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2003 Volume 19 Issue 2
2003, 19(02): 97-99
doi: 10.3866/PKU.WHXB20030201
Abstract:
Metal-polysilane-silicon(MPS) structures were designed in this investigation. It was first discovered that the MPS structures possessed capacitance-voltage(C－V) characteristics, and the C－V characteristics were consistent with the branching densities of the polysilanes, i.e., with the increase in branching densities, the C－V curves drifted more dramatically towards the positive direction of the electrical voltage axis. The MPS structures may be promising in designing devices for the measurement of the branching densities of the branched polysilanes. Many of the flat-band voltages of the MPS structures were positive, which played positive roles in semiconductor devices.
Metal-polysilane-silicon(MPS) structures were designed in this investigation. It was first discovered that the MPS structures possessed capacitance-voltage(C－V) characteristics, and the C－V characteristics were consistent with the branching densities of the polysilanes, i.e., with the increase in branching densities, the C－V curves drifted more dramatically towards the positive direction of the electrical voltage axis. The MPS structures may be promising in designing devices for the measurement of the branching densities of the branched polysilanes. Many of the flat-band voltages of the MPS structures were positive, which played positive roles in semiconductor devices.
2003, 19(02): 100-104
doi: 10.3866/PKU.WHXB20030202
Abstract:
The photocatalytic oxidation of CO on Pd(2％)/TiO2 was investigated. It was found that CO oxidation activity on Pd/TiO2 was greatly enhanced if illuminated with UV light(λ=365 nm) as compared with that in the dark(the ratio of the above two rate constants is ca. 15). But on bare TiO2 no CO oxidation reaction was observed both in the dark and under UV light illumination. The photocatalytic enhancement of CO on Pd/TiO2 could be elucidated by the increase of surface concentration of oxygen atoms (or O－) on Pd and the spillover of oxygen atoms from Pd to TiO2.
The photocatalytic oxidation of CO on Pd(2％)/TiO2 was investigated. It was found that CO oxidation activity on Pd/TiO2 was greatly enhanced if illuminated with UV light(λ=365 nm) as compared with that in the dark(the ratio of the above two rate constants is ca. 15). But on bare TiO2 no CO oxidation reaction was observed both in the dark and under UV light illumination. The photocatalytic enhancement of CO on Pd/TiO2 could be elucidated by the increase of surface concentration of oxygen atoms (or O－) on Pd and the spillover of oxygen atoms from Pd to TiO2.
2003, 19(02): 105-108
doi: 10.3866/PKU.WHXB20030203
Abstract:
In this paper, the process of aspirin synthesis was studied by using on-line Raman spectroscopy. Wavelet analysis has been applied to remove the fluorescent background from the Raman spectra, and the variation of components concentration was determined with Multi-wavelength Linear Regression Method. The on-line Raman spectroscopy provided direct information about the variation of components concentration on the reaction time in the synthesis process.
In this paper, the process of aspirin synthesis was studied by using on-line Raman spectroscopy. Wavelet analysis has been applied to remove the fluorescent background from the Raman spectra, and the variation of components concentration was determined with Multi-wavelength Linear Regression Method. The on-line Raman spectroscopy provided direct information about the variation of components concentration on the reaction time in the synthesis process.
2003, 19(02): 109-114
doi: 10.3866/PKU.WHXB20030204
Abstract:
The electrical properties of BaEu2Ti4O12 were characterized by means of AC impedance spectroscopy in the frequency rang of 10－1～107 Hz. The experiment results indicate: (i) the permittivity value measured in this low frequency range is compatible with the published value measured in microwave range. The permittivity value obtained in high frequency range is net effect of bulk and grain boundary permittivitis; better-sintered ceramic has thinner grain boundary and may have larger permittivity value; (ii) when the sample was cooled down slowly from elevated temperature or annealed in O2-rich atmosphere, the conductivity was reduced, which may be explained by the reduction of oxygen vacancies in crystal. These treatments may lower the dielectric loss in microwave range.
The electrical properties of BaEu2Ti4O12 were characterized by means of AC impedance spectroscopy in the frequency rang of 10－1～107 Hz. The experiment results indicate: (i) the permittivity value measured in this low frequency range is compatible with the published value measured in microwave range. The permittivity value obtained in high frequency range is net effect of bulk and grain boundary permittivitis; better-sintered ceramic has thinner grain boundary and may have larger permittivity value; (ii) when the sample was cooled down slowly from elevated temperature or annealed in O2-rich atmosphere, the conductivity was reduced, which may be explained by the reduction of oxygen vacancies in crystal. These treatments may lower the dielectric loss in microwave range.
2003, 19(02): 115-119
doi: 10.3866/PKU.WHXB20030205
Abstract:
The thermodynamic properties of system HCl-NaCl-C2H6O2-H2O was studied by EMF measurement in the cells without liquid junction: Pt, H2 (105 Pa)|HCl (m), C2H6O2 (w), H2O (1－w) | AgCl-Ag (A) Pt, H2 (105 Pa)|HCl (mA), NaCl (mB), C2H6O2 (w), H2O（1－w）| AgCl-Ag (B) at constant total ionic strength I=0.5, 1.0, 1.5 and 2.0 mol•kg－1, from 5 to 45 ℃, where mA and mB are the molalities of HCl and NaCl, respectively, w is the mass fraction of glycol in the mixed solvent, which is 10％ during all measurement. The standard electrode potential of Ag-AgCl in the mixed solvent has been determined from cell (A). The activity coefficients of HCl γA in the mixed solvent system have been determined from cell(B). The results show that the activity coefficients of HCl in HCl-NaCl solutions still obey Harned’s Rule. The standard transfer Gibbs free energies of HCl have been calculated. The primary, secondary and total medium effects of HCl have been calculated and discussed.
The thermodynamic properties of system HCl-NaCl-C2H6O2-H2O was studied by EMF measurement in the cells without liquid junction: Pt, H2 (105 Pa)|HCl (m), C2H6O2 (w), H2O (1－w) | AgCl-Ag (A) Pt, H2 (105 Pa)|HCl (mA), NaCl (mB), C2H6O2 (w), H2O（1－w）| AgCl-Ag (B) at constant total ionic strength I=0.5, 1.0, 1.5 and 2.0 mol•kg－1, from 5 to 45 ℃, where mA and mB are the molalities of HCl and NaCl, respectively, w is the mass fraction of glycol in the mixed solvent, which is 10％ during all measurement. The standard electrode potential of Ag-AgCl in the mixed solvent has been determined from cell (A). The activity coefficients of HCl γA in the mixed solvent system have been determined from cell(B). The results show that the activity coefficients of HCl in HCl-NaCl solutions still obey Harned’s Rule. The standard transfer Gibbs free energies of HCl have been calculated. The primary, secondary and total medium effects of HCl have been calculated and discussed.
2003, 19(02): 120-124
doi: 10.3866/PKU.WHXB20030206
Abstract:
In reverse microemulsions, sodium bis(2-ethylhexyl) sulfosuccinate(Aerosol OT, AOT) has an ability to solubilize much larger amount of water than dimethyl sulfoxide(DMSO), formamide and acetonitrile(the amount of the polar solvent solubilized in AOT reverse microemulsions: water >acetonitrile >formamide >DMSO). In the microemulsions with the mixtures of nonaqueous polar solvent and water as polar phases, the solubilization of formamide and acetonitrile is in anta nism to that of water, while the presence of water in a certain extent increases the solubilized amount of DMSO. The influences of various polar solvents on the conductivity properties of the reverse microemulsions have been studied.
In reverse microemulsions, sodium bis(2-ethylhexyl) sulfosuccinate(Aerosol OT, AOT) has an ability to solubilize much larger amount of water than dimethyl sulfoxide(DMSO), formamide and acetonitrile(the amount of the polar solvent solubilized in AOT reverse microemulsions: water >acetonitrile >formamide >DMSO). In the microemulsions with the mixtures of nonaqueous polar solvent and water as polar phases, the solubilization of formamide and acetonitrile is in anta nism to that of water, while the presence of water in a certain extent increases the solubilized amount of DMSO. The influences of various polar solvents on the conductivity properties of the reverse microemulsions have been studied.
2003, 19(02): 125-129
doi: 10.3866/PKU.WHXB20030207
Abstract:
B3LYP and CCSD(T) methods were employed to investigate the systems of R－C≡P(R=－BH2, －CH3,－NH2, －OH). The results indicate that isomers P≡C－BH2 and CH3－C≡P containing C≡P triple bond are thermodynamically the most stable species in BH2－C≡P and CH3－C≡P systems, respectively. But in the systems of HO－C≡P and NH2－C≡P, H－P=C=O and N≡C－PH2 containing C≡N triple bond are thermodynamically the most stable species, respectively. The calculated results on the kinetic stability indicate that for R－C≡P(R=－BH2,－NH2) systems, in which no experimental information are available, five isomers are kinetically stable. In HO－C≡P system, two kinetically stable species are located. Isomer H－P=C=O has been detected in experiment, and in view of higher kinetic stability, another isomer HO－C≡P should be experimentally observable. For CH3－C≡P system, isomer CH3－C≡P has been observed in experiment, and another kinetically stable isomer HC≡C－PH2 ought to be detected in future experiments.
B3LYP and CCSD(T) methods were employed to investigate the systems of R－C≡P(R=－BH2, －CH3,－NH2, －OH). The results indicate that isomers P≡C－BH2 and CH3－C≡P containing C≡P triple bond are thermodynamically the most stable species in BH2－C≡P and CH3－C≡P systems, respectively. But in the systems of HO－C≡P and NH2－C≡P, H－P=C=O and N≡C－PH2 containing C≡N triple bond are thermodynamically the most stable species, respectively. The calculated results on the kinetic stability indicate that for R－C≡P(R=－BH2,－NH2) systems, in which no experimental information are available, five isomers are kinetically stable. In HO－C≡P system, two kinetically stable species are located. Isomer H－P=C=O has been detected in experiment, and in view of higher kinetic stability, another isomer HO－C≡P should be experimentally observable. For CH3－C≡P system, isomer CH3－C≡P has been observed in experiment, and another kinetically stable isomer HC≡C－PH2 ought to be detected in future experiments.
2003, 19(02): 130-133
doi: 10.3866/PKU.WHXB20030208
Abstract:
The structure of free base phthalocyanine (H2Pc) has been predicted using density functional theory (DFT) at the B3LYP/6-31G level and time-dependent density functional theory (TDDFT) has been applied to the excited states of H2Pc.The effects of tetraaza substitutions and tetrabenzo annulations on the molecular orbitals and excited states of H2Pc were examined by the comparison with H2P, H2Pz and H2TBP.These substitutions lead to the inversion of HOMO-1 (132 b1u) and HOMO-3 (130 b1u) and as a result the spectra of H2Pc could not be interpreted by using the uterman four-orbital model. The effects of tetraaza subsitution are especially obvious which cause not only the B band but also the Q bands of H2Pz and H2Pc unable to be interpreted by using the uterman four-orbital model. Both the tetraaza substitutions and tetrabenzo annulations cause the oscillator strengths of Q band stronger, so the oscillator strengths of H2Pc are the largest among these compounds. The TDDFT energies are in od agreement with the experimental spectra.
The structure of free base phthalocyanine (H2Pc) has been predicted using density functional theory (DFT) at the B3LYP/6-31G level and time-dependent density functional theory (TDDFT) has been applied to the excited states of H2Pc.The effects of tetraaza substitutions and tetrabenzo annulations on the molecular orbitals and excited states of H2Pc were examined by the comparison with H2P, H2Pz and H2TBP.These substitutions lead to the inversion of HOMO-1 (132 b1u) and HOMO-3 (130 b1u) and as a result the spectra of H2Pc could not be interpreted by using the uterman four-orbital model. The effects of tetraaza subsitution are especially obvious which cause not only the B band but also the Q bands of H2Pz and H2Pc unable to be interpreted by using the uterman four-orbital model. Both the tetraaza substitutions and tetrabenzo annulations cause the oscillator strengths of Q band stronger, so the oscillator strengths of H2Pc are the largest among these compounds. The TDDFT energies are in od agreement with the experimental spectra.
2003, 19(02): 134-138
doi: 10.3866/PKU.WHXB20030209
Abstract:
The biothermochemical characteristics of the actions of two kinds of cationic lanthanide(III) monoporphyrinate complexes {[Re(TMP)(H2O)3]Cl, Re=Y, Yb, TMP=5,10,15,20 -tetrakis(4’-methoxyphenyl)porphyrin} on growth metabolism of Escherichia coli were studied by means of a LKB-2277 bioactivity monitor at 37 ℃.The maximum power, Pmax; the growth rate constant k1,k2; inhibitive ratio I(％) and half inhibition concentration cI,50 (mg•L-1),respectively, were obtained. Experimental results show that porphyrinate complexes possess the bi-directional biological effection: they stimulate the growth of the E. coli at lower concentration but inhibit the growth at higher concentration. Inhibitory effection of [Yb(TMP)(H2O)3]Cl (cI,50=143 mg•L-1) is stronger than that of [Y(TMP)(H2O)3]Cl.
The biothermochemical characteristics of the actions of two kinds of cationic lanthanide(III) monoporphyrinate complexes {[Re(TMP)(H2O)3]Cl, Re=Y, Yb, TMP=5,10,15,20 -tetrakis(4’-methoxyphenyl)porphyrin} on growth metabolism of Escherichia coli were studied by means of a LKB-2277 bioactivity monitor at 37 ℃.The maximum power, Pmax; the growth rate constant k1,k2; inhibitive ratio I(％) and half inhibition concentration cI,50 (mg•L-1),respectively, were obtained. Experimental results show that porphyrinate complexes possess the bi-directional biological effection: they stimulate the growth of the E. coli at lower concentration but inhibit the growth at higher concentration. Inhibitory effection of [Yb(TMP)(H2O)3]Cl (cI,50=143 mg•L-1) is stronger than that of [Y(TMP)(H2O)3]Cl.
2003, 19(02): 139-143
doi: 10.3866/PKU.WHXB20030210
Abstract:
A general model for hydrogen adsorption is derived to discuss the compressibility of the hydrogen molecules on the adsorption surface caused by the strong adsorptive potential exerted by the carbon wall. The mono-layer capacity (see Table 1) inside the tube of the MWCNTs tested in our laboratory is evalued by the comparison studies on the adsorptive performance between the tubular pore and the slit-pore, the results show that better adsorptive performance can only be obtained when temperature is getting lower or the diameter of the tube is getting smaller (see Fig.1). From the model, the strong attraction to the surface may even cause hydrogen molecules to attain much higher densities than that of liquid hydrogen, and this will surely make adsorbed hydrogen molecules to behave as repulsion among each other. This phenomenon is discussed in terms of experimental data and the ascertained model (see Fig.3). A linear form of the model is applied to determine the interaction energy between hydrogen molecules in the adsorbed layer from the experimental data. Analysis of the experimental data of hydrogen adsorption over a wide range of pressure and temperature shows that the energies of hydrogen-hydrogen interactions in the adsorbed phase are positive in low temperature region(< 200 K) and obtain the highest value in the temperature range of 160～180 K, but will be negative when the temperature is above 230 K(see Fig.4), indicating the repulsions among the adsorbed hydrogen molecules are prominent in low temperature, however, the attractions among the adsorbed hydrogen molecules at higher temperature are hard to understand because the pressures are also high in those cases. Comments are made that the chemical adsorption should be included to interpret the experimental data at higher temperatures. The results presented here also show that the concept of ‘maximum capacity’ for hydrogen adsorption should differ from the density of the adsorbed hydrogen molecules.
A general model for hydrogen adsorption is derived to discuss the compressibility of the hydrogen molecules on the adsorption surface caused by the strong adsorptive potential exerted by the carbon wall. The mono-layer capacity (see Table 1) inside the tube of the MWCNTs tested in our laboratory is evalued by the comparison studies on the adsorptive performance between the tubular pore and the slit-pore, the results show that better adsorptive performance can only be obtained when temperature is getting lower or the diameter of the tube is getting smaller (see Fig.1). From the model, the strong attraction to the surface may even cause hydrogen molecules to attain much higher densities than that of liquid hydrogen, and this will surely make adsorbed hydrogen molecules to behave as repulsion among each other. This phenomenon is discussed in terms of experimental data and the ascertained model (see Fig.3). A linear form of the model is applied to determine the interaction energy between hydrogen molecules in the adsorbed layer from the experimental data. Analysis of the experimental data of hydrogen adsorption over a wide range of pressure and temperature shows that the energies of hydrogen-hydrogen interactions in the adsorbed phase are positive in low temperature region(< 200 K) and obtain the highest value in the temperature range of 160～180 K, but will be negative when the temperature is above 230 K(see Fig.4), indicating the repulsions among the adsorbed hydrogen molecules are prominent in low temperature, however, the attractions among the adsorbed hydrogen molecules at higher temperature are hard to understand because the pressures are also high in those cases. Comments are made that the chemical adsorption should be included to interpret the experimental data at higher temperatures. The results presented here also show that the concept of ‘maximum capacity’ for hydrogen adsorption should differ from the density of the adsorbed hydrogen molecules.
2003, 19(02): 144-149
doi: 10.3866/PKU.WHXB20030211
Abstract:
Electrochemical impedance spectroscopy (EIS) of bare LY12 Al alloy and LY12/epoxy electrodes in 3.5％ (mass fraction) NaCl solution has been investigated, respectively. The results show that the impedance spectra for bare LY12 alloys below the pitting potential (Epp) consist of two capacitance loops, relating to the formation of Cl－ containing salt film at high frequencies and anodically electrochemical dissolution of Al at low frequencies. An inductive loop was detected at low frequencies with potentials above the Epp. Water tends to uptake in epoxy coating preferentially in the early time. After water and oxygen reach the alloy base the electrochemical reaction interface will form on the base, and the alloy is corroded. Then the diffusion of the corrosion products becomes the rate-determining step in the case of coating barrier. When the slow diffusion particle Cl－ accesses to coating/alloy interface, Cl－ interacts with the stimulating corrosion products and a chemical reaction salt film is formed, resulting in the presence of film impedance and the disappear of diffusion impedance in EIS. According to the above experimental phenomena different impedance models in various immersion stages are proposed to fit the EIS measurements.
Electrochemical impedance spectroscopy (EIS) of bare LY12 Al alloy and LY12/epoxy electrodes in 3.5％ (mass fraction) NaCl solution has been investigated, respectively. The results show that the impedance spectra for bare LY12 alloys below the pitting potential (Epp) consist of two capacitance loops, relating to the formation of Cl－ containing salt film at high frequencies and anodically electrochemical dissolution of Al at low frequencies. An inductive loop was detected at low frequencies with potentials above the Epp. Water tends to uptake in epoxy coating preferentially in the early time. After water and oxygen reach the alloy base the electrochemical reaction interface will form on the base, and the alloy is corroded. Then the diffusion of the corrosion products becomes the rate-determining step in the case of coating barrier. When the slow diffusion particle Cl－ accesses to coating/alloy interface, Cl－ interacts with the stimulating corrosion products and a chemical reaction salt film is formed, resulting in the presence of film impedance and the disappear of diffusion impedance in EIS. According to the above experimental phenomena different impedance models in various immersion stages are proposed to fit the EIS measurements.
2003, 19(02): 150-153
doi: 10.3866/PKU.WHXB20030212
Abstract:
The chemical reduction process has been used for the synthesis of silver powder in ethylene glycol. The mechanism for the formation of flake powder has been proposed on the basis of analysis of the main factors influencing the morphology of silver powder. The results showed that the key factor for the formation of flake silver powder was the heterogeneous seeds of platinum firstly reduced. It offered a plane for precipitation and reduction of silver later. The concentration of free silver ion was controlled by polyvinyl pyrrolidone (PVP) by the formation of complex. And more PVP was absorbed on the surface of silver ion selectively. Thus the nucleation and growth of silver was influenced and flake silver powder formed.
The chemical reduction process has been used for the synthesis of silver powder in ethylene glycol. The mechanism for the formation of flake powder has been proposed on the basis of analysis of the main factors influencing the morphology of silver powder. The results showed that the key factor for the formation of flake silver powder was the heterogeneous seeds of platinum firstly reduced. It offered a plane for precipitation and reduction of silver later. The concentration of free silver ion was controlled by polyvinyl pyrrolidone (PVP) by the formation of complex. And more PVP was absorbed on the surface of silver ion selectively. Thus the nucleation and growth of silver was influenced and flake silver powder formed.
2003, 19(02): 154-157
doi: 10.3866/PKU.WHXB20030213
Abstract:
Raman spectra of aqueous solutions of CaCl2 and MgCl2 in the OH stretching region (2 500 to 4 000 cm－1) with various concentrations below 1.0 mol•L－1 were measured. Computer deconvolutions of the Raman spectra allow the percent of tetrahedral hydrogen bonded structure of water to be determined. It is shown that CaCl2 and MgCl2 break tetrahedral hydrogen bonded structure of water and the breaking effect of Ca2＋ is stronger than that of Mg2＋. By comparison with results of 17O NMR, it is deduced that CaCl2 and MgCl2 promote structure of water as a whole by forming hydrogen bonding among water molecules with fewer hydrogen bonding even though they break tetrahedral hydrogen bonded structure of water.
Raman spectra of aqueous solutions of CaCl2 and MgCl2 in the OH stretching region (2 500 to 4 000 cm－1) with various concentrations below 1.0 mol•L－1 were measured. Computer deconvolutions of the Raman spectra allow the percent of tetrahedral hydrogen bonded structure of water to be determined. It is shown that CaCl2 and MgCl2 break tetrahedral hydrogen bonded structure of water and the breaking effect of Ca2＋ is stronger than that of Mg2＋. By comparison with results of 17O NMR, it is deduced that CaCl2 and MgCl2 promote structure of water as a whole by forming hydrogen bonding among water molecules with fewer hydrogen bonding even though they break tetrahedral hydrogen bonded structure of water.
2003, 19(02): 158-162
doi: 10.3866/PKU.WHXB20030214
Abstract:
The threshold energies of photovoltaic response of both doped nano-La0.8Sr0.2FeO3 and undoped nano-LaFeO3 were probed by the vacuum adsorptive surface photovoltage technique. The results show that the threshold energy of nano-La0.8Sr0.2FeO3 is obviously smaller than that of nano-LaFeO3 under exposure to the sensor gas (ethanol vapor). And the difference between threshold energies of the two samples exposed to the sensor gas is increased, compared with that of them exposed to air. Moreover, by means of the difference of the threshold energies before and after doping Sr2＋ ion, the reorganization energy of surface electrons of doped sample can be quantitative calculated, i.e., Ers=b－a (where Ers is reorganization energy of surface electron of the sample, b and a is threshold energy before and after doping Sr2＋ ion respectively). The reason for producing reorganization energy of surface electrons is discussed.
The threshold energies of photovoltaic response of both doped nano-La0.8Sr0.2FeO3 and undoped nano-LaFeO3 were probed by the vacuum adsorptive surface photovoltage technique. The results show that the threshold energy of nano-La0.8Sr0.2FeO3 is obviously smaller than that of nano-LaFeO3 under exposure to the sensor gas (ethanol vapor). And the difference between threshold energies of the two samples exposed to the sensor gas is increased, compared with that of them exposed to air. Moreover, by means of the difference of the threshold energies before and after doping Sr2＋ ion, the reorganization energy of surface electrons of doped sample can be quantitative calculated, i.e., Ers=b－a (where Ers is reorganization energy of surface electron of the sample, b and a is threshold energy before and after doping Sr2＋ ion respectively). The reason for producing reorganization energy of surface electrons is discussed.
2003, 19(02): 163-166
doi: 10.3866/PKU.WHXB20030215
Abstract:
Three-dimensional quantitative structure-activity relationships of isoflavone and quinolone derivatives as tyrosine kinase inhibitors were studied using the flexible atom receptor model(FLARM) method. Some 3D-QSAR models were built with high correlation coefficients. The flexible atom receptor model also gives the pseudo receptor model， which indicates possible interactions between receptor and the ligand. The possible interactions between the ligand and the receptor in the pseudo receptor model are in accordance with those in the Novartis pharmacophore model.
Three-dimensional quantitative structure-activity relationships of isoflavone and quinolone derivatives as tyrosine kinase inhibitors were studied using the flexible atom receptor model(FLARM) method. Some 3D-QSAR models were built with high correlation coefficients. The flexible atom receptor model also gives the pseudo receptor model， which indicates possible interactions between receptor and the ligand. The possible interactions between the ligand and the receptor in the pseudo receptor model are in accordance with those in the Novartis pharmacophore model.
2003, 19(02): 167-170
doi: 10.3866/PKU.WHXB20030216
Abstract:
Using mixed surfactants cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX-100) as co-template and tetraethylorthosilicate (TEOS) as silica source,MCM-48 molecular sieves were hydrothermally prepared. The yields of MCM-48 molecular sieves could be considerably increased by adjusting pH of the solutions which had been statically crystallized for three days, at the same time the utilizing efficiency of the mixed surfactants was much higher than that of only CTAB as template.
Using mixed surfactants cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX-100) as co-template and tetraethylorthosilicate (TEOS) as silica source,MCM-48 molecular sieves were hydrothermally prepared. The yields of MCM-48 molecular sieves could be considerably increased by adjusting pH of the solutions which had been statically crystallized for three days, at the same time the utilizing efficiency of the mixed surfactants was much higher than that of only CTAB as template.
2003, 19(02): 171-173
doi: 10.3866/PKU.WHXB20030217
Abstract:
The nano-TiO2/Poly(butyl acrylate) composite film was prepared by microemulsion in-situ polymerization method on glass substrate. The structure of the thin film was characterized by FTIR, XPS and HRTEM (high-resolution TEM) techniques. The results of FTIR analyses indicated that the poly(butyl acrylate) networks formed through in-situ polymerization. XPS results showed that Ti(OC4H9)4 changed into TiO2 through hydrolyzation. HRTEM of polymerized thin film indicated that the TiO2 nanolines are dispersed in the poly(butyl acrylate) networks.
The nano-TiO2/Poly(butyl acrylate) composite film was prepared by microemulsion in-situ polymerization method on glass substrate. The structure of the thin film was characterized by FTIR, XPS and HRTEM (high-resolution TEM) techniques. The results of FTIR analyses indicated that the poly(butyl acrylate) networks formed through in-situ polymerization. XPS results showed that Ti(OC4H9)4 changed into TiO2 through hydrolyzation. HRTEM of polymerized thin film indicated that the TiO2 nanolines are dispersed in the poly(butyl acrylate) networks.
2003, 19(02): 174-176
doi: 10.3866/PKU.WHXB20030218
Abstract:
The Monte Carlo method and Lennard-Jones plus Axilord-Teller （LJ＋AT） potential were employed to investigate the formation and growth mechanism of palladium clusters in gas phase. It was found by the simulation that the icosahedron Pd13 cluster formed spontaneously from gas phase, and larger Pd clusters formed through adding atoms to the Pd13 surface. Besides Pd13 and Pd55, Pd19 and Pd39 clusters also had five-fold symmetry, and all of them were stable energetically.
The Monte Carlo method and Lennard-Jones plus Axilord-Teller （LJ＋AT） potential were employed to investigate the formation and growth mechanism of palladium clusters in gas phase. It was found by the simulation that the icosahedron Pd13 cluster formed spontaneously from gas phase, and larger Pd clusters formed through adding atoms to the Pd13 surface. Besides Pd13 and Pd55, Pd19 and Pd39 clusters also had five-fold symmetry, and all of them were stable energetically.
Electrochemical Preparation and Characterization of Metal Multilayers and Metal Multilayer Nanowires
2003, 19(02): 177-180
doi: 10.3866/PKU.WHXB20030219
Abstract:
Cu/Co multilayers were prepared by single bath technology (SBT) and double bath technology (DBT), respectively. The technological conditions of SBT and DBT were studied. Using electrochemical method, XRD and SEM, the layer structure of the prepared multilayer was affirmed. The magnetoresistance property of Cu/Co multilayers was measured and the results show that the GMR of Cu/Co multilayers is 7.5％ at 2500 Gs. On the base of the preparation of Cu/Co multilayers, Cu/Co multilayer nanowires arrays on porous anodic aluminum oxide templates were fabricated and its structure was characterized by TEM. The micrographs exhibited that the diameter of the Cu/Co multilayer nanowires is about 120 nm and length up to 10 μm.
Cu/Co multilayers were prepared by single bath technology (SBT) and double bath technology (DBT), respectively. The technological conditions of SBT and DBT were studied. Using electrochemical method, XRD and SEM, the layer structure of the prepared multilayer was affirmed. The magnetoresistance property of Cu/Co multilayers was measured and the results show that the GMR of Cu/Co multilayers is 7.5％ at 2500 Gs. On the base of the preparation of Cu/Co multilayers, Cu/Co multilayer nanowires arrays on porous anodic aluminum oxide templates were fabricated and its structure was characterized by TEM. The micrographs exhibited that the diameter of the Cu/Co multilayer nanowires is about 120 nm and length up to 10 μm.
2003, 19(02): 181-184
doi: 10.3866/PKU.WHXB20030220
Abstract:
The kinetics of dissolution and phase transformation of 2M •2B2O3•MgCl2•14H2O in water at 87 ℃ were studied. The results of liquid phases anlysized at a given time intervals and solid phases identified by IR and XRD show that 2M •2 B2O3•MgCl2•14H2O dissolved incongruently in water and the process was not the same at low temperature, a new crystal midproduct (M •B2O3•4H2O) was formed, the final solid phase was pinnoite (M •B2O3•3H2O). With the aid of Simplex Optimum Method and Runge-Kutta Digital Solution of differential equation system, the experimental data was fitted. The kinetic equation of the crystallization reaction was given and a mechanism of crystallization reaction was proposed.
The kinetics of dissolution and phase transformation of 2M •2B2O3•MgCl2•14H2O in water at 87 ℃ were studied. The results of liquid phases anlysized at a given time intervals and solid phases identified by IR and XRD show that 2M •2 B2O3•MgCl2•14H2O dissolved incongruently in water and the process was not the same at low temperature, a new crystal midproduct (M •B2O3•4H2O) was formed, the final solid phase was pinnoite (M •B2O3•3H2O). With the aid of Simplex Optimum Method and Runge-Kutta Digital Solution of differential equation system, the experimental data was fitted. The kinetic equation of the crystallization reaction was given and a mechanism of crystallization reaction was proposed.
2003, 19(02): 185-192
doi: 10.3866/PKU.WHXB20030221
Abstract:
This paper gives the experimental setup and the theory of surfactant-selective membrane electrode applying in the study of the interaction between the surfactants and the polymers. The applications of the surfactant-selective membrane in studying the interactions between ionic surfactants and different kinds of polymers are also reviewed. The results have indicated that the binding isotherm of surfactant on polymer is a very od method to investigate the interactions between surfactants and polymers. The earlier studies mainly concerned with surfactants-polymers systems at relatively higher polymer or surfactant concentrations. However, the introduction of the surfactant selective membrane electrode has allowed the extension of these studies to very low surfactant concentration.
This paper gives the experimental setup and the theory of surfactant-selective membrane electrode applying in the study of the interaction between the surfactants and the polymers. The applications of the surfactant-selective membrane in studying the interactions between ionic surfactants and different kinds of polymers are also reviewed. The results have indicated that the binding isotherm of surfactant on polymer is a very od method to investigate the interactions between surfactants and polymers. The earlier studies mainly concerned with surfactants-polymers systems at relatively higher polymer or surfactant concentrations. However, the introduction of the surfactant selective membrane electrode has allowed the extension of these studies to very low surfactant concentration.
