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1993 Volume 9 Issue 2
1993, 9(02): 145-147
doi: 10.3866/PKU.WHXB19930201
Abstract:
This paper reports the establishment of the set-up of ion-neutral reaction and the measurement of the rate constant of the reaction O~+ ions with N_2 at 298 K. O~+ ions were generated by microwave and electrode in this discharge flow system, and the O~+ concentriation was detected by quadrapole mass spectrometer.
The specific rate constant obtained is
k=(2.50±0.52)×10~(-12) cm~3·molec~(-1)·s~(-1) (T=298 K)
This paper reports the establishment of the set-up of ion-neutral reaction and the measurement of the rate constant of the reaction O~+ ions with N_2 at 298 K. O~+ ions were generated by microwave and electrode in this discharge flow system, and the O~+ concentriation was detected by quadrapole mass spectrometer.
The specific rate constant obtained is
k=(2.50±0.52)×10~(-12) cm~3·molec~(-1)·s~(-1) (T=298 K)
1993, 9(02): 148-154
doi: 10.3866/PKU.WHXB19930202
Abstract:
Two series of luminescent rare-earth chelates have been studied spectroscopically, one is(TOPO)_2Eu(β-dik)_3(TOPO=tri-n-octyl-phosphine oxide; β-dik=trifluoroace-tylacetone(TFA), hexafluoroacetylacetone(HFA), thenoyltrifluoroacetone(TTA)), the other is (Phen)_2RE(NO_3)_3 (Phen=1,10-phenanthroline; RE=Eu,Tb,Sm). By using British NIMA LB system 2000 round trough, the pressure area (π-A) isotherms for (TOPO)_2Eu(β-dik)_3, (Phen)_2RE(NO_3)_3 monolayers at the air-water interface were investigated, then the monolayers were transfered on hydrophobic glass slides. The alternate-layer LB films were deposited by arachidic acid (AA, odd layers) and (TOPO)_2Eu (β-dik)_3 (even layers). The mixed LB films were deposited by (Phen)_2Eu(NO_3)_3 and AA (in molar ratio 1:4). Low angle X-ray diffraction results showed that the LB films mentioned above all have a periodic structure. The lattice spacing, for alternate-layer LB films are 5.32—5.52 nm, for mixed LB films are 5.23—5.32 nm. FTIR results indicated that hydrogen bond established between —CF_3 of (TOPO)_2Eu(β-dik)_3 and —COOH of AA in alternate-layer LB films. It was found that the fluorescent emission from the LB films mentioned above is strong and the fluorescent emission strength increases with the increasing of the number of layers. that the fluorescent emission from the LB films mentioned above is strong and the fluorescent emission strength increases with the increasing of the number of layers. Especially, even with only two alternate layers of AA and (TOPO)_2Eu(β-dik)_3, the characteristic fluorescent emission of Eu(III)(~5D_0→F_1 and ~5D_0→~7F_2) could be detected also. The fluorescent emission spectra of these rare-earth chelates in multilayers are much similar to those in solution, but the fluorescent excitation spectra are a little different. The characteristic fluorescent emission for each rare-earth chelate appeared in the spectra provided that the mixed LB film of (Phen)_2Eu(NO_3)_3, (Phen)_2Tb(NO_3)_3, (Phen)_2Sm(NO_3)_2 and arachidic acid (in molar ratio 1:1:1:12) was excited by optimum excitation wavelength corresponding to each rare-earth.
Two series of luminescent rare-earth chelates have been studied spectroscopically, one is(TOPO)_2Eu(β-dik)_3(TOPO=tri-n-octyl-phosphine oxide; β-dik=trifluoroace-tylacetone(TFA), hexafluoroacetylacetone(HFA), thenoyltrifluoroacetone(TTA)), the other is (Phen)_2RE(NO_3)_3 (Phen=1,10-phenanthroline; RE=Eu,Tb,Sm). By using British NIMA LB system 2000 round trough, the pressure area (π-A) isotherms for (TOPO)_2Eu(β-dik)_3, (Phen)_2RE(NO_3)_3 monolayers at the air-water interface were investigated, then the monolayers were transfered on hydrophobic glass slides. The alternate-layer LB films were deposited by arachidic acid (AA, odd layers) and (TOPO)_2Eu (β-dik)_3 (even layers). The mixed LB films were deposited by (Phen)_2Eu(NO_3)_3 and AA (in molar ratio 1:4). Low angle X-ray diffraction results showed that the LB films mentioned above all have a periodic structure. The lattice spacing, for alternate-layer LB films are 5.32—5.52 nm, for mixed LB films are 5.23—5.32 nm. FTIR results indicated that hydrogen bond established between —CF_3 of (TOPO)_2Eu(β-dik)_3 and —COOH of AA in alternate-layer LB films. It was found that the fluorescent emission from the LB films mentioned above is strong and the fluorescent emission strength increases with the increasing of the number of layers. that the fluorescent emission from the LB films mentioned above is strong and the fluorescent emission strength increases with the increasing of the number of layers. Especially, even with only two alternate layers of AA and (TOPO)_2Eu(β-dik)_3, the characteristic fluorescent emission of Eu(III)(~5D_0→F_1 and ~5D_0→~7F_2) could be detected also. The fluorescent emission spectra of these rare-earth chelates in multilayers are much similar to those in solution, but the fluorescent excitation spectra are a little different. The characteristic fluorescent emission for each rare-earth chelate appeared in the spectra provided that the mixed LB film of (Phen)_2Eu(NO_3)_3, (Phen)_2Tb(NO_3)_3, (Phen)_2Sm(NO_3)_2 and arachidic acid (in molar ratio 1:1:1:12) was excited by optimum excitation wavelength corresponding to each rare-earth.
1993, 9(02): 155-160
doi: 10.3866/PKU.WHXB19930203
Abstract:
Tbe reaction path (IRC or MEP) of the reaction CH(~4∑~-)+H_2→CH_2(~3B_1)+H has been traced by Fukui's theory and ab initio calculation. Furthermore, the dynamic properties along the reaction path and CVT rate constants have been investi-gated by reaction path Hamiltonian theory and variational transition state theory. On this basis, the adiabatic and diabatic vibrational-state-selected rate constants were calculated. The results show that the effects of CVT method are notable, and the rate enhancement is also notable while H_2 stretch mode is vibrationally excited.
Tbe reaction path (IRC or MEP) of the reaction CH(~4∑~-)+H_2→CH_2(~3B_1)+H has been traced by Fukui's theory and ab initio calculation. Furthermore, the dynamic properties along the reaction path and CVT rate constants have been investi-gated by reaction path Hamiltonian theory and variational transition state theory. On this basis, the adiabatic and diabatic vibrational-state-selected rate constants were calculated. The results show that the effects of CVT method are notable, and the rate enhancement is also notable while H_2 stretch mode is vibrationally excited.
1993, 9(02): 161-164
doi: 10.3866/PKU.WHXB19930204
Abstract:
The electronic states of a C_(60) molecule have been calculated by using the SSH model. The electronic energy spectrum and dimerization on molecular structure are in od agreement with that obtained from the method of molecular orbit and local density function theory. With the SSH model, there is string polaron for both neutral excited and charged C_(60) molecule, and this is consistent with the experimental results. Besides, a comparison has been made between C_(60) and polacetylene.
The electronic states of a C_(60) molecule have been calculated by using the SSH model. The electronic energy spectrum and dimerization on molecular structure are in od agreement with that obtained from the method of molecular orbit and local density function theory. With the SSH model, there is string polaron for both neutral excited and charged C_(60) molecule, and this is consistent with the experimental results. Besides, a comparison has been made between C_(60) and polacetylene.
1993, 9(02): 165-169
doi: 10.3866/PKU.WHXB19930205
Abstract:
1993, 9(02): 170-174
doi: 10.3866/PKU.WHXB19930206
Abstract:
The O_(1s) binding energy of M , CaO, SrO and BaO were determined by means of XPS. Prior to the determination,the samples were heated in the spectrometer at 400 ℃. The surface carbonates were partly decomposed and the O_(1s) spectra of lattice oxygen of the oxides were recorded. The O_(1s) binding energies of M , CaO and SrO determined by present work are lower than that reported in the literatures. A reasonable correlation between O_(1s) binding energies determined by present work and the partial charge on oxygen calculated by Sanderson for these alkaline earth oxides are found. The O_(1s) binding energy of BaO_2 determined by present work is 530.9 eV which is also lower than that reported in the literatures.
The O_(1s) binding energy of M , CaO, SrO and BaO were determined by means of XPS. Prior to the determination,the samples were heated in the spectrometer at 400 ℃. The surface carbonates were partly decomposed and the O_(1s) spectra of lattice oxygen of the oxides were recorded. The O_(1s) binding energies of M , CaO and SrO determined by present work are lower than that reported in the literatures. A reasonable correlation between O_(1s) binding energies determined by present work and the partial charge on oxygen calculated by Sanderson for these alkaline earth oxides are found. The O_(1s) binding energy of BaO_2 determined by present work is 530.9 eV which is also lower than that reported in the literatures.
1993, 9(02): 175-180
doi: 10.3866/PKU.WHXB19930207
Abstract:
The electrochemical properties of morin(MOR)over the entire pH range were studied. Four reduction waves were obtained. P_1 is a surface catalytic hydrogen wave. The other three waves have been proved as adsorptive waves. The electrode processes have been verified as being an EC mechanism. The reduction electron number of P_2 was determined as one by using DC polarography. At pH 6.6, on the surface of mercury electrode, the adsorption of MOR obeys Temkin isotherm. The adsorption coef-ficient β=9.3×10~6 and the experimental constant g=2.2×10~(-10) mol·cm~(-2) has been calculated. The adsorption type is considered as a flat orientation on the surface of the mercury electrode.
In 0.2 mol·L~(-1) sodium hydroxide solution, P_3 and P_4 can be obtained. n_3=1, n_4=1 have been determined by using DC adsorptive current formula and peak area measurement. The potential of P_3 and P_4 shift positively with the increase of pH. It has been suggested that hydroxide ion participates in the electrode reaction.
The electrochemical properties of morin(MOR)over the entire pH range were studied. Four reduction waves were obtained. P_1 is a surface catalytic hydrogen wave. The other three waves have been proved as adsorptive waves. The electrode processes have been verified as being an EC mechanism. The reduction electron number of P_2 was determined as one by using DC polarography. At pH 6.6, on the surface of mercury electrode, the adsorption of MOR obeys Temkin isotherm. The adsorption coef-ficient β=9.3×10~6 and the experimental constant g=2.2×10~(-10) mol·cm~(-2) has been calculated. The adsorption type is considered as a flat orientation on the surface of the mercury electrode.
In 0.2 mol·L~(-1) sodium hydroxide solution, P_3 and P_4 can be obtained. n_3=1, n_4=1 have been determined by using DC adsorptive current formula and peak area measurement. The potential of P_3 and P_4 shift positively with the increase of pH. It has been suggested that hydroxide ion participates in the electrode reaction.
1993, 9(02): 181-186
doi: 10.3866/PKU.WHXB19930208
Abstract:
SPE (Solid Polymer Electrolyte) composite electrodes were utilized for the selective oxidation of allyl alcohol to aldehyde. In order to enhance the reaction selectivity, manganese dioxide was deposited into the Nafion as a mediator. Cinnamyl alcohol was selectively oxidized to cinnamaldehyde with high current efficiency.
SPE (Solid Polymer Electrolyte) composite electrodes were utilized for the selective oxidation of allyl alcohol to aldehyde. In order to enhance the reaction selectivity, manganese dioxide was deposited into the Nafion as a mediator. Cinnamyl alcohol was selectively oxidized to cinnamaldehyde with high current efficiency.
1993, 9(02): 187-192
doi: 10.3866/PKU.WHXB19930209
Abstract:
It has been shown by in situ XRD that V_2O_5 can disperse spontaneously onto the surface of silica gel, but the dispersion temperature is relatively high. The presence of H_2O vapour inhibits the dispersion of V_2O_5 to a certain extent, The dispersion process of V_2O_5 onto the surface of silica gel can be accelerated by using K_2SO_4 as an additive. The surface acidity of V_2O_5/SiO_2 is quite strong. However, K_2SO_4 can suppress the acidity by neutralizing strong acid sites. This may be one of the important reasons why K_2SO_4 can improve the selectivity of V_2O_5/SiO_2 for many selective oxidations.
It has been shown by in situ XRD that V_2O_5 can disperse spontaneously onto the surface of silica gel, but the dispersion temperature is relatively high. The presence of H_2O vapour inhibits the dispersion of V_2O_5 to a certain extent, The dispersion process of V_2O_5 onto the surface of silica gel can be accelerated by using K_2SO_4 as an additive. The surface acidity of V_2O_5/SiO_2 is quite strong. However, K_2SO_4 can suppress the acidity by neutralizing strong acid sites. This may be one of the important reasons why K_2SO_4 can improve the selectivity of V_2O_5/SiO_2 for many selective oxidations.
1993, 9(02): 193-199
doi: 10.3866/PKU.WHXB19930210
Abstract:
A series of Hydroxy-Fe-Al Pillared Clays (FeAl-PILC) containing mixed-metal complexes with various Fe/Al ratios were prepared by two methods. The structure of the pillaring solution was studied by ~(27)Al-NMR, UV, ESR. The structure and thermal stability of the pillared clays were determined by XRD, DTA, UV-DRS. The results suggest that the basal spacings are 1.98—1.55 nm. The pillaring structure, surface area and thermal stability of FeAl-PILC are greatly affected by Fe/Al ratios in pillaring solution, FeAl-PILC products with Fe/Al ratio<0.5 have the pillaring structure the pillaring structure similar to that of Al-PILC, but FeAl-PILC products with Fe/Al ratio>0.5 have the pillaring structure similar to that of Fe-PILC. The basal spacings, surface area and thermal stability decrease with increasing of Fe/Al ratio.
A series of Hydroxy-Fe-Al Pillared Clays (FeAl-PILC) containing mixed-metal complexes with various Fe/Al ratios were prepared by two methods. The structure of the pillaring solution was studied by ~(27)Al-NMR, UV, ESR. The structure and thermal stability of the pillared clays were determined by XRD, DTA, UV-DRS. The results suggest that the basal spacings are 1.98—1.55 nm. The pillaring structure, surface area and thermal stability of FeAl-PILC are greatly affected by Fe/Al ratios in pillaring solution, FeAl-PILC products with Fe/Al ratio<0.5 have the pillaring structure the pillaring structure similar to that of Al-PILC, but FeAl-PILC products with Fe/Al ratio>0.5 have the pillaring structure similar to that of Fe-PILC. The basal spacings, surface area and thermal stability decrease with increasing of Fe/Al ratio.
1993, 9(02): 200-205
doi: 10.3866/PKU.WHXB19930211
Abstract:
In this paper, the property of orientation distribution function composed of second and fourth legendre polynomials was studied. It was pointed that this function can he used to describe four kinds of orientation distribution models. Corresponding to the four models, four regions of order parameters <P_2> and <P_4> were given. The orientation distribution polar graphs were observed when the order parameters were changing.
In this paper, the property of orientation distribution function composed of second and fourth legendre polynomials was studied. It was pointed that this function can he used to describe four kinds of orientation distribution models. Corresponding to the four models, four regions of order parameters <P_2> and <P_4> were given. The orientation distribution polar graphs were observed when the order parameters were changing.
1993, 9(02): 206-210
doi: 10.3866/PKU.WHXB19930212
Abstract:
High temperature oxide superconducters Ba_(2-x)Sr_xYCu_3O_(7-a) (x=0, 0.25, 0.50, 0.75, 1.0, 1.25) was prepared using high purity BaCO_3, SrCO_3, Y_2O_2, CuO. The super-conducting transition temperature (T_c) of the samples was measured by the four-probe technique for resistivity and alternative current method for magnetic suscepti-bility. The properties of the superconductots were examined by using powder XRD method, EXAFS, laser Raman spectroscopy, TG and high vacuum mass spectroscopy TPD. The amount of substitution x is larger, the T_c is lower, the lattice parameters a, b, c and V are smaller and the occupation of oxygen is lower. The catalytic activity of these oxides for CO oxidation was also detected by continuous flow system at 1 atm. The easier released oxygen of these oxides O_I, the most active oxygen in the lattice, is the active center in catalytic oxidation by CO. The reaction mechnism is the same as that of Ba_2YCu_3O_(7-δ). Furthermore, there is a linear relationship between the catalytic activity and the amount of O_I.
High temperature oxide superconducters Ba_(2-x)Sr_xYCu_3O_(7-a) (x=0, 0.25, 0.50, 0.75, 1.0, 1.25) was prepared using high purity BaCO_3, SrCO_3, Y_2O_2, CuO. The super-conducting transition temperature (T_c) of the samples was measured by the four-probe technique for resistivity and alternative current method for magnetic suscepti-bility. The properties of the superconductots were examined by using powder XRD method, EXAFS, laser Raman spectroscopy, TG and high vacuum mass spectroscopy TPD. The amount of substitution x is larger, the T_c is lower, the lattice parameters a, b, c and V are smaller and the occupation of oxygen is lower. The catalytic activity of these oxides for CO oxidation was also detected by continuous flow system at 1 atm. The easier released oxygen of these oxides O_I, the most active oxygen in the lattice, is the active center in catalytic oxidation by CO. The reaction mechnism is the same as that of Ba_2YCu_3O_(7-δ). Furthermore, there is a linear relationship between the catalytic activity and the amount of O_I.
1993, 9(02): 211-217
doi: 10.3866/PKU.WHXB19930213
Abstract:
The relationship of AES chemical shift with clement valence and electronegativity is discussed. It has also offered Auger electron kinetic energy and chemical shift data of various compounds. Besides, we apply AES chemical shift to study the adsorption of oxygen on zinc. This method can distinguish the states of zinc and oxygen. The interface reaction mechanism of Ti/SiO_2 during RTA treatment was explained with this method and the structure of lubrication film can be studied by AES.
The relationship of AES chemical shift with clement valence and electronegativity is discussed. It has also offered Auger electron kinetic energy and chemical shift data of various compounds. Besides, we apply AES chemical shift to study the adsorption of oxygen on zinc. This method can distinguish the states of zinc and oxygen. The interface reaction mechanism of Ti/SiO_2 during RTA treatment was explained with this method and the structure of lubrication film can be studied by AES.
1993, 9(02): 218-223
doi: 10.3866/PKU.WHXB19930214
Abstract:
The oscillations of m-C_6H_4(OH)_2-KBrO_3-H_2SO_4 (system A) as well as m-C_6H_4(OH)_2-KBrO_3-H_2SO_4-MnSO_4(system B) have been studied. The relations between induction period as well as oscillating period and the initial concentrations of reactants as well as temperatures of the system have been determined experimentally.
With low concentrations of Mn~(2+), system B exhibits two types of oscillation phenomena, ie, after the first type of oscillation and through a certain time interval, a second type of oscillation occurs. The characteristics of the two types of oscillation are different. The oscillating behavior of the first type of oscillation is similar to that of system A. The second type of oscillation may exhibit period-double-monotonous phenomena, which supports the idea in reference[1]. With higher concentrations of Mn~(2+), the second type of oscillation disappears and the system exhibit only one oscillation. System B is one of the typical examples showing the two types of oscillations.
The oscillations of m-C_6H_4(OH)_2-KBrO_3-H_2SO_4 (system A) as well as m-C_6H_4(OH)_2-KBrO_3-H_2SO_4-MnSO_4(system B) have been studied. The relations between induction period as well as oscillating period and the initial concentrations of reactants as well as temperatures of the system have been determined experimentally.
With low concentrations of Mn~(2+), system B exhibits two types of oscillation phenomena, ie, after the first type of oscillation and through a certain time interval, a second type of oscillation occurs. The characteristics of the two types of oscillation are different. The oscillating behavior of the first type of oscillation is similar to that of system A. The second type of oscillation may exhibit period-double-monotonous phenomena, which supports the idea in reference[1]. With higher concentrations of Mn~(2+), the second type of oscillation disappears and the system exhibit only one oscillation. System B is one of the typical examples showing the two types of oscillations.
1993, 9(02): 224-228
doi: 10.3866/PKU.WHXB19930215
Abstract:
The viscosities of polystyrene-b-poly (ethylene/propylene) diblock copolymer in mixed solvent of n-octane and benzene were measured. The influences of the constitution of the mixed solvent, temperature and concentration were on the viscosity investigated. During the micellization the solution viscosity increases rapidly. The results are consistent with the study on the micellization by light scattering. The average mass of micelleswas measurod and the hydrodynamic radius of gyrations were calculated.
The viscosities of polystyrene-b-poly (ethylene/propylene) diblock copolymer in mixed solvent of n-octane and benzene were measured. The influences of the constitution of the mixed solvent, temperature and concentration were on the viscosity investigated. During the micellization the solution viscosity increases rapidly. The results are consistent with the study on the micellization by light scattering. The average mass of micelleswas measurod and the hydrodynamic radius of gyrations were calculated.
1993, 9(02): 229-232
doi: 10.3866/PKU.WHXB19930216
Abstract:
This paper reported the studies on the microemulsion of TritonX-100, hexanol, Water and alkane system. △G_(s→i)~0, the variation of the standard Gibbs function for alcohol (Cosurfactant) migrating from the oil phase to the interfacial phase had been determined and discussed. △S_(s→i)~0, △H_(s→i), the variation of the standard entropy and standard enthalpy respectively, were calculated accordingly on thermodynamic relations and at various temperatures. The result showed the existence of a linear relationship between the above thermodynamic function and the carbon number in the alkane skeleton. Based upon these results, an interpretation and discussion on the stability and structure of the microemulsion were given.
This paper reported the studies on the microemulsion of TritonX-100, hexanol, Water and alkane system. △G_(s→i)~0, the variation of the standard Gibbs function for alcohol (Cosurfactant) migrating from the oil phase to the interfacial phase had been determined and discussed. △S_(s→i)~0, △H_(s→i), the variation of the standard entropy and standard enthalpy respectively, were calculated accordingly on thermodynamic relations and at various temperatures. The result showed the existence of a linear relationship between the above thermodynamic function and the carbon number in the alkane skeleton. Based upon these results, an interpretation and discussion on the stability and structure of the microemulsion were given.
1993, 9(02): 233-237
doi: 10.3866/PKU.WHXB19930217
Abstract:
We detailed the stability of ELM with glutamic acid dialkyl esters as surfactants by moving single drop method. It is a new method which can overcome the weakness as the surface area of W/O emulsion drops cannot be measared accurately because the diameters of the emulsion drops are widely dispersed in the stirring method. Moreover, it may avoid the membrane breakup causing by mechanical stirring. It is a available method to measure the stability of ELM.
We detailed the stability of ELM with glutamic acid dialkyl esters as surfactants by moving single drop method. It is a new method which can overcome the weakness as the surface area of W/O emulsion drops cannot be measared accurately because the diameters of the emulsion drops are widely dispersed in the stirring method. Moreover, it may avoid the membrane breakup causing by mechanical stirring. It is a available method to measure the stability of ELM.
1993, 9(02): 238-241
doi: 10.3866/PKU.WHXB19930218
Abstract:
IR multi-photon dissociation (IRMPD) of trimethyl phosphite has been carried out by a TEA CO_2 laser. The fluorescence spectra near 326 and 520 nm were assigned to electronically excited PO~* and HPO~* radical respectively. Sample presure depen-dences of fluorescence intensity were measured. Possible mechanism was suggested.
IR multi-photon dissociation (IRMPD) of trimethyl phosphite has been carried out by a TEA CO_2 laser. The fluorescence spectra near 326 and 520 nm were assigned to electronically excited PO~* and HPO~* radical respectively. Sample presure depen-dences of fluorescence intensity were measured. Possible mechanism was suggested.
1993, 9(02): 242-246
doi: 10.3866/PKU.WHXB19930219
Abstract:
Studies on pervaporation separation of alcohol/water mixture and pervaporation-aided catalytic esterification reaction have been carried out using a laboratory reactor equipped with a hydrophilic polyvinyl alcohol membrane. It was found that the flux and the separation factor of the membrane varied with the composition and temperature of the alcohol/water mixture and the thickness of the membrane. On the other hand, the rate and conversion of the esterification reactions increased as the flux and the A/V ratio of the membrane were increased. The conversion of the pervaporation-aided esterification of acetic acid by ethanol approached 96—99% in our reaction device, and the time required to attain 95% conversion t_(95) reduced by half as compared with that of the blank reaction. For the pervaporation-aided esterification of salicylic acid by methanol, the reaction conversion increased by 1.5 times as well.
Studies on pervaporation separation of alcohol/water mixture and pervaporation-aided catalytic esterification reaction have been carried out using a laboratory reactor equipped with a hydrophilic polyvinyl alcohol membrane. It was found that the flux and the separation factor of the membrane varied with the composition and temperature of the alcohol/water mixture and the thickness of the membrane. On the other hand, the rate and conversion of the esterification reactions increased as the flux and the A/V ratio of the membrane were increased. The conversion of the pervaporation-aided esterification of acetic acid by ethanol approached 96—99% in our reaction device, and the time required to attain 95% conversion t_(95) reduced by half as compared with that of the blank reaction. For the pervaporation-aided esterification of salicylic acid by methanol, the reaction conversion increased by 1.5 times as well.
1993, 9(02): 247-251
doi: 10.3866/PKU.WHXB19930220
Abstract:
The metastable molecule CS(a~3Π) has been obtained, by the energy transfer reaction of He(2~3S) with CS_2 in a discharge-flow system The technique of fixed observation-point was used to obtained the quenching rate constants of CS(a~3Π) with various reagents CO_2, CS_2, ICl, H_2O, NOCl, CH_2Cl_2, CHF_2Cl and SF_6. Thc mechanism for quenching has been discussed.
The metastable molecule CS(a~3Π) has been obtained, by the energy transfer reaction of He(2~3S) with CS_2 in a discharge-flow system The technique of fixed observation-point was used to obtained the quenching rate constants of CS(a~3Π) with various reagents CO_2, CS_2, ICl, H_2O, NOCl, CH_2Cl_2, CHF_2Cl and SF_6. Thc mechanism for quenching has been discussed.
1993, 9(02): 252-255
doi: 10.3866/PKU.WHXB19930221
Abstract:
The electronic structure and chemical bonds in La(NO_3)_3·bipy·2H_2O·(B-15-C-5) has been studied by INDO method. The results indicated that 5d orbitals of La have largest contribution and 4f orbitals have hardly contribution in all valence orbitals of La in coordinate bonds of La—O and La—N. B-15-C-5 does not coordinate with La, but it effects formation of the complex and chemical bond.
The electronic structure and chemical bonds in La(NO_3)_3·bipy·2H_2O·(B-15-C-5) has been studied by INDO method. The results indicated that 5d orbitals of La have largest contribution and 4f orbitals have hardly contribution in all valence orbitals of La in coordinate bonds of La—O and La—N. B-15-C-5 does not coordinate with La, but it effects formation of the complex and chemical bond.
1993, 9(02): 256-262
doi: 10.3866/PKU.WHXB19930222
Abstract:
The influences of the side phenyls (PHs) on the electronic energy band-structure of polydiaeetylenes have been studied by quantum-chemical EHCO-ASED method. When the backbone are changed from polybutatriene(PBT) to polydiacetylene(PDA), the band widths △E_(HO) and △E_(LU) decrease montonically from those of PBT to PDA, but the energy gap decreases from E_g(PBT)=0.43 eV to the minimum E_g(MIN)=0.11 eV firstly, and then increases to E_g(PDA)=1.43 eV (Table 2). Corresponding to the minimum, there is a symmetry inversion for HOCO and LUCO (Table 3). When PHs are coplanar with the backbone (PBT-PH1 and PDA-PH1), they will take part in the conjugation of the system to a certain extent (Table 5), and cause: (I) energy gaps E_g (PBT-PH1) and E_g(PDA-PH1) to change to 56% of E_g(PBT) and 76% of E_g(PDA) respectively (Table 4); (II) the band widths, both ΔE_(HO) and ΔE_(LU) for PBT-PH1 and PDA PH1, to decrease to 40—50% of those of PBT and PDA respectively (Table 4). When PHs are perpendicular to the plane of the backbone (PBT-PH2 and PDA-PH_2), the influences of PHs on the band structure are limitted (Table 4). According to the results and the discussions in this paper, it is shown that the intrinsic semiconductor characteristic of polydiacetylenes is hard to be improved obviously by the side group.
The influences of the side phenyls (PHs) on the electronic energy band-structure of polydiaeetylenes have been studied by quantum-chemical EHCO-ASED method. When the backbone are changed from polybutatriene(PBT) to polydiacetylene(PDA), the band widths △E_(HO) and △E_(LU) decrease montonically from those of PBT to PDA, but the energy gap decreases from E_g(PBT)=0.43 eV to the minimum E_g(MIN)=0.11 eV firstly, and then increases to E_g(PDA)=1.43 eV (Table 2). Corresponding to the minimum, there is a symmetry inversion for HOCO and LUCO (Table 3). When PHs are coplanar with the backbone (PBT-PH1 and PDA-PH1), they will take part in the conjugation of the system to a certain extent (Table 5), and cause: (I) energy gaps E_g (PBT-PH1) and E_g(PDA-PH1) to change to 56% of E_g(PBT) and 76% of E_g(PDA) respectively (Table 4); (II) the band widths, both ΔE_(HO) and ΔE_(LU) for PBT-PH1 and PDA PH1, to decrease to 40—50% of those of PBT and PDA respectively (Table 4). When PHs are perpendicular to the plane of the backbone (PBT-PH2 and PDA-PH_2), the influences of PHs on the band structure are limitted (Table 4). According to the results and the discussions in this paper, it is shown that the intrinsic semiconductor characteristic of polydiacetylenes is hard to be improved obviously by the side group.
1993, 9(02): 263-267
doi: 10.3866/PKU.WHXB19930223
Abstract:
The activity coefficients of TBP in n-cetane have been determined by cryoscopic method. This method is simpler, more rapid and the range of concentration studied is wider than other physico-chemical methods. It may be used for the determination of activity coefficients of major extractants in n-cetane.
The activity coefficients of TBP in n-cetane have been determined by cryoscopic method. This method is simpler, more rapid and the range of concentration studied is wider than other physico-chemical methods. It may be used for the determination of activity coefficients of major extractants in n-cetane.
Study on the Ferrocene-Containing Ploynuculi Metal Complexes Quenching Luminescence of *[Cr(bpy)3]3+
1993, 9(02): 268-272
doi: 10.3866/PKU.WHXB19930224
Abstract:
Ferrocene-containing ploynuclear metal complexes M(Fe-C(CH_3)=N N=CSSR)_2 (M=Ni~(2+), Cu~(2+), Zn~(2+), Pd~(2+), Co~(2+), Cd~(2+), R=CH_3, CH_2φ) have been synthesized and characterized by cyclic voltummetry. It has been found that this kind of complexes can quench the luminescence of [Cr(bpy)_3]~(3+) efficiencily. The Stern-Volmer plot is linear and yield the bimolecular quenching rate constants in order of 10~8～10~9 dm~3·mol~(-1)·s~(-1). The quenching process is carrid out through electron transfer and energy transfer mechanism.
Ferrocene-containing ploynuclear metal complexes M(Fe-C(CH_3)=N N=CSSR)_2 (M=Ni~(2+), Cu~(2+), Zn~(2+), Pd~(2+), Co~(2+), Cd~(2+), R=CH_3, CH_2φ) have been synthesized and characterized by cyclic voltummetry. It has been found that this kind of complexes can quench the luminescence of [Cr(bpy)_3]~(3+) efficiencily. The Stern-Volmer plot is linear and yield the bimolecular quenching rate constants in order of 10~8～10~9 dm~3·mol~(-1)·s~(-1). The quenching process is carrid out through electron transfer and energy transfer mechanism.
1993, 9(02): 273-276
doi: 10.3866/PKU.WHXB19930225
Abstract:
An artificial membrane consisting of pricramic acid in nitrobenzene was used as an oil phase imposed between two aqueous phases. The right one contained trimethyl-slearylammonium chloride and aicohol; and the left contained sucrose solution (or H_2O).
We found that this system exhibited rhythmic oscillation of electrical potential. The amplitude of the oscillations was between 20—150 mV. The oscillations were observed even when ethyl alcohol was absent in the aqueous of trimethylslearylammonium Chloride, and the increase in amplitude of oscillation with time was found to be less in the presence of sucrose. Some of the expremental results have been explained.
An artificial membrane consisting of pricramic acid in nitrobenzene was used as an oil phase imposed between two aqueous phases. The right one contained trimethyl-slearylammonium chloride and aicohol; and the left contained sucrose solution (or H_2O).
We found that this system exhibited rhythmic oscillation of electrical potential. The amplitude of the oscillations was between 20—150 mV. The oscillations were observed even when ethyl alcohol was absent in the aqueous of trimethylslearylammonium Chloride, and the increase in amplitude of oscillation with time was found to be less in the presence of sucrose. Some of the expremental results have been explained.
1993, 9(02): 277-280
doi: 10.3866/PKU.WHXB19930226
Abstract:
The photoelectrochemical polymerization process: monomer first polymerizes into low polymer and then the low polymer may be oxidized into polymerfilm.
monomer→low polymer→polymerfilm
Irradiation can accelerate the formation of low polymer. The rate of the first step for pyrrole and thiophene is slow, and the second step for aniline is slow. When the film is formed, it can speed up the rate of film formation.
The photoelectrochemical polymerization process: monomer first polymerizes into low polymer and then the low polymer may be oxidized into polymerfilm.
monomer→low polymer→polymerfilm
Irradiation can accelerate the formation of low polymer. The rate of the first step for pyrrole and thiophene is slow, and the second step for aniline is slow. When the film is formed, it can speed up the rate of film formation.
1993, 9(02): 281-287
doi: 10.3866/PKU.WHXB19930227
Abstract:
