2004 Vol. 17, No. 2

Letter
This letter reports a study on producing gas-phase O2(a1Δ)by decomposition of triphenyl phosphite ozonide((C6H5O)3 PO3,TPPO3)under a number of reaction conditions. For the first time,the cooperative emission at wavelengths 634 and 703 nm of O2(a1Δ)generated by TPPO3 decomposition are observed. Specifically,under the condition of catalyzed decomposition by pyridine of TPPO3 solution in CFCl3 at low temperature,the emission spectrum is the same as that from the basic hydrogen peroxide plus chlorine reaction. This shows the feasibility of developing a new source for singlet delta oxygen. However,in the experiments of spontaneous decomposition of solid TPPO3 and thermal decomposition of TPPO3 solution on a high temperature surface,the spectra have a wide emission background around the 634 and 703 nm peaks,which indicates the production of some excited species than O2(a1Δ). Besides,there are about 2%-3% CO and 1. 5%-2% CO2 in the gaseous products together with a small amount of insoluble in acetone solid product,which imply that other than the formation of O2(a1Δ)and TPPO by unimolecular decomposition of TPPO3,more complicated reactions may take place. The study of the reaction mechanism,the optimization of the expertise of O2(a1Δ)generation by TPPO3 decomposition as well as measurement of absolute concentration of O2(a1Δ)are under way.
Article
The gas phase reaction of Ni plasma and methanol clusters is studied by the laser ablation-molecular beam(LAMB) method. Five species of clustered complex ions Ni+(CH3OH)n,NiO+(CH3OH)n,H+(CH3OH)n,H3O+(CH3OH)n,CH3O-(CH3OH)n(n≤25)are observed. Interestingly,the species and sizes of the product clusters vary observably when the plasma acts on the different parts of the pulsed methanol molecular beam. When the laser ablated Ni plasma acts on the head and tail of the beam,the metal methanol complex clusters Ni+(CH3OH)n and the oxidation clusters NiO+(CH3OH)n(n=1-15)together with protonated methanol clusters H +(CH3OH)n are domain. While the plasma acts on the middle of the beam,however,Ni+(CH3OH)1-2 and H+(CH3OH)n along with the mixed methanol-water clusters H3O+(CH3OH)n(n=15-25)turn to be the main resulting clusters. By comparing the intensities and the cluster sizes of NiO+(CH3OH)n with Ni+(CH3OH)n,the formation of NiO+(CH3OH)n is contributed to the intracluster demethanation reaction of Ni+(CH3OH)n and evaporation of several methanol molecules. As the H3O+(CH3OH)n is observed only when the plasma acts on the high density part of the beam,and their intensities are only 0. 5% of the protonated methanol molecule,it is concluded that the species are partially due to the recombination of H+(CH3OH)n and water,which come from the plasma-molecule reaction.
The vacuum ultraviolet photoionization of ferrocene has been studied by using synchrotron radiation and a time-of-flight(TOF)mass spectrometer. The photoionization TOF mass spectrum and photoionization efficiency (PIE)curves of some ions were measured. VUV absorption by ferrocene results in Fe(C5H5)2+,FeC5H5+,Fe+,FeC3H3+,FeC3H+,C10H9+,C10H8+ and C5H6+. The ionization potential(IP)of ferrocene is determined to be (6.78±0.05)eV. The appearance potential(AP)of the fragment FeC5H5+ was measured to be(13.40±0.10)eV. In addition,theoretical calculations with the density functional method B3LYP and the basis set 6-31G(d)have been carried out. The calculation result shows that the ionization potential of ferrocene is 6.16 eV,which is smaller than that from the experiment because the ionization potential from calculation is adiabatic value and the experimental result is vertical value. Due to the limited available computational cost,the case of the electron spin S=1/2 for Fe is only considered,which may lead to some low precision in calculation. So the calculation result is just as references. The appearance potential of FeC5H5+ is 12.17 eV,which is also smaller than the experimental value. According to the experimental and calculation results,the bond energies of D0(FeC5H5+-C5H5),D0(Fe+-C5H5),D0(C5H5-Fe+-C5H5)have been evaluated and the possible channels of dissociation photoionization have been analyzed. Sequential elimination of C5H5 ligands is a major dissociation channel,but concerted elimination of two C5H5 ligands also takes place.
Being an electron deficient polyene,[60]Fullerene(C60)is prone to radical and nucleophilic addition reactions as well as to cycloadditions. Various[2+n]cycloaddition reactions show considerable promise for functionalization of the fullerene sphere,the reactions with n=1,2,3 and 4 being most typical. Among the[4+2],[3+2],[2+2]and[2+1]cycloaddition reactions,the[3 + 2]addition has been widely studied. 1,3-Dipolar cycloaddition of azomethine ylide prepared via the reaction between amino acetic acid and 4,5-dimercapto methyl-1,3-dithioleyl(DMIT)to C60 rises to novel C60 pyrrolidine derivative C66H9NS4 . The molecular structure is identified and characterized by FTIR,UV-Vis,H-NMR and elementary analysis. The electronic spectrum of the title compound is studied by using INDO/ S method on the basis of the optimized geometrics with B3LYP / 6-31G(d)method. It is shown that the exception of the absorption is beyond 438. 9 nm. The calculated results are essentially consistent with experimental values.
Based on the wavefunctions obtained in the calculation of C-H stretching overtones of C6H6 and C6D6 molecules,the visible and infrared transition intensities of the molecules for C-H stretching overtones up to as high as v=0 are described by the Iachello-Oss algebraic model on the symmetric bases. The formula for Raman transition is also given. The operators for the transition are constructed according to the symmetry of the molecule. The construction of the symmetric bases is greatly simplified by using the symmetrized boson representation technique. Combining with the overtones calculation,the present work shows the vibration mode of C-H stretching is the local mode,which is consistent with other works. The agreement between the calculated results and observations is very good. The agreement indicates that the coupling between C-H stretching mode and other modes is weak or the coupling effects can be absorbed in the adjustment of parameters. The high precision calculation of the properties of molecules can be achieved by the algebraic model with fewer parameters compared with the traditional method. It also indicates that the combination of algebraic model and the symmetrized boson representation technique is a very powerful tool for describing the vibration of molecules.
Using DFT method at B3LYP / 6-311G** level,the possible electronic states of RuH2 and RuN2 have been calculated,including the chemical adsorption and physical adsorption. For the RuH2 cluster,electronic states 3B2 and 5Σ- correspond to the physical adsorption. The RuN2 calculation results were also compared with the experimental values on ruthenium single crystal surfaces. It is found that the single states and the triplet states are in good agreement with the experimental values. For the C∞v symmetry,the calculated frequency of the quintuple state 5Σ- is slightly lower than the experimental value. For the C2v symmetry,the frequencies of the quintuple states are much lower than the experiment value and the 3B2 and 5A1 states are unstable.
Cations of fluorinated pyridines(pentafluoropyridine,2,6-difluoropyridine,and 2-fluoropyridine)have been studied by using density functional B3LYP method in conjunction with 6-31G(d,p),6-311G(d,p),6-31+G(d,p),and 6-311+G(d,p)basis sets. B3LYP geometry optimization and frequency analysis calculations indicate that the pentafluoropyridine cation,2,6-difluoropyridine cation,and 2-fluoropyridine cation have C2v,C2v,and Cs structures in the 2A2,2A2,and 2A" ground states,respectively. The calculated geometries of the cations and the parent molecules were compared. The natural population analysis calculations at the B3LYP level with different basis sets were performed on the three cations and the three parent molecules. The isotropic hyperfine coupling constants in the three cations(radicals)were calculated. The vertical and adiabatic ionization potential(VIP and AIP)values of the pentafluoropyridine,2,6-difluoropyridine,and 2-fluoropyridine molecules were calculated by using the B3LYP method,and the calculated VIP values are in excellent agreement with experiment.
The hydrogen bond is one of the most important intermolecular interactions playing an important role in intermolecular recognition processes essential to most biological systems. Adrenaline is an important catecholamine neurotransmitter in the mammalian central nervous system. Dimethyl sulphoxide can carry with it drugs across membranes. The geometries of adrenaline and six stable 1 : 1 complexes formed between adrenaline and dimethyl sulphoxide were optimized by Berny method at PM3 level and thus were optimized by density functional theory(B3LYP method)at the 6-31G,6-31G*,and 6-31+G* level respectively to obtain accurate structures. Single-point energies of all optimized molecular geometries were calculated to discuss the energies and structural parameters between reactants and products. All the binding energies have been corrected by the zero point vibrational energies(ZPVE)at varied basis set levels from 6-31G to 6-31 + G*. The results indicated that stronger hydrogen-bonded complexes were formed by molecular interaction between adrenaline and dimethyl sulphoxide. The calculation results can be better used to explain some experimental phenomena.
Self-diffusion is one of the most fundamental motions of particles in liquid. Nuclear magnetic resonance (NMR)provides a convenient and noninvasive means for accurately measuring the self-diffusion coefficient of molecules in solution. The theoretical expressions of apparent diffusion rates of MQCs are given and computer simulation based on the method to measure the self-diffusion coefficient by NMR was discussed and the random walk model of particles is used to simulate the apparent diffusion behaviors of intra-molecular and inter-molecular multiple-quantum coherences(MQCs). The results of computer simulation agree well with theoretical predictions.
Transparant conducting oxides showing the combination of high electrical conductivity and high transparency for visible light have been based on electron doping into a conduction band. For p-type delafossite oxides,the valence band is commonly the oxygen 2p band. Doping to produce holes in this band but the electronic conductivity of such p-type oxides is highly activated and can generally only be measured at temperatures well above room temperature. So it is very desirable to improve conductivity by doping wide-gap delafossites as transparant conducting oxides nowadays. The article reported the prepration and characterization of Ca-doped CuCrO2 monophasic delafossites. It was found that conductivity had a notable improvement after Ca-doped and reached 3. 2×10-2 S/cm for x=0.06 Ca-doped at room temperature and the structures had not been changed. The temperature dependence of electrical conductivity around room temperture was consistent with thermal activation type very well from 200 K to 300 K. The activation energe was 0. 36 eV before doping,but it changed to 0.27 eV when Ca-doped. This phenomenon suggest that in pure non-doped CuCrO2,carrier was the Cu+ d. After Ca-doped,the Cu2+ was formed from the Cu+ by a charge compensating process when the divalent Ca2+ substituted for the trivalent Cr3+ . The Seebeck coefficients being large positive constants implied that all the samples were p-type conducting oxides.
Silica sols were prepared by hydrolysis of Si(OC2H5)4(TEOS)using HCl,NH3·H2O,HCl/NH3·H2O as catalyzers,and the different granularities of SiO2 sols which catalyzed by HCl first and then NH3·H2O have the same terminal pH value were prepared. The silica colloidal particles were investigated with Transmission Electron Microscope(TEM). The results showed sol catalyzed by HCl possesses very little particle,catalyzed by NH3·H2O has particle configuration,catalyzed by HCl/NH3·H2O possesses consecutive configuration. Poly(diallyldimethylammonium chloride)(PDDA)and SiO2 nanoparticulate complex thin films were prepared by electrostatic self-assembly multiplayer(ESAM)method. After assembling films,thin films surface conformation was observed with Electron Microscope and their transmittance was tested with 721 Spectrophotometer. The results showed that the silica sol catalyzed with HCl is not good for the fabrication of ESAM films and the silica sol catalyzed with HCl first and then NH3·H2O or by NH3·H2O only are very suitable for ESAM film fabrication. TEM data indicate that the microstructure of PDDA/ SiO2 prepared from silica sol catalyzed with HCl first and then NH3·H2O is consecutive and that the microstructure of PDDA/ SiO2 prepared from silica sol catalyzed by NH3·H2O only is particulate-parking like. The dependence of the transmittance of assembled films on the bilayer number of the films and the anti-scratching properties of the films were investigated. The results show that PDDA/ SiO2 films prepared from silica sol catalyzed by NH3·H2O only possess higher transmittance but lower anti-scratching properties. The effect of granularity of sols on optical performances of the thin films was studied,results showed the less the granularity of sol,the better the optical performances. For the sake of improving the light transmittance of films,we can reduce the granularity of sol,but it may play down its mechanical damage resist intensity.
The solution dispersion method has been successfully used to prepare Pb nanoparticles in a paraffin oilpolyglycol mixed solution by directly dispersing melted Pb granules. In this solution system,paraffin oil was used as reacting media and polyglycol served as an antioxidant to protect Pb nanoparticles from oxidizing. The size and structure of the prepared Pb nanoparticles were characterized by means of the transmission electron microscopy (TEM)and powder X-ray diffraction(XRD). Their tribological behavior was evaluated with a four-ball tester. The TEM and XRD investigations reveal that the prepared Pb nanoparticles,with the average particle diameter of 70 nm,appear to be of close spherical shape and possess the same crystal structure as the bulk Pb. The tribological results show that the Pb nanoparticles as an oil additive exhibit good friction-reduction and antiwear properties at different additive concentration and applied load. Meanwhile,they can also strikingly improve the load-carrying capacity of the base oil. The rubbed surface was also investigated by the scanning electron microscope(SEM)and energy dispersive spectroscopy(EDS). However,there was not presence of Pb element on the worn surfaces,which indicated that no chemical reaction occurred between the Pb nanoparticles and the rubbing surfaces. In addition,the tribological mechanism of the formation of the sliding-bearing system was also proposed.
