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2007 Volume 23 Issue 9
2007, 23(09):
Abstract:
2007, 23(09): 1311-1315
doi: 10.1016/S1872-1508(07)60064-3
Abstract:
Ni-B amorphous catalyst supported by chitosan (CS)-modified silica(Ni-B/CS/SiO2) was prepared using the impregnation-reduction method. The as-prepared catalysts were characterized using X-ray powder diffraction (XRD), fourier transform infrared (FTIR) spectra, inductively coupled plasma (ICP) spectrometer, Brunauter-Emmett-Teller (BET) method, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The results showed that the particle sizes, the surface content of Ni active species, and catalytic activity were improved by introducing chitosan to the surface of silica. In the hydrogenation of furfuryl alcohol (FA) to tetrafurfural alcohol (THFA), the amorphous Ni-B/CS/SiO2 catalyst exhibited superior catalytic activity to the corresponding traditional Ni-B/SiO2 amorphous catalyst and Raney Ni.
Ni-B amorphous catalyst supported by chitosan (CS)-modified silica(Ni-B/CS/SiO2) was prepared using the impregnation-reduction method. The as-prepared catalysts were characterized using X-ray powder diffraction (XRD), fourier transform infrared (FTIR) spectra, inductively coupled plasma (ICP) spectrometer, Brunauter-Emmett-Teller (BET) method, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The results showed that the particle sizes, the surface content of Ni active species, and catalytic activity were improved by introducing chitosan to the surface of silica. In the hydrogenation of furfuryl alcohol (FA) to tetrafurfural alcohol (THFA), the amorphous Ni-B/CS/SiO2 catalyst exhibited superior catalytic activity to the corresponding traditional Ni-B/SiO2 amorphous catalyst and Raney Ni.
2007, 23(09): 1316-1320
doi: 10.1016/S1872-1508(07)60065-5
Abstract:
The decomposition reaction kinetics of the double-base (DB) rocket propellant composed of the mixed ester of triethyleneglycol dinitrate (TEGDN) and nitroglycerin (NG), and nitrocellulose (NC) with lanthanumcitrate as a combustion catalyst was investigated by thermogravimetry and differential thermogravimetry (TG-DTG), and differential scanning calorimetry (DSC) under atmospheric pressure and flowing nitrogen gas conditions. The results showed that the thermal decomposition processes of DB propellant had two mass loss stages: volatilization and decomposition of the mixed ester in the first-stage and exothermic decomposition reaction in the second-stage. The exothermic decomposition reaction mechanism obeyed the third-order chemical reaction rule. The kinetic parameters of the reaction were: Ea=231.14 kJ·mol-1, A=1023.29 s-1. The kinetic equation can be expressed as: dα/dt=1022.99(1-α)3e-2.78×104/T. The critical temperatures of the thermal explosion of the DB propellant obtained from the onset temperature (Te) and the peak temperature (Tp) were: Tbe=463.62 K, Tbp=477.88 K. The entropy of activation (⊿S≠), enthalpy of activation (⊿H≠), and free energy of activation (⊿G≠) of the reaction were 219.75 J·mol-1·K-1, 239.23 kJ·mol-1, and 135.96 kJ·mol-1, respectively.
The decomposition reaction kinetics of the double-base (DB) rocket propellant composed of the mixed ester of triethyleneglycol dinitrate (TEGDN) and nitroglycerin (NG), and nitrocellulose (NC) with lanthanumcitrate as a combustion catalyst was investigated by thermogravimetry and differential thermogravimetry (TG-DTG), and differential scanning calorimetry (DSC) under atmospheric pressure and flowing nitrogen gas conditions. The results showed that the thermal decomposition processes of DB propellant had two mass loss stages: volatilization and decomposition of the mixed ester in the first-stage and exothermic decomposition reaction in the second-stage. The exothermic decomposition reaction mechanism obeyed the third-order chemical reaction rule. The kinetic parameters of the reaction were: Ea=231.14 kJ·mol-1, A=1023.29 s-1. The kinetic equation can be expressed as: dα/dt=1022.99(1-α)3e-2.78×104/T. The critical temperatures of the thermal explosion of the DB propellant obtained from the onset temperature (Te) and the peak temperature (Tp) were: Tbe=463.62 K, Tbp=477.88 K. The entropy of activation (⊿S≠), enthalpy of activation (⊿H≠), and free energy of activation (⊿G≠) of the reaction were 219.75 J·mol-1·K-1, 239.23 kJ·mol-1, and 135.96 kJ·mol-1, respectively.
2007, 23(09): 1321-1324
doi: 10.1016/S1872-1508(07)60066-7
Abstract:
The adsorption properties of middle molecular weight toxins on two types of carbon nanotubes (CNTs) (i.e., multi-walled carbon nanotubes (MWCNTs) and aligned multi-walled carbon nanotubes (ACNTs)) were studied and compared with two commercial haemoadsorbents (i.e., activated carbon (AC) and macroporous resin (MR)). The results showed that it took only 10 and 15 min for MWCNTs and ACNTs to achieve the adsorption equilibrium, respectively. The adsorption amount of MWCNTs reached 47.18 mg·g -1, which was 5.5 and 10.8 times of that of macroporous resin and activated carbon, respectively. Pore structure analyses indicated that the high adsorption efficiency should be attributed to the higher mesopore volumes of CNTs. All of the results implied the great potential applications of CNTs in haemoperfusion (HP).
The adsorption properties of middle molecular weight toxins on two types of carbon nanotubes (CNTs) (i.e., multi-walled carbon nanotubes (MWCNTs) and aligned multi-walled carbon nanotubes (ACNTs)) were studied and compared with two commercial haemoadsorbents (i.e., activated carbon (AC) and macroporous resin (MR)). The results showed that it took only 10 and 15 min for MWCNTs and ACNTs to achieve the adsorption equilibrium, respectively. The adsorption amount of MWCNTs reached 47.18 mg·g -1, which was 5.5 and 10.8 times of that of macroporous resin and activated carbon, respectively. Pore structure analyses indicated that the high adsorption efficiency should be attributed to the higher mesopore volumes of CNTs. All of the results implied the great potential applications of CNTs in haemoperfusion (HP).
2007, 23(09): 1325-1331
doi: 10.1016/S1872-1508(07)60067-9
Abstract:
A three-dimensional pharmacophore model was developed for a considerable number of pyrrolidine-based and butane-based chemokine (C-C motif) receptor 5(CCR5) anta nists, which can block the entry of human immunodeficiency virus type 1 (HIV-1) by inhibiting the interaction of HIV-1 envelope protein and CCR5. The pharmacophore model was generated using a training set consisting of 25 carefully selected anta nists with the diverse molecular architecture and bioactivity, as required by the Catalyst/HypoGen program. The activity of the training set molecules expressed in IC50 ( half-inhibitory concentration) covered from 0.06 to 10000 nmol·L-1. The most predictive pharmacophore model (Hypo 1), consisting of two positive ionizable points and three hydrophobic groups, had a correlation of 0.924 and a root mean square of 1.068, and a cost difference of 63.67 bits between the null cost and the total cost. The model was applied in predicting the activity of 74 compounds as a test set. The results indicated that the model was able to provide clear guidelines and accurate activity prediction for novel anta nist design.
