用密度泛函方法研究质子化苯基丙酮-水团簇

The structure and growth trend of the protonated acetophenone-water clusters have been investigated using the DFT-B3LYP method combined with the standard 6-31+G(d,p) basis set. In order to obtain more accurate single-point energy the B3LYP/6-311++G(3df,2p) method was adapted. The results show that the formation of H+C8H8O-H2O is a barrierless reaction process and the equilibrium distance between the proton and the O atom in C8H8O molecule is 1.015 A. For H+C8H8O-(H2O)n(n=1,2,3) clusters, the proton lies between the acetophenone molecule C8H8O and the water molecule H2O. The distance between the proton and the O atom of the C8H8O molecule increased from n=1 to n=3; C8H8O-H+-H2O can be regarded as an solvation shell. For H+C8H8O (H2O)n (n=4,5,6,7,8) clusters, the proton lies between the two H2O molecules forming a H5O2+ structure, C8H8O-H5O2+ is an important structure, which the other H2O molecules will attack from different sides.     

多晶Fe60Ni40合金阳极钝化膜的XPS研究

过渡金属Fe、Ni或其合金由于它们具有磁性和在工业上被用作催化剂等，它们与氧化腐蚀性气体02、C12等的作用已被广泛研究［‘－3］．含Ni的不锈钢和含Ni50％的FeNi基合金在酸性溶液中表现出比铁更好的耐腐蚀性并增强了氧化钝化层的附着力，放它们在溶液的腐蚀与钝性研究已引起广泛的兴趣，甚至包括对F6Ni基非晶合全玻璃的腐蚀与钝性研究【4一刊，用不同的方法研究溶液状态下的自然氧化膜或阳极钝化膜，得出的结果不同，对腐蚀与钝性解释也很不一致，硼酸一础砂或磷酸一磷酸盐缓冲液在工业上被广泛用作清洗剂、缓蚀剂或成膜剂等·因此，…     

Formation of crystalline Na2V6O16·3H2O ribbons into belts and rings

Single-crystalline nanobelts and nanorings of Na(2)V(6)O(16)·3H(2)O structures have been facilely synthesized through a direct hydrothermal reaction between NaVO(3) and H(3)PO(4), without the addition of any harmful solvents or surfactants. The analytical techniques of scanning electron microscopy, transmission electron microscopy (TEM), powder X-ray diffraction, thermogravimetric analysis, energy-dispersive X-ray spectroscopy, Fourier transform infrared, high-resolution TEM, and selected-area electron diffraction have been used to characterize the morphology, composition, and structure of the synthesized products. The Na(2)V(6)O(16)·3H(2)O nanobelts are up to several hundreds of micrometers in length and 100-300 nm in thickness, and for nanorings, the diameters are 4.5-6.5 μm. H(3)PO(4) plays a key role in maintaining the pH of the solution as well as producing PO(4)(3-) ions in solution. The chemical reactions and a possible growth mechanism involved in the formation of Na(2)V(6)O(16)·3H(2)O nanobelts and nanorings are briefly discussed.     

CsxH3-xPW12O40的孔结构

Ｎ２静态吸附容量法的测定结果表明，磷钨酸铯盐（ＣｓｘＨ３－ｘＰＷ１２Ｏ４０）的孔窝和孔分布与ｘ值的大小相关。ｘ〈１．５的ＣｓｘＨ３－ｘＰＷ１２Ｏ４０孔容相近，孔分布近似；当ｘ〉１．５时，ＣｓｘＨ３－ｘＰＷ１２Ｏ４０的孔主要是孔径小于１０ｎｍ的中孔和微孔，平均孔径及孔容随ｘ的增加而增大。ＳＥＭ和ＴＥＭ的观测结果表明，ＣｓｘＨ３－ｘＰＷ１２Ｏ４０的孔是微细粒子堆积留下的空隙孔，可能不存在晶内孔。     

Effect of formic acid addition on water cluster stability and structure

Computational chemistry simulations were performed to determine the effect that the addition of a single formic acid molecule has on the structure and stability of protonated water clusters. Previous experimental studies showed that addition of formic acid to protonated pure water results in higher intensities of large-sized clusters when compared to pure water and methanol-water mixed clusters. For larger, protonated clusters, molecular dynamics simulations were performed on H(+)(H(2)O)(n), H(+)(H(2)O)(n)CH(3)OH, and H(+)(H(2)O)(n)CHOOH clusters, 19-28 molecules in size, using a reactive force field (ReaxFF). Based on these computations, formic acid-water clusters were found to have significantly higher binding energies per molecule. Addition of formic acid to a water cluster was found to alter the structure of the hydrogen-bonding network, creating selective sites within the cluster, enabling the formation of new hydrogen bonds, and increasing both the stability of the cluster and its rate of growth.     

Single-walled carbon nanotube growth using [Fe(3)(mu(3)-O)(mu-O(2)CR)(6)(L)(3)](n+) complexes as catalyst precursors

We present herein the VLS growth of SWNTs from oxo-hexacarboxylate-triron precursors, [Fe(3)O(O(2)CCH(3))(6)(EtOH)(3)] and [Fe(3)O(O(2)CCH(2)OMe)(6)(H(2)O)(3)][FeCl(4)], on spin-on-glass surfaces, using C(2)H(4)/H(2) (750 degrees C) and CH(4)/H(2) (800 and 900 degrees C) growth conditions. The SWNTs have been characterized by AFM, SEM and Raman spectroscopy. The characteristics of the SWNTs are found to be independent of the identity of the precursor complex or the solvent from which it is spin-coated. The as grown SWNTs show a low level of side-wall defects and have an average diameter of 1.2-1.4 nm with a narrow distribution of diameters. At 750 and 800 degrees C the SWNTs are grown with a range of lengths (300 nm-9 microm), but at 900 degrees C only the longer SWNTs are observed (6-8 microm). The yield of SWNTs per unit area of catalyst nanoparticle decreases with the growth temperature. We have demonstrated that spin coating of molecular precursors allows for the formation of catalyst nanoparticles suitable for growth of SWNTs with a high degree of uniformity in the diameter, without the formation of preformed clusters of a set diameter.     

H2O nucleation around Au+

First principles electronic structure calculations have been carried out to investigate the ground state geometry, electronic structure, and the binding energy of [Au(H2O)n]+ clusters containing up to 10 H2O molecules. It is shown that the first coordination shell of Au+ contains two H2O molecules forming a H2O-Au+-H2O structure with C2 symmetry. Subsequent H2O molecules bind to the previous H2O molecules forming stable and fairly rigid rings, each composed of 4 H2O molecules, and leading to a dumbbell structure at [Au(H2O)8]+. The 9th and the 10th H2O molecules occupy locations above the Au+ cation mainly bonded to one H2O from each ring, leading to structures where the side rings are partially distorted and forming structures that resemble droplet formation around the Au+ cation. The investigations highlight quantum effects in nucleation at small sizes and provide a microscopic understanding of the observed incremental binding energy deduced from collision induced dissociation that indicates that [Au(H2O)n]+ clusters with 7-10 H2O molecules have comparable binding energy. The charge on the Au+ is shown to migrate to the outside H2O molecules, suggesting an interesting screening phenomenon.     

Revealing the mechanisms behind SnO2 nanoparticle formation and growth during hydrothermal synthesis: an in situ total scattering study

The formation and growth mechanisms in the hydrothermal synthesis of SnO(2) nanoparticles from aqueous solutions of SnCl(4)·5H(2)O have been elucidated by means of in situ X-ray total scattering (PDF) measurements. The analysis of the data reveals that when the tin(IV) chloride precursor is dissolved, chloride ions and water coordinate octahedrally to tin(IV), forming aquachlorotin(IV) complexes of the form [SnCl(x)(H(2)O)(6-x)]((4-x)+) as well as hexaaquatin(IV) complexes [Sn(H(2)O)(6-y)(OH)(y)]((4-y)+). Upon heating, ellipsoidal SnO(2) nanoparticles are formed uniquely from hexaaquatin(IV). The nanoparticle size and morphology (aspect ratio) are dependent on both the reaction temperature and the precursor concentration, and particles as small as ~2 nm can be synthesized. Analysis of the growth curves shows that Ostwald ripening only takes place above 200 °C, and in general the growth is limited by diffusion of precursor species to the growing particle. The c-parameter in the tetragonal lattice is observed to expand up to 0.5% for particle sizes down to 2-3 nm as compared to the bulk value. SnO(2) nanoparticles below 3-4 nm do not form in the bulk rutile structure, but as an orthorhombic structural modification, which previously has only been reported at pressures above 5 GPa. Thus, adjustment of the synthesis temperature and precursor concentration not only allows control over nanoparticle size and morphology but also the structure.     

Theoretical and experimental study of the interaction of O2 and H2O with metallic zinc--discussion of the initial step of oxide formation

The steps of Zn corrosion and ZnO formation using dry O2 or O2/water atmosphere were investigated in situ using an experimental and theoretical approach. The adsorption equilibrium and kinetics of O2/H2O on Zn have been measured at different temperatures and relative humidities using a Cahn 1000 vacuum recording electrobalance. The amounts adsorbed on Zn are different in the presence or absence of O2. SEM-EDAX, XPS, and XRD studies have been performed at the surface for different times of reaction. A theoretical study using the extended Hückel method has been done for the adsorption/reaction of H2O/O2 on Zn and on ZnO. A coherent explanation is presented for the initial steps of ZnO formation on Zn, for the steady state found for the ZnO growth, and for the experimental findings of the methods cited above.     

Concerning the reaction between singlet nitrenium ions and water: a computational investigation on competitive reaction paths

The reaction between singlet nitrenium ions XNH(+) (X = F and Cl) and H(2)O has been investigated by high-level of theory ab initio calculations. The geometries of the involved intermediates, transition structures, and dissociation products have been optimized at the MP2(full)/6-31G(d) level of theory, and accurate total energies have been obtained using the Gaussian-3 (G3) procedure. The reaction commences by the exothermic formation of the F-NH-OH(2) (+) and Cl-NH-OH(2) (+) intermediates, which are in turn able to undergo two distinct low-energy reaction paths, namely, the isomerization to the N-protonated isomers of the hydroxylamines F-NH-OH or Cl-NH-OH, and the eventual extrusion of HF or HCl. The competitive or alternative occurrence of these two processes strictly depends on the nature of the substituent X. In the reaction between FNH(+) and H(2)O, the energy gained in the formation of the complex F-NH-OH(2) (+) from the association between FNH(+) and H(2)O, 52.1 kcal mol(-1), is by far larger than the activation barrier for the loss of HF from F-NH-OH(2) (+), computed as 24.9 kcal mol(-1). In addition, the F-NH-OH(2) (+) intermediate requires 33.0 kcal mol(-1) to overcome the barrier for the isomerization to F-NH(2)-OH(+). Therefore, the reaction between FNH(+) and H(2)O is expected to occur practically exclusively by HF elimination with formation of the HN-OH(+) ionic product. On the other hand, for the reaction between ClNH(+) and H(2)O, it is not possible to get a definitive conclusion on the competitive or alternative occurrence of the two reaction paths. In fact, the transition structure involved in the elimination of HCl from Cl-NH-OH(2) (+) is only 3.4 kcal mol(-1) lower in energy than the transition structure for the isomerization of Cl-NH-OH(2) (+) to Cl-NH(2)-OH(+). In addition, the absolute values of the energy barriers of these two processes, 24.2 and 27.6 kcal mol(-1), respectively, are comparable with the energy gained in the formation of the complex Cl-NH-OH(2) (+) from the association between ClNH(+) and H(2)O, 24.0 kcal mol(-).1 Therefore, the ClNH(+) cation is predicted to react with water significantly slower than FNH(+).     

Cu,Zn-SOD酶模型配合物催化O2-歧化作用的研究

为了解Cu,Zn-SOD酶中Cu周围环境对催化O_2~-歧化作用活性的影响,本文用NBT法测定了Cu,Zn-SOD酶及一系列咪唑桥异核模型配合物催化O_2~-歧化作用的活性,并用ESR方法鉴测了其中一个配合物与O_2~-作用的中间过程。结果表明,具有平面四方构型或轴向有弱配位H_2O或ClO_4~-基团的四方锥构型的Cu~(2+)配合物具有较高活性,说明配合物催化歧化O_2~-过程中,Cu~(2+)可能首先以轴向与O_2~-配位,形成Cu~(2+)-O_2~-中间化合物,紧接着Cu~(2+)被还原成Cu~+。     

THE EFFECTS OF NEAR-UV RADIATION ON HUMAN LENS β-CRYSTALLINS: PROTEIN STRUCTURAL CHANGES and THE PRODUCTION OF O2_ and H2O2

beta-Crystallins (beta 1-, beta 2- and beta 3-crystallin) comprise nearly half the protein of the human lens. The effect of near-UV radiation, which is one of the possible risk factors in cataract formation, on the beta-crystallins is investigated in this study. Protein intersubunit crosslinking, change in charge of the protein subunits to more acidic species and changes in protein tertiary structure (conformation) by 300 nm irradiation are reported. The fluorescence yield of protein tryptophan residues decreases by 300 nm irradiation. There is an increase in nontryptophan fluorescence (lambda cx 340 nm, lambda cm 400-600 nm), and in protein absorption at 340 nm, due to the formation of tryptophan photooxidation products. Both tryptophan and its oxidation products can be photoexcited by 300 nm irradiation and the latter are known to be good photosensitizers. The results provide evidence for the generation of H2O2 in the irradiated human beta-crystallin solutions by the Type I photosensitizing action of the chromophores absorbing at 300 nm. The H2O2 is generated via the intermediate production of O2 anion; the latter spontaneously dismutates to H2O2, presumably via O2- protein interactions. The amount of H2O2 generated per absorbed photon is compared for various solutions of beta 1-, beta 2- and beta 3-crystallins from human lenses of different age.     

Observations of different core water cluster ions Y-(H2O)n (Y = O2, HOx, NOx, COx) and magic number in atmospheric pressure negative corona discharge mass spectrometry

Reliable mass spectrometry data from large water clusters Y(-)(H(2)O)(n) with various negative core ions Y(-) such as O(2)(-), HO(-), HO(2)(-), NO(2)(-), NO(3)(-), NO(3)(-)(HNO(3))(2), CO(3)(-) and HCO(4)(-) have been obtained using atmospheric pressure negative corona discharge mass spectrometry. All the core Y(-) ions observed were ionic species that play a central role in tropospheric ion chemistry. These mass spectra exhibited discontinuities in ion peak intensity at certain size clusters Y(-)(H(2)O)(m) indicating specific thermochemical stability. Thus, Y(-)(H(2)O)(m) may correspond to the magic number or first hydrated shell in the cluster series Y(-)(H(2)O)(n). The high intensity discontinuity at HO(-)(H(2)O)(3) observed was the first mass spectrometric evidence for the specific stability of HO(-)(H(2)O)(3) as the first hydrated shell which Eigen postulated in 1964. The negative ion water clusters Y(-)(H(2)O)(n) observed in the mass spectra are most likely to be formed via core ion formation in the ambient discharge area (760 torr) and the growth of water clusters by adiabatic expansion in the vacuum region of the mass spectrometers (≈1 torr). The detailed mechanism of the formation of the different core water cluster ions Y(-)(H(2)O)(n) is described.     

Helical poly(3-methyl-4-vinylpyridine)/amino acid complexes: preparation, characterization, and biocompatibility

Helical poly(3-methyl-4-vinylpyridine) (P3M4VP)/amino acid complexes have been prepared via acid-base reaction of the achiral polymer with D and L amino acids: alanine, leucine, valine, serine and phenylalanine. The circular dichroism (CD) spectra of P3M4VP/D- and L-alanine complexes in CH(3)OH/H(2)O show opposing (near mirror image) Cotton effect signals at 278.4, 274.8 and 270.8 nm, indicating the formation of enantiomeric secondary structures. The formation of the enantiomeric structures is supported by observed [alpha](D)(25) values of -3.0 and +3.0 for the P3M4VP/D-alanine and P3M4VP/L-alanine complexes, respectively. The preparation of helical P3M4VP/amino acid complexes has been carried out in CH(3)OH and H(2)O at pH 1.8 and 2.7. The intensities of the Cotton effect signals were good. For example, for the P3M4VP/L-alanine complexes in CH(3)OH/H(2)O and H(2)O (pH 1.8), the second Cotton effect signal around 275-277 nm show [theta;] values of 49 980 and 79 210 deg . cm(2) . dmol(-1), respectively. The formation of the helical secondary structure is rapid. The acid-base reaction between P3M4VP and L-alanine in CH(3)OH/H(2)O, in 10 min, show a CD spectrum with Cotton effect signals at 274 and 272 nm with [theta] values of 27,000 deg . cm(2) . dmol(-1) and -36,000 deg . cm(2) . dmol(-1), respectively. P3M4VP permits ready conformational reorientation on complexation with amino acids, but once the helical P3M4VP/amino acid complexes are formed, it is stable at room temperature. P3M4VP is not compatible with HeLa ovarian cancer cells, but the helical P3M4VP/amino acid complexes are compatible with HeLa cells. The complexes minimally interfere with the adhesion and growth of HeLa cells on complex surfaces. Helical poly(3-methyl-4-vinylpyridine)/D- and L-alanine complexes support the attachment and growth of HeLa cells. The micrographs shows HeLa cells after three days: left panel: on P3M4VP/L-alanine complex; right panel: on P3M4VP/D-alanine complex.     

Speciation in the aqueous H+/H2VO4-/H2O2/picolinate system relevant to diabetes research

A detailed study of the quaternary aqueous H+/H2VO4-/H2O2/picolinate (Pi-) system has been performed at 25 degrees C in 0.150 M Na(Cl) medium using quantitative 51 V NMR (500 MHz) and potentiometric data (glass electrode). In the ternary H+/H2VO4-/Pi- system, six complexes have been found in the pH region 1-10. In the quaternary H+/H2VO4-/H2O2/Pi- system, eight additional complexes have been found. Generally, equilibria are fast in both systems. The rate of peroxide decomposition depends on the species in solution. Chemical shifts, compositions and formation constants for the species are given. Equilibrium conditions and the fit of the model to the experimental data are illustrated in distribution diagrams. Possible formation of mixed ligand species with imidazole, lactic acid and citric acid have been investigated and ruled out under the same experimental conditions. Structural proposals are given, based on 1)C NMR data and available crystal structures.     

Novel coordination polymers and structural systematics in the hydrothermal M,M' trans-3(-3-pyridyl)acrylic acid system

The bifunctional ligand trans-3-(3-pyridyl)acrylic acid has been utilized to promote the formation of a novel hetero-metallic [Cu3(C8H6NO2)6Nd2(NO3)6] (1) and two homometallic: [Nd(C8H6NO2)3H2O] (2) and [Cu(C8H6NO2)2] x H2O (3) metal organic framework (MOF) materials. The philosophy here is that a mixture of hard (Nd3+) and softer metal cations will show preference for the carboxylic and pyridyl functional groups, respectively. As such, a 3-D topology 1 has emerged as a stable, heterometallic structure. Efforts to explore structural systematics in this system have led to the synthesis of homometallic end members and hence the formation of a 2-D coordination polymer 2, and a 1-D coordination polymer 3. Presented is an analysis of the effect of a second metal centre on coordination environment, overall structure formation, thermal and luminescence properties.     

再生气氛对HDN催化剂再生性能的影响

采用不同手段研究了催化剂反应前后及在Ｈ２Ｏ和Ｎ２介质中再生时催化剂性质和表面原子浓度及其颁的变化。ＢＥＴ结果表明，Ｎ２介质中再生，催化剂的孔径基本没有变化，而Ｈ２Ｏ介质中再生的催化剂孔径明显增大，化学组成分析结果说明，长期运转使用后的催化剂在２和Ｈ２Ｏ介质中再生后其活性组分均有少量流失。电子探针的结果表明，结炭后的催化剂活性组分很不均匀，在Ｎ２和Ｈ２Ｏ介质中再生后其分布得到了明显改善，但仍不如新鲜     

Hydrothermal synthesis, crystal structures, and luminescent properties of a series of new lanthanide oxalatophosphonates with a layer architecture

Eleven new lanthanide oxalatophosphonate hybrids with a 2D layered structures, namely, [Ln(H(3)L)(C(2)O(4))]·2H(2)O (Ln = La-Dy, Er and Y, H(4)L = C(6)H(5)CH(2)N(CH(2)PO(3)H(2))(2)), have been synthesized under hydrothermal conditions and structurally characterized by X-ray single-crystal diffraction, X-ray powder diffraction, infrared spectroscopy, elemental analysis and thermogravimetric analysis. Compounds 1-11 are isomorphous and they exhibit a 2D framework structure. Two {LnO(8)} polyhedra and four {CPO(3)} tetrahedra are interconnected into a unit via corner-sharing, and the so-built units are bridged by the oxalate anions into a layer. The result of connections in this manner is the formation of a 24-atom window. The thermal stabilities and guest desorption-sorption properties of compounds 1-11 have been investigated. The luminescent properties of compounds 5, 6, 8 and 9 have also been studied.     

A potentiometric study on oxalate and citrate complexes of tin(II)

The formation of oxalate and citrate complexes of the Sn2+ ion in 1 M Na(ClO4) at 25 degrees C was investigated in the -log[H+] range 2 to 5 by potentiometric titrations using glass and tin amalgam electrodes. The tin concentration was varied from 0.5 to 5 mM and the concentration of the ligands from 1 to 40 mM. The experimental data have been explained by the formation of the oxalato complexes SnC2O4(aq) and Sn(C2O4)2(2-) and of the citrate complexes (C3H5O7(3-) = citrate ion) SnC3H5O7-, SnHC3H5O7(aq), SnH2C3H5O7+ and Sn(OH)C3H5O7(2-). The equilibrium constants were refined by the computer program SUPERQUAD. The final values of the constants on the medium scale and in the infinite dilution reference state are given in Table 2.     

Lamellar and three-dimensional hybrid compounds formed by cyclohexene- and cyclohexanedicarboxylates of Pb, La, and Cd

To establish factors that determine the formation of three-dimensional hybrid structures of metal dicarboxylates involving metal-oxygen-metal linkages, we have investigated metal dicarboxylates derived from 1,2-cyclohexene as well as 1,2-, 1,3-, and 1,4-cyclohexane dicarboxylic acids. Thus, we have synthesized a 1,2-cyclohexenedicarboxylate of Cd, [Cd(1,2-CHeDC)(H2O)] (I), a 1,2-cyclohexanedicarboxylate of Pb, [Pb(1,2-CHDC)] (II), and three 1,4-cyclohexanedicarboxylates of La [La2(1,4-CHDC)3(H2O)4] (III), [La3(1,4-HCHDC)2(1,4-CHDC)5(H2O)2].H2O (IV) and [La2(1,4-CHDC)3(H2O)].2.5 H2O (V) under hydrothermal conditions and determined their structures. A mixed dicarboxylate involving both 1,3- and 1,4-cyclohexenedicarboxylates of Pb, [Pb3O(1,3-CHDC)(1,4-CHDC)].0.5 H2O (VI) and a 1,4-cyclohexanedicarboxylate of Pb, [Pb(6)O(2)(1,4-CHDC)3(1,4-HCHDC)2], have also been synthesized and characterized. While the 1,2-dicarboxylates have layered structures, the 1,4-dicarboxylates and the mixed dicarboxylates possess three-dimensional structures. Interestingly, both the 1,2 and 1,4-dicarboxylates are true hybrid compounds composed of infinite M-O-M linkages. The equatorial-equatorial (e,e) conformation is adopted commonly in all these compounds, although less stable conformations are encountered occasionally. The formation of the layered and the three-dimensional structures can be understood based on the relative disposition of the two carboxylic groups, the 1,4-isomer favoring the three-dimensional structure. Based on the results of the present study along with the available literature, we conclude that in order to obtain three-dimensional hybrid structures with metal-oxygen-metal networks, it appears necessary to make use of the 1,4-cyclohexanedicarboxylic acid.