1997 Volume 13 Issue 6
Raman spectroscopy was applied to characterize the species deposited from the mass-selected C60 ion beam which was accelerated to 900 eV. The substrates for the deposition were (0001) surface of highly oriented pyrolitic graphite and (111) surface of ld crystal. The species do not exhibit the Raman scattering features of buckminsterfullerene, but displays peaks at 1585 and 1332 cm-1 instead. The former peak is the chararteristic Ranan peak of hexa nal graphite, and the latter can be attributed to the amorphous carbon in sp3 hybridization. The result reveals that C60 was collapsed to form a new phase when it collides on the solid surface.
Polydentate ligands, N,N'-bis[o-(diphenylphosphino)benzylidene]-1,2-propane-diamine [P2N2Me for short] and N,N'-bis[o-(diphenylphosphino)benzy1]-1,2-propanediamine [P2N2 H4Me for short] have been synthesized. The interaction of RuCl2(DMSO)4 with one equivalent of P2N2Me or P2N2H4Me in refluxing toluene gave trans-RuCl2(P2N2Me) and trans-RuCl2(P2N4H4Me) in od yield, respectively. The ligands and the complexes have been fully characterized by elemental analysis and spectroscopic methods. The complexes act as an excellent catalyst precursor in hydrogen transfer hydrogenation of acetophenone in catalyst: acetophenone :iso-PrOK of 1: 100: 15, leading to 2-phenylethanol of 89-96% yield.
A new numeric method is proposed to analyse the polarization of flow-through bipolar electrodes. This method is able to predict the behaviour of three-dimensional bipolar electrode based upon the experimentally measured monopolar polarization curve. The effect of electrolytic current density and solution resistivity on current efficiency is also discussed.
To study intermolecular energy transfer of rare earth-β-diketones, monolayers of mixed RE(TTA)3Phen (RE=La, Gd, Tb, or Y) with Eu(TTA)3Phen in molar ratio of 1:1 and 1:4 were fabricated in this paper. Meanwhile, an active enhanced sphere model was proposed to acquire the efficient radii of energy transfer between the molecules of complexes. The efficient radius for energy transfer from Gd(TTA)3Phen or Tb(TTA)3Phen to Eu(TTA)3Phen is 12Å and those from La (TTA)3Phen and Y(TTA)3Phen to Eu(TTA)3Phen are 7Å and 10Å, respectively. The reliability of the model was proved by comparing the emission intensities that were calculated by using values of R mentioned above with experimental values. The model proposed is a supplement to Perrins active sphere theory. By this model a triplet-triplct energy transfer can be deduced from TTA of RE(TTA)3Phen to that of Eu(TTA)3Phen. The process proceeds by an electron exchange mechanism.
By selecting phase-separable glass system Na2O-Al2O3-B2O3-SiO2 as the base glass and by introducing Cu+, I- from the starting materials CuO/SnO and NaI respectively, CuI microcrystal doped silicate glasses have been prepared successfully. The microcrystal and its distribution in the glass medium are observed by means of X-ray diffraction and HRTEM. The effects of heating treatment on the optical absorption of glasses is studied by the transmission spectra of glasses at room temperature. It is also found from the experiment that the glasses have the effect of compressing the pulse-width of the free oscillation in the cavity of Nd: YAG laser.
The thermokinetic equation (MTD) of mitochondrial metabolism was deduced and the relation between this equation and exponential model was examined. The technology of evolutionary computation was first introduced to the research of biological thermochemistry. The thermokinetic parameters of some mitochondrial external metabolism were globally optimized with the evolutionary computation program about MTD, which was programmed ourselves, and excellent result was obtained.
On the basis of experimental study the electronic structure of Sb2Te3 and its solution has been calculated using the discrete-variational Xα method. It is shown that the energy gap of pure Sb2Te3 is zero using the expanded basis; the Sb-Te bond in pure Sb2Te3 is almost "pure" covalent contributed by valance s and p orbitals; with the addition of Se the gap increased to 0.19eV, which can eliminate the bipolar effect contribution to the thermal conductivity. All the theoretical results obtained are in od agreement with the experimental ones, indicating the adequacy of using DV-X quatum mechanical method to the calculation of semiconductor atomic clusters.
A simple and general method for synthesizing functionalized alkanethiols is reported. The synthesis started from carboxylic acid, RCOOH, which was selectively condensed with the amino group of 2-aminoethanethiol, thus giving the targetting thiol compounds. A series of thiol compounds having a structure of RC(O)NHCH2CH2SH, where R was azobenzene derivatives, dicetylene derivatives and n-akanes, respectively, have been synthesized using this method. The self-assembled monolayers(SAMs) of these species were characterized by wettability measurement, electrochemistry and grazing incidence refletance infrared spectroscopy(GIR-IR). The SAM from 4((N-(2’-mercaptrvethyl)amino)carbonyl) azobenzene showed clearcut electrochemical reactivity in aqueous solution, in which the surface coverage was evaluated to be 4.21×10-10mol•cm-2. On the other hand, for the thiols of R being n-alkanes, the packing structures became gradually improved with increasing the alkyl chain length. For CH3(CH2)6C(O)NHCH2CH2SH SAM, GIR-IR data indicate that the C=O and N-H groups are parallel with the substrate surface while the whole molecular axis is perpendicular to the surface.
Multinuclear solid-state NMR, including (29)Si、(23)Na、(11)B MAS and (29)Si CP/MAS NMR was employed to study the structure change of Na2O-B2O3-SiO2 glasses after 24 hour heat-treatment of phase separation at different temperatures. Then the glasses were etched with acid. The results show that there is a turning point temperature. Being confined by dynamical factors, phase separation did not reach equilibrium below this temperature. The degree of phase separation was reduced when the temperature was decreased. When the temperature was above this turning temperature, the phase separation could reach equilibrium. Being controlled by thermodynamics, the degree of mtiscibility was enhanced when the temperature was increased. The phase separation was the best when the heat-treatment of phase separation was proceeded at this turning temperature. The NMR results obtained from different resonant nuclei were consistent with one another.
AM1 molecular orbital method using the unrestricted Hartree-Fock (UHF ) calculations has been applied to investigate the thermal Diels-Alder reaction of cyclohexadiene and CH2=CHR (R=CH3, CHO and CN). The results obtained indicate that these thermal Diels-Alder reactions may occur through the concerted pathway and also two radical pathways.
Rotation of C60 molecule in C60 crystal was studied by using the L-J potential, the rotational barriers on six different rotational axes have been obtained. Since C60 molecule in the crystal rotates with a high speed, the interaction potential of the rotational molecule with other C60 molecules was considered as the average of the latter being distribute on the sphere of the rotating molecule. In the computational process, the nearest -neighbor interactions and the second nearest-neighbor interactions have been considered. The results show that the second nearest -neighbor interactions have neglected influence on the rotational barriers.
The electrocatalytic oxidation of methanol on polythionine(PTn) film modified with Pt microparticles has been studied by means of cyclic voltammetry and in-situ FTIR spectroscopy. The Pt microparticles produced by cyclic voltammetry were highly dispersed in and on the PTn film. The modified electrodes exhibit significant electrocatalytic activity for the oxidation of methanol and the catalytic activity was found in dependence on the Pt loading. The linearly adsorbed CO species is the only intermediate in the oxidation of methanol and the abnormal IR spectra for adsorbed CO were observed. On such modified electrodes, adsorbed CO species derived from methanol can be readily oxidized. The enhanced electrocatalytic activity may be ascribed to the high dispersion of Pt microparticles in and on the PTn film and the synergestic effect between Pt microparticles and the polymer. From the above results, a possible reaction mechanism was proposed.
Influence of doping Pr on the characteristics of VPO catalyst was investigated by means of XRD, XPS, ESR, 31P NMR, NH3-TPD and IR techniques. The catalysts were used in the selective oxidation of n-butane to maleic anhydride. Experimental results showed that, when Pr/V(atomic ratio)=0.05,the amount of (VO)2P2O7 was increased and the surface acidity was enhanced, and the conversion of n-butane and the selectivity to maleic anhydride reached a maximum value respectively. While Pr/V≥0.10, the amount of(VO)2P2O7 and surface acidity were decreased and the activity of catalysts was reduced.
The Y zeolite dealumiated by oxalic acid and ammonium oxalate maintained the faujasite structure with a od crystallinity. The OH-IR spectra and chemical analysis showed that there were aluminum vacancies in the framework of the dealuminated Y zeolite. In such a dealuminated Y zeolite, the hydroxyls represented by 3550cm-1 was accessible to pyridine, while not so stable as the hydroxyls represented by 3640cm-1 when they were heated in vacuum. The IR spectra of double probes of Pyridine and CO illustrate the production of extra-framework aluminum species which are related to Lewis acid sites in the process of dehydroxylation. The results of N2 adsorption at low temperature suggest the existence of secondary pores which are much larger than the aluminum vacancies, and this probably resulted from the structure reconstruction.
The configuration and photoelectron processes of metal-free phthalocyanine multilayered film have been discussed in detail. And by the study of photodecay surface residual potential, the results obtained are that the initial surface dark potential (Vo) charged from DC corona voltage (-6kV) is -910V, the dark surface potential (Vd) measured atter 2-sec. dark decay is -825V, it is 90.3% of the initial surface dark potential (Vo), the rate of dark decay (DR) calculated from initial surface potential (Vo) and dark surface potential (Vd) is 9.3%, the surface residual potential (Vr) measured after 1.5-sec. illumination is 40V, the light sensitivity (E1/2) calculated from illumtinating power (EL) and the time of half photo-decay (t1/2 ) is 2 lux.sec. These values are in valid values region of laser printers. Indicating that metal-free phthalocyanine used in function separated multi-layered film is an appropriate photogenerator-photoconductor. It would pave a solid road to small-size for copies, especially for laser printers, and much expanded scope of studies and applications in organic photoconductor.
The inflence of the additives, NaH2PO4 and 1-hydroxyethylidene-1,1'-diphosphonic acid (HEDP), the concentration of HNO3 and the temperature of reaction on the phase transformation and aggregation of Fe2O3 particles obtained by the boiling reflux of 0.2mol-1 Fe(NO3)3 solution has been studied using TEM and XRD. Phosphate gave monodispersed spindle-shaped α-Fe2O3 perticles used as magnetic recording material. Nanowhiskers of α-Fe2O3 was formed in the presence of HEDP and HNO3. The method is provisionally referred to as the inhibitory subcrystal aggregation method.
The enthalpy changes, entropy changes and equilibrium constants of coordination reactions of 18-crown-6 with the alkali ions Na+ and K+ at 298.15K were measured by using RD-496 microcalorimeter with methanol, ethanol, n-propanol and n-butanol as solvents respectively. The results indicated that the enthalpy changes △rHm, entropy changes △rSm, and the stability of the complexes are closely related with the polarity of the solvents, and the order of the stability is ethanol>methanol>n-propanol>n-butanol>H2O for the same complex in the solvents investigated. The stability order was reasonably explained by relating the stability constants of the complexes with the dielectric constants of these solvents, and by using the model of solvated-desolvated ions and ion pair in the coordination reactions.
The influence of second metal component (Fe) on Pt/KL zeolie catalyst was investigated. The catalytic properties of Pt-Fe/KL zeolite varied as the amount of Fe. When the amount of Fe was 0.3 % (mass fraction), the catalyst was found to show both excellent n-hexane aromatization reactivity and higher ability for sulphur-resistance. The dispersion of Pt particles was also found to be better in this bimetallic catalyst, whereas the electron state of Pt particles as indicated by CO-FTIR was modified to be more electron-deficient than that of Pt/KL zeolite, which made the bimetallic Pt-Fe/KL more tolerant to sulphur poisoning.