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2007 Volume 23 Issue 7
Two amino acid-based Gemini surfactants derived fromcystine, sodium N,N’-di(4-n-butyloxycinnamoly)-L-cystine (SDBCC) and sodium N,N’-didecamino L-cystine (SDDC), were synthesized. Their surface activity and aggregation properties were also investigated by equilibrium surface tension measurements, dynamic light scattering (DLS), and transmission electron microscopy (TEM).
Three-dimensional porous Cu6Sn5 alloy electrodes were prepared by electroplating using copper foam as current collector. The micro-holes and small islands on surface of the Cu6Sn5 alloy increased largely the surface area of the electrode, and improved significantly the ability of the electrode in buffering the volume change in process of charge/discharge when the Cu6Sn5 alloy was employed as anode in a lithium-ion battery. Galvonostatic charging/discharging results demonstrated that the initial discharge (lithiation) and charge (delithiation) specific capacities of the Cu6Sn5 alloy electrode were 620 mAh·g-1 and 560 mAh·g-1, respectively. It demonstrated that the Cu6Sn5 alloy electrode exhibited a large initial coulomb efficiency (90.3%) and od capacity retention. SEM (scanning electron microscope) results illustrated that the Cu6Sn5 alloy deposited on copper foam substrate was more stable than that on a conventional copper substrate, and displayed no obvious exfoliation after 50 charge/discharge cycles.
Using Au(S2O3)3-2 as the ld precursor, Au/TiO2 photocatalysts were prepared by water washing (W) and rotary evaporation (E) processes, respectively. The samples were characterized by UV-Vis diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic absorption flame emission spectroscopy (AAS). The photocatalytic activity of the samples was evaluated from the analysis of the photodegradation of methyl orange. Using the water washing treatment, well dispersed ld nanoparticles with the diameter of 2 -5 nm were formed on the surface of TiO2, whereas only the ld coating was formed for rotary evaporation processes. The photocatalytic activity of Au/TiO2 photocatalysts is related to the preparation process. With a similar ld loading, the photocatalysts prepared by water washing showed higher photocatalytic activity compared to the catalysts prepared by rotary evaporation.
A molecular dynamics simulation was applied on a eutectic system (LiTFSI:urea) at a molar ratio of 1:3.6 at 25 ℃ and 50 ℃ to obtain the structural and dynamical properties. The results showed that there was almost no difference in structural properties at the above two simulation temperatures. The coordination number of the Li+ was about 5 and mainly coordinated by carbonyl oxygen atoms from urea and oxygen atoms from TFSI- anions. Also in the solvation shell of Li+, each TFSI- anion provided only one oxygen atom out of four to coordinate with Li+, and the TFSI- anions have trans, cis, and gauche configurations. The ratio of different configurations will change with temperature.
The microcalorimetric method was used to study the antibacterial activity on the bacteria’s multiplying metabolismand the non multiplying metabolism. The metabolismthermogenic curves of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), under the action of the synthesized Schiff base and its 3d, 4f complexes (2L, 2LZnYb), were obtained. The results showed that the multiplying metabolism and the non multiplying metabolism of bacteria could be analyzed by the thermogenic curves using the thermokinetic equations. On the multiplying metabolism, the two compounds (ZL, 2LZnYb) have strong activity for E. coli. (IC50 (half-inhibitory concentration) is 6.1 and 5.1 mg·L-1, respectively) and weak activity for S. aureus (IC50 is 310.1 and 595.9 mg·L-1, respectively). The introduction of Zn and Yb with the compound slightly increased the inhibition on the multiplying metabolism of E. coli but greatly decreased the effect on that of S. aureus. The activity of these two compounds showed great difference on the non multiplying metabolism. Regardless of E. coli or S. aureus, 2L just showed a notable inhibition and MSC50 (the minimum stationary-cidal concentration 50) of 2L was 6.4 and 209.7 mg·L-1 for the two microorganisms, respectively. Thus, 2L may become a novel kind of potential antibacterial candidate.
Pd nanoparticles were supported on different types of carbon materials including multiwalled carbon nanotubes (MWCNT) and carbon black prepared by the intermittent microwave heating (IMH) technique. The morphologies and electrochemical properties of the electrocatalysts were characterized. TEMand XRD measurements revealed that the Pd nanoparticles were uniformly dispersed on MWCNT with an average particle size of 4 nm. The cyclic voltammetric, chronopotentiometric, and electrochemical impedance spectroscopic (EIS) experiments indicated that Pd/MWCNT electrocatalyst showed a better performance for methanol oxidation than that of Pt/C in alkaline media. A negative shift over 100 mV of the onset potential for methanol oxidation was found on Pd/MWCNT compared to that on Pt/C. The results indicated that the enhancement in the activity for methanol oxidation on Pd/MWCNT was due to not only the increase in the active surface area but also the synergistic interaction between Pd and MWCNT.
The oxygen poisoning mechanism of the catalytic hydrolysis of carbonyl sulfide (OCS) over alumina at room temperature was investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS), XRD, BET, and ion chromatograph (IC). The surface hydroxyl (—OH) species triggered the catalytic hydrolysis of OCS on Al2O3, with the formation of surface hydrogen thiocarbonate (HSCO-2) species as a key intermediate. Surface SO2-4 was identified with in situ DRIFTS and IC. It was found that the accumulation of sulfate on catalyst led to the poisoning of Al2O3 in the presence of oxygen.
Pure and Ag-doped TiO2 powders were prepared by sol-gel method. The crystal structure, particle size and surface properties of the samples were characterized by means of X-ray diffraction(XRD), transmissionelectron microscopy(TEM) and Brunaner-Emmett-Teller(BET) surface areas. The results revealed that the Ag dopant increased the specific surface area of TiO2 powders. The sensitive properties of the samples were also investigated. It was found that the doped sensor had a better sensitivity and higher selectivity to HCHO than the pure one. The sensitivity of the sensor , which was prepared with 5% Ag-doped TiO2 calcined at 500 ℃, was the highest. With the optimum working current of 124 mA, the sensitivity of the sensor was approximate to 4 at its detection limit of 10 μL·L-1, its recovery time was 9 s whereas response time was no more than 1 s.
Densities (ρ) and refractive indices (nD) of glycine (Gly), DL-alanine (Ala), DL-valine (Val) (0.02, 0.04, 0.06, 0.08, and 0.10 mol·L-1) in 0.005 and 0.008 mol·L-1 aqueous cetyltrimethylammoniumbromide (CTAB) have been measured at 298.15, 303.15, 308.15, and 313.15 K. The density data have been utilized to calculate apparent molar volumes (φv), partial molar volumes (φ0v), at infinite dilution and partial molar volumes of transfer φ0v(tr) of amino acids. The refractive index data have been used to calculate molar refractivity (RD) of amino acids in aqueous cetyltrimethylammonium bromide. It has been observed that φ0v varies linearly with increasing number of carbon atoms in the alkyl chain of amino acids, and hence, was split to get contributions from the zwitterionic end groups (NH+3, COO-) and methylene group (CH2) of the amino acids. The behaviour of these parameters has been used to investigate the solute-solute, solute-solvent interactions and the effect of cetyltrimethylammoniumcation on these interactions.
The kinetics and mechanismof lactic acid oxidation in the presence of Mn(II) and Ce(IV) ions by chromic acid were studied spectrophotometrically. The oxidation of lactic acid by Cr(VI) was found to proceed in two measurable steps, both of which gave pyruvic acid as the primary product in the absence of Mn(II). 2Cr(VI)+2CH3CHOHCOOH→2CH3COCOOH+Cr(V)+Cr(III) Cr(V)+CH3CHOHCOOH→Cr(III)+CH3COCOOH The observed kinetics was explained due to the catalytic and inhibitory effects of Mn(II) and Ce(IV) on the lactic acid oxidation by Cr(VI). The reactivity of lactic acid depends upon the experimental conditions. It acts as a two-or three-equivalent reducing agent in the absence or presence of Mn(II). It was examined that Cr(III) products resulting from the direct reduction of Cr(VI) by three-equivalent reducing agents. The oxidation of lactic acid follows the complex order kinetics with respect to [lactic acid]. The activation parameters Ea, △H#, and △S# were calculated and discussed.
The hydrogen bonding interactions between ureas or thioureas and different carbonyl compounds were studied using the Moller-Plesset perturbation theory (MP2) method. The natural bond orbital analysis further disclosed the essence of the hydrogen bonding interaction. In addition, the substituent effects were investigated and the results indicated that both the electron-withdrawing groups on ureas (thioureas) and electron-donating groups on carbonyl compounds can facilitate the hydrogen bonding formation. Two possible hydrogen bonding complex conformations, cis and trans, were discussed and the energy gaps between themwere analyzed, in combination with the catalytic reactions.
A study on thermal denaturation of hen egg-white lysozyme (HEWL) was carried out by differential scanning calorimetry (DSC) and modulated temperature differential scanning calorimetry (MDSC). It was found that DSCprofiles ofHEWLwere dependent on heating rates and concentrations of enzyme as well as cosolvent. The enthalpy of denaturation (△Hm) increasedwith increasing enzyme concentration in aqueous solution. In aqueous solution containing dimethylsolfoxide (DMSO), denaturation temperature (Tm) shifted toward lower temperature, and the transition peak became shallower and broader with increasing volume proportion of DMSO. When the content of DMSO was more than 70%, only a declining smooth line could be observed instead of a single endothermic transition curve. Interestingly, fromMDSC curves of HEWL in aqueous solution without DMSO, a small and symmetrical peak in front of the main transition (I) was observed marginally, which was regarded as a pre-transition (II). Specially, this small and marginal peak could not be found in aqueous solution containing DMSO. In addition, with increasing amount of protein, Tm(II) shifted toward lower temperature, and △Hm(II) decreased along with the temperature gap between two transitions lengthened. The results were considered to be due to the reversible dissociation of HEWL dimers in aqueous solution.
Nanocrystalline TiO2 was synthesized by the low-temperature hydrothermal method using ionic liquid (1-ethyl-3-methyl-imidazole acetate)-water mixture as solvent; various studies such as X-ray diffraction, Brunauer-Emmett-Teller surface area, X-ray photoelectron spectra, UV-Vis spectroscopy were conducted. The products prepared from ionic liquid-water mixture possessed od anatase crystallinity and contained less brookite phase than that from pure water. The photocatalytic degradation of methyl orange in water was studied in photoreactor with UV lamp as light source. The product prepared from ionic liquid-water solvent for 24 h showed superior photocatalytic activity for the degradation of methyl orange compared to commercial TiO2, Degussa P25. The higher photocatalytic activity was attributed to the crystal phase, grain size, and specific surface area of the catalyst. Further, the effects of the catalyst amount and pH value of solution on the photocatalytic activity of the product were also investigated.
TiO2 doped with iron (Fe-TiO2) thin films were synthesized using sol-gel method. TiO2 codoped with iron and nitrogen (Fe/N-TiO2) thin films were prepared by calcining Fe-TiO2 thin films in ammonia atmosphere. The influence of iron and nitrogen doping concentration, heat-treatment temperature and film thickness on the hydrophilicity of the films were studied by XRD, XPS, SEM, UV-Vis spectra and measured water contact angle. The results indicated that Fe/N-TiO2 (0.5%Fe,molar percent) films were optimumin hydrophilicity, especially under visible-light irradiation. Doping iron mostly reduced the recombination of electrons and holes, and doping nitrogen in TiO2 enhances photoresponse in visible-light region. The hydrophilicity benefited fromboth effects.
Copper-based catalysts for methanol synthesis were prepared by glow discharge plasma. These catalysts were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area measurement (BET method), hydrogen temperature programmed desorption (H2-TPD), and carbon monoxide temperature programmed desorption (CO-TPD). The catalytic performances of these samples were measured in methanol synthesis from the hydrogenation of carbon monoxide. After plasma enhancement in N2 and then in H2, the conversion of carbon monoxide was 2.61 times higher than that of the conventional sample. Meanwhile, the space time yield (STY) of methanol was 2.65 times higher, and the amount of surface active sites on the catalysts increased as evidenced by TPD experiments.
Asymmetric Gemini surfactants CmH2m+1OCH2CH(OH)CH2N+(CH3)2C8H17Br, referred to as CmOhpNC8 (m=10, 12 and 14), were synthesized. This type of surfactant molecule has a head region (a hydroxyl and a quaternary ammonium linked by one methylene group) with a small size and two alkyl chains with different lengths. The maximum bubble pressure technique was used to investigate the adsorption kinetics of CmOhpNC8 aqueous solution below their critical micelle concentrations at the air/water interface. The results showed an obvious kinetic process for the adsorption of CmOhpNC8. When CmOhpNC8 were adsorbed on the freshly formed interface, the adsorption process was pure diffusion controlled.When some molecules existed at the interface, the adsorption barrier (Ea) appeared, which reduced with increasing m. This indicated that those molecules with long alkyl chain migrated more easily from the subsurface into the surface, which was attributed to enhanced hydrophobic interaction between the alkyl chains with
increasing m.
The IR spectroscopic and electrochemical measurements demonstrated that glucose oxidase ( x) could be immobilized on the surface of carbon black (CB) using a simple adsorptionmethod. The electrochemical measurements indicated that x immobilized on CB could under the quasi-reversible and direct electrochemical reaction and keep the bioelectrocatalytic activity for the glucose oxidation. Even after conservation for two weeks, its electrocatalytic activity decreased only 5%, illustrating the od stability of x immobilized on CB.
A three-dimensional pharmacophore model was generated for aldose reductase (ALR2) inhibitors with flavonoid skeleton, using the software Catalyst. Specially customized features of hydrogen-bond acceptor and donor were used in this study, which perform better than the default features of Catalyst. The hypothesis model was scored based on the cost of the hypothesis from the null hypothesis. The final selected pharmacophore model had three features; one hydrogen bond acceptor and two donors. Six flavonoid compounds were used to dock into ALR2 active site, using InsightII/Affinity. Comparison between the pharmacophore model and the docking results suggested that the C7 and C4’ hydroxyls on the flavone skeleton were key functional groups influencing ALR2 inhibotory activity, and TYR48, VAL47, GLN49, HIS110, and TRP111 at the active site of ALR2 were the key residues for the binding.
A sandwich-type Si/Fe/Si film was deposited on Cu foil by magnetron sputtering. High-resolution transmission electron microscope (HRTEM) and selected area electron diffraction (SAED) results indicated that the sputtered film had an amorphous structure. The cross-sectional scanning electron microscope (SEM) images and the energy dispersive X-ray spectrometry (EDXS) spectra showed that the thickness of the filmwas 3.2 μm, and its volume expansion ratio was up to 265% after the prolonged electrochemical lithiation and delithiation cycles. In the potential range 1.5-0.005 V (vs Li+/Li) at the current density of 0.1 mA·cm-2, the film anode exhibited a high initial lithiation capacity around 1.85 mAh·cm-2, and reached the highest reversible delithiation capacity of 0.84 mAh·cm-2 after 70 cycles. After 200 cycles, it still retained a reversible capacity of 0.55 mAh·cm-2, which was 66%of the highest reversible capacity. The introduction of Fe to Si not only improved the conductivity of the film, which partially reduced the voltage hysteresis, but also effectively suppressed the volume expansion, which led to a prolonged cycle life.
The freezing behavior of Al nanowires at different cooling rates was studied by using the classic molecular dynamics simulation via embedded atom method (EAM) potentials. In order to distinguish the evolution of the local clusters in the cooling process of Al nanowires with different cooling rates, pair analysis technique was employed. The simulation results indicated that the microstructure of the nanowires changed from amorphous to helical multi-shelled structure with the decrease of cooling rate. The helical multi-shelled structure owed some features of amorphous structure, but it was more stable than the later. Moreover, even if the cooling rate decreased to 1×109 K·s-1, Al nanowires still kept the helical multi-shelled structure.
Based on effective core potential of Cu atom, the LANL2DZ basis set for Cu atom and the 6-311+(d) basis set for C and N atoms were used. At the same time, the necessary modification was made for the section of p orbit function of valence electrons basis set of Cu atom. The energies, equilibrium structure , and harmonic frequency of the ground state of CuC and CuNmolecules were calculated using density functional theory (B3LYP) method. Based on the theory of atomic and molecular statics, the reasonable dissociation limit and dissociation energy for the ground state of CuC and CuN molecules were derived. The potential energy curve scan for the ground state of CuC and CuN molecules was carried out with density function theory (B3LYP) method. Murrell-Sorbie analytical potential energy function and its Dunham expansion around equilibrium position were also derived with nonlinear least-square fit. At the same time, the spectroscopic constants for the ground state of CuC and CuN molecules were calculated following the formula of Herzberg and Dunham.
On the basis of experimental data, double-Langmuir (DL) model was used to investigate the adsorption and separation of hydrogen and carbon dioxide in activated mesocarbon microbeads with high specific surface. Pure and binary adsorption isotherms of carbon dioxide and hydrogen (mole ratio is 1:9) in activated mesocarbon microbeads were measured using the high-precision intelligent gravimetric analyzer at temperature of 298, 273 and 268 K, and the pressure ranging from 0 to 1.8 MPa. In order to get adsorption amount of the single component of mixture gas, the DL model and the ideal adsorbed solution theory (IAST) were combined. The combined method can be applied to carbon dioxide and hydrogen binary systems perfectly. The calculated results indicated that the selectivity of carbon dioxide can reach 73.4 at 268 K and 1.7 MPa, which suggests that the activated mesocarbon microbead was an excellent candidate for the removal of carbon dioxide in hydrogen/carbon dioxide mixtures.
Highly ordered mesoporous carbon, denoted as CMK-5, was synthesized by using mesoporous silicates SBA-15 as template and furfuryl alcohol as carbon precursor. Carbon supported platinum nanoparticles were prepared by a microwave-irradiated polyol process. In order to improve the dispersity of Pt nanoparticles, cationic surfactant (CTAB) as stabilizer was added to the microwave heating process. X-ray diffraction (XRD) and transmission electron microscopy (TEM) images showed that the dispersity of Pt nanoparticles was improved and the particle size of the catalyst was decreased to 2.9 nm with addition of cationic surfactant (CTAB). Cyclic voltammograms showed that the CTAB-stabilized Pt/CMK-5 catalyst exhibited a higher catalytic activity than the catalyst without CTAB or the commercial JMPt/C catalyst.
Crystalline Cu0.04V2O5 was prepared by precipitation method followed by heat treatment at 300 and 600 ℃. The material prepared at 300 ℃ showed porous morphology, whereas that prepared at 600 ℃ was highly crystalline. X-ray diffraction showed both materials exhibiting the same orthorhombic structure as that of V2O5. Fourier transform infrared spectroscopy confirmed the existence of ca 0.18 mol of absorbed water in one mol of the material prepared at 300 ℃electrochemical performance of V2O5. The material prepared at 600 ℃ had a reversible discharge capacity over 160 mAh·g-1 after 60 cycles at the current density of C/5.6. The material prepared at 300 ℃ showed od cycling performance at higher current densities, with a reversible capacity ca 100 mAh·g-1 when cycled at C/1.9. The discrepancy in the rate performance of Cu0.04V2O5 was attributed to the morphology of materials.
The thermal decomposition processes of ZnSn(OH)6 were studied using TG/DTG at various heating rates of 2.5, 5.0, 10.0, 15.0, 20.0 K·min -1. The results showed that the decomposition proceeded through one step in nitrogen atmosphere at the temperature range from 298 to 873 K. A od agreement was found between the mass loss of the thermal decomposition of ZnSn(OH)6 and the theoretical mass loss. The thermal decomposition kinetics was investigated employing non-isothermal multiple scanning method. The activation energy for the decomposition reaction of ZnSn(OH)6 was determined to be E=128.77 kJ·mol-1 in nitrogen atmosphere and the pre-exponential factor of its kinetics equations was calculated to be lg(A/s-1)=10.61. The mechanism function was obtained to be Mample Power theorem.
Using the density functional theory (DFT), the reaction of chlorine trifluoride with water of different proportion was studied. At B3pw91/6-31++G(d,p) level with DFT method, the geometries of all species(reactants, transition states and products) were optimized and the vibration frequencies and zero point vibration energies (ZPVE) were also calculated. All the energies of the species were obtained with the correction of ZPVE. The results of the calculations showed that the energy barriers of the reaction of chlorine trifluoride and water were very low; plenty water was in favor of HClO2, insufficient water was in favor of other haloid oxide.
Based on thermodynamical and kinetic theories, the mechanism of synthesizing ultra-fine diamond in graphite suspension by ms-pulsed laser irradiation was analyzed. Diamonds were nucleated by condensation in the carbon vapor plume formed when ms-pulsed laser irradiated on the graphite particles. Compared to ns-pulsed laser, ms-pulsed laser with a lower laser energy density and a longer pulse width provided a smaller degree of supercooling for the growth of diamond nucleus, allowed rather low growth velocity for diamond nucleus. On the other hand, sp2 hybridization on diamond surface could reduce the surface energy of diamond nucleus and make them more stable. However, the formation of sp2 hybridized structure retarded the epitaxy growth of the nanodiamonds, thus preventing the formation of large grains. Above two factors could determine the formation of ultra-fine nanodiamonds during the synthesis process by the irradiation of ms-pulsed laser. Our results suggested that the growth of nanodiamonds follows Wilson-Frenkel law, and ms-pulsed laser with lower energy density was propitious for producing fine nanodiamonds.
The co-adsorption of CO2 and HCOO on Cu(100) surface was studied by the first-principle DFT-GGA calculations. The calculated stabilization energy of CO2 by co-adsorbed HCOO was -11.10 kJ·mol-1, which was quite close to the experimental TPD result. The main contribution to the stabilization energy of CO2 came from the strong induced effect of HCOO on the adjacent adsorbed CO2 which increased the interaction of“dipolar CO2”with the Cu (100). Moreover, the co-adsorbed HCOO broke the linear symmetry of adsorbed CO2 due to its induced effect and thus enhanced the reaction rate of formate synthesis fromCO2/H2 gas feed.
An approach was developed to investigate hole oxidation on TiO2 films in aqueous solutions by using octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs) as a probe, in which the adsorption and surface diffusion of the reactants were exculded. Under UV irradiation, the water contact angle of the OTS SAMs on TiO2 films in water decreased obviously. In the presence of hole scavengers, the decrease of water contact angle for the OTS SAMs on TiO2 films with UV irradiation was inhibited apparently, while the effect of·OH radical scavengers and fluoride on the decrease of water contact angle was very small. It indicated that direct hole oxidation played a major role in photocatalytic removal of alkyl chains on TiO2 films in aqueous solutions.
LiFePO4/C composite cathode materials were synthesized by carbothermal reduction (CTR) method using FePO4 as precursor. The precursors and the products were characterized by TG-DTA, FTIR, XRD, and the reaction mechanism was investigated. The compositions and electrochemical performance of the products at different calcination temperatures were studied. The results showed that LiFePO4 in the sample prepared at 300 ℃ was primary phase, so the crystallization temperature in this route was lower than that of other methods. At 300, 400, 500 ℃, Li3PO4 and Fe2O3 as impurity phases existed in the samples and the higher temperature led to less impurity phases. The sample calcined at 600 ℃ had no impurity, but Li4P2O7 appeared at 700 ℃. The sample prepared at 600 ℃ for 24 h had the best electrochemical performance, which could deliver a discharge capacity of 146 mAh·g-1 at 0.1C and retain a discharge capacity of 141 mAh·g-1 after 15 cycles.
ZnWO4 nanorods were prepared via a hydrothermal route, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The morphology of ZnWO4 nanocrystals were found to depend on the reaction time and pH. Luminescent properties of ZnWO4 nanocrystals were investigated by photoluminescence (PL) spectroscopy.
Laser flash photolysis technique was employed to characterize the triplet excited state behavior of C60-dexamethasone (C60-DE) in benzene. The time-resolved triplet-triplet (T-T) difference absorption spectrum of 3C60-DE* with optical excitation (355 nm laser pulse) was recorded. The spectrum of 3C60-DE* exhibited maxima at 700, 440, 350, and 310 nm. The bleaching maximum observed at 330 nm coincides well with the ground-state maximum in this region. 3C60-DE* could be quenched by oxygen. Compared with 3C60*, the T-T annihilation rate constant of 3C60-DE* deduced ((5.03±1.31)×109 L·mol-1·s-1 for 3C60* and (3.53±0.87)×109 L·mol-1·s-1 for 3C60-DE*), and the life time of 3C60-DE*increased ((12.0±2.6) μs for 3C60*, (18.0±3.3) μs for 3C60-DE*). The reason may be that the connection of dexamethasone decreased the colliding probability of the C60 ball.
Dihydrogen-bonded complexes formed from pyrrole and a series of small molecules were studied at density functional B3LYP/6-311++G(d, p) level of theory. The topological characters of the electron density and atomic integral characters of the dihydrogen-bonded complexes were investigated extensively. Especially, the changes of atomic net charge, dipole moment, energy and volume of both the proton-donors and acceptors in the forming process of dihydrogen-bond were discussed.
A series of composite alkaline polymer electrolyte membranes composed of poly(vinyl alcohol) (PVA), potassiumhydroxide (KOH), bentonite, and water were prepared by a solution casting method. The composite alkaline polymer electrolytes of PVA-bentonite-KOH-H2O were characterized by XRD, SEM, and CV technologies. The influence of bentonite on electrical conductivity of the composite membrane was studied. The results indicated that the bentonite had dual effects on the conductivity of the composite membrane; on one hand, it could decrease the conductivity of composite membrane by blocking the ion transfer tunnel in the PVA polymer structure, on the other hand, it improved the conductivity by increasing the KOH content in the composite electrolyte and forming a highly conductive defective layer on PVA-bentonite phase interface. However, in the system, when the water mass fraction was relative lower, the conductivity of the composite electrolyte system had a maximun value, while at a more higher water content w(H2O)=65%, the conductivity of the systemincreased linearly. The highest electrical conductivity reached 0.110 S·cm-1 at roomtemperature. XRD patterns revealed the amorphous structure of PVA in the composite membrane with appropriate mass ratio; SEM test confirmed that the bentonite-blending composite membrane contained a lot of micro-tunnels; cyclic voltammetry measurement demonstrated that composite alkaline polymer electrolyte membrane had a wide electrochemical stable window (about 2.0 V).
