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2007 Volume 23 Issue 3
2007, 23(03): 285-288
doi: 10.1016/S1872-1508(07)60020-5
Abstract:
Triethylamine pentaborate, [HN(C2H5)3][B5O6(OH)4] (1), was hydrothermally synthesized and characterized by single crystal X-ray diffraction, FTIR, elemental analysis, and thermogravimetric analysis. Compound 1 crystallized in the monoclinic system, space group P21/c with a=1.0036(2) nm, b=1.1353(2) nm, c=1.4843(3) nm, and β=106.54(3)°. It consisted of isolated borate polyanion [B5O6(OH)4]- and triethylamine cation [HN(C2H5)3]+. The anionic units, [B5O6(OH)4]-, were linked by hydrogen bonds to form a 3D supramolecular network containing large channels, in which the templating [HN(C2H5)3]+ cations were located.
Triethylamine pentaborate, [HN(C2H5)3][B5O6(OH)4] (1), was hydrothermally synthesized and characterized by single crystal X-ray diffraction, FTIR, elemental analysis, and thermogravimetric analysis. Compound 1 crystallized in the monoclinic system, space group P21/c with a=1.0036(2) nm, b=1.1353(2) nm, c=1.4843(3) nm, and β=106.54(3)°. It consisted of isolated borate polyanion [B5O6(OH)4]- and triethylamine cation [HN(C2H5)3]+. The anionic units, [B5O6(OH)4]-, were linked by hydrogen bonds to form a 3D supramolecular network containing large channels, in which the templating [HN(C2H5)3]+ cations were located.
2007, 23(03): 289-294
doi: 10.1016/S1872-1508(07)60021-7
Abstract:
A simple procedure based on gelatification, promoted by the ring-opening reaction of propylene oxide, was proposed for the synthesis of alumina, in which hydrated aluminium nitrate (Al(NO3)3·9H2O) was mixed with propylene oxide and gelated in ethanol solvent. After being dried and calcined under air atmosphere, a kind of amorphous alumina with a well-defined mesopores structure was obtained. The samples were characterized by BET, SEM, FT-IR, and DTA. The results of liquid nitrogen adsorption indicated that two clear peaks appeared in the pore size distribution of each sample, whereas the larger pores were inkbottle-like. The average pore size of the alumina could be controlled by tuning the molar ratio of propylene oxide to aluminium nitrate over a range of pore diameters from 2.8 to 6.0 nm. The mechanism of the gelatification was finally proposed according to the characterizations. Both pH detection and FT-IR results demonstrated that propylene oxide indeed acted as an irreversible proton scavenger that induceed inorganic aluminium ions to under hydrolysis and condensation to form the aluminium oxide framework.
A simple procedure based on gelatification, promoted by the ring-opening reaction of propylene oxide, was proposed for the synthesis of alumina, in which hydrated aluminium nitrate (Al(NO3)3·9H2O) was mixed with propylene oxide and gelated in ethanol solvent. After being dried and calcined under air atmosphere, a kind of amorphous alumina with a well-defined mesopores structure was obtained. The samples were characterized by BET, SEM, FT-IR, and DTA. The results of liquid nitrogen adsorption indicated that two clear peaks appeared in the pore size distribution of each sample, whereas the larger pores were inkbottle-like. The average pore size of the alumina could be controlled by tuning the molar ratio of propylene oxide to aluminium nitrate over a range of pore diameters from 2.8 to 6.0 nm. The mechanism of the gelatification was finally proposed according to the characterizations. Both pH detection and FT-IR results demonstrated that propylene oxide indeed acted as an irreversible proton scavenger that induceed inorganic aluminium ions to under hydrolysis and condensation to form the aluminium oxide framework.
2007, 23(03): 295-298
doi: 10.1016/S1872-1508(07)60022-9
Abstract:
The association between alcohols and N,N-dimethylacetamide in carbon tetrachloride was investigated using FTIR spectroscopy at 298 K. The formation constants for 1∶1 and 1∶2 complexes were calculated using the method of Whetsel and Kagarise. The observed 1∶1 complex values were also verified using the method of Nash. The rate of change in C=O bond moment on complexing with alcohols increased with increasing acidity of alcohols. The formation constant and values of free energy change increased with the increase in carbon chain length of alcohols, which suggested that the degree of complex formation varied with the length of the carbon chain of alcohols.
The association between alcohols and N,N-dimethylacetamide in carbon tetrachloride was investigated using FTIR spectroscopy at 298 K. The formation constants for 1∶1 and 1∶2 complexes were calculated using the method of Whetsel and Kagarise. The observed 1∶1 complex values were also verified using the method of Nash. The rate of change in C=O bond moment on complexing with alcohols increased with increasing acidity of alcohols. The formation constant and values of free energy change increased with the increase in carbon chain length of alcohols, which suggested that the degree of complex formation varied with the length of the carbon chain of alcohols.
2007, 23(03): 299-304
doi: 10.1016/S1872-1508(07)60023-0
Abstract:
Conducting polypyrrole films (PPy) doped with p-toluenesulfonate (TOS-), ClO-4, and Cl- were electro- chemically prepared, respectively. The electrochemical capacitance properties of the PPy films were investigated with cyclic voltammetry (CV), galvanostatic charge/discharge, and electrochemical impedance spectroscope (EIS) techniques. The morphology observation and structure analysis of PPy films were performed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The results showed that PPy-Cl and PPy-TOS were characterized with a highly porous and ordered structure, which led to their fast ion switch processes. Moreover, they exhibited a rectangle-like shape of voltammetry characteristics even at a scanning rate of 50 mV·s-1, a linear variation of the voltage with respect to time in charge/discharge process and almost ideal capacitance behavior in low frequency even on deeply charged/discharged states in 1 mol·L-1 KCl solution. Furthermore, specific capacitance of PPy-Cl (polymerization charge of 2 mAh·cm-2) would reach 270 F·g-1 (scanning rate of 5 mV·s-1) or 175 F·g-1 (scanning rate of 200 mV·s-1) and its specific energy could reach 35.3 mWh·g-1. Moreover, with heavier doping ion (TOS-), PPy-TOS (polymerization charge of 2 mAh·cm-2) had a slightly smaller specific capacitance (146 F·g-1, scanning rate of 5 mV·s-1) but very rapidly charge/discharge ability (specific capacitance of 123.6 F·g-1 at scanning rate of 200 mV·s-1) and its specific power could reach 10 W·g-1. In addition, both PPy-TOS and PPy-Cl had a od cycleability. All of the above implied that the PPy-Cl and PPy-TOS were two kinds of promising electrode material for supercapacitors.
Conducting polypyrrole films (PPy) doped with p-toluenesulfonate (TOS-), ClO-4, and Cl- were electro- chemically prepared, respectively. The electrochemical capacitance properties of the PPy films were investigated with cyclic voltammetry (CV), galvanostatic charge/discharge, and electrochemical impedance spectroscope (EIS) techniques. The morphology observation and structure analysis of PPy films were performed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The results showed that PPy-Cl and PPy-TOS were characterized with a highly porous and ordered structure, which led to their fast ion switch processes. Moreover, they exhibited a rectangle-like shape of voltammetry characteristics even at a scanning rate of 50 mV·s-1, a linear variation of the voltage with respect to time in charge/discharge process and almost ideal capacitance behavior in low frequency even on deeply charged/discharged states in 1 mol·L-1 KCl solution. Furthermore, specific capacitance of PPy-Cl (polymerization charge of 2 mAh·cm-2) would reach 270 F·g-1 (scanning rate of 5 mV·s-1) or 175 F·g-1 (scanning rate of 200 mV·s-1) and its specific energy could reach 35.3 mWh·g-1. Moreover, with heavier doping ion (TOS-), PPy-TOS (polymerization charge of 2 mAh·cm-2) had a slightly smaller specific capacitance (146 F·g-1, scanning rate of 5 mV·s-1) but very rapidly charge/discharge ability (specific capacitance of 123.6 F·g-1 at scanning rate of 200 mV·s-1) and its specific power could reach 10 W·g-1. In addition, both PPy-TOS and PPy-Cl had a od cycleability. All of the above implied that the PPy-Cl and PPy-TOS were two kinds of promising electrode material for supercapacitors.
