Study on the Adsorption and Activation of NO and CO over Mixed Oxide Catalysts Containing Cu by Means of TPSR

Adsorption and activation of small molecules NO, CO and CO+ NO on LaSrCuO4, La2CuO4 and La1.7Th0.3CuO4 which are typical samples in the sence of nonstoichiometric oxygen(lambda) anrong the series of La2-x(SrTh)(x)CuO4 +/-lambda mixed oxide catalysts were studied by means of MS- TPD (TPSR ), XRD, chemical analysis and so on. It was shown that the adsorption amount of NO can be correlated with the content of oxygen vacancy while the types and strength of adsorption of NO could be related to the oxidation state of the metallic ion. It was also found that CO molecule was first converted into CO32- and then desorbed in the form of CO2 at high temperature during the adsorption and desorption of CO on the mixed oxide with oxygen vacancy. The fact that the profiles of TPD(TPSR) of NO in co-adsorption of NO+CO and in single NO adsorption are similar shows that the adsorption of NO molecule not only has some priority to that of CO but also is stronger than that of CO. It seems that the adsorption of NO plays a dominate role in the activation and decomposition of NO.

Study on alternating LB films of charge-transfer complex of octadecyl-TCNQ and copper phthalocyanine derivative

Infrared spectra of alternating LB films of octadecyl-TCNQ/CuPc are studied. Charge-transfer complexes are formed in LB films and conductance increases about three orders than that of pure CuPc LB films.

H-1 nmr study on the ring opening selectivity of aromatic dianhydrides towards methanol

Several isomeric aromatic diester-diacids may appear as a result of the opening selectivity of anhydride groups towards the alcohol. H-1 n.m.r. was thus used to characterize the isomeric structure and to quantify the isomer composition. It was found that the isomer ratios quantitatively correlate with electron affinity of bridged dianhydrides and is independent of the alcohol structure used. Furthermore, the H-1 n.m.r chemical shift of bridged diester-diacids was found to be a very sensitive probe of chemical nature of bridged groups and can be used as indices of the opening selectivity. (C) 1997 Elsevier Science Ltd.

A study of the electrochemical characteristics of the Co(salen)-Nafion modified electrode

A Co(salen)-Nafion modified electrode was prepared by immersing a glassy carbon electrode coated with the Nafion film into the aqueous solution with saturated Co(salen), The modified electrode showed a stable electrochemical reaction of Co(salen) at about 0 V(vs, SCE), The result of XPS indicated the valence of cobalt in Co(salen) changes from +2 before to +3 after Co(salen) enters the Nafion film, It is due to forming axis coordination of cobalt with sulfonic group in Nafion film, It was found that the mode of electron transfer in Co(salen)-Nafion modified electrode was controlled by physical diffusion and electron hopping, It was also found that the modified electrode could catalyze the reduction of O-2 to H2O2. The real catalyst may be the adduct of Co-I(salen) and O-2.

Study on the interaction of rare earth with 3,5,3'-triiodothyronine

The stability constants for rare earth complexes with 3,5,3'-triiodothyronine were determined at 37 degrees C end an ionic strength of 0.15 mole/L NaCl. The lanthanide induced shifts were measured for H-1 nuclei of 3,5,3'-triiodothyronine. The coordination of rare earth with 3, 5, 3'-triiodothyronine was discussed.

Ab initio study of C-9 and LaC9+ clusters

The energies and geometries of C-9 and LaC9+ clusters were calculated at HF, MP2 and DFT levels. For C-9, all theoretical levels show that the linear chain is the most stable structure. For LaC9+, two isomers were considered. In the first case La has two single bonds (A), while it forms a double bond in the second (B). Our results showed that in HF calculation, B is marginally more stable than A, while for MP2 and DFT, A is favored. Our results also revealed that there is not enough space for C-9 ring to accommodate lanthanum. Our conclusion agrees well with experiment.

Study on the microstructure and properties of nanosized stannic oxide powders

Stannic oxide xerogel was prepared by a forced hydrolysis method using SnCl4 as the precursor. The average grain sizes of the nanosized stannic oxide powders varied with the sintering temperatures. The powders were characterized by several different physico-chemical techniques. TEM was employed for the direct observation on grain sizes, shape and state of aggregation of the particles. XRD technique was used for the determination of the crystalline structure. Microstructural parameters of average crystallite size () and mean-square root microstrain (epsilon(2)>(1/2)) for the samples were calculated from the broadened values of the half-peak intensity of XRD. The atomic ratio between oxygen and tin in the surface region of the particles was estimated through the analysis of XPS. Attributing to lots of oxygen vacancies in the surface region of the nanoparticulates and the 'trapped electrons' in the vacancies, an ESR signal was observed in the sample sintered at 300 degrees C for 2 h. FTIR of the powders showed that intensity of the transverse optical mode of Sn-O stretching vibration increased with the sintering temperature while the bending vibration of O-Sn-O showed a blue shift. For Raman spectra, very important spectral characteristics such as variations of intensity and width of the bands were observed. A new Raman vibrational band located at 572 cm(-1) was identified in the samples of nanosized stannic oxide powders. Variation of these spectroscopic properties were strongly affected by grain size, shape and state of aggregation of the nanosized particulates.

Study on the beta relaxation mechanism of thermosetting polyimide thermoplastic polyimide blends

The thermosetting polyimide PMR-I5 and its blends with thermoplastic polyimides have been studied by dynamic mechanical analysis. The results obtained indicate that the level of beta relaxations in PMR-15 are increased with an increase in cross-linking density. This phenomenon is interpreted as a change of chemical structure during the cross-linking process. Addition of thermoplastic polyimide makes the magnitude of beta relaxations increase when PMR-15 is the major component. This might be due to the strong intermolecular charge-transfer interaction between PI and PI or PMR-15 and PMR-15 molecular chains being partly replaced by the weak intermolecular interaction between PI and PMR-15 in PMR-15/PI blends, resulting in some phenylene rings or imide groups in PIs and PMR-15 chains being able to participate in beta relaxation. However, this increment in beta relaxation magnitude can be reduced by heat treatment of the sample, as a result of phase separation. Hence, it is concluded that the beta relaxation magnitude is determined by the number of groups which can participate in relaxation per unit length, i.e. the magnitude of beta relaxation increases with decreasing interaction between the molecular chains. Copyright (C) 1996 Elsevier Science Ltd

An ESR study on (OH)-O-center dot-radical scavenging activity of water-soluble fullerenols

Water-soluble polyhydroxylated fullerene derivatives (fullerenol) were synthesized, and their scavenging ability for (OH)-O-.-radical was studied by the combination of ESR spectroscopy and spin-trapping technique with phenyl-t-butyl-nitrone. It was found that fullerenols showed an excellent efficiency in eliminating (OH)-O-. free radicals generated by UV photolysis of H2O2. At an applied fullerenol concentration of 0, 3 mg/mL in the final solution, a radical scavenging efficiency of approximate 95% was achieved, revealing the potential use of these compounds as novel potent free radical scavengers in biological systems.

ESCA study of dichlorozirconocene/methylaluminoxane olefin polymerization catalyst system

An investigation has been undertaken by use of ESCA in the characterization of the central metal(Zr) of dichlorozirconocene/methylaluminoxane homogeneous olefin polymerization catalyst. The change of electron density shown by a shift in ESCA signals (181.8 - 182.7eV) indicates that the catalytic species are ''cation-like''. Within the range of detecting sensitivity of ESCA spectrometer, only a part of the new catalytic derivative was formed. The influence of complexion time and Al : Zr ratio on the formation of the catalytic zirconocene cation has also been investigated.

Study on the UCST and LCST in PHB/PBHE-solvent system

Upper and lower critical solution temperature (UCST and LCST) behaviours have been examined for solution of PHB/PBHE blends in chloroform and chlorobenzene. Polymer-Solvent systems prepared with various solvents and concentrations were found to possess UCST and LCST characteristics. PHB/PBHE solution in chloroform displayed greater miscibility temperature region than that of the blend in chlorobenzene, but the relative tendency of both UCST and LCST were similar.

Comparative study of Nickel-based perovskite-like mixed oxide catalysts for direct decomposition of NO

The mixed oxides LaNiO3, La0.1Sr0.9NiO3, La2NiO4 and LaSrNiO4 were prepared and used as catalysts for the direct decomposition of NO. The catalysts were characterized by means of XRD, XPS, O-2-TPD, NO-TPD and chemical analysis. By comparing the physico-chemical properties and catalytic activity for NO decomposition, a conclusion could be drawn as follows. The direct decomposition of NO over perovskite and related mixed oxide catalysts follows a redox mechanism. The lower valent metal ions Ni2+ and disordered oxygen vacancies seem to be the active sites in the redox process. The oxygen vacancy plays an important role favorable for the adsorption and activation of NO molecules on one hand and on the other hand for increasing the mobility of lattice oxygen which is beneficial to the reproduction of active sites. The presence of oxygen vacancies is one of the indispensable factors to give the mixed oxides a steady activity for NO decomposition.

A theoretical study on the nonlinear optical second-order properties of azobenzene series molecules

On the basis of AM1 and INDO/CI methods, we devise the program for the calculation of nonlinear second-order optical susceptibilities beta(ijk) and perform systematic theoretical studies on the nonlinear optical second-order properties of azobenzene series molecules, i. e. on the basis of [GRAPHICS] we induced different donors on the left side of phenyl ring, and different accepters on the right side of phenyl ring, and examined the rule of beta variation. The regularity summarized from the calculated results has been explained micromechanically. Finally, a molecule having a big nonlinear second-order optical susceptibility has been designed.

Probe beam deflection study of the ion exchange between Prussian blue film or indium hexacyanoferrate film and electrolyte solutions

Probe beam deflection(PBD) technique together with electrochemical techniques such as cyclic voltammetry was used to study the ion exchange in prussian blue(PB) film and its analogue indium hexacyanoferrate (InHCF) chemically modified electrodes, The ion exchange mechanism of PB was verified as following: K2Fe2+FeI(CN)(6)(-e--K+)reversible arrow(+e-+K+)KFe(3+)Fe(I)(CN)(6)(-xe--xK+)reversible arrow(+xe-+xK+) [Fe3+FeI(CN)(6)](x)[KFe3+FeI(CN)(6)](1-x) where on reduction in contact with an acidic KCl electrolyte, H+ enter PB film before K+. Both the cations and anions participate concurrently in the redox process of InHCF, meanwhile K+ ion plays a major role in the whole charge transfer process of this film with increasing radii of anions.

A study of the radical reaction of C-60 with n-Bu(3)SnH

The reaction of buckministerfullerene (C-60) with tri-n-blltyltin hydride(n-Bu(3)SnH) in toluene solution has been investigated. According to mass spectrometry analysis, the products of above reaction are C-60(BuH)(n)(n = 1 similar to 3) and Bu(x)Sn(y)H(x) (x = 3 similar to 8, y = 1 similar to 4,approximate to = 0 similar to 3). The reaction maybe provide a new method for the synthesis of alkylated fullerene derivatives. Where C-60 also takes a role of a catalysis of organtic-tin polymerization. The radical reaction mechanism has been discussed.