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2007 Volume 23 Issue 12
2007, 23(12):
Abstract:
2007, 23(12): 1827-1830
doi: 10.1016/S1872-1508(07)60085-0
Abstract:
The feasibility of controlled protein immobilization via DNA conjugation by utilizing laminar flow in a microfluidic device was demonstrated. The glass surface in a microchannel was treated by oli nucleotides. The laminar flow brought different protein-DNA conjugates parallel into the microchannel. DNA recognition allows proteins to be delivered to the desired location. The total internal reflection fluorescence was also applied to monitor the process. Both the specificity and sensitivity were high, and the immobilization and removal of the proteins were repeatable. It was shown that with parallel detection of specific and non-specific recognitions, the accuracy of bio-assay would be effectively enhanced. This strategy could improve the performing quality of biosensors in microfluidic devices.
2007, 23(12): 1831-1838
doi: 10.1016/S1872-1508(07)60086-2
Abstract:
A scheme of time-dependent density functional theory (TDDFT) combined with single-excitation configuration interaction (CIS) approach was employed to make a detailed investigation of the emitting energy for fifteen well-known coumarin derivatives. The results showed that the predicted emitting energies as well as the absorption ones were dominated mainly by the exchange-correlation (XC) functional to be used. So long as a functional is properly chosen, the experimental emitting energy of most derivatives can be accurately reproduced within 0.16 eV by a calculation at the TDDFT/6-31G(d)//CIS/3-21G(d) theoretical level. It was found that, nevertheless, the hybrid functional, B3LYP, well predicted the absorption energies for all the fifteen coumarin derivatives but none of the functionals could work equally well for the emitting energy calculations. Two pure functionals, OLYP and BLYP, yield od emitting energies for the 7-aminocoumarins or derivatives with a N atom connected to 7-position, which exhibit inconspicuous charge transfer (CT) in their excited states, whereas the B3LYP hybrid functional, with 20% Hartree-Fock (HF) exchange energy, performs significantly better than OLYP and BLYP for those 3-substituted coumarins with larger CT in excited states. Thus, in comparison with the absorption energies, the selection of proper functionals for the emitting energy calculations becomes more complex. In all probability, it is effective and doable to choose an XC-functional with alterable fraction of HF exchange energy according to the composition and structure characteristics of molecule.
A scheme of time-dependent density functional theory (TDDFT) combined with single-excitation configuration interaction (CIS) approach was employed to make a detailed investigation of the emitting energy for fifteen well-known coumarin derivatives. The results showed that the predicted emitting energies as well as the absorption ones were dominated mainly by the exchange-correlation (XC) functional to be used. So long as a functional is properly chosen, the experimental emitting energy of most derivatives can be accurately reproduced within 0.16 eV by a calculation at the TDDFT/6-31G(d)//CIS/3-21G(d) theoretical level. It was found that, nevertheless, the hybrid functional, B3LYP, well predicted the absorption energies for all the fifteen coumarin derivatives but none of the functionals could work equally well for the emitting energy calculations. Two pure functionals, OLYP and BLYP, yield od emitting energies for the 7-aminocoumarins or derivatives with a N atom connected to 7-position, which exhibit inconspicuous charge transfer (CT) in their excited states, whereas the B3LYP hybrid functional, with 20% Hartree-Fock (HF) exchange energy, performs significantly better than OLYP and BLYP for those 3-substituted coumarins with larger CT in excited states. Thus, in comparison with the absorption energies, the selection of proper functionals for the emitting energy calculations becomes more complex. In all probability, it is effective and doable to choose an XC-functional with alterable fraction of HF exchange energy according to the composition and structure characteristics of molecule.
2007, 23(12): 1839-1845
doi: 10.1016/S1872-1508(07)60087-4
Abstract:
A novel fluorescent sensing film was developed by covalently attaching pyrene moieties onto a glass plate surface via triethylenetetramine in a self-assembled monolayer manner. Fluorescence measurements demonstrated that the emission of the filmcould be quenched by organic copper (II) salts, including copper acetate, copper tartrate, and copper citrate, with high selectivity and sensitivity, and the response of the film to Cu (Ac)2 is fully reversible. In contrast, the presence of inorganic copper salts, such as Cu(NO3)2, CuSO4, and CuCl2, showed lower quenching efficiency. The sensing performance of the filmto Cu(Ac)2 is slightly influenced by other divalentmetal acetates, including Zn(Ac)2, Pb(Ac)2, Co(Ac)2, and Ni(Ac)2. Furthermore, the quenching of Cu(Ac)2 to the emission of the filmis static in nature.
A novel fluorescent sensing film was developed by covalently attaching pyrene moieties onto a glass plate surface via triethylenetetramine in a self-assembled monolayer manner. Fluorescence measurements demonstrated that the emission of the filmcould be quenched by organic copper (II) salts, including copper acetate, copper tartrate, and copper citrate, with high selectivity and sensitivity, and the response of the film to Cu (Ac)2 is fully reversible. In contrast, the presence of inorganic copper salts, such as Cu(NO3)2, CuSO4, and CuCl2, showed lower quenching efficiency. The sensing performance of the filmto Cu(Ac)2 is slightly influenced by other divalentmetal acetates, including Zn(Ac)2, Pb(Ac)2, Co(Ac)2, and Ni(Ac)2. Furthermore, the quenching of Cu(Ac)2 to the emission of the filmis static in nature.
2007, 23(12): 1846-1850
doi: 10.1016/S1872-1508(07)60088-6
Abstract:
With p-N,N-dimethylaminobenzonitrile (DMABN) as a probe, the variations of the intensity of its second fluorescence emission (Ia) and the corresponding characteristic wavelength (λa) with the surfactant concentration (c), here the examined surfactants (C12TABr, SDS, C12E23, and C12-3-C12·2Br), were measured by Hitachi F4500 fluorescence spectrophotometer. The results showed that both the break point on the Ia-c curve and the minimum of the derivative variation corresponding to the λa-c curve agreed very well with the critical micelle concentration (cmc) of the surfactant in aqueous solution as measured by surface tension technique. Due to strong aggregation of C12-3-C12·2Br in aqueous solution, the information about loose micellar structure could be obtained by its λa-c curve.
With p-N,N-dimethylaminobenzonitrile (DMABN) as a probe, the variations of the intensity of its second fluorescence emission (Ia) and the corresponding characteristic wavelength (λa) with the surfactant concentration (c), here the examined surfactants (C12TABr, SDS, C12E23, and C12-3-C12·2Br), were measured by Hitachi F4500 fluorescence spectrophotometer. The results showed that both the break point on the Ia-c curve and the minimum of the derivative variation corresponding to the λa-c curve agreed very well with the critical micelle concentration (cmc) of the surfactant in aqueous solution as measured by surface tension technique. Due to strong aggregation of C12-3-C12·2Br in aqueous solution, the information about loose micellar structure could be obtained by its λa-c curve.
