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2012 Volume 28 Issue 6
2012, 28(06):
Abstract:
2012, 28(06): 1275-1290
doi: 10.3866/PKU.WHXB201203162
Abstract:
ld nanorods exhibit unique and tunable surface plasmon resonance (SPR) derived optical properties in the ultraviolet-visible-near infrared (UV-Vis-NIR) region. The high stability, low biological toxicity, bright color, and versatility of ld nanorods have inspired an explosion of research interest in their properties and applications (which include roles in catalysis, data storage, and biomedicine). This paper presents a brief overview of current research progress on the optical properties of ld nanorods, including surface plasmon resonance, local field enhancement, plasmon coupling, fluorescence, and application outlook.
ld nanorods exhibit unique and tunable surface plasmon resonance (SPR) derived optical properties in the ultraviolet-visible-near infrared (UV-Vis-NIR) region. The high stability, low biological toxicity, bright color, and versatility of ld nanorods have inspired an explosion of research interest in their properties and applications (which include roles in catalysis, data storage, and biomedicine). This paper presents a brief overview of current research progress on the optical properties of ld nanorods, including surface plasmon resonance, local field enhancement, plasmon coupling, fluorescence, and application outlook.
2012, 28(06): 1291-1305
doi: 10.3866/PKU.WHXB201204093
Abstract:
Self-ordered porous anodic TiO2 nanotubes and other porous anodic oxides (PAO) have received considerable attention because of their potential for high technological application in a number of fields. The anodization of valve metals has been widely investigated over the last eight decades. The formation mechanisms of hexa nal cells and nanotubes, however, have remained unclear until now. Simply reviewing the mechanisms of PAO formation was not the aim of this research and we were more interested in reviewing the forming processes of compact anodic oxides (CAO) and investigating the relationship between the PAO and CAO, to better understand the pore generating mechanisms. The present work introduces the differences between PAO and CAO films, as well as reviewing the traditional theories of PAO films and their deficiencies. Recent progress in the formation mechanism of PAO, including the viscous flow, breakdown, equifield strength, and oxygen bubbles models has been reviewed in detail. The perspective on future developments for the PAO forming mechanism has been tentatively discussed. Based on sufficient analysis of the latest findings, it has been proposed that several approaches may be employed for investigating the pore forming and self-ordering mechanisms. These new approaches include ultrasound-assisted anodizing, anodizing under vacuum or high pressure and adding sodium carbonate or a reducing agent to the PAO-forming electrolytes. An investigation of changes in the current and anodizing efficiencies would also be an effective approach for better understanding the physical nature of fieldassisted dissolution (FAD).
Self-ordered porous anodic TiO2 nanotubes and other porous anodic oxides (PAO) have received considerable attention because of their potential for high technological application in a number of fields. The anodization of valve metals has been widely investigated over the last eight decades. The formation mechanisms of hexa nal cells and nanotubes, however, have remained unclear until now. Simply reviewing the mechanisms of PAO formation was not the aim of this research and we were more interested in reviewing the forming processes of compact anodic oxides (CAO) and investigating the relationship between the PAO and CAO, to better understand the pore generating mechanisms. The present work introduces the differences between PAO and CAO films, as well as reviewing the traditional theories of PAO films and their deficiencies. Recent progress in the formation mechanism of PAO, including the viscous flow, breakdown, equifield strength, and oxygen bubbles models has been reviewed in detail. The perspective on future developments for the PAO forming mechanism has been tentatively discussed. Based on sufficient analysis of the latest findings, it has been proposed that several approaches may be employed for investigating the pore forming and self-ordering mechanisms. These new approaches include ultrasound-assisted anodizing, anodizing under vacuum or high pressure and adding sodium carbonate or a reducing agent to the PAO-forming electrolytes. An investigation of changes in the current and anodizing efficiencies would also be an effective approach for better understanding the physical nature of fieldassisted dissolution (FAD).
2012, 28(06): 1306-1312
doi: 10.3866/PKU.WHXB201204012
Abstract:
A new eigenvalue analysis-based method is presented for the construction of skeletal reduced mechanisms from complex chemical reaction mechanisms. A reduced mechanism of 21 species and 83 elementary reactions for methane-air combustion was generated from detailed mechanism GRI1.2. The ignition delay time, obtained for different values of equivalence ratio, initial temperature and pressure on the basis of this reduced mechanism, were compared with those based on the detailed mechanism GRI1.2, and another skeletal mechanism DRM19. The reduced mechanism agreed favorably with the detailed model, and performed more accurately than DRM19. Two reduced mechanisms, the first involving 120 reactions among 26 species, the second, 140 reactions among 30 species, were also generated from GRI3.0. They were tested by means of premixed laminar flame calculations. The method very accurately predicted speed of flame propagation and key species concentration and even NO concentration distribution in methane combustion.
A new eigenvalue analysis-based method is presented for the construction of skeletal reduced mechanisms from complex chemical reaction mechanisms. A reduced mechanism of 21 species and 83 elementary reactions for methane-air combustion was generated from detailed mechanism GRI1.2. The ignition delay time, obtained for different values of equivalence ratio, initial temperature and pressure on the basis of this reduced mechanism, were compared with those based on the detailed mechanism GRI1.2, and another skeletal mechanism DRM19. The reduced mechanism agreed favorably with the detailed model, and performed more accurately than DRM19. Two reduced mechanisms, the first involving 120 reactions among 26 species, the second, 140 reactions among 30 species, were also generated from GRI3.0. They were tested by means of premixed laminar flame calculations. The method very accurately predicted speed of flame propagation and key species concentration and even NO concentration distribution in methane combustion.
2012, 28(06): 1313-1319
doi: 10.3866/PKU.WHXB201203292
Abstract:
The effects of positive/negative silver nanoparticles on the spectroscopic properties of methyl orange (MO) in solution at different pH values were studied by UV-visible (UV-Vis) absorption spectroscopy and fluorometry. New complexes were formed by the strong electrostatic interaction between positive silver nanoparticles (P-Ag) and the MO so that UV-Vis absorption spectra showed the performance of the complexes. However, the UV-Vis absorption spectra only showed superposition of component peaks after addition of negative silver nanoparticles (N-Ag) to MO solution because of the weak interaction between N-Ag and MO induced by electrostatic repulsion. S1→S0 was significantly enhanced in the MO solution containing P-Ag. The largest and smallest fluorescence enhancement ratios were observed at pH 2.1 and 4.8, respectively. The fluorescence intensity of S2→S0 decreased and was almost independent of pH. Similar trends were observed for the MO solution containing N-Ag, except that the intensity of S1→S0 was slightly enhanced in the presence of a small amount of N-Ag. The effects of silver nanoparticles with different electrical properties on the spectroscopic properties of MO depend on the interaction between MO and the silver nanoparticles as well as local field enhancement and non-radiative energy transfer.
The effects of positive/negative silver nanoparticles on the spectroscopic properties of methyl orange (MO) in solution at different pH values were studied by UV-visible (UV-Vis) absorption spectroscopy and fluorometry. New complexes were formed by the strong electrostatic interaction between positive silver nanoparticles (P-Ag) and the MO so that UV-Vis absorption spectra showed the performance of the complexes. However, the UV-Vis absorption spectra only showed superposition of component peaks after addition of negative silver nanoparticles (N-Ag) to MO solution because of the weak interaction between N-Ag and MO induced by electrostatic repulsion. S1→S0 was significantly enhanced in the MO solution containing P-Ag. The largest and smallest fluorescence enhancement ratios were observed at pH 2.1 and 4.8, respectively. The fluorescence intensity of S2→S0 decreased and was almost independent of pH. Similar trends were observed for the MO solution containing N-Ag, except that the intensity of S1→S0 was slightly enhanced in the presence of a small amount of N-Ag. The effects of silver nanoparticles with different electrical properties on the spectroscopic properties of MO depend on the interaction between MO and the silver nanoparticles as well as local field enhancement and non-radiative energy transfer.
2012, 28(06): 1320-1328
doi: 10.3866/PKU.WHXB201204064
Abstract:
The interaction between melamine and 1,12-diaminododecanediorotate (DDO), a bolaamphiphile bearing molecular recognition sites for amine functional groups, was transformed into visible color changes using polymerized 2,4-tricosadiynoic acid (TCDA) vesicles. TCDA was found to be more sensitive than other polydiacetylene vesicles with various alkane chain-lengths in reporting the molecular recognition event. Colorimetric changes occurred as a result of modifications in the conjugated backbone of TCDA triggered by changes in the chemical environment associated with the recognition process. To better understand this mechanism, the influence of melamine on the thermotropic behavior of polydiacetylene vesicles and the thermodynamics were investigated via differential scanning calorimetry (DSC). It was found that the phase transitions of both TCDA and DDO/TCDA vesicles were shifted to higher temperatures when melamine was present, and that the magnitude of this shift increased as the melamine levels were raised. Color changes associated with the molecular recognition process were only observed with the unaided eye when melamine was introduced at levels well in excess of those theoretically required. Using sucrose and urea as model kosmotropic and chaotropic compounds, respectively, the effect of such solutes on the phase transition of polydiacetylene vesicles and equilibrium energetics of the molecular recognition were examined. Results indicate that the excess melamine likely behaves as a chaotrope in the colloid. In combination with the multipoint hydrogen bond formation between melamine and DDO, these effects are responsible for the blue-red color transition of the DDO/TCDA vesicles. Identification of this chaotrope-assisted color visualization mechanism for PDA vesicles provides new insights into the Hofmeister series effect on the conformation change of conjugated polymers.
The interaction between melamine and 1,12-diaminododecanediorotate (DDO), a bolaamphiphile bearing molecular recognition sites for amine functional groups, was transformed into visible color changes using polymerized 2,4-tricosadiynoic acid (TCDA) vesicles. TCDA was found to be more sensitive than other polydiacetylene vesicles with various alkane chain-lengths in reporting the molecular recognition event. Colorimetric changes occurred as a result of modifications in the conjugated backbone of TCDA triggered by changes in the chemical environment associated with the recognition process. To better understand this mechanism, the influence of melamine on the thermotropic behavior of polydiacetylene vesicles and the thermodynamics were investigated via differential scanning calorimetry (DSC). It was found that the phase transitions of both TCDA and DDO/TCDA vesicles were shifted to higher temperatures when melamine was present, and that the magnitude of this shift increased as the melamine levels were raised. Color changes associated with the molecular recognition process were only observed with the unaided eye when melamine was introduced at levels well in excess of those theoretically required. Using sucrose and urea as model kosmotropic and chaotropic compounds, respectively, the effect of such solutes on the phase transition of polydiacetylene vesicles and equilibrium energetics of the molecular recognition were examined. Results indicate that the excess melamine likely behaves as a chaotrope in the colloid. In combination with the multipoint hydrogen bond formation between melamine and DDO, these effects are responsible for the blue-red color transition of the DDO/TCDA vesicles. Identification of this chaotrope-assisted color visualization mechanism for PDA vesicles provides new insights into the Hofmeister series effect on the conformation change of conjugated polymers.
2012, 28(06): 1329-1336
doi: 10.3866/PKU.WHXB201204193
Abstract:
3-(dicyanomethylene)-5,5-dimethyl-1-(3-[9-(2-ethyl-hexyl)-carbazol]-vinyl) cyclohexene (DCDHCC) is one of a series of organic dyes with od emission performance in photoelectric devices. The absorption and emission spectra of DCDHCC were computed using PBE0, BMK, and M06 hybrids in the frame of time-dependent density functional theory (TDDFT) in combination with polarizable continuum models (PCMs). Linear-response (LR) and state-specific (SS) PCM approaches were used as well as 6-31G(d) and 6-31+G(d,p) basis sets. The absorption and emission spectra were calculated in benzene, tetrahydrofuran, and acetone and compared with experimental observations. On the one hand, choice of hybrids was found to have a greater effect on the absorption spectra than the basis sets or the solvent model and BMK was established to be a suitable functional for the calculation of the absorption spectra of DCDHCC, on the other hand, the basis set used had a significant impact on the geometries of the excited states and thus the emission spectra, and the 6-31+G(d,p) basis set was necessary for the optimization of the excited states. It is envisaged that our calculations may be of assistance in the design of analo us emitters.
3-(dicyanomethylene)-5,5-dimethyl-1-(3-[9-(2-ethyl-hexyl)-carbazol]-vinyl) cyclohexene (DCDHCC) is one of a series of organic dyes with od emission performance in photoelectric devices. The absorption and emission spectra of DCDHCC were computed using PBE0, BMK, and M06 hybrids in the frame of time-dependent density functional theory (TDDFT) in combination with polarizable continuum models (PCMs). Linear-response (LR) and state-specific (SS) PCM approaches were used as well as 6-31G(d) and 6-31+G(d,p) basis sets. The absorption and emission spectra were calculated in benzene, tetrahydrofuran, and acetone and compared with experimental observations. On the one hand, choice of hybrids was found to have a greater effect on the absorption spectra than the basis sets or the solvent model and BMK was established to be a suitable functional for the calculation of the absorption spectra of DCDHCC, on the other hand, the basis set used had a significant impact on the geometries of the excited states and thus the emission spectra, and the 6-31+G(d,p) basis set was necessary for the optimization of the excited states. It is envisaged that our calculations may be of assistance in the design of analo us emitters.
2012, 28(06): 1337-1346
doi: 10.3866/PKU.WHXB201204092
Abstract:
The electronic and geometrical structures of the ground and excited states of six fluorescent emitters, namely 3-(dicyanomethylene)-5,5-dimethyl-1-(3-[9-(2-ethyl-hexyl)-carbazol]-vinyl) cyclohexene (DCDHCC), DCDHCC2, 3-(dicyanomethylene)-5,5-dimethyl-1(4-diphenylamino-styryl) cyclohexene (DCDPC), DCDPC2, 3-(dicyanomethylene)-5,5-dimethyl-1-(4-[9-carbazol]-styryl)cyclohexene (DCDCC), and 3-(dicyanomethylene)-5,5-dimethyl-1-(4-dimethylamino-styryl)cyclohexene (DCDDC) which were specifically designed for organic light-emitting diodes (OLEDs), were studied using density functional theory (DFT) and time-dependent DFT (TDDFT) in conjunction with polarizable continuum models (PCMs). Five hybrid functionals, PBE0, M06, BMK, M062X, and CAM-B3LYP, were used and compared. The experimental spectra of the molecules in acetone solvent were precisely reproduced with the BMK functional. The ionization potential and the electron affinity were calculated to access the properties of the molecules in charge injection. It was found that, when double π-bridges and acceptors were used, the emission of emitters red-shifted to the optimal emitting region. Two brand new molecules, DCDCC2 and DCDDC2, which are the double-branched counterparts of DCDCC and DCDDC, respectively, have been designed. The calculated properties of DCDCC2 and DCDDC2 in spectra and charge injection suggested that they would be as effective in their capacities as fluorescent emitters as the above six emitters.
The electronic and geometrical structures of the ground and excited states of six fluorescent emitters, namely 3-(dicyanomethylene)-5,5-dimethyl-1-(3-[9-(2-ethyl-hexyl)-carbazol]-vinyl) cyclohexene (DCDHCC), DCDHCC2, 3-(dicyanomethylene)-5,5-dimethyl-1(4-diphenylamino-styryl) cyclohexene (DCDPC), DCDPC2, 3-(dicyanomethylene)-5,5-dimethyl-1-(4-[9-carbazol]-styryl)cyclohexene (DCDCC), and 3-(dicyanomethylene)-5,5-dimethyl-1-(4-dimethylamino-styryl)cyclohexene (DCDDC) which were specifically designed for organic light-emitting diodes (OLEDs), were studied using density functional theory (DFT) and time-dependent DFT (TDDFT) in conjunction with polarizable continuum models (PCMs). Five hybrid functionals, PBE0, M06, BMK, M062X, and CAM-B3LYP, were used and compared. The experimental spectra of the molecules in acetone solvent were precisely reproduced with the BMK functional. The ionization potential and the electron affinity were calculated to access the properties of the molecules in charge injection. It was found that, when double π-bridges and acceptors were used, the emission of emitters red-shifted to the optimal emitting region. Two brand new molecules, DCDCC2 and DCDDC2, which are the double-branched counterparts of DCDCC and DCDDC, respectively, have been designed. The calculated properties of DCDCC2 and DCDDC2 in spectra and charge injection suggested that they would be as effective in their capacities as fluorescent emitters as the above six emitters.
2012, 28(06): 1347-1354
doi: 10.3866/PKU.WHXB201203301
Abstract:
The molecular dynamics (MD) method has been used to simulate the solidification process of pure liquid Fe induced by a series of Al2O3 nanoparticles of different radii at three temperatures (1750, 1730 and 1710 K). The structural evolution of Al2O3 nanoparticles and the effect of these particles on the solidification process of pure Fe have been analyzed. It was found that during the solidification process, the inner structure of the Al2O3 nanoparticles remained crystalline and structural deformation only occurred in surface atoms. The CTIM-2 method showed that the solidified Fe atoms were mainly faced-centered cubic (fcc) and hexa nal closed-packed (hcp) atoms. In addition, the temperature at which solidification took place was influenced by the size of the Al2O3 nanoparticles. The orientations of the resulting Fe crystals were influenced by the extent of the drift of the Al2O3 nanoparticles.
The molecular dynamics (MD) method has been used to simulate the solidification process of pure liquid Fe induced by a series of Al2O3 nanoparticles of different radii at three temperatures (1750, 1730 and 1710 K). The structural evolution of Al2O3 nanoparticles and the effect of these particles on the solidification process of pure Fe have been analyzed. It was found that during the solidification process, the inner structure of the Al2O3 nanoparticles remained crystalline and structural deformation only occurred in surface atoms. The CTIM-2 method showed that the solidified Fe atoms were mainly faced-centered cubic (fcc) and hexa nal closed-packed (hcp) atoms. In addition, the temperature at which solidification took place was influenced by the size of the Al2O3 nanoparticles. The orientations of the resulting Fe crystals were influenced by the extent of the drift of the Al2O3 nanoparticles.
2012, 28(06): 1355-1360
doi: 10.3866/PKU.WHXB201204063
Abstract:
The geometries, stabilities, and electronic properties of Au12M (M=Na, Mg, Al, Si, P, S, Cl) clusters were systematically investigated by using first-principles calculations based on density functional theory (DFT). For each cluster, the average binding energy, the embedding energy, the vertical ionization potential, the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), the natural charge population analysis, and the natural bond orbital analysis (NBO) were calculated. The lowest-energy structures of Au12M (M=Na, Mg, Al) clusters are cages with M encapsulated in the center, while structures of Au12M (M=Si, P, S, Cl) clusters are pyramidal with M at the apex. The Au12S cluster, having the full closed-shells, is the most stable. Furthermore, from the natural population analysis, it follows that charges transfer from Au to M in all the clusters. The NBO and HOMO analyses reveal that hybridization occurs between the Au s-d orbitals and the M p orbitals.
The geometries, stabilities, and electronic properties of Au12M (M=Na, Mg, Al, Si, P, S, Cl) clusters were systematically investigated by using first-principles calculations based on density functional theory (DFT). For each cluster, the average binding energy, the embedding energy, the vertical ionization potential, the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), the natural charge population analysis, and the natural bond orbital analysis (NBO) were calculated. The lowest-energy structures of Au12M (M=Na, Mg, Al) clusters are cages with M encapsulated in the center, while structures of Au12M (M=Si, P, S, Cl) clusters are pyramidal with M at the apex. The Au12S cluster, having the full closed-shells, is the most stable. Furthermore, from the natural population analysis, it follows that charges transfer from Au to M in all the clusters. The NBO and HOMO analyses reveal that hybridization occurs between the Au s-d orbitals and the M p orbitals.
2012, 28(06): 1361-1367
doi: 10.3866/PKU.WHXB201203261
Abstract:
Intermolecular complexes of MCH2X…ClF (M=Cu, Ag, Au; X = F, Cl, Br) and CH3X…ClF were investigated using by quantum chemistry method. Only one stable structure containing a halogen bond was obtained for the CH3X…ClF complexes. For the MCH2X…ClF complexes, as well as the halogen-bonded complex, another optimized structure containing both a halogen bond and M…Cl interaction was determined. The stability of the MCH2X…ClF complexes was greater than that of the CH3X…ClF complexes. Substitution with M improves the stability of the resulting complex with the order Ag>Cu>Au. The most negative molecular electrostatic potential of X in MCH2X and CH3X was calculated, and the decrease of this value is the main reason for the enhanced stability of these complexes. The characteristics of these complexes were also studied by natural bond orbital and atoms in molecules methods. The second-order perturbation energy and topological properties of the saddle points were calculated and the results were consistent with the interaction energy.
Intermolecular complexes of MCH2X…ClF (M=Cu, Ag, Au; X = F, Cl, Br) and CH3X…ClF were investigated using by quantum chemistry method. Only one stable structure containing a halogen bond was obtained for the CH3X…ClF complexes. For the MCH2X…ClF complexes, as well as the halogen-bonded complex, another optimized structure containing both a halogen bond and M…Cl interaction was determined. The stability of the MCH2X…ClF complexes was greater than that of the CH3X…ClF complexes. Substitution with M improves the stability of the resulting complex with the order Ag>Cu>Au. The most negative molecular electrostatic potential of X in MCH2X and CH3X was calculated, and the decrease of this value is the main reason for the enhanced stability of these complexes. The characteristics of these complexes were also studied by natural bond orbital and atoms in molecules methods. The second-order perturbation energy and topological properties of the saddle points were calculated and the results were consistent with the interaction energy.
2012, 28(06): 1368-1372
doi: 10.3866/PKU.WHXB201203161
Abstract:
A hierarchical configuration of TiO2 nanoarray film, comprising a nestlike TiO2 nanoarray layer integrated with a nanosheet network overlayer, was constructed. The hierarchical TiO2 film was obtained by the post-hydrothermal treatment with NaOH solution on hydrothermally synthesized TiO2-derived nanostructured arrays grown on fluorine-doped tin oxide substrate (FTO). The TiO2 films were characterized by field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy, and absorbance spectroscopy. FE-SEM shows that the hierarchical TiO2 film with a thickness of 1.5 μm is composed of a nanosheet overlayer (~0.2 μm height) and the nestlike nanoarray layer (~1.3 μm height). XRD patterns display that the TiO2 films have pure anatase phase structure. UV-Vis spectra reveal enhanced light scattering and dye adsorption ability of the hierarchical TiO2 film. For the dye-sensitized solar cell (DSSC) based on the nanosheet/nestlike nanoarray hierarchical TiO2 film, a short-circuit current (Jsc) of 7.79 mA·cm-2, open-circuit voltage (Voc) of 0.80 V, fill factor (FF) of 0.40, and photoelectric conversion efficiency (η) of 2.48% are achieved. Within the dye-sensitized solar cell, the photoelectric conversion efficiency of the hierarchical TiO2 film was nearly ten times higher than that of nanostructured array film.
A hierarchical configuration of TiO2 nanoarray film, comprising a nestlike TiO2 nanoarray layer integrated with a nanosheet network overlayer, was constructed. The hierarchical TiO2 film was obtained by the post-hydrothermal treatment with NaOH solution on hydrothermally synthesized TiO2-derived nanostructured arrays grown on fluorine-doped tin oxide substrate (FTO). The TiO2 films were characterized by field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy, and absorbance spectroscopy. FE-SEM shows that the hierarchical TiO2 film with a thickness of 1.5 μm is composed of a nanosheet overlayer (~0.2 μm height) and the nestlike nanoarray layer (~1.3 μm height). XRD patterns display that the TiO2 films have pure anatase phase structure. UV-Vis spectra reveal enhanced light scattering and dye adsorption ability of the hierarchical TiO2 film. For the dye-sensitized solar cell (DSSC) based on the nanosheet/nestlike nanoarray hierarchical TiO2 film, a short-circuit current (Jsc) of 7.79 mA·cm-2, open-circuit voltage (Voc) of 0.80 V, fill factor (FF) of 0.40, and photoelectric conversion efficiency (η) of 2.48% are achieved. Within the dye-sensitized solar cell, the photoelectric conversion efficiency of the hierarchical TiO2 film was nearly ten times higher than that of nanostructured array film.
2012, 28(06): 1373-1379
doi: 10.3866/PKU.WHXB201204061
Abstract:
Organic bulk heterojunction photovoltaic devices based on poly(3-hexylthiophene) (P3HT, donor) and [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM, acceptor) were fabricated using solvent annealing treatment. The nanoscale morphology and structure of the P3HT:PCBM blend films were characterized by UV-Vis absorption spectroscopy (UV-Vis), atomic force microscopy (AFM), and X-ray diffraction (XRD) analyses. In addition, the AFM images were processed using the entropyfilt method. The performances of the P3HT:PCBM devices with different mass ratios were measured, having a structure of indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/P3HT:PCBM/aluminium (Al). The results showed that the crystallinity of the P3HT polymer can be disturbed by the relative amount of PCBM molecules. The 1:1 (mass ratio) blend film possessed the greatest absorption width by UV-Vis absorption, as well as od phase separation and a high level of crystallinity, providing the best device performance (2.77%). This study indicates that the donor and acceptor mass ratios do have an influence on the nanoscale morphology and structure of the blend films, which can in turn affect the device performance.
Organic bulk heterojunction photovoltaic devices based on poly(3-hexylthiophene) (P3HT, donor) and [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM, acceptor) were fabricated using solvent annealing treatment. The nanoscale morphology and structure of the P3HT:PCBM blend films were characterized by UV-Vis absorption spectroscopy (UV-Vis), atomic force microscopy (AFM), and X-ray diffraction (XRD) analyses. In addition, the AFM images were processed using the entropyfilt method. The performances of the P3HT:PCBM devices with different mass ratios were measured, having a structure of indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/P3HT:PCBM/aluminium (Al). The results showed that the crystallinity of the P3HT polymer can be disturbed by the relative amount of PCBM molecules. The 1:1 (mass ratio) blend film possessed the greatest absorption width by UV-Vis absorption, as well as od phase separation and a high level of crystallinity, providing the best device performance (2.77%). This study indicates that the donor and acceptor mass ratios do have an influence on the nanoscale morphology and structure of the blend films, which can in turn affect the device performance.
2012, 28(06): 1380-1386
doi: 10.3866/PKU.WHXB201203304
Abstract:
A precursor powder of Ce0.8Nd0.2O1.9 (NDC) containing 0.05% (mass fraction) SiO2 as an impurity (NDCSi) was doped with 0-2.0% (molar fraction) M or FeO1.5 via the sol-gel method. After pressing at 10 MPa, the samples were sintered at 1300 ° C for 6 h. The structure of the pellets was characterized by X-ray diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscopy (FE-SEM). The electrical conductivity of the pellets was measured using AC impedance spectroscopy. All of the samples exhibited a cubic fluorite structure. Doping with M or Fe2O3 lowered the sintering temperature, and increased the density, grain boundaries and total conductivity of NDCSi. The relative density of the samples doped with Fe2O3 or M (>93%) was higher than those of NDC or NDCSi (about 86%), suggesting these dopants are effective at promoting densification. NDCSi + 0.5FeO1.5 and NDCSi + 2.0M samples exhibited the highest conductivities of 0.63 × 10-2 and 0.29 × 10-2 S · cm-1, respectively, which are 5.7 and 2.6 times larger than that of NDCSi (0.11×10-2 S·cm-1) at 550 °C. Doping with M or Fe2O3 had a larger effect on the grain boundary conductivity of SDCSi than the bulk conductivity. These results indicate that M and Fe2O3 are effective sintering aids as well as grain boundary scavengers with different mechanisms.
A precursor powder of Ce0.8Nd0.2O1.9 (NDC) containing 0.05% (mass fraction) SiO2 as an impurity (NDCSi) was doped with 0-2.0% (molar fraction) M or FeO1.5 via the sol-gel method. After pressing at 10 MPa, the samples were sintered at 1300 ° C for 6 h. The structure of the pellets was characterized by X-ray diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscopy (FE-SEM). The electrical conductivity of the pellets was measured using AC impedance spectroscopy. All of the samples exhibited a cubic fluorite structure. Doping with M or Fe2O3 lowered the sintering temperature, and increased the density, grain boundaries and total conductivity of NDCSi. The relative density of the samples doped with Fe2O3 or M (>93%) was higher than those of NDC or NDCSi (about 86%), suggesting these dopants are effective at promoting densification. NDCSi + 0.5FeO1.5 and NDCSi + 2.0M samples exhibited the highest conductivities of 0.63 × 10-2 and 0.29 × 10-2 S · cm-1, respectively, which are 5.7 and 2.6 times larger than that of NDCSi (0.11×10-2 S·cm-1) at 550 °C. Doping with M or Fe2O3 had a larger effect on the grain boundary conductivity of SDCSi than the bulk conductivity. These results indicate that M and Fe2O3 are effective sintering aids as well as grain boundary scavengers with different mechanisms.
2012, 28(06): 1387-1392
doi: 10.3866/PKU.WHXB201204013
Abstract:
To improve the electrochemical activity of electrodes in the vanadium redox battery, carbon paper electrode was treated with a hydrogen peroxide and sulfuric acid solution, according to the hydrothermal acid oxidation method, in a Teflon-lined stainless steel autoclave over different time periods at 180 °C. The water contact angle test showed that the contact angle of treated carbon paper samples changed from 120.0° to 100.8° by adjusting the treatment time from 6 to 18 h. Furthermore, a treatment time of 12 h resulted in the lowest contact angle observed, indicating that the wetting property of the carbon paper had been enhanced under these treatment conditions. Fourier transformation infrared spectroscopy results showed that oxygen-containing groups, such as the carbonyl and carboxyl groups, had been successfully introduced to the carbon papers. Scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and charge-discharge tests were carried to characterize the surface topography and electrochemical properties of the carbon papers. The treated samples showed high activity in the redox reactions of V(IV)/V(V). A single-cell employing carbon paper was treated for 12 h as an electrode and exhibited an excellent performance. The energy efficiency reached 80% at a current density of 30 mA·cm-2. The corresponding coulombic and voltage efficiencies were 96% and 84%, respectively.
To improve the electrochemical activity of electrodes in the vanadium redox battery, carbon paper electrode was treated with a hydrogen peroxide and sulfuric acid solution, according to the hydrothermal acid oxidation method, in a Teflon-lined stainless steel autoclave over different time periods at 180 °C. The water contact angle test showed that the contact angle of treated carbon paper samples changed from 120.0° to 100.8° by adjusting the treatment time from 6 to 18 h. Furthermore, a treatment time of 12 h resulted in the lowest contact angle observed, indicating that the wetting property of the carbon paper had been enhanced under these treatment conditions. Fourier transformation infrared spectroscopy results showed that oxygen-containing groups, such as the carbonyl and carboxyl groups, had been successfully introduced to the carbon papers. Scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and charge-discharge tests were carried to characterize the surface topography and electrochemical properties of the carbon papers. The treated samples showed high activity in the redox reactions of V(IV)/V(V). A single-cell employing carbon paper was treated for 12 h as an electrode and exhibited an excellent performance. The energy efficiency reached 80% at a current density of 30 mA·cm-2. The corresponding coulombic and voltage efficiencies were 96% and 84%, respectively.
2012, 28(06): 1393-1397
doi: 10.3866/PKU.WHXB201204062
Abstract:
Well-aligned ZnO nanorods (NRs) were grown on the ZnO seed layer of a polyimide (PI) coated flexible substrate using the hydrothermal method and used as a support matrix for the immobilization of glucose oxidase ( x). The crystal structures and surface morphologies of the so-formed ZnO nanorods were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). x was immobilized on the surfaces of ZnO nanorods using electrostatic adsorption. Both the x and modified ZnO nanorods were characterized by UV-visible spectroscopy, and the absorption peaks of ZnO and x can be detected. Fourier transform infrared (FTIR) spectroscopy were used to characterize the chemical structure of the glucose oxide, which still maintained its biological activity. This study provides an experiment basis for the preparation of flexible glucose biosensors owing to the flexibility of the enzyme electrode, which showed a sensitive current response when tested by cyclic voltammetry.
Well-aligned ZnO nanorods (NRs) were grown on the ZnO seed layer of a polyimide (PI) coated flexible substrate using the hydrothermal method and used as a support matrix for the immobilization of glucose oxidase ( x). The crystal structures and surface morphologies of the so-formed ZnO nanorods were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). x was immobilized on the surfaces of ZnO nanorods using electrostatic adsorption. Both the x and modified ZnO nanorods were characterized by UV-visible spectroscopy, and the absorption peaks of ZnO and x can be detected. Fourier transform infrared (FTIR) spectroscopy were used to characterize the chemical structure of the glucose oxide, which still maintained its biological activity. This study provides an experiment basis for the preparation of flexible glucose biosensors owing to the flexibility of the enzyme electrode, which showed a sensitive current response when tested by cyclic voltammetry.
2012, 28(06): 1398-1404
doi: 10.3866/PKU.WHXB201204091
Abstract:
This work describes the electrochemical synthesis of cadmium sulfide (CdS) nanostructured films by applying a pulsed current technique on the ld electrode modified with a self-assembled p-aminothiophenol monolayer (PATP/Au). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the morphology and crystal phase of the synthesized samples. An ordered array of CdS nanorods with a relatively higher c-axis preferred orientation was found on the PATP/ Au substrate. The results indicated that the size of the CdS nanorods increased with the increase in the pulse width of the pulsed current, whereas the uniformity decreased. Furthermore, the size and coverage of the CdS nanorods increased with the increase in the pulse height. Thus, the morphology and size of the prepared CdS nanorods could be controlled by adjusting the pulse width and height. Cyclic voltammetry (CV) and chronopotentiometry were also applied to investigate the mechanism of the electrodeposition of CdS on PATP/Au. In accordance with the experimental results, we suggest that the interaction of the －NH2 in PATP molecules with Cd2+ in the solution may have contributed to the passing of electrons along the PATP chain following a modification of the p-aminothiophenol monolayer on the Au substrate. A formation mechanism for the electrochemically synthesized CdS nanorods on the PATP/Au substrate has consequently been proposed.
This work describes the electrochemical synthesis of cadmium sulfide (CdS) nanostructured films by applying a pulsed current technique on the ld electrode modified with a self-assembled p-aminothiophenol monolayer (PATP/Au). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the morphology and crystal phase of the synthesized samples. An ordered array of CdS nanorods with a relatively higher c-axis preferred orientation was found on the PATP/ Au substrate. The results indicated that the size of the CdS nanorods increased with the increase in the pulse width of the pulsed current, whereas the uniformity decreased. Furthermore, the size and coverage of the CdS nanorods increased with the increase in the pulse height. Thus, the morphology and size of the prepared CdS nanorods could be controlled by adjusting the pulse width and height. Cyclic voltammetry (CV) and chronopotentiometry were also applied to investigate the mechanism of the electrodeposition of CdS on PATP/Au. In accordance with the experimental results, we suggest that the interaction of the －NH2 in PATP molecules with Cd2+ in the solution may have contributed to the passing of electrons along the PATP chain following a modification of the p-aminothiophenol monolayer on the Au substrate. A formation mechanism for the electrochemically synthesized CdS nanorods on the PATP/Au substrate has consequently been proposed.
2012, 28(06): 1405-1410
doi: 10.3866/PKU.WHXB201203202
Abstract:
The self-assembly of hydrophobically associating polyacrylamide (HAPAM) and the effect of adding gemini surfactant (dimyristic acid glycol ester di(α-sodium sulfonate), DMES-14) were studied by static light scattering, dynamic light scattering, and fluorometry. HAPAM formed hydrophobic microdomains in solution through self-assembly, which decreased the fluorescence intensity ratio (I1/I3) of the first peak (373 nm) and the third peak (383 nm) in the emission spectrum of pyrene as the polymer HAPAM concentration (CP) was increased until a plateau was reached at high CP. When surfactant was added to the polymer solution, the interaction between HAPAM and surfactant resulted in the formation of mixed micelles. This caused I1/I3 to decrease as the surfactant concentration (CS) was increased at the same polymer concentration until CS was greater than 30 mg·L-1, after which point I1/I3 showed little change. The aggregation number of aggregates in the mixed system containing surfactant and polymer decreased at first and then increased as CP was increased. A certain amount of surfactant could enhance interchain interactions, while excess surfactant broke down interchain interactions between the hydrophobic groups of HAPAM, which resulted in maximum values of the apparent weight average molecular weight (Mw,a), root-mean-square radius of gyration (<Rg>), and hydrodynamic radius (<Rh>) of HAPAM as CS was increased. <Rg>/<Rh> increased slowly as CS was increased, which reflected the relative stretch of the polymer chains.
The self-assembly of hydrophobically associating polyacrylamide (HAPAM) and the effect of adding gemini surfactant (dimyristic acid glycol ester di(α-sodium sulfonate), DMES-14) were studied by static light scattering, dynamic light scattering, and fluorometry. HAPAM formed hydrophobic microdomains in solution through self-assembly, which decreased the fluorescence intensity ratio (I1/I3) of the first peak (373 nm) and the third peak (383 nm) in the emission spectrum of pyrene as the polymer HAPAM concentration (CP) was increased until a plateau was reached at high CP. When surfactant was added to the polymer solution, the interaction between HAPAM and surfactant resulted in the formation of mixed micelles. This caused I1/I3 to decrease as the surfactant concentration (CS) was increased at the same polymer concentration until CS was greater than 30 mg·L-1, after which point I1/I3 showed little change. The aggregation number of aggregates in the mixed system containing surfactant and polymer decreased at first and then increased as CP was increased. A certain amount of surfactant could enhance interchain interactions, while excess surfactant broke down interchain interactions between the hydrophobic groups of HAPAM, which resulted in maximum values of the apparent weight average molecular weight (Mw,a), root-mean-square radius of gyration (<Rg>), and hydrodynamic radius (<Rh>) of HAPAM as CS was increased. <Rg>/<Rh> increased slowly as CS was increased, which reflected the relative stretch of the polymer chains.
2012, 28(06): 1411-1417
doi: 10.3866/PKU.WHXB201203262
Abstract:
The aggregation behavior of the triblock copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (L64, PEO13PPO30PEO13) in the room-temperature ionic liquid 1-butyl-3- methylimidazolium tetrafluoroborate ([Bmim] [BF4]) was investigated using polarized optical microscopy (POM), small-angle X-ray scattering (SAXS), and Fourier transform infrared (FTIR) spectroscopy. The phase diagram of the L64/[Bmim] [BF4] system is described, where the micellar phase (L1), a mixture of lamellar liquid crystalline (Lα) and L1 phases, the Lα phase, a mixture of Lα and reverse micellar (L2) phases, and the L2 phase are sequentially mapped. Among these phases, the behavior of the Lα phase formed in the L64/[Bmim][BF4] system in the L64 concentration region of 40%-65% (w, mass fraction) was focused on because it forms highly-ordered structures. The Maltese cross texture was found through POM characterization, and was typical for the Lα phase. The SAXS patterns further confirm the formation of the Lα phase. In addition, the lattice spacings of the Lα phase were obtained from the SAXS patterns. The effect of temperature on the microstructure of the Lα phase was also elucidated. As the temperature was increased, the lattice spacing and ordering of the Lα phase increased, while the interfacial area decreased for a certain temperature range. However, the birefringence of the Lα phase disappeared when the temperature reached a certain level, which was attributed to the breakdown of hydrogen bonding between [Bmim] [BF4] and poly(ethylene oxide) chains, so the ordering of the Lα phase was decreased. The formation mechanism of the Lα phase is also discussed. Hydrogen bonding, electrostatic and solvophobic interactions are believed to be the main driving forces for the formation of Lα phase in the L64/[Bmim][BF4] system.
The aggregation behavior of the triblock copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (L64, PEO13PPO30PEO13) in the room-temperature ionic liquid 1-butyl-3- methylimidazolium tetrafluoroborate ([Bmim] [BF4]) was investigated using polarized optical microscopy (POM), small-angle X-ray scattering (SAXS), and Fourier transform infrared (FTIR) spectroscopy. The phase diagram of the L64/[Bmim] [BF4] system is described, where the micellar phase (L1), a mixture of lamellar liquid crystalline (Lα) and L1 phases, the Lα phase, a mixture of Lα and reverse micellar (L2) phases, and the L2 phase are sequentially mapped. Among these phases, the behavior of the Lα phase formed in the L64/[Bmim][BF4] system in the L64 concentration region of 40%-65% (w, mass fraction) was focused on because it forms highly-ordered structures. The Maltese cross texture was found through POM characterization, and was typical for the Lα phase. The SAXS patterns further confirm the formation of the Lα phase. In addition, the lattice spacings of the Lα phase were obtained from the SAXS patterns. The effect of temperature on the microstructure of the Lα phase was also elucidated. As the temperature was increased, the lattice spacing and ordering of the Lα phase increased, while the interfacial area decreased for a certain temperature range. However, the birefringence of the Lα phase disappeared when the temperature reached a certain level, which was attributed to the breakdown of hydrogen bonding between [Bmim] [BF4] and poly(ethylene oxide) chains, so the ordering of the Lα phase was decreased. The formation mechanism of the Lα phase is also discussed. Hydrogen bonding, electrostatic and solvophobic interactions are believed to be the main driving forces for the formation of Lα phase in the L64/[Bmim][BF4] system.
2012, 28(06): 1418-1424
doi: 10.3866/PKU.WHXB201203291
Abstract:
A novel aromatic Schiff base ligand has been designed and its interfacial phase behavior as well as its in situ coordination with Cu(II) ions on the surface of pure water was compared with those of the corresponding pre-synthesized Cu(II) complex. Surface pressure-area isotherms, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, and atomic force microscopy were used to characterize deposited monolayer and multilayer films of the complexes. Both the ligand and corresponding complex formed stable monolayer or multilayer films at the air/water interface, which could be subsequently transferred onto solid substrates to construct Langmuir-Blodgett films. A novel phase transition was observed when the ligand was spread on the surface of pure water. During this phase transition, the two-dimensional (2D) flat film changed into three-dimensional (3D) fiber-like nanoarchitectures. However, upon coordination with Cu(II) ions, only flat films were obtained. This phenomenon was thought to be caused by the change of molecular conformation and/or hydrophobicity during supramolecular assembly at the air/water interface. This work provides a simple clue for regulating the nanostructures in organized films.
A novel aromatic Schiff base ligand has been designed and its interfacial phase behavior as well as its in situ coordination with Cu(II) ions on the surface of pure water was compared with those of the corresponding pre-synthesized Cu(II) complex. Surface pressure-area isotherms, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, and atomic force microscopy were used to characterize deposited monolayer and multilayer films of the complexes. Both the ligand and corresponding complex formed stable monolayer or multilayer films at the air/water interface, which could be subsequently transferred onto solid substrates to construct Langmuir-Blodgett films. A novel phase transition was observed when the ligand was spread on the surface of pure water. During this phase transition, the two-dimensional (2D) flat film changed into three-dimensional (3D) fiber-like nanoarchitectures. However, upon coordination with Cu(II) ions, only flat films were obtained. This phenomenon was thought to be caused by the change of molecular conformation and/or hydrophobicity during supramolecular assembly at the air/water interface. This work provides a simple clue for regulating the nanostructures in organized films.
2012, 28(06): 1425-1431
doi: 10.3866/PKU.WHXB201203091
Abstract:
The surface acid-base properties of a γ-Al2O3/SiO2 nano-mixed system were studied by potentiometric titration technique. Based on experimental data complemented by surface complexation theory of Constant Capacitance Model, the relevant equilibrium constants of surface acid-base reactions in the nano-mixed system were calculated using the WinSGW program as: ≡XOH+H+⇔≡XOH2+ (lgK1=5.06± 0.05); ≡XOH⇔≡XO-+H+ (lgK2=-8.45±0.10). Furthermore, the adsorption of heavy metal ions (Cu2+ , Pb2+ , Zn2+ ) at the surface of the γ-Al2O3/SiO2 nano-mixed system was studied as a function of pH. Again using WinSGW software, the surface complexation constants of Cu2+, Pb2+ and Zn2+ ions in aqueous suspensions of γ-Al2O3/SiO2mixed systems were established respectively as: ≡XOH+M2+⇔≡XOM++H+ [lgK=-2.20, -1.72, -2.90 (M=Cu, Pb, Zn)]
The surface acid-base properties of a γ-Al2O3/SiO2 nano-mixed system were studied by potentiometric titration technique. Based on experimental data complemented by surface complexation theory of Constant Capacitance Model, the relevant equilibrium constants of surface acid-base reactions in the nano-mixed system were calculated using the WinSGW program as: ≡XOH+H+⇔≡XOH2+ (lgK1=5.06± 0.05); ≡XOH⇔≡XO-+H+ (lgK2=-8.45±0.10). Furthermore, the adsorption of heavy metal ions (Cu2+ , Pb2+ , Zn2+ ) at the surface of the γ-Al2O3/SiO2 nano-mixed system was studied as a function of pH. Again using WinSGW software, the surface complexation constants of Cu2+, Pb2+ and Zn2+ ions in aqueous suspensions of γ-Al2O3/SiO2mixed systems were established respectively as: ≡XOH+M2+⇔≡XOM++H+ [lgK=-2.20, -1.72, -2.90 (M=Cu, Pb, Zn)]
2012, 28(06): 1432-1438
doi: 10.3866/PKU.WHXB201203151
Abstract:
A hydrophobic porous silica material was successfully synthesized using sodium silicate as silica source, hydrochloric acid as catalyst, and trimethylchlorosilane (TMCS) as a surface modifying agent, through sol-gel and surface modification processes. The structure and properties of the fabricated porous silica were analyzed by Fourier-transform infrared (FTIR) spectroscopy, contact-angle analyzer, liquid N2 adsorption, and scanning electron microscopy (SEM). The porous silica displayed a hierarchical porous structure and was super-hydrophobic, with contact angle as high as 156°. Specific surface area and pore volume were determined to be 566 m2·g-1 and 2.28 cm3·g-1, respectively. Moreover, the porous silica could adsorb up to 14 times its own mass of toluene, gasoline, diesel, and lube oil. The abundant mesopores and macropores allowed adsorption saturation to be reached within several minutes. In addition, the porous silica was extremely hydrophobic in gasoline-water mixture and thus preferentially adsorbed organic compounds other than water. This is an important requisite of od recyclability. It was verified that, following extraction with n-hexane, the regenerated porous silica retained its initial adsorption capacity. This porous silica, with od selectivity and excellent regeneration capability for oil removal, could find novel applications in the adsorption and separation of organics from polluted water.
A hydrophobic porous silica material was successfully synthesized using sodium silicate as silica source, hydrochloric acid as catalyst, and trimethylchlorosilane (TMCS) as a surface modifying agent, through sol-gel and surface modification processes. The structure and properties of the fabricated porous silica were analyzed by Fourier-transform infrared (FTIR) spectroscopy, contact-angle analyzer, liquid N2 adsorption, and scanning electron microscopy (SEM). The porous silica displayed a hierarchical porous structure and was super-hydrophobic, with contact angle as high as 156°. Specific surface area and pore volume were determined to be 566 m2·g-1 and 2.28 cm3·g-1, respectively. Moreover, the porous silica could adsorb up to 14 times its own mass of toluene, gasoline, diesel, and lube oil. The abundant mesopores and macropores allowed adsorption saturation to be reached within several minutes. In addition, the porous silica was extremely hydrophobic in gasoline-water mixture and thus preferentially adsorbed organic compounds other than water. This is an important requisite of od recyclability. It was verified that, following extraction with n-hexane, the regenerated porous silica retained its initial adsorption capacity. This porous silica, with od selectivity and excellent regeneration capability for oil removal, could find novel applications in the adsorption and separation of organics from polluted water.
2012, 28(06): 1439-1447
doi: 10.3866/PKU.WHXB201203142
Abstract:
Synthesis of micro-mesoporous zeolites β/M (where β and M denote β zeolite and MCM-41 zeolite, respectively) combined with zeolites β and MCM-41 was achieved in the sodium hydroxide system using a two-step hydrothermal treatment method. Sodium aluminate and fume silica were used as the sources of aluminum and silicon, while tetraethylammonium hydroxide (TEAOH) and cetyltrimethylammonium bromide (CTAB) were used as templates for the formation of β crystal seeds and for self-assembling of β crystal seeds into mesoporous zeolites β/M, respectively. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and high resolution transmission electron microscope (HRTEM). Reaction time and particle size of β crystal seeds were found to play an important role in the synthesis of β/M zeolites. When β seeds crystallize in a short time, a pure phase (denoted βM) can result, whose mesoporous structure resembles MCM-41, while long crystallization times can result in a phase mixture of mesoporous βM and microporous β zeolite. Due to the insertion of the secondary building units of β zeolite into the mesoporous wall, the β/M micro-mesoporous combined zeolites showed enhanced toluene adsorption performance and hydrothermal stability.
Synthesis of micro-mesoporous zeolites β/M (where β and M denote β zeolite and MCM-41 zeolite, respectively) combined with zeolites β and MCM-41 was achieved in the sodium hydroxide system using a two-step hydrothermal treatment method. Sodium aluminate and fume silica were used as the sources of aluminum and silicon, while tetraethylammonium hydroxide (TEAOH) and cetyltrimethylammonium bromide (CTAB) were used as templates for the formation of β crystal seeds and for self-assembling of β crystal seeds into mesoporous zeolites β/M, respectively. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and high resolution transmission electron microscope (HRTEM). Reaction time and particle size of β crystal seeds were found to play an important role in the synthesis of β/M zeolites. When β seeds crystallize in a short time, a pure phase (denoted βM) can result, whose mesoporous structure resembles MCM-41, while long crystallization times can result in a phase mixture of mesoporous βM and microporous β zeolite. Due to the insertion of the secondary building units of β zeolite into the mesoporous wall, the β/M micro-mesoporous combined zeolites showed enhanced toluene adsorption performance and hydrothermal stability.
2012, 28(06): 1448-1454
doi: 10.3866/PKU.WHXB201204011
Abstract:
MOx-SiO2 (M=Ce, Zr, Al) mixed oxides with a MOx:SiO2 mass ratio of 1:1 were prepared by co-precipitation. Pt-only diesel oxidation catalysts supported on these mixed oxides were obtained by the incipient wetness method. The catalytic activities in simplified diesel exhaust gas before and after SO2 treatment were analyzed. The catalysts were characterized by X-ray diffraction, N2 adsorption-desorption, NH3/O2/CO2 temperature programmed desorption (NH3/O2/CO2-TPD) and X-ray photoelectron spectroscopy (XPS). The results of NH3-TPD suggested that the surface of the catalysts had multiple acidic sites, and the number of medium-strength acidic sites increased following treatment with SO2. The results of O2-TPD revealed that there were α and β oxygen species in the catalysts, and the amount of O2 desorption decreased for the SO2-treated catalysts. The Pt/Al2O3-SiO2 catalyst exhibited the lowest surface acidity and the largest amount of oxygen desorption. XPS indicated that the binding energy of Pt 4f5/2 decreased when the catalysts were treated with SO2. All the catalysts showed excellent activity for CO and C3H8, and the Pt/ ZrO2-SiO2 catalyst exhibited the best SO2 poisoning resistance, showing the potential for these catalysts to be applied in diesel oxidation.
MOx-SiO2 (M=Ce, Zr, Al) mixed oxides with a MOx:SiO2 mass ratio of 1:1 were prepared by co-precipitation. Pt-only diesel oxidation catalysts supported on these mixed oxides were obtained by the incipient wetness method. The catalytic activities in simplified diesel exhaust gas before and after SO2 treatment were analyzed. The catalysts were characterized by X-ray diffraction, N2 adsorption-desorption, NH3/O2/CO2 temperature programmed desorption (NH3/O2/CO2-TPD) and X-ray photoelectron spectroscopy (XPS). The results of NH3-TPD suggested that the surface of the catalysts had multiple acidic sites, and the number of medium-strength acidic sites increased following treatment with SO2. The results of O2-TPD revealed that there were α and β oxygen species in the catalysts, and the amount of O2 desorption decreased for the SO2-treated catalysts. The Pt/Al2O3-SiO2 catalyst exhibited the lowest surface acidity and the largest amount of oxygen desorption. XPS indicated that the binding energy of Pt 4f5/2 decreased when the catalysts were treated with SO2. All the catalysts showed excellent activity for CO and C3H8, and the Pt/ ZrO2-SiO2 catalyst exhibited the best SO2 poisoning resistance, showing the potential for these catalysts to be applied in diesel oxidation.
2012, 28(06): 1455-1460
doi: 10.3866/PKU.WHXB201203303
Abstract:
Au catalysts supported on Al2O3 and MOx-Al2O3 (M=Fe and Zn) were prepared by the deposition-precipitation method. Their catalytic activities for CO oxidation in the absence and presence of an H2-rich steam at room temperature were investigated in detail. Catalyst bed temperatures were determined directly by a thermocouple. The catalyst surface temperature depended on the volume ratio of O2/CO, and the concentrations of CO and H2. The temperature on the Au/Al2O3 surface can reach 170°C during CO oxidation, and is decreased to 55°C by addition of FeOx. These results indicate that formation of hot-spots on γ-alumina-supported ld catalysts could be controlled by adding an appropriate dopant. The structure of the catalysts was characterized by techniques such as X-ray powder diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Addition of a dopant could transfer the active center from Au to AuIII, which resulted in different reaction mechanisms of preferential oxidation of CO in the presence of H2.
Au catalysts supported on Al2O3 and MOx-Al2O3 (M=Fe and Zn) were prepared by the deposition-precipitation method. Their catalytic activities for CO oxidation in the absence and presence of an H2-rich steam at room temperature were investigated in detail. Catalyst bed temperatures were determined directly by a thermocouple. The catalyst surface temperature depended on the volume ratio of O2/CO, and the concentrations of CO and H2. The temperature on the Au/Al2O3 surface can reach 170°C during CO oxidation, and is decreased to 55°C by addition of FeOx. These results indicate that formation of hot-spots on γ-alumina-supported ld catalysts could be controlled by adding an appropriate dopant. The structure of the catalysts was characterized by techniques such as X-ray powder diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Addition of a dopant could transfer the active center from Au to AuIII, which resulted in different reaction mechanisms of preferential oxidation of CO in the presence of H2.
2012, 28(06): 1461-1466
doi: 10.3866/PKU.WHXB201203302
Abstract:
CaO modified CuZnAlZr mixed oxide catalysts were prepared by mechanical mixing and co-precipitation methods, and their catalytic performances for CO hydrogenation to higher alcohols were investigated using a continuous flow high-pressure fixed-bed micro-reactor. The catalysts were characterized by X-ray diffraction (XRD), N2-adsorption-desorpotion, temperature-programmed reduction of H2 (H2-TPR), and temperature-programmed desorption of CO2 (CO2-TPD). The results showed that doping with CaO did not alter the textural properties of the catalyst, but increased the number of basic sites. Furthermore, the CaO-modified CuZnAlZr catalysts possessed both weak and medium strength basic sites, while unmodified CuZnAlZr catalyst possessed only weak basic sites. Catalytic performance, assessed by CO hydrogenation to C2+ alcohols, was improved in the CaO-doped CuZnAlZr catalyst relative to the undoped catalyst.
CaO modified CuZnAlZr mixed oxide catalysts were prepared by mechanical mixing and co-precipitation methods, and their catalytic performances for CO hydrogenation to higher alcohols were investigated using a continuous flow high-pressure fixed-bed micro-reactor. The catalysts were characterized by X-ray diffraction (XRD), N2-adsorption-desorpotion, temperature-programmed reduction of H2 (H2-TPR), and temperature-programmed desorption of CO2 (CO2-TPD). The results showed that doping with CaO did not alter the textural properties of the catalyst, but increased the number of basic sites. Furthermore, the CaO-modified CuZnAlZr catalysts possessed both weak and medium strength basic sites, while unmodified CuZnAlZr catalyst possessed only weak basic sites. Catalytic performance, assessed by CO hydrogenation to C2+ alcohols, was improved in the CaO-doped CuZnAlZr catalyst relative to the undoped catalyst.
2012, 28(06): 1467-1473
doi: 10.3866/PKU.WHXB201203312
Abstract:
Solid-state grinding is a simple and effective technique to incorporate active species into the channels of mesoporous materials with different degrees of filling. Using this method, different concentrations of CuO were loaded into the mesochannels of as-prepared mesoporous silica (APS) and calcined SBA-15 (CS). The samples were prepared and characterized using X-ray diffraction (XRD), N2 physisorption, and Fourier transform infrared (FTIR) spectroscopy. The relative number of hydroxyl groups was studied by in situ FTIR spectroscopy, and the total surface acidity of the adsorbents was monitored by FTIR spectroscopy at 423 K using pyridine as a probe. Desulfurization of fluid catalytic cracking (FCC) fuel oils using these materials was investigated. The results suggest that CuO interacts directly with support hydroxyl groups to form [Si-O-Cu-O-Si] linkages in the mixtures, which can effectively constrain the condensation of hydroxyl groups in SBA-15 to improve the mesostructure of the adsorbents during calcination. Saturated coverage of the surface of APS is reached using 3 mmol·g-1 CuO. However, using CS, aggregation of CuO is observed in the material containing 3 mmol·g-1 of CuO. Both the surface acidity and desulfurization performance significantly increase upon modification of SBA-15 with CuO, and then decrease slowly as the concentration of CuO is increased. The sample containing 3 mmol·g-1 CuO shows the highest Lewis acidity and desulfurization performance. The Lewis acidity of the adsorbents matches the adsorptive desulfurization performance. It is also demonstrated that reduction of charge density around copper atoms helps to form Lewis acid sites.
Solid-state grinding is a simple and effective technique to incorporate active species into the channels of mesoporous materials with different degrees of filling. Using this method, different concentrations of CuO were loaded into the mesochannels of as-prepared mesoporous silica (APS) and calcined SBA-15 (CS). The samples were prepared and characterized using X-ray diffraction (XRD), N2 physisorption, and Fourier transform infrared (FTIR) spectroscopy. The relative number of hydroxyl groups was studied by in situ FTIR spectroscopy, and the total surface acidity of the adsorbents was monitored by FTIR spectroscopy at 423 K using pyridine as a probe. Desulfurization of fluid catalytic cracking (FCC) fuel oils using these materials was investigated. The results suggest that CuO interacts directly with support hydroxyl groups to form [Si-O-Cu-O-Si] linkages in the mixtures, which can effectively constrain the condensation of hydroxyl groups in SBA-15 to improve the mesostructure of the adsorbents during calcination. Saturated coverage of the surface of APS is reached using 3 mmol·g-1 CuO. However, using CS, aggregation of CuO is observed in the material containing 3 mmol·g-1 of CuO. Both the surface acidity and desulfurization performance significantly increase upon modification of SBA-15 with CuO, and then decrease slowly as the concentration of CuO is increased. The sample containing 3 mmol·g-1 CuO shows the highest Lewis acidity and desulfurization performance. The Lewis acidity of the adsorbents matches the adsorptive desulfurization performance. It is also demonstrated that reduction of charge density around copper atoms helps to form Lewis acid sites.
2012, 28(06): 1474-1480
doi: 10.3866/PKU.WHXB201203311
Abstract:
In this paper, a series of La0.7Sr0.3Co1-xFexO3 (x=0, 0.2, 0.6, and 1.0) catalysts was synthesized by a sol-gel method with calcination at 700 °C in static air. The effect of the Fe doping on the structure, the performance of the NOx storage, sulfur tolerance and regeneration of the perovskite catalysts was investigated. Our results showed that the partial substitution of Co with Fe improved the depersion of the SrCO3 phase, and that the perovskite phase became the only species detected from the X-ray diffraction (XRD) patterns. The NOx storage capacity (NSC) of the catalysts dropped following an increase in the proportion of Fe doping. The deposition of sulfate on the surface and the partial structural damage of the La0.7Sr0.3CoO3 catalyst led to a dramatic reduction in the NSC and the NO oxidation capacity after the sulfation treatment: the NSC being reduced by 64.2%, and the conversion of NO-to-NO2 falling to 43.4% from 72.8%. The sulfur tolerance of the perovskite catalyst, however, was improved after doping with Fe at the B sites of the La0.7Sr0.3CoO3 catalyst. Of all of these catalysts, the perovskite with 60% of Fe doping (the Fe60 sample) gave the best performance for sulfur tolerane properties and regeneration ability. The NSC of the Fe60 sample was reduced by only 16.6%, and the NO-to-NO2 conversion reached the value almost similar to that of the fresh sample (i.e. 69.1%).
In this paper, a series of La0.7Sr0.3Co1-xFexO3 (x=0, 0.2, 0.6, and 1.0) catalysts was synthesized by a sol-gel method with calcination at 700 °C in static air. The effect of the Fe doping on the structure, the performance of the NOx storage, sulfur tolerance and regeneration of the perovskite catalysts was investigated. Our results showed that the partial substitution of Co with Fe improved the depersion of the SrCO3 phase, and that the perovskite phase became the only species detected from the X-ray diffraction (XRD) patterns. The NOx storage capacity (NSC) of the catalysts dropped following an increase in the proportion of Fe doping. The deposition of sulfate on the surface and the partial structural damage of the La0.7Sr0.3CoO3 catalyst led to a dramatic reduction in the NSC and the NO oxidation capacity after the sulfation treatment: the NSC being reduced by 64.2%, and the conversion of NO-to-NO2 falling to 43.4% from 72.8%. The sulfur tolerance of the perovskite catalyst, however, was improved after doping with Fe at the B sites of the La0.7Sr0.3CoO3 catalyst. Of all of these catalysts, the perovskite with 60% of Fe doping (the Fe60 sample) gave the best performance for sulfur tolerane properties and regeneration ability. The NSC of the Fe60 sample was reduced by only 16.6%, and the NO-to-NO2 conversion reached the value almost similar to that of the fresh sample (i.e. 69.1%).
2012, 28(06): 1481-1488
doi: 10.3866/PKU.WHXB201203313
Abstract:
Neodymium-doped bismuth titanate (Bi3.25Nd0.75Ti3O12, BNdT) nanostructures with different morphologies were synthesized hydrothermally without using surfactant or template. Transmission electron microscopy (TEM) results showed that different morphologies could be fabricated simply by manipulating the concentration of OH- ions during hydrothermal synthesis. Hydroxide ions played an important role in controlling the formation of seeds and the growth rate of BNdT particles. On the basis of structural analysis of samples obtained under different conditions, a possible mechanism for the formation of these distinctive morphologies was proposed. A UV-visible diffuse reflectance spectrum (UV-Vis DRS) of an as-prepared BNdT sample revealed that its band gap energy (Eg) was about 1.984 eV. BNdT photocatalysts exhibited higher photocatalytic activities for the degradation of methyl orange (MO) under visible light irradiation than those for traditional commercial P25 TiO2 and N-doped TiO2 (N-TiO2). BNdT nanowires prepared using a hydroxide concentration of 10 mol·L-1 showed the highest photocatalytic activity among the samples. Over this catalyst, 93.0% degradation of MO (0.01 mmol·L-1) was obtained after irradiation with visible light for 360 min. In addition, there was no significant decrease in photocatalytic activity after the catalyst was used 4 times, indicating that BNdT is a stable photocatalyst for degradation of MO under visible light irradiation.
Neodymium-doped bismuth titanate (Bi3.25Nd0.75Ti3O12, BNdT) nanostructures with different morphologies were synthesized hydrothermally without using surfactant or template. Transmission electron microscopy (TEM) results showed that different morphologies could be fabricated simply by manipulating the concentration of OH- ions during hydrothermal synthesis. Hydroxide ions played an important role in controlling the formation of seeds and the growth rate of BNdT particles. On the basis of structural analysis of samples obtained under different conditions, a possible mechanism for the formation of these distinctive morphologies was proposed. A UV-visible diffuse reflectance spectrum (UV-Vis DRS) of an as-prepared BNdT sample revealed that its band gap energy (Eg) was about 1.984 eV. BNdT photocatalysts exhibited higher photocatalytic activities for the degradation of methyl orange (MO) under visible light irradiation than those for traditional commercial P25 TiO2 and N-doped TiO2 (N-TiO2). BNdT nanowires prepared using a hydroxide concentration of 10 mol·L-1 showed the highest photocatalytic activity among the samples. Over this catalyst, 93.0% degradation of MO (0.01 mmol·L-1) was obtained after irradiation with visible light for 360 min. In addition, there was no significant decrease in photocatalytic activity after the catalyst was used 4 times, indicating that BNdT is a stable photocatalyst for degradation of MO under visible light irradiation.
2012, 28(06): 1489-1496
doi: 10.3866/PKU.WHXB201203221
Abstract:
Composite electrodes consisting of highly ordered, vertically oriented TiO2 nanotube (TiO2-NT) arrays modified with Fe2O3, CuO, and NiO nanoparticles were successfully fabricated by a simple electrochemical anodization and electrodeposition method. Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and UV-Vis diffuse reflectance spectroscopy were used to characterize the structure and optical properties of the resulting Fe2O3/TiO2-NT, CuO/TiO2-NT, and NiO/TiO2-NT composite electrodes. The photoelectrochemical (PEC) activities of the composite electrodes were evaluated using phenol as a model pollutant. Results indicated that transition metal oxide nanoparticles were deposited on the mouth, tube wall, and base of the TiO2-NTs. The PEC activity of the composite electrodes was over twice that of an unmodified TiO2-NT electrode. The Fe2O3/TiO2-NT electrode showed the highest absorption intensity in the visible light region. After treatment for 120 min, the phenol removal efficiency using the Fe2O3/TiO2-NT anode could reach 96%, while it was only 41% for the unmodified TiO2-NT anode. Moreover, the Fe2O3/TiO2-NT electrode tended to generate intermediates of low toxicity. The higher PEC activity of the composite electrodes was attributed to the presence of hetero-nanostructures with high interfacial area comprised of TiO2-NTs and transition metal oxide nanoparticles, which efficiently facilitated electron transfer and inhibited the recombination of photogenerated electron- hole pairs.
Composite electrodes consisting of highly ordered, vertically oriented TiO2 nanotube (TiO2-NT) arrays modified with Fe2O3, CuO, and NiO nanoparticles were successfully fabricated by a simple electrochemical anodization and electrodeposition method. Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and UV-Vis diffuse reflectance spectroscopy were used to characterize the structure and optical properties of the resulting Fe2O3/TiO2-NT, CuO/TiO2-NT, and NiO/TiO2-NT composite electrodes. The photoelectrochemical (PEC) activities of the composite electrodes were evaluated using phenol as a model pollutant. Results indicated that transition metal oxide nanoparticles were deposited on the mouth, tube wall, and base of the TiO2-NTs. The PEC activity of the composite electrodes was over twice that of an unmodified TiO2-NT electrode. The Fe2O3/TiO2-NT electrode showed the highest absorption intensity in the visible light region. After treatment for 120 min, the phenol removal efficiency using the Fe2O3/TiO2-NT anode could reach 96%, while it was only 41% for the unmodified TiO2-NT anode. Moreover, the Fe2O3/TiO2-NT electrode tended to generate intermediates of low toxicity. The higher PEC activity of the composite electrodes was attributed to the presence of hetero-nanostructures with high interfacial area comprised of TiO2-NTs and transition metal oxide nanoparticles, which efficiently facilitated electron transfer and inhibited the recombination of photogenerated electron- hole pairs.
2012, 28(06): 1497-1501
doi: 10.3866/PKU.WHXB201203273
Abstract:
The efficiency of organic light-emitting diodes (OLEDs) was markedly improved using the novel electron transporting material 2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (NBPhen) doped with Cs-derivatives including cesium carbonate (Cs2CO3) and cesium acetate (CH3COOCs) as the n-type dopant. The operating voltage of devices containing these materials as an n-type electron transporting layer (n-ETL) was significantly reduced. Optimized devices with Cs2CO3-doped or CH3COOCsdoped n-ETL (ITO/β-NPB/CBP:5%(w) N-BDAVBi/NBPhen/NBPhen:Cs2CO3 (or CH3COOCs)/Al) exhibited excellent electroluminescent performance with current densities of 551.80 and 527.88 mA·cm-2 at 14 V, corresponding brightnesses of 39750 and 39820 cd·m-2, and current efficiencies of 14.60 and 14.40 cd· A-1 at 10000 cd·m-2, respectively. These results were superior to that of conventional device (ITO/β-NPB/ CBP:5%(w)N-BDAVBi/NBPhen/Cs2CO3/Al) without an n-ETL, which exhibited a current density of 312.39 mA·cm-2 at 14 V, corresponding brightness of 25190 cd·m-2, and current efficiency of 9.45 cd·A-1 at 10000 cd·m-2. In addition, the reason for the increase in the efficiency of n-type doped devices has been analyzed based on the concept of the doping mechanism in organic semiconductors and the energy level scheme of the devices.
The efficiency of organic light-emitting diodes (OLEDs) was markedly improved using the novel electron transporting material 2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (NBPhen) doped with Cs-derivatives including cesium carbonate (Cs2CO3) and cesium acetate (CH3COOCs) as the n-type dopant. The operating voltage of devices containing these materials as an n-type electron transporting layer (n-ETL) was significantly reduced. Optimized devices with Cs2CO3-doped or CH3COOCsdoped n-ETL (ITO/β-NPB/CBP:5%(w) N-BDAVBi/NBPhen/NBPhen:Cs2CO3 (or CH3COOCs)/Al) exhibited excellent electroluminescent performance with current densities of 551.80 and 527.88 mA·cm-2 at 14 V, corresponding brightnesses of 39750 and 39820 cd·m-2, and current efficiencies of 14.60 and 14.40 cd· A-1 at 10000 cd·m-2, respectively. These results were superior to that of conventional device (ITO/β-NPB/ CBP:5%(w)N-BDAVBi/NBPhen/Cs2CO3/Al) without an n-ETL, which exhibited a current density of 312.39 mA·cm-2 at 14 V, corresponding brightness of 25190 cd·m-2, and current efficiency of 9.45 cd·A-1 at 10000 cd·m-2. In addition, the reason for the increase in the efficiency of n-type doped devices has been analyzed based on the concept of the doping mechanism in organic semiconductors and the energy level scheme of the devices.
2012, 28(06): 1502-1508
doi: 10.3866/PKU.WHXB201203201
Abstract:
Atomic force microscopy (AFM) provides a means for characterizing the surface topography and biophysical properties of individual living cells under near-physiological conditions. However, owing to the lack of adequate cellular immobilization methods, AFM imaging of living, suspended mammalian cells is still a big challenge. In this paper, a method is presented for immobilizing individual living B lymphoma cells that combines mechanical trapping with pillar arrays and electrostatic adsorption with poly-L-lysine. In this way, the topography and elasticity changes of individual B lymphoma cells that were stimulated with different concentrations of Rituximab were observed and measured dynamically. When the cell is stimulated by 0.2 mg·mL-1 Rituximab for 2 h, the cell topography becomes more corrugated and Young's modulus decreases from 196 to 183 kPa. When the cell is stimulated by 0.5 mg·mL-1 Rituximab for 2 h, the cell topography changes more significantly and some tubercles appear, and Young's modulus decreases from 234 to 175 kPa. These results thus provide a unique insight into the effects of Rituximab on individual cells.
Atomic force microscopy (AFM) provides a means for characterizing the surface topography and biophysical properties of individual living cells under near-physiological conditions. However, owing to the lack of adequate cellular immobilization methods, AFM imaging of living, suspended mammalian cells is still a big challenge. In this paper, a method is presented for immobilizing individual living B lymphoma cells that combines mechanical trapping with pillar arrays and electrostatic adsorption with poly-L-lysine. In this way, the topography and elasticity changes of individual B lymphoma cells that were stimulated with different concentrations of Rituximab were observed and measured dynamically. When the cell is stimulated by 0.2 mg·mL-1 Rituximab for 2 h, the cell topography becomes more corrugated and Young's modulus decreases from 196 to 183 kPa. When the cell is stimulated by 0.5 mg·mL-1 Rituximab for 2 h, the cell topography changes more significantly and some tubercles appear, and Young's modulus decreases from 234 to 175 kPa. These results thus provide a unique insight into the effects of Rituximab on individual cells.
2012, 28(06): 1509-1519
doi: 10.3866/PKU.WHXB201203272
Abstract:
Ligand-based and receptor-based methods were implemented together to investigate the binding modes of human adenosine A3 anta nists. First, pharmacophore models were developed using the HypoGen program with a training set of 18 diverse human adenosine A3 receptor anta nists from literature. Meanwhile, the three-dimensional structure of A3 receptor was modeled by homology modeling and molecular dynamics, and validated by PROCHECK. Molecular docking was conducted further to investigate receptor-ligand interactions. The pharmacophore model and homology models of A3 receptor matched well, allowing some important information to be obtained. One of the new pharmacophore models was used to screen the MDL drug database report (MDDR) including about 120000 compounds. As a result, eight candidate compounds that can be used for biological evaluation were discovered. These findings are important for the development and discovery of novel selective A3 anta nists and antiasthmatic compounds.
Ligand-based and receptor-based methods were implemented together to investigate the binding modes of human adenosine A3 anta nists. First, pharmacophore models were developed using the HypoGen program with a training set of 18 diverse human adenosine A3 receptor anta nists from literature. Meanwhile, the three-dimensional structure of A3 receptor was modeled by homology modeling and molecular dynamics, and validated by PROCHECK. Molecular docking was conducted further to investigate receptor-ligand interactions. The pharmacophore model and homology models of A3 receptor matched well, allowing some important information to be obtained. One of the new pharmacophore models was used to screen the MDL drug database report (MDDR) including about 120000 compounds. As a result, eight candidate compounds that can be used for biological evaluation were discovered. These findings are important for the development and discovery of novel selective A3 anta nists and antiasthmatic compounds.
2012, 28(06): 1520-1524
doi: 10.3866/PKU.WHXB201203131
Abstract:
We report on synthesis of nanoscale graphene oxide (N ) by modified Hummers’method. Synthesized N particles were surface functionalized by attaching carboxylic acid and polyethylene glycol groups to render them soluble in cell culture medium. The structures and properties of functionalized N were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and zeta potential analyzer. Cell viability studies show that PEG-modified N particles are highly soluble and incur almost no cytotoxicity to A549 cells, which suggest a great potential for the use of N in various biomedical applications.
We report on synthesis of nanoscale graphene oxide (N ) by modified Hummers’method. Synthesized N particles were surface functionalized by attaching carboxylic acid and polyethylene glycol groups to render them soluble in cell culture medium. The structures and properties of functionalized N were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and zeta potential analyzer. Cell viability studies show that PEG-modified N particles are highly soluble and incur almost no cytotoxicity to A549 cells, which suggest a great potential for the use of N in various biomedical applications.
2012, 28(06): 1525-1532
doi: 10.3866/PKU.WHXB201203271
Abstract:
Mesoporous carbon materials are required for application in various areas. In our previous work, we successfully prepared mesoporous carbon with thin pore walls using inexpensive γ-alumina as a template and sucrose as the carbon source, and proposed a mechanism for the synthetic process. In this work, other carbon source was explored to improve the synthetic process and obtain a better understanding of the synthetic mechanism. Compared with sucrose, phenolic resin generated in situ as the carbon precursor can form a complete and robust carbon layer on the template surface in one polymerization and carbonization procedure, simplifying the synthetic process. In addition, the specific surface areas of the carbon materials were greatly increased when phenolic resin was used as the carbon precursor. According to the proposed synthetic mechanism, the mesopores of the carbon materials had two sources: the removal of template particles, and the original pores of the template. When the size of template pores differed significantly from that of the template particles, the obtained carbon materials possessed a bimodal pore size distribution (PSD) at about 4 and 13 nm. In this work, carbon material with a bimodal PSD in the mesopore range was obtained when thin, rod-like alumina was used as the template. The carbon materials possessed ultra large specific surface area (>1800 m2·g-1) and pore volume (>4.5 cm3·g-1), so they were used as electrodes for electric double-layer capacitors. Cyclic voltammograms were nearly rectangular even at a high sweep rate (50 mV·s-1), and the capacitances were relatively high (about 200 F·g-1). When the current density was increased from 0.1 A·g-1 to 1.0 A·g-1, the decrease in specific capacitance was only 10%.
Mesoporous carbon materials are required for application in various areas. In our previous work, we successfully prepared mesoporous carbon with thin pore walls using inexpensive γ-alumina as a template and sucrose as the carbon source, and proposed a mechanism for the synthetic process. In this work, other carbon source was explored to improve the synthetic process and obtain a better understanding of the synthetic mechanism. Compared with sucrose, phenolic resin generated in situ as the carbon precursor can form a complete and robust carbon layer on the template surface in one polymerization and carbonization procedure, simplifying the synthetic process. In addition, the specific surface areas of the carbon materials were greatly increased when phenolic resin was used as the carbon precursor. According to the proposed synthetic mechanism, the mesopores of the carbon materials had two sources: the removal of template particles, and the original pores of the template. When the size of template pores differed significantly from that of the template particles, the obtained carbon materials possessed a bimodal pore size distribution (PSD) at about 4 and 13 nm. In this work, carbon material with a bimodal PSD in the mesopore range was obtained when thin, rod-like alumina was used as the template. The carbon materials possessed ultra large specific surface area (>1800 m2·g-1) and pore volume (>4.5 cm3·g-1), so they were used as electrodes for electric double-layer capacitors. Cyclic voltammograms were nearly rectangular even at a high sweep rate (50 mV·s-1), and the capacitances were relatively high (about 200 F·g-1). When the current density was increased from 0.1 A·g-1 to 1.0 A·g-1, the decrease in specific capacitance was only 10%.
2012, 28(06): 1533-1538
doi: 10.3866/PKU.WHXB201203191
Abstract:
TixV1-xO2 (0≤x≤1) thin films with different molar ratios of V/Ti were prepared on c-plane sapphire (0001) substrates by radio frequency magnetron sputtering. The microstructure and optical properties of the thin films were determined by X-ray diffraction (XRD), Raman spectroscopy, and UV-visible-near infrared (UV-Vis-NIR) spectroscopy. The width of the optical band gap was calculated and the integrated solar transmittance of the films was characterized. As the content of titanium was increased, infrared regulation and thermal hysteresis were gradually reduced until they disappeared. The results show that the band gap of the thin films broadens as the content of titanium increases, causing the optical absorption edge to exhibit a blue shift. Conversely, the band gap narrows as the proportion of vanadium is increased, which causes a red shift of the optical absorption edge.
TixV1-xO2 (0≤x≤1) thin films with different molar ratios of V/Ti were prepared on c-plane sapphire (0001) substrates by radio frequency magnetron sputtering. The microstructure and optical properties of the thin films were determined by X-ray diffraction (XRD), Raman spectroscopy, and UV-visible-near infrared (UV-Vis-NIR) spectroscopy. The width of the optical band gap was calculated and the integrated solar transmittance of the films was characterized. As the content of titanium was increased, infrared regulation and thermal hysteresis were gradually reduced until they disappeared. The results show that the band gap of the thin films broadens as the content of titanium increases, causing the optical absorption edge to exhibit a blue shift. Conversely, the band gap narrows as the proportion of vanadium is increased, which causes a red shift of the optical absorption edge.
2012, 28(06): 1539-1544
doi: 10.3866/PKU.WHXB201204101
Abstract:
Indium oxide (In2O3) was synthesized using a hydrothermal process. The crystallography and microstructure of the synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The In2O3 had a flower-like hierarchical nanostructure and was composed of tiny near-spherical crystals with a diameter of approximately 20 nm. When In2O3 was mixed with CdO in a 1:1 molar ratio, it was found that the resulting In2O3/CdO composite showed an interesting grape-like porous microstructure following calcinations at elevated temperatures. A gas sensor using this In2O3/CdO composite as the sensing material showed higher sensitivity to different concentration of formaldehyde than the gas sensor based on pure flower-like In2O3 nanomaterials. The In2O3/CdO-based sensors showed a high sensitivity to a concentration of 0.05×10-6 formaldehyde at the optimized operating temperature of 410 °C and a od level of selectivity over other possible interference gases such as ethanol, toluene, acetone, methanol, and ammonia. The gas sensing mechanism of In2O3/CdO sensor has been discussed in detail.
Indium oxide (In2O3) was synthesized using a hydrothermal process. The crystallography and microstructure of the synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The In2O3 had a flower-like hierarchical nanostructure and was composed of tiny near-spherical crystals with a diameter of approximately 20 nm. When In2O3 was mixed with CdO in a 1:1 molar ratio, it was found that the resulting In2O3/CdO composite showed an interesting grape-like porous microstructure following calcinations at elevated temperatures. A gas sensor using this In2O3/CdO composite as the sensing material showed higher sensitivity to different concentration of formaldehyde than the gas sensor based on pure flower-like In2O3 nanomaterials. The In2O3/CdO-based sensors showed a high sensitivity to a concentration of 0.05×10-6 formaldehyde at the optimized operating temperature of 410 °C and a od level of selectivity over other possible interference gases such as ethanol, toluene, acetone, methanol, and ammonia. The gas sensing mechanism of In2O3/CdO sensor has been discussed in detail.
2012, 28(06): 1545-1550
doi: 10.3866/PKU.WHXB201203026
Abstract:
This work reports a two-step constant-current anodization approach for the fabrication of an anodic aluminum oxide (AAO) template having an aspect ratio>1000. The effects of oxidation current densities and oxidation time on the morphologies, pore size, and thickness of AAO templates were studied. The results indicated that the morphology and thickness were significantly affected by both the oxidation time and the oxidation current density. High-quality AAO templates with 150-200 nm pore sizes, 200 μm thicknesses, and 1000-1300 aspect ratios could be prepared under a constant-current density of 8 mA?cm-2 and an oxidation time of 18 h. Using the AAO template, Ni nanowire arrays were fabricated by electrochemical deposition and were characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) techniques. The Ni nanowire arrays were parallel to each other, with diameters of 150 nm, lengths of 180-200 μm, and aspect ratios of 1200-1300. These parameters compared favorably with those of the AAO template, thus indicating that it can be used for preparation of one-dimensional nanowire arrays with an ultrahigh aspect ratio. The effects of the aspect ratios on the magnetic characteristics of the Ni nanowire arrays were examined by comparing their coercivities and remanence ratios in parallel and perpendicular directions, respectively. The results indicated that Ni nanowire arrays with an aspect ratio >1000 clearly displayed a magnetic anisotropy, while the arrays with an aspect ratio of 200 did not. Thus an AAO template with an ultrahigh aspect ratio can be fabricated using a two-step constant-current anodization method, and that the AAO template may find applications in the fabrication of one-dimensional, high-aspect ratio nanowire arrays with special optical and magnetic properties.
This work reports a two-step constant-current anodization approach for the fabrication of an anodic aluminum oxide (AAO) template having an aspect ratio>1000. The effects of oxidation current densities and oxidation time on the morphologies, pore size, and thickness of AAO templates were studied. The results indicated that the morphology and thickness were significantly affected by both the oxidation time and the oxidation current density. High-quality AAO templates with 150-200 nm pore sizes, 200 μm thicknesses, and 1000-1300 aspect ratios could be prepared under a constant-current density of 8 mA?cm-2 and an oxidation time of 18 h. Using the AAO template, Ni nanowire arrays were fabricated by electrochemical deposition and were characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) techniques. The Ni nanowire arrays were parallel to each other, with diameters of 150 nm, lengths of 180-200 μm, and aspect ratios of 1200-1300. These parameters compared favorably with those of the AAO template, thus indicating that it can be used for preparation of one-dimensional nanowire arrays with an ultrahigh aspect ratio. The effects of the aspect ratios on the magnetic characteristics of the Ni nanowire arrays were examined by comparing their coercivities and remanence ratios in parallel and perpendicular directions, respectively. The results indicated that Ni nanowire arrays with an aspect ratio >1000 clearly displayed a magnetic anisotropy, while the arrays with an aspect ratio of 200 did not. Thus an AAO template with an ultrahigh aspect ratio can be fabricated using a two-step constant-current anodization method, and that the AAO template may find applications in the fabrication of one-dimensional, high-aspect ratio nanowire arrays with special optical and magnetic properties.
