备出Ga_(2-2x)O_3∶2xCr~(3+)(Ga_2O_3∶xCr)与Y_3Ga_(5-5x)O_(12)∶5xCr~(3+)(YGG∶xCr)2种多晶粉体(x=0.01,0.03,0.05,0.07)。并采用X射线衍射(XRD)、红外光谱(IR)、扫描电镜(SEM)、荧光光谱(PL)对样品的结构、组成、形貌和荧光性能进行测试分析。XRD和IR分析结果显示在900℃煅烧后Ga_2O_3∶xCr和YGG∶xCr两种样品均成相。SEM照片显示Ga_2O_3∶xCr样品形貌为柱形多面体,YGG∶xCr为短棒状。PL结果显示Cr~(3+)在Ga_2O_3和YGG两种基质中的最强荧光发射峰分别位于742和740 nm,均属于Cr~(3+)的~2E-~4A_2跃迁,对比发现Cr~(3+)在YGG基质中的荧光发射强度更强,在远红光区的荧光性能更好,能满足温室照明中植物光合作用的需求。     

Synthesis of nano-sized crystalline oxide ion conducting fluorite-type Y2O3-doped CeO2 using perovskite-like BaCe0.9Y0.1O2.95 (BCY) and study of CO2 capture properties of BCY

Formation of nano-sized Y₂O₃-doped CeO₂ (YCO) was observed in the chemical reaction between proton conducting Y₂O₃-doped BaCeO₃ (BCY) and CO₂ in the temperature range 700-1000 °C, which is generally prepared by wet-chemical methods that include sol-gel, hydrothermal, polymerization, combustion, and precipitation reactions. BCY can capture CO₂ of 0.13 g per ceramic gram at 700 °C, which is comparable to that of the well-known Li₂ZrO₃ (0.15 g per ceramic gram at 600 °C). Powder X-ray diffraction (PXRD), energy dispersive X-ray analysis (EDX), laser particle size analysis (LPSA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ac impedance spectroscopy were employed to characterize the reaction product obtained from reaction between BCY and CO₂ and subsequent acid washing. PXRD study reveals presence of fluorite-like CeO₂ (a=5.410 (1) Å) structure and BaCO₃ in reaction products. TEM investigation of the acid washed product showed the formation of nano-sized material with particle sizes of about 50 nm. The electrical conductivity of acid washed product (YCO) in air was found to be about an order higher than the undoped CeO₂ reported in the literature.