2007, 23(12): 1851-1856
doi: 10.1016/S1872-1508(07)60089-8
Abstract:
TiO2, ZrO2-TiO2, and ZrO2-TiO2-CeO2 were prepared by co-precipitation method and characterized by X-ray diffraction (XRD), specific surface area measurements (BET), temperature-programmed desorption (NH3-TPD), oxygen storage capacity (OSC), and temperature-programmed reduction (H2-TPR). The results showed that ZrO2-TiO2-CeO2 exhibited large number of surface strong acidity, possessed some oxygen storage capacity, and strong redox property. The three materials were used as supports and the monolith catalysts were prepared with 1% (w) V2O5 and 9%(w) WO3 for selective catalytic reduction (SCR) of NO with ammonia in the presence of excessive O2, and the results of catalytic activity showed that the catalyst used ZrO2-TiO2-CeO2 as support yielded nearly 100% NO conversion at 275 ℃ at a gas hourly space velocity (GHSV) of 10000 h-1, and it had the best catalytic activity and showed great potential for practical application.
TiO2, ZrO2-TiO2, and ZrO2-TiO2-CeO2 were prepared by co-precipitation method and characterized by X-ray diffraction (XRD), specific surface area measurements (BET), temperature-programmed desorption (NH3-TPD), oxygen storage capacity (OSC), and temperature-programmed reduction (H2-TPR). The results showed that ZrO2-TiO2-CeO2 exhibited large number of surface strong acidity, possessed some oxygen storage capacity, and strong redox property. The three materials were used as supports and the monolith catalysts were prepared with 1% (w) V2O5 and 9%(w) WO3 for selective catalytic reduction (SCR) of NO with ammonia in the presence of excessive O2, and the results of catalytic activity showed that the catalyst used ZrO2-TiO2-CeO2 as support yielded nearly 100% NO conversion at 275 ℃ at a gas hourly space velocity (GHSV) of 10000 h-1, and it had the best catalytic activity and showed great potential for practical application.
2007, 23(12): 1857-1863
doi: 10.1016/S1872-1508(07)60090-4
Abstract:
In recent times, as nonviral gene vectors, chitosan and its derivations have attracted many researchers’ attentions. The preparation of a novel gene vector-magnetic nanoparticle coated with a novel polymer-lysine modified chitosan (CTS-lys) is described in this article. Initially, the correlation conditions of preparing CTS-lys were optimized, and it was demonstrated that lots of amines of chitosan were modified by lysine, which was indicated by infrared spectroscopy (IR) and proton nuclear magnetic resonance (1H-NMR). Subsequently, through the coprecipitation method, the lysine modified chitosan magnetic nanospheres (CTS-lys-MNPs) were attained. The characterizations of nanospheres were measured by transmission electron microscopy (TEM), dynamic laser light scattering, vibrating samples magnetometer (VSM), and X-ray diffraction (XRD). The cytotoxicity of CTS-lys-MNPs was also investigated with U293 cells. The results indicated that the average size of nanospheres was about 100 nm, and they had narrower size distribution, od superparamagnetic property, and perfect crystallinity, and they also retained low toxicity. Additionally, the combination of DNA and CTS-lys-MNPs was observed via agarose gel electrophoresis, and the ability of complexes ofCTS-lys-MNPs andDNAcrossingblood-brain barrier (BBB) in ratswas studied by single photon emission computed tomography (SPECT). The results showed that the gene vector was a superior material, which had the ability of targeting and avoiding the caption of BBB.
In recent times, as nonviral gene vectors, chitosan and its derivations have attracted many researchers’ attentions. The preparation of a novel gene vector-magnetic nanoparticle coated with a novel polymer-lysine modified chitosan (CTS-lys) is described in this article. Initially, the correlation conditions of preparing CTS-lys were optimized, and it was demonstrated that lots of amines of chitosan were modified by lysine, which was indicated by infrared spectroscopy (IR) and proton nuclear magnetic resonance (1H-NMR). Subsequently, through the coprecipitation method, the lysine modified chitosan magnetic nanospheres (CTS-lys-MNPs) were attained. The characterizations of nanospheres were measured by transmission electron microscopy (TEM), dynamic laser light scattering, vibrating samples magnetometer (VSM), and X-ray diffraction (XRD). The cytotoxicity of CTS-lys-MNPs was also investigated with U293 cells. The results indicated that the average size of nanospheres was about 100 nm, and they had narrower size distribution, od superparamagnetic property, and perfect crystallinity, and they also retained low toxicity. Additionally, the combination of DNA and CTS-lys-MNPs was observed via agarose gel electrophoresis, and the ability of complexes ofCTS-lys-MNPs andDNAcrossingblood-brain barrier (BBB) in ratswas studied by single photon emission computed tomography (SPECT). The results showed that the gene vector was a superior material, which had the ability of targeting and avoiding the caption of BBB.
2007, 23(12): 1864-1868
doi: 10.3866/PKU.WHXB20071207
Abstract:
Density functional theory (DFT) was employed to investigate the dimerization of ethene over acidic zeolites with a 5T cluster model simulating zeolite. At the B3LYP/6-311+G(3df, 2p) level, the activation energy was obtained with a zero point energy (ZPE) correction. It was found that the process of the dimerization of ethene can be divided into three steps: the chemical adsorption of first ethene molecule, the physical adsorption of second ethene molecule and the dimerization reaction. The reaction proceeds by ethene chemical adsorption to form the surface ethoxide and the C—C bond formation between the ethoxide and the second ethene molecule to form the butoxide product. The calculated reaction energy barriers of ethene chemical adsorption and dimerization reaction are 108 and 149 kJ·mol-1, respectively. The obtained activation barrier of β-scission of 1-butene is 217 kJ·mol-1 in the reverse reaction of ethene dimerization.
Density functional theory (DFT) was employed to investigate the dimerization of ethene over acidic zeolites with a 5T cluster model simulating zeolite. At the B3LYP/6-311+G(3df, 2p) level, the activation energy was obtained with a zero point energy (ZPE) correction. It was found that the process of the dimerization of ethene can be divided into three steps: the chemical adsorption of first ethene molecule, the physical adsorption of second ethene molecule and the dimerization reaction. The reaction proceeds by ethene chemical adsorption to form the surface ethoxide and the C—C bond formation between the ethoxide and the second ethene molecule to form the butoxide product. The calculated reaction energy barriers of ethene chemical adsorption and dimerization reaction are 108 and 149 kJ·mol-1, respectively. The obtained activation barrier of β-scission of 1-butene is 217 kJ·mol-1 in the reverse reaction of ethene dimerization.
