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1992 Volume 8 Issue 2
1992, 8(02): 145-147
doi: 10.3866/PKU.WHXB19920201
Abstract:
Time-of-flight mass spectrum of C_nB~- has been recorded on a selfbuilt instrument with laser vaporization of tetraphenylboron sodium. By analysis of the com-position of the anions, it is found that number of the boron atoms in any of these ions equals to the number of the charges carried by the anion, and the sum of the numbers of the carbon and boron atoms in these species are always the odd numbers. The experimental results show that boron atom has a strong tendency to attract an electron so that those C_nB~- will have similar electronic structures as C_n, and carbon clusters with odd members are always more stable than their even neighbors.
Time-of-flight mass spectrum of C_nB~- has been recorded on a selfbuilt instrument with laser vaporization of tetraphenylboron sodium. By analysis of the com-position of the anions, it is found that number of the boron atoms in any of these ions equals to the number of the charges carried by the anion, and the sum of the numbers of the carbon and boron atoms in these species are always the odd numbers. The experimental results show that boron atom has a strong tendency to attract an electron so that those C_nB~- will have similar electronic structures as C_n, and carbon clusters with odd members are always more stable than their even neighbors.
1992, 8(02): 148-152
doi: 10.3866/PKU.WHXB19920202
Abstract:
In this paper SSIMS (Static Secondary Ion Mass Spectrometry) combined with XPS was used for measuring the surface state and constitution of selvage layers of novel supported catalysts MoO_3-CoO/TiO_2-Al_2O_3. Because of very high surface sensitivity, SSIMS has been used successfully in characterization of the surface state or species of active component supported on the surface of the carrier (TiO_2-Al_2O_3), as measuring the intensity ratios (e.g. I_(114_(MoO~+))/I_(27_(Al~+)), I_(59_(Co~+))/I_(27_(Al~+)), etc.) of different secondary ions. Also, SSIMS has been used for determining the constitution of selvage layers of novel supported catalysts MoO_3-CoO/TiO_2-Al_2O_3, as measuring the intensity of secondary ion as a funcnion of time (e.g. I~(114)MoO~+(t), I~(59)Co~+(t), etc.). The results of the dispersed amount of active component MoO_3 on the surface of carrier by SSIMS are in line with those obtained by PASCA (Positron Annihilation Spectroscopy for Chemical Analysis) and LRS (Laser Raman Spectroscopy). Furthermore, the results of surface state and constitution of selvage layers of novel supported catalysts MoO_3-CoO/TiO_2-Al_2O_3 can be correlated with the HDS (hydrodesulfurization) reactivity of thiophene at the atmosphere pressure. And the satisfactory result was obtained. All these mentiond above illustrate that after improving some experimental techniques, the SSIMS can be used as a powerful tool for measuring the surface state and the constitution of selvage layers of supported catalysts simply and directly.
In this paper SSIMS (Static Secondary Ion Mass Spectrometry) combined with XPS was used for measuring the surface state and constitution of selvage layers of novel supported catalysts MoO_3-CoO/TiO_2-Al_2O_3. Because of very high surface sensitivity, SSIMS has been used successfully in characterization of the surface state or species of active component supported on the surface of the carrier (TiO_2-Al_2O_3), as measuring the intensity ratios (e.g. I_(114_(MoO~+))/I_(27_(Al~+)), I_(59_(Co~+))/I_(27_(Al~+)), etc.) of different secondary ions. Also, SSIMS has been used for determining the constitution of selvage layers of novel supported catalysts MoO_3-CoO/TiO_2-Al_2O_3, as measuring the intensity of secondary ion as a funcnion of time (e.g. I~(114)MoO~+(t), I~(59)Co~+(t), etc.). The results of the dispersed amount of active component MoO_3 on the surface of carrier by SSIMS are in line with those obtained by PASCA (Positron Annihilation Spectroscopy for Chemical Analysis) and LRS (Laser Raman Spectroscopy). Furthermore, the results of surface state and constitution of selvage layers of novel supported catalysts MoO_3-CoO/TiO_2-Al_2O_3 can be correlated with the HDS (hydrodesulfurization) reactivity of thiophene at the atmosphere pressure. And the satisfactory result was obtained. All these mentiond above illustrate that after improving some experimental techniques, the SSIMS can be used as a powerful tool for measuring the surface state and the constitution of selvage layers of supported catalysts simply and directly.
1992, 8(02): 153-155
doi: 10.3866/PKU.WHXB19920203
Abstract:
1992, 8(02): 156-161
doi: 10.3866/PKU.WHXB19920204
Abstract:
At the level of INDO/CI methods, using the program for calculations of the second-order nonlinear susceptibilites (β_(ijk)) written by ourselves, we calculated the β_(ijk) of aniline, nitrobenzene, ρ-nitroaniline and 4-nitro-4′-aminostilbene and inves-tigated dependence of β_(ijk) on LASER frequencies. It is shown that the intramolecular charge transfer is the origin of the nonlinear optics phenomenon and the LASER field plays an important role to the magnitude and direction of the second-order nonlinear optics susceptibility. When the LASER frequency is close to the molecular resonance frequency, the second-order nonlinear susceptibility becomes larger, before and after the resonance freguence, β_(ijk) changes its sign and the Kleinman symmetry begins to break down.
1992, 8(02): 162-170
doi: 10.3866/PKU.WHXB19920205
Abstract:
The conductance bridge was used to measure the molar conductances for H_2O-C_2H_5OH-NaCl system and the headspace gas chromatograph was used to measure the activity of water and ethanol in H_2O-C_2H_5OH-(NaCl, KCl, KBr) systems. The associ-ation constant, limiting molar conductance and distance parameter in H_2O-C_2H_5OH-MX (NaCl, KCl, CsCl, KBr) systems are regressed from Lee-Wheaton model. The results show the orders of association ability of ions are Na~+>K~+>Cs~+ and Cl~->Br~-, and these four salts form ion-pair separated by solvent in ethanol. The improved Pitzer-Li equation is applied to calculate the short-range term of activity coefficient. The association of ions is taken into account and the results show that the procedure of our calculation is reasonable. When the concentration of salt increases, the activity of water decreases, but the activity of C_2H_5OH increases. It means that these salts present a salting-in effect for water but salting-out effect for C_2H_5OH.
The conductance bridge was used to measure the molar conductances for H_2O-C_2H_5OH-NaCl system and the headspace gas chromatograph was used to measure the activity of water and ethanol in H_2O-C_2H_5OH-(NaCl, KCl, KBr) systems. The associ-ation constant, limiting molar conductance and distance parameter in H_2O-C_2H_5OH-MX (NaCl, KCl, CsCl, KBr) systems are regressed from Lee-Wheaton model. The results show the orders of association ability of ions are Na~+>K~+>Cs~+ and Cl~->Br~-, and these four salts form ion-pair separated by solvent in ethanol. The improved Pitzer-Li equation is applied to calculate the short-range term of activity coefficient. The association of ions is taken into account and the results show that the procedure of our calculation is reasonable. When the concentration of salt increases, the activity of water decreases, but the activity of C_2H_5OH increases. It means that these salts present a salting-in effect for water but salting-out effect for C_2H_5OH.
1992, 8(02): 171-174
doi: 10.3866/PKU.WHXB19920206
Abstract:
The electronic structure and coordinating activation of chemical bonds of η~6-benzene complex of neodymium have been studied by INDO method. The results show that the coordination of NdCl_3 to AlCl_3 through six μ_2-Cl may decrease the Lewis acidity of the Nd ion, the charge difference on Nd and Cl, and polarity of Nd—Cl bonds, which leads to the increasing of the solubility of NdCl_3 in benzene and the stability of the η~6-benzene complex of neodymium.
The coordination of benzene molecule to neodymium ion decreases the strength of C—C and C—H bonds in benzene and enhances the alkylation affinity of the benzene ring obviously.
The electronic structure and coordinating activation of chemical bonds of η~6-benzene complex of neodymium have been studied by INDO method. The results show that the coordination of NdCl_3 to AlCl_3 through six μ_2-Cl may decrease the Lewis acidity of the Nd ion, the charge difference on Nd and Cl, and polarity of Nd—Cl bonds, which leads to the increasing of the solubility of NdCl_3 in benzene and the stability of the η~6-benzene complex of neodymium.
The coordination of benzene molecule to neodymium ion decreases the strength of C—C and C—H bonds in benzene and enhances the alkylation affinity of the benzene ring obviously.
1992, 8(02): 175-180
doi: 10.3866/PKU.WHXB19920207
Abstract:
The critical micelle concentration (CMC) of aqueous C_8-lecithin solutions was measured as a function of temperature, salt type and concentration by laser light scattering. The CMC's are raised linearly with the concentration of KI, but show a broad maximum in their dependence on the concentration of KCl. As temperature increases, the CMC's of all the systems are raised. The negative values of the ladder spacing and standard enthalpy of the micelle formation deduced from the CMC values indicate that micelle formation is a spontaneous process. Compared with the salt free system, the micelles in the KI added (>/0.35 mol·L~(-1)) solution are easier to form and more stable. The average aggregation number of the micelles and the micelle growth parameter Δμ obtained from the present experiment are quite consistent with those obtained previously from the coexistence curves.
