The geometry, vibrational frequencies, thermochemistry, quadrupole moments and electronic structure of C2Na2: Comparison with C2Li2, C2H2, C2F2 and C2Cl2

The electronic structure of Na₂C₂ is studied using ab initio electronic structure methods and is compared to the companion molecule Li₂C₂. Both the linear D_∞h and planar structures are minima on the ground state potential surface with the planar D_2h conformation being the lowest energy form, similar to Li₂C₂. At the CCSD(t) level the planar form is more stable that the linear by 11.2 kcal/mol as compared with 7.34 kcal/mol for Li₂C₂. Both molecules are significantly ionic. The vibrational frequencies, atomization energy at 0 K, D₀, and the standard enthalpy of formation, are calculated and compared to those of Li₂C₂ as well as HCCH, FCCF and ClCCCl. We find D₀ and to be 331.1 and 84.92 kcal/mol for Li₂C₂ and 298.3 and 93.25 kcal/mol for Na₂C₂. We calibrate these by calculating the same quantities for HCCH, FCCF and ClCCCl.     

Solid state photodecomposition studies of K4Ti(O2)4·2H2O, K3Ta(O2)2F4 and K2V2O3(O2)2F2

The compounds K₄Ti(O₂)₄·2H₂O, K₃Ta(O₂)₂F₄ and K₂V₂O₃(O₂)₂F₂ undergo photolysis in the solid state. The photolysis kinetics obey the parabolic rate equation p = kt^1/2 and indicate a monoexcitation process for the photolysis. These features are similar to those reported previously for peroxo complexes. The mechanism of evolution of oxygen reported earlier appears to be the same in all these solids.     

低阶煤半焦利用热重在O2/CO2、O2/N2和O2/Ar气氛下燃烧特性研究

利用热重研究了两种中国西北典型低阶煤半焦的燃烧特性。探究了不同气氛（O₂/CO₂、O₂/N₂和O₂/Ar）和不同氧气浓度对其燃烧特性的影响。实验结果表明,无论是反应气氛还是氧气浓度都会对低阶煤半焦的燃烧产生影响。相比于N₂和Ar,CO₂明显有利于燃烧反应进行：当反应气氛由O₂/CO₂变为O₂/Ar时,两种不同低阶煤半焦的燃尽温度分别升高了63.7和68.8℃;而当反应气氛由O₂/CO₂变为O₂/N₂时,两种不同低阶煤半焦的燃尽温度分别升高了135.9和129.6℃。在研究范围内,氧气浓度的提高也能明显提高半焦的燃烧性能。与此同时,半焦燃烧特性的动力学分析表明,随着氧气浓度提高,两种半焦燃烧反应的表观活化能E和指前因子A均呈增大趋势。通过对E和A两者关系的分析结果表明,半焦富氧燃烧的活化能和指前因子存在动力学补偿效应。     

A theoretical study of the reaction of SiH2 with C2H2 and C2D2

Potential energy surfaces of the reaction of SiH₂ and C₂H₂ (and C₂D₂) have been calculated by means of ab initio molecular orbital theory at the QCISD/6-311G++(2df, 2p)//MP2/6-31G(d, p) level with corrections for the triple excitations to the QCISD energies. The barrier heights for the two reaction channels of the adduct, thus calculated, were further utilized for the dynamical calculation of the rate constants in the framework of quantum statistical Rice-Ramsperger-Kassel theory. Contributions of the rate constants of the various pathways to the total rate constant (K_T) for the disappearance of the reactants are critically examined and compared with experiment. The pressure dependence of K_T(C₂H₂) is primarily due to the formation of silirene. K_T(C₂D₂) is consistently higher than K_T(C₂H₂). The standard heat of formation of silirene is predicted to be 72.1 ± 3 kcal/mol. Rearrangement of silirene to vinylsilylene requires an activation energy smaller than that to silylacetylene.     

Some further studies of estertin compounds. crystal structures of [NEt4][MeO2CCH2CH2Sn(dmio)2] (dmio = 1,3-dithiole-2-one-4,5-dithiolato) and (MeO2CCH2CH2)2SnX2[X2 = I2, (NCS)2 or Cl, Br]

Estertn compounds, (MeO₂CCH₂CH₂)₂SnX₂ [X₂ = I₂ (2); X₂ = Br₂ (9); X₂ = Cl, Br (4)) or X₂ = (NCS)₂ (3)] have been obtained by halide exchange reactions of (MeO₂CCH₂CH₂)₂SnCl₂. Crystal structure determinations of 2–4 revealed chelating MeO₂CCH₂CH₂ units with distorted octahedral geometries at tin. The Sn---O bond lengths in the isothiocyanato complex, 3, are shorter [2.390(11) to 2.498(12), mean 2.439 Å], with the chelate bite angles, C---Sn---O, larger [74.3(7) to 78.2(6), mean 76.0°] than those in the halide analogues 2 and 4 [Sn---O = 2.519(2) to 2.541(8), mean 2.530 Å; C---Sn---O 72.8(3) to 73.9(4), mean 73.3°]. ¹H, ¹³C and ¹¹⁹Sn NMR and IR spectra of 2–4 and 9 were determined in CDCl₃ solution: the NMR spectra of (MeO₂CCH₂CH₂)₂SnX₂ show the following trends: (i) both δ¹H and δ¹³C, increase and (ii) both ²J (Sn---H) and ¹J(Sn---C) decrease in the sequence X₂ = (NCS)₂, Cl₂, ClBr, Br₂ and I₂. The MeO₂CCH₂CH₂ and dmio groups (dmio = 1,3-dithiole-2-one-4,5-dithiolato) are all chelating groups in (MeO₂CCH₂CH₂)₂Sn(dmio) (5). As shown by X-ray crystallography, the tin atom in the anion of solid [Q][MeO₂CCH₂CH₂Sn(dmio)₂] 6 (Q = NEt₄) forms 5 strong bonds [to C and the 4 thiolato S atoms, Sn---S 2.459(2) to 2.559(2) Å], arranged in a near trigonal bipyramidal array. There is an additional Intramolecular but weaker, interaction with the carbonyl oxygen atom [Sn---O = 3.111(5) Å]; v(C=O) = 1714 cm⁻¹ in solid 6 (Q = NEt₄). NMR spectra of 5 and 6 are also reported.     

Conversion of NO in NO/N2, NO/O2/N2, NO/C2H4/N2 and NO/C2H4/O2/N2 Systems by Dielectric Barrier Discharge Plasmas

An experimental study on the conversion of NO in the NO/N₂, NO/O₂/N₂, NO/C₂H₄/N₂ and NO/C₂H₄/O₂/N₂ systems has been carried out using dielectric barrier discharge (DBD) plasmas at atmospheric pressure. In the NO/N₂ system, NO decomposition to N₂ and O₂ is the dominating reaction; NO conversion to NO₂ is less significant. O₂ produced from NO decomposition was detected by an on-line mass spectrometer. With the increase of NO initial concentration, the concentration of O₂ produced decreases at 298 K, but slightly increases at 523 K. In the NO/O₂/N₂ system, NO is mainly oxidized to NO₂, but NO conversion becomes very low at 523 K and over 1.6% of O₂. In the NO/C₂H₄/N₂ system, NO is reduced to N₂ with about the same NO conversion as that in the NO/N₂ system but without NO₂ formation. In the NO/C₂H₄/O₂/N₂ system, the oxidation of NO to NO₂ is dramatically promoted. At 523 K, with the increase of the energy density, NO conversion increases rapidly first, and then almost stabilizes at 93–91% of NO conversion with 61–55% of NO₂ selectivity in the energy density range of 317–550 J L⁻¹. It finally decreases gradually at high energy density. A negligible amount of N₂O is formed in the above four systems. Of the four systems studied, NO conversion and NO₂ selectivity of the NO/C₂H₄/O₂/N₂ system are the highest, and NO/O₂/C₂H₄/N₂ system has the lowest electrical energy consumption per NO molecule converted.     

H2O2-responsive theranostic nanomedicine

This review summarizes and discusses the very-recent developments of H₂O₂-responsive theranostic nanoplatforms for versatile biomedical applications, including diagnostic imaging, attenuating tumor hypoxia, enhancing the therapeutic effi ciency of photodynamic therapy/radiation therapy/chemotherapy and theranostic of inflammation/diabetic. It is highly believed that H₂O₂-responsive theranostic nanomedicine will be extensively developed a new specifi c and effi cient theranostic modality to benefi t the personalized biomedicine in the near future.     

TiO2/UV/O2和TiO2/UV/N2体系降解水中对氯硝基苯

以商用TiO₂P25为催化剂,分别在TiO₂/UV/O₂和TiO₂/UV/N₂两种体系下进行降解对氯硝基苯(pCNB)试验.采用ESR对两种体系下光催化反应形成的·OH进行测定,利用LC-MS对两种体系下反应形成的中间产物进行了定性和定量分析,最后对pCNB降解过程中氯和硝基的存在形式进行了研究.结果表明:TiO₂/UV/O₂体系的催化降解效果要明显优于TiO₂/UV/N₂体系;两种反应体系都有·OH产生,并且TiO₂/UV/O₂体系产生的·OH的量多于TiO₂/UV/N₂体系产生的·OH的量;TiO₂/UV/O₂体系形成的中间产物的种类要多于TiO₂/UV/N₂体系形成的,苯环上的氢、氯、硝基均可被·OH取代形成对硝基酚(pNP)、5-氯-2-硝基酚(5-C-2-PN)等酚类物质;两种体系下均有Cl^-和NO₂^-存在,其中Cl^-生成势与pCNB的去除势一致,只有TiO₂/UV/O₂体系中存在NO₃^-.     

The pure rotational Raman spectra of cyanogen, C2N2 and C2N2

The pure rotational Raman spectra of C₂¹⁴N₂ and C₂¹⁵N₂ have been recorded photographically using a 3-metre spectrograph with a reciprocal linear dispersion of 1.4 cm⁻¹ mm⁻¹ at 488.0 nm and analysed to give the rotational and centrifugal distortion constants for both species. Corrections were applied to compensate for the effect of molecules in excited vibrational states on the pure rotational spectra. Comparisons are made with previous infrared vibration—rotational studies on these species and with previous Raman studies on C₂¹⁴N₂. The following bond lengths were calculated: r₀(C---N) = 116 ± 1 pm; r₀(C---C) = 138 ± 2 pm.     

Estimating the limiting reducing power of SmI2/H2O/amine and YbI2/H2O/amine by efficient reduction of unsaturated hydrocarbons

The mixture of samarium diiodide, amine, and water (SmI2/H2O/Et3N) is known to be a particularly powerful reductant, but until now the limiting reducing power has not been determined. A series of unsaturated hydrocarbons with varying half-wave reduction potentials (E(1/2) = -1.6 to -3.4 V, vs SCE) have been treated with SmI2/H2O/Et3N and YbI2/H2O/Et3N, respectively. All hydrocarbons with potentials of -2.8 V or more positive were readily reduced with SmI2/H2O/Et3N, whereas all hydrocarbons with potentials of -2.3 V or more positive were readily reduced using YbI2/H2O/Et3N. This defines limiting values of the chemical reducing power of SmI2/H2O/Et3N to -2.8 V and of YbI2/H2O/Et3N to -2.3 V vs SCE.     

Study of plasma-polymerization deposition of C2H2/CO2/H2 onto ethylene-co-propylene rubber membranes

Ethylene-co-propylene rubber (ERP) membranes were modified by use of acetylene/carbon dioxide/hydrogen (C₂H₂/CO₂/H₂) plasma-polymerization deposition. The influence of flow rate of gases, glow discharge power and deposition time on the amount of deposition was investigated. Infrared spectroscopy and scanning electron microscopy were employed to study the structure and surface morphology of the deposited EPR membrane. The water contact angle and the permeation property were examined as well. The results showed that deposition comprises oxygen-containing groups including >C=O and –OH, the hydrophilicity of EPR membrane was therefore improved. It was also found that the permeation coefficient of plasma modified EPR membrane decreased with the increase of the amount of deposition.     

Density functional theory study on the structural and electronic properties of low index rutile surfaces for TiO2/SnO2/TiO2 and SnO2/TiO2/SnO2 composite systems

The present study is concerned with the structural and electronic properties of the TiO2/SnO2/TiO2 and SnO2/TiO2/SnO2 composite systems. Periodic quantum mechanical method with density functional theory at the B3LYP level has been carried out. Relaxed surface energies, structural characteristics and electronic properties of the (110), (010), (101) and (00) low-index rutile surfaces for TiO2/SnO2/TiO2 and SnO2/TiO2/SnO2 models are studied. For comparison purposes, the bare rutile TiO2 and SnO2 structures are also analyzed and compared with previous theoretical and experimental data. The calculated surface energy for both rutile TiO2 and SnO2 surfaces follows the sequence (110) < (010) < (101) < (001) and the energy increases as (010) < (101) < (110) < (001) and (010) approximately = (110) < (101) < (001) for SnO2/TiO2/SnO2 and TiO2/SnO2/TiO2 composite systems, respectively. SnO2/TiO2/SnO2 presents larger values of surface energy than the individual SnO2 and TiO2 metal oxides and the TiO2/SnO2/TiO2 system renders surface energy values of the same order that the TiO2 and lower than the SnO2. An analysis of the electronic structure of the TiO2/SnO2/TiO2 and SnO2/TiO2/SnO2 systems shows that the main characteristics of the upper part of the valence bands for all the studied surfaces are dominated by the external layers, i.e., by the TiO2 and the SnO2, respectively, and the topology of the lower part of the conduction bands looks like the core layers. There is an energy stabilization of both valence band top and conduction band bottom for (110) and (010) surfaces of the SnO2/TiO2/SnO2 composite system in relation to their core TiO2, whereas an opposite trend is found for the same surfaces of the TiO2/SnO2/TiO2 composite system in relation to the bare SnO2. The present theoretical results may explain the growth of TiO2@SnO2 bimorph composite nanotape.     

双酸体系下有序介孔SO42-/ZrO2-SiO2材料的合成

采用一锅合成法通过调变自组装过程中硫酸和盐酸的体积比,成功制备了系列介孔SO₄^2-/ZrO₂-SiO₂固体酸材料(Zr/Si物质的量为1.1).XRD、UV-Vis DRS、HR-TEM等表征结果表明,所得材料均具有高度有序的二维介孔结构及四方相氧化锆的晶体结构.氮吸附和FT-IR表征结果进一步发现,通过改变硫酸/盐酸体积比可有效调变材料比表面积、孔容、孔径及表面L酸与B酸的相对强度.与纯硅介孔分子筛SBA-15不同,此系列SO₄^2-/ZrO₂-SiO₂固体酸材料均在正戊烷的异构化反应中表现出较高的催化活性和稳定性.其原因在于,在合成过程中硫酸的加入不仅促使了酸基的形成,而且稳定了催化剂的晶体结构;盐酸的存在则保持了有序的介孔结构.由此可见,混酸合成体系有望制备出结构有序、酸性可调、催化性能优越的新型催化材料,并在众多酸催化反应中取得应用.     

改性固体超强酸S2O82-/ZrO2-CoO用于FCC汽油氧化脱硫的研究

以硝酸锆、硝酸铜和硝酸钴为金属源,过硫酸铵作为浸渍液,采用共沉淀浸渍法合成出固体超强酸催化剂S₂O₈^2-/ZrO₂、S₂O₈^2-/ZrO₂-CuO和S₂O₈^2-/ZrO₂-CoO,通过XRD、FT-IR、NH₃-TPD、BET对催化剂进行表征。结果表明,Co（钴）改性催化剂S₂O₈^2-/ZrO₂-CoO在三种催化剂中超强酸位最多。将其作为催化剂,过氧化氢作为氧化剂用于FCC汽油氧化脱硫反应,研究不同反应温度、催化剂用量、反应时间、氧化剂用量对FCC汽油脱硫效果的影响。结果表明,FCC汽油氧化脱硫的最佳条件为：反应温度70 ℃,反应1.5 h,FCC汽油加入量与氧化剂体积比7.5：1,催化剂用量0.02 g/mL。反应产物利用N,N-二甲基甲酰胺进行萃取分离,萃取剂/汽油体积比为1：1时,FCC汽油脱硫率最高可达85.34%,回收率为94.45%,并且催化剂表现出较为稳定的催化活性。     

THE STUDY OF LUMINOL-H_2O_2-IO_4~--S~(2-)CHEMILUMINESCENCE SYSTEM AND ITS APPLICATION

This paper reports a new chemiluminescence system i.e.luminol-H_2O_2-IO_4~- catalyzed by sulphide ion(S~(2-)).Based on this catalysis,a newchemiluminescence(CL)method for the determination of trace S~(2-)is pro-posed.The detection limit is 0.2μg/LS~(2-),the linear dynamic range is 5μgto 100βμg/L S~(2-)and the variation coefficient at an sulphide concentrationof 100μg/L S~(2-)is 4.5%(n=10).The method has been satisfactory applied tothe determination of trace sulphide ion in water.     

Flow reactor studies and kinetic modeling of the H2/O2/NOX and CO/H2O/O2/NOX reactions

Flow reactor experiments were performed over wide ranges of pressure (0.5–14.0 atm) and temperature (750–1100 K) to study H₂/O₂ and CO/H₂O/O₂ kinetics in the presence of trace quantities of NO and NO₂. The promoting and inhibiting effects of NO reported previously at near atmospheric pressures extend throughout the range of pressures explored in the present study. At conditions where the recombination reaction H + O₂ (+M) = HO₂ (+M) is favored over the competing branching reaction, low concentrations of NO promote H₂ and CO oxidation by converting HO₂ to OH. In high concentrations, NO can also inhibit oxidative processes by catalyzing the recombination of radicals. The experimental data show that the overall effects of NO addition on fuel consumption and conversion of NO to NO₂ depend strongly on pressure and stoichiometry. The addition of NO₂ was also found to promote H₂ and CO oxidation but only at conditions where the reacting mixture first promoted the conversion of NO₂ to NO. Experimentally measured profiles of H₂, CO, CO₂, NO, NO₂, O₂, H₂O, and temperature were used to constrain the development of a detailed kinetic mechanism consistent with the previously studied H₂/O₂, CO/H₂O/O₂, H₂/NO₂, and CO/H₂O/N₂O systems. Model predictions generated using the reaction mechanism presented here are in good agreement with the experimental data over the entire range of conditions explored. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 705–724, 1999     

Synthesis and structural behavior of the P-functional organotin chlorides [Ph2P(CH2)3]2SnCl2, Ph2P(CH2)3SnCl2Me, and Ph2P(CH2)nSnCl3 (n=2, 3)

The P-functional organotin dichloride [Ph₂P(CH₂)₃]₂SnCl₂ (3) is synthesized by reaction of Ph₂P(CH₂)₃MgCl with SnCl₄ independently of the molar ratio of the starting compounds. The corresponding organotin trichlorides Ph₂P(CH₂)_nSnCl₂R (4: n=2, R=Cl; 5: n=3, R=Cl; 6: n=3, R=Me) are formed in a cleavage reaction of Ph₂P(CH₂)_nSnCy₃ (n=2, 3) with SnCl₄ or MeSnCl₃, respectively. The main features of the crystal structures of 3–6 are both intra- and intermolecular PSn coordinations and the existence of intermolecular Sn---ClSn bridges. For further characterization of the title compounds, the adducts 4(Ph₃PO)₂ (7) and 5(Ph₃PO) (8), as well as the P-oxides and P-sulfides of 3–6 (9–15), are synthesized. The results of crystal structure analyses of 7, 11, 12, and 14 are reported. The structures of 9–15 are characterized by intramolecular P=XSn interactions (X=O, S). A first insight into the structural behavior of the compounds 3–15 in solution is discussed on the basis of multinuclear NMR data.     

含氟CaO-P2O5-SiO2-Na2O-B2O3玻璃陶瓷的制备及性能表征

采用溶胶-凝胶法制备CaO-P₂O₅-SiO₂-Na₂O-B₂O₃体系前驱体粉末,用CaF₂替代部分CaO再次制备前驱体粉末。 通过TG-DSC分析确定结晶温度为865 ℃,经过热处理获得主晶相为Na₆Ca₃Si₆O₁₈的玻璃陶瓷。 通过X射线衍射(XRD)、傅里叶红外光谱(FTIR)、扫描电子显微镜(SEM)等技术手段及体外生物活性实验分析玻璃陶瓷的显微结构及性能。 结果表明,CaF₂的加入能提高玻璃陶瓷的体积密度、抗折强度和弹性模量,并且不会破坏玻璃陶瓷的生物活性。     

Syntheses and characterizations of complex perovskite oxynitrides LaMg1/3Ta2/3O2N, LaMg1/2Ta1/2O5/2N1/2, and BaSc0.05Ta0.95O2.1N0.9

The following complex oxynitride perovskites have been prepared: LaMg_1/3Ta_2/3O₂N, LaMg_1/2Ta_1/2O_5/2N_1/2, and BaSc_0.05Ta_0.95O_2.1N_0.9. Synchrotron X-ray powder diffraction analyses show that LaMg_1/3Ta_2/3O₂N and LaMg_1/2Ta_1/2O_5/2N_1/2 are isostructural to the oxide La₂Mg(Mg_1/3Ta_2/3)O₆ (space group P2₁/n), whereas BaSc_0.05Ta_0.95O_2.1N_0.9 has a simple cubic symmetry similarly to BaTaO₂N. The orderings of octahedral cations are markedly diminished in the above oxynitrides, as compared with the related oxides such as La₂Mg(Mg_1/3Ta_2/3)O₆ and Ba₂ScTaO₆. The optical band gaps are similar for the homologous compositions, LaMg_1/3Ta_2/3O₂N, LaMg_1/2Ta_1/2O_5/2N_1/2 and LaTaON₂ (1.9 eV), and BaSc_0.05Ta_0.95O_2.1N_0.9 and BaTaO₂N (1.8 eV), while the absorption edges become broader for the complex derivatives. As revealed from the impedance spectroscopic analysis, the oxynitrides have clearly different dielectric components from those of comparable oxides containing Ta⁵⁺. Impedance spectroscopy reveals interesting capacitor geometry in BaSc_0.05Ta_0.95O_2.1N_0.9 in which the semiconducting oxynitride grains are separated by insulating secondary phases. Most notably BaSc_0.05Ta_0.95O_2.1N_0.9 has a bulk component with a high relative permittivity (κ=7300) and the grain boundary component with an even higher κ.