Hydrothermal synthesis, crystal structure and characterization of [Zn(H2O)4]2 [H2As6V15O42(H2O)]·2H2O

The compound [Zn(H₂O)₄]₂[H₂As₆V₁₅O₄₂(H₂O)]·2H₂O (1) has been synthesized and characterized by elemental analysis, IR, ESR, magnetic measurement, third-order nonlinear property study and single crystal X-ray diffraction analysis. The compound 1 crystallizes in trigonal space group R3, a=b=12.0601(17) Å, c=33.970(7) Å, γ=120°, V=4278.8(12) Å³, Z=3 and R1(wR2)=0.0512 (0.1171). The crystal structure is constructed from [H₂As₆V₁₅O₄₂(H₂O)]⁴⁻ anions and [Zn(H₂O)₄]²⁺ cations linked through hydrogen bonds into a network. The [H₂As₆V₁₅O₄₂(H₂O)]⁶⁻ cluster consists of 15 VO₅ square pyramids linked by three As₂O₅ handle-like units.     

Silica xerogel-hydrogen peroxide composites: their morphology, stability, and antimicrobial activity

Hydrogen peroxide was incorporated into silica xerogel matrix over the concentration range from 3.8 to 68.0 wt% via the sol–gel route. The obtained composites were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The release rates of H₂O₂ from the composites into the aqueous phase were examined. In most cases, a 90% release was attained after ca. 10 min, and it was only slightly dependent on H₂O₂ concentration and particle size. The antimicrobial activity of the composite containing 3.59% H₂O₂ was evaluated against Escherichia coli and Micrococcus luteus. A comparative assay was carried out for aqueous solution of H₂O₂ of the same concentration. The results demonstrated a potent microbicidal efficacy of the composite. Furthermore, diffusion range of the hydrogen peroxide from the solid composite into an agar medium matched that of the H₂O₂ in aqueous solution. The stability tests with the xerogels containing 3.8, 26.4, and 68.0% of H₂O₂ showed that after 63 days respective losses of the H₂O₂ at 3 °C were 8.8, 9.7, and 6.2%. Both the DSC results and the stability tests have shown that the molecular water present in the pores stabilizes the composite, probably through improving the binding of the H₂O₂ molecules onto the silica surface.     

Large heteropolymetalate complexes formed from lanthanide (Y, Ce, Pr, Nd, Sm, Eu, Gd), nickel cations and cryptate [As4W40O140]: synthesis and structure characterization

A new family of heteropolytungstate complexes (NH₄)₂₁[Ln(H₂O)₅{Ni(H₂O)}₂As₄W₄₀O₁₄₀]·xH₂O(Ln=Y, Ce, Pr, Nd, Sm, Eu, Gd) were prepared by the reaction of Na₂₇[NaAs₄W₄₀O₁₄₀]·60H₂O with NiCl₂·6H₂O and Ln(NO₃)₃·xH₂O at pH≈4.5. The crystal structures of (NH₄)₂₁[Gd(H₂O)₅{Ni(H₂O)}₂As₄W₄₀O₁₄₀]·51H₂O was determined by X-ray diffraction analysis and element analysis. The compound crystallizes in the monoclinic space group P2₁/n with a=19.754(3), b=24.298(4), c=39.350(6) Å, β=100.612(3)°, V=18564(5) ų, Z=2, R1(wR₂)=0.0544(0.0691). The central site S1 and two opposite sites S2 of the big cyclic ligand [As₄W₄₀O₁₄₀]²⁸⁻ are occupied by one Ln³⁺and two Ni²⁺, respectively, each site supply four O_d coordinating to metal ion, another one water molecule and other five water molecules coordinate, respectively, to Ni²⁺and Ln³⁺. Polyanion [Ln(H₂O)₅{Ni(H₂O)}₂As₄W₄₀O₁₄₀]²¹⁻ has C_2v symmetry. IR and UV–vis spectra of [NaAs₄W₄₀O₁₄₀]²⁷⁻ of the title compounds are discussed.     

氨基醇杂多酸类离子液体催化环酮的Baeyer-Villiger氧化反应

合成了一系列氨基醇杂多酸类离子液体,并将其用于催化环酮的Baeyer-Villiger氧化反应.以2-庚基环戊酮为模板底物,H₂O₂为氧化剂,探究了此类氨基醇杂多酸类离子液体的催化活性,筛选出催化活性最高的催化剂为[Pro-ps]H₂PW₁₂O₄₀,最佳反应条件:n(2-庚基环戊酮)∶n(催化剂)∶n(H₂O₂)=1∶0. 03∶4,反应温度40℃,反应时间8 h,无溶剂.在最佳条件下,2-庚基环戊酮的转化率为98. 19%,产物δ-十二内酯的选择性可达82. 84%.水相中的离子液体[Pro-ps]H₂PW₁₂O₄₀经干燥后可以重复使用.经过5次循环使用后催化活性未见明显下降.[Pro-ps]H₂PW₁₂O₄₀还可用于催化其它多种环酮的Baeyer-Villiger氧化反应,结果表明,该催化剂具有良好的...     

Thermal decomposition study on mixed ligand thymine complexes of divalent nickel(II) with dianions of some dicarboxylic acids

Thermal decomposition of mixed ligand thymine (2,4-dihydroxy-5-methylpyrimidine) complexes of divalent Ni(II) with aspartate, glutamate and ADA (N-2-acetamido)iminodiacetate dianions was monitored by TG, DTG and DTA analysis in static atmosphere of air. The decomposition course and steps of complexes [Ni(C₅H₆N₂O₂)(C₄H₅NO₄)²⁻(H₂O)₂]·H₂O, [Ni(C₅H₆N₂O₂)(C₅H₇NO₄)²⁻(H₂O)₂]·H₂O and [Ni(C₅H₆N₂O₂)(C₆H₈N₂O₅)²⁻(H₂O)₂]·1.5H₂O were analyzed. The final decomposition products are found to be the corresponding metal oxides. The kinetic parameters namely, activation energy (E*), enthalpy (ΔH*), entropy (ΔS*) and free energy change of decomposition (ΔG*) are calculated from the TG curves using Coats–Redfern and Horowitz–Metzger equations. The stability order found for these complexes follows the trend aspartate > ADA > glutamate.     

Use of a manganese dioxide column in the flow enthalpimetric determination of hydrogen peroxide

A method for flow enthalpimetric determination of H₂O₂ is described. The method uses manganese dioxide to catalyse the decomposition of H₂O₂. The catalyst is stable enough to be used for at least 500 analyses. H₂O₂ in the concentration range 0.01–10mM is determined with coefficients of variation < 2%. The method has been used for determination of glucose in a non-alcoholic beverage and wines, with glucose oxidase as the peroxide-producing enzyme.     

Spectrophotometric determination of hydrogen peroxide in rainwater

Hydrogen peroxide in rainwater has been determined from the measurement of absorption at 432 nm after the formation of the stable oxo-peroxo-pyridine-2,6-dicarboxylatovanadate(V) complex (OPDV) in acid media. Determinations were in good agreement with those using a modified p-hydroxyphenylacetic acid (PHPA) emission method. The linear range for the OPDV method is from 0.05 to 50 ppm H₂O₂, and the limit of detection under the analytical conditions employed was 5.8 nmol H₂O₂ for a 20 cm³ rainwater sample. The volume weighted mean H₂O₂ concentration in rainwater collected at roof-top level in central Kowloon was 15.9 μM (N=10), and the ratio of non-sea salt sulphate and H₂O₂ concentrations was significantly correlated with pH. The OPDV absorption method was also employed for the determination of ambient gaseous H₂O₂, and liquid-nitrogen cold-trap collection gave results about 30% lower than impinger sampling, where artifact H₂O₂ formation occurred.     

Factors influencing decomposition of H2O2 over supported Pd catalyst in aqueous medium

Since H₂O₂ decomposition can result in selectivity/yield loss in the direct H₂O₂ synthesis process from H₂ and O₂ over supported Pd catalysts, it is important to have an enhanced understanding about the factors affecting the H₂O₂ decomposition reaction. Herein, detailed studies have been undertaken to investigate the influence of different factors, such as (a) nature and concentration of acid in reaction medium, (b) nature and concentration of halide in presence and absence of acid in reaction medium, (c) pretreatment procedures and (d) catalyst modification by incorporation of different halides, on the H₂O₂ decomposition reaction over a 5% Pd/C catalyst in aqueous medium at 25 °C. This study has shown that the H₂O₂ decomposition activity is profoundly influenced by all the above factors. The effectiveness of the acids in suppressing the H₂O₂ decomposition activity decreased in the following order: hydroiodic acid > hydrobromic acid > hydrochloric acid  acetic acid > phosphoric acid > sulfuric acid > perchloric acid. The ability of the acid to decrease the H₂O₂ decomposition activity was found to very strongly depend on the nature of its associated anion. Halides, such as iodide, bromide and chloride were particularly effective in suppressing the H₂O₂ decomposition activity. Oxidation pretreatment of the catalyst was found to strongly suppress its H₂O₂ decomposition activity, while a reduction treatment was found to promote its activity. A gradual decrease in the H₂O₂ decomposition activity of the catalyst was observed with each successive usage due to in situ sub-surface oxidation of Pd by H₂O₂. Halide incorporation either via the reaction medium or prior catalyst modification had a similar qualitative effect on the H₂O₂ decomposition activity.     

Protein nanoparticles containing Cu(II) and DOX for efficient chemodynamic therapy via self-generation of H2O2

Chemodynamic therapy (CDT) refers to generating hydroxyl radical (^·OH) in tumor sites via hydrogen peroxide (H₂O₂) catalyzed by transition metal ions in cancer cells under acidic environment. However, H₂O₂ content is not enough for effective CDT, although H₂O₂ content in cancer cells is higher than that of normal cells. Herein, we synthesized DOX@BSA-Cu NPs (nanoparticles) for effective CDT by providing enhanced content of H₂O₂ in cancer cells. The results proved Cu²⁺ in NPs could be reduced to Cu⁺ by glutathione (GSH) and effectively converted H₂O₂ to ^·OH. Moreover, the loaded low-dose doxorubicin (DOX) in the NPs could improve the content of H₂O₂ and resulted in more efficient generation of ^·OH in cancer cells. Thus DOX@BSA-Cu NPs exhibited higher cytotoxicity to cancer cells. This research may provide new ideas for the further studies on more effective Cu(II)-based CDT nanoagents.     

Spectrophotometric determination of H(2)O(2) in marine waters with leuco crystal violet

H₂O₂ in marine waters may be determined by measuring the absorbance of crystal violet (CV⁺), formed by the oxidation of leuco crystal violet (LCV) by H₂O₂ in the presence of the enzyme horseradish peroxidase, at 592 nm at pH 4. The detection limit and the precision of the method are about 0.02 μM and ± 1% (at a concentration of 0.03 μM), respectively. The results obtained by this method and by a widely used fluorimetric method agreed with each other well. After color development, samples together with the sub-samples for constructing the calibration curve may be stored for up to 5 days before their absorbances are measured without significantly changing the estimated concentration of H₂O₂.     

α,β,γ,δ,ε,η-Bi2O3电子结构和光学性质的第一性原理研究

基于密度泛函理论的CASTEP模块研究了α, β, γ, δ, ε和η-Bi₂O₃晶型, 计算分析了其几何结构、 能带结构、 电子态密度和光学性质. 结果表明, α, ε和η相均为层状结构, 其中, α和ε相为单层—Bi—O—结构, 而η相为双层—Bi—O—结构; β, γ和δ相为—Bi_m—O_n—交错结构, 其中δ相交错尤为密集, 呈现导体特性. 各晶相的导带均由Bi 6p态构成, 价带由O_2p态起主导作用. 电势电位分析结果表明, 6种晶相价带电位均在H₂O/O₂之下, 具有强氧化能力, 与实验报道的光催化氧化能力大小顺序γ-Bi₂O₃>β-Bi₂O₃>α-Bi₂O₃>δ-Bi₂O₃一致, 而导带还原电位低于H₂/H₂O, 预测纯Bi₂O₃很难具备催化产氢能力. 光学性质分析发现, γ和δ相的起始响应波长较大, 说明其应具备红外激发的性质. 这些结果可为获得偏红外激发和较宽光谱响应的Bi₂O₃材料研究提供理论基础, 为研发和应用Bi₂O₃及其复合物提供重要的指导.     

核-壳结构多酸/磁性铈铁纳米复合氧化物@SiO2吸附-氧化脱硫性能

水热法合成了铈铁纳米复合氧化物,采用化学沉积法在其表面包裹SiO₂制备核-壳结构磁性材料,以其为载体负载H₂O₂结合Keggin结构磷钼酸(HPMo)制备了HPMo-H₂O₂/CeFe_xO_y@SiO₂吸附-氧化脱硫催化剂。 采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶红外光谱(FT-IR)、X射线粉末衍射(XRD)、氮气吸附脱附(BET)、³¹P魔角核磁共振(MAS-NMR)和X射线光电子能谱(XPS)等对催化剂的结构进行表征。 结果表明,SiO₂将CeFe_xO_y包裹形成核-壳结构纳米复合材料,以其为载体负载HPMo-H₂O₂后Keggin型多酸的骨架结构保持,并产生少量过氧化磷钼酸盐活性物种。 不同催化剂对有机硫化物二苯并噻吩(DBT)的吸附脱硫和氧化脱硫性能,均呈现出HPMo-H₂O₂/CeFe_xO_y@SiO₂＞CeFe_xO_y@SiO₂＞CeFe_xO_y的活性顺序,多酸的引入大大提升了其对大分子有机硫化物的吸附和氧化脱除性能,催化氧化脱硫活性的提高源于多酸分子“假液相”反应过程的结果。 在反应温度60 ℃,反应3 h,m(油)∶m(催化剂)=35∶1,n(O)∶n(S)=10∶1的条件下,对DBT氧化脱除率达到99.4%。 制备的磁性核-壳结构氧化脱硫剂有理想的氧化脱除DBT的循环使用性能,并且可通过外加磁场进行简单分离,是一类制备方法简单、催化活性高且稳定性好的绿色环保型催化剂。     

溶解有机质对光照自然水体生物膜体系中H2O2生成的影响

通过模拟实验研究了生物膜胞外聚合物(EPS)和乙二胺四乙酸(EDTA) 2种典型溶解有机质(DOM)成分对自然水体生物膜体系中过氧化氢(H₂O₂)生成特征的影响, 并研究了体系初始pH值、 DOM浓度、 溶解氧(DO)等因素的影响. 结果表明, DOM的存在对自然水体生物膜体系中H₂O₂的生成有明显影响. 光照能促使EPS产生H₂O₂, 而EPS的存在对生物膜产生H₂O₂的直接影响不显著, EPS与生物膜共存体系中的H₂O₂由二者共同产生; EDTA本身不产生H₂O₂, 且对H₂O₂分解影响很小, 但会显著抑制生物膜产生H₂O₂, 且浓度越高抑制作用越明显. 体系pH值、 DOM浓度和DO均能不同程度影响EPS产生H₂O₂及EDTA抑制生物膜产生H₂O₂的作用.     

Nitrite formation in the radiolysis of aerated aqueous solutions of ammonia

Gamma irradiation of aerated aqueous solutions of ammonia leads to the formation of nitrite as a radiolytic product. Its yield increases with increasing concentration of NH₃ as well as O₂. OH radicals react with NH₃ to give NH₂ radicals, which in the presence of O₂ form NH₂O₂ radicals. These radicals finally lead to the formation of nitrite. G(NO₂⁻) decreases with increasing radiation dose due to secondary reactions. Its initial yield, however, is more than 1/2G_OH, while hydrogen peroxide yield is less than the expected value viz. G(H₂O₂) + 1/2G(e_aq⁻), indicating its participation in reactions with radiation produced free radicals. G(H₂) is 0.35 in aerated aqueous solutions of 10⁻³ mol dm⁻³ NH₃ and 0.23 in the absence of oxygen. Implications of these results to the use of NH₃ in primary coolant water of pressurized water nuclear power reactors of the VVER type are discussed.     

Multiple bonds between main group elements and transition metals, 155. (Hexamethylphosphoramide) methyl(oxo) bis(η-peroxo)rhenium(VII), the first example of an anhydrous rhenium peroxo complex: crystal structure and catalytic properties

Methyl(oxo)bis(η²-peroxo)rhenium(VII)1, the active species of the system CH₃ReO₃/H₂O₂ in the catalytic oxidation of different organic and organometallic compounds, is stabilized by a water molecule attached to the rhenium center. This water molecule can be removed and substituted by hexamethylphosphoramide (HMPA) to yield (hexamethylphosphoramide)methyl(oxo)bis(η²-peroxo rhenium(VII) (3). The synthesis, crystal structure (X-ray difraction study), and catalytic properties of which compound are reported. Crystal data are as follows: monoclinic, space group P2₁/n, A = 900.76(7) pm, B = 1229.80(11) pm, C = 1318.57(11) pm, β = 90.251(7)°, R_w = 0.034 for 1878 reflections. The catalytic properties of compound 3 in the oxidation of olefins with H₂O₂ are similar to those of 1.     

Extraction and determination of molybdenum with tributyl phosphate Application to analysis of copper-molybdenum ores

A differential spectrophotometric method is described for the determination of molybdenum by means of solvent extraction with tributylphosphate of the peroxymolybdate complex formed with H₂O₂ in 3.5N H₂SO₄. The extraction parameters are studied, and the behaviour of some other ions is reported. The method is used for ore analysis.     

制备条件对Ru/Ce_(0.8)Zr_(0.2)O_2催化剂上CO_2甲烷化反应性能的影响

采用均相法制得Ce0.8Zr0.2O2载体,并以其为载体等体积浸渍制得一系列负载型Ru催化剂。在0.1 MPa、GHSV为10000 h-1、H2/CO2为3.5(物质的量比)的条件下,对催化剂进行评价。借助TG-DSC、BET、H2-TPR等技术对所制备的载体和催化剂进行表征,结果表明,500℃焙烧的载体具有适中的比表面积和孔径并形成了Ce-Zr固溶体,与载体形成弱相互作用的Ru能够显著提高催化剂的活性,适宜的还原方式能促进活性组分的均匀分布。采用500℃焙烧的载体浸渍Ru Cl3溶液,干燥后在400℃焙烧,并使用水合肼和H2两次还原后的催化剂活性最高,在290℃时,H2转化率可达到93.57%。     

Zr的添加对稀燃天然气汽车尾气净化催化剂Pd-Pt/Al2O3性能的影响

Pd-Pt双金属基甲烷氧化催化剂的催化活性、抗水热老化性和耐硫性在一个通有模拟稀燃天然气汽车尾气成分的固定床反应器中进行检测.研究发现Zr掺杂的Pd-Pt/Al₂O₃ (Pd-Pt/Zr_xAl_(1-x)O_(3+x)/2)提高了催化的催化活性、抗水热老化性和耐硫性.以共沉淀法制备Zr : Al的摩尔比分别为0 : 1、0.25 : 0.75、0.5 : 0.5、0.75 :0.25和1 : 0的材料为载体材料.双金属催化剂的活性组分分别为1.5% (w,质量分数)的Pd和0.3% (w)的Pt,活性组分Pd、Pt通过共浸渍的方法浸渍到以上载体材料上制备得到一系列整体式催化剂.分别采用低温N₂吸脱附、X射线衍射(XRD)、H₂程序升温还原(H₂-TPR)、O₂程序升温氧化(O₂-TPD)及X射线光电子能谱对制备的催化剂进行表征.结果显示Zr的加入使催化剂的载体材料结晶度提高,活性组分的分散度也得到了相应的提高.同时二价Pd物种与周围电子密度分别增加.相比于Pd-Pt/Al₂O₃和Pd-Pt/ZrO₂催化剂,在不同条件预处理后, Zr的添加对催化剂的性能有明显的提高,其中催化剂Pd-Pt/Zr_0.5Al_0.5O_1.75展现了最好的催化活性、抗水热老化性以及耐硫性.     

自然水体生物膜体系中过氧化氢浓度的影响因素

以过氧化氢(H₂O₂)为自然水体生物膜产生的活性氧(ROS)的代表, 通过模拟实验, 研究了水-自然水体生物膜体系中光/暗变化、 生物膜的避光预处理与数量、 有机配体和pH值对体系中H₂O₂浓度的影响. 结果表明, 光照可快速增加体系中H₂O₂浓度, 光照转为无光时体系H₂O₂浓度下降(约为光照时的2/3); 避光预处理会显著降低体系中H₂O₂的产生速率和浓度; 生物膜数量的增减会导致体系H₂O₂浓度的相应增减; 有机配体的存在会使体系内H₂O₂浓度下降(约1/2~1/3); pH=7和5的体系中H₂O₂的浓度高于pH=9的体系(高出约1.5倍). 上述各因素主要通过影响生物膜生产H₂O₂、 H₂O₂自然分解和生物膜去除H₂O₂ 3种作用来影响体系H₂O₂浓度.     

Syntheses and structural determination of nine-coordinate K3[Nd(nta)2(H2O)]·6H2O and K3[Er(nta)2(H2O)]·5H2O

The syntheses and structural determination of Nd^III and Er^III complexes with nitrilotriacetic acid (nta) were reported in this paper. Their crystal and molecular structures and compositions were determined by single-crystal X-ray structure analyses and elemental analyses, respectively. The crystal of K₃[Nd^III(nta)₂(H₂O)]·6H₂O complex belongs to monoclinic crystal system and C2/c space group. The crystal data are as follows: a=1.5490(11) nm, b=1.3028(9) nm, c=2.6237(18) nm, β=96.803(10)°, V=5.257(6) nm³, Z=8, M=763.89, D_c=1.930 g cm⁻³, μ=2.535 mm⁻¹ and F(000)=3048. The final R₁ and wR₁ are 0.0390 and 0.0703 for 4501 (I>2σ(I)) unique reflections, R₂ and wR₂ are 0.0758 and 0.0783 for all 10474 reflections, respectively. The Nd^IIIN₂O₇ part in the [Nd^III(nta)₂(H₂O)]³⁻ complex anion has a pseudo-monocapped square antiprismatic nine-coordinate structure in which the eight coordinate atoms (two N and six O) are from the two nta ligands and a water molecule coordinate to the central Nd^III ion directly. The crystal of the K₃[Er^III(nta)₂(H₂O)]·5H₂O complex also belongs to monoclinic crystal system and C2/c space group. The crystal data are as follows: a=1.5343(5) nm, b=1.2880(4) nm, c=2.6154(8) nm, b=96.033(5)°, V=5.140(3) nm³, Z=8, M=768.89, D_c=1.987 g cm⁻³, μ=3.833 mm⁻¹ and F(000)=3032. The final R₁ and wR₁ are 0.0321 and 0.0671 for 4445 (I>2σ(I)) unique reflections, R₂ and wR₂ are 0.0432 and 0.0699 for all 10207 reflections, respectively. The Er^IIIN₂O₇ part in the [Er^III(nta)₂(H₂O)]³⁻ complex anion has the same structure as Nd^IIIN₂O₇ part in which the eight coordinate atoms (two N and six O) are from the two nta ligands and a water molecule coordinate to the central Nd^III ion directly.