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2005 Volume 21 Issue 1
2005, 21(01): 1-5
doi: 10.3866/PKU.WHXB20050101
Abstract:
Molar heat capacities of (S)-ibuprofen were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 80 to 370 K. Experimental heat capacities were fitted into a polynomial equation of heat capacities (Cp,m) with reduced temperature (X), [X=f(T)]. The polynomial equations for (S)-ibuprofen wereCp,m(S)= －39.483X4－66.649X3＋95.196X2＋210.84X＋172.98 in solid state and Cp,m(L)= 7.191X3＋4.2774X2＋56.365X＋498.5 in liquid state. The thermodynamic functions relative to the reference temperature of 298.15 K, HT－H298.15 and ST－S298.15, were derived for the(S)-ibuprofen. A fusion transition at Tm=(324.15±0.02) K was found from the Cp－T curve. The molar enthalpy and entropy of the fusion transition were determined to be (18.05±0.31) kJ•mol－1 and (55.71±0.95) J•mol－1•K－1, respectively. The purity of the (S)-ibuprofen was determined to be 99.44％ on the basis of the heat capacity measurement. Finally, the heat capacities of (S)-ibuprofen and racemic ibuprofen were compared.
Molar heat capacities of (S)-ibuprofen were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 80 to 370 K. Experimental heat capacities were fitted into a polynomial equation of heat capacities (Cp,m) with reduced temperature (X), [X=f(T)]. The polynomial equations for (S)-ibuprofen wereCp,m(S)= －39.483X4－66.649X3＋95.196X2＋210.84X＋172.98 in solid state and Cp,m(L)= 7.191X3＋4.2774X2＋56.365X＋498.5 in liquid state. The thermodynamic functions relative to the reference temperature of 298.15 K, HT－H298.15 and ST－S298.15, were derived for the(S)-ibuprofen. A fusion transition at Tm=(324.15±0.02) K was found from the Cp－T curve. The molar enthalpy and entropy of the fusion transition were determined to be (18.05±0.31) kJ•mol－1 and (55.71±0.95) J•mol－1•K－1, respectively. The purity of the (S)-ibuprofen was determined to be 99.44％ on the basis of the heat capacity measurement. Finally, the heat capacities of (S)-ibuprofen and racemic ibuprofen were compared.
2005, 21(01): 6-9
doi: 10.3866/PKU.WHXB20050102
Abstract:
With increasing the number of oxyethylene groups in the spacer of [C12H25N＋(CH3)2]2C2H4(OC2H4)n•2Br－(C12-2-En-C12•2Br, n=2,3), the homogeneous regions in the phase diagrams of aqueous mixture of C12-2-En-C12•2Br with C12H25SO4Na (SDS) expand obviously in comparison with that of [C12H25N＋(CH3)2CH2]2•2Br－/SDS mixed system. There exists a synergism between C12-2-En-C12•2Br and SDS during the mixed micellization. The minimum critical micelle concentration (cmcT,min) in the homogeneous region is 0.0339 mmol•L－1 and the corresponding molar fraction (x2*) of SDS in the bulk solution is 0.447 estimated by Rosen theory. At x2=0.5, the corresponding molar fraction (x2M) in the mixed micelle and the total aggregation number (NT) are 0.43 and 36 respectively.
With increasing the number of oxyethylene groups in the spacer of [C12H25N＋(CH3)2]2C2H4(OC2H4)n•2Br－(C12-2-En-C12•2Br, n=2,3), the homogeneous regions in the phase diagrams of aqueous mixture of C12-2-En-C12•2Br with C12H25SO4Na (SDS) expand obviously in comparison with that of [C12H25N＋(CH3)2CH2]2•2Br－/SDS mixed system. There exists a synergism between C12-2-En-C12•2Br and SDS during the mixed micellization. The minimum critical micelle concentration (cmcT,min) in the homogeneous region is 0.0339 mmol•L－1 and the corresponding molar fraction (x2*) of SDS in the bulk solution is 0.447 estimated by Rosen theory. At x2=0.5, the corresponding molar fraction (x2M) in the mixed micelle and the total aggregation number (NT) are 0.43 and 36 respectively.
2005, 21(01): 10-15
doi: 10.3866/PKU.WHXB20050103
Abstract:
Ga2O3-NiO Complex Oxide gas-sensing materials were prepared by sol-gel method. Effects of heat-treatment temperature and different n(Ni2＋) : n(Ga3＋) ratios on the phase constituents were characterized by XRD, IR and ICP, respectively. The conductance-temperature and gas-sensing properties of Ga2O3-NiO were investigated. The results demonstrate that pure phase NiGa2O4 can be obtained when the ratio of Ni2＋ to Ga3＋(n(Ni2＋) : n(Ga3＋)) is 0.7～0.9 : 2 and heat-treatment is carried out at 800 ℃ for 4 hours. Because of the reaction GaNi×→GaNi’＋h●, NiGa2O4 is a p-type semiconductor and exhibits high sensitivity and od selectivity to C2H5OH.
Ga2O3-NiO Complex Oxide gas-sensing materials were prepared by sol-gel method. Effects of heat-treatment temperature and different n(Ni2＋) : n(Ga3＋) ratios on the phase constituents were characterized by XRD, IR and ICP, respectively. The conductance-temperature and gas-sensing properties of Ga2O3-NiO were investigated. The results demonstrate that pure phase NiGa2O4 can be obtained when the ratio of Ni2＋ to Ga3＋(n(Ni2＋) : n(Ga3＋)) is 0.7～0.9 : 2 and heat-treatment is carried out at 800 ℃ for 4 hours. Because of the reaction GaNi×→GaNi’＋h●, NiGa2O4 is a p-type semiconductor and exhibits high sensitivity and od selectivity to C2H5OH.
2005, 21(01): 16-21
doi: 10.3866/PKU.WHXB20050104
Abstract:
The absorption optical spectra of poly(p-phenylene-2,6-benzo bisoxazole) (PBO) in MSA(methanesulfonic acid) solution was similar with that in film. The UV spectra of the polymers were red-shifted from the theoretical UV spectra calculated with AM/ZINDO-CI. The results of quantum calculation on the model of protonated PBO and the aggregation PBO indicated that the red-shift were attributed to the effects of protonation or intermolecular interactions. The absorption spectrum of protonated PBO calculated with AM1/ZINDO accorded with the experimental optical absorption of PBO in MSA solution.
The absorption optical spectra of poly(p-phenylene-2,6-benzo bisoxazole) (PBO) in MSA(methanesulfonic acid) solution was similar with that in film. The UV spectra of the polymers were red-shifted from the theoretical UV spectra calculated with AM/ZINDO-CI. The results of quantum calculation on the model of protonated PBO and the aggregation PBO indicated that the red-shift were attributed to the effects of protonation or intermolecular interactions. The absorption spectrum of protonated PBO calculated with AM1/ZINDO accorded with the experimental optical absorption of PBO in MSA solution.
2005, 21(01): 22-27
doi: 10.3866/PKU.WHXB20050105
Abstract:
Molecular recognition properties of three novel molecular tweezers as receptors have been investigated using diphenyl ketone and aromatic diamines. The association constants (Ka) and Gibbs free energy changes (ΔG0) have been measured by UV-visible spectroscopic titration on the complexes of these molecular tweezers with some aromatic diamines and diphenyl ketone. The results show that the supramolecular complexes formed between the tweezers and various substrates consist of 1:1 host and guest molecules. The molecular recognition ability of the receptors for diphenyl ketone and aromatic diamines is discussed in terms of size/shape-fit, complementary geometrical relationship, and the weak intermolecular forces. 1H NMR spectroscopy and computer-aided studies have been employed to elucidate the binding behavior of these molecular tweezers. Molecular modeling and 1H NMR spectroscopy studies suggest that the multiple π-π stacking and van der Waals interaction may be the main driving forces in molecular recognition. The size/shape-fit and geometyical complementary relationship between the receptor and the substrate play a pivotal role in the inclusion complextion of these guests with the molecular tweezers.
Molecular recognition properties of three novel molecular tweezers as receptors have been investigated using diphenyl ketone and aromatic diamines. The association constants (Ka) and Gibbs free energy changes (ΔG0) have been measured by UV-visible spectroscopic titration on the complexes of these molecular tweezers with some aromatic diamines and diphenyl ketone. The results show that the supramolecular complexes formed between the tweezers and various substrates consist of 1:1 host and guest molecules. The molecular recognition ability of the receptors for diphenyl ketone and aromatic diamines is discussed in terms of size/shape-fit, complementary geometrical relationship, and the weak intermolecular forces. 1H NMR spectroscopy and computer-aided studies have been employed to elucidate the binding behavior of these molecular tweezers. Molecular modeling and 1H NMR spectroscopy studies suggest that the multiple π-π stacking and van der Waals interaction may be the main driving forces in molecular recognition. The size/shape-fit and geometyical complementary relationship between the receptor and the substrate play a pivotal role in the inclusion complextion of these guests with the molecular tweezers.
2005, 21(01): 28-32
doi: 10.3866/PKU.WHXB20050106
Abstract:
The quantitative structure-activity relationship(QSAR) of indolo[1,2-b] quinazoline derivatives, in regard to their antitumor activity, was systematically studied using the density functional theory(DFT), molecular mechanism (MM＋) and regression analysis methods. via a stepwise regression analysis, some main independent factors affecting the activity of the compounds were selected out, and then the QSAR equation was established. It has been found that the energy difference (ΔεL-H) between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) of the compound, the hydrophobic parameter (lgP) of the molecule, as well as the total net charge (ΣQD) of the D-ring skeleton and the net charge(QFR1) of the first atom of the substituent R1 on D-ring are the main independent factors contributing to the antitumor activity of the compound. The cross-validation rcv2 and the fitting correlation coefficient r2 for the model established by this study are 0.7364 and 0.8505, respectively. The results suggest that this model has od predictability and further indicate that the LUMO energy closely relative to ΔεL-H and the conjugative planarity area play a very important role in the DNA-binding and the activity of the compounds. Therefore, some higher antitumor active compounds can be designed prior to their synthesis via selecting some substituents (R1), which have stronger electron-withdrawing ability and can form greater conjugative planarity area with the skeletons of the series of the compounds.
The quantitative structure-activity relationship(QSAR) of indolo[1,2-b] quinazoline derivatives, in regard to their antitumor activity, was systematically studied using the density functional theory(DFT), molecular mechanism (MM＋) and regression analysis methods. via a stepwise regression analysis, some main independent factors affecting the activity of the compounds were selected out, and then the QSAR equation was established. It has been found that the energy difference (ΔεL-H) between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) of the compound, the hydrophobic parameter (lgP) of the molecule, as well as the total net charge (ΣQD) of the D-ring skeleton and the net charge(QFR1) of the first atom of the substituent R1 on D-ring are the main independent factors contributing to the antitumor activity of the compound. The cross-validation rcv2 and the fitting correlation coefficient r2 for the model established by this study are 0.7364 and 0.8505, respectively. The results suggest that this model has od predictability and further indicate that the LUMO energy closely relative to ΔεL-H and the conjugative planarity area play a very important role in the DNA-binding and the activity of the compounds. Therefore, some higher antitumor active compounds can be designed prior to their synthesis via selecting some substituents (R1), which have stronger electron-withdrawing ability and can form greater conjugative planarity area with the skeletons of the series of the compounds.
2005, 21(01): 33-37
doi: 10.3866/PKU.WHXB20050107
Abstract:
By analyzing the X-ray absorption spectra of Ti K edge, the structural information of TiO2-SiO2 composite oxides prepared by sol-gel (CTS1, CTS4), impregnation (SYB02, SYB04, SYB06), and CVD (CVD1, CVD2)methods were obtained.TiO2 was most dispersed in SiO2 by the sol-gel method and TiO2 was least dispersed in SiO2 by the CVD method. The pre-edge structure of anatase (Ti K edge of XAFS) is characteristic of three peaks: A1, A2, and A3. For the sol-gel and impregnation prepared TiO2-SiO2 supports, the structure of Ti K edge is different from that of anatase. The intensity of A2 peak increases with the decrease of the content of Ti, and coordination numbers of the first shell of Ti－O increase with the increase of the content of Ti. The pre-edge absorption feature of TiO2-SiO2 prepared by CVD is consistent with that of anatase, and the coordination number of the first shell is nearly to 6. The bond lengths of the first shell of Ti－O increase with the increasing Ti content. The results were confirmed by further measurement using XRD. Based on the experimental results, a model of titania-silica composite oxide was proposed.
By analyzing the X-ray absorption spectra of Ti K edge, the structural information of TiO2-SiO2 composite oxides prepared by sol-gel (CTS1, CTS4), impregnation (SYB02, SYB04, SYB06), and CVD (CVD1, CVD2)methods were obtained.TiO2 was most dispersed in SiO2 by the sol-gel method and TiO2 was least dispersed in SiO2 by the CVD method. The pre-edge structure of anatase (Ti K edge of XAFS) is characteristic of three peaks: A1, A2, and A3. For the sol-gel and impregnation prepared TiO2-SiO2 supports, the structure of Ti K edge is different from that of anatase. The intensity of A2 peak increases with the decrease of the content of Ti, and coordination numbers of the first shell of Ti－O increase with the increase of the content of Ti. The pre-edge absorption feature of TiO2-SiO2 prepared by CVD is consistent with that of anatase, and the coordination number of the first shell is nearly to 6. The bond lengths of the first shell of Ti－O increase with the increasing Ti content. The results were confirmed by further measurement using XRD. Based on the experimental results, a model of titania-silica composite oxide was proposed.
2005, 21(01): 38-41
doi: 10.3866/PKU.WHXB20050108
Abstract:
The interaction between N, N-diethylaniline (DEA) and SDS/n-C5H11OH/H2O microemulsion was investigated by cyclic voltammetric method. DEA has two oxidation peaks in both O/W and W/O microemulsions, and the potential difference is only about 0.099 V between the two peaks ( Table 1, Fig.2).Since the energy needed for the radical cation DEA＋● losing an electron to form DEA2＋ is about 0.50 V (E(DEA /DEA＋●)－E(DEA＋●/DEA)≈0.50 V),the two peaks are both produced by DEA molecule losing an electron to form DEA＋●. The results indicate that DEA molecules can reside in the membrane phase of O/W and W/O microemulsion droplets with two ways. Some of them are located in the membrane phase of microemulsion near to the polar head of surfactant and cosurfactant, and others are located in the side of the hydrophobic tail of the surfactant. The distribution between the two locations depends on the structures and compositions of the microemulsions.
The interaction between N, N-diethylaniline (DEA) and SDS/n-C5H11OH/H2O microemulsion was investigated by cyclic voltammetric method. DEA has two oxidation peaks in both O/W and W/O microemulsions, and the potential difference is only about 0.099 V between the two peaks ( Table 1, Fig.2).Since the energy needed for the radical cation DEA＋● losing an electron to form DEA2＋ is about 0.50 V (E(DEA /DEA＋●)－E(DEA＋●/DEA)≈0.50 V),the two peaks are both produced by DEA molecule losing an electron to form DEA＋●. The results indicate that DEA molecules can reside in the membrane phase of O/W and W/O microemulsion droplets with two ways. Some of them are located in the membrane phase of microemulsion near to the polar head of surfactant and cosurfactant, and others are located in the side of the hydrophobic tail of the surfactant. The distribution between the two locations depends on the structures and compositions of the microemulsions.
2005, 21(01): 42-46
doi: 10.3866/PKU.WHXB20050109
Abstract:
The physical meanings and affecting factors of the optimal phase are analyzed and validated systematically in the measurement of surface photovoltage spectroscopy (SPS) based on Lock-In amplifier. Taking the example of p silicon, under different modulation frequencies the measured data of the optimal phase were in agreement with the theoretical analysis, which shows that for the usual metal-insulator-semiconductor (MIS) “sandwich” structure, the equivalent impedance can greatly affect the optimal phase. In the case of bulk materials, the optimal phase only correlates with experimental conductions. But for nanomaterials, the equivalent resistance and capacitance (Rins and Cins) of MIS structure vary under illumination that will result in great changes in the optimal phase. Because Rins and Cins are related to the characters of nanomaterials, the optimal phase may offer a new method for the measurement of photo-electric properties of nanomaterials.
The physical meanings and affecting factors of the optimal phase are analyzed and validated systematically in the measurement of surface photovoltage spectroscopy (SPS) based on Lock-In amplifier. Taking the example of p silicon, under different modulation frequencies the measured data of the optimal phase were in agreement with the theoretical analysis, which shows that for the usual metal-insulator-semiconductor (MIS) “sandwich” structure, the equivalent impedance can greatly affect the optimal phase. In the case of bulk materials, the optimal phase only correlates with experimental conductions. But for nanomaterials, the equivalent resistance and capacitance (Rins and Cins) of MIS structure vary under illumination that will result in great changes in the optimal phase. Because Rins and Cins are related to the characters of nanomaterials, the optimal phase may offer a new method for the measurement of photo-electric properties of nanomaterials.
2005, 21(01): 47-51
doi: 10.3866/PKU.WHXB20050110
Abstract:
Quasi-one-dimensional microstructures of metal-organic complex Ag(TCNQ) were prepared by chemical solution reaction method. The obtained Ag(TCNQ) samples were characterized as crystalline state by XRD.SEM observation showed that Ag(TCNQ) was quasi -one-dimensional micro tube or wire. Raman measurement showed that complete charge transfer occurred between Ag atom and TCNQ molecule during the formation of Ag(TCNQ) single microstructure. The effects of thickness of Ag films and reaction time on the formation of quasi-one-dimensional microstructure of Ag(TCNQ) were studied. The results show that the thinner the Ag film is, the sparser the Ag(TCNQ) microstructures is obtained. The changes of morphologies for different reaction time indicate that the reaction under es three stages, i.e. formation and growth of crystals, complete reaction, and dissolving, orderly.
Quasi-one-dimensional microstructures of metal-organic complex Ag(TCNQ) were prepared by chemical solution reaction method. The obtained Ag(TCNQ) samples were characterized as crystalline state by XRD.SEM observation showed that Ag(TCNQ) was quasi -one-dimensional micro tube or wire. Raman measurement showed that complete charge transfer occurred between Ag atom and TCNQ molecule during the formation of Ag(TCNQ) single microstructure. The effects of thickness of Ag films and reaction time on the formation of quasi-one-dimensional microstructure of Ag(TCNQ) were studied. The results show that the thinner the Ag film is, the sparser the Ag(TCNQ) microstructures is obtained. The changes of morphologies for different reaction time indicate that the reaction under es three stages, i.e. formation and growth of crystals, complete reaction, and dissolving, orderly.
2005, 21(01): 52-56
doi: 10.3866/PKU.WHXB20050111
Abstract:
The hydrogen bond structure and interaction energy on the ground state of pyridazine and water complex have been studied by the B3LYP and MP2 methods. All calculations show that there are strong interactions in the N…H－O hydrogen bond and there are large red-shifts for the symmetric H－O stretching vibrational frequencies in the pyridazine and water complex. The low-lying singlet 1(n,π*) and 1(π,π*) vertical excitations of the monomer pyridazine and the hydrogen bond between the pyridazine and water molecules have been investigated by the time-dependent density functional theory TDB3LYP method.
The hydrogen bond structure and interaction energy on the ground state of pyridazine and water complex have been studied by the B3LYP and MP2 methods. All calculations show that there are strong interactions in the N…H－O hydrogen bond and there are large red-shifts for the symmetric H－O stretching vibrational frequencies in the pyridazine and water complex. The low-lying singlet 1(n,π*) and 1(π,π*) vertical excitations of the monomer pyridazine and the hydrogen bond between the pyridazine and water molecules have been investigated by the time-dependent density functional theory TDB3LYP method.
2005, 21(01): 57-62
doi: 10.3866/PKU.WHXB20050112
Abstract:
Highly dispersed TiO2 nanometer powders with controlled structure were synthesized by chemical complex sol-gel auto-igniting process. The initial oxidant/reductant molar ratio, swelling of gel and temperature schedule were chosen as key variables for the controlled synthesis: by changing the initial oxidant/reductant molar ratio from 2 to 7, TiO2 having a particle size about 30 nm was obtained at 600 ℃ with a mass fraction of rutile ranging from 25％ to 68.2％; sufficient swelling and carbonizing of the gels at 150 ℃ removed non-bridging hydroxyl groups and broke down the hydrogen bonds between particles, so the formation of hard agglomerates was avoided; the mass fraction of rutile and particle size of TiO2 increased with increasing of calcination temperature; agglomerates of TiO2 were formed at 800 ℃. The optical absorption edges significantly shifted to longer wavelengths in the UV-Vis diffuse reflectance spectra of the as-prepared TiO2, and the reflectivity was about 10％ lower than that of commercial TiO2. It was found that the as-prepared TiO2 with the optimal rutile fraction of 55.5％ achieved the best optical absorption.
Highly dispersed TiO2 nanometer powders with controlled structure were synthesized by chemical complex sol-gel auto-igniting process. The initial oxidant/reductant molar ratio, swelling of gel and temperature schedule were chosen as key variables for the controlled synthesis: by changing the initial oxidant/reductant molar ratio from 2 to 7, TiO2 having a particle size about 30 nm was obtained at 600 ℃ with a mass fraction of rutile ranging from 25％ to 68.2％; sufficient swelling and carbonizing of the gels at 150 ℃ removed non-bridging hydroxyl groups and broke down the hydrogen bonds between particles, so the formation of hard agglomerates was avoided; the mass fraction of rutile and particle size of TiO2 increased with increasing of calcination temperature; agglomerates of TiO2 were formed at 800 ℃. The optical absorption edges significantly shifted to longer wavelengths in the UV-Vis diffuse reflectance spectra of the as-prepared TiO2, and the reflectivity was about 10％ lower than that of commercial TiO2. It was found that the as-prepared TiO2 with the optimal rutile fraction of 55.5％ achieved the best optical absorption.
2005, 21(01): 63-68
doi: 10.3866/PKU.WHXB20050113
Abstract:
The structural and diffusion properties of water confined in hydrophobic micropores were studied by means of molecular dynamics (MD) simulations. The effects of pore width, temperature, and pressure on density distribution in the channel direction and on self-diffusion coefficient were investigated and analyzed, and the radial distribution functions of water in micropores at different temperatures were calculated. In small-size micropores, the distribution of water molecules along the channel direction becomes very inhomogeneous as the temperature decreases, which leads to gas-liquid phase separation. The diffusivity in the direction parallel with the channel is generally 4～5 times larger than those in the direction perpendicular to the channel. Finally, a model was proposed to describe the diffusivity of water in micropores as a function of temperature and density.
The structural and diffusion properties of water confined in hydrophobic micropores were studied by means of molecular dynamics (MD) simulations. The effects of pore width, temperature, and pressure on density distribution in the channel direction and on self-diffusion coefficient were investigated and analyzed, and the radial distribution functions of water in micropores at different temperatures were calculated. In small-size micropores, the distribution of water molecules along the channel direction becomes very inhomogeneous as the temperature decreases, which leads to gas-liquid phase separation. The diffusivity in the direction parallel with the channel is generally 4～5 times larger than those in the direction perpendicular to the channel. Finally, a model was proposed to describe the diffusivity of water in micropores as a function of temperature and density.
2005, 21(01): 69-73
doi: 10.3866/PKU.WHXB20050114
Abstract:
TiO2 and TiO2-SiO2 thin films were prepared at low-temperature with hot water treatment. Their crystal structure, surface morphology and transparency were characterized by XRD, AFM and UV-Vis spectra respectively, and the effects of addition of SiO2 in the films on their performances after treatment with hot water were analyzed. The evaluations of photocatalytic activities of thin films were carried out by degradation of rhodamine B in water solution under UV irradiation. The results showed that the thin films prepared at low temperature with hot water treatment have high reactivity for degradation of rhodamine B and the addition of SiO2 can significantly increase the photocatalytic reactivitity.
TiO2 and TiO2-SiO2 thin films were prepared at low-temperature with hot water treatment. Their crystal structure, surface morphology and transparency were characterized by XRD, AFM and UV-Vis spectra respectively, and the effects of addition of SiO2 in the films on their performances after treatment with hot water were analyzed. The evaluations of photocatalytic activities of thin films were carried out by degradation of rhodamine B in water solution under UV irradiation. The results showed that the thin films prepared at low temperature with hot water treatment have high reactivity for degradation of rhodamine B and the addition of SiO2 can significantly increase the photocatalytic reactivitity.
2005, 21(01): 74-78
doi: 10.3866/PKU.WHXB20050115
Abstract:
Core-shell Au-Pt nanoparticles were synthesized by chemical reduction method. The mean diameter of the nanoparticles was determined to be 27 nm by transmission electron microscope (TEM). The prepared nanoparticles were characterized by ultraviolet-visible (UV-Vis) and infrared transmission spectroscopy. The disappearance of the characteristic peak near 520 nm of Au nanoparticles in UV-Vis spectroscopy confirmed the formation of the core-shell structure. Using infrared transmission spectroscopy, the geminal CO adsorbates that yielded a doublet IR band at around 2110 cm－1 and 2063 cm－1 on core-shell Au-Pt nanoparticles were detected for the first time. The core-shell Au-Pt nanoparticles supported on GC (glassy carbon) substrate as electrode exhibited od electrocatalytic properties for the oxidation of adsorbed CO (COad) species. The onset and peak potentials of COad oxidation were negatively shifted 0.45 and 0.11 V, respectively, in referring to the values measured on a bulk Pt electrode.
Core-shell Au-Pt nanoparticles were synthesized by chemical reduction method. The mean diameter of the nanoparticles was determined to be 27 nm by transmission electron microscope (TEM). The prepared nanoparticles were characterized by ultraviolet-visible (UV-Vis) and infrared transmission spectroscopy. The disappearance of the characteristic peak near 520 nm of Au nanoparticles in UV-Vis spectroscopy confirmed the formation of the core-shell structure. Using infrared transmission spectroscopy, the geminal CO adsorbates that yielded a doublet IR band at around 2110 cm－1 and 2063 cm－1 on core-shell Au-Pt nanoparticles were detected for the first time. The core-shell Au-Pt nanoparticles supported on GC (glassy carbon) substrate as electrode exhibited od electrocatalytic properties for the oxidation of adsorbed CO (COad) species. The onset and peak potentials of COad oxidation were negatively shifted 0.45 and 0.11 V, respectively, in referring to the values measured on a bulk Pt electrode.
2005, 21(01): 79-83
doi: 10.3866/PKU.WHXB20050116
Abstract:
The effect of alumina sol on the α phase transformation in γ-alumina powder has been studied. In comparison with α-alumina seeds, the alumina sol can also act as seeds. Moreover, because of the small particle size and perfect dispersibility of the alumina sol, the α phase transformation temperature is decreased and, meanwhile, the microstructure of the produced powders is modified. So ultrafined powders with a particle size less than 100 nm were produced with od dispersibility. The α phase transformation of the alumina precursors with alumina sol doping was studied on the base of the TEM photographs of the produced powders.
The effect of alumina sol on the α phase transformation in γ-alumina powder has been studied. In comparison with α-alumina seeds, the alumina sol can also act as seeds. Moreover, because of the small particle size and perfect dispersibility of the alumina sol, the α phase transformation temperature is decreased and, meanwhile, the microstructure of the produced powders is modified. So ultrafined powders with a particle size less than 100 nm were produced with od dispersibility. The α phase transformation of the alumina precursors with alumina sol doping was studied on the base of the TEM photographs of the produced powders.
2005, 21(01): 84-88
doi: 10.3866/PKU.WHXB20050117
Abstract:
SrTiO3 powder with high crystal perfection was synthesized by solid-state reaction of strontium nitrate with TiO(OH)2 formed by hydrolysis of tetra-butoxy titanium in the presence of alkali metal compound mineralizer. Then a photocatalyst, CoO/SrTiO3, was prepared by impregnation method. The effect of the mineralezers is decreased in the following order :KOH > NaOH > NaNO3 > KNO3.The photocatalytic activity of CoO/SrTiO3,was increased for ca.8 times when KOH mineralizer was added, with the irradiation of 400 W high-pressure mercury lamp, the hydrogen-generation rate amounts to 480 μmol•g cat－1•h－1 over the CoO/SrTiO3,catalyst.Characterization results from SEM and UV-Vis diffuse reflection spectra analysis show that the solid-state reaction for synthesizing SrTiO3 proceeds completely and the crystal perfection of SrTiO3 is improved by adding KOH mineralizer. The suitable amount of KOH is 2.0％(w).
SrTiO3 powder with high crystal perfection was synthesized by solid-state reaction of strontium nitrate with TiO(OH)2 formed by hydrolysis of tetra-butoxy titanium in the presence of alkali metal compound mineralizer. Then a photocatalyst, CoO/SrTiO3, was prepared by impregnation method. The effect of the mineralezers is decreased in the following order :KOH > NaOH > NaNO3 > KNO3.The photocatalytic activity of CoO/SrTiO3,was increased for ca.8 times when KOH mineralizer was added, with the irradiation of 400 W high-pressure mercury lamp, the hydrogen-generation rate amounts to 480 μmol•g cat－1•h－1 over the CoO/SrTiO3,catalyst.Characterization results from SEM and UV-Vis diffuse reflection spectra analysis show that the solid-state reaction for synthesizing SrTiO3 proceeds completely and the crystal perfection of SrTiO3 is improved by adding KOH mineralizer. The suitable amount of KOH is 2.0％(w).
2005, 21(01): 89-92
doi: 10.3866/PKU.WHXB20050118
Abstract:
Modified spinel lithium manganate with zirconium doped LiMn2－xZrxO4 (x= 0, 0.01, 0.02, 0.04, 0.06, 0.08, 0.10) used for cathode of lithium-ion batteries was prepared by solid-state method. The structure and morphology of as-prepared cathode materials were characterized by XRD and ESEM (environment scanning electron micrograph). The effects of the zirconium doping on improving the performances of spinel materials were analyzed in terms of the crystal structure, charge-discharge curves and cycle performances. The results showed that the modified materials had better cycle performances without significant degradation of capacity when the doping value x was less than 0.06,and LiMn1.98Zr0.02O4 was the best compound with a capacity of 113.8 mA•h•g－1 after 50 cycles.
Modified spinel lithium manganate with zirconium doped LiMn2－xZrxO4 (x= 0, 0.01, 0.02, 0.04, 0.06, 0.08, 0.10) used for cathode of lithium-ion batteries was prepared by solid-state method. The structure and morphology of as-prepared cathode materials were characterized by XRD and ESEM (environment scanning electron micrograph). The effects of the zirconium doping on improving the performances of spinel materials were analyzed in terms of the crystal structure, charge-discharge curves and cycle performances. The results showed that the modified materials had better cycle performances without significant degradation of capacity when the doping value x was less than 0.06,and LiMn1.98Zr0.02O4 was the best compound with a capacity of 113.8 mA•h•g－1 after 50 cycles.
2005, 21(01): 93-97
doi: 10.3866/PKU.WHXB20050119
Abstract:
The mathematical model of a three-parameter method, based on an integral formulation, for analyzing the coulostatically induced transients is developed. This method can compute the Tafel slopes ba or bc and corrosion current density ic. The validity of the method is confirmed by the observation that the values of Tafel slope measured by coulostatic method are coincident with those obtained by Tafel lines extrapolation method with eliminating influence of IR drop, and the comparison of results obtained by solution analysis and electrochemical measurements shows that the method provides a faithful representation of corrosion behavior. The integral method has the advantages over differential method due to its simplicity and higher signal/noise ratio, so that the numerical al rithm gives the possibility of higher precision of corrosion measurements.
The mathematical model of a three-parameter method, based on an integral formulation, for analyzing the coulostatically induced transients is developed. This method can compute the Tafel slopes ba or bc and corrosion current density ic. The validity of the method is confirmed by the observation that the values of Tafel slope measured by coulostatic method are coincident with those obtained by Tafel lines extrapolation method with eliminating influence of IR drop, and the comparison of results obtained by solution analysis and electrochemical measurements shows that the method provides a faithful representation of corrosion behavior. The integral method has the advantages over differential method due to its simplicity and higher signal/noise ratio, so that the numerical al rithm gives the possibility of higher precision of corrosion measurements.
2005, 21(01): 98-101
doi: 10.3866/PKU.WHXB20050120
Abstract:
A new method was presented for controllable preparation of nanoscale drug carriers based on the phase behaviors of microemulsions. The pseudoternary phase diagrams for the system polyoxyethylene (40)stearate (S-40)/polyoxyethylene-polyoxypropylene (F-68)/Glycerol monostearate (GMS)/water were obtained at 60 ℃ using home-made apparatus with temperature control.Different structures of microemulsion (W/O,B.C.and O/W) were distinguished by the conductivity measurement, and liquid crystal region was found to be in existence. The mass ratio of S-40 and F-68 was selected to be 7 ∶3. It was concluded that the introduce of retinoic acid (RA) has little influence on the phase behavior of drug-loading microemulsions. Solid lipid nanoparticle (SLN) of retinoic acid was prepared based on the phase behavior results. The mean particle size of RA-SLN determined by PCS is about 10 nm, and TEM images indicate that particles of RA-SLN are spherical with a size about 10 nm. The study on the phase behaviors of drug-loading microemulsions has been proved to be very significative for the controllable preparation of SLN.
A new method was presented for controllable preparation of nanoscale drug carriers based on the phase behaviors of microemulsions. The pseudoternary phase diagrams for the system polyoxyethylene (40)stearate (S-40)/polyoxyethylene-polyoxypropylene (F-68)/Glycerol monostearate (GMS)/water were obtained at 60 ℃ using home-made apparatus with temperature control.Different structures of microemulsion (W/O,B.C.and O/W) were distinguished by the conductivity measurement, and liquid crystal region was found to be in existence. The mass ratio of S-40 and F-68 was selected to be 7 ∶3. It was concluded that the introduce of retinoic acid (RA) has little influence on the phase behavior of drug-loading microemulsions. Solid lipid nanoparticle (SLN) of retinoic acid was prepared based on the phase behavior results. The mean particle size of RA-SLN determined by PCS is about 10 nm, and TEM images indicate that particles of RA-SLN are spherical with a size about 10 nm. The study on the phase behaviors of drug-loading microemulsions has been proved to be very significative for the controllable preparation of SLN.
2005, 21(01): 102-105
doi: 10.3866/PKU.WHXB20050121
Abstract:
A series of CuO/Al2O3 catalysts were prepared by impregnation method with different loadings, and calcined temperatures. The phase evolution of the surface region and the bulk on the CuO/Al2O3 catalysts was characterized by high-temperature in-situ XRD and Raman techniques. The experimental results show that CuAl2O4 phase formed as a result of a solid-solid interaction between CuO and Al2O3 when the calcination temperature reaches to 800 ℃,and the amount of CuAl2O4 increases at high temperature, which brings on the CuO in the surface region becomes more difficult to extend into the bulk, then the CuO can be stabilized on the surface region even after calcination at 900 ℃.
A series of CuO/Al2O3 catalysts were prepared by impregnation method with different loadings, and calcined temperatures. The phase evolution of the surface region and the bulk on the CuO/Al2O3 catalysts was characterized by high-temperature in-situ XRD and Raman techniques. The experimental results show that CuAl2O4 phase formed as a result of a solid-solid interaction between CuO and Al2O3 when the calcination temperature reaches to 800 ℃,and the amount of CuAl2O4 increases at high temperature, which brings on the CuO in the surface region becomes more difficult to extend into the bulk, then the CuO can be stabilized on the surface region even after calcination at 900 ℃.
2005, 21(01): 106-109
doi: 10.3866/PKU.WHXB20050122
Abstract:
Nano-wire mostly composed of lactic acid molecules was prepared by solution method successfully. FESEM, TEM, EDX, TGA and FT-IR were used to characterize the morphology and structure of nano-wire obtained. The factors affecting the nano-wire formation were studied in this work. The results indicated that the addition of zinc ion in the formulation of preparation is essential for the nano-wire formation. The mechanism of nano-wire formation was discussed preliminarily.
Nano-wire mostly composed of lactic acid molecules was prepared by solution method successfully. FESEM, TEM, EDX, TGA and FT-IR were used to characterize the morphology and structure of nano-wire obtained. The factors affecting the nano-wire formation were studied in this work. The results indicated that the addition of zinc ion in the formulation of preparation is essential for the nano-wire formation. The mechanism of nano-wire formation was discussed preliminarily.
