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2015 Volume 31 Issue 11
2015, 31(11): 2023-2028
doi: 10.3866/PKU.WHXB201509182
Abstract:
Surface plasmon coupled emission (SPCE) is a physical process opposite to conventional surface plasmon resonance (SPR) with Kretschmann configuration: if a molecule is close enough to the metal surface, the photons generated by excitation of the molecule will be coupled to the SPR mode that is then transformed into the far-field beam propagating at the resonance angle. SPCE serving as a powerful surface-selective analytical technique has been recently used in fluorescence and Raman spectroscopies, and it has several advantages such as repeatable field enhancement, high collection efficiency, and great surface selectivity. In this work, we simplified the simulation of SPCE based on the optical reciprocity theorem. We obtained the radiation patterns of the excited molecule with different orientations, the surface selectivity of SPCE, the wavelength dependence of the radiation angle, and the relationship between the full-width at half-maximum (FWHM) of the radiation angle and the thickness of a silver layer. These simulated results fit almost perfectly with the experimental results reported previously.
Surface plasmon coupled emission (SPCE) is a physical process opposite to conventional surface plasmon resonance (SPR) with Kretschmann configuration: if a molecule is close enough to the metal surface, the photons generated by excitation of the molecule will be coupled to the SPR mode that is then transformed into the far-field beam propagating at the resonance angle. SPCE serving as a powerful surface-selective analytical technique has been recently used in fluorescence and Raman spectroscopies, and it has several advantages such as repeatable field enhancement, high collection efficiency, and great surface selectivity. In this work, we simplified the simulation of SPCE based on the optical reciprocity theorem. We obtained the radiation patterns of the excited molecule with different orientations, the surface selectivity of SPCE, the wavelength dependence of the radiation angle, and the relationship between the full-width at half-maximum (FWHM) of the radiation angle and the thickness of a silver layer. These simulated results fit almost perfectly with the experimental results reported previously.
2015, 31(11): 2029-2035
doi: 10.3866/PKU.WHXB201509231
Abstract:
Organic sulfides are an atmospheric pollutant that photolyze in the atmosphere, causing additional pollution. The S―S bond exists not only in organic sulfides but also in some proteins such as L-cystine, and this bond is crucial to the bioactivity of this protein. In this work, we studied C2H5SSC2H5 photolysis at 266 nm, which is the quadruplicated frequency of the common Nd:YAG laser. The laser-induced fluorescence (LIF) spectra detected the photolyzed products, C2H5S radical. Our results show that the C2H5S radical was mainly created by dissociation of the S―S bond in C2H5SSC2H5. We determined the potential energy curves of the S―S, C―S, and C―C bonds in C2H5SSC2H5 at the B3LYP/6-311++G(d,p) level, finding that photolysis at 266 nm caused the S―S and C―S bonds of C2H5SSC2H5 to dissociate at the ground ???2029-1??? state. Nevertheless, photolysis at 266 nm did not photolyze the C―C bond of C2H5SSC2H5. By optimizing the Cs geometry of the C2H5S radical at the ???2029-1??? state and the ???2029-2??? state, we determined the ???2029-2???-???2029-1??? adiabatic transition energy at the CASSCF/6-311++G(d,p) level, and then studied the LIF spectra of the C2H5S radical. The main pathway is dissociation of the S―S bond of C2H5SSC2H5, though the C―S bond in a few C2H5SSC2H5 molecules did dissociate.
Organic sulfides are an atmospheric pollutant that photolyze in the atmosphere, causing additional pollution. The S―S bond exists not only in organic sulfides but also in some proteins such as L-cystine, and this bond is crucial to the bioactivity of this protein. In this work, we studied C2H5SSC2H5 photolysis at 266 nm, which is the quadruplicated frequency of the common Nd:YAG laser. The laser-induced fluorescence (LIF) spectra detected the photolyzed products, C2H5S radical. Our results show that the C2H5S radical was mainly created by dissociation of the S―S bond in C2H5SSC2H5. We determined the potential energy curves of the S―S, C―S, and C―C bonds in C2H5SSC2H5 at the B3LYP/6-311++G(d,p) level, finding that photolysis at 266 nm caused the S―S and C―S bonds of C2H5SSC2H5 to dissociate at the ground ???2029-1??? state. Nevertheless, photolysis at 266 nm did not photolyze the C―C bond of C2H5SSC2H5. By optimizing the Cs geometry of the C2H5S radical at the ???2029-1??? state and the ???2029-2??? state, we determined the ???2029-2???-???2029-1??? adiabatic transition energy at the CASSCF/6-311++G(d,p) level, and then studied the LIF spectra of the C2H5S radical. The main pathway is dissociation of the S―S bond of C2H5SSC2H5, though the C―S bond in a few C2H5SSC2H5 molecules did dissociate.
2015, 31(11): 2036-2042
doi: 10.3866/PKU.WHXB201509111
Abstract:
We synthesized the alanine-based ionic liquid [C2mim][Ala] (1-ethyl-3-methylimidazolium alanine) by using the neutralization method and characterized it. Using a solution-reaction isoperibol calorimeter, we determined the molar enthalpies of the solution (ΔsolHm) at various molalities in water from (288.15±0.01) to (308.15±0.01) K in intervals of 5 K. Using Archer's method, we obtained the standard molar enthalpy of solution for [C2mim][Ala] (ΔsolHmθ) and calculated its apparent relative molar enthalpy (ΦL). Using Glasser's theory of lattice energy, we obtained the lattice energy, UPOT = 566 kJ·mol-1, the hydration enthalpy of the cation and anion, (ΔH+ + ΔH-) = -620 kJ·mol-1, and the hydration enthalpy of an anion, ΔH-([Ala]-) = -387 kJ·mol-1 at 298.15 K. Finally, we obtained the heat capacity of aqueous [C2mim][Ala] (Cp(sol)) and its apparent molar heat capacity (ΦCp) at various specific molalities.
We synthesized the alanine-based ionic liquid [C2mim][Ala] (1-ethyl-3-methylimidazolium alanine) by using the neutralization method and characterized it. Using a solution-reaction isoperibol calorimeter, we determined the molar enthalpies of the solution (ΔsolHm) at various molalities in water from (288.15±0.01) to (308.15±0.01) K in intervals of 5 K. Using Archer's method, we obtained the standard molar enthalpy of solution for [C2mim][Ala] (ΔsolHmθ) and calculated its apparent relative molar enthalpy (ΦL). Using Glasser's theory of lattice energy, we obtained the lattice energy, UPOT = 566 kJ·mol-1, the hydration enthalpy of the cation and anion, (ΔH+ + ΔH-) = -620 kJ·mol-1, and the hydration enthalpy of an anion, ΔH-([Ala]-) = -387 kJ·mol-1 at 298.15 K. Finally, we obtained the heat capacity of aqueous [C2mim][Ala] (Cp(sol)) and its apparent molar heat capacity (ΦCp) at various specific molalities.
2015, 31(11): 2043-2048
doi: 10.3866/PKU.WHXB201509141
Abstract:
Ferric citrate liposomes (FAC-Lip) and heme liposomes (Heme-Lip) were successfully prepared by a rotary-evaporated film-ultrasonication method. The release of iron liposomes were studied in vitro, and results showed that both iron liposomes had sustained-released properties, with Heme-Lip showing superior sustained-released over FAC-Lip. The liposome/water partition coefficients (P) were determined by equilibrium dialysis and the influences on P were evaluated, as well as the binding Gibbs free energy between FAC (Heme) and liposome. The results show that P initially increased and then decreased with increasing cholesterol content and the ratio of lipid to drug. The hydrogen and electrostatic interactions were largest when P was at its maximum. At the dialysis equilibrium, the binding Gibbs free energies (ΔG) of FAC-Lip and Heme-Lip were -12.7 and -18.2 kJ·mol-1, respectively.
Ferric citrate liposomes (FAC-Lip) and heme liposomes (Heme-Lip) were successfully prepared by a rotary-evaporated film-ultrasonication method. The release of iron liposomes were studied in vitro, and results showed that both iron liposomes had sustained-released properties, with Heme-Lip showing superior sustained-released over FAC-Lip. The liposome/water partition coefficients (P) were determined by equilibrium dialysis and the influences on P were evaluated, as well as the binding Gibbs free energy between FAC (Heme) and liposome. The results show that P initially increased and then decreased with increasing cholesterol content and the ratio of lipid to drug. The hydrogen and electrostatic interactions were largest when P was at its maximum. At the dialysis equilibrium, the binding Gibbs free energies (ΔG) of FAC-Lip and Heme-Lip were -12.7 and -18.2 kJ·mol-1, respectively.
2015, 31(11): 2049-2056
doi: 10.3866/PKU.WHXB201510092
Abstract:
A new cyclic byproduct was formed during hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) preparation by direct nitration. Silicone column chromatography with acetone and dichloromethane in various ratios as the eluent was used to separate 3,5-dinitro-1-oxygen-3,5-diazacyclohexane from the product mixture. A single crystal of 3,5-dinitro-1-oxygen-3,5-diazacyclohexane was grown from acetone, and characterized using elemental analysis, Fourier-transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry (MS). Its structure was determined using an X-ray single-crystal diffractometer. The results indicate that the crystal molecular weight is 178.12. It belongs to the monoclinic system with the space group P121/n1, a = 0.58128(13) nm, b = 1.72389(14) nm, c = 0.71072(6) nm, β = 112.056°, V = 0.66006(16) nm3, Z = 4, DC= 1.792 g·cm-3, μ = 0.17 mm-1, and F(000) = 368.0; the final deviation factor R is 0.0397. Differential scanning calorimetrythermogravimetry (DSC-TG) was used to investigate the thermal behavior of the title compound. Sharp peaks were observed at 383.15 K (melting) and 519.05 K (decomposition). The kinetic parameters were obtained using the Kissinger and Flynn-Wall-Ozawa methods and the TG data at different heating rates. The Coats-Redfern method was used to study the thermal decomposition mechanism of 3,5-dinitro-1-oxygen-3,5-diazacyclohexane. The results show that the title compound is a low-melting-point compound with good stability; its apparent activation energy and pre-exponential factor, calculated using the Kissinger equation, are 212.32 kJ·mol-1 and 6.20×1020 s-1, respectively. The apparent activation energy, calculated using the Flynn-Wall-Ozawa equation, is 210.39 kJ·mol-1. G(α) = (1-α)-1-1 (n = 2) obtained using Coats-Redfern method is regarded as the most appropriate thermal decomposition kinetic equation.
A new cyclic byproduct was formed during hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) preparation by direct nitration. Silicone column chromatography with acetone and dichloromethane in various ratios as the eluent was used to separate 3,5-dinitro-1-oxygen-3,5-diazacyclohexane from the product mixture. A single crystal of 3,5-dinitro-1-oxygen-3,5-diazacyclohexane was grown from acetone, and characterized using elemental analysis, Fourier-transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry (MS). Its structure was determined using an X-ray single-crystal diffractometer. The results indicate that the crystal molecular weight is 178.12. It belongs to the monoclinic system with the space group P121/n1, a = 0.58128(13) nm, b = 1.72389(14) nm, c = 0.71072(6) nm, β = 112.056°, V = 0.66006(16) nm3, Z = 4, DC= 1.792 g·cm-3, μ = 0.17 mm-1, and F(000) = 368.0; the final deviation factor R is 0.0397. Differential scanning calorimetrythermogravimetry (DSC-TG) was used to investigate the thermal behavior of the title compound. Sharp peaks were observed at 383.15 K (melting) and 519.05 K (decomposition). The kinetic parameters were obtained using the Kissinger and Flynn-Wall-Ozawa methods and the TG data at different heating rates. The Coats-Redfern method was used to study the thermal decomposition mechanism of 3,5-dinitro-1-oxygen-3,5-diazacyclohexane. The results show that the title compound is a low-melting-point compound with good stability; its apparent activation energy and pre-exponential factor, calculated using the Kissinger equation, are 212.32 kJ·mol-1 and 6.20×1020 s-1, respectively. The apparent activation energy, calculated using the Flynn-Wall-Ozawa equation, is 210.39 kJ·mol-1. G(α) = (1-α)-1-1 (n = 2) obtained using Coats-Redfern method is regarded as the most appropriate thermal decomposition kinetic equation.
2015, 31(11): 2057-2063
doi: 10.3866/PKU.WHXB201509183
Abstract:
Density functional theory dictates that the electron density determines everything in a molecular system's ground state, including its structure and reactivity properties. However, little is known about how to use density functionals to predict molecular reactivity. Density functional reactivity theory is an effort to fill this gap: it is a theoretical and conceptual framework through which electron-related functionals can be used to accurately predict structure and reactivity. Such density functionals include quantities from the information-theoretic approach, such as Shannon entropy and Fisher information, which have shown great potential as reactivity descriptors. In this work, we introduce three closely related quantities: Rényi entropy, Tsallis entropy, and Onicescu information energy. We evaluated these quantities for a number of neutral atoms and molecules, revealing their scaling properties with respect to electronic energy and the total number of electrons. In addition, using the example of second-order Onicescu information energy, we examined how its patterns change with the angle of dihedral rotation of an ethane molecule at both the molecular level and atoms-in-molecules level. Using these quantities as additional reactivity descriptors, researchers can more accurately predict the structure and reactivity of molecular systems.
Density functional theory dictates that the electron density determines everything in a molecular system's ground state, including its structure and reactivity properties. However, little is known about how to use density functionals to predict molecular reactivity. Density functional reactivity theory is an effort to fill this gap: it is a theoretical and conceptual framework through which electron-related functionals can be used to accurately predict structure and reactivity. Such density functionals include quantities from the information-theoretic approach, such as Shannon entropy and Fisher information, which have shown great potential as reactivity descriptors. In this work, we introduce three closely related quantities: Rényi entropy, Tsallis entropy, and Onicescu information energy. We evaluated these quantities for a number of neutral atoms and molecules, revealing their scaling properties with respect to electronic energy and the total number of electrons. In addition, using the example of second-order Onicescu information energy, we examined how its patterns change with the angle of dihedral rotation of an ethane molecule at both the molecular level and atoms-in-molecules level. Using these quantities as additional reactivity descriptors, researchers can more accurately predict the structure and reactivity of molecular systems.
2015, 31(11): 2064-2076
doi: 10.3866/PKU.WHXB201508201
Abstract:
Electron affinities of F, Cl, OH, SH, CN, CH2, and NH2 have been computed with the second order multireference perturbation theory. The effects of basis set and size of the complete active space on accuracy of electron affinity have also been investigated. The results are compared with calculations performed with CASSCF, CASPT2, CCSD, CCSD(T), B3LYP, X3LYP, M06, HCTH, TPSS, B97D3, mPW2PLYP, and B2PLYP. The overall performance of the second order multireference perturbation theory is best at the level of basis sets used in this study.
Electron affinities of F, Cl, OH, SH, CN, CH2, and NH2 have been computed with the second order multireference perturbation theory. The effects of basis set and size of the complete active space on accuracy of electron affinity have also been investigated. The results are compared with calculations performed with CASSCF, CASPT2, CCSD, CCSD(T), B3LYP, X3LYP, M06, HCTH, TPSS, B97D3, mPW2PLYP, and B2PLYP. The overall performance of the second order multireference perturbation theory is best at the level of basis sets used in this study.
2015, 31(11): 2077-2082
doi: 10.3866/PKU.WHXB201509143
Abstract:
The potential energy surface plays an important role in studying molecular reaction dynamics. In this work, a new method, namely the “multi-center partition” method, is proposed to construct the potential energy surface of H3. The optimized function is first determined by comparing the London-Eyring-Polanyi-Sato (LEPS) potential, the many-body expansion potential, and the permutation-invariant polynomial potential. This comparison shows that the permutation-invariant polynomial fitting proposed by Bowman is the most efficient method for describing the topology of the H3 system. The quasi-classical trajectory method is used to analyze the rationality of those potential energy surfaces. By combining the multi-center partition method with the permutation-invariant polynomial method, the accuracy of the H3 molecular potential energy surface is greatly improved and could possibly be used in the fitting of potential energy surfaces in other systems.
The potential energy surface plays an important role in studying molecular reaction dynamics. In this work, a new method, namely the “multi-center partition” method, is proposed to construct the potential energy surface of H3. The optimized function is first determined by comparing the London-Eyring-Polanyi-Sato (LEPS) potential, the many-body expansion potential, and the permutation-invariant polynomial potential. This comparison shows that the permutation-invariant polynomial fitting proposed by Bowman is the most efficient method for describing the topology of the H3 system. The quasi-classical trajectory method is used to analyze the rationality of those potential energy surfaces. By combining the multi-center partition method with the permutation-invariant polynomial method, the accuracy of the H3 molecular potential energy surface is greatly improved and could possibly be used in the fitting of potential energy surfaces in other systems.
2015, 31(11): 2083-2090
doi: 10.3866/PKU.WHXB201510132
Abstract:
We investigated the electronic properties of armchair MoS2 nanoribbons with vacancy defects using a first-principles method based on density functional theory. It was found that defects reduced the stability of armchair MoS2 nanoribbons. Mo vacancies and MoS2 triple vacancies can both change the band structures of nanoribbons from semiconductor to metallic, whereas S vacancies, 2S divacancies, and MoS divacancies only decrease the bandgap. The densities of states and eigenstates of the nanoribbons indicated that impurity bands near the Fermi level basically contributed to the defect states. The relationships between the bandgap and width of four types of semiconducting nanoribbons were simulated. Nanoribbons with no defects have a bandgap that oscillates with width in a period of three, but the bandgap changes nonperiodically for nanoribbons with S vacancies, 2S divacancies, and MoS divacancies. We also found that when the concentration of defects decreased, the vacancy defects did not destroy the nanoribbon semiconducting behavior but only decreased the bandgap. These results open up possibilities for MoS2 nanoribbon applications in novel nanoelectronic devices.
We investigated the electronic properties of armchair MoS2 nanoribbons with vacancy defects using a first-principles method based on density functional theory. It was found that defects reduced the stability of armchair MoS2 nanoribbons. Mo vacancies and MoS2 triple vacancies can both change the band structures of nanoribbons from semiconductor to metallic, whereas S vacancies, 2S divacancies, and MoS divacancies only decrease the bandgap. The densities of states and eigenstates of the nanoribbons indicated that impurity bands near the Fermi level basically contributed to the defect states. The relationships between the bandgap and width of four types of semiconducting nanoribbons were simulated. Nanoribbons with no defects have a bandgap that oscillates with width in a period of three, but the bandgap changes nonperiodically for nanoribbons with S vacancies, 2S divacancies, and MoS divacancies. We also found that when the concentration of defects decreased, the vacancy defects did not destroy the nanoribbon semiconducting behavior but only decreased the bandgap. These results open up possibilities for MoS2 nanoribbon applications in novel nanoelectronic devices.
2015, 31(11): 2091-2098
doi: 10.3866/PKU.WHXB201509153
Abstract:
Using molecular dynamics simulations, we investigated the microscopic processes of large palladium clusters deposited on Pd/Ag substrates at different incident velocities at the room temperature. We studied the impact process by analyzing the deposited morphology, embedded depth, diffusion degree of the cluster atoms, temperature variation in the collision region on the substrate, and energy conversion between the cluster and substrate. This analysis yielded the change rules of the deposited morphology, structural characteristics, and energy conversion for various cluster sizes, incident velocities, and substrates. Furthermore, we explored the deformation morphology of the first deposited cluster and the temperature of the collision contact region for various impact times of the second cluster. Shortening the impact time of the second cluster caused the clusters and substrate to better combine.
Using molecular dynamics simulations, we investigated the microscopic processes of large palladium clusters deposited on Pd/Ag substrates at different incident velocities at the room temperature. We studied the impact process by analyzing the deposited morphology, embedded depth, diffusion degree of the cluster atoms, temperature variation in the collision region on the substrate, and energy conversion between the cluster and substrate. This analysis yielded the change rules of the deposited morphology, structural characteristics, and energy conversion for various cluster sizes, incident velocities, and substrates. Furthermore, we explored the deformation morphology of the first deposited cluster and the temperature of the collision contact region for various impact times of the second cluster. Shortening the impact time of the second cluster caused the clusters and substrate to better combine.
2015, 31(11): 2099-2108
doi: 10.3866/PKU.WHXB201510081
Abstract:
Cross-linked porous carbon nanofiber networks were successfully prepared by electrospinning followed by preoxidation and carbonization using low-cost melamine and polyacrylonitrile (PAN) as precursors. The structures and morphologies of the nanofiber networks were investigated using Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and N2 adsorption/desorption. The carbon fibers had an interconnected nanofibrous morphology with a well-developed porous structure including micropores, mesopores and macropores, high-level nitrogen doping (up to 14.3%), and a small average diameter (about 89 nm). Without activation, the carbon nanofibers had a high specific capacitance of 194 F·g-1 at a current density of 0.05 A·g-1. Cycling experiments showed that the specific capacitance retained approximately 99.2% of the initial capacitance after 1000 cycles at a current density of 2 A·g-1, indicating an excellent electrochemical performance.
Cross-linked porous carbon nanofiber networks were successfully prepared by electrospinning followed by preoxidation and carbonization using low-cost melamine and polyacrylonitrile (PAN) as precursors. The structures and morphologies of the nanofiber networks were investigated using Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and N2 adsorption/desorption. The carbon fibers had an interconnected nanofibrous morphology with a well-developed porous structure including micropores, mesopores and macropores, high-level nitrogen doping (up to 14.3%), and a small average diameter (about 89 nm). Without activation, the carbon nanofibers had a high specific capacitance of 194 F·g-1 at a current density of 0.05 A·g-1. Cycling experiments showed that the specific capacitance retained approximately 99.2% of the initial capacitance after 1000 cycles at a current density of 2 A·g-1, indicating an excellent electrochemical performance.
2015, 31(11): 2109-2116
doi: 10.3866/PKU.WHXB201509151
Abstract:
We fabricated highly ordered ZnO nanosheet arrays on ITO substrates by adding KCl and ethylenediamine(EDA) through potentiostatic deposition, then produced a hierarchical structure of ZnO nanorods on the nanosheets by using secondary electrodeposition. Shell-core Sb2S3/ZnO nanostructures were prepared from ZnO nanosheets and ZnO nanorods on nanosheets by chemical bath deposition. The nanostructures were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and their photoelectrochemical properties were investigated using ultraviolet-visible spectroscopy (UV-Vis) and photocurrent measurements. The shell-core Sb2S3/ZnO based on the hierarchical micronanostructure had higher photocurrent than did the shell-core Sb2S3/ZnO nanosheets. A hybrid solar cell was fabricated with a P3HT/Sb2S3/ZnO film as the photoactive layer. The P3HT/Sb2S3/ZnO hierarchical electrode exhibited an energy conversion efficiency as high as 0.81%.
We fabricated highly ordered ZnO nanosheet arrays on ITO substrates by adding KCl and ethylenediamine(EDA) through potentiostatic deposition, then produced a hierarchical structure of ZnO nanorods on the nanosheets by using secondary electrodeposition. Shell-core Sb2S3/ZnO nanostructures were prepared from ZnO nanosheets and ZnO nanorods on nanosheets by chemical bath deposition. The nanostructures were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and their photoelectrochemical properties were investigated using ultraviolet-visible spectroscopy (UV-Vis) and photocurrent measurements. The shell-core Sb2S3/ZnO based on the hierarchical micronanostructure had higher photocurrent than did the shell-core Sb2S3/ZnO nanosheets. A hybrid solar cell was fabricated with a P3HT/Sb2S3/ZnO film as the photoactive layer. The P3HT/Sb2S3/ZnO hierarchical electrode exhibited an energy conversion efficiency as high as 0.81%.
2015, 31(11): 2117-2123
doi: 10.3866/PKU.WHXB201509181
Abstract:
In this study, graphite oxide was prepared from natural graphite powder using a modified Hummers method. Well-dispersed Pt nanoparticles were synthesized on reduced graphene oxide (RGO) via a simple one-step chemical reduction method in ethylene glycol (EG) by simultaneous reduction of graphene oxide (GO) and chloroplatinic acid. The microstructure, composition, and morphology of the synthesized materials were characterized with Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). It is shown that the GO was reduced to RGO, and the Pt nanoparticles with an average particle size of 2.3 nm were well dispersed on the surface of RGO. The catalytic performance of the catalysts for methanol oxidation was investigated by cyclic voltammetry and amperometric method, which indicated that Pt/RGO catalyst had higher electrocatalytic activity and stability for the oxidation of methanol than the Pt/C and Pt/CNT catalysts. The If/Ib of Pt/RGO reached 1.3, which was 2.2 and 1.9 times as high as those of Pt/C and Pt/CNT catalysts, respectively, revealing that Pt/RGO had high poisoning tolerance to the COad intermediate species produced in the methanol oxidation reaction.
In this study, graphite oxide was prepared from natural graphite powder using a modified Hummers method. Well-dispersed Pt nanoparticles were synthesized on reduced graphene oxide (RGO) via a simple one-step chemical reduction method in ethylene glycol (EG) by simultaneous reduction of graphene oxide (GO) and chloroplatinic acid. The microstructure, composition, and morphology of the synthesized materials were characterized with Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). It is shown that the GO was reduced to RGO, and the Pt nanoparticles with an average particle size of 2.3 nm were well dispersed on the surface of RGO. The catalytic performance of the catalysts for methanol oxidation was investigated by cyclic voltammetry and amperometric method, which indicated that Pt/RGO catalyst had higher electrocatalytic activity and stability for the oxidation of methanol than the Pt/C and Pt/CNT catalysts. The If/Ib of Pt/RGO reached 1.3, which was 2.2 and 1.9 times as high as those of Pt/C and Pt/CNT catalysts, respectively, revealing that Pt/RGO had high poisoning tolerance to the COad intermediate species produced in the methanol oxidation reaction.
2015, 31(11): 2124-2130
doi: 10.3866/PKU.WHXB201509112
Abstract:
Using rheological measurements, we investigated the wormlike micelles formed by anionic surfactants, sodium oleate (NaOA), and sodium erucate (NaOEr) in the presence of KCl and tetrabutyl ammonium bromide (TBAB). The viscosity of the NaOA solution increased with KCl concentration, but adding TBAB decreased viscosity. In contrast, the apparent viscosity of NaOEr-KCl solution enhances with increasing TBAB concentration. In addition, NaOEr is better than NaOA at encouraging the construction of viscoelastic wormlike micelles, needing less surfactant and a lower salt concentration. We prepared a wormlike micelle system with strong viscoelasticity by using NaOEr, cooperatively induced by KCl and TBAB. Based on these studies, we discussed the complex influence of TBA+ on constructing wormlike micelles.
Using rheological measurements, we investigated the wormlike micelles formed by anionic surfactants, sodium oleate (NaOA), and sodium erucate (NaOEr) in the presence of KCl and tetrabutyl ammonium bromide (TBAB). The viscosity of the NaOA solution increased with KCl concentration, but adding TBAB decreased viscosity. In contrast, the apparent viscosity of NaOEr-KCl solution enhances with increasing TBAB concentration. In addition, NaOEr is better than NaOA at encouraging the construction of viscoelastic wormlike micelles, needing less surfactant and a lower salt concentration. We prepared a wormlike micelle system with strong viscoelasticity by using NaOEr, cooperatively induced by KCl and TBAB. Based on these studies, we discussed the complex influence of TBA+ on constructing wormlike micelles.
Preparation and Application of Pt-Ni Catalysts Supported on Cobalt-Polypyrrole-Carbon for Fuel Cells
2015, 31(11): 2131-2138
doi: 10.3866/PKU.WHXB201509171
Abstract:
By using pulse-microwave assisted chemical reduction, we prepared a Pt-Ni alloy supported on a cobalt-polypyrrole-carbon (Co-PPy-C) catalyst. The catalyst microstructure and morphology were characterized by using transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrocatalytic performance and durability of the catalysts were measured with cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The metal particles were well dispersed on the carbon support, and the particle size of PtNi/Co-PPy-C was about 1.77 nm. XRD showed that the Pt(111) diffraction peak was strongest, so the most of the Pt in the catalysts was in a face-centered cubic lattice. The electrochemical surface area (ECSA) of PtNi/Co-PPy-C (72.5 m2·g-1) was higher than that of Pt/C(JM) (56.9 m2·g-1). After an accelerated durability test for 5000 cycles, the particle size of PtNi/Co-PPy-C obviously increased. The degradation rate of ECSA and the mass activity (MA) of PtNi/Co-PPY-C were 38.2% and 63.9%, respectively. We applied the PtNi/Co-PPy-C catalyst after optimizing the membrane electrode assembly (MEA) with an area of 50 cm2. The fuel cell could be suitably operated at 70 ℃ with a back pressure of 50 kPa. At these conditions, the maximum power density of MEA by PtNi/Co-PPy-C was 523 mW·cm-2. The excellent performance of PtNi/Co-PPy-C makes it a promising catalyst for proton exchange membrane fuel cells (PEMFCs).
By using pulse-microwave assisted chemical reduction, we prepared a Pt-Ni alloy supported on a cobalt-polypyrrole-carbon (Co-PPy-C) catalyst. The catalyst microstructure and morphology were characterized by using transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrocatalytic performance and durability of the catalysts were measured with cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The metal particles were well dispersed on the carbon support, and the particle size of PtNi/Co-PPy-C was about 1.77 nm. XRD showed that the Pt(111) diffraction peak was strongest, so the most of the Pt in the catalysts was in a face-centered cubic lattice. The electrochemical surface area (ECSA) of PtNi/Co-PPy-C (72.5 m2·g-1) was higher than that of Pt/C(JM) (56.9 m2·g-1). After an accelerated durability test for 5000 cycles, the particle size of PtNi/Co-PPy-C obviously increased. The degradation rate of ECSA and the mass activity (MA) of PtNi/Co-PPY-C were 38.2% and 63.9%, respectively. We applied the PtNi/Co-PPy-C catalyst after optimizing the membrane electrode assembly (MEA) with an area of 50 cm2. The fuel cell could be suitably operated at 70 ℃ with a back pressure of 50 kPa. At these conditions, the maximum power density of MEA by PtNi/Co-PPy-C was 523 mW·cm-2. The excellent performance of PtNi/Co-PPy-C makes it a promising catalyst for proton exchange membrane fuel cells (PEMFCs).
2015, 31(11): 2139-2150
doi: 10.3866/PKU.WHXB201509281
Abstract:
ZSM-5 zeolites with different pore structures were synthesized using different templates (tetrapropyl ammonium hydroxide (TPAOH), cetyltrimethylammonium bromide (CTAB) and C18-6-6Br2). The obtained nanosized (NZ), mesoporous (MZ), and nanosheets (NSZ) ZSM-5 samples were compared with conventional microporous ZSM-5 zeolite (CZ). The physicochemical properties of these samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption-desorption, and temperature-programmed desorption of ammonia (NH3-TPD). The results showed that the mesopore volumes and surface areas of the four samples increased in the order NSZ > MZ > NZ > CZ, and the ratio of strong/weak acidity increased in the order CZ > MZ > NZ > NSZ. In the methanol to propylene (MTP) reaction, the catalyst porosity played an important role on the product selectivity and catalytic stability. The selectivities for propylene and total olefins improved with increasing mesoporosity; NSZ, with the largest mesopore volume, gave the highest propylene selectivity, i.e., 47.5%, and 78.4% total olefins. Meanwhile, the introduction of mesopores into the ZSM-5 zeolite extended the catalytic lifetime. The NZ sample displayed reliable MTP catalytic activity for 200 h, which was predominately attributed to its optimal combination of acidity and porosity.
ZSM-5 zeolites with different pore structures were synthesized using different templates (tetrapropyl ammonium hydroxide (TPAOH), cetyltrimethylammonium bromide (CTAB) and C18-6-6Br2). The obtained nanosized (NZ), mesoporous (MZ), and nanosheets (NSZ) ZSM-5 samples were compared with conventional microporous ZSM-5 zeolite (CZ). The physicochemical properties of these samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption-desorption, and temperature-programmed desorption of ammonia (NH3-TPD). The results showed that the mesopore volumes and surface areas of the four samples increased in the order NSZ > MZ > NZ > CZ, and the ratio of strong/weak acidity increased in the order CZ > MZ > NZ > NSZ. In the methanol to propylene (MTP) reaction, the catalyst porosity played an important role on the product selectivity and catalytic stability. The selectivities for propylene and total olefins improved with increasing mesoporosity; NSZ, with the largest mesopore volume, gave the highest propylene selectivity, i.e., 47.5%, and 78.4% total olefins. Meanwhile, the introduction of mesopores into the ZSM-5 zeolite extended the catalytic lifetime. The NZ sample displayed reliable MTP catalytic activity for 200 h, which was predominately attributed to its optimal combination of acidity and porosity.
2015, 31(11): 2151-2157
doi: 10.3866/PKU.WHXB201510083
Abstract:
The growth mode, electronic structure, and thermal stability of Ni nanoparticles on thin ZrO2(111) film surfaces were investigated using X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and low-energy electron diffraction. Stoichiometric ZrO2(111) thin films with thickness of 3 nm were epitaxially grown on a Pt(111) single-crystal surface. The results indicate that the growth of Ni vapor deposited on thin ZrO2(111) films follows two-dimensional growth up to 0.5 ML (monolayer), followed by threedimensional growth (i.e., the Stranski-Krastanov growth mode). The Ni 2p3/2 binding energy (BE) increases with decreasing Ni coverage. We used the Auger parameter method to differentiate the contributions to this BE shift from the initial-state and final-state effects. The main contribution to the Ni 2p core level BE shift is made by the final-state effect. However, at low Ni coverages, the initial-state effect also contributes. This suggests that at the initial stage of Ni growth on the ZrO2(111) surface, Ni and ZrO2 interact strongly, leading to charge transfer from Ni to the ZrO2 substrate, with the appearance of partially positively charged Niδ+. Thermal stability studies of Ni/ZrO2(111) model catalysts with two different coverages (0.05 and 0.5 ML) indicate further oxidation of Ni to Ni2+ and concurrent diffusion of Ni into the ZrO2 substrate at elevated temperatures. These findings provide an atomic-level fundamental understanding of the interactions between Ni with ZrO2, which is essential for identifying the structures of real ZrO2-supported Ni catalysts.
The growth mode, electronic structure, and thermal stability of Ni nanoparticles on thin ZrO2(111) film surfaces were investigated using X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and low-energy electron diffraction. Stoichiometric ZrO2(111) thin films with thickness of 3 nm were epitaxially grown on a Pt(111) single-crystal surface. The results indicate that the growth of Ni vapor deposited on thin ZrO2(111) films follows two-dimensional growth up to 0.5 ML (monolayer), followed by threedimensional growth (i.e., the Stranski-Krastanov growth mode). The Ni 2p3/2 binding energy (BE) increases with decreasing Ni coverage. We used the Auger parameter method to differentiate the contributions to this BE shift from the initial-state and final-state effects. The main contribution to the Ni 2p core level BE shift is made by the final-state effect. However, at low Ni coverages, the initial-state effect also contributes. This suggests that at the initial stage of Ni growth on the ZrO2(111) surface, Ni and ZrO2 interact strongly, leading to charge transfer from Ni to the ZrO2 substrate, with the appearance of partially positively charged Niδ+. Thermal stability studies of Ni/ZrO2(111) model catalysts with two different coverages (0.05 and 0.5 ML) indicate further oxidation of Ni to Ni2+ and concurrent diffusion of Ni into the ZrO2 substrate at elevated temperatures. These findings provide an atomic-level fundamental understanding of the interactions between Ni with ZrO2, which is essential for identifying the structures of real ZrO2-supported Ni catalysts.
2015, 31(11): 2158-2164
doi: 10.3866/PKU.WHXB201510091
Abstract:
CeO2 promoted CuCl/activated carbon (AC) adsorbents were prepared using an incipient wetness impregnation method, and characterized using N2 adsorption/desorption isotherms, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The Cu(II) on the AC surface was reduced to Cu(I) when calcination was performed in a nitrogen flow. The effects of Ce on the C2H4/C2H6 adsorptive separation performance were investigated. The adsorption isotherms showed that the addition of CeO2 improved the separation performance by decreasing the C2H6 adsorption capacity compared with that of the nonpromoted sample. The XRD and XPS results indicated that the active crystal particles on the AC surface became smaller, leading to higher dispersion and a higher degree of Cu(II) reduction. The best adsorption selectivity was obtained using the 5Ce50Cu [CeO2 and CuCl2 mass fractions (w) 5% and 50%, respectively] sample, i.e., with CeO2 in the adsorbent; the adsorption selectivity increased from 4.2 to 8.7 at 660 kPa compared with that of the 50Cu sample.
CeO2 promoted CuCl/activated carbon (AC) adsorbents were prepared using an incipient wetness impregnation method, and characterized using N2 adsorption/desorption isotherms, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The Cu(II) on the AC surface was reduced to Cu(I) when calcination was performed in a nitrogen flow. The effects of Ce on the C2H4/C2H6 adsorptive separation performance were investigated. The adsorption isotherms showed that the addition of CeO2 improved the separation performance by decreasing the C2H6 adsorption capacity compared with that of the nonpromoted sample. The XRD and XPS results indicated that the active crystal particles on the AC surface became smaller, leading to higher dispersion and a higher degree of Cu(II) reduction. The best adsorption selectivity was obtained using the 5Ce50Cu [CeO2 and CuCl2 mass fractions (w) 5% and 50%, respectively] sample, i.e., with CeO2 in the adsorbent; the adsorption selectivity increased from 4.2 to 8.7 at 660 kPa compared with that of the 50Cu sample.
2015, 31(11): 2165-2173
doi: 10.3866/PKU.WHXB201509184
Abstract:
Cu-SSZ-13 catalysts had been prepared by using a microwave irradiation (MW) method and a conventional hydrothermal (CH) method, which were applied to removal of NOx from diesel vehicles by NH3. The physical and chemical properties of the samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, H2 temperature-programmed reduction (H2-TPR), electron paramagnetic resonance (EPR), NH3 temperature-programmed desorption (NH3-TPD), inductively coupled plasma-mass spectroscopy (ICP-MS), and X-ray photoelectron spectroscopy (XPS). The MW had some significant advantages, greatly shortening the crystallization time of SSZ-13 and improving its physical and chemical properties. The sample synthesized using MW with a crystallization time of 9 h had similar crystallinity to that synthesized by the CH with a crystallization time of 72 h. The sample synthesized by the MW had improved pore structure and amounts of Lewis (L) acid and Brönsted (B) acid. The great increase in Cu load as an active component indicated that the MW enhanced the ability of SSZ-13 to perform Cu exchange. The Cu-SSZ-13 synthesized by MW had improved low-temperature activity and anti-aging ability.
Cu-SSZ-13 catalysts had been prepared by using a microwave irradiation (MW) method and a conventional hydrothermal (CH) method, which were applied to removal of NOx from diesel vehicles by NH3. The physical and chemical properties of the samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, H2 temperature-programmed reduction (H2-TPR), electron paramagnetic resonance (EPR), NH3 temperature-programmed desorption (NH3-TPD), inductively coupled plasma-mass spectroscopy (ICP-MS), and X-ray photoelectron spectroscopy (XPS). The MW had some significant advantages, greatly shortening the crystallization time of SSZ-13 and improving its physical and chemical properties. The sample synthesized using MW with a crystallization time of 9 h had similar crystallinity to that synthesized by the CH with a crystallization time of 72 h. The sample synthesized by the MW had improved pore structure and amounts of Lewis (L) acid and Brönsted (B) acid. The great increase in Cu load as an active component indicated that the MW enhanced the ability of SSZ-13 to perform Cu exchange. The Cu-SSZ-13 synthesized by MW had improved low-temperature activity and anti-aging ability.
2015, 31(11): 2174-2182
doi: 10.3866/PKU.WHXB201510084
Abstract:
A series of luminescent cyclometalated Ir(III) complexes functionalized with amide derivatives were prepared and compared with [Ir(ppy)2phen-NH2]Cl. The complexes were [Ir(ppy)2phen-Br]Cl, [Ir(ppy)2phen-COOH]Cl, and [Ir(ppy)2phen-Si]Cl, where ppy is 2-phenylpyridine, phen-NH2 is 5-amino-[1,10]-phenanthroline, phen-Br is 2-bromo-2-methyl-N-(1,10-phenanthrolin-5-yl)propanamide, phen-COOH is 4-[(1,10-phenanthrolin-5-yl)amino]-4-oxobut-2-enoic acid, and phen-Si is 5-[N,N-bis-3-(triethoxysilyl) propyl]ureyl-1,10-phenanthroline. They were characterized using nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS), ultraviolet-visible (UV-Vis) absorption spectroscopy, photoluminescence (PL) spectroscopy, and cyclic voltammetry (CV). The three novel complexes have intense absorptions in the blue-purple region. The complexes show bright yellow to orange PL emissions under UV irradiation, and the quantum yields (Φ) of these complexes are higher than 12%. The excited-state lifetimes of the novel complexes are 9.18-12.00 μs, much longer than that of [Ir(ppy)2phen-NH2]Cl (5.78 μs). With both the highest quantum yield (32%) and longest lifetime (12.00 μs), [Ir(ppy)2phen-Br]Cl also shows the best oxygen-sensing properties and the largest I0/I factor, 10.91 (I0: the PL intensity of the complex in the absence of O2, I: the PL intensity of the complex under pure oxygen). These results suggest that [Ir(ppy)2phen-Br]Cl may be a promising candidate for use in oxygen sensors based on covalent grafting. Time-dependent density functional theory (TD-DFT) calculations were used to supplement the photoelectric property studies. Theoretical calculations indicate that all the mononuclear complexes have approximately octahedral structures with Ir(III) as the coordination center. The computational results agree well with the experimental data.
A series of luminescent cyclometalated Ir(III) complexes functionalized with amide derivatives were prepared and compared with [Ir(ppy)2phen-NH2]Cl. The complexes were [Ir(ppy)2phen-Br]Cl, [Ir(ppy)2phen-COOH]Cl, and [Ir(ppy)2phen-Si]Cl, where ppy is 2-phenylpyridine, phen-NH2 is 5-amino-[1,10]-phenanthroline, phen-Br is 2-bromo-2-methyl-N-(1,10-phenanthrolin-5-yl)propanamide, phen-COOH is 4-[(1,10-phenanthrolin-5-yl)amino]-4-oxobut-2-enoic acid, and phen-Si is 5-[N,N-bis-3-(triethoxysilyl) propyl]ureyl-1,10-phenanthroline. They were characterized using nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS), ultraviolet-visible (UV-Vis) absorption spectroscopy, photoluminescence (PL) spectroscopy, and cyclic voltammetry (CV). The three novel complexes have intense absorptions in the blue-purple region. The complexes show bright yellow to orange PL emissions under UV irradiation, and the quantum yields (Φ) of these complexes are higher than 12%. The excited-state lifetimes of the novel complexes are 9.18-12.00 μs, much longer than that of [Ir(ppy)2phen-NH2]Cl (5.78 μs). With both the highest quantum yield (32%) and longest lifetime (12.00 μs), [Ir(ppy)2phen-Br]Cl also shows the best oxygen-sensing properties and the largest I0/I factor, 10.91 (I0: the PL intensity of the complex in the absence of O2, I: the PL intensity of the complex under pure oxygen). These results suggest that [Ir(ppy)2phen-Br]Cl may be a promising candidate for use in oxygen sensors based on covalent grafting. Time-dependent density functional theory (TD-DFT) calculations were used to supplement the photoelectric property studies. Theoretical calculations indicate that all the mononuclear complexes have approximately octahedral structures with Ir(III) as the coordination center. The computational results agree well with the experimental data.
2015, 31(11): 2183-2190
doi: 10.3866/PKU.WHXB201509142
Abstract:
We synthesized Tm3+-doped NaYF4 microcrystals with various length-to-diameter ratios by using a facile hydrothermal method assisted with sodium citrate from precursor solutions with various pH values. The β-NaYF4:Tm3+ samples were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared (FT-IR) spectroscopy, and photoluminescence spectroscopy. XRD and SEM show that as the pH of the precursor solutions increased, the morphology of the microcrystals changed from long rods to short microprisms to microplates. We also investigated the luminescence properties of the β-NaYF4:Tm3+ hexagonal microdisks and microrods. By selectively exciting the NaYF4:Tm3+ microcrystals with a 656-nm pulsed laser at a pulse duration of 10 ns, they exhibited a strong single-band down-conversion emission at 800 nm. We systematically studied how the excitation wavelength, temperature, and length-to-diameter ratio of the particles affected the luminescence intensity of their near-infrared (NIR) single-band emission. As the length-to-diameter ratio of the NaYF4:Tm3+ microcrystals increased, their luminescence intensity strengthened. Exploring the reason for this luminescence enhancement, we propose a mechanism based on vacancy defects.
We synthesized Tm3+-doped NaYF4 microcrystals with various length-to-diameter ratios by using a facile hydrothermal method assisted with sodium citrate from precursor solutions with various pH values. The β-NaYF4:Tm3+ samples were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared (FT-IR) spectroscopy, and photoluminescence spectroscopy. XRD and SEM show that as the pH of the precursor solutions increased, the morphology of the microcrystals changed from long rods to short microprisms to microplates. We also investigated the luminescence properties of the β-NaYF4:Tm3+ hexagonal microdisks and microrods. By selectively exciting the NaYF4:Tm3+ microcrystals with a 656-nm pulsed laser at a pulse duration of 10 ns, they exhibited a strong single-band down-conversion emission at 800 nm. We systematically studied how the excitation wavelength, temperature, and length-to-diameter ratio of the particles affected the luminescence intensity of their near-infrared (NIR) single-band emission. As the length-to-diameter ratio of the NaYF4:Tm3+ microcrystals increased, their luminescence intensity strengthened. Exploring the reason for this luminescence enhancement, we propose a mechanism based on vacancy defects.
2015, 31(11): 2191-2206
doi: 10.3866/PKU.WHXB201510134
Abstract:
B-Raf kinase plays an important role in the mitogen-activated protein kinase (MAPK) signaling transmission pathway and has been identified as an attractive target for cancer therapy. The exploitation of novel and efficient B-Raf inhibitors has become a hot research topic. In this study, we investigated quantitative structure-activity relationship (QSAR) to probe the origins of the inhibitory activities of B-Raf Type II inhibitors. We used structurally diverse B-Raf Type II inhibitors and an integrated docking and QSAR extended method. We focused mainly on two themes: bioactive conformations and descriptors. First, various molecular docking methods (Glide, Gold, LigandFit, Cdocker, and Libdock) were evaluated, and then all molecules were docked into the B-Raf active site to obtain the bioactive conformations. Secondly, based on the docking results, 16 scoring functions and 21 docking-generated energy-based descriptors were calculated to construct regression models. The results gave highly accurate fitting and had strong predictive abilities (M1: r2 = 0.852, r(CV)2 = 0.790, rpre2 = 0.864; M2: r2 = 0.738, r(CV)2 = 0.812, rpre2 = 0.8605). The important descriptors were also explored to elucidate the main factors influencing the inhibition activities. The models suggested that the scoring functions (G_Score, -ECD, Dock_Score, and PMF) and docking-generated energy-based descriptors (S(hb_ext), DE(int), and Emodel) were significant. Some new compounds that are potential B-Raf inhibitors were obtained through virtual screening and theoretical predictions using the established models. Such information is useful in guiding the design of novel and robust B-Raf Type II inhibitors.
B-Raf kinase plays an important role in the mitogen-activated protein kinase (MAPK) signaling transmission pathway and has been identified as an attractive target for cancer therapy. The exploitation of novel and efficient B-Raf inhibitors has become a hot research topic. In this study, we investigated quantitative structure-activity relationship (QSAR) to probe the origins of the inhibitory activities of B-Raf Type II inhibitors. We used structurally diverse B-Raf Type II inhibitors and an integrated docking and QSAR extended method. We focused mainly on two themes: bioactive conformations and descriptors. First, various molecular docking methods (Glide, Gold, LigandFit, Cdocker, and Libdock) were evaluated, and then all molecules were docked into the B-Raf active site to obtain the bioactive conformations. Secondly, based on the docking results, 16 scoring functions and 21 docking-generated energy-based descriptors were calculated to construct regression models. The results gave highly accurate fitting and had strong predictive abilities (M1: r2 = 0.852, r(CV)2 = 0.790, rpre2 = 0.864; M2: r2 = 0.738, r(CV)2 = 0.812, rpre2 = 0.8605). The important descriptors were also explored to elucidate the main factors influencing the inhibition activities. The models suggested that the scoring functions (G_Score, -ECD, Dock_Score, and PMF) and docking-generated energy-based descriptors (S(hb_ext), DE(int), and Emodel) were significant. Some new compounds that are potential B-Raf inhibitors were obtained through virtual screening and theoretical predictions using the established models. Such information is useful in guiding the design of novel and robust B-Raf Type II inhibitors.
2015, 31(11): 2207-2212
doi: 10.3866/PKU.WHXB201509152
Abstract:
We establish a model for growing titania nanowires arrays (TNAs) within micelles on the hydrophilic substrate of fluorine-doped tin oxide (FTO) in a reversed micelle reaction under hydrothermal conditions, and we discuss the mechanism that micelle size controlled the diameter in the TNAs growth progress. We produced TNAs with various diameters on FTO by adjusting the temperature, which changed the micelle size, and by using the crystal-plane suppressing effect of the Cl- ion. The volume ratio of the polar/nonpolar solvent barely influenced the nanowire diameter during growth. Based on this result, thinner TNAs can be prepared by using the restricting effect of the micelles and the crystal-plane suppressing effect of the Cl- ion. This method can also be used to synthesize other relative oxide nanomaterials.
We establish a model for growing titania nanowires arrays (TNAs) within micelles on the hydrophilic substrate of fluorine-doped tin oxide (FTO) in a reversed micelle reaction under hydrothermal conditions, and we discuss the mechanism that micelle size controlled the diameter in the TNAs growth progress. We produced TNAs with various diameters on FTO by adjusting the temperature, which changed the micelle size, and by using the crystal-plane suppressing effect of the Cl- ion. The volume ratio of the polar/nonpolar solvent barely influenced the nanowire diameter during growth. Based on this result, thinner TNAs can be prepared by using the restricting effect of the micelles and the crystal-plane suppressing effect of the Cl- ion. This method can also be used to synthesize other relative oxide nanomaterials.
2015, 31(11): 2213-2219
doi: 10.3866/PKU.WHXB201509301
Abstract:
A two-step method for growing vertical zinc oxide nanorod arrays on indium tin oxide (ITO)-coated glass substrates is proposed. First, a zinc oxide seed layer was formed on the ITO substrate by simple dipcoating combined with the Czochralski method, and then vertical zinc oxide nanorod arrays were obtained by a hydrothermal method. The nanorod arrays were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energydispersive X-ray spectroscopy (EDS). The effects of the precursor concentration, sol-aging time, hydrothermal reaction time, and cycle times of the dip-coating and hydrothermal reaction on the structure and surface morphology of the zinc oxide nanorod arrays were investigated. The results show that the length and diameter of zinc oxide nanorod arrays increased with the increasing precursor concentrations, sol-aging time, and hydrothermal reaction time. Good vertical zinc oxide nanorod arrays were obtained under the optional growth conditions, i.e., three hydrothermal reactions for 150 min, three rounds of dip-coating, 0.5 mol·L-1 precursor solution concentration, and 24 h aging.
A two-step method for growing vertical zinc oxide nanorod arrays on indium tin oxide (ITO)-coated glass substrates is proposed. First, a zinc oxide seed layer was formed on the ITO substrate by simple dipcoating combined with the Czochralski method, and then vertical zinc oxide nanorod arrays were obtained by a hydrothermal method. The nanorod arrays were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energydispersive X-ray spectroscopy (EDS). The effects of the precursor concentration, sol-aging time, hydrothermal reaction time, and cycle times of the dip-coating and hydrothermal reaction on the structure and surface morphology of the zinc oxide nanorod arrays were investigated. The results show that the length and diameter of zinc oxide nanorod arrays increased with the increasing precursor concentrations, sol-aging time, and hydrothermal reaction time. Good vertical zinc oxide nanorod arrays were obtained under the optional growth conditions, i.e., three hydrothermal reactions for 150 min, three rounds of dip-coating, 0.5 mol·L-1 precursor solution concentration, and 24 h aging.
2015, 31(11): 2220-2228
doi: 10.3866/PKU.WHXB201510131
Abstract:
A new carbon-coated SnO2 hollow fiber was successfully prepared by coaxial electrospinning, and its supercapacitor properties were well studied. The surface morphology and structure were examined using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the Brunauer-Emmett-Teller (BET) method. The results showed hollow fibers of average diameter 1 μm and carbon-coated SnO2 particles of average size 3-15 nm uniformly distributed on the fiber shell. The surface area was 565 m2·g-1. In a three-electrode system, the electrode achieved a respectable specific capacitance of 397.5 F·g-1 at 0.25 A·g-1, and the capacitance retained ratio was still 88% of the initial value after 3000 cycles at 1.0 A·g-1. In the case of a symmetrical two-electrode system, the electrode achieved a specific capacitance of 162.0 F·g-1 at 0.25 A·g-1 current density, and the capacitance retained ratio was 84% of the initial value after 3000 cycles at 1.0 A·g-1.
A new carbon-coated SnO2 hollow fiber was successfully prepared by coaxial electrospinning, and its supercapacitor properties were well studied. The surface morphology and structure were examined using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the Brunauer-Emmett-Teller (BET) method. The results showed hollow fibers of average diameter 1 μm and carbon-coated SnO2 particles of average size 3-15 nm uniformly distributed on the fiber shell. The surface area was 565 m2·g-1. In a three-electrode system, the electrode achieved a respectable specific capacitance of 397.5 F·g-1 at 0.25 A·g-1, and the capacitance retained ratio was still 88% of the initial value after 3000 cycles at 1.0 A·g-1. In the case of a symmetrical two-electrode system, the electrode achieved a specific capacitance of 162.0 F·g-1 at 0.25 A·g-1 current density, and the capacitance retained ratio was 84% of the initial value after 3000 cycles at 1.0 A·g-1.