2007, 23(03): 305-310
doi: 10.1016/S1872-1508(07)60024-2
Abstract:
A total of 15 conformers of proline were found and their geometrical structures, relative energies, harmonic frequencies, dipole moments, rotational constants, polarizabilities, and the difference in energies between HOMO and LUMO were calculated at the X3LYP/6-311++G(d, p) and the PBE1PBE/6-311++G(d, p) levels. Accurate relative energies were given at the X3LYP/6-311++G(3df, 3pd)//X3LYP/6-311++G(d, p) level of theory, which were in od agreement with high-level ab initio methods using large basis sets. The results of X3LYP are superior to those of PBE1PBE method. The characteristic H-bonding types for all the conformers were classified. The four most stable conformers had intramolecular H-bondings of N…H—O and N—H…O=C, and the dipole moments of conformers 1 and 2 were the largest and the polarizabilities were the smallest. An additional H-bonding C—H…O=C was found. In combination with the principles of statistical mechanics, conformational distributions at room temperature were computed.
A total of 15 conformers of proline were found and their geometrical structures, relative energies, harmonic frequencies, dipole moments, rotational constants, polarizabilities, and the difference in energies between HOMO and LUMO were calculated at the X3LYP/6-311++G(d, p) and the PBE1PBE/6-311++G(d, p) levels. Accurate relative energies were given at the X3LYP/6-311++G(3df, 3pd)//X3LYP/6-311++G(d, p) level of theory, which were in od agreement with high-level ab initio methods using large basis sets. The results of X3LYP are superior to those of PBE1PBE method. The characteristic H-bonding types for all the conformers were classified. The four most stable conformers had intramolecular H-bondings of N…H—O and N—H…O=C, and the dipole moments of conformers 1 and 2 were the largest and the polarizabilities were the smallest. An additional H-bonding C—H…O=C was found. In combination with the principles of statistical mechanics, conformational distributions at room temperature were computed.
Quantum Chemistry and Electron Density Topological Study on the Reaction of CH2NH(s) with O(3P) Atom
2007, 23(03): 311-316
doi: 10.3866/PKU.WHXB20070306
Abstract:
The reactions of O(3P) with ground state CH2NH(s) were investigated using B3LYP, MP2 (full), and QCISD methods using 6-311G(d, p) and aug-cc-pVDZ basis sets. Geometries of stationary points on reaction potential surfaces were optimized using B3LYP and MP2(full) methods. The characterizations of the transition states were confirmed by vibration analysis. The reaction barriers are obtained using above-mentioned methods. The intrinsic reaction coordinates (IRC) were traced according to Fukui's theory and the connecting relationship of the transition states with the reactants and products was confirmed. The calculated results showed that O(3P) atom attacked N2 and C1 atoms in CH2NH(s) producing CH2NHO(t) and OCH2NH(t) respectively, CH2NHO(t) rearranged to CH3NO(t) through a ring structure transition state when H5 shifted from N to C1.
The reactions of O(3P) with ground state CH2NH(s) were investigated using B3LYP, MP2 (full), and QCISD methods using 6-311G(d, p) and aug-cc-pVDZ basis sets. Geometries of stationary points on reaction potential surfaces were optimized using B3LYP and MP2(full) methods. The characterizations of the transition states were confirmed by vibration analysis. The reaction barriers are obtained using above-mentioned methods. The intrinsic reaction coordinates (IRC) were traced according to Fukui's theory and the connecting relationship of the transition states with the reactants and products was confirmed. The calculated results showed that O(3P) atom attacked N2 and C1 atoms in CH2NH(s) producing CH2NHO(t) and OCH2NH(t) respectively, CH2NHO(t) rearranged to CH3NO(t) through a ring structure transition state when H5 shifted from N to C1.
2007, 23(03): 317-321
doi: 10.1016/S1872-1508(07)60025-4
Abstract:
The aggregation behavior of gemini surfactants 14-s-14 micelles in heavy water solutions was studied using 1H NMR relaxation and two-dimensional nuclear Overhauser enhancement spectroscopy (2D NOESY). Spin-lattice and spin-spin relaxation measurements of the protons showed that the motion of the spacer protons and a part of the methylene protons next to the polar head group was seriously restricted. Therefore, these protons should be involved in the formation of the surface layer of the hydrophobic micellar core. The hydrophobic protons that were away from the polar head group were situated internal in the micellar core and moved relatively freely. Relaxation measurements of the 14-s-14 series(s=2, 3, 4) also showed that the molecules were more tightly packed as the length of the spacer decreased. Their motion was relatively more restricted than those of TTAB, the monomeric homologue of 14-4-14. 2D NOESY spectrum of 14-4-14 exhibited the same pattern as that of 16-4-16. This showed that the micelles of 14-4-14 were spherical, the surface of which exhibited a saw-toothed form, similar to that of 16-4-16. Consequently, the length of the alkyl chain did not have any effect on the relative arrangement of molecules in the micelles.
The aggregation behavior of gemini surfactants 14-s-14 micelles in heavy water solutions was studied using 1H NMR relaxation and two-dimensional nuclear Overhauser enhancement spectroscopy (2D NOESY). Spin-lattice and spin-spin relaxation measurements of the protons showed that the motion of the spacer protons and a part of the methylene protons next to the polar head group was seriously restricted. Therefore, these protons should be involved in the formation of the surface layer of the hydrophobic micellar core. The hydrophobic protons that were away from the polar head group were situated internal in the micellar core and moved relatively freely. Relaxation measurements of the 14-s-14 series(s=2, 3, 4) also showed that the molecules were more tightly packed as the length of the spacer decreased. Their motion was relatively more restricted than those of TTAB, the monomeric homologue of 14-4-14. 2D NOESY spectrum of 14-4-14 exhibited the same pattern as that of 16-4-16. This showed that the micelles of 14-4-14 were spherical, the surface of which exhibited a saw-toothed form, similar to that of 16-4-16. Consequently, the length of the alkyl chain did not have any effect on the relative arrangement of molecules in the micelles.
2007, 23(03): 322-326
doi: 10.3866/PKU.WHXB20070308
Abstract:
A Chinese lantern-like silicon oxide nanostructure (nano-lantern) was synthesized on the silicon substrate by thermal evaporation method. The nano-lantern was characterized by scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), energy-dispersive spectroscope (EDS), and selective area electron diffraction (SAED). The results showed that the nano-lantern had symmetrical structure, with one end connecting with the silicon wafer and the other end being a tin ball. The diameter of the nano-lantern was about 1.5-3.0 μm, arc nanowires distributed between the two ends had a diameter ranging from 70 nm to 150 nm. The catalyst tin ball was a single crystal surrounded by the amorphous silicon oxide nanowires. In addition, the growth mechanism of the silica nano-lantern was discussed and a growth model was proposed. The growing direction of the nanowires and the movement direction of the catalyst Sn ball were not in the same direction, for this reason, the nanowires grew in a bent fashion and formed the Chinese lantern-like silicon oxide nanostructure. The controllable synthesis of the Chinese lantern-like silicon oxide nanostructure might have potential applications in photoelectronics device field.
A Chinese lantern-like silicon oxide nanostructure (nano-lantern) was synthesized on the silicon substrate by thermal evaporation method. The nano-lantern was characterized by scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), energy-dispersive spectroscope (EDS), and selective area electron diffraction (SAED). The results showed that the nano-lantern had symmetrical structure, with one end connecting with the silicon wafer and the other end being a tin ball. The diameter of the nano-lantern was about 1.5-3.0 μm, arc nanowires distributed between the two ends had a diameter ranging from 70 nm to 150 nm. The catalyst tin ball was a single crystal surrounded by the amorphous silicon oxide nanowires. In addition, the growth mechanism of the silica nano-lantern was discussed and a growth model was proposed. The growing direction of the nanowires and the movement direction of the catalyst Sn ball were not in the same direction, for this reason, the nanowires grew in a bent fashion and formed the Chinese lantern-like silicon oxide nanostructure. The controllable synthesis of the Chinese lantern-like silicon oxide nanostructure might have potential applications in photoelectronics device field.
2007, 23(03): 327-331
doi: 10.1016/S1872-1508(07)60026-6
Abstract:
Conductive sulfur-containing material (CSM), synthesized by simply heating a mixture of polyacrylonitrile (PAN) and elemental sulfur, and its composite with polyaniline (PAn) were used as the cathode material for rechargeable magnesium batteries. X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy measurements showed that the CSM consisted of a graphite-like microcrystal phase and an amorphous phase, with a dehydrapyrimidine-type matrix containing S—S bonds. When polyaniline was incorporated with CSM and Cu(II) was doped into the CSM/PAn composite, the specific discharge capacity and electrochemical reversibility were enhanced significantly. The composite exhibited a discharge capacity of 117.3 mAh·g-1 and the capacity retention remained at about 78% after twenty-two cycles, based on the second cycle discharge capacity. Here PAn functioned as both electrocatalyst and cathode material. At the same time, it improved the conductivity of the active CSM at a molecular level. The results of this study provided a new thought for structure design and development of a potential cathode material for rechargeable magnesium batteries.
Conductive sulfur-containing material (CSM), synthesized by simply heating a mixture of polyacrylonitrile (PAN) and elemental sulfur, and its composite with polyaniline (PAn) were used as the cathode material for rechargeable magnesium batteries. X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy measurements showed that the CSM consisted of a graphite-like microcrystal phase and an amorphous phase, with a dehydrapyrimidine-type matrix containing S—S bonds. When polyaniline was incorporated with CSM and Cu(II) was doped into the CSM/PAn composite, the specific discharge capacity and electrochemical reversibility were enhanced significantly. The composite exhibited a discharge capacity of 117.3 mAh·g-1 and the capacity retention remained at about 78% after twenty-two cycles, based on the second cycle discharge capacity. Here PAn functioned as both electrocatalyst and cathode material. At the same time, it improved the conductivity of the active CSM at a molecular level. The results of this study provided a new thought for structure design and development of a potential cathode material for rechargeable magnesium batteries.
2007, 23(03): 332-336
doi: 10.3866/PKU.WHXB20070310
Abstract:
A poly(L-threonine) modified electrode (PLTE) was fabricated by electrochemical immobilization of L-threonine on a glassy carbon electrode (GCE). The poly(L-threonine) layer exhibited superior electrocatalytic activity towards both dopamine (DA) and epinephrine (EP). The electrochemical behaviors of the modified electrode were explored in detail with cyclic voltammetry. The apparent electron transfer coefficient and standard rate constant were calculated to be 0.51 and 1.33 s-1, respectively, for the oxidation of EP in pH 2.5 phosphate buffer solution (PBS). The modified electrode exhibited a pair of redox peaks for the oxidation of DA in pH 7.5 PBS, the apparent electron transfer coefficient and standard rate constant were calculated to be 0.60 and 0.92 s-1, respectively. The cathodic peak currents were proportional to the concentration of DA and EP in the range of 1.0×10-6-5.0×10-4 mol·L-1 and 3.0×10-6-1.0×10-4 mol·L-1, respectively. This method was successfully applied for simultaneous determination of DA and EP.
A poly(L-threonine) modified electrode (PLTE) was fabricated by electrochemical immobilization of L-threonine on a glassy carbon electrode (GCE). The poly(L-threonine) layer exhibited superior electrocatalytic activity towards both dopamine (DA) and epinephrine (EP). The electrochemical behaviors of the modified electrode were explored in detail with cyclic voltammetry. The apparent electron transfer coefficient and standard rate constant were calculated to be 0.51 and 1.33 s-1, respectively, for the oxidation of EP in pH 2.5 phosphate buffer solution (PBS). The modified electrode exhibited a pair of redox peaks for the oxidation of DA in pH 7.5 PBS, the apparent electron transfer coefficient and standard rate constant were calculated to be 0.60 and 0.92 s-1, respectively. The cathodic peak currents were proportional to the concentration of DA and EP in the range of 1.0×10-6-5.0×10-4 mol·L-1 and 3.0×10-6-1.0×10-4 mol·L-1, respectively. This method was successfully applied for simultaneous determination of DA and EP.
2007, 23(03): 337-342
doi: 10.3866/PKU.WHXB20070311
Abstract:
Hydrophobically modified polyacrylamide with hydrophobic microblocks was prepared by homo-copolymerization of sodium 2-acrylamido-tetradecane sulfonate (NaAMC14S) and acrylamide (AM) in water, and cationic Gemini surfactant hexylene-1,6-bis(dodeccyldimethylammonium bromide) (C12C6C12Br2) was synthesized. Apparent viscosity measurement and fluorescence probe methods were used to study the interaction between copolymer NaAMC14S/AM and Gemini surfactant C12C6C12Br2. The experiment results showed that the interaction was strong and exhibited in several aspects as follows: addition of C12C6C12Br2 enabled the copolymer NaAMC14S/AM to produce intermolecular association below its critical association concentration in the absence of C12C6C12Br2; the mixed micells of NaAMC14S/AM and C12C6C12Br2 formed below the critical micellar concentration of C12C6C12Br2; for the aqueous solution of 0.30%(w) copolymer NaAMC14S/AM, the apparent viscosity increased dramatically with the increase of C12C6C12Br2 concentration, and the maximum value of the viscosity was enhanced three orders of magnitude higher than the initial value without C12C6C12Br2. It was found that the interaction between copolymer NaAMC14S/AM and C12C6C12Br2 was dependent on the microstructure of copolymer NaAMC14S/AM, and the greater the content of hydrophobic microblocks, the stronger the interaction and the greater the enhanced magnitude of viscosity.
Hydrophobically modified polyacrylamide with hydrophobic microblocks was prepared by homo-copolymerization of sodium 2-acrylamido-tetradecane sulfonate (NaAMC14S) and acrylamide (AM) in water, and cationic Gemini surfactant hexylene-1,6-bis(dodeccyldimethylammonium bromide) (C12C6C12Br2) was synthesized. Apparent viscosity measurement and fluorescence probe methods were used to study the interaction between copolymer NaAMC14S/AM and Gemini surfactant C12C6C12Br2. The experiment results showed that the interaction was strong and exhibited in several aspects as follows: addition of C12C6C12Br2 enabled the copolymer NaAMC14S/AM to produce intermolecular association below its critical association concentration in the absence of C12C6C12Br2; the mixed micells of NaAMC14S/AM and C12C6C12Br2 formed below the critical micellar concentration of C12C6C12Br2; for the aqueous solution of 0.30%(w) copolymer NaAMC14S/AM, the apparent viscosity increased dramatically with the increase of C12C6C12Br2 concentration, and the maximum value of the viscosity was enhanced three orders of magnitude higher than the initial value without C12C6C12Br2. It was found that the interaction between copolymer NaAMC14S/AM and C12C6C12Br2 was dependent on the microstructure of copolymer NaAMC14S/AM, and the greater the content of hydrophobic microblocks, the stronger the interaction and the greater the enhanced magnitude of viscosity.
2007, 23(03): 343-348
doi: 10.3866/PKU.WHXB20070312
Abstract:
The adsorption of binary and ternary mixtures of thiophene, benzene, and n-hexane in MFI and MOR zeolites was simulated by using the Monte Carlo technique in grand canonical ensemble. The binary simulation results showed that thiophene molecules took precedence over benzene molecules to occupy the intersection sites in MFI. When the pressure was raised, the loading of benzene increased gradually, whereas the loading of thiophene reached a plateau. Benzene molecules were pushed to the zig-zag or straight channels by thiophene molecules. The binary system in MFI conformed with competition model by Clark et al. However, there were no distinct preferred sites for adsorption of thiophene and benzene on MOR zeolite, and the systems complied with volume filling model. The ternary simulation results showed that the adsorptive amount of n-hexane was the greatest, while the thiophene and benzene are adsorbed very little in MFI zeolite. The adsorptive amount of thiophene was the greatest, while the n-hexane and benzene were adsorbed very little in MOR zeolite. For the molecules with bulker size, they could occupy only the main channel in MOR. A little amount of n-hexane had a stronger effect on the adsorption of benzene than that of thiophene.
The adsorption of binary and ternary mixtures of thiophene, benzene, and n-hexane in MFI and MOR zeolites was simulated by using the Monte Carlo technique in grand canonical ensemble. The binary simulation results showed that thiophene molecules took precedence over benzene molecules to occupy the intersection sites in MFI. When the pressure was raised, the loading of benzene increased gradually, whereas the loading of thiophene reached a plateau. Benzene molecules were pushed to the zig-zag or straight channels by thiophene molecules. The binary system in MFI conformed with competition model by Clark et al. However, there were no distinct preferred sites for adsorption of thiophene and benzene on MOR zeolite, and the systems complied with volume filling model. The ternary simulation results showed that the adsorptive amount of n-hexane was the greatest, while the thiophene and benzene are adsorbed very little in MFI zeolite. The adsorptive amount of thiophene was the greatest, while the n-hexane and benzene were adsorbed very little in MOR zeolite. For the molecules with bulker size, they could occupy only the main channel in MOR. A little amount of n-hexane had a stronger effect on the adsorption of benzene than that of thiophene.
2007, 23(03): 349-354
doi: 10.3866/PKU.WHXB20070313
Abstract:
Magnetite nanoparticles were synthesized by chemical coprecipitation of ferrous chloride and ferric sulfate. The obtained magnetite nanoparticles were surface-modified with 3-methacryloxypropyltrimethoxy silane(3-MPS) to form terminal vinyl groups as grafting sites. The polystyrene(PS)-grafted magnetite nanoparticles were prepared by controlled/“living” free radical polymerization by using benzoyl peroxide (BPO) as an initiator in the presence of 4-hydroxyl-2,2,6,6-tetramethyl-1-piperidinyloxy(HTEMPO·). XRD measurement showed the spinel structure for the magnetite nanoparticles. GPC analysis suggested the relationship between number average molecular weight of PS and polymerization time to be with approximate linear. The PS-grafted magnetite nanoparticles are uniform with diameters in the range from 20 nm to 30 nm from TEM. The content of magnetite in magnetic PS nanoparticles was 62.6% from the analysis of TG. The results of magnetic performance by VSM displayed that the magnetic PS nanoparticles exhibited the characteristics of single domain system when saturated magnetization was equal to 31.7 emu·g-1.
Magnetite nanoparticles were synthesized by chemical coprecipitation of ferrous chloride and ferric sulfate. The obtained magnetite nanoparticles were surface-modified with 3-methacryloxypropyltrimethoxy silane(3-MPS) to form terminal vinyl groups as grafting sites. The polystyrene(PS)-grafted magnetite nanoparticles were prepared by controlled/“living” free radical polymerization by using benzoyl peroxide (BPO) as an initiator in the presence of 4-hydroxyl-2,2,6,6-tetramethyl-1-piperidinyloxy(HTEMPO·). XRD measurement showed the spinel structure for the magnetite nanoparticles. GPC analysis suggested the relationship between number average molecular weight of PS and polymerization time to be with approximate linear. The PS-grafted magnetite nanoparticles are uniform with diameters in the range from 20 nm to 30 nm from TEM. The content of magnetite in magnetic PS nanoparticles was 62.6% from the analysis of TG. The results of magnetic performance by VSM displayed that the magnetic PS nanoparticles exhibited the characteristics of single domain system when saturated magnetization was equal to 31.7 emu·g-1.
2007, 23(03): 355-360
doi: 10.3866/PKU.WHXB20070314
Abstract:
The structural and adsorption properties of Cu(100)/H surface were studied using density-functional theory (DFT) and projector-augmented wave (PAW) method. It was concluded that atomic hydrogen was adsorbed on the four- fold hollow (FFH) site with a perpendicular distance of 0.052 nm from the outmost Cu layer for a Cu(100)c(2×2)/H geometry. The bond length between H atom and substrate was calculated to be about 0.189 nm. In this adsorbate-substrate system the surface work function was predicted to be about 4.47 eV, which was almost identical to that of a clean Cu(100) surface. The total-energy calculations showed that the chemisorption energy of atomic hydrogen in the case of Cu(100)c(2×2)/H surface was about 2.37 eV with respect to an isolated atomic hydrogen as reference. The hydrogen adsorption on Cu(100) surface yielded the hybridization between surface Cu atoms and adsorbed H, and gener- ated the surface localized states at -0.8 eV relative to Fermi energy EF. This system was modeled at different coverages using p(1×1), p(2×2), and p(3×3) geometries of hydrogen atoms adsorbed on the FFH sites of the Cu(100) surface. The corresponding equilibrium geometries were obtained by total energy and Helleman-Feynman force conjugate-gradient optimizations. In the regime of lower H coverages, the hybridization between adsorbed hydrogen and substrate displayed a type of Cu(S)-H-Cu(S-1) mixing.
The structural and adsorption properties of Cu(100)/H surface were studied using density-functional theory (DFT) and projector-augmented wave (PAW) method. It was concluded that atomic hydrogen was adsorbed on the four- fold hollow (FFH) site with a perpendicular distance of 0.052 nm from the outmost Cu layer for a Cu(100)c(2×2)/H geometry. The bond length between H atom and substrate was calculated to be about 0.189 nm. In this adsorbate-substrate system the surface work function was predicted to be about 4.47 eV, which was almost identical to that of a clean Cu(100) surface. The total-energy calculations showed that the chemisorption energy of atomic hydrogen in the case of Cu(100)c(2×2)/H surface was about 2.37 eV with respect to an isolated atomic hydrogen as reference. The hydrogen adsorption on Cu(100) surface yielded the hybridization between surface Cu atoms and adsorbed H, and gener- ated the surface localized states at -0.8 eV relative to Fermi energy EF. This system was modeled at different coverages using p(1×1), p(2×2), and p(3×3) geometries of hydrogen atoms adsorbed on the FFH sites of the Cu(100) surface. The corresponding equilibrium geometries were obtained by total energy and Helleman-Feynman force conjugate-gradient optimizations. In the regime of lower H coverages, the hybridization between adsorbed hydrogen and substrate displayed a type of Cu(S)-H-Cu(S-1) mixing.
2007, 23(03): 361-366
doi: 10.1016/S1872-1508(07)60027-8
Abstract:
Two types of tin oxide self-assembly nanostructures, lotus flower-shaped and chrysanthemum-shaped, were synthesized by chemical vapor deposition method using ld nanoparticles as catalyst. The lotus flower-shaped tin oxide nanostructure comprised a disc with meshes in nanoscale and a thin film of nanowires, whereas the chrysanthemum-shaped tin oxide nanostructure comprised nanowires or nanobelts in a radicalized arrangement. X-ray diffraction spectra indicated that the former was composed of Sn and SnO2 and the latter was composed of only SnO2. By adjusting these two suits of experimental parameters, such as pressure, temperature, flow rate carrier gas or oxygen in the carrier gas, and then characterizing the products with scanning electron microscopy and X-ray diffraction, possible growth mechanism for these two types of self-assembly tin oxide nanostructures was proposed.
Two types of tin oxide self-assembly nanostructures, lotus flower-shaped and chrysanthemum-shaped, were synthesized by chemical vapor deposition method using ld nanoparticles as catalyst. The lotus flower-shaped tin oxide nanostructure comprised a disc with meshes in nanoscale and a thin film of nanowires, whereas the chrysanthemum-shaped tin oxide nanostructure comprised nanowires or nanobelts in a radicalized arrangement. X-ray diffraction spectra indicated that the former was composed of Sn and SnO2 and the latter was composed of only SnO2. By adjusting these two suits of experimental parameters, such as pressure, temperature, flow rate carrier gas or oxygen in the carrier gas, and then characterizing the products with scanning electron microscopy and X-ray diffraction, possible growth mechanism for these two types of self-assembly tin oxide nanostructures was proposed.
2007, 23(03): 367-372
doi: 10.3866/PKU.WHXB20070316
Abstract:
Monodisperse Ag nanoparticles were prepared in quaternary W/O microemulsions containing Span 80-Tween 80, liquid paraffin and 1-butanol. It was found that mass ration of Span 80 and Tween 80 had an obvious effect on the morphology and size distribution of the Ag nanoparticles. Morphologies, structure and thermal properties of the silver nanoparticles were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), thermogravimetry (TG) and differential thermal analysis (DTA). The results show that the Ag nanoparticles have cube crystal structure; exhibit uniform size distribution and have an average size of 6 nm at the mass ratio of Span 80∶Tween 80=7∶3; and are coated with long chain fatty acid through carboxyl. H2O and 1-butanol in microemulsions were removed through vacuum distillation, and Ag nanoparticles were dispersed stably in liquid paraffin. The tribological properties of liquid paraffin containing Ag nanoparticles were evaluated on a four-ball test machine. Results showed that the Ag nanoparticles in liquid paraffin exhibited od antiwear property and could improve load carrying capacity of base oil remarkably.
Monodisperse Ag nanoparticles were prepared in quaternary W/O microemulsions containing Span 80-Tween 80, liquid paraffin and 1-butanol. It was found that mass ration of Span 80 and Tween 80 had an obvious effect on the morphology and size distribution of the Ag nanoparticles. Morphologies, structure and thermal properties of the silver nanoparticles were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), thermogravimetry (TG) and differential thermal analysis (DTA). The results show that the Ag nanoparticles have cube crystal structure; exhibit uniform size distribution and have an average size of 6 nm at the mass ratio of Span 80∶Tween 80=7∶3; and are coated with long chain fatty acid through carboxyl. H2O and 1-butanol in microemulsions were removed through vacuum distillation, and Ag nanoparticles were dispersed stably in liquid paraffin. The tribological properties of liquid paraffin containing Ag nanoparticles were evaluated on a four-ball test machine. Results showed that the Ag nanoparticles in liquid paraffin exhibited od antiwear property and could improve load carrying capacity of base oil remarkably.
2007, 23(03): 373-378
doi: 10.3866/PKU.WHXB20070317
Abstract:
Kinetic parameters were calculated based on the catalytic reaction systems of sodium caprolactam salt and N-75 biuret at the temperature of 145 ℃ to 160 ℃. The reaction order was approximately first order. The activation energy was between 73.2-77.1 kJ·mol-1 and the pre-exponential factor was between 2.9×1011-3.6×1011 mol1-n·s-1. The calculated reaction heat of 134.5-137.3 J·g-1 was in consonance with the literature value of 138.6 J·g-1. The adiabatic reaction kinetic model of caprolactam anion was constructed based on the existing research findings. The coincidence between the simulation results and the experimental data revealed that the model was reasonable and correct.
Kinetic parameters were calculated based on the catalytic reaction systems of sodium caprolactam salt and N-75 biuret at the temperature of 145 ℃ to 160 ℃. The reaction order was approximately first order. The activation energy was between 73.2-77.1 kJ·mol-1 and the pre-exponential factor was between 2.9×1011-3.6×1011 mol1-n·s-1. The calculated reaction heat of 134.5-137.3 J·g-1 was in consonance with the literature value of 138.6 J·g-1. The adiabatic reaction kinetic model of caprolactam anion was constructed based on the existing research findings. The coincidence between the simulation results and the experimental data revealed that the model was reasonable and correct.
2007, 23(03): 379-383
doi: 10.3866/PKU.WHXB20070318
Abstract:
Multiphoton ionization mass spectrum of methanol clusters was studied by using pulsed 355 nm laser to ionize supersonic molecular beam. Besides some fragment ions of methanol, protonated methanol cluster ions (CH3OH)nH+ (n=1-16) were observed and the cluster′s intensity distribution was not affected by laser delay time relative to pulsed molecular beam, which implied that the ions′ species and intensity were determined only by cluster′s inherent geometric stability. Possible stable geometry structures of (CH3OH)n and (CH3OH)nH+(n=1-4) were obtained by using ab initio calculation at B3LYP/6-31G(d) basis level. Comparing cluster′s infrared vibrational spectrum with related atomic motion image, it was found that the main contribution to the strongest IR mode came from the H stretch vibration of the hydrogen bond. Proton transfer reaction occurred within clusters after ionization possibly corresponded with the excitation of vibrational mode which is related to hydrogen bond.
Multiphoton ionization mass spectrum of methanol clusters was studied by using pulsed 355 nm laser to ionize supersonic molecular beam. Besides some fragment ions of methanol, protonated methanol cluster ions (CH3OH)nH+ (n=1-16) were observed and the cluster′s intensity distribution was not affected by laser delay time relative to pulsed molecular beam, which implied that the ions′ species and intensity were determined only by cluster′s inherent geometric stability. Possible stable geometry structures of (CH3OH)n and (CH3OH)nH+(n=1-4) were obtained by using ab initio calculation at B3LYP/6-31G(d) basis level. Comparing cluster′s infrared vibrational spectrum with related atomic motion image, it was found that the main contribution to the strongest IR mode came from the H stretch vibration of the hydrogen bond. Proton transfer reaction occurred within clusters after ionization possibly corresponded with the excitation of vibrational mode which is related to hydrogen bond.
2007, 23(03): 384-388
doi: 10.1016/S1872-1508(07)60028-X
Abstract:
A streamer corona plasma induced oxidation technique, which used the so called AC/DC power supply to convert high concentration ammonium sulfite to sulfate was reported. The results showed that the sulfite oxidation rate was significantly higher than that in the forced air oxidation process. Research of using streamer discharge plasmas, to oxidize high concentration ammonium sulfite in the liquid phase, has obtained a remarkable progress. On the basis of the experiment results, the following conclusions could be arrived at: (1) In contrast to the plasma-induced oxidation, the spontaneous oxidations gave negligible contributions to convert sulfite to sulfate. (2) When the initial sulfite concentration was within 1-3 mol·L-1, plasma induced one-cycle oxidation efficiency was in the range of 20%-60%. The oxidation rate was faster than that at concentrations less than 1 mol·L-1. To make the technique industrially applicable, the plasma induced oxidation process should be performed under the initial concentration more than 1 mol·L-1. (3) With the increase of the power density, the molar energy consumption of ammonium sulfite oxidation increased faster than the oxidation efficiency did, which indicated that radical-radical termination reactions dominated the process.
A streamer corona plasma induced oxidation technique, which used the so called AC/DC power supply to convert high concentration ammonium sulfite to sulfate was reported. The results showed that the sulfite oxidation rate was significantly higher than that in the forced air oxidation process. Research of using streamer discharge plasmas, to oxidize high concentration ammonium sulfite in the liquid phase, has obtained a remarkable progress. On the basis of the experiment results, the following conclusions could be arrived at: (1) In contrast to the plasma-induced oxidation, the spontaneous oxidations gave negligible contributions to convert sulfite to sulfate. (2) When the initial sulfite concentration was within 1-3 mol·L-1, plasma induced one-cycle oxidation efficiency was in the range of 20%-60%. The oxidation rate was faster than that at concentrations less than 1 mol·L-1. To make the technique industrially applicable, the plasma induced oxidation process should be performed under the initial concentration more than 1 mol·L-1. (3) With the increase of the power density, the molar energy consumption of ammonium sulfite oxidation increased faster than the oxidation efficiency did, which indicated that radical-radical termination reactions dominated the process.
2007, 23(03): 389-393
doi: 10.3866/PKU.WHXB20070320
Abstract:
A PtRu alloy thin-film used for catalytic electrodes of fuel cells was fabricated by ion beam sputtering (IBS). The structure, surface layer structure, chemical composition, surface chemical state, and morphology of the PtRu alloy thin-film were characterized using X-ray diffraction (XRD), grazing incidence X-ray diffraction (GIXD), X-ray photoelectron spectroscopy(XPS), and atomic force microscopy (AFM). It was shown that the surface chemical state and structure in the top layer (from 15-40 nm) of PtRu alloy thin-film were changed due to the strong interaction between Pt+ and Ru+ during the ion beam sputtering deposition process, which also affected the catalytic activity of the PtRu alloy thin-film. In particular, when the atomic ratio of xPt/xRu was 0.64, enrichment of the Ru solid solution and amorphous phase Pt39Ru61 were observed on the surface layer of PtRu alloy thin-film.
A PtRu alloy thin-film used for catalytic electrodes of fuel cells was fabricated by ion beam sputtering (IBS). The structure, surface layer structure, chemical composition, surface chemical state, and morphology of the PtRu alloy thin-film were characterized using X-ray diffraction (XRD), grazing incidence X-ray diffraction (GIXD), X-ray photoelectron spectroscopy(XPS), and atomic force microscopy (AFM). It was shown that the surface chemical state and structure in the top layer (from 15-40 nm) of PtRu alloy thin-film were changed due to the strong interaction between Pt+ and Ru+ during the ion beam sputtering deposition process, which also affected the catalytic activity of the PtRu alloy thin-film. In particular, when the atomic ratio of xPt/xRu was 0.64, enrichment of the Ru solid solution and amorphous phase Pt39Ru61 were observed on the surface layer of PtRu alloy thin-film.
Molecular Recognition of a Novel Bridged Bis(β-cyclodextrin) Tethered with Aromatic Diamine for Dyes
2007, 23(03): 394-398
doi: 10.3866/PKU.WHXB20070321
Abstract:
A novel bridged bis(β-cyclodextrin) with rigid aromatic diamino tethers, 3,3′-methylenedianilino-briged-bis(6-aimino-6-deoxy-β-cyclodextrin) (2), was synthesized by the reaction of mono-[6-o-(p-tolysulfonyl)]-β-cyclodextrin with 3,3′-methylenedianiline. The inclusion complexation behaviors of native β-cyclodextrin (1) and the novel briged(β-cyclodextrin) (2) with some organic dyes, i.e., acridine red (AR), neutral red (NR), sodium 6-toluidino-2-naphthalenes- ulfonate (TNS), ammonium 8-anilino-1-naphthalenesulfonate (ANS), rhodamine B (RhB) and brilliant green (BG) were investigated at 25 ℃ in aqueous phosphate buffer solution (pH=7.20) by means of fluorescence and ultraviolet spectroscopy. The spectral titrations gave the complex stability constants (KS) and Gibbs free energy changes (ΔG0) for the stoichiometry 1∶1 inclusion complexation of hosts examined with dye molecules. The obtained results demonstrated that bis(β-cyclodextrin) 2 showed much higher binding ability and molecular selectivity toward these guest dyes than native β-cyclodextrin 1. Typically, dimmer 2 displayed the highest binding ability upon inclusion complexation with BG, affording 22.2 times higher KS value than native β-cyclodextrin. The cooperative binding ability of the bis(β-cyclodextrin) was discussed from the viewpoints of size/shape-fit interaction and multiple recognition mechanism.
A novel bridged bis(β-cyclodextrin) with rigid aromatic diamino tethers, 3,3′-methylenedianilino-briged-bis(6-aimino-6-deoxy-β-cyclodextrin) (2), was synthesized by the reaction of mono-[6-o-(p-tolysulfonyl)]-β-cyclodextrin with 3,3′-methylenedianiline. The inclusion complexation behaviors of native β-cyclodextrin (1) and the novel briged(β-cyclodextrin) (2) with some organic dyes, i.e., acridine red (AR), neutral red (NR), sodium 6-toluidino-2-naphthalenes- ulfonate (TNS), ammonium 8-anilino-1-naphthalenesulfonate (ANS), rhodamine B (RhB) and brilliant green (BG) were investigated at 25 ℃ in aqueous phosphate buffer solution (pH=7.20) by means of fluorescence and ultraviolet spectroscopy. The spectral titrations gave the complex stability constants (KS) and Gibbs free energy changes (ΔG0) for the stoichiometry 1∶1 inclusion complexation of hosts examined with dye molecules. The obtained results demonstrated that bis(β-cyclodextrin) 2 showed much higher binding ability and molecular selectivity toward these guest dyes than native β-cyclodextrin 1. Typically, dimmer 2 displayed the highest binding ability upon inclusion complexation with BG, affording 22.2 times higher KS value than native β-cyclodextrin. The cooperative binding ability of the bis(β-cyclodextrin) was discussed from the viewpoints of size/shape-fit interaction and multiple recognition mechanism.
2007, 23(03): 399-403
doi: 10.3866/PKU.WHXB20070322
Abstract:
Reaction of CH3OH with SOCl2 producing CH3Cl and SO2 in two nonpolar (ε<15) and two polar (ε>15) solvents was studied using the B3LYP method and the SCIPCM model of the SCRF theory for simulating solution effects. The reaction process consists of reaction (1) and reaction (2) with CH3OS(O)Cl being a product of reaction (1) and the reactant of reaction (2). Reaction (2) has front-side substitution (via transition state TS3f) and back-side substitution (ionization of CH3OS(O)Cl followed by substitution via transition state TS3b) mechanisms. The calculations predicted that in gas phase and in the four solvents reactions (1) and (2) were exothermic and reaction (1) had the same reaction path (TS1→IM1→TS2). The calculations indicated that reaction (2) experienced very strong effects of solvent. In gas phase and in nonpolar solvents the front-side substitution was favored over the back-side substitution since TS3f is lower in energy than the (CH3OSO++Cl-) ion pair (IM2); and in polar solvents the back-side substitution was favored over the front-side substitution since IM2 and TS3b are lower in energy than TS3f.
Reaction of CH3OH with SOCl2 producing CH3Cl and SO2 in two nonpolar (ε<15) and two polar (ε>15) solvents was studied using the B3LYP method and the SCIPCM model of the SCRF theory for simulating solution effects. The reaction process consists of reaction (1) and reaction (2) with CH3OS(O)Cl being a product of reaction (1) and the reactant of reaction (2). Reaction (2) has front-side substitution (via transition state TS3f) and back-side substitution (ionization of CH3OS(O)Cl followed by substitution via transition state TS3b) mechanisms. The calculations predicted that in gas phase and in the four solvents reactions (1) and (2) were exothermic and reaction (1) had the same reaction path (TS1→IM1→TS2). The calculations indicated that reaction (2) experienced very strong effects of solvent. In gas phase and in nonpolar solvents the front-side substitution was favored over the back-side substitution since TS3f is lower in energy than the (CH3OSO++Cl-) ion pair (IM2); and in polar solvents the back-side substitution was favored over the front-side substitution since IM2 and TS3b are lower in energy than TS3f.
2007, 23(03): 404-408
doi: 10.3866/PKU.WHXB20070323
Abstract:
The charge transport performance of the Nafion-based redox polymer films prepared under different conditions was investigated by cyclic voltammetry in the sandwiched cells. The results showed that the apparent charge transfer diffusion coefficient(Dct) of the Nafion[M(bpy)2+3, PEG (polyethylene glycol)] (M=Ru or Fe) films is about 10-6-10-7 cm2·s-1 and the mobility of the electron or hole ( μ) was about 10-4-10-5 cm2·V-1·s-1. In order to decrease the resistance of the interface, a polyaniline (PANI) layer was added to the interface of indium tin oxide coated conducting glass (ITO) electrode and the redox polymer. Consequentially , the Dct could be increased to about 10-5-10-6 cm2·s-1 and μ to about 10-3-10-4 cm2·V-1·s-1, and the operating current of the cells under 600 mV bias could be increased by almost 100 times . In addition, the Dct and μ of this redox polymer film had just reduced slightly after 30 d kept in atmosphere. Therefore, the redox polymer film is sufficiently stable.
The charge transport performance of the Nafion-based redox polymer films prepared under different conditions was investigated by cyclic voltammetry in the sandwiched cells. The results showed that the apparent charge transfer diffusion coefficient(Dct) of the Nafion[M(bpy)2+3, PEG (polyethylene glycol)] (M=Ru or Fe) films is about 10-6-10-7 cm2·s-1 and the mobility of the electron or hole ( μ) was about 10-4-10-5 cm2·V-1·s-1. In order to decrease the resistance of the interface, a polyaniline (PANI) layer was added to the interface of indium tin oxide coated conducting glass (ITO) electrode and the redox polymer. Consequentially , the Dct could be increased to about 10-5-10-6 cm2·s-1 and μ to about 10-3-10-4 cm2·V-1·s-1, and the operating current of the cells under 600 mV bias could be increased by almost 100 times . In addition, the Dct and μ of this redox polymer film had just reduced slightly after 30 d kept in atmosphere. Therefore, the redox polymer film is sufficiently stable.
2007, 23(03): 409-413
doi: 10.3866/PKU.WHXB20070324
Abstract:
Oxidation of the drug guaifenesin by a Ag(III) complex anion, [Ag(HIO6)2]5-, was studied in aqueous alkaline medium by using spectrophotometry. The major oxidation product of guaifenesin was identified by mass spectrometry. The oxidation reaction displayed an overall second-order kinetics: first-order with respect to both Ag(III) and guaifenesin. Variations of [OH-] and [IO-4]tot had a significant influence on the reaction rates, where [IO-4]tot denotes the total concentration of periodate added externally. An empirical rate expression, k′=(ka+kb[OH-])K1/{f([OH-])[IO-4]tot+K1}, was derived, where ka=(2.6±1.2)×10-2 mol-1·L·s-1, kb=(2.8±0.1) mol-2·L2·s-1, and K1=(4.1±0.4)×10-4 mol·L-1 at 25.0 ℃ and ionic strength of 0.30 mol·L-1. Activation parameters associated with ka and kb were also derived. A mechanism involving the [Ag(HIO6)(OH)(H2O)]2- as the reactive species of the oxidant was proposed. Guaifenesin and the reactive species reversibly formed a complex, which decomposed by two parallel slow steps to give rise to the products: one pathway was spontaneous and the other was assisted by a hydroxide ion.
Oxidation of the drug guaifenesin by a Ag(III) complex anion, [Ag(HIO6)2]5-, was studied in aqueous alkaline medium by using spectrophotometry. The major oxidation product of guaifenesin was identified by mass spectrometry. The oxidation reaction displayed an overall second-order kinetics: first-order with respect to both Ag(III) and guaifenesin. Variations of [OH-] and [IO-4]tot had a significant influence on the reaction rates, where [IO-4]tot denotes the total concentration of periodate added externally. An empirical rate expression, k′=(ka+kb[OH-])K1/{f([OH-])[IO-4]tot+K1}, was derived, where ka=(2.6±1.2)×10-2 mol-1·L·s-1, kb=(2.8±0.1) mol-2·L2·s-1, and K1=(4.1±0.4)×10-4 mol·L-1 at 25.0 ℃ and ionic strength of 0.30 mol·L-1. Activation parameters associated with ka and kb were also derived. A mechanism involving the [Ag(HIO6)(OH)(H2O)]2- as the reactive species of the oxidant was proposed. Guaifenesin and the reactive species reversibly formed a complex, which decomposed by two parallel slow steps to give rise to the products: one pathway was spontaneous and the other was assisted by a hydroxide ion.
2007, 23(03): 414-418
doi: 10.3866/PKU.WHXB20070325
Abstract:
TiO2 thin films were prepared at low-temperature by the sol-gel method. The as-prepared TiO2 sols were characterized with X-ray diffraction (XRD) and transmission electron microscopy (TEM), TiO2 films were characterized with UV-Vis spectra and atomic force microscopy (AFM), respectively. The photocatalytic activity of the thin films was evaluated by the degradation of rhodamine B in aqueous solution under UV irradiation．The results indicated that a bicrystalline framework of anatase and brookite was present in the as-prepared films. And the TiO2 films showed high transmittance and photocatalytic activity. The effect of sol-refluxing temperature on the performance of TiO2 films was investigated. The increase of sol-refluxing temperature led to the improved photocatalytic activity of TiO2 films. This is due to the crystalline perfection of TiO2 sols and average roughness enlargement of TiO2 films. The TiO2 films prepared by the sol refluxed at 100 ℃ showed the highest photocatalytic activity.
TiO2 thin films were prepared at low-temperature by the sol-gel method. The as-prepared TiO2 sols were characterized with X-ray diffraction (XRD) and transmission electron microscopy (TEM), TiO2 films were characterized with UV-Vis spectra and atomic force microscopy (AFM), respectively. The photocatalytic activity of the thin films was evaluated by the degradation of rhodamine B in aqueous solution under UV irradiation．The results indicated that a bicrystalline framework of anatase and brookite was present in the as-prepared films. And the TiO2 films showed high transmittance and photocatalytic activity. The effect of sol-refluxing temperature on the performance of TiO2 films was investigated. The increase of sol-refluxing temperature led to the improved photocatalytic activity of TiO2 films. This is due to the crystalline perfection of TiO2 sols and average roughness enlargement of TiO2 films. The TiO2 films prepared by the sol refluxed at 100 ℃ showed the highest photocatalytic activity.
2007, 23(03): 419-423
doi: 10.3866/PKU.WHXB20070326
Abstract:
Butanediyl-α, ω-bis-(dialkyldodecyl-ammonium bromides) (alkyl = methyl, ethyl, and propyl), which referred to as C12(n)-4-C12(n)·2Br (n=1, 2, 3), had been synthesized. The results studied by dilution method showed that a part of n-hexanol in n-heptane together with surfactant constructed a mixed film, which improved the molecular geometry of the mixed components and resulted in the formation of W/O microemulsion. The size of the water pool enlarged with increasing water content W0, which decreased the surface curvature of the water pool and therefore reduced the requirement for n-hexanol in the mixed film. With increasing the head-group size of C12(n)-4-C12(n)·2Br, i.e. n from 1 to 2, the mole ratio of n-hexanol at the film to surfactant a increased, and then decreased with further increasing n from 2 to 3. At W0=10 and 20, the radius of water pool RW reduced with increasing n, but at W0=30, RW increased considerably with increasing n from 2 to 3. These results indicated that the propyl groups linked with quaternary ammonium behaved differently from linked methyl or ethyl groups. The propyl groups may bend toward the bulk n-heptane. This unfurled the volume of the alkyl chain region of surfactant and thus decreased the requirement for n-hexanol in the film, which favored to form large water pool.
Butanediyl-α, ω-bis-(dialkyldodecyl-ammonium bromides) (alkyl = methyl, ethyl, and propyl), which referred to as C12(n)-4-C12(n)·2Br (n=1, 2, 3), had been synthesized. The results studied by dilution method showed that a part of n-hexanol in n-heptane together with surfactant constructed a mixed film, which improved the molecular geometry of the mixed components and resulted in the formation of W/O microemulsion. The size of the water pool enlarged with increasing water content W0, which decreased the surface curvature of the water pool and therefore reduced the requirement for n-hexanol in the mixed film. With increasing the head-group size of C12(n)-4-C12(n)·2Br, i.e. n from 1 to 2, the mole ratio of n-hexanol at the film to surfactant a increased, and then decreased with further increasing n from 2 to 3. At W0=10 and 20, the radius of water pool RW reduced with increasing n, but at W0=30, RW increased considerably with increasing n from 2 to 3. These results indicated that the propyl groups linked with quaternary ammonium behaved differently from linked methyl or ethyl groups. The propyl groups may bend toward the bulk n-heptane. This unfurled the volume of the alkyl chain region of surfactant and thus decreased the requirement for n-hexanol in the film, which favored to form large water pool.
2007, 23(03): 424-428
doi: 10.3866/PKU.WHXB20070327
Abstract:
Deactivations of two different kinds of anodes during electrochemical oxidation of p-chlorophenol (p-CP) were investigated by using electrochemical measurement, and their corresponding oxidation mechanisms were also discussed. The results indicated that p-CP could be oxidized directly on both the Pt (“I”type anode) and PTFE (polytetrafluoroethylene)-β-PbO2 (“II”type anode), however, the electro-catalytic activities of both anodes lost immediately. Electrolysis at high potential could recover the electro-catalytic activities of both anodes, and Pt needed higher potential than PTFE-β-PbO2 did. The deactivated Pt could also recover its activity by soaking it in ordinary organic solvents such as acetone, tetrahydrofuran, dimethyl sulfoxide, but deactivated PTFE-β-PbO2 could not. For Pt anode (“I”), besides the direct oxidation of p-CP, oxygen transfer reaction was the main cause for the removal of p-CP when anodic potential was higher than 2.0 V; for PTFE-β-PbO2 anode (“II”), besides the direct oxidation reaction, the oxidative reaction of hydroxyl radical became the main cause for the removal of p-CP when anodic potential was higher than 1.8 V.
2007, 23(03): 429-432
doi: 10.3866/PKU.WHXB20070328
Abstract:
Carbon nanotube-supported platinum nanoparticles (Pt-CNTs) were synthesized using glycol as a reducer and H2PtCl6 as an oxidant under microwave radiation. The CNTs was first hydroxylated in refluxing concentrated HNO3. Transmission electron microscopy was used to investigate the influence of the hydroxylation time on the amount of supported platinum on the carbon nanotubes and the effect of the amount of platinum on the morphology of Pt-CNTs. Selected area electron diffraction, X-ray diffraction, and UV-visible spectroscopy were employed to characterize the structure of the Pt-CNTs and the results showed that Pt was of polycrystal nanoparticles. Cyclic voltammetric study indicated that the CNTs surface was covered by a compact layer of Pt when the loadings of platinum to CNTs was as high as 0.1875 mmol·g-1. The result, on one hand, showed that cyclic voltammetry could be used to study the surface structure and properties of CNTs supported platinum nanoparticles, and on the other hand, indicated that it was possible to obtain novel electrode materials with od catalytic activity and stability by optimizing the synthesizing method for CNTs supported platinum nanoparticles.
Carbon nanotube-supported platinum nanoparticles (Pt-CNTs) were synthesized using glycol as a reducer and H2PtCl6 as an oxidant under microwave radiation. The CNTs was first hydroxylated in refluxing concentrated HNO3. Transmission electron microscopy was used to investigate the influence of the hydroxylation time on the amount of supported platinum on the carbon nanotubes and the effect of the amount of platinum on the morphology of Pt-CNTs. Selected area electron diffraction, X-ray diffraction, and UV-visible spectroscopy were employed to characterize the structure of the Pt-CNTs and the results showed that Pt was of polycrystal nanoparticles. Cyclic voltammetric study indicated that the CNTs surface was covered by a compact layer of Pt when the loadings of platinum to CNTs was as high as 0.1875 mmol·g-1. The result, on one hand, showed that cyclic voltammetry could be used to study the surface structure and properties of CNTs supported platinum nanoparticles, and on the other hand, indicated that it was possible to obtain novel electrode materials with od catalytic activity and stability by optimizing the synthesizing method for CNTs supported platinum nanoparticles.
2007, 23(03): 433-437
doi: 10.3866/PKU.WHXB20070329
Abstract:
Rhombic magnesia flakes with multi interspaces were prepared by calcining magnesium hydrate. The precursor of M could be obtained via acid immersing twice and ammonia depositing from dolomites. The structure, morphology, and composition of M and its precursor were characterized by means of XRD, FT-IR, SEM, and TEM methods. The results indicated that EDTA and PEG molecules were possessed of the effect directing the radial epitaxial growth of Mg(OH)2 flakes. The rhombic magnesia nanoflakes with 10-20 nm in thickness and up to 1 μm2 in area of main surface are single crystal with cubic crystal structure. It grows with a preferred orientation along the [100] direction and inherits the features of radial epitaxial growth of Mg(OH)2. The orientated growth mechanism of the M nanoflakes was studied based on corresponding thermodynamics and dynamics theories.
Rhombic magnesia flakes with multi interspaces were prepared by calcining magnesium hydrate. The precursor of M could be obtained via acid immersing twice and ammonia depositing from dolomites. The structure, morphology, and composition of M and its precursor were characterized by means of XRD, FT-IR, SEM, and TEM methods. The results indicated that EDTA and PEG molecules were possessed of the effect directing the radial epitaxial growth of Mg(OH)2 flakes. The rhombic magnesia nanoflakes with 10-20 nm in thickness and up to 1 μm2 in area of main surface are single crystal with cubic crystal structure. It grows with a preferred orientation along the [100] direction and inherits the features of radial epitaxial growth of Mg(OH)2. The orientated growth mechanism of the M nanoflakes was studied based on corresponding thermodynamics and dynamics theories.
2007, 23(03): 438-446
doi: 10.3866/PKU.WHXB20070330
Abstract:
The basic concepts and species of the intelligent hydrogel and the responsive behaviors of the intelligent polymers to the changes of surrounding temperature, pH, and light signal were introduced in this paper on the basis of some successful samples. The applications of the intelligent polymers were described in the fields of farming-forest and sanitation, and the future development for these materials was prospected.
The basic concepts and species of the intelligent hydrogel and the responsive behaviors of the intelligent polymers to the changes of surrounding temperature, pH, and light signal were introduced in this paper on the basis of some successful samples. The applications of the intelligent polymers were described in the fields of farming-forest and sanitation, and the future development for these materials was prospected.
2007, 23(03): 447-454
doi: 10.3866/PKU.WHXB20070331
Abstract:
