Login In
2004 Volume 20 Issue 2
2004, 20(02): 113-117
doi: 10.3866/PKU.WHXB20040201
Abstract:
The mixed potential as a function of time was measured during the electroless copper plating on ceramic and copper substrates, and the induction process was determined successfully. The effects of the chelating agents, additives and pH value on the mixed potential－time curves were investigated. The results indicate that the mixed potential－time curves shift in negative direction and the induction time becomes longer with increasing concentration of the chelating agents or the additives in the solution. And higher pH values in the solution can shorten the induction time and make the potential－time curves more negative. The activation process can affect the induction time, higher activation temperature decreases the induction time greatly and increases the plating rate at the same time. It needs much longer induction time for plating copper on fresh-copper-activated copper substrate than that on the Pd-activated copper substrate. On the basis of these results, we furthermore explained the reason why non-noble-metal activation process is inferior to noble-metal activation process in electroless copper plaing.
The mixed potential as a function of time was measured during the electroless copper plating on ceramic and copper substrates, and the induction process was determined successfully. The effects of the chelating agents, additives and pH value on the mixed potential－time curves were investigated. The results indicate that the mixed potential－time curves shift in negative direction and the induction time becomes longer with increasing concentration of the chelating agents or the additives in the solution. And higher pH values in the solution can shorten the induction time and make the potential－time curves more negative. The activation process can affect the induction time, higher activation temperature decreases the induction time greatly and increases the plating rate at the same time. It needs much longer induction time for plating copper on fresh-copper-activated copper substrate than that on the Pd-activated copper substrate. On the basis of these results, we furthermore explained the reason why non-noble-metal activation process is inferior to noble-metal activation process in electroless copper plaing.
2004, 20(02): 118-122
doi: 10.3866/PKU.WHXB20040202
Abstract:
The equilibrium geometries and stabilities of (n=0,－1,－2,－3,－4) clusters are predicted by B3LYP/6-311G computations, at the same level, endo-and exo-icosahedral clusters (X@ B12H122－ and X B12H122－,X=H0/＋,Li0/＋,He,Ne,Be0/2＋,Na＋,Mg2＋) are discussed. It is found that the endo-icosahedral clusters (X@ B12H122－,X=Li＋,Be2＋,Mg2＋) are energetically favorable than the other exo-icosahedral clusters, and the exo-icosahedral clusters B12H122－(C3v) are more stable than that of B12H122－(C2v) structures, which are demonstrated by a transition state from IRC calculations.
The equilibrium geometries and stabilities of (n=0,－1,－2,－3,－4) clusters are predicted by B3LYP/6-311G computations, at the same level, endo-and exo-icosahedral clusters (X@ B12H122－ and X B12H122－,X=H0/＋,Li0/＋,He,Ne,Be0/2＋,Na＋,Mg2＋) are discussed. It is found that the endo-icosahedral clusters (X@ B12H122－,X=Li＋,Be2＋,Mg2＋) are energetically favorable than the other exo-icosahedral clusters, and the exo-icosahedral clusters B12H122－(C3v) are more stable than that of B12H122－(C2v) structures, which are demonstrated by a transition state from IRC calculations.
2004, 20(02): 123-128
doi: 10.3866/PKU.WHXB20040203
Abstract:
In order to examine possible relationship between freezing properties and the number of hydroxyl group in solute molecules, a differential scanning calorimeter(Pyris-Diamond DSC)was employed to study the thermal behaviors(supercooling degree of heterogeneous nucleating temperature, hydration properties, glass transition and devitrification) of ethylene glycol and glycerol aqueous solutions. Experiments were conducted on 12 groups (24 in total) aqueous solutions with different concentrations. At the same concentrations (mass fraction, w), the supercooling behaviors of these two polyols aqueous solutions followed similar rules of change. At concentration of 0～5％(w), supercooling degrees decreased first and then increased with increasing concentration. But at concentration of 5％～25％(w), experimental results showed that supercooling behaviors became disorder. At concentrations >25％, supercooling degrees enhanced monotonically with the increasing solutes contents. Hydration experiments showed that the unfreezable water content in aqueous solutions of these two polyols solutions had no significant difference(ratios of unfreezable water contents are 1.04～1.15 ) with the same mass percentage. However, the temperature of glass transition and devitrification exhibited distinct difference. It can be concluded that “hydroxyl-group concentration” of this two polyols aqueous solutions could predict supercooling behaviors and hydration capabilities. Neither mass percentage nor molality of these two polyols solutions could characterize glass transition and devitrification temperature.
In order to examine possible relationship between freezing properties and the number of hydroxyl group in solute molecules, a differential scanning calorimeter(Pyris-Diamond DSC)was employed to study the thermal behaviors(supercooling degree of heterogeneous nucleating temperature, hydration properties, glass transition and devitrification) of ethylene glycol and glycerol aqueous solutions. Experiments were conducted on 12 groups (24 in total) aqueous solutions with different concentrations. At the same concentrations (mass fraction, w), the supercooling behaviors of these two polyols aqueous solutions followed similar rules of change. At concentration of 0～5％(w), supercooling degrees decreased first and then increased with increasing concentration. But at concentration of 5％～25％(w), experimental results showed that supercooling behaviors became disorder. At concentrations >25％, supercooling degrees enhanced monotonically with the increasing solutes contents. Hydration experiments showed that the unfreezable water content in aqueous solutions of these two polyols solutions had no significant difference(ratios of unfreezable water contents are 1.04～1.15 ) with the same mass percentage. However, the temperature of glass transition and devitrification exhibited distinct difference. It can be concluded that “hydroxyl-group concentration” of this two polyols aqueous solutions could predict supercooling behaviors and hydration capabilities. Neither mass percentage nor molality of these two polyols solutions could characterize glass transition and devitrification temperature.
2004, 20(02): 129-133
doi: 10.3866/PKU.WHXB20040204
Abstract:
A series of nanostructured films exhibiting high surface roughness were prepared by using square wave oxidation-reduction cycles (SWORC) on Pt microelectrodes. Scanning tunneling microscope (STM) studies illustrated that all the films were made up of Pt islands. Measurement showed that along with the increase of average thickness of nanostructured films from 58 to 139 nm, the average dimension of Pt islands in the film increased solely from 102 to 114 nm, and the average height of Pt islands varied from 15 to 18 nm.Employing CO adsorption as molecule-probe reaction, IR properties of the prepared nanostructured Pt films of different roughness were investigated by using in situ FTIR spectroscopy. The results revealed that CO linearly adsorbed (COL) on all nanostructured Pt films prepared in this paper yielded Fano-like spectra, i.e., the IR absorption of COL on nanostructured Pt film gave rise to a bipolar IR band (asymmetric line shape), which may be attributed primarily to the size effect of Pt islands.
A series of nanostructured films exhibiting high surface roughness were prepared by using square wave oxidation-reduction cycles (SWORC) on Pt microelectrodes. Scanning tunneling microscope (STM) studies illustrated that all the films were made up of Pt islands. Measurement showed that along with the increase of average thickness of nanostructured films from 58 to 139 nm, the average dimension of Pt islands in the film increased solely from 102 to 114 nm, and the average height of Pt islands varied from 15 to 18 nm.Employing CO adsorption as molecule-probe reaction, IR properties of the prepared nanostructured Pt films of different roughness were investigated by using in situ FTIR spectroscopy. The results revealed that CO linearly adsorbed (COL) on all nanostructured Pt films prepared in this paper yielded Fano-like spectra, i.e., the IR absorption of COL on nanostructured Pt film gave rise to a bipolar IR band (asymmetric line shape), which may be attributed primarily to the size effect of Pt islands.
2004, 20(02): 134-137
doi: 10.3866/PKU.WHXB20040205
Abstract:
The classical trajectory calculation by Venus 95 and based on 48 extended London-Eying-Polanyi-Sato(LEPS) potential energy surfaces(PES) which have different topological-structure are carried out to study the dependence of the rotational alignment on the properties of PES and the reaction dynamic conditions. 58 samples are obtained. The dependence is studied by multi-factors nonlinear analysis based on these samples. By pattern recognition, the key factors are the mass of reagent, the width of exit of PES and the relative collision energy. We also found that the cross interaction between different factors have very important effect.
The classical trajectory calculation by Venus 95 and based on 48 extended London-Eying-Polanyi-Sato(LEPS) potential energy surfaces(PES) which have different topological-structure are carried out to study the dependence of the rotational alignment on the properties of PES and the reaction dynamic conditions. 58 samples are obtained. The dependence is studied by multi-factors nonlinear analysis based on these samples. By pattern recognition, the key factors are the mass of reagent, the width of exit of PES and the relative collision energy. We also found that the cross interaction between different factors have very important effect.
2004, 20(02): 138-143
doi: 10.3866/PKU.WHXB20040206
Abstract:
A set of nanometer TiO2 photocatalysts doped with various ions of transition metals (Cr、Mn、Fe、Co、Ni、and Cu) was prepared by using the wet impregnation method. The samples were characterized by using some bulk and surface techniques namely X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The samples were employed as catalysts for acetic acid photocatalytic oxidation degradation and carbon dioxide photocatalytic reduction in aqueous suspension, used as probe reactions. The characterization results have confirmed that the doping ions exist on the surface in the form of oxide and have no significant effect on crystal phase of the samples. Photocatalytic activities of the doped samples were improved in the order of Cr、Co、Ni、Fe、Mn、Cu. The photocatalytic activity of doped TiO2 appears to be a complex function of the dopant concentration, adsorption oxygen and the nature of doped ions.
A set of nanometer TiO2 photocatalysts doped with various ions of transition metals (Cr、Mn、Fe、Co、Ni、and Cu) was prepared by using the wet impregnation method. The samples were characterized by using some bulk and surface techniques namely X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The samples were employed as catalysts for acetic acid photocatalytic oxidation degradation and carbon dioxide photocatalytic reduction in aqueous suspension, used as probe reactions. The characterization results have confirmed that the doping ions exist on the surface in the form of oxide and have no significant effect on crystal phase of the samples. Photocatalytic activities of the doped samples were improved in the order of Cr、Co、Ni、Fe、Mn、Cu. The photocatalytic activity of doped TiO2 appears to be a complex function of the dopant concentration, adsorption oxygen and the nature of doped ions.
2004, 20(02): 144-148
doi: 10.3866/PKU.WHXB20040207
Abstract:
On the basis of 5-MP semiempirical method used to deal with the interaction between atoms and metal surfaces, an extended LEPS potential between CO and Pt surface has been constructed. The adsorption mechanism of CO on three Pt low-index surfaces was investigated by the extended LEPS potential. We reproduce well the experimental data of the adsorption sites, the adsorption geometry, the binding energy and the eigenvibration for CO on Pt surfaces. We also evaluate some unreasonable experimental data in the literatures and predict the following important information that has not been observed: on Pt (100),an 1 962.60 cm－1 frequency in fourfold hollow site; and on Pt (110),the C－O and Pt－C distances as 115.1,147 pm, respectively have been predicted.
On the basis of 5-MP semiempirical method used to deal with the interaction between atoms and metal surfaces, an extended LEPS potential between CO and Pt surface has been constructed. The adsorption mechanism of CO on three Pt low-index surfaces was investigated by the extended LEPS potential. We reproduce well the experimental data of the adsorption sites, the adsorption geometry, the binding energy and the eigenvibration for CO on Pt surfaces. We also evaluate some unreasonable experimental data in the literatures and predict the following important information that has not been observed: on Pt (100),an 1 962.60 cm－1 frequency in fourfold hollow site; and on Pt (110),the C－O and Pt－C distances as 115.1,147 pm, respectively have been predicted.
2004, 20(02): 149-153
doi: 10.3866/PKU.WHXB20040208
Abstract:
Organic-inorganic hybrid mesoporous molecular sieve MCM-41 was synthesized by co-condensation of tetraethoxysilane (TEOS) and 3-chlorpropyl-triethoxysilane, then reacted with (1R,2R)-1,2-diaminocyclohexane and dichloro(p-cymene)-ruthenium dimer successively to afford immobilized asymmetric hydrogen transfer catalyst. The prepared catalyst was characterized by means of FT-IR, PXRD and N2 adsorption-desorption isotherms,and was applied in asymmetric hydrogen transfer reactions of reduction of acetophenone to α-phenyl ethanol. It showed an average conversion of 6.42％ and ee (enantiomeric excess) value of 12.64％ in all 3 performances. The conversion was a little higher than its corresponding homogenous counterpart (conversion of 3.56％ and ee value of 33.04％), while the ee values were somewhat lower.
Organic-inorganic hybrid mesoporous molecular sieve MCM-41 was synthesized by co-condensation of tetraethoxysilane (TEOS) and 3-chlorpropyl-triethoxysilane, then reacted with (1R,2R)-1,2-diaminocyclohexane and dichloro(p-cymene)-ruthenium dimer successively to afford immobilized asymmetric hydrogen transfer catalyst. The prepared catalyst was characterized by means of FT-IR, PXRD and N2 adsorption-desorption isotherms,and was applied in asymmetric hydrogen transfer reactions of reduction of acetophenone to α-phenyl ethanol. It showed an average conversion of 6.42％ and ee (enantiomeric excess) value of 12.64％ in all 3 performances. The conversion was a little higher than its corresponding homogenous counterpart (conversion of 3.56％ and ee value of 33.04％), while the ee values were somewhat lower.
2004, 20(02): 154-157
doi: 10.3866/PKU.WHXB20040209
Abstract:
The resonant two-photons ionization technique is employed to study jet-cooled van der Waals (vdW) complex C6H5CH3…N2 through the S1←S0 transition. By Comparing the spectra of isotopic complex C6D5CD3…N2, we have tentatively assigned all the observed spectral features to the complex C6H5CH3…N2. The rich information about the complex intermolecular vdW viberational modes and internal rotation of N2 are obtained by the spectra. The binding energies for the complex C6H5CH3…N2 in the excited electronic state and in the ground electronic state are about 494 cm－1 and 474 cm－1, those are very close to the calculated values.
The resonant two-photons ionization technique is employed to study jet-cooled van der Waals (vdW) complex C6H5CH3…N2 through the S1←S0 transition. By Comparing the spectra of isotopic complex C6D5CD3…N2, we have tentatively assigned all the observed spectral features to the complex C6H5CH3…N2. The rich information about the complex intermolecular vdW viberational modes and internal rotation of N2 are obtained by the spectra. The binding energies for the complex C6H5CH3…N2 in the excited electronic state and in the ground electronic state are about 494 cm－1 and 474 cm－1, those are very close to the calculated values.
2004, 20(02): 158-163
doi: 10.3866/PKU.WHXB20040210
Abstract:
Dielectric measurement was carried out on D354 anion-exchange beads dispersed in KCl solutions with different concentrations. Distinct dielectric relaxations were observed in the frequency between 106 Hz and 107 Hz, and particular relations between permittivity, electric conductivity, relaxation time and the solution concentration were obtained. It was proved that such a relaxation is a non-single mechanism relaxation that due mainly to interfacial polarization, then the particular dielectric behavior was interpreted by the theory of Maxwell-Wagner and properties of electrical double layer, and the information of ion transformation and accumulation at the interface between the particles and solution phase in the presence of an external AC (alternative current) field was obtained. It is conclude that, the electric double layer that formed during the static ionic equilibrium would not be destroyed by added AC field; the enrichment of counterions in electric double layer predicts dielectric increment, while the thickness of electric double layer decides the magnitude of the relaxation frequency; and the ionic strength in electric double layer was fond corresponding to the ionic strength of pure KCl solution with a concentration of 0.7 mmol•L－1.
Dielectric measurement was carried out on D354 anion-exchange beads dispersed in KCl solutions with different concentrations. Distinct dielectric relaxations were observed in the frequency between 106 Hz and 107 Hz, and particular relations between permittivity, electric conductivity, relaxation time and the solution concentration were obtained. It was proved that such a relaxation is a non-single mechanism relaxation that due mainly to interfacial polarization, then the particular dielectric behavior was interpreted by the theory of Maxwell-Wagner and properties of electrical double layer, and the information of ion transformation and accumulation at the interface between the particles and solution phase in the presence of an external AC (alternative current) field was obtained. It is conclude that, the electric double layer that formed during the static ionic equilibrium would not be destroyed by added AC field; the enrichment of counterions in electric double layer predicts dielectric increment, while the thickness of electric double layer decides the magnitude of the relaxation frequency; and the ionic strength in electric double layer was fond corresponding to the ionic strength of pure KCl solution with a concentration of 0.7 mmol•L－1.
2004, 20(02): 164-168
doi: 10.3866/PKU.WHXB20040211
Abstract:
Nanometer-sized BaTiO3 crystallites in different sizes have been prepared by sol-gel method. The crystal structure, phase transition and Raman spectra of the BaTiO3 crystallites were investigated by XRD, Raman spectra and DSC. The results indicated that BaTiO3 crystallite forms at temperature of 750 ℃. The average grain size is about 38 nm and the crystal structure belongs to the cubic paraelectric phase. With the increase of annealing temperature, the grain becomes larger and a axis becomes shorter while c axis becomes longer gradually. The crystal structure begins to change to the cubic paraelectric phase from the tetra nal phase at about 54 nm of average grain. The crystal structure of BaTiO3 crystallite with an average grain size of about 102 nm belongs to tetra nal phase. During the decrease of average grain size, the temperature of phase transition from orthodoxy to tetra nal increases while the temperature of phase transition from tetra nal to cubic decreases. There exists heat stagnation in phase transition and the heat stagnation decreases gradually with the decreasing grain size. The frequencies of Raman bands strongly depend on grain sizes and structures of the BaTiO3 crystallite. The characteristic peaks of tetra nal phase disappear at about 38 nm of average grain.
Nanometer-sized BaTiO3 crystallites in different sizes have been prepared by sol-gel method. The crystal structure, phase transition and Raman spectra of the BaTiO3 crystallites were investigated by XRD, Raman spectra and DSC. The results indicated that BaTiO3 crystallite forms at temperature of 750 ℃. The average grain size is about 38 nm and the crystal structure belongs to the cubic paraelectric phase. With the increase of annealing temperature, the grain becomes larger and a axis becomes shorter while c axis becomes longer gradually. The crystal structure begins to change to the cubic paraelectric phase from the tetra nal phase at about 54 nm of average grain. The crystal structure of BaTiO3 crystallite with an average grain size of about 102 nm belongs to tetra nal phase. During the decrease of average grain size, the temperature of phase transition from orthodoxy to tetra nal increases while the temperature of phase transition from tetra nal to cubic decreases. There exists heat stagnation in phase transition and the heat stagnation decreases gradually with the decreasing grain size. The frequencies of Raman bands strongly depend on grain sizes and structures of the BaTiO3 crystallite. The characteristic peaks of tetra nal phase disappear at about 38 nm of average grain.
2004, 20(02): 169-172
doi: 10.3866/PKU.WHXB20040212
Abstract:
Crystallization of calcium oxalate (CaC2O4) was comparatively investigated in five gel systems in the absence and presence of potassium citrate (K3cit).The five gelatinous systems include water, sodium chloride, synthesized urine, diluted healthy urine and diluted pathological urine, respectively. In the absence of K3cit, calcium oxalate monohydrate (COM) is the dominant phase. However, calcium oxalate dihydrate (COD) and trihydrate (COT) crystals appeared simultaneously in the gel systems containing sodium chloride or synthesized urine. COD appeared also in the diluted pathological urine, whereas there was not any COD or COT crystals in the diluted healthy urine system. In the presence of K3cit, the percentage of COT increased markedly in the gel systems containing either water, sodium chloride or synthesized urine. A great deal of COD appeared in the diluted pathological urine system, and a few COD and COT appeared in the diluted healthy urine system. The lower temperature, higher ionic strength and the presence of metal ions in the gel systems lead to increase of the percentage of COT crystals. K3cit has the ability to induce the formation of COD and COT, as well as to diminish the sectional area of COM crystals, thus K3cit can prevent and cure calcium oxalate calculi.
Crystallization of calcium oxalate (CaC2O4) was comparatively investigated in five gel systems in the absence and presence of potassium citrate (K3cit).The five gelatinous systems include water, sodium chloride, synthesized urine, diluted healthy urine and diluted pathological urine, respectively. In the absence of K3cit, calcium oxalate monohydrate (COM) is the dominant phase. However, calcium oxalate dihydrate (COD) and trihydrate (COT) crystals appeared simultaneously in the gel systems containing sodium chloride or synthesized urine. COD appeared also in the diluted pathological urine, whereas there was not any COD or COT crystals in the diluted healthy urine system. In the presence of K3cit, the percentage of COT increased markedly in the gel systems containing either water, sodium chloride or synthesized urine. A great deal of COD appeared in the diluted pathological urine system, and a few COD and COT appeared in the diluted healthy urine system. The lower temperature, higher ionic strength and the presence of metal ions in the gel systems lead to increase of the percentage of COT crystals. K3cit has the ability to induce the formation of COD and COT, as well as to diminish the sectional area of COM crystals, thus K3cit can prevent and cure calcium oxalate calculi.
2004, 20(02): 173-177
doi: 10.3866/PKU.WHXB20040213
Abstract:
Three cross-photodimers were synthesized by irradiation of each two monomers of 4-(2-phenylethenyl)pyridine, 2-(2-phenylethenyl)benzoxazole and 5-phenyl-2-(2-phenylethenyl) oxazole in H2SO4 solution using medium-pressure Mercury lamp (λ > 300 nm) as light source.The cross-photodimerization was monitored by HPLC titration. The results showed that three photodimers were produced in each reaction,two of them were the self-photodimers and the other one was the cross-photodimer. The cross-photodimers were isolated by column chromatography and their structures with syn-head-to-tail configurations were determined by UV, IR, 1H NMR, 13C NMR and MS. The photolysis of the cross-photodimer was performed in dilute methanol solution upon the irradiation of low-pressure Mercury lamp (λ=254 nm) and monitored by HPLC and UV titration. It was found that the cross-photodimer was photolyzed into trans-monomers at first, and then the new-formed trans-monomers were converted into cis-ones by the trans-cis isomerization.
Three cross-photodimers were synthesized by irradiation of each two monomers of 4-(2-phenylethenyl)pyridine, 2-(2-phenylethenyl)benzoxazole and 5-phenyl-2-(2-phenylethenyl) oxazole in H2SO4 solution using medium-pressure Mercury lamp (λ > 300 nm) as light source.The cross-photodimerization was monitored by HPLC titration. The results showed that three photodimers were produced in each reaction,two of them were the self-photodimers and the other one was the cross-photodimer. The cross-photodimers were isolated by column chromatography and their structures with syn-head-to-tail configurations were determined by UV, IR, 1H NMR, 13C NMR and MS. The photolysis of the cross-photodimer was performed in dilute methanol solution upon the irradiation of low-pressure Mercury lamp (λ=254 nm) and monitored by HPLC and UV titration. It was found that the cross-photodimer was photolyzed into trans-monomers at first, and then the new-formed trans-monomers were converted into cis-ones by the trans-cis isomerization.
2004, 20(02): 178-181
doi: 10.3866/PKU.WHXB20040214
Abstract:
Monodisperse polystyrene(PS) microcapsules containing vitamin E(VE)were prepared by membrane emulsification-dying in liquid technique. The diameter of microcapsules was about 4 times the size of the pore diameter of Shirasu porous glass (SPG) membrane, and the coefficient of variation (CV) of the microcapsule size was less than 0.2, showing a od monodispersity. Furthermore, the effects of the ratio of PS to VE (m/m) and the diameter of microcapsules on the release characteristics were investigated. When the ratio of PS to VE (m/m) is 40/1, the permeability coefficients were 0.71×10－9 and 0.74×10－9 m•s－1 corresponding to the microcapsule diameters of 21.32 and 11.45 μm, and the concentrations of VE released were 8 and 12 mg•L－1 respectively, which conform to the optimal concentration in applications.
Monodisperse polystyrene(PS) microcapsules containing vitamin E(VE)were prepared by membrane emulsification-dying in liquid technique. The diameter of microcapsules was about 4 times the size of the pore diameter of Shirasu porous glass (SPG) membrane, and the coefficient of variation (CV) of the microcapsule size was less than 0.2, showing a od monodispersity. Furthermore, the effects of the ratio of PS to VE (m/m) and the diameter of microcapsules on the release characteristics were investigated. When the ratio of PS to VE (m/m) is 40/1, the permeability coefficients were 0.71×10－9 and 0.74×10－9 m•s－1 corresponding to the microcapsule diameters of 21.32 and 11.45 μm, and the concentrations of VE released were 8 and 12 mg•L－1 respectively, which conform to the optimal concentration in applications.
2004, 20(02): 182-185
doi: 10.3866/PKU.WHXB20040215
Abstract:
The nanocrystalline TiO2-Pt modified titanium (Ti/nano-TiO2-Pt) electrode was prepared by electrosynthesis and direct hydrolysis and electrodeposited Pt on nanocrystalline TiO2 film. SEM was used to characterize the structure of Ti/nano-TiO2-Pt (Pt micro particle 60 nm). Redox behaviors of the Ti/nano-TiO2-Pt electrode, as well as the electrocatalytic activity of the Ti/nano-TiO2-Pt electrode for Mn2＋ oxydized to Mn3＋ were investigated by cyclic voltammetry and bulk electrolysis. The results indicated that there was high electrocatalytic activity of the Ti/nano-TiO2-Pt electrode for Mn2＋ oxydized to Mn3＋; The electrocatalytic activity of the Ti/nano-TiO2-Pt electrode was higher than Pt electrode. In preparative electrolysis under heterogeneous optimal conditions, average current efficiency for Mn3＋ was 86％.
The nanocrystalline TiO2-Pt modified titanium (Ti/nano-TiO2-Pt) electrode was prepared by electrosynthesis and direct hydrolysis and electrodeposited Pt on nanocrystalline TiO2 film. SEM was used to characterize the structure of Ti/nano-TiO2-Pt (Pt micro particle 60 nm). Redox behaviors of the Ti/nano-TiO2-Pt electrode, as well as the electrocatalytic activity of the Ti/nano-TiO2-Pt electrode for Mn2＋ oxydized to Mn3＋ were investigated by cyclic voltammetry and bulk electrolysis. The results indicated that there was high electrocatalytic activity of the Ti/nano-TiO2-Pt electrode for Mn2＋ oxydized to Mn3＋; The electrocatalytic activity of the Ti/nano-TiO2-Pt electrode was higher than Pt electrode. In preparative electrolysis under heterogeneous optimal conditions, average current efficiency for Mn3＋ was 86％.
2004, 20(02): 186-190
doi: 10.3866/PKU.WHXB20040216
Abstract:
The thermodynamic properties of HCl-NiSO4-H2O system was studied by EMF measurement in the cells without liquid junction: Pt, H2(101.325 kPa)│HCl(mA), NiSO4(mB), H2O│AgCl-Ag at certain total ionic strength I =0.4、0.6、0.8、1.0、1.5、2.0 mol•kg－1 with various ionic strength fractions of NiSO4 yB=0.00、0.10、0.20、0.30、0.50、0.70 at different temperatures from 278.15～323.15 K .The activity coefficients of HCl γA in the solution have been calculated from EMF of cell (A).The results show that the activity coefficients of HCl in the solutions still obey Harned’s rule.
The thermodynamic properties of HCl-NiSO4-H2O system was studied by EMF measurement in the cells without liquid junction: Pt, H2(101.325 kPa)│HCl(mA), NiSO4(mB), H2O│AgCl-Ag at certain total ionic strength I =0.4、0.6、0.8、1.0、1.5、2.0 mol•kg－1 with various ionic strength fractions of NiSO4 yB=0.00、0.10、0.20、0.30、0.50、0.70 at different temperatures from 278.15～323.15 K .The activity coefficients of HCl γA in the solution have been calculated from EMF of cell (A).The results show that the activity coefficients of HCl in the solutions still obey Harned’s rule.
2004, 20(02): 191-193
doi: 10.3866/PKU.WHXB20040217
Abstract:
Using chemical vapour deposition(CVD) method to decompose alcohol at high-temperature with zeolite(synthetic satonite)-based Fe particles as catalyst, authors synthesize carbon nanotubes (CNTs) of thinner walls and opened ends. Compared with the CNTs synthesized in other methods, CNTs synthesized by the author are straighter and have bigger inside diameter and fewer defects when the experimental parameters are controlled stably. CNTs of these structures have better performance in hydrogen-storage, and have greater potential applications.
Using chemical vapour deposition(CVD) method to decompose alcohol at high-temperature with zeolite(synthetic satonite)-based Fe particles as catalyst, authors synthesize carbon nanotubes (CNTs) of thinner walls and opened ends. Compared with the CNTs synthesized in other methods, CNTs synthesized by the author are straighter and have bigger inside diameter and fewer defects when the experimental parameters are controlled stably. CNTs of these structures have better performance in hydrogen-storage, and have greater potential applications.
2004, 20(02): 194-198
doi: 10.3866/PKU.WHXB20040218
Abstract:
Oil film life, rate of oil film thinning, water-oil interfacial properties and their effects on demulsification of model petroleum emulsions(O/W) in the presence of demulsifiers are studied. The results indicate that the interfacial elasticity decreased with the addition of demulsifiers, resulting a decrease of both the strength and the thickness of the oil film, and hence leading to a shorter film life. The film will break down when the film thickness reaches to a critical value by film thinning .For the demulsifiers in the same series, the interfacial elasticity of the film lowered with increasing demulsifier concentration initially, and then kept constant after the concentration reached a definite value. For the demulsifiers in different series, the more the interfacial elasticity lowered, the better the dewatering effect will be. The dewatering rate is correlated with the interfacial elasticity. An action mechanism of the demulsifiers was proposed according to the experimental results.
Oil film life, rate of oil film thinning, water-oil interfacial properties and their effects on demulsification of model petroleum emulsions(O/W) in the presence of demulsifiers are studied. The results indicate that the interfacial elasticity decreased with the addition of demulsifiers, resulting a decrease of both the strength and the thickness of the oil film, and hence leading to a shorter film life. The film will break down when the film thickness reaches to a critical value by film thinning .For the demulsifiers in the same series, the interfacial elasticity of the film lowered with increasing demulsifier concentration initially, and then kept constant after the concentration reached a definite value. For the demulsifiers in different series, the more the interfacial elasticity lowered, the better the dewatering effect will be. The dewatering rate is correlated with the interfacial elasticity. An action mechanism of the demulsifiers was proposed according to the experimental results.
2004, 20(02): 199-201
doi: 10.3866/PKU.WHXB20040219
Abstract:
With the increase of the anodizing time, the nanoporous morphology of the anodic porous alumina film formed by anodizing Al in an oxalic acid solution will change from irregular to regular and the distribution of nanoporous will also change from disarray to regular hexangular array. The results indicated that there was high internal stress in the barrier layer due to the severe mismatch between the barrier layer formed in early anodization and the Al substrate. The release of the internal stress resulted in the origination of the numerous nanoporous in the surface of the barrier layer, which accordingly made the surface energy of oxide film increase quickly. The internal stress in the walls and the surface tension in the surface of nanoporous acted together in the anodization and determined the morphology and distribution of the nanoporous in each phase of the anodization. When these two forces reached a balance, the nanoporous possessed excellent uniformity in diameter and spacing of the holes. At this time, the energy of the system is at the lowest. The transition process from unbalance to balance of the these two forces is the internal drive in the selforganized process of the porous configuration from the initial irregular through to regular array.
With the increase of the anodizing time, the nanoporous morphology of the anodic porous alumina film formed by anodizing Al in an oxalic acid solution will change from irregular to regular and the distribution of nanoporous will also change from disarray to regular hexangular array. The results indicated that there was high internal stress in the barrier layer due to the severe mismatch between the barrier layer formed in early anodization and the Al substrate. The release of the internal stress resulted in the origination of the numerous nanoporous in the surface of the barrier layer, which accordingly made the surface energy of oxide film increase quickly. The internal stress in the walls and the surface tension in the surface of nanoporous acted together in the anodization and determined the morphology and distribution of the nanoporous in each phase of the anodization. When these two forces reached a balance, the nanoporous possessed excellent uniformity in diameter and spacing of the holes. At this time, the energy of the system is at the lowest. The transition process from unbalance to balance of the these two forces is the internal drive in the selforganized process of the porous configuration from the initial irregular through to regular array.
2004, 20(02): 202-206
doi: 10.3866/PKU.WHXB20040220
Abstract:
The present study describes the application of capillary zone electrophoresis(CZE) to investigate the interaction between bovine serum albumin and gatifloxacin, the simplified method of Hummel-Dreyer was applied and the experimental condition was established after a large number of tests. Based on the site-binding model, practical formula for small ligand molecule to bio-macromolecule has been proposed; the binding parameters were measured according to suggested model by non-linear fitting program.
The present study describes the application of capillary zone electrophoresis(CZE) to investigate the interaction between bovine serum albumin and gatifloxacin, the simplified method of Hummel-Dreyer was applied and the experimental condition was established after a large number of tests. Based on the site-binding model, practical formula for small ligand molecule to bio-macromolecule has been proposed; the binding parameters were measured according to suggested model by non-linear fitting program.
2004, 20(02): 207-210
doi: 10.3866/PKU.WHXB20040221
Abstract:
Electrochemical quartz crystal microbalance and cyclic voltammetry were employed for studying the formation mechanism and electrochemical properties of the self-assembled membrane formed on the surface of the ld electrode. Experimental results show that specific interaction exists between L-cysteine and the ld electrode surface, additionally, the L-cysteine molecular pairs were formed due to the existence of electrostatic attraction and hydrogen bond between themselves in the solution with the pH around isoelectric point. Consequently, an L-cysteine self-assembled bilayer could be formed on the ld electrode surface. A pair of stable redox peaks were observed with the self-assembled bilayer modified ld electrode when potential scanning in 0.2 mol•L－1 Hac-NaAc buffer solution in the range of －0.2～0.5 V (vs SCE). It was also found that the modified electrode has an obvious electrocatalytic effect on the electrooxidation of ascorbic acid.
Electrochemical quartz crystal microbalance and cyclic voltammetry were employed for studying the formation mechanism and electrochemical properties of the self-assembled membrane formed on the surface of the ld electrode. Experimental results show that specific interaction exists between L-cysteine and the ld electrode surface, additionally, the L-cysteine molecular pairs were formed due to the existence of electrostatic attraction and hydrogen bond between themselves in the solution with the pH around isoelectric point. Consequently, an L-cysteine self-assembled bilayer could be formed on the ld electrode surface. A pair of stable redox peaks were observed with the self-assembled bilayer modified ld electrode when potential scanning in 0.2 mol•L－1 Hac-NaAc buffer solution in the range of －0.2～0.5 V (vs SCE). It was also found that the modified electrode has an obvious electrocatalytic effect on the electrooxidation of ascorbic acid.
2004, 20(02): 211-215
doi: 10.3866/PKU.WHXB20040222
Abstract:
This paper reports a method for the preparation of monodispersed ld colloid by seeding growth, with elimination of the nonspherical by-products, which were often observed and difficult to separate in previous works. The formation of nonspherical particles was found to be closely associated with the experimental conditions, such as, molar ratios and addition sequence of the reagents. The larger the [NH2OH]:[HAuCl4] ratio, the less and smaller the nonspherical particles. In addition, the effect of addition sequence can be ascribed to that of [NH2OH]:[HAuCl4] ratio, since different addition sequences make different instantaneous [NH2OH]:[HAuCl4] ratios during the addition and thus lead to different shape distribution of particles. Based on these findings, a method is adopted to rule out the nonspherical particles, by using high ratios of [NH2OH] to [HAuCl4] (the [NH2OH]:[HAuCl4] ratio being kept in the range of 10～30) and favorable addition sequence (NH2OH being added to seeds prior to HAuCl4). No nonspherical nanoparticles can be observed, and the resulted ld colloid shows od monodispersity and excellent size-controllability.
This paper reports a method for the preparation of monodispersed ld colloid by seeding growth, with elimination of the nonspherical by-products, which were often observed and difficult to separate in previous works. The formation of nonspherical particles was found to be closely associated with the experimental conditions, such as, molar ratios and addition sequence of the reagents. The larger the [NH2OH]:[HAuCl4] ratio, the less and smaller the nonspherical particles. In addition, the effect of addition sequence can be ascribed to that of [NH2OH]:[HAuCl4] ratio, since different addition sequences make different instantaneous [NH2OH]:[HAuCl4] ratios during the addition and thus lead to different shape distribution of particles. Based on these findings, a method is adopted to rule out the nonspherical particles, by using high ratios of [NH2OH] to [HAuCl4] (the [NH2OH]:[HAuCl4] ratio being kept in the range of 10～30) and favorable addition sequence (NH2OH being added to seeds prior to HAuCl4). No nonspherical nanoparticles can be observed, and the resulted ld colloid shows od monodispersity and excellent size-controllability.
2004, 20(02): 216-220
doi: 10.3866/PKU.WHXB20040223
Abstract:
The multilayer films of horseradish peroxidase (HRP) were fabricated by layer-by-layer assembly of HRP and concanavalin A (Con A) through lectin-glycogen reaction. The surface topography and roughness were characterized by AFM. The thickness of the films was studied by AFM and ellipsometry. The thicknesses of the Con A and the HRP film are about 9.0 and 4.6 nm, respectively, which correspond to their X-ray diffraction data. It is demonstrated that the shape of Con A and HRP molecule was well retained during the assembly process. Cyclic voltammetry (CV) was used to test the electrochemical properties of the films. The enzyme electrode of three bilayers of （Con A/HRP） films was sensitive for the reduction of hydrogen peroxide in the methylene blue (MB) solution. The response current is proportional to the concentration of H2O2 within the range of 0.2～1.0 mmol•L－1. The sensitivity of the enzyme electrode is 24.0 mA•mol－1 •L and the apparent Michaelis constant is 4.2 mmol•L－1.
The multilayer films of horseradish peroxidase (HRP) were fabricated by layer-by-layer assembly of HRP and concanavalin A (Con A) through lectin-glycogen reaction. The surface topography and roughness were characterized by AFM. The thickness of the films was studied by AFM and ellipsometry. The thicknesses of the Con A and the HRP film are about 9.0 and 4.6 nm, respectively, which correspond to their X-ray diffraction data. It is demonstrated that the shape of Con A and HRP molecule was well retained during the assembly process. Cyclic voltammetry (CV) was used to test the electrochemical properties of the films. The enzyme electrode of three bilayers of （Con A/HRP） films was sensitive for the reduction of hydrogen peroxide in the methylene blue (MB) solution. The response current is proportional to the concentration of H2O2 within the range of 0.2～1.0 mmol•L－1. The sensitivity of the enzyme electrode is 24.0 mA•mol－1 •L and the apparent Michaelis constant is 4.2 mmol•L－1.
2004, 20(02): 221-224
doi: 10.3866/PKU.WHXB20040224
Abstract:
Nanorods of lead chromate and barium chromate were synthesized by using artificial active membrane of celloidin as template and the cooperating effect of artificial active membrane with ethylenediamine. The results indicated that the diameter of lead chromate nanorods is between 28～55 nm and the largest ratio of length to diameter is 25, the nanorod exhibited a monoclinic single crystal structure. The diameter of barium chromate nanorods is between 24～38 nm and the largest ratio of length to diameter is 28. The rod had an orthorhombic single crystal structure. The products have optical properties which are different from those of bulk materials: the IR absorption peaks have slightly blue-shift, the fluorescent emission peaks have 9 nm and 15 nm blue-shift respectively compared to those of the bulk materials, and the UV-Vis spectra showed that the obvious absorption peaks respectively blue-shifted 30 nm and 35 nm compared to bulk that of materials as a result of quantum size effect. The synthesis mechanism of the products was discussed primarily.
Nanorods of lead chromate and barium chromate were synthesized by using artificial active membrane of celloidin as template and the cooperating effect of artificial active membrane with ethylenediamine. The results indicated that the diameter of lead chromate nanorods is between 28～55 nm and the largest ratio of length to diameter is 25, the nanorod exhibited a monoclinic single crystal structure. The diameter of barium chromate nanorods is between 24～38 nm and the largest ratio of length to diameter is 28. The rod had an orthorhombic single crystal structure. The products have optical properties which are different from those of bulk materials: the IR absorption peaks have slightly blue-shift, the fluorescent emission peaks have 9 nm and 15 nm blue-shift respectively compared to those of the bulk materials, and the UV-Vis spectra showed that the obvious absorption peaks respectively blue-shifted 30 nm and 35 nm compared to bulk that of materials as a result of quantum size effect. The synthesis mechanism of the products was discussed primarily.