A three-dimensional pharmacophore model was developed for a considerable number of pyrrolidine-based and butane-based chemokine (C-C motif) receptor 5(CCR5) anta nists, which can block the entry of human immunodeficiency virus type 1 (HIV-1) by inhibiting the interaction of HIV-1 envelope protein and CCR5. The pharmacophore model was generated using a training set consisting of 25 carefully selected anta nists with the diverse molecular architecture and bioactivity, as required by the Catalyst/HypoGen program. The activity of the training set molecules expressed in IC50 ( half-inhibitory concentration) covered from 0.06 to 10000 nmol·L-1. The most predictive pharmacophore model (Hypo 1), consisting of two positive ionizable points and three hydrophobic groups, had a correlation of 0.924 and a root mean square of 1.068, and a cost difference of 63.67 bits between the null cost and the total cost. The model was applied in predicting the activity of 74 compounds as a test set. The results indicated that the model was able to provide clear guidelines and accurate activity prediction for novel anta nist design.
2007, 23(09): 1332-1336
doi: 10.1016/S1872-1508(07)60068-0
Abstract:
The structures of spermwhale myoglobin (Mb) and mutants were investigated in terms of the ABEEM/MM method. The molecular dynamic simulations showed that the bifurcated hydrogen-bondings in the proximal side of the heme in Mb were not stable. These simulations indicated that hydrogen-bondings could not determine the overall orientation of imidazole, which could be related to the histidine residue. The amide acids and the bulk of the imidazole can have effects on the flexibility of proximal ligands.
The structures of spermwhale myoglobin (Mb) and mutants were investigated in terms of the ABEEM/MM method. The molecular dynamic simulations showed that the bifurcated hydrogen-bondings in the proximal side of the heme in Mb were not stable. These simulations indicated that hydrogen-bondings could not determine the overall orientation of imidazole, which could be related to the histidine residue. The amide acids and the bulk of the imidazole can have effects on the flexibility of proximal ligands.
2007, 23(09): 1337-1341
doi: 10.1016/S1872-1508(07)60069-2
Abstract:
Absorption and excited state intramolecular proton transfer (ESIPT) fluorescence of 2’-ethylhexyl salicylate (EHS) were examined in the presence of cationic, non-ionic, and anionic surfactants. It was found that linear EHS molecule was solubilized in micelles with its flexible hydrophobic 2’-ethylhexyl chain toward the micellar core and with its rigid salicylate moiety toward the micelle-water interface. The UV absorbance of EHS was improved and intramolecular hydrogen bonding formation of EHS was favored, resulting in greatly enhanced ESIPT fluorescence. The excited EHS molecules decay via visible luminescence and non-radiative deactivation. The binding sites of EHS in micelles were explained at a molecular level in terms of molecular structures and sizes of EHS and surfactants. Dynamic fluorescence quenching and spectral measurements of ester hydrolysis of EHS provide further evidences for the binding sites of EHS in different micelles.
Absorption and excited state intramolecular proton transfer (ESIPT) fluorescence of 2’-ethylhexyl salicylate (EHS) were examined in the presence of cationic, non-ionic, and anionic surfactants. It was found that linear EHS molecule was solubilized in micelles with its flexible hydrophobic 2’-ethylhexyl chain toward the micellar core and with its rigid salicylate moiety toward the micelle-water interface. The UV absorbance of EHS was improved and intramolecular hydrogen bonding formation of EHS was favored, resulting in greatly enhanced ESIPT fluorescence. The excited EHS molecules decay via visible luminescence and non-radiative deactivation. The binding sites of EHS in micelles were explained at a molecular level in terms of molecular structures and sizes of EHS and surfactants. Dynamic fluorescence quenching and spectral measurements of ester hydrolysis of EHS provide further evidences for the binding sites of EHS in different micelles.
2007, 23(09): 1342-1346
doi: 10.1016/S1872-1508(07)60070-9
Abstract:
Comparing with pure copper, the corrosion behavior of copper clad laminate (CCL) in NaCl solution was studied by using linear polarization, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It was shown that CCL had a different corrosion behavior and showed a lower corrosion resistance compared with the pure copper. At low polarization potential, CCL dissolves through the formation of CuCl-2 , which may be a determined step in the anodic process. And when the polarization potential increased, a porous filmcontaining CuCl formed on the CCL surface, and the transportation of Cl- in the film became the controlling step in the corrosion process. An inductive loop at low frequency was observed in the EIS measurement, which was attributed to the modulation of CuCl film due to the competition between dissolution and growth processes on CCL surface.
Comparing with pure copper, the corrosion behavior of copper clad laminate (CCL) in NaCl solution was studied by using linear polarization, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It was shown that CCL had a different corrosion behavior and showed a lower corrosion resistance compared with the pure copper. At low polarization potential, CCL dissolves through the formation of CuCl-2 , which may be a determined step in the anodic process. And when the polarization potential increased, a porous filmcontaining CuCl formed on the CCL surface, and the transportation of Cl- in the film became the controlling step in the corrosion process. An inductive loop at low frequency was observed in the EIS measurement, which was attributed to the modulation of CuCl film due to the competition between dissolution and growth processes on CCL surface.
2007, 23(09): 1347-1352
doi: 10.3866/PKU.WHXB20070908
Abstract:
TiO2 nano-crystalline films on Al substrate were prepared from tetra-n-butyl titanate by sol-gel method. The synthesized TiO2 films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The photodegradation activity of methylene blue (MB) solutions under UV irradiation was studied. The results indicated that the TiO2 particles could be built up from crystallites ranging from 10 nm to 20 nm and had a dense bonding. The interface diffusion between TiO2 and Al substrate takes place at calcination temperature of 450 ℃ for 30 min and Al element diffuses into TiO2 film from Al substrate, forming a diffusion layer with a thickness of about 75 nm. The interface diffusion between TiO2 and Al substrate leaded to the inferior photocatalytic activity. The influence of Al substrate on photodegradation activity of MB solutions became less and less as the thickness of the thin filmincreased.
TiO2 nano-crystalline films on Al substrate were prepared from tetra-n-butyl titanate by sol-gel method. The synthesized TiO2 films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The photodegradation activity of methylene blue (MB) solutions under UV irradiation was studied. The results indicated that the TiO2 particles could be built up from crystallites ranging from 10 nm to 20 nm and had a dense bonding. The interface diffusion between TiO2 and Al substrate takes place at calcination temperature of 450 ℃ for 30 min and Al element diffuses into TiO2 film from Al substrate, forming a diffusion layer with a thickness of about 75 nm. The interface diffusion between TiO2 and Al substrate leaded to the inferior photocatalytic activity. The influence of Al substrate on photodegradation activity of MB solutions became less and less as the thickness of the thin filmincreased.
2007, 23(09): 1353-1359
doi: 10.1016/S1872-1508(07)60071-0
Abstract:
Benesi-Hildebrand (B-H) method is a widely used approach for determining the stoichiometry and equilibrium constants of nonbonded interactions, particularly 1:1 and 1:2 interactions. Using computer simulation, it was shown that, under certain conditions, the approach could generate inappropriate stoichiometric conclusions for 1:2 interactions. This problemcould occur in the cases of both weak and strong interactions, where the 1:1 B-H plots showed a linear feature and the 1:2 B-H plots showed a nonlinear feature. In addition, effect of the initial concentrations on the accurate evaluation of equilibrium constants of 1:1 interactions was investigated. It was found that the minimum safe concentration ratio r0 between ligand and central species was 100. However, for weak nonbonding interactions, for example K<25 L·mol-1 (C0P=4×10-4 mol·L-1), the ratio r0 has no limitation. Two conditions proposed in literatures for the safe application of the B-H method were examined. It was found that the inequation, 1/(KC0P)≥10, was a condition to secure CB/C0B≥91%. The other inequation, KC0B≥0.1, was not found to be the safe condition to validate the B-H method.
Benesi-Hildebrand (B-H) method is a widely used approach for determining the stoichiometry and equilibrium constants of nonbonded interactions, particularly 1:1 and 1:2 interactions. Using computer simulation, it was shown that, under certain conditions, the approach could generate inappropriate stoichiometric conclusions for 1:2 interactions. This problemcould occur in the cases of both weak and strong interactions, where the 1:1 B-H plots showed a linear feature and the 1:2 B-H plots showed a nonlinear feature. In addition, effect of the initial concentrations on the accurate evaluation of equilibrium constants of 1:1 interactions was investigated. It was found that the minimum safe concentration ratio r0 between ligand and central species was 100. However, for weak nonbonding interactions, for example K<25 L·mol-1 (C0P=4×10-4 mol·L-1), the ratio r0 has no limitation. Two conditions proposed in literatures for the safe application of the B-H method were examined. It was found that the inequation, 1/(KC0P)≥10, was a condition to secure CB/C0B≥91%. The other inequation, KC0B≥0.1, was not found to be the safe condition to validate the B-H method.
2007, 23(09): 1360-1364
doi: 10.1016/S1872-1508(07)60072-2
Abstract:
The size consistency of the multireference perturbation theory and multireference singly-excited and doubly-excited configuration interaction (MRSDCI) was investigated numerically with three super-molecular models composed of H2, He, and LiH monomers separated by a large distance. A small full configuration interaction was performed first over the model space and then multireference perturbation calculations were carried out. Numerical results demonstrated that the previously derived size consistent multireference second-order perturbation theory was size consistent with respect to the above three super-molecules. Its accuracy relative to the full configuration interaction (CI) was also discussed. Size consistent error of two sets of the multireference second-order and third-order perturbation theories as well as MRSDCI were studied and compared.
The size consistency of the multireference perturbation theory and multireference singly-excited and doubly-excited configuration interaction (MRSDCI) was investigated numerically with three super-molecular models composed of H2, He, and LiH monomers separated by a large distance. A small full configuration interaction was performed first over the model space and then multireference perturbation calculations were carried out. Numerical results demonstrated that the previously derived size consistent multireference second-order perturbation theory was size consistent with respect to the above three super-molecules. Its accuracy relative to the full configuration interaction (CI) was also discussed. Size consistent error of two sets of the multireference second-order and third-order perturbation theories as well as MRSDCI were studied and compared.
2007, 23(09): 1365-1369
doi: 10.3866/PKU.WHXB20070911
Abstract:
MnO2 particles in the size less than 200 nm were prepared via the oxidation of MnSO4 using KMnO4 as oxidizer. The printing‘ink’was prepared by mixing MnO2 particles with acetylene black, dispersion additive Lomar-D, ethanolamine, binder CMCS and distilled water in the mass ratio of 200:40:4:1:1:4000, and dispersing under ultrasonic. The ultra thin MnO2 film electrodes were prepared by means of computer jet printing technique using this‘ink’. The SEMimages showed that the surface of the ultra thin MnO2 filmelectrode was uniform, and its thickness was about 2.5 μm. In 1 mol·L-1 Li2SO4 solution the electrodes present typical electrochemical supercapacitance behavior observed by voltammetry and charge-discharge measurements, in the potential region of 0-0.85 V(vs SCE). Its specific capacitance reached to 154 F·g-1 at the discharge current of 9.4 A·g-1, and remained almost no change after 2000 cycles.
MnO2 particles in the size less than 200 nm were prepared via the oxidation of MnSO4 using KMnO4 as oxidizer. The printing‘ink’was prepared by mixing MnO2 particles with acetylene black, dispersion additive Lomar-D, ethanolamine, binder CMCS and distilled water in the mass ratio of 200:40:4:1:1:4000, and dispersing under ultrasonic. The ultra thin MnO2 film electrodes were prepared by means of computer jet printing technique using this‘ink’. The SEMimages showed that the surface of the ultra thin MnO2 filmelectrode was uniform, and its thickness was about 2.5 μm. In 1 mol·L-1 Li2SO4 solution the electrodes present typical electrochemical supercapacitance behavior observed by voltammetry and charge-discharge measurements, in the potential region of 0-0.85 V(vs SCE). Its specific capacitance reached to 154 F·g-1 at the discharge current of 9.4 A·g-1, and remained almost no change after 2000 cycles.
2007, 23(09): 1370-1374
doi: 10.3866/PKU.WHXB20070912
Abstract:
In order to fabricate WC/CNT nanocomposite, carbon nanotubes (CNTs) were first surface decorated by carboxy groups, and tungsten ionic groups were decorated on the surface of carbon nanotube through carboxy groups, then the tungsten ionic groups were reduced into tungsten carbide by an approach of in situ reduction and carbonization. The samples were characterized by FTIR, XRD, SEM, HRTEM, and N2 adsorption. FTIR and N2 adsorption results showed that the decorated carbon nanotube was of carboxylation, while its specific surface area increased. XRD results showed that the sample was composed of tungsten carbide (WC), carbon nanotube and non-stoichiometric tungsten oxide. SEMand HRTEMresults showed that the tungsten carbide nanoparticles with irregular granular laid on the outer surface of carbon nanotube homogenously. The electrocatalytic activity of the samples was tested by powder-microelectrode, and the results showed that the electrocatalytic activity of the sample for methanol oxidation in basic solution was higher than that of hollow microsphere tungsten carbide with mesoporosity and purified carbon nanotube.
In order to fabricate WC/CNT nanocomposite, carbon nanotubes (CNTs) were first surface decorated by carboxy groups, and tungsten ionic groups were decorated on the surface of carbon nanotube through carboxy groups, then the tungsten ionic groups were reduced into tungsten carbide by an approach of in situ reduction and carbonization. The samples were characterized by FTIR, XRD, SEM, HRTEM, and N2 adsorption. FTIR and N2 adsorption results showed that the decorated carbon nanotube was of carboxylation, while its specific surface area increased. XRD results showed that the sample was composed of tungsten carbide (WC), carbon nanotube and non-stoichiometric tungsten oxide. SEMand HRTEMresults showed that the tungsten carbide nanoparticles with irregular granular laid on the outer surface of carbon nanotube homogenously. The electrocatalytic activity of the samples was tested by powder-microelectrode, and the results showed that the electrocatalytic activity of the sample for methanol oxidation in basic solution was higher than that of hollow microsphere tungsten carbide with mesoporosity and purified carbon nanotube.
2007, 23(09): 1375-1380
doi: 10.3866/PKU.WHXB20070913
Abstract:
The influence of supports on the preparation of TiO2 nanoparticles in adsorption phase nanoreactor formed by the adsorption layer on silica surface was studied. Series temperature experiments of two types of supports (support A: size 20 nm, specific surface area 640 m2·g-1; support SiO2 B: size 12 nm, surface area 200 m2·g-1) were designed. Electronic energy spectrum indicated that the concentration of TiO2 on the two supports both decreased with temperature increasing. TiO2 quantity on support A decreased sharply between 40-60 ℃, whereas the coresponding temperature range for support B was between 30-50 ℃. TiO2 particles on support B were more uniform than those on support A in TEM. The grain size curve by XRD suggested that size of TiO2 particles on support A reduced with temperature rising and there was also a sharp decrease as in quantity curve of TiO2, but TiO2 particles on support B had a substantially constant size. Based on the characteristics of adsorption on silica surface, the generality of adsorption on SiO2 was proposed to explain the same changes in Ti concentration on different supports. The different characteristics of internal/external surface induced variant temperature-sensitivities and characteristics of adsorption on support surface. Moreover these different adsorptions led variance of content and grain size, as well as characteristics of TiO2 on the two types of supports.
