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2002 Volume 18 Issue 7
2002, 18(07): 577-580
doi: 10.3866/PKU.WHXB20020701
Abstract:
This paper shows quantitatively the consequence of adsorbed water on N2 or O2 adsorbed on LiLSX lithium exchanged low silica X zeolite. In the range of 0～32 H2O/u.c.(unit cell), water present in LiLSX sharply declined the capacity for N2 or O2 adsorption. The reason is that the adsorption mainly occurs on the Li＋ ions on the 32 SIII sites in LiLSX. When H2O molecules residual after the desorption of hydrated LiLSX are adsorbed tightly on Li＋ at SIII site, they block the adsorption of nitrogen or oxygen. Water molecules introduced from outside into the dehydrated LiLSX influenc the adsorption of nitrogen less seriously than the residual water molecules do, because of the heterogeneity of adsorption sites and the diffusion behavior of water in LiLSX. When diffused into the inner part of a LiLSX particle, some water molecules may adsorb on weaker sites other than the strongest SIII sites.
This paper shows quantitatively the consequence of adsorbed water on N2 or O2 adsorbed on LiLSX lithium exchanged low silica X zeolite. In the range of 0～32 H2O/u.c.(unit cell), water present in LiLSX sharply declined the capacity for N2 or O2 adsorption. The reason is that the adsorption mainly occurs on the Li＋ ions on the 32 SIII sites in LiLSX. When H2O molecules residual after the desorption of hydrated LiLSX are adsorbed tightly on Li＋ at SIII site, they block the adsorption of nitrogen or oxygen. Water molecules introduced from outside into the dehydrated LiLSX influenc the adsorption of nitrogen less seriously than the residual water molecules do, because of the heterogeneity of adsorption sites and the diffusion behavior of water in LiLSX. When diffused into the inner part of a LiLSX particle, some water molecules may adsorb on weaker sites other than the strongest SIII sites.
2002, 18(07): 581-584
doi: 10.3866/PKU.WHXB20020702
Abstract:
Single strand oli deoxynucleotide was covalently attached to the alkyl modified silicon (111) surface through ester condensation reaction and the result was characterized by fluorescent spectra.The wafers modified by ss-oli deoxynucleotide were used as DNA probes and the reusability of the resultant wafer was investigated.Its perfect stability in target detection process may promote the wider and more efficient application of the gene chip technology.
Single strand oli deoxynucleotide was covalently attached to the alkyl modified silicon (111) surface through ester condensation reaction and the result was characterized by fluorescent spectra.The wafers modified by ss-oli deoxynucleotide were used as DNA probes and the reusability of the resultant wafer was investigated.Its perfect stability in target detection process may promote the wider and more efficient application of the gene chip technology.
2002, 18(07): 585-589
doi: 10.3866/PKU.WHXB20020703
Abstract:
Density functional theory with the B3LYP functional is used to determine the geometries and vibrational frequencies of HC 2nH (n=1～13). The vertical transition energies of HC 2nH (n=1～5) have been estimated by TD-B3LYP/cc-PVTZ calculations.On the basis of theoretical calculations,a generally analytic expression for the chain-size n dependence of the vertical transition energy was suggested,which can predict excellent excitation energies in comparison with available observed bands.Current calculations reveal that a nonlinear behavior for the even-numbered HC2nH between the excitation energy and the number of carbon atoms.
Density functional theory with the B3LYP functional is used to determine the geometries and vibrational frequencies of HC 2nH (n=1～13). The vertical transition energies of HC 2nH (n=1～5) have been estimated by TD-B3LYP/cc-PVTZ calculations.On the basis of theoretical calculations,a generally analytic expression for the chain-size n dependence of the vertical transition energy was suggested,which can predict excellent excitation energies in comparison with available observed bands.Current calculations reveal that a nonlinear behavior for the even-numbered HC2nH between the excitation energy and the number of carbon atoms.
2002, 18(07): 590-594
doi: 10.3866/PKU.WHXB20020704
Abstract:
By using microcalorimetry method,we have studied ura-auxotrophic mutant of saccharomyces cerevisiae AY,and 3 strains transformed from saccharomyces cerevisiae AY by plasmids.Inoculated in basic medium,ura-auxotrophic mutant of saccharomyces cerevisiae AY shows no heat effect,which means that it can not grow; but it grows in peptone-gluocose medium,and grows vi rously in YPD medium.Adding ura to the basic medium,ura-auxotrophic mutant of saccharomyces cerevisiae AY is then able to grow,and the constant of specific growth rate increases as more ura is added.All of the 3 transformed strains grow in the basic medium,but the thermogenic gragh differs because the plasmids differ in their structure and function.The result shows the difference of genetic characteristics among the target strains.
By using microcalorimetry method,we have studied ura-auxotrophic mutant of saccharomyces cerevisiae AY,and 3 strains transformed from saccharomyces cerevisiae AY by plasmids.Inoculated in basic medium,ura-auxotrophic mutant of saccharomyces cerevisiae AY shows no heat effect,which means that it can not grow; but it grows in peptone-gluocose medium,and grows vi rously in YPD medium.Adding ura to the basic medium,ura-auxotrophic mutant of saccharomyces cerevisiae AY is then able to grow,and the constant of specific growth rate increases as more ura is added.All of the 3 transformed strains grow in the basic medium,but the thermogenic gragh differs because the plasmids differ in their structure and function.The result shows the difference of genetic characteristics among the target strains.
2002, 18(07): 595-599
doi: 10.3866/PKU.WHXB20020705
Abstract:
Densities of glycine in various aqueous urea,monomethylurea(MMU),dimethylurea (DMU) solutions have been measured at 298.15 K with an Anton Paar Model 55 densimeter.From these densities,apparent molar volumes and limited partial molar volumes have been calculated; transfer volumes from water to aqueous urea,MMU,DMU solutions have also been obtained.Furthermore,the hydration numbers and volumetric interaction coefficients for glycine were evaluated.Solvent effect was discussed in detail.The results show that all of the transfer volumes in different solutions are positive,and increase with increasing the co-solutes (urea,MMU,DMU) concentration; the hydration numbers for glycine in three solutions all decrease with increasing the co-solutes concentration.It was concluded that interaction between amino acids and urea,MMU,DMU molecule is dominated by 1:1 form from the results of the volumetric interaction coefficients.
Densities of glycine in various aqueous urea,monomethylurea(MMU),dimethylurea (DMU) solutions have been measured at 298.15 K with an Anton Paar Model 55 densimeter.From these densities,apparent molar volumes and limited partial molar volumes have been calculated; transfer volumes from water to aqueous urea,MMU,DMU solutions have also been obtained.Furthermore,the hydration numbers and volumetric interaction coefficients for glycine were evaluated.Solvent effect was discussed in detail.The results show that all of the transfer volumes in different solutions are positive,and increase with increasing the co-solutes (urea,MMU,DMU) concentration; the hydration numbers for glycine in three solutions all decrease with increasing the co-solutes concentration.It was concluded that interaction between amino acids and urea,MMU,DMU molecule is dominated by 1:1 form from the results of the volumetric interaction coefficients.
2002, 18(07): 600-603
doi: 10.3866/PKU.WHXB20020706
Abstract:
Geometrical optimization and electrostatic potential calculations have been performed at HF/6-31G level for 92 disubstituted benzene molecules. Linear correlation between the n-octanol /water partition coefficient and the theoretical descriptors of molecular structure has been established by multiple regression method. It appears that Σ,Vmin,Vs,max,V,APS and μ/V could be well used to express the quantitative structure － hydrophilic relationships of the 92 molecules. A test set containing 111 molecules was used to investigate the predictive ability of the QSPR. The result is satisfing.
Geometrical optimization and electrostatic potential calculations have been performed at HF/6-31G level for 92 disubstituted benzene molecules. Linear correlation between the n-octanol /water partition coefficient and the theoretical descriptors of molecular structure has been established by multiple regression method. It appears that Σ,Vmin,Vs,max,V,APS and μ/V could be well used to express the quantitative structure － hydrophilic relationships of the 92 molecules. A test set containing 111 molecules was used to investigate the predictive ability of the QSPR. The result is satisfing.
2002, 18(07): 604-608
doi: 10.3866/PKU.WHXB20020707
Abstract:
The thiolterminated βcyclodextrin derivative(βCDd) was attached to the surface of ld electrode of quartz crystal resonator by selfassembly. The inclusion reactions of αnaphthalenesulfonate and βnaphthalenesulfonate with βCDd were monitored in situ by using quartz crystal microbalance (QCM). The influences of temperature, concentration, and the substituting position on naphthalene nucleus on the inclusion constant(Kin) and the rate constant(ka) were investigated. The relational expressions of Kin and ka were deduced theoretically and were testified by experimental results. The results obtained indicated that the stoichiometry of the inclusion complexes formed is 1:1 for the host βCDd with naphthalenesulfonate, that the inclusion reactions tallied the Langmuir adsorption model, that the substituting position on naphthalene nucleus has great effect on Kin and ka , and that the inclusion behaviors of the two derivatives with substituent at different positions with βCDd show obvious difference.
The thiolterminated βcyclodextrin derivative(βCDd) was attached to the surface of ld electrode of quartz crystal resonator by selfassembly. The inclusion reactions of αnaphthalenesulfonate and βnaphthalenesulfonate with βCDd were monitored in situ by using quartz crystal microbalance (QCM). The influences of temperature, concentration, and the substituting position on naphthalene nucleus on the inclusion constant(Kin) and the rate constant(ka) were investigated. The relational expressions of Kin and ka were deduced theoretically and were testified by experimental results. The results obtained indicated that the stoichiometry of the inclusion complexes formed is 1:1 for the host βCDd with naphthalenesulfonate, that the inclusion reactions tallied the Langmuir adsorption model, that the substituting position on naphthalene nucleus has great effect on Kin and ka , and that the inclusion behaviors of the two derivatives with substituent at different positions with βCDd show obvious difference.
2002, 18(07): 609-612
doi: 10.3866/PKU.WHXB20020708
Abstract:
Alginate-Chitosan-Alginate(ACA) ion replacement gels are a novel ion adsorbent and are hopeful to be used to cure human toxicosis metallicus.In this paper,ion replacement mechanism of ACA on Pb2＋ was studied.Sol-gel phase interface of ion replacement process of ACA was observed by optical microscope photo.On the basis of it,mobile boundary model (MBM) was used to describe ion replacement process.The results show that the model has high reliability.Ion replacement process was controlled by intraparticle diffusion control (PDC)(to see Fig.3).The chelating ion-exchanger D418 and macropore acrylic resin D113 were studied for comparative analysis.The results show that ACA ion replacement gels has much faster ion exchange velocity than D418 and D113 resin and the two ion adsorbents have different ion replacement mechanism.Ion replacement of ACA is a sol-gel phase transition process.
Alginate-Chitosan-Alginate(ACA) ion replacement gels are a novel ion adsorbent and are hopeful to be used to cure human toxicosis metallicus.In this paper,ion replacement mechanism of ACA on Pb2＋ was studied.Sol-gel phase interface of ion replacement process of ACA was observed by optical microscope photo.On the basis of it,mobile boundary model (MBM) was used to describe ion replacement process.The results show that the model has high reliability.Ion replacement process was controlled by intraparticle diffusion control (PDC)(to see Fig.3).The chelating ion-exchanger D418 and macropore acrylic resin D113 were studied for comparative analysis.The results show that ACA ion replacement gels has much faster ion exchange velocity than D418 and D113 resin and the two ion adsorbents have different ion replacement mechanism.Ion replacement of ACA is a sol-gel phase transition process.
2002, 18(07): 613-616
doi: 10.3866/PKU.WHXB20020709
Abstract:
Metallic nickel was electrochemically dissolved in absolute ethanol and acetylacetone solution in the presence of Bu4NBr(as electronconductive additive). The electrolyte solution containing the precursor was then directly hydrolyzed to obtain nanocrystalline NiO. The precursor was characterized by FTIR、1HNMR、Raman spectra and the nanopowder was characterized by XRD and TEM. The results showed that the NiO powder after hydrolysis was amorphous but formed the cubic NaCl structure when calcined at 350 ℃,the NiO powder have a narrow size distribution of 5～10 nm after annealed at 600 ℃. Characterization of the electrochemical product revealed that Ni(OEt)2(acac)2 was formed by anode dissolution of nickel in ethanol and acetylacetone mixed solution. The experiments also showed that the precursor of the nanocrystalline NiO prepared by this method can be dissolved in ethanol solution when temperature increase to 40～50 ℃ region.
Metallic nickel was electrochemically dissolved in absolute ethanol and acetylacetone solution in the presence of Bu4NBr(as electronconductive additive). The electrolyte solution containing the precursor was then directly hydrolyzed to obtain nanocrystalline NiO. The precursor was characterized by FTIR、1HNMR、Raman spectra and the nanopowder was characterized by XRD and TEM. The results showed that the NiO powder after hydrolysis was amorphous but formed the cubic NaCl structure when calcined at 350 ℃,the NiO powder have a narrow size distribution of 5～10 nm after annealed at 600 ℃. Characterization of the electrochemical product revealed that Ni(OEt)2(acac)2 was formed by anode dissolution of nickel in ethanol and acetylacetone mixed solution. The experiments also showed that the precursor of the nanocrystalline NiO prepared by this method can be dissolved in ethanol solution when temperature increase to 40～50 ℃ region.
2002, 18(07): 617-623
doi: 10.3866/PKU.WHXB20020710
Abstract:
A ceramic phase Ba12Y4.67Ti8O35 was prepared by solid state reactions,the electrical properties of which were characterised by means of AC impedance spectroscopy,gas concentration cell as well as thermoelectric measurements. The measurements indicate that this material is an oxide ion/hole mixed conductor. At 700 ℃,the bulk conductivity of the material is ～2×10－3Ω－1•cm－1.The impedance data measured at 700 ℃ in air,O2 and N2 atmospheres were analysed by using computer curve fitting,which explains that the ion diffusion impedance is hidden in air and O2 atmospheres because the oxide ion pathway is short circuited by electronic conduction.
A ceramic phase Ba12Y4.67Ti8O35 was prepared by solid state reactions,the electrical properties of which were characterised by means of AC impedance spectroscopy,gas concentration cell as well as thermoelectric measurements. The measurements indicate that this material is an oxide ion/hole mixed conductor. At 700 ℃,the bulk conductivity of the material is ～2×10－3Ω－1•cm－1.The impedance data measured at 700 ℃ in air,O2 and N2 atmospheres were analysed by using computer curve fitting,which explains that the ion diffusion impedance is hidden in air and O2 atmospheres because the oxide ion pathway is short circuited by electronic conduction.
2002, 18(07): 624-628
doi: 10.3866/PKU.WHXB20020711
Abstract:
A new compound (NH4)6•[Ca2(H2O)6(CH3COO)2]•{Ca@[O52(OH)4(CH3COO)2]}•14H2O was prepared and the structure was determined by Xray diffraction analysis. The compound shows an interesting girdlelike structure that is composed of eighteen Mo－O octahedra. There is a Ca2＋ cation in the center of the girdle, which connects to the girdle backbone by bonding to four oxygen atoms of the girdle. The valences of ten Mo atoms are ＋6 while those of the other eight Mo atoms are ＋5, between which Mo－Mo bonds are found. Four acetic ligands connect to the girdle. The girdles link into 1D chains by the Ca2＋ cations above and below the girdle bonding to the backbone oxygen atoms. This compound is triclinic, space group P1, a=1.055 2(2)nm, b=1.515 0(3)nm, c=1.544 9(3)nm, α=60.84(3), β=88.00(3), γ=71.21(3)°, V=2.019 4(7)nm3, R1=0.036 6 and wR2=0.083 3.
A new compound (NH4)6•[Ca2(H2O)6(CH3COO)2]•{Ca@[O52(OH)4(CH3COO)2]}•14H2O was prepared and the structure was determined by Xray diffraction analysis. The compound shows an interesting girdlelike structure that is composed of eighteen Mo－O octahedra. There is a Ca2＋ cation in the center of the girdle, which connects to the girdle backbone by bonding to four oxygen atoms of the girdle. The valences of ten Mo atoms are ＋6 while those of the other eight Mo atoms are ＋5, between which Mo－Mo bonds are found. Four acetic ligands connect to the girdle. The girdles link into 1D chains by the Ca2＋ cations above and below the girdle bonding to the backbone oxygen atoms. This compound is triclinic, space group P1, a=1.055 2(2)nm, b=1.515 0(3)nm, c=1.544 9(3)nm, α=60.84(3), β=88.00(3), γ=71.21(3)°, V=2.019 4(7)nm3, R1=0.036 6 and wR2=0.083 3.
2002, 18(07): 629-632
doi: 10.3866/PKU.WHXB20020712
Abstract:
With QCISD/6311G(3df) and B3LYP/6311＋＋G(3df, 3pd) calculations,stable structure of Ar3H＋ and its vibrational frequencies were calculated. The relation and difference between Ar3H＋ and Ar2H＋ were discussed. A potential curve along a special coordinate was scanned. The methods of twobody, halfthreebody, and threebody interaction were used to divide the fourbody interaction along this potential curve. The best way of dividing the multibody interaction into lowerorder was discussed.
With QCISD/6311G(3df) and B3LYP/6311＋＋G(3df, 3pd) calculations,stable structure of Ar3H＋ and its vibrational frequencies were calculated. The relation and difference between Ar3H＋ and Ar2H＋ were discussed. A potential curve along a special coordinate was scanned. The methods of twobody, halfthreebody, and threebody interaction were used to divide the fourbody interaction along this potential curve. The best way of dividing the multibody interaction into lowerorder was discussed.
2002, 18(07): 633-635
doi: 10.3866/PKU.WHXB20020713
Abstract:
Crystals of K-Pb-Tl-O complex oxides were electrodeposited on the anode from molten salts.The resulting crystals show multilayer structure with resolvable layer thicknesses in nonameters.XPS was used to analyze the crystals and the related compounds.The experimental results indicate that Pb and Tl in K-Pb-Tl-O oxides are in single high valence states.However,their core level binding energies are lower than that of the corresponding low valence non-conducting compounds.This abnormal phenomenon has been explained by using the extra-atomic relaxation effect.In addition,the relationship between the valence electronic structure and the conductivity has been discussed.
Crystals of K-Pb-Tl-O complex oxides were electrodeposited on the anode from molten salts.The resulting crystals show multilayer structure with resolvable layer thicknesses in nonameters.XPS was used to analyze the crystals and the related compounds.The experimental results indicate that Pb and Tl in K-Pb-Tl-O oxides are in single high valence states.However,their core level binding energies are lower than that of the corresponding low valence non-conducting compounds.This abnormal phenomenon has been explained by using the extra-atomic relaxation effect.In addition,the relationship between the valence electronic structure and the conductivity has been discussed.
2002, 18(07): 636-639
doi: 10.3866/PKU.WHXB20020714
Abstract:
Phthaloyl chitosan,an important chitosan derivative,has been used in many fields especially as an intermediate for further modification of chitosan.Several samples with different degree of substitution were synthesized from completely deacetylated chitosan at room temperature.Only amic acid-chitosans were found in these product instead of both amic acid-chitosan and imide-chitosan that were found at ri rous high temperature (more than 130 ℃) as reported by others.XPS was used to measure the degree of substitution.From the measurement,it was shown that the substitution happened at either N atom or O atom of the glucosamine units.As the dosage of phthaloyl anhydride changed,degree of substitution on N atom (dsN) remained almost unchange (0.26±0.03) while degree of substitution on O atom (dsO) varied from 0.01 to 1.54.PhCS can dissolve in several common organic solvents such as DMSO,dichloroacetic acid (DCA),formic acid (FA) etc and forms lyotropic mesophases.Their critical concentrations (c) were determined in some of the above solutions.The dsO showed only slight effects on c.The results were consistent with previous studies on other systems of chitosan derivatives.
Phthaloyl chitosan,an important chitosan derivative,has been used in many fields especially as an intermediate for further modification of chitosan.Several samples with different degree of substitution were synthesized from completely deacetylated chitosan at room temperature.Only amic acid-chitosans were found in these product instead of both amic acid-chitosan and imide-chitosan that were found at ri rous high temperature (more than 130 ℃) as reported by others.XPS was used to measure the degree of substitution.From the measurement,it was shown that the substitution happened at either N atom or O atom of the glucosamine units.As the dosage of phthaloyl anhydride changed,degree of substitution on N atom (dsN) remained almost unchange (0.26±0.03) while degree of substitution on O atom (dsO) varied from 0.01 to 1.54.PhCS can dissolve in several common organic solvents such as DMSO,dichloroacetic acid (DCA),formic acid (FA) etc and forms lyotropic mesophases.Their critical concentrations (c) were determined in some of the above solutions.The dsO showed only slight effects on c.The results were consistent with previous studies on other systems of chitosan derivatives.
2002, 18(07): 640-643
doi: 10.3866/PKU.WHXB20020715
Abstract:
The investigation on charge migration mechanism in double helix DNA is an important current issue extensively studied in the overlapping field of chemistry and biology.We have designed and synthesized a series of supermolecular assemblies of double helix DNA to study charge migration mechanism in DNA by measuring Ap fluorescence and its relative fluorescence quantum yield.Experimentaly,we have distinguished and observed superexchange mechanism of charge transfer in the supermolecular assemblies of double helix DNA,which plays a role in DNA for short distance; but hopping mechanism may be exhibited by the phonon-assisted polaron-like hopping migration.
The investigation on charge migration mechanism in double helix DNA is an important current issue extensively studied in the overlapping field of chemistry and biology.We have designed and synthesized a series of supermolecular assemblies of double helix DNA to study charge migration mechanism in DNA by measuring Ap fluorescence and its relative fluorescence quantum yield.Experimentaly,we have distinguished and observed superexchange mechanism of charge transfer in the supermolecular assemblies of double helix DNA,which plays a role in DNA for short distance; but hopping mechanism may be exhibited by the phonon-assisted polaron-like hopping migration.
2002, 18(07): 644-648
doi: 10.3866/PKU.WHXB20020716
Abstract:
The excess enthalpies of five binary systems of cyclohexanone separately with ethanol,n-propanol,n-butanol,cyclopentanol and cyclohexanol were determined at four different temperatures,293.15,298.15,303.15 and 308.15 K by the MS-80 calorimeter. The experimental excess enthalpies data can all be correlated to smooth equations and the standard deviations were all very small. The coefficients of the correlation equations were offered. It is found that all the excess enthalpies data for all the systems are positive in the range of the experimental concentrations and reach their maximums when the concentrations of alcohols are about 50％. The excess enthalpies data of 2-butanone with alcohols published in previous paper just has the same regularity. The excess enthalpies data increase with the number of carbon atom. It is obvious that excess enthalpies were affected greatly by the mixing temperatures,and the higher the temperatures are, the more the excess enthalpies.
The excess enthalpies of five binary systems of cyclohexanone separately with ethanol,n-propanol,n-butanol,cyclopentanol and cyclohexanol were determined at four different temperatures,293.15,298.15,303.15 and 308.15 K by the MS-80 calorimeter. The experimental excess enthalpies data can all be correlated to smooth equations and the standard deviations were all very small. The coefficients of the correlation equations were offered. It is found that all the excess enthalpies data for all the systems are positive in the range of the experimental concentrations and reach their maximums when the concentrations of alcohols are about 50％. The excess enthalpies data of 2-butanone with alcohols published in previous paper just has the same regularity. The excess enthalpies data increase with the number of carbon atom. It is obvious that excess enthalpies were affected greatly by the mixing temperatures,and the higher the temperatures are, the more the excess enthalpies.
2002, 18(07): 649-652
doi: 10.3866/PKU.WHXB20020717
Abstract:
Absorption and desorption of water vapour in alkyd and polyurethane varnish were studied by quartz crystal microbalance(QCM).The absorption and desorption kinetics curves were Fickian in nature when the relative humidity was higher than 30％,while the solubility followed Henry′s law.The average diffusion coefficient D increases linearly with relative humidity.A residual amount of water(about 10％ of the equilibrium absorption amount under the condition of RH 100％)was found to remain in the coatings after extended exposure to dry air.FTIR analysis showed that the molecular structure of the coatings changed before absorption and after desorption of water vapour.The results showed that the residual water reacted with the coating molecule and H-bond was formed between water molecule and the C=O group.A considerable part of water in the coatings may transport in a chain mode by replacement.The rate of forming H-bond is much faster than that of diffusion.When the relative humidity is higher than 30％,the concentration of the water in the coatings is sufficient to support the reaction; diffusion is the controlling step of the absorption process,so the kinetics is Fickian.When the RH is lower than 30％,the concentration of the water in the coatings is not sufficient to support the reaction; the reaction rate is lowered to the degree that it is comparable to the rate of diffusion,then the kinetics of the whole process begin to deviate from Fick′s law.
Absorption and desorption of water vapour in alkyd and polyurethane varnish were studied by quartz crystal microbalance(QCM).The absorption and desorption kinetics curves were Fickian in nature when the relative humidity was higher than 30％,while the solubility followed Henry′s law.The average diffusion coefficient D increases linearly with relative humidity.A residual amount of water(about 10％ of the equilibrium absorption amount under the condition of RH 100％)was found to remain in the coatings after extended exposure to dry air.FTIR analysis showed that the molecular structure of the coatings changed before absorption and after desorption of water vapour.The results showed that the residual water reacted with the coating molecule and H-bond was formed between water molecule and the C=O group.A considerable part of water in the coatings may transport in a chain mode by replacement.The rate of forming H-bond is much faster than that of diffusion.When the relative humidity is higher than 30％,the concentration of the water in the coatings is sufficient to support the reaction; diffusion is the controlling step of the absorption process,so the kinetics is Fickian.When the RH is lower than 30％,the concentration of the water in the coatings is not sufficient to support the reaction; the reaction rate is lowered to the degree that it is comparable to the rate of diffusion,then the kinetics of the whole process begin to deviate from Fick′s law.
2002, 18(07): 653-656
doi: 10.3866/PKU.WHXB20020718
Abstract:
Polyaniline-barium titanate (PAn/BaTiO3) nanocomposite particles have been prepared by in situ composite technique in the presence of barium titanate nanoparticles which are synthesized by sol-gel processing.The conformation,structure and thermal properties of PAn/BaTiO3 nanocomposites particles are characterized by TEM,XRD,FT-IR ,XPS and TG.The results show that the BaTiO3 nanoparticles with diameter of about 40 nm are dispersed in polyaniline,while the diameter of the composite particles is about 1 μm.There are chemical bonds between PAn and BaTiO3 in PAn/BaTiO3 nanocomposites , at the same time,the complex can reduce the agglomeration of BaTiO3 particles to some extent.
Polyaniline-barium titanate (PAn/BaTiO3) nanocomposite particles have been prepared by in situ composite technique in the presence of barium titanate nanoparticles which are synthesized by sol-gel processing.The conformation,structure and thermal properties of PAn/BaTiO3 nanocomposites particles are characterized by TEM,XRD,FT-IR ,XPS and TG.The results show that the BaTiO3 nanoparticles with diameter of about 40 nm are dispersed in polyaniline,while the diameter of the composite particles is about 1 μm.There are chemical bonds between PAn and BaTiO3 in PAn/BaTiO3 nanocomposites , at the same time,the complex can reduce the agglomeration of BaTiO3 particles to some extent.
2002, 18(07): 657-660
doi: 10.3866/PKU.WHXB20020719
Abstract:
A new model based on the concept of local composition has been proposed for the correlation of the NMR chemical shift data. Consequently, the viscosity and NMR chemical shift data were well correlated simultaneously using this model and the early proposed local composition viscosity equation. The resulting average absolute deviations of viscosity and NMR chemical shift are respectively less than 0.0006 mPa•s and 0.0072, which suggested the reasonability of the proposed model.
A new model based on the concept of local composition has been proposed for the correlation of the NMR chemical shift data. Consequently, the viscosity and NMR chemical shift data were well correlated simultaneously using this model and the early proposed local composition viscosity equation. The resulting average absolute deviations of viscosity and NMR chemical shift are respectively less than 0.0006 mPa•s and 0.0072, which suggested the reasonability of the proposed model.
2002, 18(07): 661-664
doi: 10.3866/PKU.WHXB20020720
Abstract:
The stability of microemulsion at low temperature is one of the technical indices of microemulsion quality. The major factors affect the stability at low temperature are organic solvents, surfactants, cosolvent and water quality. In this paper, three formulated microemulsions were studied,namely, 2.5％ imidacloprid ME, 5％ diniconazole ME and 10％ pyridaben ME. It was found that there is at least one break point or organic solvent concentration above which a pesticide could be solved stably in the organic solvent and the stability of the system could be prolonged at low temperature. However, one should keep in mind that minimum use of organic solvent will benefit the environmental protection. The concentration and the balance of the hydrophilicity and lipophilicity of the added surfactants in the system play a key role on the stability of agrochemical microemulsions.
The stability of microemulsion at low temperature is one of the technical indices of microemulsion quality. The major factors affect the stability at low temperature are organic solvents, surfactants, cosolvent and water quality. In this paper, three formulated microemulsions were studied,namely, 2.5％ imidacloprid ME, 5％ diniconazole ME and 10％ pyridaben ME. It was found that there is at least one break point or organic solvent concentration above which a pesticide could be solved stably in the organic solvent and the stability of the system could be prolonged at low temperature. However, one should keep in mind that minimum use of organic solvent will benefit the environmental protection. The concentration and the balance of the hydrophilicity and lipophilicity of the added surfactants in the system play a key role on the stability of agrochemical microemulsions.
2002, 18(07): 665-668
doi: 10.3866/PKU.WHXB20020721
Abstract:
Initial stages of electrodeposition of copper on glassy carbon electrode from 0.8 mol•L－1 copper sulphate electrolyte solution containing 2.0×10－2 mol•L－1 nicotinic acid are studied using cyclic voltammetry and chronoamperometry.The results show that nicotinic acid (NA) produces an inhibition of copper deposition,probably related to the adsorption of nicotinic acid.The initial deposition kinetics corresponds to a model including instantaneous nucleation and diffusion controlled growth.The X-ray diffraction results indicate that copper deposits exhibit face-centered cubic structure and (220) highly preferred orientation.Nicotinic acid produces uniform and smooth surfaces of copper deposit.
Initial stages of electrodeposition of copper on glassy carbon electrode from 0.8 mol•L－1 copper sulphate electrolyte solution containing 2.0×10－2 mol•L－1 nicotinic acid are studied using cyclic voltammetry and chronoamperometry.The results show that nicotinic acid (NA) produces an inhibition of copper deposition,probably related to the adsorption of nicotinic acid.The initial deposition kinetics corresponds to a model including instantaneous nucleation and diffusion controlled growth.The X-ray diffraction results indicate that copper deposits exhibit face-centered cubic structure and (220) highly preferred orientation.Nicotinic acid produces uniform and smooth surfaces of copper deposit.
2002, 18(07): 669-672
doi: 10.3866/PKU.WHXB20020722
Abstract:
Low surface free energy and ultrathin film of Perfluoroctanoxamidepropyltrimethoxyl Silane SAM was fabricated on microscope slide substrate by molecular self-assembled process.Contact angle measurement and XPS analysis show that the SAM has been prepared successfully with the property of water and oil repellency.The results of the friction and wear test show that this SAM can decrease the friction coefficient of the substrate significantly.
Low surface free energy and ultrathin film of Perfluoroctanoxamidepropyltrimethoxyl Silane SAM was fabricated on microscope slide substrate by molecular self-assembled process.Contact angle measurement and XPS analysis show that the SAM has been prepared successfully with the property of water and oil repellency.The results of the friction and wear test show that this SAM can decrease the friction coefficient of the substrate significantly.