2007, 23(12): 1869-1874
doi: 10.3866/PKU.WHXB20071208
Abstract:
A pair of novel chiral tetradentate bisferrocenyl ligands [N,N’-bisferrocenylmethyl-N,N’-bis (2-hydroproxypyl)-(1R,2R)-1,2-diphenylethane-diamine(5R), N,N’-bisferrocenylmethyl-N,N’-bis(2-hydroxypropyl)-(1S,2S)-1,2-diphenylethane diamine (5S)] were synthesized fromferrocenylcarboxaldehyde (1) and chiral 1,2-diphenylethane-diamine (2R or 2S) followed by the reduction of the Schiff bases with NaBH4 and subsequent N-alkylation with 1,2-propyleneoxide. All the chiral products (3R-5S) were charactered by elemental analysis, infrared (IR), 1H nuclear magnetic resonance (1H NMR), ultraviolet-visible (UV-Vis) and solid-state circular dichroism (CD) spectra. The solid-state CDspectra reveal that the chiral characteristics of 5R (or 5S) are quite similar with 4R (or 4S) and it is also notable that there are some differences between 5R (or 5S) and 3R (or 3S).
A pair of novel chiral tetradentate bisferrocenyl ligands [N,N’-bisferrocenylmethyl-N,N’-bis (2-hydroproxypyl)-(1R,2R)-1,2-diphenylethane-diamine(5R), N,N’-bisferrocenylmethyl-N,N’-bis(2-hydroxypropyl)-(1S,2S)-1,2-diphenylethane diamine (5S)] were synthesized fromferrocenylcarboxaldehyde (1) and chiral 1,2-diphenylethane-diamine (2R or 2S) followed by the reduction of the Schiff bases with NaBH4 and subsequent N-alkylation with 1,2-propyleneoxide. All the chiral products (3R-5S) were charactered by elemental analysis, infrared (IR), 1H nuclear magnetic resonance (1H NMR), ultraviolet-visible (UV-Vis) and solid-state circular dichroism (CD) spectra. The solid-state CDspectra reveal that the chiral characteristics of 5R (or 5S) are quite similar with 4R (or 4S) and it is also notable that there are some differences between 5R (or 5S) and 3R (or 3S).
2007, 23(12): 1875-1880
doi: 10.1016/S1872-1508(07)60091-6
Abstract:
In order to study the effects of R group on Fe—Hg interactions and 31P chemical shifts, the structures of mononuclear complexes Fe(CO)3(PPh2R)2 (R=pym: 1, fur: 2, py: 3, thi: 4; pym=pyrimidine, fur=furyl, py=pyridine, thi=thiazole) and binuclear complexes [Fe(CO)3(PPh2R)2(HgCl2)] (R=pym: 5, fur: 6, py: 7, thi: 8) were studied by using the density functional theory (DFT) PBE0 method. The 31P chemical shifts were calculated by PBE0-GIAO method. Nature bond orbital (NBO) analyseswere also performed to explain the nature of the Fe—Hg interactions. The conclusions can be drawn as follows: (1) The complexes with nitrogen donor atoms are more stable than those with O or S atoms. The more N atom there are, the higher is the stabilitity of the complex. (2) The Fe—Hg interactions play a dominant role in the stabilities of the complexes. In 5 or 6, there is a σ-bond between Fe and Hg atoms, However, in 7 and 8, the Fe—Hg interations act as σP—Fe→nHg and σC—Fe→nHg delocalization. (3) Through Fe邛Hg interactions, there is charge transfer from R groups towards the P, Fe, and Hg atoms, which increases the electron density on P nucleus in binuclear complexes. As a result, compared with their mononuclear complexes, the 31P chemical shifts in binuclear complexes show some reduction.
In order to study the effects of R group on Fe—Hg interactions and 31P chemical shifts, the structures of mononuclear complexes Fe(CO)3(PPh2R)2 (R=pym: 1, fur: 2, py: 3, thi: 4; pym=pyrimidine, fur=furyl, py=pyridine, thi=thiazole) and binuclear complexes [Fe(CO)3(PPh2R)2(HgCl2)] (R=pym: 5, fur: 6, py: 7, thi: 8) were studied by using the density functional theory (DFT) PBE0 method. The 31P chemical shifts were calculated by PBE0-GIAO method. Nature bond orbital (NBO) analyseswere also performed to explain the nature of the Fe—Hg interactions. The conclusions can be drawn as follows: (1) The complexes with nitrogen donor atoms are more stable than those with O or S atoms. The more N atom there are, the higher is the stabilitity of the complex. (2) The Fe—Hg interactions play a dominant role in the stabilities of the complexes. In 5 or 6, there is a σ-bond between Fe and Hg atoms, However, in 7 and 8, the Fe—Hg interations act as σP—Fe→nHg and σC—Fe→nHg delocalization. (3) Through Fe邛Hg interactions, there is charge transfer from R groups towards the P, Fe, and Hg atoms, which increases the electron density on P nucleus in binuclear complexes. As a result, compared with their mononuclear complexes, the 31P chemical shifts in binuclear complexes show some reduction.
2007, 23(12): 1881-1885
doi: 10.3866/PKU.WHXB20071210
Abstract:
The dilational rheological properties of a pair of structural isomers: sodium 2-propyl-4,5-dihexyl benzene sulfonate (366) and sodium 2,5-dipropyl-4-nonyl benzene sulfonate(393) at the air/water and decane/water interfaces were investigated by drop shape analysis method. The influences of concentration on dilational modulus were expounded. The experimental results showed that the 5-alkyl played an important role in the surface dilational modulus, while the dimension of surfactant molecule dominated the interfacial dilatinal modulus.
The dilational rheological properties of a pair of structural isomers: sodium 2-propyl-4,5-dihexyl benzene sulfonate (366) and sodium 2,5-dipropyl-4-nonyl benzene sulfonate(393) at the air/water and decane/water interfaces were investigated by drop shape analysis method. The influences of concentration on dilational modulus were expounded. The experimental results showed that the 5-alkyl played an important role in the surface dilational modulus, while the dimension of surfactant molecule dominated the interfacial dilatinal modulus.
2007, 23(12): 1886-1892
doi: 10.3866/PKU.WHXB20071211
Abstract:
A highly ordered Fe-doped TiO2 nanotube layer was fabricated by potentiostatic anodization of pure titaniumin fluorinated electrolyte solutions containing iron ions. The structure and composition of the as-prepared TiO2 nanotubes were characterized by SEM, XRD, UV-Vis, and XPS. The effects of temperature, time, dopant content on the morphologies, structure and photochemical properties of the TiO2 nanotube arrays were investigated systemically. The performances of photogenerated cathodic protection and the photoelectrochemical response for the Fe-doped TiO2 nanotube layers under illumination and dark conditions were evaluated through the electrochemical measurements. It was found that Fe ions in the TiO2 nanotube arrays could suppress the recombination of photogenerated hole-electron. The Fe-doped TiO2 nanotubes showed a stronger absorption in the 410-650 nm range. The open-circuit potentials of 316LSS (stainless steel) coupled with the Fe-doped TiO2 nanotubes layers shifted negatively under visible light irradiation (λ>400 nm), and maintained negatively for a period even in dark condition. It was indicated that the Fe-doped TiO2 nanotubes layers were able to create effectively a photogenerated cathodic protection for metals under regular sunlight conditions.
A highly ordered Fe-doped TiO2 nanotube layer was fabricated by potentiostatic anodization of pure titaniumin fluorinated electrolyte solutions containing iron ions. The structure and composition of the as-prepared TiO2 nanotubes were characterized by SEM, XRD, UV-Vis, and XPS. The effects of temperature, time, dopant content on the morphologies, structure and photochemical properties of the TiO2 nanotube arrays were investigated systemically. The performances of photogenerated cathodic protection and the photoelectrochemical response for the Fe-doped TiO2 nanotube layers under illumination and dark conditions were evaluated through the electrochemical measurements. It was found that Fe ions in the TiO2 nanotube arrays could suppress the recombination of photogenerated hole-electron. The Fe-doped TiO2 nanotubes showed a stronger absorption in the 410-650 nm range. The open-circuit potentials of 316LSS (stainless steel) coupled with the Fe-doped TiO2 nanotubes layers shifted negatively under visible light irradiation (λ>400 nm), and maintained negatively for a period even in dark condition. It was indicated that the Fe-doped TiO2 nanotubes layers were able to create effectively a photogenerated cathodic protection for metals under regular sunlight conditions.
2007, 23(12): 1893-1898
doi: 10.3866/PKU.WHXB20071212
Abstract:
In order to solve the difficulty in separating powdery 4A zeolite from solution in application of 4A zeolite, a series of magnetic 4A zeolites with different Fe3O4 contents were synthesized by traditional hydrothermal method through ultrasonic crystallization for 6 h at 70 ℃ after adding magnetic Fe3O4 particulates to the crystallization solution for 4A zeolite synthesis. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), IR, magnetic susceptibility, TG/DTA, EDX and ion exchange capability. The results showed that the magnetic 4A zeolite had od magnetism and its magnetic susceptibility increased with the Fe3O4 amount increasing. For adsorption of F- and Cr (VI) in water, the adsorption capability of magnetic 4A zeolite is equal with the pure 4A zeolite and the adsorption rate filled well the pseudo-second-order rate model.
In order to solve the difficulty in separating powdery 4A zeolite from solution in application of 4A zeolite, a series of magnetic 4A zeolites with different Fe3O4 contents were synthesized by traditional hydrothermal method through ultrasonic crystallization for 6 h at 70 ℃ after adding magnetic Fe3O4 particulates to the crystallization solution for 4A zeolite synthesis. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), IR, magnetic susceptibility, TG/DTA, EDX and ion exchange capability. The results showed that the magnetic 4A zeolite had od magnetism and its magnetic susceptibility increased with the Fe3O4 amount increasing. For adsorption of F- and Cr (VI) in water, the adsorption capability of magnetic 4A zeolite is equal with the pure 4A zeolite and the adsorption rate filled well the pseudo-second-order rate model.
2007, 23(12): 1899-1904
doi: 10.3866/PKU.WHXB20071213
Abstract:
The photocatalyst (DPPBI/Pt/TiO2)was prepared using N,N’-di(4-pyridyl)-3,4,9,10-perylene tetracarboxylic acid bisimide (DPPBI) sensitized Pt/TiO2 and characterized by infrared spectroscopy(IR), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS), and X-ray diffraction (XRD). The results of characterizationshowedthat the crystal form of TiO2was anatase, Ptwas highly dispersed on the surface of TiO2 and DPPBI was adsorbed on the surface of Pt/TiO2 in DPPBI/Pt/TiO2. Hydrogen production from water splitting using photocatalyst (DPPBI/Pt/TiO2) was studied. It has been found that the rate of hydrogen evolution reaches 6.69 滋 mol·h-1·g-1 under visible light irradiation for 8 h with 300 W Xe-lamp cold light source when 250 mL reactive liquid contains 0.8 g·L-1 photocatalyst (0.1%DPPBI/0.4%Pt/TiO2) and 0.2 mol·L-1 KI.
The photocatalyst (DPPBI/Pt/TiO2)was prepared using N,N’-di(4-pyridyl)-3,4,9,10-perylene tetracarboxylic acid bisimide (DPPBI) sensitized Pt/TiO2 and characterized by infrared spectroscopy(IR), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS), and X-ray diffraction (XRD). The results of characterizationshowedthat the crystal form of TiO2was anatase, Ptwas highly dispersed on the surface of TiO2 and DPPBI was adsorbed on the surface of Pt/TiO2 in DPPBI/Pt/TiO2. Hydrogen production from water splitting using photocatalyst (DPPBI/Pt/TiO2) was studied. It has been found that the rate of hydrogen evolution reaches 6.69 滋 mol·h-1·g-1 under visible light irradiation for 8 h with 300 W Xe-lamp cold light source when 250 mL reactive liquid contains 0.8 g·L-1 photocatalyst (0.1%DPPBI/0.4%Pt/TiO2) and 0.2 mol·L-1 KI.
2007, 23(12): 1905-1911
doi: 10.3866/PKU.WHXB20071214
Abstract:
The functional composite-type particle PMAA/SiO2, which was prepared by grafting polymethacrylic acid (PMAA) onto the surface of silica gel particles (SiO2), was used as solid adsorbent, and the static adsorption experiments for pirimicarb in water were performed. The adsorption mechanism of PMAA/SiO2 for pirimicarb in water was mainly studied via examining the effects of various factors, such as pH value, concentration of sodium chloride (NaCl) and temperature on the adsorption capacity. In order to confirm further the adsorption mechanism put forward, the interaction between the monomer methacrylic acid and pirimicarb was investigated by using UV spectral absorption method. The adsorption behaviour of PMAA/SiO2 for pirimicarb in carbon tetrachloride (CCl4) was also studied. The experimental results showed that the functional composite-type particle PMAA/SiO2 had strong adsorption ability for pirimicarb. The driving force of the adsorption was the synergism of electrostatic, hydrogen bond and hydrophobic interactions. Among them, the electrostatic interaction was the main driving force. The adsorption capacity decreases with the enhancement of temperature; as salinity of the solution increases, the adsorption capacity decreases; when pH<8, the adsorption capacity increases with the increase of pH value, decreases with the increase of pH value as pH>8, and when pH=8, the adsorption capacity has a maximum.
The functional composite-type particle PMAA/SiO2, which was prepared by grafting polymethacrylic acid (PMAA) onto the surface of silica gel particles (SiO2), was used as solid adsorbent, and the static adsorption experiments for pirimicarb in water were performed. The adsorption mechanism of PMAA/SiO2 for pirimicarb in water was mainly studied via examining the effects of various factors, such as pH value, concentration of sodium chloride (NaCl) and temperature on the adsorption capacity. In order to confirm further the adsorption mechanism put forward, the interaction between the monomer methacrylic acid and pirimicarb was investigated by using UV spectral absorption method. The adsorption behaviour of PMAA/SiO2 for pirimicarb in carbon tetrachloride (CCl4) was also studied. The experimental results showed that the functional composite-type particle PMAA/SiO2 had strong adsorption ability for pirimicarb. The driving force of the adsorption was the synergism of electrostatic, hydrogen bond and hydrophobic interactions. Among them, the electrostatic interaction was the main driving force. The adsorption capacity decreases with the enhancement of temperature; as salinity of the solution increases, the adsorption capacity decreases; when pH<8, the adsorption capacity increases with the increase of pH value, decreases with the increase of pH value as pH>8, and when pH=8, the adsorption capacity has a maximum.
2007, 23(12): 1912-1916
doi: 10.3866/PKU.WHXB20071215
Abstract:
The diffusion of hydrogen in corundum was simulated using pseudopotential plane wave method which was based on the density functional theory(DFT) with the generalized gradient approximation(GGA) to the exchange-correlation energy. The hydrogen permeation resistance and micromechanism were studied by searching the transition state and diffusion route, and gained diffusion coefficient of hydrogen by applying dynamic calculations. The activation energy was 1.59 eVand the diffusion coefficient of hydrogen was D(T)=(3.37×10-7)exp(-1.59/kT). Analyzing the calculation results, it showed that the structure in which H atom occupied empty interstitial of α-Al2O3 was more stable. H diffusion was impossible at low temperature and occured along the empty interstitials at high temperature.
The diffusion of hydrogen in corundum was simulated using pseudopotential plane wave method which was based on the density functional theory(DFT) with the generalized gradient approximation(GGA) to the exchange-correlation energy. The hydrogen permeation resistance and micromechanism were studied by searching the transition state and diffusion route, and gained diffusion coefficient of hydrogen by applying dynamic calculations. The activation energy was 1.59 eVand the diffusion coefficient of hydrogen was D(T)=(3.37×10-7)exp(-1.59/kT). Analyzing the calculation results, it showed that the structure in which H atom occupied empty interstitial of α-Al2O3 was more stable. H diffusion was impossible at low temperature and occured along the empty interstitials at high temperature.
2007, 23(12): 1917-1921
doi: 10.3866/PKU.WHXB20071216
Abstract:
The rutile TiO2 catalysts with oxygen vacancies were obtained under 927 ℃calcination using a mixed gas of saturation water vapor and H2 at 69 ℃. The catalysts were identified using X-ray diffraction (XRD), specific surface (BET), electron paramagnetic resonance spectroscopy (EPR), UV-Vis diffuse refraction spectroscopy (DRS), and X-ray photoelectron spectrum (XPS) measurements. The effect of calcination time on photocatalytic activity of TiO2 with different oxygen vacancies for O2 evolution was studied. The result indicated that appropriate oxygen vacancies could obviously improve the photocatalytic activity of rutile TiO2. The maximumO2 evolution speed of rutile TiO2 with oxygen vacancies was 222 μmol·L-1·h-1.
The rutile TiO2 catalysts with oxygen vacancies were obtained under 927 ℃calcination using a mixed gas of saturation water vapor and H2 at 69 ℃. The catalysts were identified using X-ray diffraction (XRD), specific surface (BET), electron paramagnetic resonance spectroscopy (EPR), UV-Vis diffuse refraction spectroscopy (DRS), and X-ray photoelectron spectrum (XPS) measurements. The effect of calcination time on photocatalytic activity of TiO2 with different oxygen vacancies for O2 evolution was studied. The result indicated that appropriate oxygen vacancies could obviously improve the photocatalytic activity of rutile TiO2. The maximumO2 evolution speed of rutile TiO2 with oxygen vacancies was 222 μmol·L-1·h-1.
2007, 23(12): 1922-1926
doi: 10.3866/PKU.WHXB20071217
Abstract:
A novel kind of PVDF-HFP(polyvinylidene fluoride-hexafluoropro-pylene)-based polymer electrolyte composite membrane for lithium-ion battery was prepared. Inorganic TiO2 nanopowders in composite were dealt with solid super-acidization. Series of characterizations were carried on, such as surface acid strength H0, XRD analysis, electrolyte absorbency, and electrochemical impedance spectroscopy. PE non-woven fabrics were introduced as the reinforced materials, which were soaked to prepare the composite membranes, and then assembled to get the resulted lithium-ion battery. Performance tests indicated that the lithium-ion battery had od electrochemical performance.
A novel kind of PVDF-HFP(polyvinylidene fluoride-hexafluoropro-pylene)-based polymer electrolyte composite membrane for lithium-ion battery was prepared. Inorganic TiO2 nanopowders in composite were dealt with solid super-acidization. Series of characterizations were carried on, such as surface acid strength H0, XRD analysis, electrolyte absorbency, and electrochemical impedance spectroscopy. PE non-woven fabrics were introduced as the reinforced materials, which were soaked to prepare the composite membranes, and then assembled to get the resulted lithium-ion battery. Performance tests indicated that the lithium-ion battery had od electrochemical performance.
2007, 23(12): 1927-1931
doi: 10.3866/PKU.WHXB20071218
Abstract:
Ni0.45Co0.1Mn0.45(OH)2was prepared via improved hydroxide co-precipitation. The effect of reaction condition on the shape of the product, and the effect of F- ion on the morphology and tap-density of the product were studied. LiMn0.45Ni0.45Co0.1O2 and LiMn0.45Ni0.45Co0.1O1.96F0.04 were prepared by mixing this metal hydroxide with 5% excess LiOH followed by heat-treatment. The effect of F doping on the cycling performance of the prodct was investigated. The morphology and tap-density of the product were improved through the addition of F- in co-precipitation system. The product was characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and charge-discharge tests. It can be seen from the SEMresults that the product has a od shape. The XRD studies showed that the material had a well-ordered layered structure without impurity phase. The initial capacities of both LiMn0.45Ni0.45Co0.1O2 and LiMn0.45Ni0.45Co0.1O1.96F0.04 are 157 mAh·g-1 at a charging potential between 2.8 and 4.4 V and a current density of 30 mA·g -1. The 72.6% and 86.0% discharge capacities were retained at the end of 50 charge-discharge cycles, respectively. It is shown that the F doping can obviously improve the cycling performance of the product.
Ni0.45Co0.1Mn0.45(OH)2was prepared via improved hydroxide co-precipitation. The effect of reaction condition on the shape of the product, and the effect of F- ion on the morphology and tap-density of the product were studied. LiMn0.45Ni0.45Co0.1O2 and LiMn0.45Ni0.45Co0.1O1.96F0.04 were prepared by mixing this metal hydroxide with 5% excess LiOH followed by heat-treatment. The effect of F doping on the cycling performance of the prodct was investigated. The morphology and tap-density of the product were improved through the addition of F- in co-precipitation system. The product was characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and charge-discharge tests. It can be seen from the SEMresults that the product has a od shape. The XRD studies showed that the material had a well-ordered layered structure without impurity phase. The initial capacities of both LiMn0.45Ni0.45Co0.1O2 and LiMn0.45Ni0.45Co0.1O1.96F0.04 are 157 mAh·g-1 at a charging potential between 2.8 and 4.4 V and a current density of 30 mA·g -1. The 72.6% and 86.0% discharge capacities were retained at the end of 50 charge-discharge cycles, respectively. It is shown that the F doping can obviously improve the cycling performance of the product.
2007, 23(12): 1932-1936
doi: 10.3866/PKU.WHXB20071219
Abstract:
The gel polymer electrolyte (GPE) based on PVDF-HFP and NPGDA network was prepared via γ-ray irradiation method. The structure, thermal stability and electrochemical performace of the GPE effected by irratiation dose were examined. The relationship between ionic conductivity and temperature followed Vogel-Tamman-Fulcher (VTF) equation, which suggested amorphous regions being dominant in GPE. The GPE irradiated at 5 kGy exhibited electrochemical stability up to 4.7 V vs Li/Li+ and high conductivity of 7.8×10-3 S·cm-1 at 25 ℃. In situ prepared LiMn2O4∣GPE∣Li cells exhibited od cycle performance, which provided a new approach to the fabrication of lithium-ion polymer batteries (LiPBs).
The gel polymer electrolyte (GPE) based on PVDF-HFP and NPGDA network was prepared via γ-ray irradiation method. The structure, thermal stability and electrochemical performace of the GPE effected by irratiation dose were examined. The relationship between ionic conductivity and temperature followed Vogel-Tamman-Fulcher (VTF) equation, which suggested amorphous regions being dominant in GPE. The GPE irradiated at 5 kGy exhibited electrochemical stability up to 4.7 V vs Li/Li+ and high conductivity of 7.8×10-3 S·cm-1 at 25 ℃. In situ prepared LiMn2O4∣GPE∣Li cells exhibited od cycle performance, which provided a new approach to the fabrication of lithium-ion polymer batteries (LiPBs).
2007, 23(12): 1937-1942
doi: 10.3866/PKU.WHXB20071220
Abstract:
A novel three-dimensional composite anode was prepared by using three-dimensional copper foil with micro-holes for collector and nano-Sn/SnSb alloys powders for active materials. The nano-Sn/SnSb alloys were synthesized by liquid chemical reduction methods at low temperature and the collector was obtained via multiple-step electrodeposition. Advantages of the new three-dimensional composite anode were investigated by comparing its electrochemical performance with that of normal planar anode: three-dimensional structure of the electrode enhanced the combination between active materials and the collector, which increased the possibility for the preparation of anode without binder; the novel anode effectively buffered the volume expansion of high capability active materials during charge/discharge cycles and therefore increased the capacity retention of the electrode. Compared to 33%of the initial charge capacity of normal anode after 30 cycles, the capacity retention of three-dimensional composite anode was 41% of the initial charge capacity; special structure provided a well environment for transferring charge, which made the process of the reaction more complete and therefore higher capacity. The initial specific charge capacity of normal anode was 480 mAh·g-1 and that of three-dimensional composite anode achieved 800 mAh·g-1. The advantages and attractive electrochemical performance of the three-dimensional nano-Sn/SnSb composite anode provide a new thought for structure design and development of anode for lithiumion battery.
A novel three-dimensional composite anode was prepared by using three-dimensional copper foil with micro-holes for collector and nano-Sn/SnSb alloys powders for active materials. The nano-Sn/SnSb alloys were synthesized by liquid chemical reduction methods at low temperature and the collector was obtained via multiple-step electrodeposition. Advantages of the new three-dimensional composite anode were investigated by comparing its electrochemical performance with that of normal planar anode: three-dimensional structure of the electrode enhanced the combination between active materials and the collector, which increased the possibility for the preparation of anode without binder; the novel anode effectively buffered the volume expansion of high capability active materials during charge/discharge cycles and therefore increased the capacity retention of the electrode. Compared to 33%of the initial charge capacity of normal anode after 30 cycles, the capacity retention of three-dimensional composite anode was 41% of the initial charge capacity; special structure provided a well environment for transferring charge, which made the process of the reaction more complete and therefore higher capacity. The initial specific charge capacity of normal anode was 480 mAh·g-1 and that of three-dimensional composite anode achieved 800 mAh·g-1. The advantages and attractive electrochemical performance of the three-dimensional nano-Sn/SnSb composite anode provide a new thought for structure design and development of anode for lithiumion battery.
2007, 23(12): 1943-1947
doi: 10.3866/PKU.WHXB20071221
Abstract:
The ternary copolymer of acrylonitrile (AN), methoxy polyethylene glycol (350) monoacrylate (MPGA), and lithiumacrylate (LiAc) which can be used as gel electrolyte for lithiumion batteries was prepared by radical emulsion polymerization. This improved the solubility of poly(acrylonitrile-methoxy polyethylene glycol (350) monoacrylate), and meanwhile, decreased the contraction of the membrane made from the polymer. The solubility of the ternary copolymer and the contraction of the prepared microporous membrane by phase-inversion methods were improved by way of copolymerization. Several products were characterized by infrared (IR) absorption spectroscopy and differential scanning calorimetry (DSC). The ionic conductivity of the gel electrolyte membrane at ambient temperature was tested by AC impedance. The results showed that the as-prepared gel copolymer electrolyte microporous membranes had higher ionic conductivity and were promising materials for lithiumion batteries.
The ternary copolymer of acrylonitrile (AN), methoxy polyethylene glycol (350) monoacrylate (MPGA), and lithiumacrylate (LiAc) which can be used as gel electrolyte for lithiumion batteries was prepared by radical emulsion polymerization. This improved the solubility of poly(acrylonitrile-methoxy polyethylene glycol (350) monoacrylate), and meanwhile, decreased the contraction of the membrane made from the polymer. The solubility of the ternary copolymer and the contraction of the prepared microporous membrane by phase-inversion methods were improved by way of copolymerization. Several products were characterized by infrared (IR) absorption spectroscopy and differential scanning calorimetry (DSC). The ionic conductivity of the gel electrolyte membrane at ambient temperature was tested by AC impedance. The results showed that the as-prepared gel copolymer electrolyte microporous membranes had higher ionic conductivity and were promising materials for lithiumion batteries.
2007, 23(12): 1948-1953
doi: 10.3866/PKU.WHXB20071222
Abstract:
LiCoO2 samples were synthesized by high temperature solid-state reaction method, characterized by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The reflection and transmission XRDdata of different commercial LiCoO2 materials proved that the intensity ratio of (104) to (003) (I(104)/I(003)) reflects the degree of crystal orientation, not the order of Li and Co positions in LiCoO2 crystals. The higher the crystal orientation degree was, the smaller the ratio I(104)/I(003) would be. Experimental data also indicated this ratio value should be about 95%for the LiCoO2 crystals with no preferred orientations. Therefore, the intensity ratio I(104)/I(003) can not be considered as the main evidence for the position order of Li and Co in LiCoO2 crystals. The confusion on the intensity ratios of XRD peaks of cathode material LiCoO2 for Li-ion batteries was clarified.
LiCoO2 samples were synthesized by high temperature solid-state reaction method, characterized by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The reflection and transmission XRDdata of different commercial LiCoO2 materials proved that the intensity ratio of (104) to (003) (I(104)/I(003)) reflects the degree of crystal orientation, not the order of Li and Co positions in LiCoO2 crystals. The higher the crystal orientation degree was, the smaller the ratio I(104)/I(003) would be. Experimental data also indicated this ratio value should be about 95%for the LiCoO2 crystals with no preferred orientations. Therefore, the intensity ratio I(104)/I(003) can not be considered as the main evidence for the position order of Li and Co in LiCoO2 crystals. The confusion on the intensity ratios of XRD peaks of cathode material LiCoO2 for Li-ion batteries was clarified.
2007, 23(12): 1954-1957
doi: 10.3866/PKU.WHXB20071223
Abstract:
A novel cathode material lithium vanadium phosphate with the microstructure of submicro-particles aggregate was synthesized by liquid-phase sphericizing granulation. XRD pattern showed that the crystal structure of Li3V2(PO4)3 was monoclinic and belonged to P21/n space group. SEM revealed that the diameters of the particle and aggregated particle were in submicron range and about 10 滋m, respectively, with a narrowdistribution. The electrochemical testing showed that the obtained Li3V2(PO4)3 had the maximum discharge capacity of 126.67 mAh·g-1 and initial coulombic efficiency of 95.6%in the range of 3.0-4.3 V (vs Li/Li+), and 170.47mAh·g-1 and 97.5%in the range of 3.0-4.9 V (vs Li/Li+) at a density of 55.6 mA·g-1, respectively. Moreover, the material had a better cycle stability.
A novel cathode material lithium vanadium phosphate with the microstructure of submicro-particles aggregate was synthesized by liquid-phase sphericizing granulation. XRD pattern showed that the crystal structure of Li3V2(PO4)3 was monoclinic and belonged to P21/n space group. SEM revealed that the diameters of the particle and aggregated particle were in submicron range and about 10 滋m, respectively, with a narrowdistribution. The electrochemical testing showed that the obtained Li3V2(PO4)3 had the maximum discharge capacity of 126.67 mAh·g-1 and initial coulombic efficiency of 95.6%in the range of 3.0-4.3 V (vs Li/Li+), and 170.47mAh·g-1 and 97.5%in the range of 3.0-4.9 V (vs Li/Li+) at a density of 55.6 mA·g-1, respectively. Moreover, the material had a better cycle stability.
2007, 23(12): 1958-1962
doi: 10.3866/PKU.WHXB20071224
Abstract:
The monodispersed magnetic Fe3O4 hollow submicro-spheres were prepared by directly pyrolyzing the P(St-co-AA)/Fe2O3 core-shell particles in nitrogen, which were obtained by controlled hydrolysis of FeCl3 on the surface of template particles. The structure, composition and magnetic properties of those hollow spheres were examined by transmission electron microscopy(TEM), field emission scanning electron microscopy(FESEM), X-ray diffraction(XRD) and vibrating sample magnetometer(VSM) etc. The results showed that the monodispersed Fe3O4 hollow submicro-spheres with even and compact shells were produced since the Fe2O3 shells were deoxidized into Fe3O4 by the pyrolysates decomposed from the polymer cores during heat-treatment in nitrogen gas. The Fe3O4 hollow particles showed saturated magnetization of 50.91 A·m2·kg -1, remaining magnetization of 3.97 A·m2·kg -1 and coercivity of 2.33 kA·m-1 at roomtemperature.
The monodispersed magnetic Fe3O4 hollow submicro-spheres were prepared by directly pyrolyzing the P(St-co-AA)/Fe2O3 core-shell particles in nitrogen, which were obtained by controlled hydrolysis of FeCl3 on the surface of template particles. The structure, composition and magnetic properties of those hollow spheres were examined by transmission electron microscopy(TEM), field emission scanning electron microscopy(FESEM), X-ray diffraction(XRD) and vibrating sample magnetometer(VSM) etc. The results showed that the monodispersed Fe3O4 hollow submicro-spheres with even and compact shells were produced since the Fe2O3 shells were deoxidized into Fe3O4 by the pyrolysates decomposed from the polymer cores during heat-treatment in nitrogen gas. The Fe3O4 hollow particles showed saturated magnetization of 50.91 A·m2·kg -1, remaining magnetization of 3.97 A·m2·kg -1 and coercivity of 2.33 kA·m-1 at roomtemperature.
2007, 23(12): 1963-1968
doi: 10.3866/PKU.WHXB20071225
Abstract:
The potentiodynamic scanning polarization, electrochemical impedance spectroscopy and surface analysis methods were employed to investigate the effect of pseudomonas on the corrosion behaviors of stee1 A3 in cladosporium solution. It was showed that the existence of pseudomonas affected the anodic process of steel A3 in cladosporium solution, free corrosion current (icorr) of steel A3 decreased when the two microorganisms coexisted in the culture. With exposure time increasing, from the 7th day, the impedance value of steel A3 in the mixed-colony system was greater than that in the cladosporium system, which indicated that pseudomonas had an inhibitory effect on the corrosion of steel A3. The results of SEMindicated that pitting corrosion occurred in both of the cladosporium and the pseudomonas-cladosporium mixed colony systems, but the pitting holes of steel A3 in the latter solution were smaller and shallower.
The potentiodynamic scanning polarization, electrochemical impedance spectroscopy and surface analysis methods were employed to investigate the effect of pseudomonas on the corrosion behaviors of stee1 A3 in cladosporium solution. It was showed that the existence of pseudomonas affected the anodic process of steel A3 in cladosporium solution, free corrosion current (icorr) of steel A3 decreased when the two microorganisms coexisted in the culture. With exposure time increasing, from the 7th day, the impedance value of steel A3 in the mixed-colony system was greater than that in the cladosporium system, which indicated that pseudomonas had an inhibitory effect on the corrosion of steel A3. The results of SEMindicated that pitting corrosion occurred in both of the cladosporium and the pseudomonas-cladosporium mixed colony systems, but the pitting holes of steel A3 in the latter solution were smaller and shallower.
2007, 23(12): 1969-1973
doi: 10.3866/PKU.WHXB20071226
Abstract:
Magnetic chitosan-alginate microcapsules were prepared via emulsion-gel method. Fe3O4 magnetic hollow spheres were capsulated into the microcapsules, which endowed the microcapsules with magnetic targeting properties. Cefradine was used as model drug to study the properties of the microcapsules including drug content,encapsulation efficiency, and controlled drug release. The results showed that with the increasing of initial drug concentration, the drug content increased, but the encapsulation efficiency decreased. The microcapsules exhibited sustained release of the drug in all media and the release rate could be regulated by the pH value: in simulated gastric fluid, the release rate was greatly decreased, and in simulated body fluid and intestinal fluid, the microcapsules exhibited a constant release in 50 h with different release rates. Under an external magnetic field, the microcapsules showed fine magnetic response properties, which provided possibility for magnetic targeting drug delivery.
Magnetic chitosan-alginate microcapsules were prepared via emulsion-gel method. Fe3O4 magnetic hollow spheres were capsulated into the microcapsules, which endowed the microcapsules with magnetic targeting properties. Cefradine was used as model drug to study the properties of the microcapsules including drug content,encapsulation efficiency, and controlled drug release. The results showed that with the increasing of initial drug concentration, the drug content increased, but the encapsulation efficiency decreased. The microcapsules exhibited sustained release of the drug in all media and the release rate could be regulated by the pH value: in simulated gastric fluid, the release rate was greatly decreased, and in simulated body fluid and intestinal fluid, the microcapsules exhibited a constant release in 50 h with different release rates. Under an external magnetic field, the microcapsules showed fine magnetic response properties, which provided possibility for magnetic targeting drug delivery.
2007, 23(12): 1974-1978
doi: 10.3866/PKU.WHXB20071227
Abstract:
The intermolecular complexes of BeH2 with hydrogen halides (HX(X=F, Cl, Br, I)) were examined using ab initio calculations performed at the second-order Moller-Plesset perturbation approximation with the 6-311++G(3d,3p) basis set. Dihydrogen-bonds were formed in complexes of BeH2 with hydrogen halides based on the judgement from the geometrical criteria. The characteristics of the bond critical points, the electron densities and their Laplacians, also confirmed this conclusion. The calculated binding energies of complexes of BeH2 with hydrogen halides usingMP2/6-311++G(3d, 3p) methods, corrected by the basis-set superposition error (BSSE) were -14.468 kJ·mol-1 to -5.464 kJ·mol-1. In an effort to comprehend the underlying basis of this interaction, we have also carried out a ri rous decomposition of the interaction energies using the symmetry adapted perturbational theory (SAPT) method. The results indicated that electro-static energies, induction energies, dispersion energies, and exchange-repulsion energies were all important to the total binding energies. The contribution of the induction energy to total attractive energy decreased from 37.8% in BeH2…HF complex to 24.0% in BeH2…HI complex. The dispersion energy dramatically increased from 16.0%in BeH2…HF complex to 33.8% in BeH2…HI complex.
The intermolecular complexes of BeH2 with hydrogen halides (HX(X=F, Cl, Br, I)) were examined using ab initio calculations performed at the second-order Moller-Plesset perturbation approximation with the 6-311++G(3d,3p) basis set. Dihydrogen-bonds were formed in complexes of BeH2 with hydrogen halides based on the judgement from the geometrical criteria. The characteristics of the bond critical points, the electron densities and their Laplacians, also confirmed this conclusion. The calculated binding energies of complexes of BeH2 with hydrogen halides usingMP2/6-311++G(3d, 3p) methods, corrected by the basis-set superposition error (BSSE) were -14.468 kJ·mol-1 to -5.464 kJ·mol-1. In an effort to comprehend the underlying basis of this interaction, we have also carried out a ri rous decomposition of the interaction energies using the symmetry adapted perturbational theory (SAPT) method. The results indicated that electro-static energies, induction energies, dispersion energies, and exchange-repulsion energies were all important to the total binding energies. The contribution of the induction energy to total attractive energy decreased from 37.8% in BeH2…HF complex to 24.0% in BeH2…HI complex. The dispersion energy dramatically increased from 16.0%in BeH2…HF complex to 33.8% in BeH2…HI complex.
2007, 23(12): 1979-1984
doi: 10.3866/PKU.WHXB20071228
Abstract:
Fe3O4/ chitosan magnetic microspheres of 50 to 80 滋m were prepared using the inverse phase emulsion dispersion and chemical crosslinking technology, and then modified with ethylenediamine for use in the adsorption of heavy metal ions. The adsorption properties of the modified Fe3O4/chitosan toward Cu2+, Cd2+ and Ni2+ were investigated. It was found that the adsorption capacities of Cu2+ and Ni2+ increased with pH, and a maximum adsorption for Cd2+ occurred at pH=3. The saturated adsorption capacities calculated by Langmuir isotherms were 54.3 mg·g-1 for Cu2+, 20.4 mg·g-1 for Cd2+, and 12.4 mg·g-1 for Ni2+, respectively. The adsorption kinetics were well described by pseudo-second-order equation models. The experimental results showed that the Fe3O4/chitosan modified with ethylenediamine presented higher adsorption selectivity for Cu2+ than for Cd2+ and Ni2+ in all studied pH ranges.
Fe3O4/ chitosan magnetic microspheres of 50 to 80 滋m were prepared using the inverse phase emulsion dispersion and chemical crosslinking technology, and then modified with ethylenediamine for use in the adsorption of heavy metal ions. The adsorption properties of the modified Fe3O4/chitosan toward Cu2+, Cd2+ and Ni2+ were investigated. It was found that the adsorption capacities of Cu2+ and Ni2+ increased with pH, and a maximum adsorption for Cd2+ occurred at pH=3. The saturated adsorption capacities calculated by Langmuir isotherms were 54.3 mg·g-1 for Cu2+, 20.4 mg·g-1 for Cd2+, and 12.4 mg·g-1 for Ni2+, respectively. The adsorption kinetics were well described by pseudo-second-order equation models. The experimental results showed that the Fe3O4/chitosan modified with ethylenediamine presented higher adsorption selectivity for Cu2+ than for Cd2+ and Ni2+ in all studied pH ranges.
2007, 23(12): 1985-1988
doi: 10.3866/PKU.WHXB20071229
Abstract:
Nanoscaled α-ZnS spheres about 35 nm in diameter were synthesized by a chemical solution way. XRD and TEM results showed that the nanoscaled ZnS spheres were made up of secondary nanoparticles with diameters about 6 nm. Two emission bands were observed in the photoluminescence (PL) spectrum of ZnS nanocrystals, one centered at 430 nm while the other at 360 nm. The former was attributed to the surface trapped emission, while the latter was assigned to the near band-edge emission. The Raman spectra characterization showed that no photodecomposition was observed under the strong laser irradiation, which indicated that the as-prepared ZnS nanocrystals were of high chemical stability.
Nanoscaled α-ZnS spheres about 35 nm in diameter were synthesized by a chemical solution way. XRD and TEM results showed that the nanoscaled ZnS spheres were made up of secondary nanoparticles with diameters about 6 nm. Two emission bands were observed in the photoluminescence (PL) spectrum of ZnS nanocrystals, one centered at 430 nm while the other at 360 nm. The former was attributed to the surface trapped emission, while the latter was assigned to the near band-edge emission. The Raman spectra characterization showed that no photodecomposition was observed under the strong laser irradiation, which indicated that the as-prepared ZnS nanocrystals were of high chemical stability.
2007, 23(12): 1989-2016
Abstract:
2007, 23(12): 2017-2028
Abstract:
