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2002 Volume 18 Issue 12
2002, 18(12): 1057-1061
doi: 10.3866/PKU.WHXB20021201
Abstract:
The polycrystalline vanadyl phthalocyanine (VOPc) nanoparticles in phase I and phase II have been fabricated by laser ablation in aqueous solution without or with a kind of nonionic surfactants respectively. X-ray diffraction patterns, UV-Vis absorption spectroscopy and Fourier-transform infrared (FT-IR) spectroscopy have been used to characterize the crystalline structures in VOPc nanoparticles. About 100 nm-sized in phase I and 60 nm-sized in phase II particles of VOPc are observed by a scanning electron microscope (SEM). The formation mechanism of VOPc nanoparticles in phase II is discussed in this paper.
The polycrystalline vanadyl phthalocyanine (VOPc) nanoparticles in phase I and phase II have been fabricated by laser ablation in aqueous solution without or with a kind of nonionic surfactants respectively. X-ray diffraction patterns, UV-Vis absorption spectroscopy and Fourier-transform infrared (FT-IR) spectroscopy have been used to characterize the crystalline structures in VOPc nanoparticles. About 100 nm-sized in phase I and 60 nm-sized in phase II particles of VOPc are observed by a scanning electron microscope (SEM). The formation mechanism of VOPc nanoparticles in phase II is discussed in this paper.
2002, 18(12): 1062-1067
doi: 10.3866/PKU.WHXB20021202
Abstract:
Submonolayer assembly of Au (core)-Cu (shell) nanoparticles was prepared by electrodeposition of Cu on Au nanoparticles assembly electrode, where AUDT＋DT mixed monolayer was used as the coupling layer between ld substrate and Au nanoparticles. Under suitable polarized potential, Cu was found to be selectively electrodeposited on Au nanoparticles rather than on the organic monolayer. At －0.03 V, Au (core)-Cu (shell) nanoparticles have od monodispersity and spherical shape until their diameters exceeded 20 nm,and the diameters of which are in od accordance with those calculated by coulometry.
Submonolayer assembly of Au (core)-Cu (shell) nanoparticles was prepared by electrodeposition of Cu on Au nanoparticles assembly electrode, where AUDT＋DT mixed monolayer was used as the coupling layer between ld substrate and Au nanoparticles. Under suitable polarized potential, Cu was found to be selectively electrodeposited on Au nanoparticles rather than on the organic monolayer. At －0.03 V, Au (core)-Cu (shell) nanoparticles have od monodispersity and spherical shape until their diameters exceeded 20 nm,and the diameters of which are in od accordance with those calculated by coulometry.
2002, 18(12): 1068-1070
doi: 10.3866/PKU.WHXB20021203
Abstract:
Transition metal catalyst based on nickel containing coordinated N and O atoms is a new type of polyolefin catalyst. We modeled a Ni catalyst with [NH=CH－CH=CH－O],and studied the reaction mechanism by the model catalyst using density functional method at the B3LYP/LANL2MB level. The results showed that at first the cationic complex forms a square-planar structure with a vacant site. An ethylene molecule attacks the vacant site, perpendicularly to the [Ni(N=C－C=C－O)] plane, and then it rotates into the plane for an insertion reaction. After insertion reaction, a β- a stic hydrogen bond is formed between Ni and Cβ－H7 so as to assist the regeneracy of a new vacant site and to realize the chain propagation.
Transition metal catalyst based on nickel containing coordinated N and O atoms is a new type of polyolefin catalyst. We modeled a Ni catalyst with [NH=CH－CH=CH－O],and studied the reaction mechanism by the model catalyst using density functional method at the B3LYP/LANL2MB level. The results showed that at first the cationic complex forms a square-planar structure with a vacant site. An ethylene molecule attacks the vacant site, perpendicularly to the [Ni(N=C－C=C－O)] plane, and then it rotates into the plane for an insertion reaction. After insertion reaction, a β- a stic hydrogen bond is formed between Ni and Cβ－H7 so as to assist the regeneracy of a new vacant site and to realize the chain propagation.
2002, 18(12): 1071-1075
doi: 10.3866/PKU.WHXB20021204
Abstract:
Short chain fatty alcohol (ethanol, n-propanol, n-butanol) was added into the 1:1 mixed systems of cationic and anionic surfactants (sodium dodecyl sulfate-octyltrimythylammonium bromide, sodium dodecyl sulfate-dodecyltrimythylammonium bromide).The precipitation of this kind of catanionic surfactants will be dissolved, and an aqueous two-phase will be formed after the addition of short-chained fatty alcohol. The surfactant concentration is bigger in the upper phase, and smaller in the lower phase respectively. The results of TEM and birefringence observation showed that vesicle and liquid crystal spontaneously formed in the lower and upper phase, respectively. The volume ratio of the aqueous two-phase would increase with the decrease of carbon chain of alcohol, and decrease with the increase of temperature. Sonication also promotes the transition from precipitation to vesicle, which is similar to the effect of addition of short chain fatty alcohols.
Short chain fatty alcohol (ethanol, n-propanol, n-butanol) was added into the 1:1 mixed systems of cationic and anionic surfactants (sodium dodecyl sulfate-octyltrimythylammonium bromide, sodium dodecyl sulfate-dodecyltrimythylammonium bromide).The precipitation of this kind of catanionic surfactants will be dissolved, and an aqueous two-phase will be formed after the addition of short-chained fatty alcohol. The surfactant concentration is bigger in the upper phase, and smaller in the lower phase respectively. The results of TEM and birefringence observation showed that vesicle and liquid crystal spontaneously formed in the lower and upper phase, respectively. The volume ratio of the aqueous two-phase would increase with the decrease of carbon chain of alcohol, and decrease with the increase of temperature. Sonication also promotes the transition from precipitation to vesicle, which is similar to the effect of addition of short chain fatty alcohols.
2002, 18(12): 1076-1080
doi: 10.3866/PKU.WHXB20021205
Abstract:
Insoluble calcium salts are always observed in different types of gallstones, such as calcium phosphate, calcium carbonate and calcium bilirubinate. The major form of calcium phosphate in gallstone is calcium hydroxyapatite (HAP). Understanding of the transformation of amorphous calcium phosphate (ACP) into HAP in bile is necessary to prevent gallstones formation. The aim of this paper was to examine the interaction of bile salts, an important bio-surfactant, with ACP using vibrational spectroscopy. ACP [(Ca9－x(HPO4)2x(PO4)6－2x)],calcium hydrogen phosphate(CaHPO4•2H2O) and calcium phosphate(Ca3(PO4)2) precipitations were synthesized. CaHPO4 reacted with NaDC (0.1 mol•L－1) completely in solution, and mixed complex(NamCan(DC)2n＋m) precipitate formed. In contrast, only part of Ca3(PO4)2 reacted with NaDC, and the aggregate of NaDC in solution increased by Ca2＋bridge. It indicated that the micelle of NaDC bound to Ca2＋ on the solid surface of both CaHPO4 and Ca3(PO4)2, and the reactivity of CaHPO4 was more stronger than that of Ca3(PO4)2. ACP reacted with NaDC, NaTC and NaC respectively. The results demonstrated that the solubility of ACP increased with increase of bile salts content in solution. The reacting capacity of bile salts for ACP has the following order: NaDC >NaTC >NaC. The affinity of bile salts micelle to calcium binding to in ACP is stronger than binding to PO43－. Therefore, ACP transfers easily into HAP under bile condition.
Insoluble calcium salts are always observed in different types of gallstones, such as calcium phosphate, calcium carbonate and calcium bilirubinate. The major form of calcium phosphate in gallstone is calcium hydroxyapatite (HAP). Understanding of the transformation of amorphous calcium phosphate (ACP) into HAP in bile is necessary to prevent gallstones formation. The aim of this paper was to examine the interaction of bile salts, an important bio-surfactant, with ACP using vibrational spectroscopy. ACP [(Ca9－x(HPO4)2x(PO4)6－2x)],calcium hydrogen phosphate(CaHPO4•2H2O) and calcium phosphate(Ca3(PO4)2) precipitations were synthesized. CaHPO4 reacted with NaDC (0.1 mol•L－1) completely in solution, and mixed complex(NamCan(DC)2n＋m) precipitate formed. In contrast, only part of Ca3(PO4)2 reacted with NaDC, and the aggregate of NaDC in solution increased by Ca2＋bridge. It indicated that the micelle of NaDC bound to Ca2＋ on the solid surface of both CaHPO4 and Ca3(PO4)2, and the reactivity of CaHPO4 was more stronger than that of Ca3(PO4)2. ACP reacted with NaDC, NaTC and NaC respectively. The results demonstrated that the solubility of ACP increased with increase of bile salts content in solution. The reacting capacity of bile salts for ACP has the following order: NaDC >NaTC >NaC. The affinity of bile salts micelle to calcium binding to in ACP is stronger than binding to PO43－. Therefore, ACP transfers easily into HAP under bile condition.
2002, 18(12): 1081-1086
doi: 10.3866/PKU.WHXB20021206
Abstract:
The density function theory(DFT) B3LYP study on the 2-C5H10＋ and 1-C5H10＋ radical cations has been carried out. The molecular geometries for various conformations of the two cations were optimized at the B3LYP/6-31G(d, p), B3LYP/6-31＋G(d, p), B3LYP/6-311G(d, p), and B3LYP/6-311＋G(d, p) levels， and the frequency analysis calculations were performed at the B3LYP/6-311G(d, p) level. The 1-C5H10＋ ion was predicted to have a nonplanar structure, which is in contrast to the previous conclusions based on ab initio calculations. Based on the B3LYP/6-311G(d, p) geometries, the proton isotropic hyperfine coupling constants (HFCCs) were calculated at the B3LYP/6-311G(d, p) and MP2(full)/6-311G(d, p) levels. The calculated HFCCs results are in od agreement with experiment and more accurate than the previous theoretical results.
The density function theory(DFT) B3LYP study on the 2-C5H10＋ and 1-C5H10＋ radical cations has been carried out. The molecular geometries for various conformations of the two cations were optimized at the B3LYP/6-31G(d, p), B3LYP/6-31＋G(d, p), B3LYP/6-311G(d, p), and B3LYP/6-311＋G(d, p) levels， and the frequency analysis calculations were performed at the B3LYP/6-311G(d, p) level. The 1-C5H10＋ ion was predicted to have a nonplanar structure, which is in contrast to the previous conclusions based on ab initio calculations. Based on the B3LYP/6-311G(d, p) geometries, the proton isotropic hyperfine coupling constants (HFCCs) were calculated at the B3LYP/6-311G(d, p) and MP2(full)/6-311G(d, p) levels. The calculated HFCCs results are in od agreement with experiment and more accurate than the previous theoretical results.
2002, 18(12): 1087-1092
doi: 10.3866/PKU.WHXB20021207
Abstract:
In this paper, two kinds of 3D-QSAR techniques: comparative molecular fields analysis (CoMFA) and comparative similarity indices analysis (CoMSIA) were applied using a data set of 37 melatonin anta nists. The influences of different grid spacing and partial charge models were systematically investigated. The CoMFA contour plots identified several essential features including steric and electrostatic fields, which are valuable for us to take insight into the mechanisms of the intermolecular interactions between inhibitors and receptor.
In this paper, two kinds of 3D-QSAR techniques: comparative molecular fields analysis (CoMFA) and comparative similarity indices analysis (CoMSIA) were applied using a data set of 37 melatonin anta nists. The influences of different grid spacing and partial charge models were systematically investigated. The CoMFA contour plots identified several essential features including steric and electrostatic fields, which are valuable for us to take insight into the mechanisms of the intermolecular interactions between inhibitors and receptor.
2002, 18(12): 1093-1098
doi: 10.3866/PKU.WHXB20021208
Abstract:
Cr-Ni binary system was constructed by the determination of normal alloy samples and diffusion couple samples using XRD, electron probe microanalysis, scanning electron microscopy and differential thermal analysis. In our studies the , γ andα phases exist in Cr-Ni binary phase diagram. The structures of the , γ and α phases belong to A2, A1 and , respectively. The lattice parameters of these phases increase with temperature and with increasing of chromium concentration. The effect of temperature on the change of lattice parameters is more obvious than that of Cr concentration. The δ phase is only confirmed in the alloys after DTA and cast alloys by X-ray diffraction.δ phase belongs to metastable phase.
Cr-Ni binary system was constructed by the determination of normal alloy samples and diffusion couple samples using XRD, electron probe microanalysis, scanning electron microscopy and differential thermal analysis. In our studies the , γ andα phases exist in Cr-Ni binary phase diagram. The structures of the , γ and α phases belong to A2, A1 and , respectively. The lattice parameters of these phases increase with temperature and with increasing of chromium concentration. The effect of temperature on the change of lattice parameters is more obvious than that of Cr concentration. The δ phase is only confirmed in the alloys after DTA and cast alloys by X-ray diffraction.δ phase belongs to metastable phase.
2002, 18(12): 1099-1103
doi: 10.3866/PKU.WHXB20021209
Abstract:
The n-p coupled semiconductor material 0.5％Cu/TiO2-2.0％NiO was prepared using sol-gel method, on which the photo stimulated surface reaction (PSSR) of the synthesis of CH3OH from CO2 and H2O was studied. XRD, TEM, IR, UV-Vis and TPD experiments were adopted to characterizing the structure, photon absorbing and chemisorbing ability of the material. It was revealed that, during PSSR on the prepared material,CH3OH can be secured at normal temperature; while at the temperature of 200 ℃,CO2 conversion can be further increased, and the selectivity for CH3OH could reach up to 87.5％, because of the light-surface-heat cooperation effect. According to the experimental results, the surface precursor of CH3OH was specified to be the horizontal adsorbed state of CO2.Finally the PSSR mechanism was presented.
The n-p coupled semiconductor material 0.5％Cu/TiO2-2.0％NiO was prepared using sol-gel method, on which the photo stimulated surface reaction (PSSR) of the synthesis of CH3OH from CO2 and H2O was studied. XRD, TEM, IR, UV-Vis and TPD experiments were adopted to characterizing the structure, photon absorbing and chemisorbing ability of the material. It was revealed that, during PSSR on the prepared material,CH3OH can be secured at normal temperature; while at the temperature of 200 ℃,CO2 conversion can be further increased, and the selectivity for CH3OH could reach up to 87.5％, because of the light-surface-heat cooperation effect. According to the experimental results, the surface precursor of CH3OH was specified to be the horizontal adsorbed state of CO2.Finally the PSSR mechanism was presented.
2002, 18(12): 1104-1109
doi: 10.3866/PKU.WHXB20021210
Abstract:
Based on the crystal structure data of the lanthanide complexes, lanthanide contraction of the single valance bond length R0 for Ln－O bond is confirmed. The R0 values with B=0.037 nm were re-determined systematically as described by the linear equation R0 (nm)=0.2879－0.00132N, where N is the atomic number of lanthanide. Using the parameters suggested by Brown-O′Keeffe and the present authors, the bond valance sums for Ln(III) in some organometallic compounds were calculated and discussed in detail. Prospects for the further studies in the line of bond valence parameters were briefly presented.
Based on the crystal structure data of the lanthanide complexes, lanthanide contraction of the single valance bond length R0 for Ln－O bond is confirmed. The R0 values with B=0.037 nm were re-determined systematically as described by the linear equation R0 (nm)=0.2879－0.00132N, where N is the atomic number of lanthanide. Using the parameters suggested by Brown-O′Keeffe and the present authors, the bond valance sums for Ln(III) in some organometallic compounds were calculated and discussed in detail. Prospects for the further studies in the line of bond valence parameters were briefly presented.
2002, 18(12): 1110-1115
doi: 10.3866/PKU.WHXB20021211
Abstract:
Densities of serine in glucose-water and sucrose-water mixed solvents have been measured at 298.15 K by an oscillating-tube densimeter. Apparent molar volumes, limiting partial molar volumes and number of hydration of serine have been calculated. The transfer volumes from water to sugar-water mixtures have been obtained and discussed in terms of the structural hydration interaction model. The results obtained have been compared with that in glycerol-water and ethylene glycol-water mixtures. It is concluded that the magnitude of enhancement effect on volume is related to the number of OH groups.
Densities of serine in glucose-water and sucrose-water mixed solvents have been measured at 298.15 K by an oscillating-tube densimeter. Apparent molar volumes, limiting partial molar volumes and number of hydration of serine have been calculated. The transfer volumes from water to sugar-water mixtures have been obtained and discussed in terms of the structural hydration interaction model. The results obtained have been compared with that in glycerol-water and ethylene glycol-water mixtures. It is concluded that the magnitude of enhancement effect on volume is related to the number of OH groups.
2002, 18(12): 1116-1119
doi: 10.3866/PKU.WHXB20021212
Abstract:
The phase equilibrium of 2M •2B2O3•MgCl2•14H2O-MgCl2-H2O system at 30 ℃ has been studied. The experimental results showed that the phase transformation product was inderite(2M •3B2O3•15H2O) when the mass fraction of MgCl2 is in the range 0 to 2％, pinnate(M •B2O3•3H2O) in the range 2％ to 13.8％, demonstrating a great reduction in the temperature of formation of M •B2O3•3H2O and providing some physico-chemical basis in explaining the formation of pinnoite mineral in the salt lakes. When the mass fraction of MgCl2 was higher than 13.8％, the chloropinnoite dissolved congruently and did not transform. The mechanisms of the dissolution and phase transformation have been proposed.
The phase equilibrium of 2M •2B2O3•MgCl2•14H2O-MgCl2-H2O system at 30 ℃ has been studied. The experimental results showed that the phase transformation product was inderite(2M •3B2O3•15H2O) when the mass fraction of MgCl2 is in the range 0 to 2％, pinnate(M •B2O3•3H2O) in the range 2％ to 13.8％, demonstrating a great reduction in the temperature of formation of M •B2O3•3H2O and providing some physico-chemical basis in explaining the formation of pinnoite mineral in the salt lakes. When the mass fraction of MgCl2 was higher than 13.8％, the chloropinnoite dissolved congruently and did not transform. The mechanisms of the dissolution and phase transformation have been proposed.
2002, 18(12): 1120-1124
doi: 10.3866/PKU.WHXB20021213
Abstract:
The electro-oxidation of CH3OH on underpotentially-deposited-tin-modified platinum electrode (upd-Sn/Pt) has been studied. In this study, we aimed to clarify the role of tin playing in methanol electroxidation by using electrochemical techniques and surface-enhanced infrared absorption spectroscopy (SEIRAS). The following points have been obtained through the study. The upd-Sn modified Pt electrode with coverage around 0.20 shows a remarkably enhanced activity for the electro-oxidation of CH3OH; As long as the potential is lower than 0.35 V (vs RHE),regardless of a pure Pt or the upd-Sn/ Pt electrode, the direct electro-oxidation of methanol only can reach the stage of COads formation,i.e.CH3OH/Pt=COads＋4H＋＋4e(Pt) (a). When the rate of the accumulation of COads exceeds the rate of the following reaction: Sn－OH＋COads = CO2＋H＋＋e (Sn) (b), the reaction (a) will slow down. When the surface of pure Pt is completely covered by COads, the reaction (a) will totally stop. There will be no current to be output until reaction (b) removes COads from the electrode surface. The more the sites of Pt occupied by Sn adatoms, the fewer the sites available for reaction (a). That is why an unduly high coverage of Sn will lead to the reduction of catalysis of upd-Sn/Pt electrode. The enhanced effect of tin on the methanol electroxidation is observed on both the bright platinum and the platinized platinum.
The electro-oxidation of CH3OH on underpotentially-deposited-tin-modified platinum electrode (upd-Sn/Pt) has been studied. In this study, we aimed to clarify the role of tin playing in methanol electroxidation by using electrochemical techniques and surface-enhanced infrared absorption spectroscopy (SEIRAS). The following points have been obtained through the study. The upd-Sn modified Pt electrode with coverage around 0.20 shows a remarkably enhanced activity for the electro-oxidation of CH3OH; As long as the potential is lower than 0.35 V (vs RHE),regardless of a pure Pt or the upd-Sn/ Pt electrode, the direct electro-oxidation of methanol only can reach the stage of COads formation,i.e.CH3OH/Pt=COads＋4H＋＋4e(Pt) (a). When the rate of the accumulation of COads exceeds the rate of the following reaction: Sn－OH＋COads = CO2＋H＋＋e (Sn) (b), the reaction (a) will slow down. When the surface of pure Pt is completely covered by COads, the reaction (a) will totally stop. There will be no current to be output until reaction (b) removes COads from the electrode surface. The more the sites of Pt occupied by Sn adatoms, the fewer the sites available for reaction (a). That is why an unduly high coverage of Sn will lead to the reduction of catalysis of upd-Sn/Pt electrode. The enhanced effect of tin on the methanol electroxidation is observed on both the bright platinum and the platinized platinum.
2002, 18(12): 1125-1128
doi: 10.3866/PKU.WHXB20021214
Abstract:
Power－time curves of amylase catalyzed reaction with or without activation were obtained with a 2277 thermal activity monitor(Sweden). The data of Km and vmax were calculated for enzyme-catalyzed reactions without activation. Data of apparent Km1 and vmax were calculated for activation (Ca2＋, Mg2＋) using thermokinetics theory and reduced extent method. From the relationship between and concentration of metal ions(c), the effects of the activation were gained for metal ions of amylase-catalyzed reaction.
Power－time curves of amylase catalyzed reaction with or without activation were obtained with a 2277 thermal activity monitor(Sweden). The data of Km and vmax were calculated for enzyme-catalyzed reactions without activation. Data of apparent Km1 and vmax were calculated for activation (Ca2＋, Mg2＋) using thermokinetics theory and reduced extent method. From the relationship between and concentration of metal ions(c), the effects of the activation were gained for metal ions of amylase-catalyzed reaction.
