Vinyl Polymerization. 254.∗ Polymerization of Methyl Methacrylate by the System Cellulose-Water-Carbon Tetrachloride

Radical polymerization of methyl methacrylate initiated by the system cellulose-water-carbon tetrachloride was kinetically studied. Results obtained are: 1) The amounts of water, carbon tetrachloride, and cellulose affected the conversion. Michaelis-Menten's equation was applied to the relationship between the rate of polymerization and the amount of MMA. 2) Other methacrylates and acrylates were also polymerized by this system. 3) When methanol or ethanol was used instead of water, some weak polymerization activity was observed. 4) Initiating ability depended on the kind of cellulose used. 5) The activity of cellulose was not changed by washing with boiling water or by solvent extraction. 6) Polymerization was inhibited by the presence of air. 7) Heating in the presence of water and carbon tetrachloride markedly decreased the activity of the cellulose.     

The crystal chemistry of L-Ta2O5 and related structures

Single crystals of a new form of L-Ta₂O₅ with a 19×b superstructure have been synthesised by flux growth. The phase is most likely stabilised by the incorporation of a small amount of lithium (0.14 wt% Li) from the flux. The phase has C-centred monoclinic symmetry with , (), , γ=90.00(1)°. The structure was refined in space group C112/m to R₁=0.044 for 814 unique reflections with F>4σ(F). The structure can be described as comprising chains of edge-shared TaO₇ pentagonal bipyramids that are regularly folded at (010) planes to give sinusoidal chains along [010]. These chains are interconnected along [100] and [001] by corner sharing, creating inter-chain regions that are occupied by isolated TaO₆ octahedra and pairs of corner-shared octahedra. A comparison with published data for high-quality refinements of related structures has led to the development of a general model that can explain the structural chemistry variations in the known L-Ta₂O₅-related structures. A shorthand notation is presented for representing the structures, based on the sequence along [010] of the interchain octahedra.     

Redox properties of N2S2-type nickel complexes with aromatic ligands. Crystal structure of [1,2-C6H4(SMe)NH2]2Ni2+(MeCN)2·2ClO4–

The redox properties of six chelate N₂S₂-type Ni(ii) complexes containing two aromatic NS or one N₂S₂ ligands, such as 2-aminothiophenol, 2-aminothiophenolate anion, 2-amidothiophenolate dianion, 2-amidothioanisole, 2,2"-diaminodiphenyl disulfide dianion, and 8-quinolinethiolate anion, were studied by cyclic voltammetry at a glassy-carbon electrode in DMF. Some free ligands were also studied for comparison. A new Ni^II complex with the 2,2"-diamidodiphenyl disulfide dianion was synthesized. The crystal and molecular structures including the square planar Ni(N₂S₂) center with two MeCN molecules as additional axial ligands were established for the Ni^II complex with 2-aminothioanisole [1,2-C₆H₄(SMe)NH₂]₂Ni²⁺(MeCN)₂·2ClO₄ ^– using X-ray diffraction. The most part of the studied compounds are irreversibly oxidized and reduced; however, bis(2-amidothiophenolato)nickel(iv) and bis(8-quinolinethiolato)nickel(ii) show a quasi-reversible behavior in the reduction region. The electrochemically generated anionic form of the 8-thioquinoline complex is rapidly alkylated in the presence of BuⁿBr or BuⁿI to form, probably, the corresponding butylnickel(iii) complex.     

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

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。     

Exploring the Dual Characteristics of CH3OH Adsorption to Metal Atomic Structures on Si (111)-7 × 7 Surface

Metal atoms were deposited on an Si (111)-7 × 7 surface, and they were adsorbed with alcohol gases (CH₃OH/C₂H₅OH/C₃H₇OH). Initially, C_nH_2n+1OH adsorption was simply used as an intermediate layer to prevent the chemical reaction between metal and Si atoms. Through scanning tunneling microscopy (STM) and a mass spectrometer, the C_nH_2n+1OH dissociation process is further derived as the construction of a surface quasi-potential with horizontal and vertical directions. With the help of three typical metal depositions, the surface characteristics of CH₃OH adsorption are more clearly presented in this paper. Adjusting the preheating temperature, the difference of thermal stability between CH₃O^– and H⁺ could be obviously derived in Au deposition. After a large amount of H⁺ was separated, the isolation characteristic of CH₃O^– was discussed in the case of Fe deposition. In the process of building a new metal-CH₃O^–-H⁺ model, the dual characteristics of CH₃OH were synthetically verified in Sn deposition. CH₃O^– adsorption is prone to influencing the interaction between the metal deposition and substrate surface in the vertical direction, while H⁺ adsorption determines the horizontal behavior of metal atoms. These investigations lead one to believe that, to a certain extent, the formation of regular metal atomic structures on the Si (111)-7 × 7-CH₃OH surface is promoted, especially according to the dual characteristics and adsorption models we explored.     

Accelerated FeIII/FeII redox cycle of Fenton reaction system using Pd/NH2-MIL-101(Cr) and hydrogen

In this paper, a novel improvement in the catalytic Fenton reaction system named MHACF-NH₂-MIL-101(Cr) was constructed based on H₂ and Pd/NH₂-MIL-101(Cr). The improved system would result in an accelerated reduction in Fe^III, and provide a continuous and fast degradation efficiency of the 10 mg L^-1 4-chlorophenol which was the model contaminant by using only trace level Fe^II. The activity of Pd/NH₂-MIL-101(Cr) decreased from 100% to about 35% gradually during the six consecutive reaction cycles of 18 h. That could be attributed to the irreversible structural damage of NH₂-MIL-101(Cr).     

钛铁矿制备二氧化钛-四氧化三铁复合材料及其光催化应用

TiO_2因具有多种优异的特性被广泛应用在半导体光催化领域,但是纳米结构的TiO_2颗粒细微,在进行光催化反应之后,难以回收再利用。本文以廉价钛铁矿为原料制备光催化剂TiO_2,同时利用副产物铁合成Fe_3O_4,并采用简单温和的浸渍法制备Fe_3O_4/TiO_2磁性复合材料。通过XRD、FT-IR、SEM、EDS等手段对材料形态结构进行表征分析,并以光降解有机污染物若丹明B为探针反应,考察其光催化性能。结果表明,质量比为1∶10的Fe_3O_4/TiO_2复合材料结构稳定、分散均匀,具有最优的光催化活性(波长356nm下反应3h,若丹明B降解率达到64.0%),并表现出良好的重复性。同时,动力学结果显示降解符合一级反应动力学。     

氨基酸-BrO-3-Mn2+-H2SO4-丙酮体系的振荡反应

This paper, Using potentiometric method, first reports the oscillating behavior of five amino acids (L-methionine, L-cystine, L-tryptophan, L-serine, L-tyrosine) in a new oscillating system of amino acid-BrO_3~--Mn~(2+)-H_2SO_4-acetone. The effect of many factors on oscillation have been investigated. According to Arrhenius equation, the apparent activation energy of the oscillatary induction period and oscillation period of five oscillating systems are obtained within temperature range of 20～37 ℃.     

Determination of Four Active Oxygen Species Such as H2O2, •OH, •O2 −, and 1O2 by Luminol and CLA-Chemiluminescence Methods and Evaluation of Antioxidative Effects of Hydroxybenzoic Acids

Abstract

Simple and rapid chemiluminescence (CL) assays for H₂O₂, ?OH, ?O₂ ^? and ¹O₂ using 5-amino-2,3-dihydro-1,4-phthalazinedione (luminol) or 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2-α]pyrazin-3-one (CLA) as CL reagents were developed. The means of the intra-assay relative standard deviations of ten replicate measurements of H₂O₂ (25-120 μM), ?OH generated from Fe(II) ion (2.5-10 μM) in the presence of 980 μM H₂O₂, ?O₂ ^? generated from hypoxanthine (HX) (7-50 μM) in the presence of 9 × 10^?3 units xanthine oxidase (XO) and ¹O₂ generated from NaOCl (3-12 mM) in the presence of 97.6 μM H₂O₂ were found to be 4.0%, 2.8%, 2.4% and 8.7%, respectively. To validate the proposed methods, the scavenging abilities of three standard antioxidative compounds, such as L-ascorbic acid, (±)-α-tocopherol and superoxide dismutase (SOD) were examined for four active oxygen species and compared with those by anelectron spin resonance (ESR) spin-trapping method. In addition, the CL methods were also applied to establish the relationships between the decrease of CL intensity and the structures as well as redox characters of syringic acid, 3-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid. From the obtained results, the scavenging effects to H₂O₂, ?OH, ?O₂ ^? and ¹O₂ of other dihydroxybenzoic acids were also evaluated.     

Chemical modification of nanocrystalline metal oxides: effect of the real structure and surface chemistry on the sensor properties

The relationships between the composition, structure, chemistry of the surface, and sensor properties of nanocomposites SnO₂-M _n O _m (M _n O _m = Fe₂O₃, MoO₃, V₂O₅) obtained by chemical precipitation from solutions were analyzed. The relationships between the elemental and phase composition of the nanocomposites and the effect of the composition on the nanostructure and the acidic and oxidation properties of the nanocomposite surface were considered. The modification of the SnO₂ surface by other oxides makes it possible to control the type and density of the acid sites and the oxidation properties of the surface and to enhance the selectivity of the materials in the detection of various gases. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1086–1105, June, 2008.     

Reactions of O(3P) with secondary C-H bonds of saturated hydrocarbons in nonequilibrium plasmas

The functionalization of three n-alkanes by means of a low-pressure oxygen plasma has been achieved. The plasma was generated by applying a low-Frequency high-voltage glow discharge through an oxygen flow. bit, activated species so produced have been allowed to interact with the surface of each one of the liquid compounds at a time. The hydrocarbon has been cooled down to a temperature low enough so that its vapor pressure is about 20–100 times lower than the O₂ pressure, this heing of the order of 0.1–0.4 torr. Under these conditions the main products of the reactions have been the alcohols, except for the primary ones, and the corresponding ketones. A remarkable result we have arrived at is that for the first time secondary carbon hydrogen bonds have shown to possess different reactivities withO(³P). The latter has proved to he the most relevant active species of the plasma. A discussion is given to explain this novel result under two theoretical bases recently published: (i) a conformational analysis of the hydrocarbons according to molecular mechanics calculations, and (ii) an analysis of properties of the molecules based on calculations with charge distributions derived from 6–31G^* wave functions.     

纺锤形α-Fe2O3粒子的溶液催化合成

以Fe₂(SO₄)₃为原料, 在pH为4～7、微量催化剂Fe^2＋离子及晶体助长剂NaH₂PO₄存在下, 沸腾回流, 短时间可直接成长出纺锤形α-Fe₂O₃超细粒子. 与强迫水解法和水热法比较, 该方法具有操作简单、反应物浓度高、反应条件温和及重现性好等优点. 同时研究了各种因素对产物的轴比及相转化速率的影响.     

纳米固体超强酸SO42-/Fe2O3的制备及其催化合成乙酸乙酯

将Fe₂O₃纳米粉体经一定浓度的H₂SO₄浸泡活化后制成纳米固体超强酸SO₄^2-/Fe₂O₃,将其用于催化合成乙酸乙酯以考察其活性。利用均匀设计分析了超强酸制备过程及酯化反应过程中各因素的影响,研究结果表明较好的制备条件是:H₂SO₄浓度:2.5mol·L^-1;浸泡时间:1h;活化温度:167℃;活化时间:1h,此时获得的固体超强酸SO₄^2-/Fe₂O₃的粒径小于50nm。当催化剂用量为冰乙酸质量的5%,n(乙醇)∶n(冰乙酸)为3∶1,反应3.5h后乙酸的转化率高于80%。该催化剂经H₂SO₄溶液浸泡、活化再生后可重新使用,推断出其酸强度H₀<-14.5。     

Synthesis, structure, and properties of chromium(III) sulfates

Reactions between CrO₃ and 50- are studied at temperatures up to the boiling point of the acid. Depending on the H₂SO₄ concentration and synthesis temperature, Cr₂(SO₄)₃, CrH(SO₄)₂, (H₃O)[Cr(SO₄)₂], Cr₂(SO₄)₃·H₂SO₄·4H₂O (gross formula), and (H₅O₂)[Cr(H₂O)₂(SO₄)₂], are obtained as identified reaction products in addition to the incompletely characterized chromic-sulfuric acid. The Cr^III-based sulfates are characterized by X-ray powder diffraction, thermogravimetric, and magnetic susceptibility measurements. The nuclear and magnetic structures of Cr₂(SO₄)₃ at are determined, the structure type of (H₃O)[Cr(SO₄)₂] is established, and the crystal structure of (H₅O₂)[Cr(H₂O)₂(SO₄)₂] is firmly stipulated. Magnetic susceptibility data suggest that the samples of CrH(SO₄)₂ are in a micro-crystalline rather than in an amorphous state. All Cr^III-based sulfates synthesized in this study appear to undergo paramagnetic-to-antiferromagnetic transitions at around .     

Study of the vibrational spectra of SO2, H2O and D2O using the U(4) algebraic model

Using the U(4) algebraic model, in this work we report a study of the vibrational spectra of SO₂, H₂0¹⁸ and D₂O¹⁶. The inclusion of intermode couplings in algebraic models has been stated to give a deep insight into detailed spectroscopy for these bent XY₂ molecules. Improved set of algebraic parameters has been reported to provide improved RMS deviations for these molecules.     

MnO2 nanozyme induced the chromogenic reactions of ABTS and TMB to visual detection of Fe2+ and Pb2+ ions in water

In this study, we used a simple and rapid colourimetric reaction for visual sensing of Fe²⁺ and Pb²⁺ ions in water by employing nano-MnO₂ as a natural oxidase mimic to respectively catalyse ABTS and TMB in citrate-phosphate buffer solution (C-PBS) at 25°C and pH 3.8. It was found that nano-MnO₂ possessed highly oxidase-mimicking activity with the K_m values of 0.030 and 0.027 toward ABTS and TMB, respectively, indicating TMB had a stronger affinity on nano-MnO₂ than ABTS. Interestingly, the presence of 0.01 mmol·L^?1 Fe²⁺/Pb²⁺ ion was able to significantly down-regulate the activity of MnO₂ nanozyme in nano-MnO₂-mediated ABTS reaction processes (P < 0.01), which mainly due to the strong adsorption of metal ion toward nano-MnO₂ surface via the electrostatic attractions, thus leading to the passivation and inactivation of MnO₂ nanozyme catalytic activity. Thereinto, Fe²⁺ reacted with multivalent manganese by oxidation-reduction, while Pb²⁺ was specifically adsorbed onto the surface of MnO₂ nanozyme and formed complexes. Notably, only Fe²⁺ ion inhibited the activity of MnO₂ nanozyme-TMB with a detection limit as low as 1.0 μmol·L^?1. In MnO₂ nanozyme-ABTS sensing systems, Fe²⁺ and Pb²⁺ ions detection limit of 0.5 and 2.0 μmol·L^?1 were, respectively, achieved with a linear response range of 0–0.02 and 0–0.8 mmol·L^?1, implying the developed MnO₂ nanozyme-ABTS sensor was potentially applicable for the visual determination of Fe²⁺ and Pb²⁺ ions in water. In the real water samples, MnO₂ nanozyme-ABTS achieved high accuracy (relative errors: 3.4?10.5%) and recovery (96?110%) for respective detection of Fe²⁺ and Pb²⁺ ions. The simple and rapid MnO₂ nanozyme-ABTS sensing systems might provide a practical assay for visual detection of Fe²⁺ and Pb²⁺ ions in the environmental water samples.     

A study of the compounds present in the three-component system Dy2O3-SeO2-H2O at 100°C

The solubility isotherm of the system Dy₂O₃-SeO₂-H₂O at 100°C was studied and drawn. The selenites present in the system were identified and isolated. A thorough TG, DTG and DTA analysis was made. By modelling the conditions of TG, DTG and DTA analysis, the phases of the thermal decomposition were isolated and identified. The chemistry of the reaction was described.     

Predicting skin permeability from complex chemical mixtures: incorporation of an expanded QSAR model

Quantitative structure–activity relationship (QSAR) models have been widely used to study the permeability of chemicals or solutes through skin. Among the various QSAR models, Abraham’s linear free-energy relationship (LFER) model is often employed. However, when the experimental conditions are complex, it is not always appropriate to use Abraham’s LFER model with a single set of regression coefficients. In this paper, we propose an expanded model in which one set of partial slopes is defined for each experimental condition, where conditions are defined according to solvent: water, synthetic oil, semi-synthetic oil, or soluble oil. This model not only accounts for experimental conditions but also improves the ability to conduct rigorous hypothesis testing. To more adequately evaluate the predictive power of the QSAR model, we modified the usual leave-one-out internal validation strategy to employ a leave-one-solute-out strategy and accordingly adjust the Q² _LOO statistic. Skin permeability was shown to have the rank order: water > synthetic > semi-synthetic > soluble oil. In addition, fitted relationships between permeability and solute characteristics differ according to solvents. We demonstrated that the expanded model (r² = 0.70) improved both the model fit and the predictive power when compared with the simple model (r² = 0.21).     

The fabrication of a nanoscale polyoxometalate based magnetic adsorbent and its selective adsorption on cationic dyes

Amino group-functionalized Fe₃O₄ is loaded on a coordination complex-modified polyoxometalate nanoparticle. In this composite material, Fe₃O₄ and coordination complex-modified polyoxometalate are connected with intense hydrogen bonds as suggested by FTIR. This composite material exhibits excellent methylene blue (MB) adsorption, with adsorption capacity of 175.5 mg g^?1. It also possesses selective separation ability between cationic and anionic dye molecules. In binary solution of MB and methyl orange (MO), MB adsorption efficiency reaches 75%, but it exhibits almost no effect on the adsorption of methyl orange. The saturation magnetization value of this composite material is 18.89 emu g^?1, allowing magnetic separation, which facilitates the recycle and reuse of this composite adsorbent.