The critical micelle concentration (CMC) of aqueous C_8-lecithin solutions was measured as a function of temperature, salt type and concentration by laser light scattering. The CMC's are raised linearly with the concentration of KI, but show a broad maximum in their dependence on the concentration of KCl. As temperature increases, the CMC's of all the systems are raised. The negative values of the ladder spacing and standard enthalpy of the micelle formation deduced from the CMC values indicate that micelle formation is a spontaneous process. Compared with the salt free system, the micelles in the KI added (>/0.35 mol·L~(-1)) solution are easier to form and more stable. The average aggregation number of the micelles and the micelle growth parameter Δμ obtained from the present experiment are quite consistent with those obtained previously from the coexistence curves.
1992, 8(02): 181-185
doi: 10.3866/PKU.WHXB19920208
Abstract:
The 1,2-cycloaddition reaction mechanism of singlet molecular oxygen ~1O_2 with imidazole has been investigated by semiempirical molecular orbital AM1 method and energy gradient technique. The calculated results show that the mentioned reaction is a stepwise reaction via a diradical intermediate. The barrier height of the first step reaction is 39.2 kJ·mol~(-1) while the second step reaction is 150.5 kJ·mol~(-1). The second step reaction is the rate determining step.
The 1,2-cycloaddition reaction mechanism of singlet molecular oxygen ~1O_2 with imidazole has been investigated by semiempirical molecular orbital AM1 method and energy gradient technique. The calculated results show that the mentioned reaction is a stepwise reaction via a diradical intermediate. The barrier height of the first step reaction is 39.2 kJ·mol~(-1) while the second step reaction is 150.5 kJ·mol~(-1). The second step reaction is the rate determining step.
1992, 8(02): 186-190
doi: 10.3866/PKU.WHXB19920209
Abstract:
Mark-Houwink equations of ring-shaped and linear polystyrene in ethyl acetate were obtained as:
[η]_r=1.91×10~(-2)·M~(0.607) and [η]_1=4.06×10~(-2)·M~(0.572).
The excimer fluorescent effect of the ring-shaped and linear polystyrene was studied. According to the difference of flexibility between ring-shaped and linear polymer coils in their dilute solution formed by not od solvent the difference of the excimer effect between them may be interpreted. Two correlation linear equations concerning to the (I_E/I_M)_(c→0) versus molecular weight of the samples were obtained.
(I_E/I_m)_(r,c→0)=1.91+3.40×10~(-6)·M
and (I_E/I_m)_(l,c→0)=2.15+3.05×10~(-6)·M
Mark-Houwink equations of ring-shaped and linear polystyrene in ethyl acetate were obtained as:
[η]_r=1.91×10~(-2)·M~(0.607) and [η]_1=4.06×10~(-2)·M~(0.572).
The excimer fluorescent effect of the ring-shaped and linear polystyrene was studied. According to the difference of flexibility between ring-shaped and linear polymer coils in their dilute solution formed by not od solvent the difference of the excimer effect between them may be interpreted. Two correlation linear equations concerning to the (I_E/I_M)_(c→0) versus molecular weight of the samples were obtained.
(I_E/I_m)_(r,c→0)=1.91+3.40×10~(-6)·M
and (I_E/I_m)_(l,c→0)=2.15+3.05×10~(-6)·M
1992, 8(02): 191-196
doi: 10.3866/PKU.WHXB19920210
Abstract:
The stability of the aqueous solution, surface activity, stability of the foam and foaming ability of the mixture, formed by mixing TX-100 (C_8H_(17)C_6H_4(OC_2H_4)_(9.8)OH; C_8ΦE_(9.8)) and its sulfate (C_8H_(17)C_6H_4(OC_2H_4)_(9.8)OSO_3Na; C_8ΦE_(9.8)S) with cationic surfactants (C_nH_(2n+1)+NC_5H_5Br; C_nPy, n=10, 12, 14; C_mH_(2m+1)N(CH_3)_3Br; C_mNM_3, m=16, 18), have been measured. The results show that it can not only form a stable aqueous solution of cationic-anionic surfactant mixture, but also promote the solubility of cationic surfactants very much when C_8ΦE_(9.8)S mix with cationic surfactants; The surface activity of the foam and the foaming ability of C_8ΦE_(9.8)S-C_nPy will reach the maximum when n equate to 12. The surface activity and the stability of the foma of C_8ΦE_(9.8)S-C_(18)NM_3 are much higher than that of C_8ΦE_(9.8)S-C_(18)NM_3, but the foaming ability of C_8ΦE_(9.8)S-C_(18)NM_3 is much higher than that of C_8ΦE_(9.8)S-C_(18)NM_3. Theoretical calculation shows that the attraction between C_8ΦE_(9.8)S and C_(18)NM_3 is much stronger than that between C_8ΦE_(9.8)S and C_(18)NM_3.
The stability of the aqueous solution, surface activity, stability of the foam and foaming ability of the mixture, formed by mixing TX-100 (C_8H_(17)C_6H_4(OC_2H_4)_(9.8)OH; C_8ΦE_(9.8)) and its sulfate (C_8H_(17)C_6H_4(OC_2H_4)_(9.8)OSO_3Na; C_8ΦE_(9.8)S) with cationic surfactants (C_nH_(2n+1)+NC_5H_5Br; C_nPy, n=10, 12, 14; C_mH_(2m+1)N(CH_3)_3Br; C_mNM_3, m=16, 18), have been measured. The results show that it can not only form a stable aqueous solution of cationic-anionic surfactant mixture, but also promote the solubility of cationic surfactants very much when C_8ΦE_(9.8)S mix with cationic surfactants; The surface activity of the foam and the foaming ability of C_8ΦE_(9.8)S-C_nPy will reach the maximum when n equate to 12. The surface activity and the stability of the foma of C_8ΦE_(9.8)S-C_(18)NM_3 are much higher than that of C_8ΦE_(9.8)S-C_(18)NM_3, but the foaming ability of C_8ΦE_(9.8)S-C_(18)NM_3 is much higher than that of C_8ΦE_(9.8)S-C_(18)NM_3. Theoretical calculation shows that the attraction between C_8ΦE_(9.8)S and C_(18)NM_3 is much stronger than that between C_8ΦE_(9.8)S and C_(18)NM_3.
1992, 8(02): 197-201
doi: 10.3866/PKU.WHXB19920211
Abstract:
The group contribution mothod has been used to calculate the values of solubility parameter, intrinsic viscosity, Mark-Houwink parameters of ring-and linear shaped polystyrene according to cohesive energy, molar volume, molar attraction constant. All these calculating results were also experimentally demonstrated. Futhermore, the theoretical significance of the value of critical molecular weight used calculating the K_(θ,r) of ring-shaped polymer is detaily discussed.
The group contribution mothod has been used to calculate the values of solubility parameter, intrinsic viscosity, Mark-Houwink parameters of ring-and linear shaped polystyrene according to cohesive energy, molar volume, molar attraction constant. All these calculating results were also experimentally demonstrated. Futhermore, the theoretical significance of the value of critical molecular weight used calculating the K_(θ,r) of ring-shaped polymer is detaily discussed.
1992, 8(02): 202-206
doi: 10.3866/PKU.WHXB19920212
Abstract:
In this paper the transient behavior of n-InP semiconductor electrode in Fe~(3+)/Fe~(2+) solution using current step method is studied. From the equivalent circuit of the n-InP electrode under irradiation, a theoretical model for the change of photopoten-tial is derived in the presence of a small signal. The results of the experiments confirm the derivation. On the basis of the experiments and the theoretical model we also develop a method for measuring the capacitance of the space charge layer (C_(sc)). The observation of the influences of various light intensities is studied also.
In this paper the transient behavior of n-InP semiconductor electrode in Fe~(3+)/Fe~(2+) solution using current step method is studied. From the equivalent circuit of the n-InP electrode under irradiation, a theoretical model for the change of photopoten-tial is derived in the presence of a small signal. The results of the experiments confirm the derivation. On the basis of the experiments and the theoretical model we also develop a method for measuring the capacitance of the space charge layer (C_(sc)). The observation of the influences of various light intensities is studied also.
1992, 8(02): 207-211
doi: 10.3866/PKU.WHXB19920213
Abstract:
The effect of metal ions of different valences on the conformation of DNA molecules by UV spectra has been studied. The result shows that a hypochromicity occurs at 257 nm after adding metal ions, and the degree of hypochromicity depends on the valence of metal ions. The higher the valence of metal ion, the stronger the hypochromicity. It follows that interactions of metal ions with DNA molecules cause contraction of DNA conformation. The higher the valence of the metal ion, the stronger the effect, eventually, DNA condensation may be induced. The phenomena has been disscussed according to Modern Polyelectrolyte Theory, and the result is satisfactory.
The effect of metal ions of different valences on the conformation of DNA molecules by UV spectra has been studied. The result shows that a hypochromicity occurs at 257 nm after adding metal ions, and the degree of hypochromicity depends on the valence of metal ions. The higher the valence of metal ion, the stronger the hypochromicity. It follows that interactions of metal ions with DNA molecules cause contraction of DNA conformation. The higher the valence of the metal ion, the stronger the effect, eventually, DNA condensation may be induced. The phenomena has been disscussed according to Modern Polyelectrolyte Theory, and the result is satisfactory.
1992, 8(02): 212-217
doi: 10.3866/PKU.WHXB19920214
Abstract:
The state of surface site of catalyst for CO hydrogenation was studied with TPSR, TPR and TR. Results show that there are two kinds of active sites on the surface of Ni/Al_2O_3 catalysts. The site A comes from crystallite of Ni exposed on the surface, while the site B comes from Ni-Al intermediate which formed by the strong interaction of Ni with the support Al_2O_3. Results also show that the CO can be adsorbed on both sites, if active hydrogen is adsorbed on the surface, the ratio of adsorbed CO on both sites will be changed.
The state of surface site of catalyst for CO hydrogenation was studied with TPSR, TPR and TR. Results show that there are two kinds of active sites on the surface of Ni/Al_2O_3 catalysts. The site A comes from crystallite of Ni exposed on the surface, while the site B comes from Ni-Al intermediate which formed by the strong interaction of Ni with the support Al_2O_3. Results also show that the CO can be adsorbed on both sites, if active hydrogen is adsorbed on the surface, the ratio of adsorbed CO on both sites will be changed.
1992, 8(02): 218-225
doi: 10.3866/PKU.WHXB19920215
Abstract:
The equation of transient response to a small amplitude perturbation of potential step for multi-time constant electrode processes was deduced, and a method of calculating the parameters in the equation of transient response containing one, two or three time constants was proposed. Using this method, the number of time constants can be determened unambigiously, and the kinetic parameters of the electrode process studied can be estimated easily.
The equation of transient response to a small amplitude perturbation of potential step for multi-time constant electrode processes was deduced, and a method of calculating the parameters in the equation of transient response containing one, two or three time constants was proposed. Using this method, the number of time constants can be determened unambigiously, and the kinetic parameters of the electrode process studied can be estimated easily.
1992, 8(02): 226-231
doi: 10.3866/PKU.WHXB19920216
Abstract:
In this work, we have measured the second-order rate constants of the reactions O(~3P)+CS_2 and N(~4S)+CS_2 over temperature range 293-500 K using discharge flow-chemiluminescence method. The results obtained are as follows: k_1=(8.44_(-0.61)~(+0.66))×10~(-11)exp ((-2.1±0. 1)×4.184 kJ·mol~(-1)/RT) cm~3·molec~(-1). s~(-1) (for O(~3P) + CS_2) and k_2=(3.09_(0.80)~(+1.08))×10~(-11) exp((-1.87±0.22)×4.184 kJ·mol~(-1)/RT)cm~3·molec~(-1)·s~(-1)(for N(~4S)+CS_2), respectively. The value of k_1 is in od agreement with literature results. With our best knowledge, no value of k_2 has been reported. In addition, we have calculated the structural parameters and energies of the intermediates NCS_2 and NSCS of the reaction N(~4S)+CS_2 by using approximate quantum chemistry theory. The minimum potential energy curves via reaction coordinates have also been calculated. A discussion of the reaction mechanism is presented.
In this work, we have measured the second-order rate constants of the reactions O(~3P)+CS_2 and N(~4S)+CS_2 over temperature range 293-500 K using discharge flow-chemiluminescence method. The results obtained are as follows: k_1=(8.44_(-0.61)~(+0.66))×10~(-11)exp ((-2.1±0. 1)×4.184 kJ·mol~(-1)/RT) cm~3·molec~(-1). s~(-1) (for O(~3P) + CS_2) and k_2=(3.09_(0.80)~(+1.08))×10~(-11) exp((-1.87±0.22)×4.184 kJ·mol~(-1)/RT)cm~3·molec~(-1)·s~(-1)(for N(~4S)+CS_2), respectively. The value of k_1 is in od agreement with literature results. With our best knowledge, no value of k_2 has been reported. In addition, we have calculated the structural parameters and energies of the intermediates NCS_2 and NSCS of the reaction N(~4S)+CS_2 by using approximate quantum chemistry theory. The minimum potential energy curves via reaction coordinates have also been calculated. A discussion of the reaction mechanism is presented.
1992, 8(02): 232-235
doi: 10.3866/PKU.WHXB19920217
Abstract:
~(31)P NMR spectra during the hydrolysis process of thiophosphate(A) ??? in neutral, acid and basic media were recorded. By analyzing the ~(31)P NMR date obtained, hydrolysis mechanism was confirmed. Information of hydrolysis rate in different media was also obtained. In addition, the solvent effects of ~(31)P NMR of thiophosphate were investigated in detail.
~(31)P NMR spectra during the hydrolysis process of thiophosphate(A) ??? in neutral, acid and basic media were recorded. By analyzing the ~(31)P NMR date obtained, hydrolysis mechanism was confirmed. Information of hydrolysis rate in different media was also obtained. In addition, the solvent effects of ~(31)P NMR of thiophosphate were investigated in detail.
1992, 8(02): 236-239
doi: 10.3866/PKU.WHXB19920218
Abstract:
The reactions of OH radical with C_2H_2 and C_2H_4 have been studied with ther- modynamic and kinetic methods based on ab initio level. The changes of the ther-modynamic function of the reactions were calculated at a range of 200-1600 K of temperature. The results indicate that both of the reactions are exothermic, which is 135.60±2.76 and 100.58±7.32 kJ·mol~(-1) respectively at the cited temperature in-tervals. The reaction of OH radical with C_2H_2 can proceed easier than with C_2H_4. Also, the A factor and the rate constant of the reactions were calculated with transition state theory. Pressure dependence of the rate constants was found. At 298 K, 80.0 kPa, the rate constant k_1 equals 5.09×10~5 m~3·mol~(-1)·s~(-1), the experimental data is (4.49±1.63)×10~5 m~3·mol~(-1)·s~(-1); at 299.2 K, 88.31 kPa, k_2 is equal to 6.64×10~6 m~3·mol~(-1)·s~(-1), and the experimental data is (4.73±4.76)×10~6 m~3·mol~(-1)·s~(-1), which are in od agreement.
The reactions of OH radical with C_2H_2 and C_2H_4 have been studied with ther- modynamic and kinetic methods based on ab initio level. The changes of the ther-modynamic function of the reactions were calculated at a range of 200-1600 K of temperature. The results indicate that both of the reactions are exothermic, which is 135.60±2.76 and 100.58±7.32 kJ·mol~(-1) respectively at the cited temperature in-tervals. The reaction of OH radical with C_2H_2 can proceed easier than with C_2H_4. Also, the A factor and the rate constant of the reactions were calculated with transition state theory. Pressure dependence of the rate constants was found. At 298 K, 80.0 kPa, the rate constant k_1 equals 5.09×10~5 m~3·mol~(-1)·s~(-1), the experimental data is (4.49±1.63)×10~5 m~3·mol~(-1)·s~(-1); at 299.2 K, 88.31 kPa, k_2 is equal to 6.64×10~6 m~3·mol~(-1)·s~(-1), and the experimental data is (4.73±4.76)×10~6 m~3·mol~(-1)·s~(-1), which are in od agreement.
1992, 8(02): 240-242
doi: 10.3866/PKU.WHXB19920219
Abstract:
Measurements of ~2H NMR spectra and phase diagrams showed that the stability of SDS/C_(10)OH/solvents lamellar liquid crystal decreased when glycerol was used as solvent instead of water.
Measurements of ~2H NMR spectra and phase diagrams showed that the stability of SDS/C_(10)OH/solvents lamellar liquid crystal decreased when glycerol was used as solvent instead of water.
1992, 8(02): 243-246
doi: 10.3866/PKU.WHXB19920220
Abstract:
In this paper, we report the SERS of tetraphenyl porphyin (TPP) adsorbed on silver films prepared by homogeneous chemical reduction for the first time. We suggest that the adsorbed state of TPP on Ag surface is characterized as the por-phyin ring plane is laid on Ag surface paralleled, and the phenyl ring plane is inclined to Ag surface. In concideration of this adsorbed state and charge transfer theory, we assigned a part of the spectral peaks of certain vibrational model and explain the mechanism of TPP enhanced effect.
In this paper, we report the SERS of tetraphenyl porphyin (TPP) adsorbed on silver films prepared by homogeneous chemical reduction for the first time. We suggest that the adsorbed state of TPP on Ag surface is characterized as the por-phyin ring plane is laid on Ag surface paralleled, and the phenyl ring plane is inclined to Ag surface. In concideration of this adsorbed state and charge transfer theory, we assigned a part of the spectral peaks of certain vibrational model and explain the mechanism of TPP enhanced effect.
1992, 8(02): 247-250
doi: 10.3866/PKU.WHXB19920221
Abstract:
A series of rare earth aluminate oxides were prepared by nitrate decomposition. The catalysts obtained were characterized by XRD, CO_2 TPD and XPS techniques and their catalytic activities for methane coupling were measured, The experimental results showed that the basicity of the surface can be interpreted by the double ioni-zation energy of oxygen species on the surface. There exists some correlation between this parameter and their catalytic activities.
A series of rare earth aluminate oxides were prepared by nitrate decomposition. The catalysts obtained were characterized by XRD, CO_2 TPD and XPS techniques and their catalytic activities for methane coupling were measured, The experimental results showed that the basicity of the surface can be interpreted by the double ioni-zation energy of oxygen species on the surface. There exists some correlation between this parameter and their catalytic activities.
1992, 8(02): 251-254
doi: 10.3866/PKU.WHXB19920222
Abstract:
The crystals of complexes [M(H_2EDTA)H_2O] (M=Cu, Ni) are synthesized in aqueous solution. The electronic absorption spectra of these crystals are determined at room temperature. By using of the method of ligand radial wave function scaling theory of 3d orbit, the d-d transition spectra are explained quantitatively, and the d-electron transitions of the electronic absorption spectra are discussed.
The crystals of complexes [M(H_2EDTA)H_2O] (M=Cu, Ni) are synthesized in aqueous solution. The electronic absorption spectra of these crystals are determined at room temperature. By using of the method of ligand radial wave function scaling theory of 3d orbit, the d-d transition spectra are explained quantitatively, and the d-electron transitions of the electronic absorption spectra are discussed.
1992, 8(02): 255-260
doi: 10.3866/PKU.WHXB19920223
Abstract:
The algebraic formulas of 1.5 and 2.5 rank are given for four space groups P2_1, Pn, Pnα2_1, P2_12_12_1. It is better that the results of applying them to estimating general type of phases for four correspondent crystal structures. And a method of transforming algebraic formulas from 1(2) rank into 1.5(2.5) rank is proposed.
The algebraic formulas of 1.5 and 2.5 rank are given for four space groups P2_1, Pn, Pnα2_1, P2_12_12_1. It is better that the results of applying them to estimating general type of phases for four correspondent crystal structures. And a method of transforming algebraic formulas from 1(2) rank into 1.5(2.5) rank is proposed.
1992, 8(02): 261-265
doi: 10.3866/PKU.WHXB19920224
Abstract:
Raman spectrum was used to characterize the structure of Mo species supported on TiO_2-modified Al_2O_3. For Mo/Al_2O_3 without TiO_2 samples the bands at 325-350 cm~(-1) and 930-940 cm~(-1) assigned as tetrahedral MoO_4~(-2), and the bands at 215 and 950 cm~(-1) as octahedral MoO_6~(-6) can be observed at lower MoO_3 loading, while Al_2(MoO_4)_3 phase and crystalline MoO_3 appeared respectively at 370, 1004 cm~(-1) and 822, 991 cm~(-1) when the amount of MoO_3 was beyond one monolayer dispersion on Al_2O_3 surface. As for Mo/TiO_2-Al_2O_3 samples, only octahedral MoO_6~(-6) and crystalline MoO_3, but no tetrahedral MoO_4~(-2) and Al_2(MoO_4)_3 phases had been detected at low or high MoO_3 loadings, even calcination temperature of the samples raised to 973 K, which reveals that TiO_2 covered on Al_2O_3 can weaken the interaction between MoO_3 and Al_2O_3, and inhibits the formation of Al_2(MoO_4)_3 phase. When a definite amount of CoO added into molybdena samples the bands of crystalline MoO_3 disappeared, suggesting that CoO can effectively promote the dispersion of MoO_3 on the carrier. The presence of CoMoO_4 phase was observed in Al_2O_3 or TiO_2-Al_2O_3 carriers.
Raman spectrum was used to characterize the structure of Mo species supported on TiO_2-modified Al_2O_3. For Mo/Al_2O_3 without TiO_2 samples the bands at 325-350 cm~(-1) and 930-940 cm~(-1) assigned as tetrahedral MoO_4~(-2), and the bands at 215 and 950 cm~(-1) as octahedral MoO_6~(-6) can be observed at lower MoO_3 loading, while Al_2(MoO_4)_3 phase and crystalline MoO_3 appeared respectively at 370, 1004 cm~(-1) and 822, 991 cm~(-1) when the amount of MoO_3 was beyond one monolayer dispersion on Al_2O_3 surface. As for Mo/TiO_2-Al_2O_3 samples, only octahedral MoO_6~(-6) and crystalline MoO_3, but no tetrahedral MoO_4~(-2) and Al_2(MoO_4)_3 phases had been detected at low or high MoO_3 loadings, even calcination temperature of the samples raised to 973 K, which reveals that TiO_2 covered on Al_2O_3 can weaken the interaction between MoO_3 and Al_2O_3, and inhibits the formation of Al_2(MoO_4)_3 phase. When a definite amount of CoO added into molybdena samples the bands of crystalline MoO_3 disappeared, suggesting that CoO can effectively promote the dispersion of MoO_3 on the carrier. The presence of CoMoO_4 phase was observed in Al_2O_3 or TiO_2-Al_2O_3 carriers.
1992, 8(02): 266-269
doi: 10.3866/PKU.WHXB19920225
Abstract:
A micro-Raman electrochemical cell was designed for in-situ study of the elec-troreduction of SO_2Cl_2. This type of microcell has advantages of low sample volume, easy manipulation and experimental safety. Therefore, it can be used conveniently for in-situ spectroscopic investigation of strongly oxidative and hazardous Li-liquid cathode electrochemical systems.
A micro-Raman electrochemical cell was designed for in-situ study of the elec-troreduction of SO_2Cl_2. This type of microcell has advantages of low sample volume, easy manipulation and experimental safety. Therefore, it can be used conveniently for in-situ spectroscopic investigation of strongly oxidative and hazardous Li-liquid cathode electrochemical systems.
1992, 8(02): 270-273
doi: 10.3866/PKU.WHXB19920226
Abstract:
~(13)C and ~1H NMR technique was used to study the interaction of Gly-Gly with heavy lanthanide cations Dy~(3+), Ho~(3+), Er~(3+), Tm~(3+) and Yb~(3+) in aqueous solution. The stability constants for the 1:1 and 1:2 complexes of Gly-Gly with Ho~(3+) and Yb~(3+) were determined from the titration curves of chemical shift versus concentration ratio of lanthanide to Gly-Gly. The solution structure of the Ln-Gly-Gly complex was analyzed based upon the ~(13)C and ~1H lanthanide-induced shifts and the results show that in the complex Gly-Gly is coordinated to the lanthanide ion through the carboxyl oxygens with the backbone of the ligand in an extended state.
~(13)C and ~1H NMR technique was used to study the interaction of Gly-Gly with heavy lanthanide cations Dy~(3+), Ho~(3+), Er~(3+), Tm~(3+) and Yb~(3+) in aqueous solution. The stability constants for the 1:1 and 1:2 complexes of Gly-Gly with Ho~(3+) and Yb~(3+) were determined from the titration curves of chemical shift versus concentration ratio of lanthanide to Gly-Gly. The solution structure of the Ln-Gly-Gly complex was analyzed based upon the ~(13)C and ~1H lanthanide-induced shifts and the results show that in the complex Gly-Gly is coordinated to the lanthanide ion through the carboxyl oxygens with the backbone of the ligand in an extended state.
1992, 8(02): 274-278
doi: 10.3866/PKU.WHXB19920227
Abstract:
This paper reported an observation of the chemiluminescence in the 400～900 nm spectral region produced by the crossed molecular beam reaction of F(~2P) with CH_2Br_2, as well as the reaction mechanism. Under single collision condition, only vibrationally excited HF~≠(X,V) (V≤3) can be observed. In the case of multicollision, in addition to V≤3, HF~≠(X,V) with V>3 and electronically excited Br_2~*(B), BrF~*(B) have been detected. The equilibrium rotational temperature for HF(3,0) band is 320 K, and the relative population ratio of different V levels of HF is N_3:N_4:N_5=0.69:1.00:0.12.
This paper reported an observation of the chemiluminescence in the 400～900 nm spectral region produced by the crossed molecular beam reaction of F(~2P) with CH_2Br_2, as well as the reaction mechanism. Under single collision condition, only vibrationally excited HF~≠(X,V) (V≤3) can be observed. In the case of multicollision, in addition to V≤3, HF~≠(X,V) with V>3 and electronically excited Br_2~*(B), BrF~*(B) have been detected. The equilibrium rotational temperature for HF(3,0) band is 320 K, and the relative population ratio of different V levels of HF is N_3:N_4:N_5=0.69:1.00:0.12.
1992, 8(02): 279-287
doi: 10.3866/PKU.WHXB19920228
Abstract:
