2001 Vol. 14, No. 1

Article
The developments in pulse radiolysis studies of the formation of metal clusters in aque-ous solution are introduced. The property of metal clusters and their various reactions with other substances are summarized. The trends of research on this subject are prospected.
Mn/P、Ti/P binary cluster ions, produced by laser ablation, were studied with a Tan-dem TOF mass spectrometer. The experiments show that the clustering ability of Ti/P is stronger than that of Mn/P. And there is an odd-even oscillation in the peak strength of MPy+(M=Mn, Ti) series, the mass peaks of evenmare higher than those of oddm. This relates to the specific stability of P4structure. Through laser photodissociation, P4or P2is easy to be stripped, it can be inferred that some phosphorus atoms combine into P4or P2and the interaction between it and the other part of the cluster is weaker. In the growth of the clusters, MnxPy+cluster cations rich in P transferred to those rich in Mn, while in cluster anions MnxPy-, it tends tox≈y. For Ti/P cluster cations and anions, the number of atoms of Ti/P are all close tox≈y.
By using the high resolution dispersion spectra of NH2(~A2A1,090) 423(F1/F2) it is ob-served that the spin-rotational conservation transition is dominant for the parent levels. It con-firms the assumption that the electron is a spectator at single collision between open-shell and close-shell molecules. As to the daughter levels, the tendency for the conservation of the spin-rotation coupling of the parent level is found and may be explained by the long range interaction between those molecules.
The absolute optical oscillator strengths density spectrum and photoionization mass spectrometry of nitrous oxide in the energy region of 7.8~24.5eV have been measured at an im-pact energy of 2500eV with the FWHM 200meV. Values of the partial photoionization oscillator strengths density of N2O+, NO+, O+, N2+and N+are reported and values of the oscillator strengths density for neutral dissociation in the energy region of 13.0~21.0eV are reported for the first time. The competition among different decay channels of the superexcited states of ni-trous oxide is expatiated.
Blue and near violet upconversion luminescence originating from4D3/2and2G9/2levels in Nd3+:LaCl3can be induced upon excitation into2G7/2+4G5/2in the yellow region. Upconversion occurs via an energy transfer mechanism with or without excited-state absorption. Analysis of the upconversion tran-sient of4D3/2→4I11/2radiative transition at 12K leads to a rate constantwt1=1468 s-1for the energy transfer step. The lifetimes of the main fluorescence levels of Nd3+: LaCl3and NdCl3in the visible range were measured and the values are compared and discussed.
The reaction mechanism of the triplet-state NH+O3→HNO+O2has been studied by using ab initio MO method. The geometries of reactants, transition state, intermediate and prod-ucts have been optimized with HF/6-31++G** basis set and verified by frequency analysis. The single point calculation of the species have been performed by Mller-Plesset Perturbation theory up to 2nd order. The zero-point energies are also corrected, the results show that the re-action molecules combine with each other first to form an energy-enriched intermediate, fol-lowed by decomposition of the intermediate to give HNO and O2.
ab intio calculations for a group of 59 solvent molecules have been performed at HF/6-31G* level, linear correlation of five polarity scalesETN,π*, Py, SPPandS’of these sol-vents to electrostatic potential quantities calculated on molecular surface,Πandσtot2, have been es-tablished by using multiple regression. Comparisons have also been made between present analyses and those ones derived from correlation the polarity scales to the theoretical thermodynamic re-sults. It follows thatS’should be a good global solvent polarity scale,ETNis not appropriate to be used to describe the polarity of protic solvents, whileπ*andSPPare not good polarity descriptors for the aromatic and polychlorinated solvents.
The reaction paths for P-ylide and P-ylide-like radical were discussed. The invetigation of the topological properties of the chemical bonds was emphasized on. The following conclusions are given: After the energy transition states (ETS),Δtype transition structures appe in both of the two reactions. The mistakes in the previous paper by Brain F. Yates are pointe out and corrected: TheΔtype transition structures are the“structure transition state”(ETS) not the“energy transition state”(STS). For the two exothermic elementary reactions, the struture transition states (STS) both appear after the energy transition states (ETS), which are consistent with the conclusions we have given before. According to the topological properties, thchanging trends of the P2-H3bonds and C1-H3bonds are consistent in both the P-ylide and th P-ylide-like radical reactions.
The geometries, energetics and spectroscopic properties of oxygen clusters, Oxy(x=2~6, y=-2~2), were investigated at the B3LYP/6-311G (d, p) level. The CASSCF calculations were carried out for the ground and excited states of3O2and2O2+. The total energy is3O2(3Σg-)<2O2-(2Πgi)<1O2(1Δg)<1O2-2(1Σg+)<2O2+(2Πg)<1O2+2(1Σg+). The relative energy of the active doublet anion of oxygen molecule,2O2-(2Πgi), is only 28 kJ/mol higher than the triplet neutral oxygen molecule,3O2(3Σg-). The calculated O-O vibrational frequencies all are in good agreement with the experimental values. They are 1577 (1580), 1139 (1090), 1563 (1484), 627 (615~545) and 1993 (1905) cm-1, where the O-O vibrational frequency values in parentheses are experimental values, for3O2(3Σg-),2O2-(2Πgi),1O2(1Δg),1O2-2(1Σg+) and2O2+(2Πg), respectively. Moreover, the O-O vibrational frequency of1O2+2(1Σg+) was computed as 2368 cm-1which has not been reported before at both experimental and theoretical levels. Both bent and linear geometries of O3were studied. The bent-types of O3are more favorable than the linear-type in energy. Three types of structure for oxygen trimers are calculated at the B3LYP/6-311G (d, p) level. They are the structure-I with an obtuse angle of O-O-O,the structure-II with an acute angle of O-O-O, and the structure-III of linear type. For a bent-type structure of O3species (structure-I), the total enegy is2O3-(2B1)<1O3(1A1)<3O3(3B2)<1O3-2(1A1)<2O3+(2A1). The optimization of geometry at B3LYP/6-311G (d, p) level indicated that the species of2O3-(2B1) with 1.3573 of O-O bond length and 115.6584o of O-O-O bond anger is the ground state of O3. The total energy of O4species and their ions is2O4-(Cs,2A′, bend-type)<2O4-(C2v,2A2,face-centered triangle-type)<2O4-(D∞h,2Σg, linear-type)<1O4(Cs,1A′, bend-type)<1O4(D∞h,1Σg, linear-type)<1O4(D4h,1A1g, square-type)<1O4(C2v,1A1, face-centered triangle-type)<2O4-(D4h,1A1g, square-type)<2O4+(D∞h,2Σg, linear-type)<2O4+(Cs,1A′, bend-type). The species with the lowest relative energy is an anion,2O4-(Cs,2A′, bendtype), with chair form geometry and characteristic vibronic frequencies of 1179 and 1349 cm-1. The relative energy of1O5(C2v,1A1) with coplanar-triangle-bicone geometry is the lowest among the O5species and their ions, which may be a resonance structure with1O5(C2v,1A1) of A type. Their characteristic vibronic frequency is 1302 cm-1. The relative energy of the O6species and their ions with hexagon geometry is lower than one with linear geometry. Their infrared vi-bronic intensity may be weak and unobservable but the Raman vibronic intensity may be strong and observable based on their symmetry.
The SO2absorption spectrum is recorded using Xe lamp source under atmospheric conditions at ambient temperatures. The SO2concentration is retrieved to study the relation between SO2concentration and time. In this experiment, effects of temperature and the buffer gas N2are also considered. It is demonstrated that the concentration of SO2decreases in a linear relation to the time and the period of illumination may have effects on the rate of decrease. These results are applicable to SO2pollution monitoring in the atmosphere using high resolution spectrometer and differential absorption lidar.
The SO2absorption spectrum is recorded using Xe lamp source under atmospheric conditions at ambient temperatures. The SO2concentration is retrieved to study the relation between SO2concentration and time. In this experiment, effects of temperature and the buffer gas N2are also considered. It is demonstrated that the concentration of SO2decreases in a linear relation to the time and the period of illumination may have effects on the rate of decrease. These results are applicable to SO2pollution monitoring in the atmosphere using high resolution spectrometer and differential absorption lidar.
The microstructure of the carbon nanotubes were characterized by means of transmis-sion electron microscope, high-resolution transmission electron microscope, X-ray diffraction and Raman spectra. The effects of the microstructure on their properties of electrochemical insertion were investigated. The carbon nanotube, which preparaed by catalytic decomposition of acetylene using iron nanoparticles as catalyst, showed a low degree of graphitization. There were large amount of the defects such as wrinkled graphite sheets, interstitial carbon atoms, unorga-nized graphitic structure and microcavities in this nanotube and lead to a higher specific capacity, which is 640mAh/g at first cycle. But the defect structure resulted in a low cycling stability. After 40 cycles, its capacity was degraded to 58% of the original one. The carbon nanotube, which prepared by the pyrolysis of ethylene catalyzed by iron oxide nanoparticales, showed a high degree of graphitization and a rule microstructure. The well-graphitized carbon nanotube exhibited a low electrochemical storage lithium capacity, which is 282mAh/g at first cycle. But it showed a good cycling stability. After 40 cycles, the capacity maintained 86% of the original capacity. The influences of the temperature and charge/discharge current densities on their electrochemical storage lithium capacities were also discussed.
Nano-ZnO particles were prepared in the ordered pores of anodic aluminum oxide membranes through hydrolyzation routes of metal alkoxide. Scanning Electron Microscope (SEM) and High Resolution Transmission Electron Microscope (HRTEM) were used to observe the morphology. Photoluminescence spectra of the assembly of nano-ZnO/anodic aluminum oxide membrane were measured. The photoluminescence intensity of the nano-ZnO particles in the assembly was compared with that of nano-ZnO particles which was prepared by conventional process. The reason of the enhancement of the photoluminescence intensity was discussed.
The interaction for Gelatin with Silver(I) ion have been developmented by UV/Vis, IR spectra, TEM and conductance.electropheresis methods respectively. Where were also investigated that the effect of pHmedium, temperature and multicomponent concentration on interaction gelatin-silver. It is an autocatalysis reduction process that reaction of gelatin-silver, and a colloid system on any condition. It has maximum absorbance at 233 and 422nm. It is formed a multinucleate complex under suitable condition first, then reduced to metalic Ag particle and collectived to superfine colloidal gel, which is carried on positive charge, diameter of colloid particle about is 30nm and electrokinetic potential of double electrode layer is 0.014~0.016V.
The ethylene(C2H4)absorbs in molecular state on Ru (1010) surface stably below 200K. The dehydrogenated of ethylene occurs at 200K. The main product of the dehydrogenation of the absorbed ethylene is the acetylene (C2H2). After the dehydrogenation of the absorbed ethylene, the binding energies ofσCCandσCHbond have an increase of 0.5 and 1.1eV respectively. The C-C bonds of both ethylene and acetylene tilt in <0001> azimuth.
The local structures of the oxidic and sulfided molybdenum loaded KHMoY zeolites prepared by solid-state reaction and the sulfided mixtures of KHY/MoO3have been investigated by EXAFS. The alcohol synthesis of CO hydrogenation is used to characterize catalytic performance for the sulfided (K, Mo)Y catalysts which is well explained by the EXAFS results. The results indicate that the local structures of Mo(VI) species depend on the atomic ratio of (K+2Mo)/Al. At the ratio of (K+2Mo)/Al lower than the exchange capacity, i.e., 1, the molybdenum species are completely dispersed into the supercages of the zeolites as small atomic cluster of MoS2. At the ratio of (K+2Mo)/Al lager than 1, the molybdenum species could exist in two phases, including both inside and outside of the zeolite supercages. Moreover, the size of MoS2located at the out-surface of the zeolite supercages is much larger than the one in the zeolite supercages. We present that MoS2cluster in the zeolite supercages of zeolites has a higher selectivity of alcohol synthesis for the CO hydrogenation than the MoS2particles located at the out-surface of the zeolite supercages.
The effects of poly(ethylene glycols) with different molecular weight (PEG1000, PEG2000, PEG6000) and polyvinylpyrrolidone with different polymerization degree (PVP-K30, PVP-K90) on the cloud point of nonionic surfactant dodecyl polyoxyethylene polyoxy propylene ether C12H25O(EO)m(PO)nH (LS36,m=3, n=6; LS45,m=4, n=5; LS54,m=5, n=4) were studied in the paper. It is found that a higher polymer concentration can result in a significant decrease on the cloud point of the aqueous surfactant solutions because of the formation of corona-shaped intra-chain micelles which indicate that the micelle-micelle interaction is attractive and can be expected to facilitate collisions among the micelles, as well as a slightly increasing at a lower PVP concentration because of the effects of viscosity, charge, and interaction between the polymer and surfactant.
The excess copolymerization enthalpy was defined to describe the intramolecular intaction within random copolymers, based on statistic physical interaction and the mean field thry. The interaction parameterχblendof the two-component polymer blends and the mixing thalpy of the three-component polymer blends were derived The miscibility of commonly ubinary polymer blends and the compatibility of the three component polymer blends were dcussed in brief. The interaction parameterχblendcould well explain the miscible behavior, not compatible behavior in polymer blends.