The influence of supports on the preparation of TiO2 nanoparticles in adsorption phase nanoreactor formed by the adsorption layer on silica surface was studied. Series temperature experiments of two types of supports (support A: size 20 nm, specific surface area 640 m2·g-1; support SiO2 B: size 12 nm, surface area 200 m2·g-1) were designed. Electronic energy spectrum indicated that the concentration of TiO2 on the two supports both decreased with temperature increasing. TiO2 quantity on support A decreased sharply between 40-60 ℃, whereas the coresponding temperature range for support B was between 30-50 ℃. TiO2 particles on support B were more uniform than those on support A in TEM. The grain size curve by XRD suggested that size of TiO2 particles on support A reduced with temperature rising and there was also a sharp decrease as in quantity curve of TiO2, but TiO2 particles on support B had a substantially constant size. Based on the characteristics of adsorption on silica surface, the generality of adsorption on SiO2 was proposed to explain the same changes in Ti concentration on different supports. The different characteristics of internal/external surface induced variant temperature-sensitivities and characteristics of adsorption on support surface. Moreover these different adsorptions led variance of content and grain size, as well as characteristics of TiO2 on the two types of supports.
2007, 23(09): 1381-1386
doi: 10.3866/PKU.WHXB20070914
Abstract:
Reduction of RuCl3·3H2O with hydrogen in ionic liquid [BMIM]BF4(1-butyl-3-methylimidazolium tetrafluoroborate) or [BMIM][p-CH3C6H4SO3] (1-butyl-3-methylimidazolium p-methylphenylsulfonate) medium using P(m-C6H4SO3Na)3 (TPPTS) as stabilizer yielded ruthenium nanoparticles. Further treatment of the Ru nanoparticles with chiral modifier (1S, 2S)-1,2-diphenyl-1,2-ethylene-diamine((1S, 2S)-DPEN) and KOHin ionic liquid/i-PrOH mixed solvent resulted in a novel immobilized chiral catalyst which can asymmetrically hydrogenate acetophenone and its derivatives. 100%conversion and 79.1%ee (enantiomeric excess) were obtained for acetophenone under optimized conditions. The catalyst immobilized in ionic liquid not only exhibits excellent reactivities and enantioselectivities in asymmetric hydrogenation of acetophenone and its derivatives, but also can be recycled and reused by simple extraction with n-hexane.
Reduction of RuCl3·3H2O with hydrogen in ionic liquid [BMIM]BF4(1-butyl-3-methylimidazolium tetrafluoroborate) or [BMIM][p-CH3C6H4SO3] (1-butyl-3-methylimidazolium p-methylphenylsulfonate) medium using P(m-C6H4SO3Na)3 (TPPTS) as stabilizer yielded ruthenium nanoparticles. Further treatment of the Ru nanoparticles with chiral modifier (1S, 2S)-1,2-diphenyl-1,2-ethylene-diamine((1S, 2S)-DPEN) and KOHin ionic liquid/i-PrOH mixed solvent resulted in a novel immobilized chiral catalyst which can asymmetrically hydrogenate acetophenone and its derivatives. 100%conversion and 79.1%ee (enantiomeric excess) were obtained for acetophenone under optimized conditions. The catalyst immobilized in ionic liquid not only exhibits excellent reactivities and enantioselectivities in asymmetric hydrogenation of acetophenone and its derivatives, but also can be recycled and reused by simple extraction with n-hexane.
2007, 23(09): 1387-1392
doi: 10.3866/PKU.WHXB20070915
Abstract:
La1-xCuxMnO3 (x=0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5) catalysts were synthesized by amorphous heteronuclear complexingmethod. The catalystswere characterized by XRD, TEM, andN2 adsorption isotherms. The cataluminescence (CTL) response to CO and the activities in the oxidation of CO and CH4 over the catalysts were investigated. XRD analysis indicated that the single-phase perovskite crystals were formed at x≤0.1, but perovskite and CuO phases coexisted at x>0.1. The catalytic activities of La1-xCuxMnO3 catalysts were superior to those of LaMnO3 catalysts for CO oxidation. La0.9Cu0.1MnO3 (calcined at 700 ℃ for 3 h) catalyst showed the highest catalytic activity for CO oxidation (T100%= 170 ℃), which agreed well with the cataluminescence results. However, La0.95Cu0.05MnO3 catalyst showed the highest catalytic activity for CH4 oxidation (T95%=705 ℃).
La1-xCuxMnO3 (x=0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5) catalysts were synthesized by amorphous heteronuclear complexingmethod. The catalystswere characterized by XRD, TEM, andN2 adsorption isotherms. The cataluminescence (CTL) response to CO and the activities in the oxidation of CO and CH4 over the catalysts were investigated. XRD analysis indicated that the single-phase perovskite crystals were formed at x≤0.1, but perovskite and CuO phases coexisted at x>0.1. The catalytic activities of La1-xCuxMnO3 catalysts were superior to those of LaMnO3 catalysts for CO oxidation. La0.9Cu0.1MnO3 (calcined at 700 ℃ for 3 h) catalyst showed the highest catalytic activity for CO oxidation (T100%= 170 ℃), which agreed well with the cataluminescence results. However, La0.95Cu0.05MnO3 catalyst showed the highest catalytic activity for CH4 oxidation (T95%=705 ℃).
2007, 23(09): 1393-1398
doi: 10.3866/PKU.WHXB20070916
Abstract:
The quantitative structure-activity relationships (QSAR) of a series of human immunodeficiency virus type 1 (HIV-1) integrase inhibitors of the derivatives of diketone acids (DKAs) were investigated using genetic function approximation (GFA) and moleculor field analysis (MFA) models and then validated by F-test and predictive-ability test. The r2pred of these two models reached 0.987 and 0.759, respectively, which demonstrated that the models had perfect predictive ability. Furthermore pharmocophore analysis was used to confirm the models and demonstrate the importance of hydrophobic interactions. Based on the above conclusions, three new molecules of DKAs with higher activity have been theoretically designed and are waiting for support from experiment. The findings in this research will give some guidance for designing novel effective HIV-1 integrase inhibitors.
The quantitative structure-activity relationships (QSAR) of a series of human immunodeficiency virus type 1 (HIV-1) integrase inhibitors of the derivatives of diketone acids (DKAs) were investigated using genetic function approximation (GFA) and moleculor field analysis (MFA) models and then validated by F-test and predictive-ability test. The r2pred of these two models reached 0.987 and 0.759, respectively, which demonstrated that the models had perfect predictive ability. Furthermore pharmocophore analysis was used to confirm the models and demonstrate the importance of hydrophobic interactions. Based on the above conclusions, three new molecules of DKAs with higher activity have been theoretically designed and are waiting for support from experiment. The findings in this research will give some guidance for designing novel effective HIV-1 integrase inhibitors.
2007, 23(09): 1399-1404
doi: 10.3866/PKU.WHXB20070917
Abstract:
Ordered mesoporous carbon materials were successfully synthesized by an easy method of the carbonization of sulfuric-acid-treated silica/triblock copolymer/sucrose composites. The morphologies, structures and pore characteristics of the carbon materials were investigated by X-ray diffraction (XRD), nitrogen adsorption desorption and transmission electron microscopy (TEMand HRTEM) measurements. On the basis of comparing the surface areas and pore properties of two ordered mesoporous carbons obtained by changing the content of the reactants, their electrochemical hydrogen storage capacities were tested by Galvanostatic charge-discharge measurement. The results showed that the carbon material (C-P) with higher specific surface area (720 m2·g-1) and pore volume (0.86 cm3·g-1) had higher hydrogen storage capacity (70.1 mAh·g-1) than the carbon material (C-S) (64.1 mAh·g-1) with lower specific surface area (610 m2·g-1) and pore volume (0.66 cm3·g-1). Both of the two ordered mesoporous carbons exhibited higher hydrogen storage capacities than the single-walled carbon nanotubes (25.9 mAh·g-1). The cyclic voltammetry measurement indicated that the ordered mesoporous carbon electrode possessed higher electrochemical activity than single-walled carbon nanotubes electrode.
Ordered mesoporous carbon materials were successfully synthesized by an easy method of the carbonization of sulfuric-acid-treated silica/triblock copolymer/sucrose composites. The morphologies, structures and pore characteristics of the carbon materials were investigated by X-ray diffraction (XRD), nitrogen adsorption desorption and transmission electron microscopy (TEMand HRTEM) measurements. On the basis of comparing the surface areas and pore properties of two ordered mesoporous carbons obtained by changing the content of the reactants, their electrochemical hydrogen storage capacities were tested by Galvanostatic charge-discharge measurement. The results showed that the carbon material (C-P) with higher specific surface area (720 m2·g-1) and pore volume (0.86 cm3·g-1) had higher hydrogen storage capacity (70.1 mAh·g-1) than the carbon material (C-S) (64.1 mAh·g-1) with lower specific surface area (610 m2·g-1) and pore volume (0.66 cm3·g-1). Both of the two ordered mesoporous carbons exhibited higher hydrogen storage capacities than the single-walled carbon nanotubes (25.9 mAh·g-1). The cyclic voltammetry measurement indicated that the ordered mesoporous carbon electrode possessed higher electrochemical activity than single-walled carbon nanotubes electrode.
2007, 23(09): 1405-1410
doi: 10.3866/PKU.WHXB20070918
Abstract:
The concentration distribution of polymer solution prior to gelling has been numerically studied with self-consistent field theory (SCFT). As a result, under specified conditions (system size, interactions between polymer segments, solvent and wall, solution concentration), the depletion/adsorption transition will take place. It was demonstrated that the depletion/adsorption transition depends on the difference of the interaction parameters between polymer segment and wall, and that of solvent and wall. The reciprocal of the polymer chain length was found to have a linear effect on the differences of the interaction parameters at the transition point. Furthermore, when the capillary’s diameter is not large enough, the linear fitting constants are related with the system dimension and the average volume fraction of the polymer solution. The polymer chains with smaller molecular weight approach closer to the wall when the polymer is polydisperse. Increasing the polymer concentration and chain length, choosing better solvents or reducing the systemdimension is beneficial to the solution uniformity.
The concentration distribution of polymer solution prior to gelling has been numerically studied with self-consistent field theory (SCFT). As a result, under specified conditions (system size, interactions between polymer segments, solvent and wall, solution concentration), the depletion/adsorption transition will take place. It was demonstrated that the depletion/adsorption transition depends on the difference of the interaction parameters between polymer segment and wall, and that of solvent and wall. The reciprocal of the polymer chain length was found to have a linear effect on the differences of the interaction parameters at the transition point. Furthermore, when the capillary’s diameter is not large enough, the linear fitting constants are related with the system dimension and the average volume fraction of the polymer solution. The polymer chains with smaller molecular weight approach closer to the wall when the polymer is polydisperse. Increasing the polymer concentration and chain length, choosing better solvents or reducing the systemdimension is beneficial to the solution uniformity.
2007, 23(09): 1411-1414
doi: 10.3866/PKU.WHXB20070919
Abstract:
The predominance diagram of dissolved species and potential -pH diagrams of V-H2O system were studied at 25 ℃ by concentration comparison method. The concentration of dissolved species, the borderlines for liquid phases or solid phases, and the borderlines between solid and liquid phase were calculated using the computer programming on the basis of thermodynamic analysis and electrochemistry analysis. The solid regions and liquid regions of kinds of species were ascertained. The predominance diagram of dissolved species and two potential-pH diagrams (at total concentration of V: cT(V)=1.0×10-5 and cT(V)=1.0×10-7 mol·L-1, respectively) of the V-H2O system were plotted. The results showed that under a certain temperature and pressure, the phase stable regions were determined by the total concentration of the species. The stable region of solution was enlarged along with the decreasing of cT(V), whereas the regions of solid phases were reduced.
The predominance diagram of dissolved species and potential -pH diagrams of V-H2O system were studied at 25 ℃ by concentration comparison method. The concentration of dissolved species, the borderlines for liquid phases or solid phases, and the borderlines between solid and liquid phase were calculated using the computer programming on the basis of thermodynamic analysis and electrochemistry analysis. The solid regions and liquid regions of kinds of species were ascertained. The predominance diagram of dissolved species and two potential-pH diagrams (at total concentration of V: cT(V)=1.0×10-5 and cT(V)=1.0×10-7 mol·L-1, respectively) of the V-H2O system were plotted. The results showed that under a certain temperature and pressure, the phase stable regions were determined by the total concentration of the species. The stable region of solution was enlarged along with the decreasing of cT(V), whereas the regions of solid phases were reduced.
2007, 23(09): 1415-1420
doi: 10.3866/PKU.WHXB20070920
Abstract:
The membrane characteristics of capsules composed of sodiumcellulose sulfate (NaCS) and poly[dimethyl(diallyl)ammonium chloride] (PDMDAAC) were investigated under the condition of introducing other molecules. The small molecules, soluble polymers, soluble polyions, and salts of small molecule were individually added into polyanion (NaCS) solution to check their effects on capsule formation. The membrane thickness and mechanical intensity of capsules were studied under the condition of different concentration of additives. Meanwhile the effects of additives on viscosity and zeta potential of dilute NaCS solution were investigated. The results indicated that the effects of additives on the membrane characteristics could be judged by viscosity and zeta potential variation of dilute polyelectrolytes with addition of other molecules. The effect of additives on the reaction between polyelectrolytes was analyzed, and an explanation correlating the characteristics of capsule to the properties of dilute solution was proposed according to solution lattice theory.
The membrane characteristics of capsules composed of sodiumcellulose sulfate (NaCS) and poly[dimethyl(diallyl)ammonium chloride] (PDMDAAC) were investigated under the condition of introducing other molecules. The small molecules, soluble polymers, soluble polyions, and salts of small molecule were individually added into polyanion (NaCS) solution to check their effects on capsule formation. The membrane thickness and mechanical intensity of capsules were studied under the condition of different concentration of additives. Meanwhile the effects of additives on viscosity and zeta potential of dilute NaCS solution were investigated. The results indicated that the effects of additives on the membrane characteristics could be judged by viscosity and zeta potential variation of dilute polyelectrolytes with addition of other molecules. The effect of additives on the reaction between polyelectrolytes was analyzed, and an explanation correlating the characteristics of capsule to the properties of dilute solution was proposed according to solution lattice theory.
2007, 23(09): 1421-1424
doi: 10.3866/PKU.WHXB20070921
Abstract:
The hybridization of oli nucleotide probe with matched or mismatched DNA target was monitored by a combination of electrochemical control and in situ quartz crystal microbalance technique. The results indicated that the apparent efficiency of hybridization for matched DNA target at a positive potential was higher than that at a negative potential. But an obvious response of “false positives”may be obtained at the positive potential. Application of negative potential can availably halt hybridization for mismatched target DNA. The effect of the orientation of oli nucleotide probe and micro forces on DNA hybridization under interface electric field was discussed.
The hybridization of oli nucleotide probe with matched or mismatched DNA target was monitored by a combination of electrochemical control and in situ quartz crystal microbalance technique. The results indicated that the apparent efficiency of hybridization for matched DNA target at a positive potential was higher than that at a negative potential. But an obvious response of “false positives”may be obtained at the positive potential. Application of negative potential can availably halt hybridization for mismatched target DNA. The effect of the orientation of oli nucleotide probe and micro forces on DNA hybridization under interface electric field was discussed.
2007, 23(09): 1425-1431
doi: 10.3866/PKU.WHXB20070922
Abstract:
A time and space averaged chemical kinetics model in the removal of formaldehyde via a dielectric barrier discharge at atmospheric pressure and ambient temperature was reported. An analysis with regard to the discharge time evolution of the different main species was also included, and the results of the analysis showed that O· and OH·radicals, especially OH·radicals, were the key species for the removal of HCHO. The role played by the first electronically excited metastable state N2(A3∑+u) was clarified that, in air, the chemical attacks of O2 and H2Oby N2(A3∑+u) produced much more O·and OH·radicals. In nitrogen, N2(A3∑removal of HCHO. Specific energy cost and the molar ratio of nCO2 /nCO for HCHOremoval at different HCHOinitial concentrations and gas flow rates were also discussed. Specific energy cost at high HCHO initial concentration was lower than that at low HCHOinitial concentration. If input discharge energy density <60 J·L-1, nCO2 /nCO at lowHCHOinitial concentration was higher than that at high HCHO initial concentration.
A time and space averaged chemical kinetics model in the removal of formaldehyde via a dielectric barrier discharge at atmospheric pressure and ambient temperature was reported. An analysis with regard to the discharge time evolution of the different main species was also included, and the results of the analysis showed that O· and OH·radicals, especially OH·radicals, were the key species for the removal of HCHO. The role played by the first electronically excited metastable state N2(A3∑+u) was clarified that, in air, the chemical attacks of O2 and H2Oby N2(A3∑+u) produced much more O·and OH·radicals. In nitrogen, N2(A3∑removal of HCHO. Specific energy cost and the molar ratio of nCO2 /nCO for HCHOremoval at different HCHOinitial concentrations and gas flow rates were also discussed. Specific energy cost at high HCHO initial concentration was lower than that at low HCHOinitial concentration. If input discharge energy density <60 J·L-1, nCO2 /nCO at lowHCHOinitial concentration was higher than that at high HCHO initial concentration.
2007, 23(09): 1432-1436
doi: 10.3866/PKU.WHXB20070923
Abstract:
Electrochemical voltametric methods and in-situ electrochemical surface-enhanced Raman spectroscopy (SERS) were used to investigate the electrooxidation behavior of ethanol in different media on a roughened platinum electrode. It was found that ethanol could dissociate spontaneously to produce strongly adsorbed intermediate, CO, in acidic, neutral, and alkaline media on the roughened platinum electrode. The complete oxidation potential of COad on the roughened platinumelectrode was negatively shifted about 0.300V in the alkaline medium (0.20 V) compared with that in the acidic and neutral media (0.50 V). The positive oxidation peak potential of ethanol was negatively shifted about 0.85 V in the alkaline medium (-0.20 V) than that in the acidic medium (0.65 V). By comparing the oxidation current and the peak potential, it was found that the electrocatalytic activity of roughened platinum electrode for ethanol and CO oxidation in the alkaline medium was higher than in acidic and neutral media. The results suggested that ethanol was oxidized to CO2 on the roughened platinum electrode via parallel reaction mechanism in acidic, neutral or alkaline media.
Electrochemical voltametric methods and in-situ electrochemical surface-enhanced Raman spectroscopy (SERS) were used to investigate the electrooxidation behavior of ethanol in different media on a roughened platinum electrode. It was found that ethanol could dissociate spontaneously to produce strongly adsorbed intermediate, CO, in acidic, neutral, and alkaline media on the roughened platinum electrode. The complete oxidation potential of COad on the roughened platinumelectrode was negatively shifted about 0.300V in the alkaline medium (0.20 V) compared with that in the acidic and neutral media (0.50 V). The positive oxidation peak potential of ethanol was negatively shifted about 0.85 V in the alkaline medium (-0.20 V) than that in the acidic medium (0.65 V). By comparing the oxidation current and the peak potential, it was found that the electrocatalytic activity of roughened platinum electrode for ethanol and CO oxidation in the alkaline medium was higher than in acidic and neutral media. The results suggested that ethanol was oxidized to CO2 on the roughened platinum electrode via parallel reaction mechanism in acidic, neutral or alkaline media.
2007, 23(09): 1437-1441
doi: 10.3866/PKU.WHXB20070924
Abstract:
Low-temperature heat capacities of the complex Zn(Phe)(NO3)2·H2O(s) (Phe: phenylalanine) have been precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 78 to 370 K. The initial dehydration temperature of the complex (T0=(324.27±0.37) K) has been obtained by means of the analysis of the heat capacity curve. The experimental values of molar heat capacities have been fitted to a polynomial equation of heat capacities (Cp, m) vs the temperature (T) with the least square method. The smoothed heat capacities and the thermodynamic functions of the complex have been calculated on the basis of the equation. In accordance with Hess law, dissolution enthalpies of the mixtures {ZnSO4·7H2O(s)+2NaNO3(s)+L-Phe(s)} and {Zn(Phe)(NO3)2·H2O(s)+Na2SO4(s)} in 2 mol·L-1 HCl were measured to be: ⊿dH0m,1=(69.42±0.05) kJ·mol-1 and ⊿dH0m,2 =(48.14±0.04) kJ·mol-1, by using an isoperibol solution-reaction calorimeter. Furthermore, the standard molar enthalpy of formation for the complex was determined as, ⊿fH0m =-(1363.10±3.52) kJ·mol-1, by designing a thermochemical cycle. In addition, the reliability of the designed thermochemical cycle has been verified by UV-Vis spectroscopy and the data of the refractive indices.
Low-temperature heat capacities of the complex Zn(Phe)(NO3)2·H2O(s) (Phe: phenylalanine) have been precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 78 to 370 K. The initial dehydration temperature of the complex (T0=(324.27±0.37) K) has been obtained by means of the analysis of the heat capacity curve. The experimental values of molar heat capacities have been fitted to a polynomial equation of heat capacities (Cp, m) vs the temperature (T) with the least square method. The smoothed heat capacities and the thermodynamic functions of the complex have been calculated on the basis of the equation. In accordance with Hess law, dissolution enthalpies of the mixtures {ZnSO4·7H2O(s)+2NaNO3(s)+L-Phe(s)} and {Zn(Phe)(NO3)2·H2O(s)+Na2SO4(s)} in 2 mol·L-1 HCl were measured to be: ⊿dH0m,1=(69.42±0.05) kJ·mol-1 and ⊿dH0m,2 =(48.14±0.04) kJ·mol-1, by using an isoperibol solution-reaction calorimeter. Furthermore, the standard molar enthalpy of formation for the complex was determined as, ⊿fH0m =-(1363.10±3.52) kJ·mol-1, by designing a thermochemical cycle. In addition, the reliability of the designed thermochemical cycle has been verified by UV-Vis spectroscopy and the data of the refractive indices.
2007, 23(09): 1442-1446
doi: 10.3866/PKU.WHXB20070925
Abstract:
Al12Si3.75Ge0.25O26 mullite powder was prepared by sol-gel method using Al(NO3)3, Cl3GeCH2CH2COOH and TEOS(Si(OC2H5)4) as precursors. The mullitization process of precursors was monitored by TG-DSC, XRD and FT-IR. After the reduction of Al12Si3.75Ge0.25O26, strong room temperature photoluminescence (PL) can be observed at 565, 613, 682, 731, and 777 nm, respectively. The PL intensity was related with the reduction temperature, and the sample reduced at 500 ℃ had the highest PL intensity among those samples reduced at different temperatures. The XPS spectra showed that some Ge4+ had been reduced to Ge0 under those temperatures. The average size of Ge nanoparticles was about 1.95 nmestimated by Raman spectra analysis.
Al12Si3.75Ge0.25O26 mullite powder was prepared by sol-gel method using Al(NO3)3, Cl3GeCH2CH2COOH and TEOS(Si(OC2H5)4) as precursors. The mullitization process of precursors was monitored by TG-DSC, XRD and FT-IR. After the reduction of Al12Si3.75Ge0.25O26, strong room temperature photoluminescence (PL) can be observed at 565, 613, 682, 731, and 777 nm, respectively. The PL intensity was related with the reduction temperature, and the sample reduced at 500 ℃ had the highest PL intensity among those samples reduced at different temperatures. The XPS spectra showed that some Ge4+ had been reduced to Ge0 under those temperatures. The average size of Ge nanoparticles was about 1.95 nmestimated by Raman spectra analysis.
2007, 23(09): 1447-1450
doi: 10.3866/PKU.WHXB20070926
Abstract:
The temperature-programmeddesorption(TPD)was used tostudythe adsorptionandthermal decomposition of 2-propanol and trifluoro-2-propanol on clean Ni(100) surface. The products of TPD in both cases were traced for molecular desorption and for the products of dehydration (alkene) and dehydrogenation (ketone) reactions. The results showed that a partial switch from alcohol dehydrogenation to alcohol dehydration was driven by substitution of γ-hydrogen with more electronegative fluorine atoms. The inductive effect exerted by fluorine atoms substituted at the γ position led to a significant inhibition of β-hydride elimination from the alkoxide intermediates, and to the opening of a new γ-hydride elimination channel which eventually ended in alkene formation. While exclusive dehydrogenation to acetone via β-hydride elimination from 2-propoxide surface species was seen with 2-propanol, some dehydration to 3,3,3-trifluoropropene was observed with 1,1,1-trifluoro-2-propanol.
The temperature-programmeddesorption(TPD)was used tostudythe adsorptionandthermal decomposition of 2-propanol and trifluoro-2-propanol on clean Ni(100) surface. The products of TPD in both cases were traced for molecular desorption and for the products of dehydration (alkene) and dehydrogenation (ketone) reactions. The results showed that a partial switch from alcohol dehydrogenation to alcohol dehydration was driven by substitution of γ-hydrogen with more electronegative fluorine atoms. The inductive effect exerted by fluorine atoms substituted at the γ position led to a significant inhibition of β-hydride elimination from the alkoxide intermediates, and to the opening of a new γ-hydride elimination channel which eventually ended in alkene formation. While exclusive dehydrogenation to acetone via β-hydride elimination from 2-propoxide surface species was seen with 2-propanol, some dehydration to 3,3,3-trifluoropropene was observed with 1,1,1-trifluoro-2-propanol.
2007, 23(09): 1451-1453
doi: 10.3866/PKU.WHXB20070927
Abstract:
Ferrocene-filled double-walled carbon nanotubes (Fc@DWNTs) were successfully synthesized by introducing ferrocene molecules into the hollow cavities of DWNTs in a vapor phase diffusion process. High resolution transmission electron microscopy (HRTEM) and infrared spectroscopy (FTIR) were employed to characterize this nanohybrid material. FTIR results revealed that there were strong intermolecular interactions between DWNTs and ferrocene, indicating electron transfers occured between them.
Ferrocene-filled double-walled carbon nanotubes (Fc@DWNTs) were successfully synthesized by introducing ferrocene molecules into the hollow cavities of DWNTs in a vapor phase diffusion process. High resolution transmission electron microscopy (HRTEM) and infrared spectroscopy (FTIR) were employed to characterize this nanohybrid material. FTIR results revealed that there were strong intermolecular interactions between DWNTs and ferrocene, indicating electron transfers occured between them.
2007, 23(09): 1454-1458
doi: 10.3866/PKU.WHXB20070928
Abstract:
The absorption and emission spectra of magnolol in ethanol were determined, and the fluorescence self-quenching characteristics, including static-quenching and dynamic-quenching, were revealed. Magnolol aggregation occurs with its concentration increases. On the other hand, the quenching rate constants produced by the monomer, dimmer, and trimer, kqm, kqd, and kqt, are much greater than those controlled by diffusion. It seems that other long-range energy migration should be taken into account besides the short-range electron exchange energy in the quenching mechanism.
2007, 23(09): 1459-1462
doi: 10.3866/PKU.WHXB20070929
Abstract:
The thermal stability and the kinetics of thermal decomposition of protionamide were studied by thermogravimetry. Activation energy Ea of thermal decomposition of this substance was obtained to be 54.65 kJ·mol-1 by Kissinger method and Ozawa-Flynn-Wall method. Kinetics model function and frequency factor A of protionamide were predicted with the Malek method, which were f(α)=α0.391(1-α)0.145 and lnA=13.12, respectively. Moreover, melting point, molar enthalpy and entropy of fusion of this compound were determined to be 414.09 K, 23.21 kJ·mol-1, and
56.06 J·mol-1·K-1, respectively.
The thermal stability and the kinetics of thermal decomposition of protionamide were studied by thermogravimetry. Activation energy Ea of thermal decomposition of this substance was obtained to be 54.65 kJ·mol-1 by Kissinger method and Ozawa-Flynn-Wall method. Kinetics model function and frequency factor A of protionamide were predicted with the Malek method, which were f(α)=α0.391(1-α)0.145 and lnA=13.12, respectively. Moreover, melting point, molar enthalpy and entropy of fusion of this compound were determined to be 414.09 K, 23.21 kJ·mol-1, and
56.06 J·mol-1·K-1, respectively.
2007, 23(09): 1463-1467
doi: 10.3866/PKU.WHXB20070930
Abstract:
The spontaneous monolayer dispersion of sucrose on the surface of MCM-48 by impregnation method was studied, and its monolayer dispersion capacity was determined by XRD quantitative phase analysis. The sucrose/MCM-48 samples were characterized by DTA and N2 adsorption. It was found that sucrose could readily monolayerly dispersed on MCM-48, with a monolayer dispersion capacity of 1.1 g sucrose/g MCM-48. When 0.8 g sucrose per g MCM-48 was dispersed on MCM-48, the specific surface area of MCM-48 was decreased from 998 m2·g-1 to 114 m2·g-1, with the decrease of the mean pore size from 2.7 nm to 2.0 nm. Further increase of sucrose amount more than the monolayer dispersion capacity resulted in the decrease of the specific surface area to less than 10 m2·g-1. This might be related to the limited difference between the pore size of MCM-48 and the molecular diameter of sucrose, which led to the blockage of the pores of MCM-48 at high sucrose amount.
The spontaneous monolayer dispersion of sucrose on the surface of MCM-48 by impregnation method was studied, and its monolayer dispersion capacity was determined by XRD quantitative phase analysis. The sucrose/MCM-48 samples were characterized by DTA and N2 adsorption. It was found that sucrose could readily monolayerly dispersed on MCM-48, with a monolayer dispersion capacity of 1.1 g sucrose/g MCM-48. When 0.8 g sucrose per g MCM-48 was dispersed on MCM-48, the specific surface area of MCM-48 was decreased from 998 m2·g-1 to 114 m2·g-1, with the decrease of the mean pore size from 2.7 nm to 2.0 nm. Further increase of sucrose amount more than the monolayer dispersion capacity resulted in the decrease of the specific surface area to less than 10 m2·g-1. This might be related to the limited difference between the pore size of MCM-48 and the molecular diameter of sucrose, which led to the blockage of the pores of MCM-48 at high sucrose amount.
2007, 23(09): 1468-1472
doi: 10.3866/PKU.WHXB20070931
Abstract:
The dipole moment(μ), polarizability(α) and the first hyperpolarizability(β) of van der Waals complexes anion [Li…X]e-[1](X=FH, OH2, NH3) were calculated by using ab initio methods with 6-311G basis set series at MP2 level. We also discussed the contribution of the effect of basis set and the electronic correlation on the dipole moment, polarizability and the first hyperpolarizability, and compared the contributions of valence electrons to the first hyperpolarizability. The values of dipole moment, polarizability and the first hyperpolarizability of three complexes anion calculated with MP4(SDQ)/6-311++G(2df, 2pd) are: μ=2.5633 a.u., α=1.0476×103 a.u., β=1.0948×105 a.u. for [Li…FH]e-[1], μ=2.3204 a.u., α=1.2201×103 a.u., β=2.1410×105 a.u. for [Li…OH2]e-[1] and μ=2.4687 a.u., α=1.4817×103 a.u., β= 3.4040×105 a.u. for [Li…NH3]e-[1], respectively. The results showed that all the three complexes anion had huge first hyperpolarizability, andthe contributionof one valence electron tothe first hyperpolarizabilitywasmore than1.0×105 a.u..
The dipole moment(μ), polarizability(α) and the first hyperpolarizability(β) of van der Waals complexes anion [Li…X]e-[1](X=FH, OH2, NH3) were calculated by using ab initio methods with 6-311G basis set series at MP2 level. We also discussed the contribution of the effect of basis set and the electronic correlation on the dipole moment, polarizability and the first hyperpolarizability, and compared the contributions of valence electrons to the first hyperpolarizability. The values of dipole moment, polarizability and the first hyperpolarizability of three complexes anion calculated with MP4(SDQ)/6-311++G(2df, 2pd) are: μ=2.5633 a.u., α=1.0476×103 a.u., β=1.0948×105 a.u. for [Li…FH]e-[1], μ=2.3204 a.u., α=1.2201×103 a.u., β=2.1410×105 a.u. for [Li…OH2]e-[1] and μ=2.4687 a.u., α=1.4817×103 a.u., β= 3.4040×105 a.u. for [Li…NH3]e-[1], respectively. The results showed that all the three complexes anion had huge first hyperpolarizability, andthe contributionof one valence electron tothe first hyperpolarizabilitywasmore than1.0×105 a.u..
2007, 23(09): 1473-1477
doi: 10.3866/PKU.WHXB20070932
Abstract:
A preparation method of ambient temperature ionic liquid, 3-hexyl-1-methylimidazolium iodide, via efficient reaction of 1-methylimidazole with 1-hexyl iodide using Teflon-lined, stainless steel autoclave, was described. It was found that excellent yield, about 100%, was obtained due to the increase of reaction temperature, which resulted in the feasibility of using only stoichiometric amounts of reactants. The main advantages of this present approach are solvent-free, eco-friendly, easy procedure and high purity of products. Moreover, the apparent diffusion coefficient of triiodide in the mixture of 3-hexyl-1-methylimidazolium iodide and 1-methylimidazole was investigated by cyclic voltammetry. The photovoltaic performances of dye-sensitized solar cells with electrolytes containing the mixture and different concentrations of iodine were compared.
A preparation method of ambient temperature ionic liquid, 3-hexyl-1-methylimidazolium iodide, via efficient reaction of 1-methylimidazole with 1-hexyl iodide using Teflon-lined, stainless steel autoclave, was described. It was found that excellent yield, about 100%, was obtained due to the increase of reaction temperature, which resulted in the feasibility of using only stoichiometric amounts of reactants. The main advantages of this present approach are solvent-free, eco-friendly, easy procedure and high purity of products. Moreover, the apparent diffusion coefficient of triiodide in the mixture of 3-hexyl-1-methylimidazolium iodide and 1-methylimidazole was investigated by cyclic voltammetry. The photovoltaic performances of dye-sensitized solar cells with electrolytes containing the mixture and different concentrations of iodine were compared.
2007, 23(09): 1478-1482
doi: 10.3866/PKU.WHXB20070933
Abstract:
The Raman spectra and Surface enhanced Raman spectra (SERS) of leucine and isoleucine adsorbed on core-shell Au/Ag nanoparticles were obtained and assigned, and the different Raman peaks resulting from different vibrational models of the isomers忆groups were analysed. In Raman spectra, the leucine’s (ω(CH3)) is at 962, 945, 924 cm-1, (δas(CH3)) at 1408, 1454 cm-1; corresponding values for isoleucine are, 922 cm-1 and 1448, 1420, 1394 cm-1, respectwely. The difference in the peak positions of corresponding groups between leucine and isoleucine is more apparent in the SERS at acidic and basic conditions. The relationship between leucine and isoleucine’s concentration and SERS was interpreted preliminarily and the adsorption model on the core-shell Au/Ag nanoparticle surface was speculated.
The Raman spectra and Surface enhanced Raman spectra (SERS) of leucine and isoleucine adsorbed on core-shell Au/Ag nanoparticles were obtained and assigned, and the different Raman peaks resulting from different vibrational models of the isomers忆groups were analysed. In Raman spectra, the leucine’s (ω(CH3)) is at 962, 945, 924 cm-1, (δas(CH3)) at 1408, 1454 cm-1; corresponding values for isoleucine are, 922 cm-1 and 1448, 1420, 1394 cm-1, respectwely. The difference in the peak positions of corresponding groups between leucine and isoleucine is more apparent in the SERS at acidic and basic conditions. The relationship between leucine and isoleucine’s concentration and SERS was interpreted preliminarily and the adsorption model on the core-shell Au/Ag nanoparticle surface was speculated.
2007, 23(09): 1483-1486
doi: 10.3866/PKU.WHXB20070934
Abstract:
The catalytic activity of candida ru sa lipase has been investigated in sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/Triton X-100 mixed reverse micellar systemby using castor oil as substrate. The effects of molar fraction of Triton X-100 in total surfactants, molar ratio of water to total surfactants, reaction temperature, pH and the concentration of castor oil on enzyme activity were studied when the concentration of overall surfactant was kept constant. Significant increase of the activity of candida ru sa lipase was observed in the presence of Triton X-100. It was also found that the castor oil inhibited the reaction when its concentration was higher than 0.24 mol·L-1.
The catalytic activity of candida ru sa lipase has been investigated in sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/Triton X-100 mixed reverse micellar systemby using castor oil as substrate. The effects of molar fraction of Triton X-100 in total surfactants, molar ratio of water to total surfactants, reaction temperature, pH and the concentration of castor oil on enzyme activity were studied when the concentration of overall surfactant was kept constant. Significant increase of the activity of candida ru sa lipase was observed in the presence of Triton X-100. It was also found that the castor oil inhibited the reaction when its concentration was higher than 0.24 mol·L-1.
