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2008 Volume 24 Issue 2
2008, 24(02):
Abstract:
2008, 24(02): 187-192
doi: 10.1016/S1872-1508(08)60007-8
Abstract:
A series of derivatives were designed based on the model compound 1,4-divinyphenyl-bridged triphenylene, and the structures were studied using the AM1 method and density functional theory (DFT) at the B3LYP/3-21G level. On the basis of the B3LYP/3-21G optimized geometries, the electronic spectra and 13C NMR spectra of the derivatives were calculated using the INDO/CIS and B3LYP/3-21G methods, respectively. The energy gaps, abilities of accepting holes, and thermal stabilities were affected by the number and electron-donating capability as well as steric effect of the substituents. The red shifts of the first and main absorptions in the electronic spectra of the derivatives relative to those of the parent compound were predicted in the presence of the groups —CN and —OH. The chemical shift of the carbon atom on —CN was transferred to the low field under the effect of the nitrogen atom. The chemical shifts of the carbon atoms associated with —CN were transformed into the high field owing to the high electron density. The chemical shifts of the carbon atoms on the conjugation skeleton were almost unchanged.
A series of derivatives were designed based on the model compound 1,4-divinyphenyl-bridged triphenylene, and the structures were studied using the AM1 method and density functional theory (DFT) at the B3LYP/3-21G level. On the basis of the B3LYP/3-21G optimized geometries, the electronic spectra and 13C NMR spectra of the derivatives were calculated using the INDO/CIS and B3LYP/3-21G methods, respectively. The energy gaps, abilities of accepting holes, and thermal stabilities were affected by the number and electron-donating capability as well as steric effect of the substituents. The red shifts of the first and main absorptions in the electronic spectra of the derivatives relative to those of the parent compound were predicted in the presence of the groups —CN and —OH. The chemical shift of the carbon atom on —CN was transferred to the low field under the effect of the nitrogen atom. The chemical shifts of the carbon atoms associated with —CN were transformed into the high field owing to the high electron density. The chemical shifts of the carbon atoms on the conjugation skeleton were almost unchanged.
2008, 24(02): 193-196
doi: 10.1016/S1872-1508(08)60008-X
Abstract:
ZnS nanowires were successfully synthesized through the direct reaction of Zn and S vapor via carbon-assisted chemical evaporation deposition method with Au catalyst. The investigations indicated that the size of ZnS nanowires with a diameter of approximately 40 nm was uniform along the axis of the wire and the surfaces were slick. The ZnS nanowire with a hexa nal wurtzite structure was a typical single crystalline structure. HRTEM and SEAD results demonstrated that the nanowire grew along [1100] direction, which was different from the common direction reported in literatures. The growth of nanowires was controlled by vapor-liquid-solid (VLS) mechanism.
ZnS nanowires were successfully synthesized through the direct reaction of Zn and S vapor via carbon-assisted chemical evaporation deposition method with Au catalyst. The investigations indicated that the size of ZnS nanowires with a diameter of approximately 40 nm was uniform along the axis of the wire and the surfaces were slick. The ZnS nanowire with a hexa nal wurtzite structure was a typical single crystalline structure. HRTEM and SEAD results demonstrated that the nanowire grew along [1100] direction, which was different from the common direction reported in literatures. The growth of nanowires was controlled by vapor-liquid-solid (VLS) mechanism.
2008, 24(02): 197-200
doi: 10.1016/S1872-1508(08)60009-1
Abstract:
A simplified Monte Carlo model was proposed to simulate the oscillatory behavior during catalytic partial oxidation of methane. Using the Langmuir-Hinshelwood mechanism, the oscillatory behavior was observed in both reaction rates and coverages of adsorbed species. The influence of oxidation and reduction of the catalyst surface on the oscillations was investigated, and the analysis showed that the fast oxidation and slow reduction of the catalyst surface resulted in the oscillatory behavior.
A simplified Monte Carlo model was proposed to simulate the oscillatory behavior during catalytic partial oxidation of methane. Using the Langmuir-Hinshelwood mechanism, the oscillatory behavior was observed in both reaction rates and coverages of adsorbed species. The influence of oxidation and reduction of the catalyst surface on the oscillations was investigated, and the analysis showed that the fast oxidation and slow reduction of the catalyst surface resulted in the oscillatory behavior.
2008, 24(02): 201-204
doi: 10.1016/S1872-1508(08)60010-8
Abstract:
The electrochemical processes of irreversibly adsorbed antimony (Sbad) on Au electrode were investigated by cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM). CV data showed that Sbad on Au electrode yielded oxidation and reduction features at about 0.15 V (vs saturated calomel electrode, SCE). EQCM data indicated that Sbad specieswere stable on Au electrode in the potential region from-0.25 to 0.18 V (vs SCE); the adsorption of Sb inhibited the adsorption of water and anion on Au electrode at low electrode potentials. Sb2O3 species was suggested to form on the Au electrode at 0.18 V. At a potential higher than 0.20 V the Sb2O3 species could be further oxidized to Sb(V) oxidation state and then desorbed fromAu electrode.
The electrochemical processes of irreversibly adsorbed antimony (Sbad) on Au electrode were investigated by cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM). CV data showed that Sbad on Au electrode yielded oxidation and reduction features at about 0.15 V (vs saturated calomel electrode, SCE). EQCM data indicated that Sbad specieswere stable on Au electrode in the potential region from-0.25 to 0.18 V (vs SCE); the adsorption of Sb inhibited the adsorption of water and anion on Au electrode at low electrode potentials. Sb2O3 species was suggested to form on the Au electrode at 0.18 V. At a potential higher than 0.20 V the Sb2O3 species could be further oxidized to Sb(V) oxidation state and then desorbed fromAu electrode.
2008, 24(02): 205-210
doi: 10.3866/PKU.WHXB20080205
Abstract:
La1-xCexCoO3 (x=0, 0.05, 0.1, 0.2, 0.3) catalysts were synthesized by amorphous heteronuclear complexing method. The catalysts were characterized by XRD, TEM, and N2 adsorption isotherms. The cataluminescence (CTL) response to CO and the activities in the oxidation of CO over the catalysts were investigated. Results showed that La1-xCeyφx-yCoO3 perovskite with lanthanumdeficiency, CeO2 and CO3O4 phases were formed after La3+ was substituted with Ce4+ in the catalyst. Compared with LaCoO3 catalyst, the catalyst with x=0.1 showed the highest activity for CO oxidation (T100%=290 ℃). The CTL result is well consistent with the order of CO catalytic activity over La1-xCexCoO3 catalysts.
La1-xCexCoO3 (x=0, 0.05, 0.1, 0.2, 0.3) catalysts were synthesized by amorphous heteronuclear complexing method. The catalysts were characterized by XRD, TEM, and N2 adsorption isotherms. The cataluminescence (CTL) response to CO and the activities in the oxidation of CO over the catalysts were investigated. Results showed that La1-xCeyφx-yCoO3 perovskite with lanthanumdeficiency, CeO2 and CO3O4 phases were formed after La3+ was substituted with Ce4+ in the catalyst. Compared with LaCoO3 catalyst, the catalyst with x=0.1 showed the highest activity for CO oxidation (T100%=290 ℃). The CTL result is well consistent with the order of CO catalytic activity over La1-xCexCoO3 catalysts.
2008, 24(02): 211-216
doi: 10.3866/PKU.WHXB20080206
Abstract:
La0.8Sr0.2FeMn1.5Al9.5O19-δ (LSFMAO) hexaaluminate aerosol was prepared by co-precipitation combined with supercritical drying and high temperature calcinations. XRD, SEM, BET, TPR characterizations as well as methane catalytic combustion were performed to investigate the effects of supercritical drying and high temperature calcinations on the structure and reactivity of the catalysts. The results indicated that the plate-like LSFMAO hexaaluminate aerosol was formed after calcination of the aerosol precursors at 1200 ℃. The as-prepared LSFMAO hexaaluminate possesses large specific surface area (16 m2·g-1) and excellent catalytic combustion activity at high gas space velocity. However, further calcinations of the LSFMAO hexaaluminate at 1300 ℃ and 1400 ℃ resulted in severe sintering and reduction of catalytic activity. These results revealed that supercritical drying was helpful to promote the combustion activity and resist sintering of the LSFMAO hexaaluminate up to 1200 ℃ above which the sintering resistance and redox performance of LSFMAO hexaaluminates were mainly determined by the components and intrinsic properties.
La0.8Sr0.2FeMn1.5Al9.5O19-δ (LSFMAO) hexaaluminate aerosol was prepared by co-precipitation combined with supercritical drying and high temperature calcinations. XRD, SEM, BET, TPR characterizations as well as methane catalytic combustion were performed to investigate the effects of supercritical drying and high temperature calcinations on the structure and reactivity of the catalysts. The results indicated that the plate-like LSFMAO hexaaluminate aerosol was formed after calcination of the aerosol precursors at 1200 ℃. The as-prepared LSFMAO hexaaluminate possesses large specific surface area (16 m2·g-1) and excellent catalytic combustion activity at high gas space velocity. However, further calcinations of the LSFMAO hexaaluminate at 1300 ℃ and 1400 ℃ resulted in severe sintering and reduction of catalytic activity. These results revealed that supercritical drying was helpful to promote the combustion activity and resist sintering of the LSFMAO hexaaluminate up to 1200 ℃ above which the sintering resistance and redox performance of LSFMAO hexaaluminates were mainly determined by the components and intrinsic properties.
2008, 24(02): 217-222
doi: 10.3866/PKU.WHXB20080207
Abstract:
The adducts R3SiX-NR’3 (R=H, CH3; X=F, Cl, Br, I; R’=H, CH3) formed in two addition modes were studied with DFT at B3LYP/6-31g(d,p) level (Xatoms used the cep-121g base-set): one type was the adducts approached axially along the Si—X bond, the other type was the adducts approached laterally along the Si—X bond. The computed results showed that the former was more stable and more easily to be formed. The presence of group with pushing electron effect on Si made it difficult to form Si—N bond and the reverse was true on NR’3. NH3-H3SiX and N(CH3)3-H3SiX series can form two kinds of adducts. NH3-H2(CH3)SiX series can only form one kind of adduct. NH3-H(CH3)2SiX and NH3-(CH3)3SiX series can not form any adducts. The adduct of X=Cl is the most stable one in the same series. The bonding properties of all the adducts, the change of NBO charges, the influence of various halogen atoms and methyl on the structures and the stability of adducts were analyzed. The possibility of being conductive of adducts H3SiX-NH3 and H3SiX-N(CH3)3 in organic solvents was also discussed.
The adducts R3SiX-NR’3 (R=H, CH3; X=F, Cl, Br, I; R’=H, CH3) formed in two addition modes were studied with DFT at B3LYP/6-31g(d,p) level (Xatoms used the cep-121g base-set): one type was the adducts approached axially along the Si—X bond, the other type was the adducts approached laterally along the Si—X bond. The computed results showed that the former was more stable and more easily to be formed. The presence of group with pushing electron effect on Si made it difficult to form Si—N bond and the reverse was true on NR’3. NH3-H3SiX and N(CH3)3-H3SiX series can form two kinds of adducts. NH3-H2(CH3)SiX series can only form one kind of adduct. NH3-H(CH3)2SiX and NH3-(CH3)3SiX series can not form any adducts. The adduct of X=Cl is the most stable one in the same series. The bonding properties of all the adducts, the change of NBO charges, the influence of various halogen atoms and methyl on the structures and the stability of adducts were analyzed. The possibility of being conductive of adducts H3SiX-NH3 and H3SiX-N(CH3)3 in organic solvents was also discussed.
2008, 24(02): 223-229
doi: 10.1016/S1872-1508(08)60011-X
Abstract:
A modified approach to prepare novel amphipathic octadecyl-quaternized carboxymethyl chitosan (QACMC) was reported, in which carboxymethyl chitosan (CMC), prepared fromchitosan, was made to react with glycidyl octadecyl dimethylammonium chloride; thus, the octadecyl quaternary ammonium group was introduced into CMC. The structure and thermal properties of these derivatives were characterized by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H-NMR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The crystalline properties of QACMC were perfect, and it had a high degree of crystallinity. All the chitosan derivatives had od thermal stability when the temperature was lower than 200 ℃. The moisture-absorption and retention abilities of QACMC were lower than that of hyaluronic acid (HA) and CMC. The carboxymethyl and quaternary ammonium groups did not show a synergistic effect, and the effects of both the molar mass and the hydrophobic side chains of long alkyl moieties were important. Minocycline hydrochloride was successfully incorporatedintoQACMCpolymeric micelles with a remarkably highe fficiency (10.9%,mass fraction). QACMCpromises to be a high-potential delivery vector for lipophilic drugs.
A modified approach to prepare novel amphipathic octadecyl-quaternized carboxymethyl chitosan (QACMC) was reported, in which carboxymethyl chitosan (CMC), prepared fromchitosan, was made to react with glycidyl octadecyl dimethylammonium chloride; thus, the octadecyl quaternary ammonium group was introduced into CMC. The structure and thermal properties of these derivatives were characterized by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H-NMR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The crystalline properties of QACMC were perfect, and it had a high degree of crystallinity. All the chitosan derivatives had od thermal stability when the temperature was lower than 200 ℃. The moisture-absorption and retention abilities of QACMC were lower than that of hyaluronic acid (HA) and CMC. The carboxymethyl and quaternary ammonium groups did not show a synergistic effect, and the effects of both the molar mass and the hydrophobic side chains of long alkyl moieties were important. Minocycline hydrochloride was successfully incorporatedintoQACMCpolymeric micelles with a remarkably highe fficiency (10.9%,mass fraction). QACMCpromises to be a high-potential delivery vector for lipophilic drugs.
2008, 24(02): 230-236
doi: 10.1016/S1872-1508(08)60012-1
Abstract:
The electrochemical quartz crystal microbalance (EQCM) technique was used to investigate the electrodeposition of the charge-transfer complex (CTC) generated during electrooxidation of o-tolidine (o-TD) in Britton-Robinson (B-R) buffers and effects of coexisting chondroitin sulfate (CS). A V-shaped frequency response to the cyclic voltammetric switching of o-TD indicated the precipitation and dissolution of the poorly soluble CTC, an oxidation intermediate, formed at the Au electrode during the redox switching of o-TD in a neutral or a weakly acidic medium (pH=4.07-6.50). The effects of potential scan rate, solution pH, and several supporting electrolytes were examined. The depth of the V-shaped frequency curves (-⊿f0V) was related to the supporting electrolyte used, with a decreasing sequence for -⊿f0V as 0.20 mol·L-1 NaNO3>0.20 mol·L-1 NaClO4>0.10 mol·L-1 Na2SO4. The -⊿f0V response to the redox switching of the CTC/o-TD“couple”was enhanced by the introduction of CS because of the formation of the CTC-CS adduct, as also characterized and supported by UV-Vis and FTIR spectrophotometry. The molar ratio (x) of the CTCto CSin the adduct and the electrode-collection efficiency of the CTC (η) were estimated using EQCM. The values of -⊿f0V increased with the increase in CS concentration, with a linear range from 0.75 to 15.2 μmol·L-1, and a detection limit down to 50 nmol·L-1. The new method proposed for CS assay was characterized by a dynamically renewed surface of the detection electrode.
The electrochemical quartz crystal microbalance (EQCM) technique was used to investigate the electrodeposition of the charge-transfer complex (CTC) generated during electrooxidation of o-tolidine (o-TD) in Britton-Robinson (B-R) buffers and effects of coexisting chondroitin sulfate (CS). A V-shaped frequency response to the cyclic voltammetric switching of o-TD indicated the precipitation and dissolution of the poorly soluble CTC, an oxidation intermediate, formed at the Au electrode during the redox switching of o-TD in a neutral or a weakly acidic medium (pH=4.07-6.50). The effects of potential scan rate, solution pH, and several supporting electrolytes were examined. The depth of the V-shaped frequency curves (-⊿f0V) was related to the supporting electrolyte used, with a decreasing sequence for -⊿f0V as 0.20 mol·L-1 NaNO3>0.20 mol·L-1 NaClO4>0.10 mol·L-1 Na2SO4. The -⊿f0V response to the redox switching of the CTC/o-TD“couple”was enhanced by the introduction of CS because of the formation of the CTC-CS adduct, as also characterized and supported by UV-Vis and FTIR spectrophotometry. The molar ratio (x) of the CTCto CSin the adduct and the electrode-collection efficiency of the CTC (η) were estimated using EQCM. The values of -⊿f0V increased with the increase in CS concentration, with a linear range from 0.75 to 15.2 μmol·L-1, and a detection limit down to 50 nmol·L-1. The new method proposed for CS assay was characterized by a dynamically renewed surface of the detection electrode.
2008, 24(02): 237-242
doi: 10.3866/PKU.WHXB20080210
Abstract:
A novel crystallite carbon (NCC)was prepared by KOH activation of carbonized petroleumcoke precursors. The porous structure, crystallite structure, and microstructure were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), and high resolution transmission electron microscopy (HRTEM) measurements, respectively. The capacitive behavior of the NCC electrodes was also examined with 1 mol·L-1 tetraethylammonium tetrafluoroborate (Et4NBF4) solution in propylene carbonate (PC). It was found that the NCC was composed of much well-grown graphite-like crystallite with average interlayer spacing (d002) of 0.377 nm. The NCC had lower surface area (130.7 m2·g-1) and more distinct crystal character than activated carbon (AC). The energy storage for the NCC depended on the intercalation of electrolyte ions into graphite-like crystallite layers. The specific capacitance of the NCC was 110.6 F·g-1, showing specific energy of 27.5 Wh·kg-1, specific power of over 1.2 kW·kg-1 and excellent cycle stability. Therefore, the crystallite carbon is a promising candidate for novel electrode material.
A novel crystallite carbon (NCC)was prepared by KOH activation of carbonized petroleumcoke precursors. The porous structure, crystallite structure, and microstructure were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), and high resolution transmission electron microscopy (HRTEM) measurements, respectively. The capacitive behavior of the NCC electrodes was also examined with 1 mol·L-1 tetraethylammonium tetrafluoroborate (Et4NBF4) solution in propylene carbonate (PC). It was found that the NCC was composed of much well-grown graphite-like crystallite with average interlayer spacing (d002) of 0.377 nm. The NCC had lower surface area (130.7 m2·g-1) and more distinct crystal character than activated carbon (AC). The energy storage for the NCC depended on the intercalation of electrolyte ions into graphite-like crystallite layers. The specific capacitance of the NCC was 110.6 F·g-1, showing specific energy of 27.5 Wh·kg-1, specific power of over 1.2 kW·kg-1 and excellent cycle stability. Therefore, the crystallite carbon is a promising candidate for novel electrode material.
2008, 24(02): 243-249
doi: 10.1016/S1872-1508(08)60013-3
Abstract:
The effect of pH value on the adsorption behavior and inhibition mechanism of dodecylamine for carbon dioxide corrosion of carbon steel was investigated by electrochemical methods and scanning electron microscopy (SEM). The results indicated that the pH value of the solution played the crucial role to the adsorption behavior and inhibition mechanismof dodecylamine. The inhibition performance of dodecylamine on carbon steel was dependent on the pH value and the inhibition efficiency increased with the increase of pH value. At pH 4.9, dodecylamine mainly inhibited the cathode process of the corrosion. The adsorption energy of dodecylamine on the metal surface was lower. The adsorption of dodecylamine on the metal surface was not stable and an anode desorption phenomenon could be observed. Hence, dodecylamine did not provide effective inhibition to the corrosion. While at pH 6.9, it had much higher adsorption energy. Dodecylamine adsorbed on the metal surface tightly and formed the effective diffusion barrier which inhibited both the cathode and anode processes effectively.
The effect of pH value on the adsorption behavior and inhibition mechanism of dodecylamine for carbon dioxide corrosion of carbon steel was investigated by electrochemical methods and scanning electron microscopy (SEM). The results indicated that the pH value of the solution played the crucial role to the adsorption behavior and inhibition mechanismof dodecylamine. The inhibition performance of dodecylamine on carbon steel was dependent on the pH value and the inhibition efficiency increased with the increase of pH value. At pH 4.9, dodecylamine mainly inhibited the cathode process of the corrosion. The adsorption energy of dodecylamine on the metal surface was lower. The adsorption of dodecylamine on the metal surface was not stable and an anode desorption phenomenon could be observed. Hence, dodecylamine did not provide effective inhibition to the corrosion. While at pH 6.9, it had much higher adsorption energy. Dodecylamine adsorbed on the metal surface tightly and formed the effective diffusion barrier which inhibited both the cathode and anode processes effectively.
2008, 24(02): 250-256
doi: 10.3866/PKU.WHXB20080212
Abstract:
A simulation study was performed for the effects of six different cooling rates on microstructure during solidification of liquid metal Zn adopting molecular dynamics method. The pair distribution function g(r) curves, the total energy per atom, the bond-type index method and the cluster-type index method (CTIM-2) were used to analyze the variations of microstructure during the solidification process. The results showed that the cooling rate played a critical role in the microstructure transitions. As the cooling rate being 1×1014, 5×1013, 2×1013, 1×1013, 5×1012 K·s -1, the amorphous structures would be formed with 1551, 1541 and 1431 bond-types as the main body in the system. As the cooling rate being 1×1012 K·s-1, a part of crystal structure would be formed, in which the hcp and fcc basic cluster structures with 1421 and 1422 bond-types coexisted as the main body. At the same time, it was found that the glass transition temperature Tg would be decreased with the cooling rate slowing down.
A simulation study was performed for the effects of six different cooling rates on microstructure during solidification of liquid metal Zn adopting molecular dynamics method. The pair distribution function g(r) curves, the total energy per atom, the bond-type index method and the cluster-type index method (CTIM-2) were used to analyze the variations of microstructure during the solidification process. The results showed that the cooling rate played a critical role in the microstructure transitions. As the cooling rate being 1×1014, 5×1013, 2×1013, 1×1013, 5×1012 K·s -1, the amorphous structures would be formed with 1551, 1541 and 1431 bond-types as the main body in the system. As the cooling rate being 1×1012 K·s-1, a part of crystal structure would be formed, in which the hcp and fcc basic cluster structures with 1421 and 1422 bond-types coexisted as the main body. At the same time, it was found that the glass transition temperature Tg would be decreased with the cooling rate slowing down.
2008, 24(02): 257-262
doi: 10.3866/PKU.WHXB20080213
Abstract:
Using density functional theory associated with B3LYP method with 6-31G** and Lanl2dz basis sets, the optimization of the geometries and the calculation of frequencies for (MN)nHm (M=Ga, In; n= 1-4; m=1, 2) clusters were carried out, respectively. In addition, the most stable structures, binding energy of hydrogen atom, and energy gap were obtained. The results showed that the ground state structures of (MN)nH (M=Ga, In; n=1-4) and (MN)nH2(M=Ga, In; n=1-4) clusters were doublet and singlet states, respectively. When the number of hydrogen atom was one, the isomer in which hydrogen atomwas added in nitrogen atomwas more stable than that in M(M=Ga, In) atom. If there was a N3 unit, the isomers in which hydrogen atom was added in nitrogen atom of either side in N3 unit were the same and the most stable. While the number of hydrogen atom was two, except for n is equal to one, the isomer in which two hydrogen atoms were added in nitrogen atoms, respectively, was the most stable. If there was a N3 unit, the isomer in which two hydrogen atoms were added in the two farthest nitrogen atoms in N3 unit, respectively, was the most stable. Larger binding energies of a single hydrogen atom on small MN clusters and larger highest occupied and lowest unoccupied molecular-orbital energy gaps for GaNH, (GaN)3H, and InNH make these species have more stable.
Using density functional theory associated with B3LYP method with 6-31G** and Lanl2dz basis sets, the optimization of the geometries and the calculation of frequencies for (MN)nHm (M=Ga, In; n= 1-4; m=1, 2) clusters were carried out, respectively. In addition, the most stable structures, binding energy of hydrogen atom, and energy gap were obtained. The results showed that the ground state structures of (MN)nH (M=Ga, In; n=1-4) and (MN)nH2(M=Ga, In; n=1-4) clusters were doublet and singlet states, respectively. When the number of hydrogen atom was one, the isomer in which hydrogen atomwas added in nitrogen atomwas more stable than that in M(M=Ga, In) atom. If there was a N3 unit, the isomers in which hydrogen atom was added in nitrogen atom of either side in N3 unit were the same and the most stable. While the number of hydrogen atom was two, except for n is equal to one, the isomer in which two hydrogen atoms were added in nitrogen atoms, respectively, was the most stable. If there was a N3 unit, the isomer in which two hydrogen atoms were added in the two farthest nitrogen atoms in N3 unit, respectively, was the most stable. Larger binding energies of a single hydrogen atom on small MN clusters and larger highest occupied and lowest unoccupied molecular-orbital energy gaps for GaNH, (GaN)3H, and InNH make these species have more stable.
2008, 24(02): 263-268
doi: 10.3866/PKU.WHXB20080214
Abstract:
Nanostructured Co3O4 with different morphologies was synthesized by solvothermal method using different cobalt salts in water and n-butanol solvent system. The structure and morphology of the products were characterized by X-ray diffraction (XRD) and transmission electronmicroscopy (TEM). The results showed that the shape and size of Co3O4 could be controlled by altering the anions in the reaction system. Electrochemical properties of Co3O4 electrode were characterized by cyclic voltammetry (CV), galvanostatic charge/discharge and alternating current (AC) impedance method. The results indicated that the shape and size of Co3O4 had remarkable influence on its capacitive performance. In the potential range of -0.40-0.55 V(vs SCE), the spherical Co3O4 obtained from cobalt nitrate showed excellent capacitance performance in 2 mol·L -1 KOH electrolyte. The initial specific capacitance of single Co3O4 electrode reached 362.0 F·g-1 and 90% was maintained after 400 cycles.
Nanostructured Co3O4 with different morphologies was synthesized by solvothermal method using different cobalt salts in water and n-butanol solvent system. The structure and morphology of the products were characterized by X-ray diffraction (XRD) and transmission electronmicroscopy (TEM). The results showed that the shape and size of Co3O4 could be controlled by altering the anions in the reaction system. Electrochemical properties of Co3O4 electrode were characterized by cyclic voltammetry (CV), galvanostatic charge/discharge and alternating current (AC) impedance method. The results indicated that the shape and size of Co3O4 had remarkable influence on its capacitive performance. In the potential range of -0.40-0.55 V(vs SCE), the spherical Co3O4 obtained from cobalt nitrate showed excellent capacitance performance in 2 mol·L -1 KOH electrolyte. The initial specific capacitance of single Co3O4 electrode reached 362.0 F·g-1 and 90% was maintained after 400 cycles.
2008, 24(02): 269-274
doi: 10.3866/PKU.WHXB20080215
Abstract:
The theoretical studies on the mechanisms of ring-opening reaction of 8-hydroxyguanine radical were performed by the experimentally calibrated theoretical method of B3LYP/DZP++. All of the computational results revealed that the ring-opening reaction occured through a pathway including two elementary reactions, the C8—N9 bond-broken step followed by a transfer step of cation-like hydrogen atom of the hydroxyl moiety. The high activation energy in the transfer reaction of hydrogen atom in the absence of water led this reaction to be somewhat difficult; on the contrary, the hydrogen transfer might occur feasibly with assistance of one water molecule due to the formation of a six-member ring transition state which was beneficial to lower the reaction activation energy. The difference of the activation energies of two elementary reactions demonstrated that the rate-limiting steps of ring-opening reaction in the absence of water and in the presence of water were the hydrogen transfer step and C8—N9 bond-broken process, respectively.
The theoretical studies on the mechanisms of ring-opening reaction of 8-hydroxyguanine radical were performed by the experimentally calibrated theoretical method of B3LYP/DZP++. All of the computational results revealed that the ring-opening reaction occured through a pathway including two elementary reactions, the C8—N9 bond-broken step followed by a transfer step of cation-like hydrogen atom of the hydroxyl moiety. The high activation energy in the transfer reaction of hydrogen atom in the absence of water led this reaction to be somewhat difficult; on the contrary, the hydrogen transfer might occur feasibly with assistance of one water molecule due to the formation of a six-member ring transition state which was beneficial to lower the reaction activation energy. The difference of the activation energies of two elementary reactions demonstrated that the rate-limiting steps of ring-opening reaction in the absence of water and in the presence of water were the hydrogen transfer step and C8—N9 bond-broken process, respectively.
2008, 24(02): 275-280
doi: 10.3866/PKU.WHXB20080216
Abstract:
Based on energy dispersion relation of the single-walled carbon nanotubes (SWCNTs), the electronic velocity and effective mass of the lowest conduction band for the SWCNTs were computed, and the relation of the electronic velocity and effective mass with the wave vector and diameters of the SWCNTs were discussed emphatically. The calculated results show that the electronic velocity and effective mass significantly depend on the structure parameter of the semiconducting zigzag-SWCNTs such as their diameter. The electronic velocity and effective mass of the lowest conduction band for various armchair (always metallic) SWCNTs and metallic zigzag-SWCNTs have the same changing curves versus the wave vector, but for various semiconducting zigzag-SWCNTs the electronic velocity and effective mass of the lowest conduction band have different changing curves versus the wave vector. This means that under the low bias voltage, various metallic zigzag-SWCNTs and armchair SWCNTS with different diameters have the same transport properties, while the semiconducting zigzag-SWCNTs with different diameters have different transport properties.
Based on energy dispersion relation of the single-walled carbon nanotubes (SWCNTs), the electronic velocity and effective mass of the lowest conduction band for the SWCNTs were computed, and the relation of the electronic velocity and effective mass with the wave vector and diameters of the SWCNTs were discussed emphatically. The calculated results show that the electronic velocity and effective mass significantly depend on the structure parameter of the semiconducting zigzag-SWCNTs such as their diameter. The electronic velocity and effective mass of the lowest conduction band for various armchair (always metallic) SWCNTs and metallic zigzag-SWCNTs have the same changing curves versus the wave vector, but for various semiconducting zigzag-SWCNTs the electronic velocity and effective mass of the lowest conduction band have different changing curves versus the wave vector. This means that under the low bias voltage, various metallic zigzag-SWCNTs and armchair SWCNTS with different diameters have the same transport properties, while the semiconducting zigzag-SWCNTs with different diameters have different transport properties.
2008, 24(02): 281-288
doi: 10.3866/PKU.WHXB20080217
Abstract:
Epidermal growth factor receptor (EGFR) protein tyrosine kinases (TK) are attractive targets for anti-tumor drug design. So, a od pharmacophore model of EGFR TK inhibitors will be propitious to design new EGFR TK inhibitors. 80 compounds reported EGFR TK inhibitors which work at the ATP-binding domain were chosen to construct several pharmacophore models with the help of Catalyst software. Based on the action mechanism and the 3D structure of the EGFR tyrosine kinases, a fitting pharmacophore model (RMS=0.438, Correl=0.908, Weight=1.52, Config=17.36) including two aromatic ring centers (RA), an aliphatic hydrophobic core (HP) and a positive ionizable center (PI) was confirmed. This model revealed that the RA and HP group may act on ATP binding pocket, and the PI may act on the surface of ATP binding pocket. Therefore, this study could provide new hints for denovo design of new EGFR inhibitors with observable structure and predictable activity (screened in silico).
Epidermal growth factor receptor (EGFR) protein tyrosine kinases (TK) are attractive targets for anti-tumor drug design. So, a od pharmacophore model of EGFR TK inhibitors will be propitious to design new EGFR TK inhibitors. 80 compounds reported EGFR TK inhibitors which work at the ATP-binding domain were chosen to construct several pharmacophore models with the help of Catalyst software. Based on the action mechanism and the 3D structure of the EGFR tyrosine kinases, a fitting pharmacophore model (RMS=0.438, Correl=0.908, Weight=1.52, Config=17.36) including two aromatic ring centers (RA), an aliphatic hydrophobic core (HP) and a positive ionizable center (PI) was confirmed. This model revealed that the RA and HP group may act on ATP binding pocket, and the PI may act on the surface of ATP binding pocket. Therefore, this study could provide new hints for denovo design of new EGFR inhibitors with observable structure and predictable activity (screened in silico).
2008, 24(02): 289-295
doi: 10.3866/PKU.WHXB20080218
Abstract:
The side-on bounded FeN2 (s-FeN2 for short) structure was calculated using B3LYP/6-311+G(d) method. The geometric structures, electronic structures, energies, and vibrational frequencies were calculated for many stable electronic states, van der Waals force interaction states, and transition states with different spin multiplicities. The results showed that: (1) the Fe—N bond length R1 and N—N bond length R2 were close to each other among the same kind states; (2) the fourmost stable electronic states of the side-on bounded FeN2were 15B2, 15B1, 13B1, and 13B2, the energy differences were about 25 kJ·mol-1; the electronic structures of the triplet states were plentiful, most of the singlet states were much higher in total energies than triplets’ and quintets’; (3) there have no fragment orbital overlap and electron transfer in S-FeN2 when Fe atom takes on 3d64s2 configuration due to the strong electron repulsion between σ or π electron pairs. To the other excited-state configurations 4s13d7, 4s13d64p1, and 3d74p1, there were some electrons transfer from Fe atom to N2 molecule via σ(sd)-π and π-π* orbitals overlap, the systems present somewhat ionicity and the bond length of activated N2 is generally not larger than 120 pm, that means Fe atom cannot insert into N≡N; (4) if electrons were excited to the molecular orbitals composed by nitrogen molecule moiety π-orbitals, the N2 could be activated to single bond even dissociation.
The side-on bounded FeN2 (s-FeN2 for short) structure was calculated using B3LYP/6-311+G(d) method. The geometric structures, electronic structures, energies, and vibrational frequencies were calculated for many stable electronic states, van der Waals force interaction states, and transition states with different spin multiplicities. The results showed that: (1) the Fe—N bond length R1 and N—N bond length R2 were close to each other among the same kind states; (2) the fourmost stable electronic states of the side-on bounded FeN2were 15B2, 15B1, 13B1, and 13B2, the energy differences were about 25 kJ·mol-1; the electronic structures of the triplet states were plentiful, most of the singlet states were much higher in total energies than triplets’ and quintets’; (3) there have no fragment orbital overlap and electron transfer in S-FeN2 when Fe atom takes on 3d64s2 configuration due to the strong electron repulsion between σ or π electron pairs. To the other excited-state configurations 4s13d7, 4s13d64p1, and 3d74p1, there were some electrons transfer from Fe atom to N2 molecule via σ(sd)-π and π-π* orbitals overlap, the systems present somewhat ionicity and the bond length of activated N2 is generally not larger than 120 pm, that means Fe atom cannot insert into N≡N; (4) if electrons were excited to the molecular orbitals composed by nitrogen molecule moiety π-orbitals, the N2 could be activated to single bond even dissociation.
2008, 24(02): 296-300
doi: 10.3866/PKU.WHXB20080219
Abstract:
CdTe nanocrystals were synthesized in aqueous solution with different stabilizers (L-cysteine hydrochloride (L-Cys), 3-mercaptopropionic acid (MPA), 1-thioglycerol (TG), and thioglycolic acid (TGA)) by a simple route, and were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), and X-ray diffraction pattern (XRD). The effect of aqueous synthesis conditions on the optical properties of CdTe nanocrystals was investigated and it was found that the molar ratio of Cd/Te, pH value, refluxing time, and different stabilizers significantly affected the optical properties of CdTe nanocrystals. The obtained CdTe nanocrystals exhibited a favorable narrow emission band under different conditions. The photoluminescence (PL) peaks and absorption peaks could be tuned by changing the synthesis conditions of CdTe nanocrystals. Different PL quantum yields (QY) were obtained using different stabilizers. The PL peak position of CdTe nanocrystals did not show significant shift under different excitation wavelengths.
CdTe nanocrystals were synthesized in aqueous solution with different stabilizers (L-cysteine hydrochloride (L-Cys), 3-mercaptopropionic acid (MPA), 1-thioglycerol (TG), and thioglycolic acid (TGA)) by a simple route, and were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), and X-ray diffraction pattern (XRD). The effect of aqueous synthesis conditions on the optical properties of CdTe nanocrystals was investigated and it was found that the molar ratio of Cd/Te, pH value, refluxing time, and different stabilizers significantly affected the optical properties of CdTe nanocrystals. The obtained CdTe nanocrystals exhibited a favorable narrow emission band under different conditions. The photoluminescence (PL) peaks and absorption peaks could be tuned by changing the synthesis conditions of CdTe nanocrystals. Different PL quantum yields (QY) were obtained using different stabilizers. The PL peak position of CdTe nanocrystals did not show significant shift under different excitation wavelengths.
2008, 24(02): 301-306
doi: 10.3866/PKU.WHXB20080220
Abstract:
A three-dimensional pharmacophore model of 3-hydro-3-methyl glutaryl coenzyme A (HMG-CoA) reductase inhibitors (RI)was developed based on 21 HMG-CoAreductase inhibitors froma rat liver. The selected training set had great diversity in both molecular structure and bioactivity as required by HypoGen program in the Catalyst software. The inhibitors in training set showed HMG-CoA RI inhibiting activity with IC50 values of 0.3-8000 nmol·L-1. The best statistical hypothesis, consisting of four features, one hydrogen-bond acceptor, one hydrogen-bond donor, one ring aromatic feature, and one hydrophobic point, had a correlation coefficient of 0.8883, a root-mean-square (RMS) deviation of 1.269, a Fixed cost of 88.75, a Total cost of 111.5, and a Configuration cost of 16.98, this hypothesis had highly predictive ability. The predictive ability was approved by the results of the activity estimated by mapping the compounds of the testing set with it. The cross-validation provided strong confidence on this hypothesis. This pharmacophore model can contribute to the finding and designing of new-type HMG-CoA reductase inhibitors, and to the development of traditional Chinese medicine and materia medica.
A three-dimensional pharmacophore model of 3-hydro-3-methyl glutaryl coenzyme A (HMG-CoA) reductase inhibitors (RI)was developed based on 21 HMG-CoAreductase inhibitors froma rat liver. The selected training set had great diversity in both molecular structure and bioactivity as required by HypoGen program in the Catalyst software. The inhibitors in training set showed HMG-CoA RI inhibiting activity with IC50 values of 0.3-8000 nmol·L-1. The best statistical hypothesis, consisting of four features, one hydrogen-bond acceptor, one hydrogen-bond donor, one ring aromatic feature, and one hydrophobic point, had a correlation coefficient of 0.8883, a root-mean-square (RMS) deviation of 1.269, a Fixed cost of 88.75, a Total cost of 111.5, and a Configuration cost of 16.98, this hypothesis had highly predictive ability. The predictive ability was approved by the results of the activity estimated by mapping the compounds of the testing set with it. The cross-validation provided strong confidence on this hypothesis. This pharmacophore model can contribute to the finding and designing of new-type HMG-CoA reductase inhibitors, and to the development of traditional Chinese medicine and materia medica.
2008, 24(02): 307-312
doi: 10.3866/PKU.WHXB20080221
Abstract:
3D pharmacophore model was characterized using a training set of gpIIb/IIIa inhibitors which consisted of 20 3,4-dihydro-1(1H)-isoquinolinone-based anta nists by the Catalyst program. The best models (linear r=0.7715) were used as database search queries to identify active compounds for glycoprotein IIb/IIIa receptor from the Chinese herbal drugs database (CHDD) and eight active compounds were found by further activity-determined experiment. The validity of the pharmocophore model was proved further by the experimental results.
3D pharmacophore model was characterized using a training set of gpIIb/IIIa inhibitors which consisted of 20 3,4-dihydro-1(1H)-isoquinolinone-based anta nists by the Catalyst program. The best models (linear r=0.7715) were used as database search queries to identify active compounds for glycoprotein IIb/IIIa receptor from the Chinese herbal drugs database (CHDD) and eight active compounds were found by further activity-determined experiment. The validity of the pharmocophore model was proved further by the experimental results.
2008, 24(02): 313-316
doi: 10.3866/PKU.WHXB20080222
Abstract:
Details of the fabrication of an ultra thin porous alumina membrane (PAM) on silicon substrate with controllable height (thinner than 100 nm) by a two-step anodization of the aluminum deposited on the silicon substrate in oxalic acid solution were revealed. A formation mechanism of preferential anodizing of the remaining aluminum islands in the Al/Si interface was firstly proposed on the basis of the current-time curve. FE-SEM top view and cross section micrographs showed that the non-ordered surface layer formed in the first anodizing process was etched away, and in the second process the hexa nal ordered arrangement of pores existed in the local domain, suggesting that the ultra thin porous alumina membrane can be used as template for further fabricating nano-devices and nano-structures on silicon substrate.
Details of the fabrication of an ultra thin porous alumina membrane (PAM) on silicon substrate with controllable height (thinner than 100 nm) by a two-step anodization of the aluminum deposited on the silicon substrate in oxalic acid solution were revealed. A formation mechanism of preferential anodizing of the remaining aluminum islands in the Al/Si interface was firstly proposed on the basis of the current-time curve. FE-SEM top view and cross section micrographs showed that the non-ordered surface layer formed in the first anodizing process was etched away, and in the second process the hexa nal ordered arrangement of pores existed in the local domain, suggesting that the ultra thin porous alumina membrane can be used as template for further fabricating nano-devices and nano-structures on silicon substrate.
2008, 24(02): 317-322
doi: 10.3866/PKU.WHXB20080223
Abstract:
PtRu nanoparticles supported on the carbon, with different mean particle sizes, were synthesized by microwave-assisted ethylene glycol process, the effects of pH on the PtRu/C catalyst were mainly investigated. UV-Vis spectroscopy, energy dispersive X-ray analysis, transmission electron microscopy, and X-ray diffraction were applied to characterize the PtRu nanoparticles. The solution pH had important influence on the metal particle size. TEMresults indicated that the PtRu mean particle size decreased from 3.5 nm to 1.5 nm with the increase of pH value. However, when pH value reached 11.0, the metal loading of synthesized catalyst decreased distinctly because the metal nanoparticles were protected in solution. The results showed that the PtRu/C catalyst synthesized at pH ca 9.0, with appropriate particle sizes (2.4 nm) and homogenous dispersed particles, had the highest electrocatalytic activity for methanol electrooxidation among all the synthesized catalysts.
PtRu nanoparticles supported on the carbon, with different mean particle sizes, were synthesized by microwave-assisted ethylene glycol process, the effects of pH on the PtRu/C catalyst were mainly investigated. UV-Vis spectroscopy, energy dispersive X-ray analysis, transmission electron microscopy, and X-ray diffraction were applied to characterize the PtRu nanoparticles. The solution pH had important influence on the metal particle size. TEMresults indicated that the PtRu mean particle size decreased from 3.5 nm to 1.5 nm with the increase of pH value. However, when pH value reached 11.0, the metal loading of synthesized catalyst decreased distinctly because the metal nanoparticles were protected in solution. The results showed that the PtRu/C catalyst synthesized at pH ca 9.0, with appropriate particle sizes (2.4 nm) and homogenous dispersed particles, had the highest electrocatalytic activity for methanol electrooxidation among all the synthesized catalysts.
2008, 24(02): 323-327
doi: 10.3866/PKU.WHXB20080224
Abstract:
Electrocatalytic reduction of H2O2 on Pd nanoparticles in acidic medium was investigated by linear potential sweep method using an Au rotating disk electrode covered with Pd nanoparticles. The apparent activation energy for electroreduction of H2O2 on Pd nanoparticles was determined to be around 27.6 kJ·mol -1. The reaction proceeds via a two electron process. The type of anion of electrolytes significantly affected the catalytic behavior of Pd nanoparticles. A possible rate-determining step was proposed based on the dependence of kinetic current on the concentration of H2O2 and proton. The reaction mechanismwas briefly discussed.
Electrocatalytic reduction of H2O2 on Pd nanoparticles in acidic medium was investigated by linear potential sweep method using an Au rotating disk electrode covered with Pd nanoparticles. The apparent activation energy for electroreduction of H2O2 on Pd nanoparticles was determined to be around 27.6 kJ·mol -1. The reaction proceeds via a two electron process. The type of anion of electrolytes significantly affected the catalytic behavior of Pd nanoparticles. A possible rate-determining step was proposed based on the dependence of kinetic current on the concentration of H2O2 and proton. The reaction mechanismwas briefly discussed.
2008, 24(02): 328-332
doi: 10.3866/PKU.WHXB20080225
Abstract:
Using first-principles electronic structure and transport calculations the electronic structure and transport properties of single layer armchair graphene nanoribbons with zigzag edges and the effect of edge-vacancy defects were investigated. It was shown that perfect armchair graphene nanoribbons were metallic ribbons. Though the electronic band structure may be affected by the edge-vacancy defects, they remain the metallic characteristic.
Using first-principles electronic structure and transport calculations the electronic structure and transport properties of single layer armchair graphene nanoribbons with zigzag edges and the effect of edge-vacancy defects were investigated. It was shown that perfect armchair graphene nanoribbons were metallic ribbons. Though the electronic band structure may be affected by the edge-vacancy defects, they remain the metallic characteristic.
2008, 24(02): 333-337
doi: 10.3866/PKU.WHXB20080226
Abstract:
Phase equilibrium of quaternary system Cd2+, Na+//Cl-, SO2-4-H2O at 298 K was studied by isothermal method. The study showed that the quaternary system bearing Cd included Na2CdCl4·3H2O phase field, seven univariant curves, three co-saturation points and five crystal phase fields. The crystal fields of equilibrium solid phases were Na2SO4, CdSO4, CdCl2·2.5H2O, Na2CdCl4·3H2O and NaCl, respectively. The physico-chemical properties of solution in the quaternary system indicated regular change along with the increase of Cd2+ concentration. The results indicated that Cd salts possess quite high solubilities in the system studied, which means a strong transfer of Cd2+ and a high pollution risk of soil environment.
Phase equilibrium of quaternary system Cd2+, Na+//Cl-, SO2-4-H2O at 298 K was studied by isothermal method. The study showed that the quaternary system bearing Cd included Na2CdCl4·3H2O phase field, seven univariant curves, three co-saturation points and five crystal phase fields. The crystal fields of equilibrium solid phases were Na2SO4, CdSO4, CdCl2·2.5H2O, Na2CdCl4·3H2O and NaCl, respectively. The physico-chemical properties of solution in the quaternary system indicated regular change along with the increase of Cd2+ concentration. The results indicated that Cd salts possess quite high solubilities in the system studied, which means a strong transfer of Cd2+ and a high pollution risk of soil environment.
2008, 24(02): 338-344
doi: 10.3866/PKU.WHXB20080227
Abstract:
Two pyrazolone compounds, POTAS and PDTAS, were synthesized and their inhibition action and adsorption behavior on copper in aqueous NaHCO3 (mass fraction 5%) solution were investigated by means of mass loss and electrochemical techniques. It was showed that the two compounds had od corrosion inhibition for copper in NaHCO3 solution. The inhibition efficiency of the two compounds was found to decrease as follows: POTAS>PDTAS. Both POTAS and PDTAS were mixed-type inhibitors. The results of experiment revealed that the adsorption on copper surface was monolayer adsorption. The adsorption processes were exothermic reaction and belong to physical absorption.
Two pyrazolone compounds, POTAS and PDTAS, were synthesized and their inhibition action and adsorption behavior on copper in aqueous NaHCO3 (mass fraction 5%) solution were investigated by means of mass loss and electrochemical techniques. It was showed that the two compounds had od corrosion inhibition for copper in NaHCO3 solution. The inhibition efficiency of the two compounds was found to decrease as follows: POTAS>PDTAS. Both POTAS and PDTAS were mixed-type inhibitors. The results of experiment revealed that the adsorption on copper surface was monolayer adsorption. The adsorption processes were exothermic reaction and belong to physical absorption.
2008, 24(02): 345-349
doi: 10.3866/PKU.WHXB20080228
Abstract:
Aucore@Ptshell nanoparticleswere synthesizedby chemical reductionmethod. The sampleswere characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). In-situ surfac-enhanced Raman scattering (in-situ SERS) spectroscopy combined with cyclic voltammetry was utilized to investigate the electro-oxidation behavior of formic acid adsorbed on Aucore@Ptshell nanoparticles coated on platinum electrode, and SERS spectra with high quality were acquired. Results showed that the intermediates COad and HCOOad, the dissociated products of HCOOH, were produced at open circuit potential. As the potential moved to positive, the first oxidation wave for CO2 was observed at +0.10 V. The study demonstrated that the electrode prepared by Aucore@Ptshell nanoparticles coated on platinum substrate exhibited od electro-catalytic properties and SERS activity for the oxidation of HCOOH, and the electro-oxidation proceeds of formic acid via“dual path”mechanism.
Aucore@Ptshell nanoparticleswere synthesizedby chemical reductionmethod. The sampleswere characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). In-situ surfac-enhanced Raman scattering (in-situ SERS) spectroscopy combined with cyclic voltammetry was utilized to investigate the electro-oxidation behavior of formic acid adsorbed on Aucore@Ptshell nanoparticles coated on platinum electrode, and SERS spectra with high quality were acquired. Results showed that the intermediates COad and HCOOad, the dissociated products of HCOOH, were produced at open circuit potential. As the potential moved to positive, the first oxidation wave for CO2 was observed at +0.10 V. The study demonstrated that the electrode prepared by Aucore@Ptshell nanoparticles coated on platinum substrate exhibited od electro-catalytic properties and SERS activity for the oxidation of HCOOH, and the electro-oxidation proceeds of formic acid via“dual path”mechanism.
2008, 24(02): 350-354
doi: 10.3866/PKU.WHXB20080229
Abstract:
An amphiphilic graft copolymer PAA-g-C8PhEO10Ac with poly(acrylic acid) as a main chain and octylphenyl polyoxylethylene ether(C8PhEO10) as graft chains was synthesized via free radical copolymerization of acrylic acid (AA) and amphiphilic C8PhEO10Ac maromonomers. The number average molecular weight of the copolymer was determined to be 4.37×104 by gel permeation chromatography(GPC). The structure and composition of the copolymer obtained were characterized by FTIR and 1H-NMR. The molar ratio of acrylic acid monomer to macromonomer is 9:1 in the copolymer and 32 C8PhEO10 branch chains attach to a poly(acrylic acid) backbone. Self-assembly behavior of PAA-g-C8PhEO10Ac in aqueous solution was preliminary studied by means of surface tension measurements, fluorescent probe and TEM. It was found that spherical micelles are formed in water phase at cmc1 and cmc2. As compared with those at cmc1, the surface tension of the copolymer solution and the polarity in the micellar core further decrease at cmc2. Furthermore the diameter of the micelles increases and the micelles become compact. The presence of 1.0%(w) sodium chloride results in the lower surface tension of the copolymer solution and the weaker polarity in micellar core.
An amphiphilic graft copolymer PAA-g-C8PhEO10Ac with poly(acrylic acid) as a main chain and octylphenyl polyoxylethylene ether(C8PhEO10) as graft chains was synthesized via free radical copolymerization of acrylic acid (AA) and amphiphilic C8PhEO10Ac maromonomers. The number average molecular weight of the copolymer was determined to be 4.37×104 by gel permeation chromatography(GPC). The structure and composition of the copolymer obtained were characterized by FTIR and 1H-NMR. The molar ratio of acrylic acid monomer to macromonomer is 9:1 in the copolymer and 32 C8PhEO10 branch chains attach to a poly(acrylic acid) backbone. Self-assembly behavior of PAA-g-C8PhEO10Ac in aqueous solution was preliminary studied by means of surface tension measurements, fluorescent probe and TEM. It was found that spherical micelles are formed in water phase at cmc1 and cmc2. As compared with those at cmc1, the surface tension of the copolymer solution and the polarity in the micellar core further decrease at cmc2. Furthermore the diameter of the micelles increases and the micelles become compact. The presence of 1.0%(w) sodium chloride results in the lower surface tension of the copolymer solution and the weaker polarity in micellar core.
2008, 24(02): 355-358
doi: 10.3866/PKU.WHXB20080230
Abstract:
Rare earth metal seed Tb was employed for the growth of GaNnanorods. GaNnanorods were synthesized successfully through ammoniating Ga2O3/Tb films sputtered on Si(111) substrates. X-ray diffraction results indicated that the nanorods were hexa nal GaN. Observations using scanning electron microscopy and high-resolution transmission electron microscopy showed that GaN was of single-crystal nanorod structure, with diameter 50-150 nm and length about 10 μm. Photoluminescence spectrum showed a strong UV emission peak at 368.6 nm, indicating that the products possess od luminescent characteristics. The growth mechanismof GaN nanorods was also discussed.
Rare earth metal seed Tb was employed for the growth of GaNnanorods. GaNnanorods were synthesized successfully through ammoniating Ga2O3/Tb films sputtered on Si(111) substrates. X-ray diffraction results indicated that the nanorods were hexa nal GaN. Observations using scanning electron microscopy and high-resolution transmission electron microscopy showed that GaN was of single-crystal nanorod structure, with diameter 50-150 nm and length about 10 μm. Photoluminescence spectrum showed a strong UV emission peak at 368.6 nm, indicating that the products possess od luminescent characteristics. The growth mechanismof GaN nanorods was also discussed.
