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2007 Volume 23 Issue 10
2007, 23(10):
Abstract:
2007, 23(10): 1493-1497
doi: 10.1016/S1872-1508(07)60074-6
Abstract:
High-efficiency white organic light-emitting devices (WOLEDs) based on phosphorescent dye bis[2-(4-tert-butylphenyl)benzothiazolato-N,C2’]iridium (acetylacetonate) [(t-bt)2Ir (acac)] doped 4,4’-bis (carbazol-9-yl) biphenyl (CBP) as a yellow emitting layer were fabricated. The structure of the devices is indium tin oxide (ITO)/N,N’-bis-(1-naphthyl)-N,N’-biphenyl-1,1’-biphenyl-4,4’-diamine (NPB)/CBP: (t-bt)2Ir(acac)/NPB/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/8-hydroxyquinoline aluminum(Alq3)/Mg:Ag, and the second NPB layer fromthe anode was used as a blue fluorescent emitter and the first NPB layer was used as a hole transporting layer, the BCP and Alq3 were used as hole blocking and electron transporting layers, respectively. The turn-on voltage of the device was 3 V with a maximumluminance of 15460 cd·m-2 at 16.5 V and maximumluminance efficiency of 7.5 lm·W-1 at 4 V, respectively. The Commission Internationale de I’Eclairage (CIE) coordinates located at (0.33, 0.32) remained stable at the driving voltage higher than 8 V, which is almost consistent with the optimum white CIE of (0.33, 0.33). The purity of white light could be adjusted by doping concentration. The effect of charge carrier trapping and energy transfer on the device performance were also discussed.
High-efficiency white organic light-emitting devices (WOLEDs) based on phosphorescent dye bis[2-(4-tert-butylphenyl)benzothiazolato-N,C2’]iridium (acetylacetonate) [(t-bt)2Ir (acac)] doped 4,4’-bis (carbazol-9-yl) biphenyl (CBP) as a yellow emitting layer were fabricated. The structure of the devices is indium tin oxide (ITO)/N,N’-bis-(1-naphthyl)-N,N’-biphenyl-1,1’-biphenyl-4,4’-diamine (NPB)/CBP: (t-bt)2Ir(acac)/NPB/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/8-hydroxyquinoline aluminum(Alq3)/Mg:Ag, and the second NPB layer fromthe anode was used as a blue fluorescent emitter and the first NPB layer was used as a hole transporting layer, the BCP and Alq3 were used as hole blocking and electron transporting layers, respectively. The turn-on voltage of the device was 3 V with a maximumluminance of 15460 cd·m-2 at 16.5 V and maximumluminance efficiency of 7.5 lm·W-1 at 4 V, respectively. The Commission Internationale de I’Eclairage (CIE) coordinates located at (0.33, 0.32) remained stable at the driving voltage higher than 8 V, which is almost consistent with the optimum white CIE of (0.33, 0.33). The purity of white light could be adjusted by doping concentration. The effect of charge carrier trapping and energy transfer on the device performance were also discussed.
2007, 23(10): 1498-1502
doi: 10.3866/PKU.WHXB20071003
Abstract:
The geometry structure of Mg, Zn doped 32-atom supercell of AlN was optimized by adopting the method of ultra-soft pseudopotential technology of total energy-plane wave based upon the density functional theory(DFT). Cell parameters of both doped and undoped were calculated theoretically. Band structures, binding energies,partial density of states, mulliken charges, and electron density differences of doped AlN crystals were calculated and analyzed in detail. The results revealed that Mg , Zn substituting for Al provided many states of holes. The p-type conduction was obtained. And Mg was a better p-type dopant than Zn.
The geometry structure of Mg, Zn doped 32-atom supercell of AlN was optimized by adopting the method of ultra-soft pseudopotential technology of total energy-plane wave based upon the density functional theory(DFT). Cell parameters of both doped and undoped were calculated theoretically. Band structures, binding energies,partial density of states, mulliken charges, and electron density differences of doped AlN crystals were calculated and analyzed in detail. The results revealed that Mg , Zn substituting for Al provided many states of holes. The p-type conduction was obtained. And Mg was a better p-type dopant than Zn.
2007, 23(10): 1503-1507
doi: 10.1016/S1872-1508(07)60075-8
Abstract:
X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study the effects of reaction conditions (catalysts, reaction temperature and time) on the crystalline phases and morphologies of the carbothermal reaction products in the sol-gel synthesis of Si3N4 nanowires. The results showed that Si3N4 nanowires could be obtained with high yield by using xerogel, which produced a mixture with 5%(w) Fe after carbonization, with a controlling reaction temperature and time of 1300 ℃ and 10 h, respectively. The products obtained by using different additives had different crystalline phases. The content of additives also influenced the morphologies of the products. With increasing the reaction temperature or extending the reaction time, the products underwent a phase transformationof SiOx2N2O→Si3N4. In the presence of metals, Si3N4 nanowires were produced with the help of the vapor-liquid-solid mechanism
X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study the effects of reaction conditions (catalysts, reaction temperature and time) on the crystalline phases and morphologies of the carbothermal reaction products in the sol-gel synthesis of Si3N4 nanowires. The results showed that Si3N4 nanowires could be obtained with high yield by using xerogel, which produced a mixture with 5%(w) Fe after carbonization, with a controlling reaction temperature and time of 1300 ℃ and 10 h, respectively. The products obtained by using different additives had different crystalline phases. The content of additives also influenced the morphologies of the products. With increasing the reaction temperature or extending the reaction time, the products underwent a phase transformationof SiOx2N2O→Si3N4. In the presence of metals, Si3N4 nanowires were produced with the help of the vapor-liquid-solid mechanism
2007, 23(10): 1508-1514
doi: 10.1016/S1872-1508(07)60076-X
Abstract:
Using time domain reflectometry (TDR), dielectric relaxation studies were carried out on binary mixtures of amides (N-methylformamide (NMF), N,N-dimethylformamide (DMF)) with alcohols (1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, and 1-decanol) for various concentrations over the frequency range from 10 MHz to 10 GHz at 303 K. The Kirkwood correlation factor and excess dielectric constant properties were determined and discussed toyield information on the molecular interactions of the systems. The relaxation time varied with the chain length of alcohols and substituted amides were noticed. The Bruggeman plot shows a deviation from linearity. This deviation was attributed to some sort of molecular interaction which may take place between the alcohols and substituted amides. The excess static permittivity and excess inverse relaxation time values varied from negative to positive for all the systems indicating that the solute-solvent interaction existed between alcohols and substituted amides for all the dynamics of the mixture.
Using time domain reflectometry (TDR), dielectric relaxation studies were carried out on binary mixtures of amides (N-methylformamide (NMF), N,N-dimethylformamide (DMF)) with alcohols (1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, and 1-decanol) for various concentrations over the frequency range from 10 MHz to 10 GHz at 303 K. The Kirkwood correlation factor and excess dielectric constant properties were determined and discussed toyield information on the molecular interactions of the systems. The relaxation time varied with the chain length of alcohols and substituted amides were noticed. The Bruggeman plot shows a deviation from linearity. This deviation was attributed to some sort of molecular interaction which may take place between the alcohols and substituted amides. The excess static permittivity and excess inverse relaxation time values varied from negative to positive for all the systems indicating that the solute-solvent interaction existed between alcohols and substituted amides for all the dynamics of the mixture.
2007, 23(10): 1515-1519
doi: 10.3866/PKU.WHXB20071006
Abstract:
Ti-substrate PbO2 (Ti/PbO2) anodeswith Sb-doped SnO2 interlayer were prepared by thermal decomposition-electroplating technique. The behavior and mechanism of the inactivation of Ti/PbO2 anodes were studied by the
accelerated life test, electrochemical impedance spectrum, XRD and SEM-EDX. The results showed that the inactivation of Ti/PbO2 anodes was a developing process. During oxygen evolution, partial active oxygen atoms produced as intermediate product diffuse toward Ti substrate, and they oxidize Pb3+ to Pb4+ in the PbO2 coating to occupy gradually the oxygen vacancies as free electron donors. This results in not only the decrease of conductivity but also a change of intrinsic stresses from tensile stresses to compressive stresses. When the process was finished on the whole, large numbers of active oxygen atoms began to diffuse to Ti substrate. The oxidation of Ti substrate led to
the production of an interfacial stresses. Under the effects of compressive intrinsic stresses and interfacial stresses, PbO2 coating knobs out, subsequently flakes off and Ti/PbO2 anodes become inactive rapidly.
2007, 23(10): 1520-1524
doi: 10.3866/PKU.WHXB20071007
Abstract:
The interaction between atorvastatin calcium (AC) and bovine serum albumin (BSA) was investigated using electrochemical techniques in conjunction with spectroscopy. Both enhancement and abatement actions of BSA on the peak current of AC were discussed in low and high BSA concentration ranges. In pH 7.17 phosphate buffer solution, AC caused an irreversible reduction peak on mercury electrode. With the addition of BSA into the AC solution, the peak current of AC changed and peak potential shifted. The results of linear-sweep voltammetry showed that the molecule of BSA came into being the hydrophobic tiny section where hydrophobic aromatic-group in AC molecule was embedded through hydrophobic interaction when the concentration of BSA was in the range from 1.0×10-7 to 2.0×10-6 mol·L-1. The binding equilibrium constant and binding ratio were calculated as 1.67×105 and 1:1, respectively. Furthermore, the results of UV absorption spectra showed that the UV absorption peak of BSA could red-shift slightly in the presence of AC. The interaction between AC and BSA could result in the change of conformationof BSA. Thus, α-helix structure in BSA was also decreased. The results of IR spectroscopy showed that AC could interact with sulfur-containing and nitrogen-containing groups in BSA molecular.
2007, 23(10): 1525-1530
doi: 10.1016/S1872-1508(07)60077-1
Abstract:
Polarization curve, electrolysis curve, and electrochemical impedance spectroscopy (EIS) were adopted to study the polarization of iron electrode in the concentrated NaOH solution. The results showed that passivation of the iron anode occured more easily at higher temperature, lower alkaline concentration, and greater current density. However, the passivation phenomenon of the iron electrode might become too weak to see under some conditions. The conditions were as follows: temperature 25-35 ℃, current density ≤ 4.7 mA·cm-2, alkaline concentration ≥ 14.5mol·L-1. EIS was used to investigate the impedance change of the electrode surface during the above polarization process. Next, the step characteristic of the iron anode polarization during its super-passivation range in theconcentrated NaOH solution was described.
Polarization curve, electrolysis curve, and electrochemical impedance spectroscopy (EIS) were adopted to study the polarization of iron electrode in the concentrated NaOH solution. The results showed that passivation of the iron anode occured more easily at higher temperature, lower alkaline concentration, and greater current density. However, the passivation phenomenon of the iron electrode might become too weak to see under some conditions. The conditions were as follows: temperature 25-35 ℃, current density ≤ 4.7 mA·cm-2, alkaline concentration ≥ 14.5mol·L-1. EIS was used to investigate the impedance change of the electrode surface during the above polarization process. Next, the step characteristic of the iron anode polarization during its super-passivation range in theconcentrated NaOH solution was described.
2007, 23(10): 1531-1536
doi: 10.1016/S1872-1508(07)60078-3
Abstract:
The photochemical reaction of benz[a]anthracene (B[a]A) on TiO2 particles was investigated by using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and gas chromatography-mass spectrometry (GC-MS). It was confirmed that photocatalytic oxidation of benz[a]anthracene occured on the surface of TiO2 particles, and the surface hydroxyl and oxygen participated in the reactions. The main photochemical product of benz [a] anthracene was benz [a] anthracene-7,12-dione. Possible photochemical mechanism of benz[a]anthracene was also proposed. Under the simulated sun light irradiation (22 mW·cm-2), the process of benz[a]anthracene photodegration on TiO2 particles matches the exponential decay equation, and the half-life time is 6.8 min.
The photochemical reaction of benz[a]anthracene (B[a]A) on TiO2 particles was investigated by using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and gas chromatography-mass spectrometry (GC-MS). It was confirmed that photocatalytic oxidation of benz[a]anthracene occured on the surface of TiO2 particles, and the surface hydroxyl and oxygen participated in the reactions. The main photochemical product of benz [a] anthracene was benz [a] anthracene-7,12-dione. Possible photochemical mechanism of benz[a]anthracene was also proposed. Under the simulated sun light irradiation (22 mW·cm-2), the process of benz[a]anthracene photodegration on TiO2 particles matches the exponential decay equation, and the half-life time is 6.8 min.
2007, 23(10): 1537-1542
doi: 10.3866/PKU.WHXB20071010
Abstract:
Catalysts Ir/γ-Al2O3 were prepared by impregnating γ-Al2O3 with an aqueous solution or microemulsion solution ofH2IrCl6. The catalystswere characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscope (TEM). The catalytic performance of the supportediridiumcatalysts for the selective hydrogenation of avermectin to ivermectin was investigated. Compared with active carbon (AC), α-Al2O3, and TiO2, γ-Al2O3 is a better support in this system. Among Ir, Ru, Pd, and Pt supported on γ-Al2O3, the catalyst Ir/γ-Al2O3 showed the best catalytic activity and selectivity to ivermectin. Ir/γ-Al2O3 prepared by means of microemulsion solution showed the best catalytic activity, but the catalytic selectivity to ivermectin was lower that over Ir/γ-Al2O3 modified with PVP (polyvinylpyrrolidone), which exhibited excellent activity as well as od selectivity.
Catalysts Ir/γ-Al2O3 were prepared by impregnating γ-Al2O3 with an aqueous solution or microemulsion solution ofH2IrCl6. The catalystswere characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscope (TEM). The catalytic performance of the supportediridiumcatalysts for the selective hydrogenation of avermectin to ivermectin was investigated. Compared with active carbon (AC), α-Al2O3, and TiO2, γ-Al2O3 is a better support in this system. Among Ir, Ru, Pd, and Pt supported on γ-Al2O3, the catalyst Ir/γ-Al2O3 showed the best catalytic activity and selectivity to ivermectin. Ir/γ-Al2O3 prepared by means of microemulsion solution showed the best catalytic activity, but the catalytic selectivity to ivermectin was lower that over Ir/γ-Al2O3 modified with PVP (polyvinylpyrrolidone), which exhibited excellent activity as well as od selectivity.
2007, 23(10): 1543-1552
doi: 10.3866/PKU.WHXB20071011
Abstract:
(2+1) Resonance multiphoton ionization (REMPI) spectra of HX(X=Cl, Br and I) were recorded and analyzed by simulation calculation to derive rotational constants, band origins and isotope shift values for a number of vibrational bands of Ω states. Our data for HCl compared nicely with those derived by Green et al. using conventional analysis methods. Newspectroscopic parameters were derived for 8 vibrational bands which were assigned to the V(1∑+) state, for v'=4 of the E(1∑+) state as well as for 5 new bands in HBr . New spectroscopic parameters were derived for 4 vibrational bands which are assigned to the V state and for v'=1 of the E state in HI. Anomalies in energy level spacings, rotational parameters and isotope shift values were observed as being largely due to homogeneous interactions between the V and the E states. Variations observed in the intensity ratio of O and S line series to Q line series in vibrational bands of the E and V states for HCl and HBr were discussed and mechanisms of two photon excitation processes were proposed.
(2+1) Resonance multiphoton ionization (REMPI) spectra of HX(X=Cl, Br and I) were recorded and analyzed by simulation calculation to derive rotational constants, band origins and isotope shift values for a number of vibrational bands of Ω states. Our data for HCl compared nicely with those derived by Green et al. using conventional analysis methods. Newspectroscopic parameters were derived for 8 vibrational bands which were assigned to the V(1∑+) state, for v'=4 of the E(1∑+) state as well as for 5 new bands in HBr . New spectroscopic parameters were derived for 4 vibrational bands which are assigned to the V state and for v'=1 of the E state in HI. Anomalies in energy level spacings, rotational parameters and isotope shift values were observed as being largely due to homogeneous interactions between the V and the E states. Variations observed in the intensity ratio of O and S line series to Q line series in vibrational bands of the E and V states for HCl and HBr were discussed and mechanisms of two photon excitation processes were proposed.
2007, 23(10): 1553-1559
doi: 10.3866/PKU.WHXB20071012
Abstract:
SbOx+SnO2 were prepared by thermal decomposition as intermediate layer of Ti based MnO2 anode. Service lives of the anodes with or without SbOx +SnO2 intermediate layer in 0.5 mol·L -1 H2SO4 solution were investigated by using accelerated electrolysis. Polarization curves and cyclic voltammetric curves (CVs) were utilized to analyze Cl2 evolution reaction (CER) of the oxide electrodes. Cyclic voltammetric curves and electrochemical impedance spectroscopy (EIS) were utilized with the aim of obtaining detailed information related to the changes of the inner structure during the electrolysis. The results indicated that the main reason for the deactivation of MnO2 anodes was the passivation derived from the increase of the thickness of the insulating TiO2 layer. With the introduction of intermediate layer, the resistance between Ti base and active coating was lowered and the increase of resistance during the electrolysis was postponed dramatically, so the service lives were improved remarkably.
SbOx+SnO2 were prepared by thermal decomposition as intermediate layer of Ti based MnO2 anode. Service lives of the anodes with or without SbOx +SnO2 intermediate layer in 0.5 mol·L -1 H2SO4 solution were investigated by using accelerated electrolysis. Polarization curves and cyclic voltammetric curves (CVs) were utilized to analyze Cl2 evolution reaction (CER) of the oxide electrodes. Cyclic voltammetric curves and electrochemical impedance spectroscopy (EIS) were utilized with the aim of obtaining detailed information related to the changes of the inner structure during the electrolysis. The results indicated that the main reason for the deactivation of MnO2 anodes was the passivation derived from the increase of the thickness of the insulating TiO2 layer. With the introduction of intermediate layer, the resistance between Ti base and active coating was lowered and the increase of resistance during the electrolysis was postponed dramatically, so the service lives were improved remarkably.
2007, 23(10): 1560-1564
doi: 10.3866/PKU.WHXB20071013
Abstract:
The structure of β-HMX and several complexes with H+ or NH+4 were optimized using the density functiona theory(DFT)at the B3P86/6-31G** level. Meanwhile, the bond dissociation energies of the weakest N—NO2 for β-HMX and the complexes were obtained by the same calculation method. It was found that the geometrical configuration of the HMX in the complexes differed significantly from that of β-HMX. On the other hand, one of the N—NO2 bonds of HMX was activated due to the combination of H+ with HMX, but this activation was unobvious for the complexes with NH+4 . The N—NO2 bond dissociation energies of two complexes with H+ decreased about 20 and 82 kJ·mol-1, respectively, in comparison with that of β-HMX. However, the N—NO2 bond dissociation energy for the complex with NH+4 decreased only about 8 kJ·mol-1. It indicated that the H+ could promote the initial thermal decomposition of N—NO2 bond of β-HMX, but this initial decomposition was slightly influenced by NH+4.
The structure of β-HMX and several complexes with H+ or NH+4 were optimized using the density functiona theory(DFT)at the B3P86/6-31G** level. Meanwhile, the bond dissociation energies of the weakest N—NO2 for β-HMX and the complexes were obtained by the same calculation method. It was found that the geometrical configuration of the HMX in the complexes differed significantly from that of β-HMX. On the other hand, one of the N—NO2 bonds of HMX was activated due to the combination of H+ with HMX, but this activation was unobvious for the complexes with NH+4 . The N—NO2 bond dissociation energies of two complexes with H+ decreased about 20 and 82 kJ·mol-1, respectively, in comparison with that of β-HMX. However, the N—NO2 bond dissociation energy for the complex with NH+4 decreased only about 8 kJ·mol-1. It indicated that the H+ could promote the initial thermal decomposition of N—NO2 bond of β-HMX, but this initial decomposition was slightly influenced by NH+4.
2007, 23(10): 1565-1571
doi: 10.3866/PKU.WHXB20071014
Abstract:
Several classical water models (SPC, TIPnP (n=3-5)) and polarizable models (POL3, AMOEBA, SPC-FQ, TIP4P-FQ), combining the results of ab initio methods were employed to study the properties of water clusters, such as structures, dipoles, induced dipoles, charge transfer, polarized energies, many-body energies and binding energies, and were evaluated against the related literature works. Whether the polarized effects can be neglected in the modelng of water clusters was judged by the total potential and the decomposed energy terms. All in all, the polarizable water models, especially the induced multiple model (AMOEBA), do better job than classical fixed charge models. Fluctuating charge and four sites model is more realistic to be applied to the biological sytems in consideration of the balance of efficiency and accuracy. The comparable studies of this paper provide a reference for developing the polarized models and applying themto other systems.
Several classical water models (SPC, TIPnP (n=3-5)) and polarizable models (POL3, AMOEBA, SPC-FQ, TIP4P-FQ), combining the results of ab initio methods were employed to study the properties of water clusters, such as structures, dipoles, induced dipoles, charge transfer, polarized energies, many-body energies and binding energies, and were evaluated against the related literature works. Whether the polarized effects can be neglected in the modelng of water clusters was judged by the total potential and the decomposed energy terms. All in all, the polarizable water models, especially the induced multiple model (AMOEBA), do better job than classical fixed charge models. Fluctuating charge and four sites model is more realistic to be applied to the biological sytems in consideration of the balance of efficiency and accuracy. The comparable studies of this paper provide a reference for developing the polarized models and applying themto other systems.
2007, 23(10): 1572-1576
doi: 10.3866/PKU.WHXB20071015
Abstract:
The herbicide of alachlor was incorporated into the channels of MCM-41-type mesoporous silica (M41) by using an impregnation method. Surface hydrophobic modification of the assembly of alachlor-MCM-41 (Ach/M41), via a gas-solid reaction with 1,1,1,3,3,3-hexamethyldisilazane (HMDS), gave rise to an efficient sustained-release system (Ach/TMS-M41). The resulting Ach/TMS-M41 not only retained high alachlor loading capacity but also possessed prolonged alachlor release time. The characterization results of XRD, nitrogen adsorption/desorption, FT-IR, and TG analysis showed that the M41 retained its structural integrity during the alachlor-loading process and alachlor was dispersed completely in the channels of MCM-41 with a mass ratio of alachlor [m (alachlor)/m(alachlor-MCM-41)] as high as 0.381 g·g-1 (mass fraction 27.6%). The release properties of Ach/M41 and Ach/TMS-M41 in water were investigated. 62% and 38.1% of alachlor were released from Ach/M41 and Ach/TMS-M41 ofter 6 days, respectively, which indicated that hydrophobic modification of MCM-41 was conducive to sustained-release of alachlor. Furthermore, the framework of the mesoporous silica protected the encapsulated alachlor against ultraviolet light irradiation.
The herbicide of alachlor was incorporated into the channels of MCM-41-type mesoporous silica (M41) by using an impregnation method. Surface hydrophobic modification of the assembly of alachlor-MCM-41 (Ach/M41), via a gas-solid reaction with 1,1,1,3,3,3-hexamethyldisilazane (HMDS), gave rise to an efficient sustained-release system (Ach/TMS-M41). The resulting Ach/TMS-M41 not only retained high alachlor loading capacity but also possessed prolonged alachlor release time. The characterization results of XRD, nitrogen adsorption/desorption, FT-IR, and TG analysis showed that the M41 retained its structural integrity during the alachlor-loading process and alachlor was dispersed completely in the channels of MCM-41 with a mass ratio of alachlor [m (alachlor)/m(alachlor-MCM-41)] as high as 0.381 g·g-1 (mass fraction 27.6%). The release properties of Ach/M41 and Ach/TMS-M41 in water were investigated. 62% and 38.1% of alachlor were released from Ach/M41 and Ach/TMS-M41 ofter 6 days, respectively, which indicated that hydrophobic modification of MCM-41 was conducive to sustained-release of alachlor. Furthermore, the framework of the mesoporous silica protected the encapsulated alachlor against ultraviolet light irradiation.
2007, 23(10): 1577-1582
doi: 10.3866/PKU.WHXB20071016
Abstract:
A first-principle computational method based on the hybrid density functional theory was used to calculate the inelastic electron tunneling spectra (IETS) of 4,4’-biphenyldithiol molecular electronic devices. The influence of distance of electrodes on the IETS was investigated. The molecular geometric structures and the IETS were studied for different distances between two ld electrodes. When the distance of the electrodes changed, the numerical results showed that the IETS had a sensitive variation, which demonstrated that the IETS was a od method to explore microstructure of molecular devices. The vibrational modes with direction perpendicular to the electrode surface gave a great contribution to the IETS.
A first-principle computational method based on the hybrid density functional theory was used to calculate the inelastic electron tunneling spectra (IETS) of 4,4’-biphenyldithiol molecular electronic devices. The influence of distance of electrodes on the IETS was investigated. The molecular geometric structures and the IETS were studied for different distances between two ld electrodes. When the distance of the electrodes changed, the numerical results showed that the IETS had a sensitive variation, which demonstrated that the IETS was a od method to explore microstructure of molecular devices. The vibrational modes with direction perpendicular to the electrode surface gave a great contribution to the IETS.
2007, 23(10): 1583-1588
doi: 10.3866/PKU.WHXB20071017
Abstract:
Magnetic chitosan nanoparticles(Fe2O3-CS) were prepared in microemulsion by crosslinking method. The transmission electron microscopy (TEM), Fourier transforminfrared spectrophotometry (FT-IR) and vibrating specimen magnetometer (VSM) were used to characterize the nanoparticles. The mean diameter of the particles was about 40 nm with od dispersibility and magnetic response. The bovine serum albumin (BSA) was connected onto the surface of the magnetic nanoparticles with carbodiimide hydrochloride (EDC) as the activator. The products were then characterized by atomic force microscope (AFM) and ultraviolet spectrometer (UV). The results showed that the nanoparticles had a od adsorbability of the BSA. The adsorption isotherm of the BSA on the magnetic chitosan microspheres basicly obeyed the Langmuir model, with a maximum adsorption capacity of 250 mg·g -1 and an adsorption equilibrium constant of 0.007 L·mg-1. The stability of the particles-BSA complex in phosphate buffer solution (PBS) with different pH was also studied. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that BSA was desorbed frommagnetic particles under alkaline condition.
Magnetic chitosan nanoparticles(Fe2O3-CS) were prepared in microemulsion by crosslinking method. The transmission electron microscopy (TEM), Fourier transforminfrared spectrophotometry (FT-IR) and vibrating specimen magnetometer (VSM) were used to characterize the nanoparticles. The mean diameter of the particles was about 40 nm with od dispersibility and magnetic response. The bovine serum albumin (BSA) was connected onto the surface of the magnetic nanoparticles with carbodiimide hydrochloride (EDC) as the activator. The products were then characterized by atomic force microscope (AFM) and ultraviolet spectrometer (UV). The results showed that the nanoparticles had a od adsorbability of the BSA. The adsorption isotherm of the BSA on the magnetic chitosan microspheres basicly obeyed the Langmuir model, with a maximum adsorption capacity of 250 mg·g -1 and an adsorption equilibrium constant of 0.007 L·mg-1. The stability of the particles-BSA complex in phosphate buffer solution (PBS) with different pH was also studied. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that BSA was desorbed frommagnetic particles under alkaline condition.
2007, 23(10): 1589-1593
doi: 10.3866/PKU.WHXB20071018
Abstract:
The electrochemiluminescence (ECL) behaviour of a new reagent 10,10'-dimethyl-3,3'-disulfo-9,9'-biacridine (DMDSBA) was studied. The effects of the electrochemical parameters, the reaction medium and pH on the ECL were investigated in detail. It was found that the new reagent DMDSBA gave a strong electrochemiluminescence in KNO3 solution when an appropriate voltage was applied on glassy carbon electrode. Under the optimum conditions, the natural logarithm of the ECL intensity of DMDSBA has a od linear relationship with the natural logarithm of the concentration of DMDSBA in the range of 1.0×10-5 -1.0×10-8 mol·L-1, the detection limit of DMDSBA was 2.3×10-9 mol·L -1. The cyclic voltammetry, fluorescence spetrum and ECL spetrum for this ECL system have also been investigated in detail, based on which a possible mechanismfor the ECL of DMDSBA was proposed.
2007, 23(10): 1594-1598
doi: 10.3866/PKU.WHXB20071019
Abstract:
The molecular geometries of porphin and those modified with —CH=CH2, —COCH3, —CHOHCH3, —CHNH2CH3, or —CHSHCH3 groups were optimized at the B3LYP/6-31G (d, p) level of density functional theory (DFT). At the same time, their absorption spectra and 1H NMR were also calculated. The results illustrated that these substitution groups had differential spatial positions and did not disturb the structure of porphin extremely. Meanwhile, they have re-adjusted the contribution of atomic charges of porphin and then have changed the LUMO-HOMO energy gaps of porphin. As a result, the absorption spectra and 1H NMR were changed accordingly.
The molecular geometries of porphin and those modified with —CH=CH2, —COCH3, —CHOHCH3, —CHNH2CH3, or —CHSHCH3 groups were optimized at the B3LYP/6-31G (d, p) level of density functional theory (DFT). At the same time, their absorption spectra and 1H NMR were also calculated. The results illustrated that these substitution groups had differential spatial positions and did not disturb the structure of porphin extremely. Meanwhile, they have re-adjusted the contribution of atomic charges of porphin and then have changed the LUMO-HOMO energy gaps of porphin. As a result, the absorption spectra and 1H NMR were changed accordingly.
2007, 23(10): 1599-1602
doi: 10.3866/PKU.WHXB20071020
Abstract:
Nanorod-like SrTiO3 crystals starting from SrCO3 and TiO2 were synthesized by a composite-hydroxide- mediated (CHM) method at 200 ℃ for 48 h. The as-synthesized SrTiO3 nanorods with length from 500 to 800 nm, width about 100-150 nm were assembled by lots of regular nano-sheets. When a small amount of deionized water was added in the vessel during synthesis process, the shape of the crystals turned into cubes. The growth mechanism of SrTiO3 nanorods was discussed and it was found that the formation of SrTiO3 nanorods involved four steps: dissolution→homogeneous nucleation→growth of regular sheets→coordinative self-assembles. The influences of water were discussed in detail.
Nanorod-like SrTiO3 crystals starting from SrCO3 and TiO2 were synthesized by a composite-hydroxide- mediated (CHM) method at 200 ℃ for 48 h. The as-synthesized SrTiO3 nanorods with length from 500 to 800 nm, width about 100-150 nm were assembled by lots of regular nano-sheets. When a small amount of deionized water was added in the vessel during synthesis process, the shape of the crystals turned into cubes. The growth mechanism of SrTiO3 nanorods was discussed and it was found that the formation of SrTiO3 nanorods involved four steps: dissolution→homogeneous nucleation→growth of regular sheets→coordinative self-assembles. The influences of water were discussed in detail.
2007, 23(10): 1603-1606
doi: 10.3866/PKU.WHXB20071021
Abstract:
The anatase TiO2 nanowire arrays with 60 nm diameter and 20 nm diameter were prepared within the nanochannels of anodic aluminumoxide (AAO) template by an electrochemically induced sol-gel method. Atomic force microscopy (AFM) technique was applied to map topographic image at half-contact mode and to measure current-voltage characteristics of individual TiO2 nanowire at contact mode. The I -V characteristics of individual TiO2 nanowire by AFM revealed semiconductor characteristics. The bias voltage resulting in a measurable current on individual TiO2 nanowire was much lower than that on the bulk TiO2 materials, and its value increased with the diameter of individual nanowire decreasing.
The anatase TiO2 nanowire arrays with 60 nm diameter and 20 nm diameter were prepared within the nanochannels of anodic aluminumoxide (AAO) template by an electrochemically induced sol-gel method. Atomic force microscopy (AFM) technique was applied to map topographic image at half-contact mode and to measure current-voltage characteristics of individual TiO2 nanowire at contact mode. The I -V characteristics of individual TiO2 nanowire by AFM revealed semiconductor characteristics. The bias voltage resulting in a measurable current on individual TiO2 nanowire was much lower than that on the bulk TiO2 materials, and its value increased with the diameter of individual nanowire decreasing.
2007, 23(10): 1607-1611
doi: 10.3866/PKU.WHXB20071022
Abstract:
Cyclic voltammetry, steady polarization and alternating current impedance were used to study the mechanism of Cr(III) electrodeposition in carboxylic acid-urea system. The results indicated that the trivalent chromium ion t three electrons by two steps in which one electron was t firstly and two secondly. The two steps were all nonreversible reductions with chemical transformation. The kinetic parameters, such as reaction orders, Tafel slopes and apparent transfer coefficients calculated from the theoretical kinetics equation were agreed well with the experimentally measured ones.
Cyclic voltammetry, steady polarization and alternating current impedance were used to study the mechanism of Cr(III) electrodeposition in carboxylic acid-urea system. The results indicated that the trivalent chromium ion t three electrons by two steps in which one electron was t firstly and two secondly. The two steps were all nonreversible reductions with chemical transformation. The kinetic parameters, such as reaction orders, Tafel slopes and apparent transfer coefficients calculated from the theoretical kinetics equation were agreed well with the experimentally measured ones.
2007, 23(10): 1612-1616
doi: 10.3866/PKU.WHXB20071023
Abstract:
1H-NMR, Dynamic light scattering (DLS), and transmission electron microscopy (TEM) were used to study the effect of block ratio on the self-aggregation behavior of poly (ethylene glycol)-b-[2-(dimethylamino) ethyl methacrylate] (PEG-b-PDMAEMA) copolymers in water. The results revealed that the block ratio of the two blocks was the key factor to its micellization process: the PEG mass content less than 33% is the precondition for the copolymer to show its unique pH- and thermo-responsive micellization behavior. Also, the micellization process was closely related to the block ratio of the two constitutional blocks. The hydrogen bonding interaction between different groups in the polymeric system may account for it.
1H-NMR, Dynamic light scattering (DLS), and transmission electron microscopy (TEM) were used to study the effect of block ratio on the self-aggregation behavior of poly (ethylene glycol)-b-[2-(dimethylamino) ethyl methacrylate] (PEG-b-PDMAEMA) copolymers in water. The results revealed that the block ratio of the two blocks was the key factor to its micellization process: the PEG mass content less than 33% is the precondition for the copolymer to show its unique pH- and thermo-responsive micellization behavior. Also, the micellization process was closely related to the block ratio of the two constitutional blocks. The hydrogen bonding interaction between different groups in the polymeric system may account for it.
2007, 23(10): 1617-1621
doi: 10.3866/PKU.WHXB20071024
Abstract:
New Fe-W-ZrO2 nano-composite layers were prepared by composite electrodeposition technology. The morphology, composition, structure, hardness and corrosion resistance properties of the coatings were systematically characterized by means of SEM, EDS, X-ray diffraction and potentiostat methods. The results showed that when the mass composition of the obtained Fe-W-ZrO2 composite coating was Fe 38.3%(w)、W 52.7%(w)、ZrO2 9.0%(w), the crack condition of Fe-W alloy coatings was improved markedly by the dispersion strengthening effect of the ZrO2 nano-particle. Meanwhile, the composite coatings presented an obvious amorphous characteristics, compact structure, and uniform composition. In comparison with Fe-W alloy coatings, not only the hardness of the composite coatings was higher, but also the corrosion resistance was enhanced evidently in 3.5%(w) NaCl and 0.5 mol·L-1 H2SO4 solution at 30 ℃.
New Fe-W-ZrO2 nano-composite layers were prepared by composite electrodeposition technology. The morphology, composition, structure, hardness and corrosion resistance properties of the coatings were systematically characterized by means of SEM, EDS, X-ray diffraction and potentiostat methods. The results showed that when the mass composition of the obtained Fe-W-ZrO2 composite coating was Fe 38.3%(w)、W 52.7%(w)、ZrO2 9.0%(w), the crack condition of Fe-W alloy coatings was improved markedly by the dispersion strengthening effect of the ZrO2 nano-particle. Meanwhile, the composite coatings presented an obvious amorphous characteristics, compact structure, and uniform composition. In comparison with Fe-W alloy coatings, not only the hardness of the composite coatings was higher, but also the corrosion resistance was enhanced evidently in 3.5%(w) NaCl and 0.5 mol·L-1 H2SO4 solution at 30 ℃.
2007, 23(10): 1622-1626
doi: 10.3866/PKU.WHXB20071025
Abstract:
The thermal behavior of polyurethane adhesive in air atmosphere was investigated by thermogravimetry (TG) and derivative thermogravimetry (DTG). The kinetic parameters were evaluated by TG method and dynamic method, and the isoconversional method was employed to verify the values. The results showed that there were three main decomposition stages in the DTG curves. The apparent activation energy values determined using the TG method were 144.31-148.35 kJ·mol-1 for the first stage of decomposition, 196.96-204.26 kJ·mol-1 for the second stage and 202.97-205.27 kJ·mol -1 for the third stage. The non-isothermal degradation was found to be first order reaction, and the activation energy increased with the increase of mass loss. The lifetime estimate indicated the maximum lifetime of polyurethane under 35 ℃in air to be 10 years . The kinetic data suggested that polyurethane adhesive had excellent thermal stability.
2007, 23(10): 1627-1630
doi: 10.3866/PKU.WHXB20071026
Abstract:
From reasonable suppositions on binding process and Langmuir’s binding theory, the interactions between 5-fluorouracil (5-FU) and bovine serumalbumin (BSA) were investigated by the isothermal titration calorimetry (ITC) and the circular dichroism (CD) spectrometry at 298.15 K. The results showed that there were two classes of binding sites on a protein (BSA) molecule for the 5-fluorouracil. For the first class of binding, N=(54.0±0.3), ⊿H0=(30.0±0.4) kJ·mol-1 (endothermal), ⊿S0=(196.0±2.6) J·mol-1·K-1 (entropy increasing), ⊿G0=(-28.4±0.3) kJ·mol-1; for the second class of binding, N=(77.0±0.4), ⊿H0=(-20.0±0.4) kJ·mol-1 (exothermal), ⊿S0=(28.6±0.3) J·mol-1·K-1 (entropy increasing), ⊿G0=(-28.5±0.2) kJ·mol -1. The interactions between 5-fluorouracil and BSA induced the relative contents of secondary structure units of protein (BSA) to change in two classes of binding processes.
From reasonable suppositions on binding process and Langmuir’s binding theory, the interactions between 5-fluorouracil (5-FU) and bovine serumalbumin (BSA) were investigated by the isothermal titration calorimetry (ITC) and the circular dichroism (CD) spectrometry at 298.15 K. The results showed that there were two classes of binding sites on a protein (BSA) molecule for the 5-fluorouracil. For the first class of binding, N=(54.0±0.3), ⊿H0=(30.0±0.4) kJ·mol-1 (endothermal), ⊿S0=(196.0±2.6) J·mol-1·K-1 (entropy increasing), ⊿G0=(-28.4±0.3) kJ·mol-1; for the second class of binding, N=(77.0±0.4), ⊿H0=(-20.0±0.4) kJ·mol-1 (exothermal), ⊿S0=(28.6±0.3) J·mol-1·K-1 (entropy increasing), ⊿G0=(-28.5±0.2) kJ·mol -1. The interactions between 5-fluorouracil and BSA induced the relative contents of secondary structure units of protein (BSA) to change in two classes of binding processes.
2007, 23(10): 1631-1636
doi: 10.3866/PKU.WHXB20071027
Abstract:
Based on the cooperation of the fluorated polyurethane and nano silicon oxide, superhydrophobic coating had been successfully fabricated on the surface of aluminium alloy. The superhydrophobic coating was characterized and investigated by FT-IR、SEM and electrochemical measurement. The FT-IR result showed that silane coupling reagent (A1100) had been grafted on the surface of the nano-silicon oxide. Scanning electronic microscopy(SEM) and optical contact angle meter (OWA) indicated that rough structure was present on the surface of the coating, and the contact angle could reach up to 156°with sliding angle smaller than 5°. The results of electrochemical measurements (EIS and polarization curve) showed that anti-corrosion property of aluminiumalloy had been greatly improved.
Based on the cooperation of the fluorated polyurethane and nano silicon oxide, superhydrophobic coating had been successfully fabricated on the surface of aluminium alloy. The superhydrophobic coating was characterized and investigated by FT-IR、SEM and electrochemical measurement. The FT-IR result showed that silane coupling reagent (A1100) had been grafted on the surface of the nano-silicon oxide. Scanning electronic microscopy(SEM) and optical contact angle meter (OWA) indicated that rough structure was present on the surface of the coating, and the contact angle could reach up to 156°with sliding angle smaller than 5°. The results of electrochemical measurements (EIS and polarization curve) showed that anti-corrosion property of aluminiumalloy had been greatly improved.
2007, 23(10): 1637-1641
doi: 10.3866/PKU.WHXB20071028
Abstract:
The various structure solar cells based on the blend of MEH-PPV(poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene) )and PCBM(1-(3-methoxycarbonyl)-propyl-1-1-phenyl-(6,6)C61) )as acceptor were fabricated. A mechanism of the influence of device structure on device performance was analyzed in detail. The result showed an increase of open circuit voltage and improvement of electric charge transport owing to the inserting of PEDOT:PSS (4083)(poly(3,4-ethylene dioxythiophene:poly(styrene sulphonic acid)). We also raised the short-circuit electric current and fill factor of device adopting LiF/Al negative electricity structure, and obtained an open circuit voltage of 0.8 V, short circuit current density of 3.40 mA·cm-2 and fill factor of 52.1% under 100 mA·cm-2 air-mass 1.5 solar simulator illumination, yielding a 1.43%power conversion efficiency. The influence of different solvents on device performance was studieds. The results showed that 1,2-dichlorobenzene was advantageous to the formation of od body heterojunction, and the performance of the corresponding device was excellence. We also analyzed the mechanism of the solvent influence on the device performance by light and dark I-V curve, photosensitivity, AFM, and gave some reasonable explainations.
The various structure solar cells based on the blend of MEH-PPV(poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene) )and PCBM(1-(3-methoxycarbonyl)-propyl-1-1-phenyl-(6,6)C61) )as acceptor were fabricated. A mechanism of the influence of device structure on device performance was analyzed in detail. The result showed an increase of open circuit voltage and improvement of electric charge transport owing to the inserting of PEDOT:PSS (4083)(poly(3,4-ethylene dioxythiophene:poly(styrene sulphonic acid)). We also raised the short-circuit electric current and fill factor of device adopting LiF/Al negative electricity structure, and obtained an open circuit voltage of 0.8 V, short circuit current density of 3.40 mA·cm-2 and fill factor of 52.1% under 100 mA·cm-2 air-mass 1.5 solar simulator illumination, yielding a 1.43%power conversion efficiency. The influence of different solvents on device performance was studieds. The results showed that 1,2-dichlorobenzene was advantageous to the formation of od body heterojunction, and the performance of the corresponding device was excellence. We also analyzed the mechanism of the solvent influence on the device performance by light and dark I-V curve, photosensitivity, AFM, and gave some reasonable explainations.
2007, 23(10): 1642-1646
doi: 10.3866/PKU.WHXB20071029
Abstract:
The lithium ion conductor LiTi2(PO4)3 has a very high ion exchange selectivity to Na+ in sodium chloride solution. The ion exchange behavior of Na/Li for LiTi2(PO4)3 in NaCl solution was investigated. The experimental results showed that the Na/Li ion exchange reaction rate increased obviously for LiTi2 (PO4)3 with increasing temperature, and the Na/Li ion exchange kinetics process of LiTi2(PO4)3 in sodium chloride solution could be represented approximately by the equation of JMAK(Johnson-Mehl-Aurami-Kalmo rav). The dissolution behaviors of LiTi2(PO4)3 in water and NaCl solution were investigated, the results showed that higher temperature, acid or alkali environment could enhance the dissolution of LiTi2(PO4)3.
The lithium ion conductor LiTi2(PO4)3 has a very high ion exchange selectivity to Na+ in sodium chloride solution. The ion exchange behavior of Na/Li for LiTi2(PO4)3 in NaCl solution was investigated. The experimental results showed that the Na/Li ion exchange reaction rate increased obviously for LiTi2 (PO4)3 with increasing temperature, and the Na/Li ion exchange kinetics process of LiTi2(PO4)3 in sodium chloride solution could be represented approximately by the equation of JMAK(Johnson-Mehl-Aurami-Kalmo rav). The dissolution behaviors of LiTi2(PO4)3 in water and NaCl solution were investigated, the results showed that higher temperature, acid or alkali environment could enhance the dissolution of LiTi2(PO4)3.
2007, 23(10): 1647-1651
doi: 10.3866/PKU.WHXB20071030
Abstract:
The geometries of various isomers of heterofullerenes C20-2nX2n (X=B, N; n=1, 2, 3, 4) were fully optimized at the B3LYP/6-31G* density functional level of theory, and the corresponding frequency calculations at the same level were used to characterize the ground state structures. The substitutional patterns, electronic structure, strain, and aromaticity of these heterofullerenes have been investigated. In general, nitrogen doping could not significantly decrease the strain of the cage. The strain of C12N8 was even larger than that of C20, this nitrogen analogue was extraordinarily unstable. The two most stable isomers of C18B2, 1,14-C18B2 and 1,3-C18B2, both have large HOMO-LUMO gaps and binding energies. They were highly aromatic. The strains of these two molecules were very small, compared with that of C20.1,14-C18B2 and 1,3-C18B2 were predicted to be highly stable small heterofullerenes, these two configurational isomers could be distinguished fromeach other by their IR spectra.
The geometries of various isomers of heterofullerenes C20-2nX2n (X=B, N; n=1, 2, 3, 4) were fully optimized at the B3LYP/6-31G* density functional level of theory, and the corresponding frequency calculations at the same level were used to characterize the ground state structures. The substitutional patterns, electronic structure, strain, and aromaticity of these heterofullerenes have been investigated. In general, nitrogen doping could not significantly decrease the strain of the cage. The strain of C12N8 was even larger than that of C20, this nitrogen analogue was extraordinarily unstable. The two most stable isomers of C18B2, 1,14-C18B2 and 1,3-C18B2, both have large HOMO-LUMO gaps and binding energies. They were highly aromatic. The strains of these two molecules were very small, compared with that of C20.1,14-C18B2 and 1,3-C18B2 were predicted to be highly stable small heterofullerenes, these two configurational isomers could be distinguished fromeach other by their IR spectra.
2007, 23(10): 1652-1656
doi: 10.3866/PKU.WHXB20071031
Abstract:
The dynamic dilational viscoelaticity properties of sodium 2,5-dipropyl-4-undecylbenzene sulfonate (3-11-3) at air/water interface were investigated by drop shape analysis. The influences of time, surface pressure, dilational frequency and concentration on surface dilational modulus and phase angle were explored. The experiment results showed that the film was elastic in lower surface pressure range, which was believed to be dominated by the in-surface process. In contrast, the viscous behavior become noticeable in higher surface pressure range, which indicates the diffusion-exchange process between bulk and surface dominates the nature of film.
The dynamic dilational viscoelaticity properties of sodium 2,5-dipropyl-4-undecylbenzene sulfonate (3-11-3) at air/water interface were investigated by drop shape analysis. The influences of time, surface pressure, dilational frequency and concentration on surface dilational modulus and phase angle were explored. The experiment results showed that the film was elastic in lower surface pressure range, which was believed to be dominated by the in-surface process. In contrast, the viscous behavior become noticeable in higher surface pressure range, which indicates the diffusion-exchange process between bulk and surface dominates the nature of film.
