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.     

在Y型分子筛中Co2+、Ni2+配合物的合成及其应用研究

用气相法和液相法分别在Y型分子筛的超笼中合成了Co²⁺、Ni²⁺的乙二胺配合物,并用红外(FT-IR)、顺磁共振(ESR)等方法对配合物的组成和稳定性进行了研究。CO²⁺的单核配合物在室温下可与O₂分子形成加合物,这种优先并可逆地吸附氧气的性能在氧气富集、对空气进行氧氮分离和食品保鲜等方面有广泛的用途。     

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.     

Chromium(III) Hydroxide Solubility in The Aqueous Na+-OH?-H2PO?4-HPO2?4-PO3?4-H2O System: A Thermodynamic Model

Chromium(III)-phosphate reactions are expected to be important in managing high-level radioactive wastes stored in tanks at many DOE sites. Extensive studies on the solubility of amorphous Cr(III) solids in a wide range of pH (2.8–14) and phosphate concentrations (10^–4 to 1.0 m) at room temperature (22±2)°C were carried out to obtain reliable thermodynamic data for important Cr(III)-phosphate reactions. A combination of techniques (XRD, XANES, EXAFS, Raman spectroscopy, total chemical composition, and thermodynamic analyses of solubility data) was used to characterize solid and aqueous species. Contrary to the data recently reported in the literature,⁽¹⁾ only a limited number of aqueous species [Cr(OH)₃H₂PO^–₄, Cr(OH)₃(H₂PO₄)^2–₂), and Cr(OH)₃HPO^2–₄] with up to about four orders of magnitude lower values for the formation constants of these species are required to explain Cr(III)-phosphate reactions in a wide range of pH and phosphate concentrations. The log K^o values of reactions involving these species [Cr(OH)₃(aq)+H₂PO^–₄⇌Cr(OH)₃H₂PO^–₄; Cr(OH)₃(aq)+2H₂PO^–₄⇌Cr(OH)₃(H₂PO₄)^2–₂; Cr(OH)₃(aq)+HPO^2–₄⇌Cr(OH)₃HPO^2–₄] were found to be 2.78±0.3, 3.48±0.3, and 1.97±0.3, respectively.     

Redox chemistry of o- and m -hydroxycinnamic acids: A pulse radiolysis study

Radiation chemical reactions of^•OH, O^•−, N₃ ^•and e _aq ^t- witho- and m-hydroxycinnamic acids were studied. The second-orderrateconstantsforthereaction of^•OH with ortho and meta isomers in buffer solution at pH7 are 3.9±0.2 × 10⁹ and 4.4 ± 0.3 × 10⁹ dm³ mol^-1 s^-1 respectively. At pH 3 the rate with the ortho isomer was halved (1.6 ± 0.4 × 10⁹ dm³ mol^-1 s^-1) but it was unaffected in the case of meta isomer (k = 4.2±0.6 × 10⁹dm³mol^-1 s^-1). The rate constant in the reaction of N₃ ^• with the ortho isomer is lower by an order of magnitude (k = 4.9 ± 0.4 × 10⁸ dm³ mol^-1s^-1). The rates of the reaction of e _aq ^t- with ortho and meta isomers were found to be diffusion controlled. The transient absorption spectrum measured in the^•OH witho-hydroxycinnamic acid exhibited an absorption maximum at 360 nm and in meta isomer the spectrum was blue-shifted (330 nm) with a shoulder at 390 nm. A peak at 420 nm was observed in the reaction of O^bb−with theo-isomer whereas the meta isomer has a maximum at 390 and a broad shoulder at 450 nm. In the reaction of the absorption peaks were centred at 370–380 nm in both the isomers. The underlying reaction mechanism is discussed.     

Oxidative addition of dihydrogen to Ni(II) complexes.ab initio MO/MP4 calculations of the electronic structure of NiH2Cl2(PH3)2 complex

Electronic state d⁶ Ni(IV) in the complex [NiH₂Cl₂(PH₃)₂] was studied by means ofab initio MO/MP4 calculations.     

Complexing tendencies of UO 22+ and Th4+ in their mixed ligand complexes with aminopolycarboxylates and resorcinol or its derivatives

Formation contants (log K _MAL ^MA ) of mixed ligand complexes MAL, where M = UO ₂ ²⁺ or Th⁴⁺, A = IMDA, NTA, HEDTA, EDTA, CDTA or DTPA, and L = resorcinol (res), 2-methyl resorcinol (2-Me-res), 5-methyl resorcinol (5-Me-res) or 4-chloro resorcinol (4-Cl-res), have been determined pH-metrically by the Irving-Rossotti approach at 25°C and at an ionic strength,I = 0.2(moldm⁻³KNO₃). The observed stability sequences are IMDA > NTA > HEDTA > EDTA > CDTA > DTPA, and 4-Cl-res > 5-Me-res > 2-Me-res > res with respect to primary and secondary ligands, respectively. Th⁴⁺ forms more stable mixed complexes than UO ₂ ²⁺ . The A ΔlogK values are negative due mainly to the charge repulsion involved in the complexation MA + L⇋MAL.     

空气中合成固溶体荧光粉Ba_2(Zn,Mg)Si_2O_7∶Eu~(2+),Eu~(3+),Ce~(3+)及其发光特性

采用高温固相法在空气中合成了Ba1.97-yZn1-xMgxSi2O7∶0.03Eu,y Ce3+系列荧光粉。分别采用X-射线衍射和荧光光谱对所合成荧光粉的物相和发光性质进行了表征。在紫外光330~360 nm激发下,固溶体荧光粉Ba1.97-yZn1-xMgxSi2O7∶0.03Eu的发射光谱在350~725 nm范围内呈现多谱峰发射,360和500 nm处有强的宽带发射属于Eu2+离子的4f 65d1-4f 7跃迁,590~725 nm红光区窄带谱源于Eu3+的5D0-7FJ(J=1,2,3,4)跃迁,这表明,在空气气氛中,部分Eu3+在Ba1.97-yZn1-xMgxSi2O7基质中被还原成了Eu2+;当x=0.1时,荧光粉Ba1.97Zn0.9Mg0.1Si2O7∶0.03Eu的绿色发光最强,表明Eu3+被还原成Eu2+离子的程度最大。当共掺入Ce3+离子后,形成Ba1.97-yZn0.9Mg0.1Si2O7∶0.03Eu,y Ce3+荧光粉体系,其发光随着Ce3+离子浓度的增大由蓝绿区经白光区到达橙红区;发现名义组成为Ba1.96Zn0.9Mg0.1Si2O7∶0.03Eu,0.01Ce3+的荧光粉的色坐标为(0.323,0.311),接近理想白光,是一种有潜在应用价值的白光荧光粉。讨论了稀土离子在Ba2Zn0.9Mg0.1Si2O7基质中的能量传递与发光机理。     

纳米Fe_3O_4及钴离子掺杂Fe_3O_4:有机碱共沉淀制备和磁性质

以有机碱四甲基氢氧化铵(TMAH)为沉淀剂合成了纳米Fe3O4和Co2+掺杂的纳米Fe3O4粒子。分别讨论了碱用量,铁盐溶液浓度,反应温度,有机碱及PEG-4000的分散性等因素对纳米Fe3O4的形貌影响。结果表明,所合成的纳米Fe3O4为30nm左右的反尖晶石型面心立方结构,有机碱除了起沉淀剂作用,还能够提高纳米Fe3O4的分散性。本文还讨论了不同Co2+掺入量的纳米Fe3O4粒子的磁性质,结果表明Co2+掺杂的纳米Fe3O4粒子的矫顽力在不同掺入量的下有较大的改变。当Co2+掺入量为10.0%时,纳米Fe3O4的矫顽力达到最大值,为1628Oe。     

Promoting effect of doped cobalt on catalysis of SiO2-supported rhodium for propylene hydroformylation

According to infrared spectroscopy and temperature programmed reduction (TPR), doped Co^o to Rh^o/SiO₂ can play an electron-donating role and prevent the oxidation of Rh^o by surface OH⁻. The interaction between monometallic cobalt and rhodium particles which are probably in close contact results in a strong enhancement of catalytic propylene hydroformylation.     

Low-temperature heat capacity and standard enthalpy of formation of neodymium glycine perchlorate complex [Nd2(Gly)6(H2O)4](ClO4)6·5H2O

Rare-earth perchlorate complex coordinated with glycine [Nd₂(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O was synthesized and its structure was characterized by using thermogravimetric analysis (TG), differential thermal analysis (DTA), chemical analysis and elementary analysis. Its purity was 99.90%. Heat capacity measurement was carried out with a high-precision fully-automatic adiabatic calorimeter over the temperature range from 78 to 369 K. A solid-solid phase transformation peak was observed at 256.97 K, with the enthalpy and entropy of the phase transformation process are 4.438 kJ mol⁻¹ and 17.270 J K⁻¹ mol⁻¹, respectively. There is a big dehydrated peak appears at 330 K, its decomposition temperature, decomposition enthalpy and entropy are 320.606 K, 41.364 kJ mol⁻¹ and 129.018 J K⁻¹ mol⁻¹, respectively. The polynomial equations of heat capacity of this compound in different temperature ranges have been fitted. The standard enthalpy of formation was determined to be −8023.002 kJ mol⁻¹ with isoperibol reaction calorimeter at 298.15 K.     

空气中合成固溶体荧光粉Ba2(Zn, Mg)Si2O7:Ce3+,Eu2+,Eu3+及其发光特性

采用高温固相法在空气中合成了Ba_1.97-yZn_1-xMg_xSi₂O₇:0.03Eu,yCe³⁺系列荧光粉。分别采用X-射线衍射和荧光光谱对所合成荧光粉的物相和发光性质进行了表征。在紫外光330~360 nm激发下,固溶体荧光粉Ba_1.97-yZn_1-xMg_xSi₂O₇:0.03Eu的发射光谱在350~725 nm范围内呈现多谱峰发射,360和500 nm处有强的宽带发射属于Eu²⁺离子的4f⁶5d¹-4f⁷跃迁,590~725 nm红光区窄带谱源于Eu³⁺的⁵D₀-⁷F_J (J=1,2,3,4)跃迁,这表明,在空气气氛中,部分Eu³⁺在Ba_1.97-yZn_1-xMg_xSi₂O₇基质中被还原成了Eu²⁺;当x=0.1时,荧光粉Ba_1.97Zn_0.9Mg_0.1Si₂O₇:0.03Eu的绿色发光最强,表明Eu³⁺被还原成Eu²⁺离子的程度最大。当共掺入Ce³⁺离子后,形成Ba_1.97-yZn_0.9Mg_0.1Si₂O₇:0.03Eu,yCe³⁺荧光粉体系,其发光随着Ce³⁺离子浓度的增大由蓝绿区经白光区到达橙红区;发现名义组成为Ba_1.96Zn_0.9Mg_0.1Si₂O₇:0.01Ce³⁺,0.03Eu的荧光粉的色坐标为(0.323,0.311),接近理想白光,是一种有潜在应用价值的白光荧光粉。讨论了稀土离子在Ba₂Zn_0.9Mg_0.1Si₂O₇基质中的能量传递与发光机理。     

A Simple Fluorometric Method Using Chlorophyll a for Determination of Hg2+ Ion

A simple and green analytical procedure based on chlorophyll a is presented for the determination of Hg²⁺ ion. Chlorophyll a was extracted and purified from the leaves of pea and is employed as a reagent for analysis of Hg²⁺ ion. It displays remarkable fluorescence emission at 674 nm when excited at 412 nm. The emission intensity decreased significantly on exposure to various concentrations of Hg²⁺ ion. This forms the basis for the determination of Hg²⁺ ion. The proposed method was evaluated for sensitivity and selectivity. The linear concentration range was found to be 2.0–10 μM with r² = 0.997 and the limit of detection for Hg²⁺ ion was 1.3 μM. Ions including Pb²⁺, Cd²⁺, Ag⁺, Zn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Mg²⁺, Mn²⁺, Ru³⁺, Er³⁺, K⁺, Na⁺, NH₄⁺, Cl⁻, NO₃⁻, CH₃COO⁻ and SO₄²⁻ did not interfere with the measurement of Hg²⁺ ion even at 500-fold excess. Since chlorophyll a is widely available in the leaves of most plants, and the extraction and purification process is simple, this technique can provide an alternative, sensitive and economical way to determine Hg²⁺ ion.     

Sr7Zr(PO4)6∶xEu2+蓝色荧光粉的合成及其发光特性

通过高温固相反应合成了新型的蓝色荧光粉Sr₇Zr(PO₄)₆∶xEu²⁺。通过X射线粉末衍射(XRD)、紫外可见(UV-Vis)吸收光谱、荧光光谱研究了Sr₇Zr(PO₄)₆∶xEu²⁺材料的相纯度及荧光性质。结果表明,Eu²⁺掺杂获得的Sr₇Zr(PO₄)₆∶xEu²⁺荧光粉为纯相,且200~400 nm范围内的近紫外(NUV)光均能对其进行有效的激发。在315 nm的激发下,Sr₇Zr(PO₄)₆∶xEu²⁺荧光粉发射出峰值位于415 nm左右的蓝光,且Eu²⁺在Sr₇Zr (PO₄)₆基质中的最佳掺杂浓度为0.05,相应的CIE色度坐标为(0.164,0.021),比商用BaMgAl₁₀O₁₇∶Eu²⁺(BAM)蓝色荧光粉具有更高的色纯度。     

Ho3+/Yb3+共掺ZnO-Al2O3-GeO2-SiO2玻璃陶瓷的制备和上转换发光性质

综合ZnO-Al₂O₃-SiO₂系和锗酸盐玻璃陶瓷的优点,采用熔融-晶化法首次制备了Ho³⁺/Yb³⁺共掺以ZnAl₂O₄为主晶相的ZnO-Al₂O₃-GeO₂-SiO₂系玻璃陶瓷。因[GeO₄]四面体和[SiO₄]四面体都是玻璃网络形成体,讨论了GeO₂取代SiO₂对玻璃陶瓷样品硬度及发光性能的影响,最终确定GeO₂的取代量为10.55%（w/w）时,玻璃陶瓷综合性能最佳。在980 nm泵浦光的激发下,发现强的绿色（546 nm）和弱的红色（650 nm）上转换发光,并研究了不同Ho³⁺/Yb³⁺掺杂比对样品上转换发光的影响,最终结果表明当Ho³⁺/Yb³⁺掺杂比为1：11（n/n）时样品荧光强度最强,在绿色上转换发光材料方面具有潜在的应用。     

La7O6(BO3)(PO4)2:Eu3+/Tb3+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Eu³⁺和Tb³⁺掺杂的La₇O₆（BO₃）（PO₄）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,La₇O₆（BO₃）（PO₄）₂：Eu³⁺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,Eu³⁺的最优掺杂浓度为0.08,对应的CIE坐标为（0.610 2,0.382 3）;La₇O₆（BO₃）（PO₄）₂：Tb³⁺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Tb³⁺的⁵D₄→⁷F₅能级跃迁,Tb³⁺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Eu³⁺和Tb³⁺掺杂的La₇O₆（BO₃）（PO₄）₂荧光材料均具有良好的热稳定性。     

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。     

XRD and UV-Vis diffuse reflectance analysis of CeO2-ZrO2 solid solutions synthesized by combustion method

A series of ceria-incorporated zirconia (Ce_1−xZr_xO₂,x = 0 to 1) solid solutions were prepared by employing the solution combustion synthesis route. The products were characterized by XRD and UV-Vis-NIR diffuse reflectance spectroscopy. The materials are crystalline in nature and the lattice parameters of the solid solution series follow Vegard’s law. Diffuse reflectance spectra of the solid solutions in the UV region show two intense bands at 250 and 297 nm which are assigned respectively to Ce³⁺ ← O²⁻and Ce⁴⁺ ← O²⁻ charge transfer transitions. The two vibrational bands in 6960 cm⁻¹ and 5168 cm⁻¹ in the NIR region indicate the presence of surface hydroxyl groups on these materials.     

Mn4+掺杂Co3O4纳米纤维的静电纺丝法制备及其电化学性能

通过静电纺丝法制备Mn⁴⁺掺杂的Co₃O₄复合纳米纤维,利用XRD、XPS、BET、SEM和电化学工作站等对材料的结构、成分、形貌和电化学性能进行表征与测试。研究发现,通过Mn⁴⁺掺杂,Co₃O₄复合纳米纤维的电化学性能得到明显改善。当n_Co∶n_Mn=20∶2时,相应的复合纤维具有较大比表面积68 m²·g^-1,而且该样品呈现出清晰的氧化还原峰,在1 A·g^-1的电流密度下,放电比电容量为585 F·g^-1,这比纯Co₃O₄纳米纤维的416 F·g^-1,有显著提高;循环500圈电容保持率达到82.6%,而纯Co₃O₄纳米纤维则是76.4%。     

Theoretical study of potential energy surface and vibrational spectra of ArF2 system

Anab initio potential energy surface (PES) of ArF₂ system has been obtained by using MP4 calculation with a large basis set including bond functions. There are two local minimums on the PES: one is T-shaped and the other is L-shaped. The L-shaped minimum is the global minimum with a well depth of -119.62 cm^-1 atR = 0.3883nm. The T-shaped minimum has a well depth of -85.93cm^-1 atR = 0.3486 nm. A saddle point is found atR = 0.3486 and τ = 61° with the well depth of -61.53 cm^-1. The vibrational energy levels have been calculated by using VSCF-CI method. The results show that this PES supports 27 vibrational bound states, and the ground states are two degenerate states assigned to the L-type vibration.