Ultra-fine whiskers of calcium carbonate were successfully synthesized by reactive precipitation in highgravity field generated by the rotating packed bed(RPB). In the experiment Ca(OH)2 and CO2 were as reactants and H3PO4 was used as the morphology-control additive. Synthesizing the same amount of CaCO3 whiskers,the needed carbonation time in the high-gravity field is 1/36-1/18 of that by the traditional technology reported in the literature. The ultra-fine CaCO3 whiskers can be synthesized and well-controlled under the following conditions:the volumetric flow rate of gas 100-300 L/h and that of liquid 600-1000 L/h,rotating speed of RPB 600-1200 r/min,reaction temperature between 40-80℃ and concentration of H3PO4 5.0%-30%. The calcium carbonate whiskers have the mean shaft diameter of 80-250 nm and the average aspect ratio of 10-25 with the narrow distribution of both the mean shaft diameter and the aspect ratio. The properties of the product are characterized by means of TEM,electron diffraction,XRD,TG-DTA and elementary analysis. Electron diffraction analysis shows that the synthesized calcium carbonate whiskers have crystalline structure,while XRD analysis indicates that aragonite structure accounts for 97.77% in content of the final CaCO3 whisker product. And TG-DTA analysis shows that the obtained product decomposes at 423℃,which is 402℃ lower than that of the CaCO3 obtained in the normal gravity.
The surface tensions of aqueous lithium bromide(LiBr)with additive(2-ethyl-1-hexanol and 1-Octanol)have been measured by using a Wihelmy plate method,and the enhancement effect of the additives on the absorption of steam into aqueous LiBr in a static pool has been studied by a real-time type laser holographic visualization method. The experimental results show that both of liquid additive and vapor additive can decrease the surface tensions of aqueous LiBr significantly,vapor additive not only can trigger the Marangoni convection at the absorption interface just like the liquid additive,but can bring about better enhancement effect on the absorption performance than that liquid additive can. The enhancement mechanism of additive on absorption has been concluded that both liquid additive and vapor additive can be adsorbed by aqueous LiBr at the liquid-vapor-interface from the liquid side and the vapor side respectively,which result in surface tension gradient,and then cause Marangoni convection at the interface which enhances the heat and mass transfer performance during the absorption process.
To obtain more crystal and magnetic structural information of powder crystals,magnetic field is introduced into X'Pert-MPD XRD apparatus with the strength of 0. 42 T and two different directions:one direction of magnetic field is vertical to the sample holder and another is parallel. XRD patterns in situ magnetic field are obtained for six samples which are representative of paramagnetic,diamagnetic,ferromagnetic,ferrimagnetic,antiferromagnetic substances and reduction product of FeCl2 by NaBH4 respectively. Compared with XRD patterns obtained in the zero magnetic field,there are some diffraction peaks disappear,some occur,or some diffraction angles and counts change. In addition,the patterns are different under the different direction of magnetic field. The cause is that magnetic dipoles in crystals are oriented along with the direction of magnetic field. The oriented magnetic dipoles produce stress in crystals and make crystal lattice changed(such as magnetostriction)or even turn particles aligned along with the direction of magnetic field to form preferred orientation of particles.
Super acidic catalyst SO42-/ZrO2 was prepared and characterized by XRD,IR,and Py-IR. Selectively catalytic gas phase flow reactions of benzene and propene over the catalyst were carried out in a made-to-measure high pressure flow reactor with a thermometer and a condenser. The benzene and propene were kept in pressure tanks at 8 : 1 ratio with N2 gas at 4. 0 MPa. The reactants were pumped into the quantifier where the pressure was maintained by N2 gas at 8. 0 MPa. They were then pumped into the reaction reactor using catalytic synthesis of isopropyl benzene. The collected liquid phase products were analyzed using GC-MS. Product analyses were carried out on SE-54. The effect of the preparative condition on the catalytic synthesis of isopropyl benzene over the catalysts has been tested. The result shows that the SO42-/ZrO2 can be used as a catalyst for the title reaction,and shows higher conversion(99.2%)for the propene and higher selectivity(93.3%)for the isopropyl benzene when the catalyst is preparated in some condition.
In order to obtain that more information on the secondary and active site structure of polyphenol oxidase from nicotinan tobacco,FT-IR,synchronous fluorescence and Vis-UV have bee employed to study the secondary structure changes of polyphenol oxidase induced by pH. The results show that,compared with native PPO(pH=7),PPO at pH=2 contains less both a-helix and anti-parallel β-sheet,more random coil,and almost the same amount of β-turn,and that PPO at pH = 11 contains less a-helix,anti-parallel β-sheet,β-turn,and more random coil. The microenvironments of both Trp and Tyr residues in PPO undergo some changes with pH changing. With the decrease in pH values at the range of pH=7.0-3.38,the coordination between Cu2+ in the active site and imidazoles of histidine are strenghtened. Different LMCT bands of the PPO active site have been observed by changing pH,which result from the structure of Cu(Ⅱ)-imidazole and Cu(Ⅱ)-imidazolate.
In order to research the flooding efficiency of flooding systems and wettability on the simulant rock surface,the orthogonal-test-design method was used to determine the optimal formula for the crude oil from the Chunliang zone of Shengli oil field by transient interfacial tension(IFT). The results indicate that two optimal formulas are naturally mixed carboxylate SDC-V(0.35%,0.36%),nonionic surfactant FBB(0.06%,0.07%),Alkaline NaHCO3 / Na2CO3 weight ratio of(0.8%,1.2%)and HPAM(0.05%,0.15%),and in the coreflood experiment,their oil recovery are(14.6%,16.7%)OOIP respectively. The contact angles have been determined for the two optimal formula systems and their components on the simulant rock surface,which points out the relationship between the flooding efficiency and contact angle is showed identification,that is,the more oil recovery the less contact angle. It will be useful to the application research of microgravity.
The electrochemical biosensor properties of the molecular devices based on solid supported bilayer lipid membranes were investigated. The results showed that the system embedded with antihistaminic agent had strong response for the histamine. The response currents for the histamine will rise following the increasing concentrations of the histamine,as a result of the special opposing effect between histamine and antihistamine. Near the normal physiological condition(pH=7. 5),a good linearity occurred for the current response against histamine concentration ranging from 3. 0 to 60. 0 μg / L,and the relation coefficient R is 0. 9878. All the experiments mentioned above showed good sensitivity,selectivity and stability. This system can measure the concentration of histamine under -200 mV by voltammetry and be expected to form the electrochemical biosensor with high stability and low detection limit.
The nanometer films of TiO2 were prepared by sol-gel method on ITO(Indium-tin oxide,SnO2:In) substrate. The TiO2 film was the anatase phase with a particle size of 100 nm from the measurements of X-ray diffraction and AFM(Atomic-Force-Microscope). Electrochemical characteristics of ITO/ TiO2 electrode under UV(ultraviolet)irradiation were investigated using the method of cyclic voltammetry. A new oxidative peak was observed at 0.035 V when the TiO2 electrode was irradiated by 253.7 nm UV light for a certain time. The peak current increased with the irradiation time. It was assumed that the new oxidative peak resulted from Ti3+,which was formed during the UV illumination. The changes of hydrophilicity of the TiO2 thin film on ITO under UV light were also observed. It was assumed that the changes of hydrophilicity of the films may be related with the formation of Ti3+ on the surface when the film was irradiated by UV light.
The representative soft lithographic techniques are used,which are micromolding and microtransfer molding methods to fabricate the micro array patterned titanium dioxide on glass substrates. Firstly titanium dioxide sol was synthesized by sol-gel method using tetrabutyl titanate as the precursor,then the pre-patterned poly(dimethylsiloxane) elastomeric stamp was used to mold the TiO2 sol on glass substrate by micromolding and microtransfer molding methods,micro patterned TiO2 sol was gelled at 70℃ with 0. 5 N pressure applied on the PDMS stamp,further heat treatment of TiO2 gel by annealing at 550℃ for 2 h produced the TiO2 microstructure. The TiO2 microstructure was observed by the optical microscope and the optical micrographs demonstrated the satisfactory yield and fidelity of pattern transfer by micromolding method and microtransfer method. The effect of gel temperature,the pressure applied on the PDMS stamp and the silicone mold on the fidelity and yield of TiO2 microstructure are discussed.
A new isothermally based cure kinetic model for the prepreg was presented using an industrially supplied prepreg rather than neat resin. The matrix resin was bismaleimide(BMI)resin,and the reinforcement was carbon fiber T700-12S. A series of isothermal Differential Scanning Calorimetry(DSC)tests were performed and analyzed by the proposed nth-order reaction model. An increase in the cure rate was observed at the higher temperature in both neat and prepreg. After reaching the peak value,the cure rate of resin dropped off faster in prepreg,resulting in a lower average value of the ultimate heat of reaction. The presence of carbon fiber was found to significantly impact the curing behavior of the resin,leading to significant changes from the neat resin kinetic parameters. The carbon fibers imposed restrictions on the molecular mobility of reactive species,reduced the extent of polymerization within the system and did not change the cure mechanism of resin.