2005 Vol. 18, No. 5

Review
Till now, theoretical research has focused on some chemical behaviors, structural properties of bio-macromolecules in solutions. When the molecular force field was used to treat solution systems, not considering the movement of electrons, in many force fields the chemical bonds between atoms must be confirmed to make sure that they can’t be destroyed or formed in modeling procedure. Using quantum chemical calculation based on B-O approximation to treat solution systems, because it can consume much more resources, this method can’t treat large systems, which restricts the application of quantum chemical calculations. Moreover the hybrid QM/MM method has been widely used in research of chemical reaction in condense phase and biologic macromolecules especially the mechanisms of enzyme catalysis reactions, which has developed rapidly and takes advantage of the accuracy of QM method and high efficiency of MM method. This article will describe a brief introduction of the principle and development history of QM/MM method and give some application introductions.
Letter
The convalently linked porphyrin-fullerene ligand was synthesized by 1,3 dipolar cycloaddition reaction. The ligand and complexes were characterized by means of FT-IR, Uv-Vis, 1HNMR, ESI-MS and elemental analysis. The photoelectricity transform performance of the compounds was studied.The result indicated that the photovoltaic effect of (n+n) heterojunction electrode formed by MP-C60/GaAs was super, especially in the I2/I3- and O2/H2O redox couples, and photovoltaic potential was preferable. The photovoltaic performance of a MP-C60/GaAs electrode at 1-2 μm thinck MP-C60 film of appeared peak value.
Article
The Cavity enhanced absorption spectroscopy based on a tunable DFB diode laser (TDL-CEAS) was described. A brief introduction of cavity enhanced absorption spectroscopy development and experimental scheme was given, the effective absorption path of the medium in the optical cavity was interpreted from the way of FabryPerot cavity. It is pointed out that the main reason why CEAS has high detection sensitivity is that the medium in the cavity can get a long absorption path. A tunable DFB diode laser which center wavelength is 1.573 μm was used as the light source, and an optical cavity which consists of two high reflectivity mirrors (near 1.573 μm, R about 0.994) separated at a distance of 34 cm was used as the absorption cell. Laser radiation was coupled into the optical cavity via accidental coincidences of laser frequency with the cavity mode when scanning the cavity and the laser. An absorption spectrum of carbon dioxide near 1.573 μm was obtained and a detection sensitivity of about 1.66×10-5 cm-1 was achieved. It is experimentally demonstrated that the CEAS is a highly sensitive and high resolution spectrum technology, and it has the advantage of simple experimental setup and easy operation.
The electron momentum profile for inner valence orbitals 2b and 3a of cyclohexene (C6H10) was firstly studied by the binary (e,2e) electron momentum spectroscopy (EMS), at the impact energy of 1200 eV plus binding energy using symmetric non-coplanar kinematics. The complete valence shell binding energy spectrum of C6H10 was also obtained. The experimental momentum profile of the summed orbitals was compared with Hartree Fock (HF) and density functional theory (DFT) methods with various basis sets. The experimental measurement was well described by the HF and DFT calculations except for the low-p region (p<0.25 a.u.). Experimental small “turn-up” effects of momentum profile in the low-p region could be due to the distorted wave effects.
On the flowing afterglow apparatus, in the energy transfer reaction between Ar (3P0,2) and SO2, two series of spectra were observed at two different downstream optical windows from the discharge region. According to the data obtained in this group’s report on the discharge of the mixture of Ar with SO2 and spectral simulation, the two spectrum progressions in the range of 320 and 600 nm were assigned to SO (A″3Σ+→X 3Σ-) and SO (c 1Σ-→X 3Σ-), respectively. The spectroscopic constants for the new electronic state were obtained by spectral simulation based on the method of the least square and shown as follows: T00 =(30460±18.0) cm-1, ωe′=(685±0.8) cm-1 and ωe′χe′=(7.7±8.0) cm-1.
The modified discrete variable representation for three-dimension (DVR3D) method was applied to the determination of the vibrational energy levels of the fundamental electronic state of H2S and H2O. The Hamiltonian was expressed in Jacobi coordinates and developed on a DVR basis for each internal coordinate. The angular coordinate used a DVR based on Legendre polynomials and the radial coordinates utilized a DVR based on sine basis functions. Successive diagonalization and truncation technique was used to reduce the size of the final Hamiltonian matrix to be diagonalized. Calculations were presented for H2S and H2O to demonstrate the accuracy of these algorithms.
A universal theoretical framework is proposed for calculating potential of mean force (PMF) between two solute particles immersed in a solvent bath, the present method overcomes all of drawbacks of previous methods. The only input required to implement the recipe is solvent density distribution profile around a single solute particle. The universal framework is applied to calculate the PMF between two large spherical particles immersed in small hard sphere solvent bath. Comparison between the present predictions and existing simulation data shows reliability of the present recipe. Effects of solvent-solute interaction detail, solvent bulk density, and solute size on the excess PMF are investigated. The resultant conclusion is that depletion of solvent component by the solute particle induces attractive excess PMF, while gathering of solvent component by the solute particle induces repulsive excess PMF, high solvent bulk density and large solute size can strengthen the tendency of attraction or repulsion. Relevance of transition from depletion attraction to gathering repulsion with the biomolecular interaction, i.e. hydrophobic attraction and hydration repulsion, is discussed.
First a short review on the dependence of crystal growth rate on the growth mechanism and concentration is present. Based on the structural model of micronucleus and crystalconstituent chains, and the feature of statistical dynamics for polymeric crystallization by molecular segregation, a general method for characterizing number the growth rate and micro crystal constituent chains and the size growth rate for crystals was proposed. According to this method, a set of quantitative expressions for correlating the growth rate in number and size with the four types of growth (folding, extending and combination of folding and extending), the crystalline temperature and the crystalline concentration was derived. Then combined the concentration index is combined with the fraction of conformation for segments, a new correlation of the concentration index to the temperature of crystallization and the flexibility of polymeric chain is theoretically obtained. The dependences of the index on the different types of growth are also studied. Finally the relationships between the growth rate for crystals and the concentration of solution were verified by the experimental validating the predictions made by the theory.
The anti-Stokes scattering was defined as the corresponding time-reversed process of the Stokes scattering. Based on the time-reversal symmetry the differences between one Stokes and its corresponding antiStokes Raman shifts have been theoretically demonstrated for the systems with Kramers-degenerate ground or final states. In the former cases the Stokes and its corresponding anti-Stokes Raman lines should display on the same side of the excited line. In the latter cases, they show major differences on two sides of the excited line. However, the whole normal Stokes Raman spectrum of a system may be still symmetric to the whole anti-Stokes spectrum, except in the cases of resonant, or laser, or circularly polarized excitation Raman scattering. This is a preliminary theoretical predication which needs more experimental and theoretical investigations.
The dynamical behavior taking on single periodic oscillation state in BZ reaction was measured experimentally as the system′s stoichiometric coefficient μ=1. The dynamical behaviors of the system under external linear and periodic perturbation were theoretical investigated. The results show that the system has an unstable region when perturbation varies linearly, and the system only takes on single periodic oscillation state in the region. But the states of the system take on 2np periodic oscillation and chaos under external periodic perturbation, and the dynamical behavior of the system changes from period-doubling into chaos. The theoretical results are also verified by numerical simulation studies.
Activation energy of hydroxyl radical OH reacting with alkanes was estimated from the quantitative relation between the bond dissociation energy (BDE) of Ri-H and the polarizability effect index (PEI) of alkyl radical Ri. Preexponential factor A in Arrhenius expression quantitatively was related to the topological steric effect index (TSEI) of alkyl radical Ri. The research results show that three parameters, PEI, TSEI and temperature T, can be used to quantify the activity of hydroxyl radical reacting with primary, secondary and tertiary carbonhydrogen bonds in alkane. The expression can accuratly evaluate the activity of C-H bonds. Moreover, the PEI and TSEI of alkyl radical Ri can be correlated quantitatively with the reaction absolute and relative rates of alkanes and cyclanes with hydroxyl radicals at various temperatures. The predicted rate constants are in good agreement with the experimental ones.
Jahn-Teller distortion of C80n(D2,Ih) was studied by the INDO method. It shows that C80(D2) is more stable than C80(Ih), which is in agreement with the experiment. Jahn-Teller distortion did not take place in C80n(D2) but happened in some of ions for C80n(Ih). Total energy of C80n was affected by the increase in absolute values of electric charges. Electronic spectra of C80 were calculated for the first time. Not only spectrum data of C80 consistent with the experiment were obtained but also electronic spectra of C80n were predicted where the electronic transition was assigned theoretically. The reason for the redshift of UV bands for C80n(D2) compared with that of C80(D2) and the blue-shift of peaks for C80n(Ih) relative to C80(Ih) is that the LUMO-HOMO energy gap of C80n(D2) is less than that of C80(D2) whereas the energy gap of C80n(Ih) is bigger than that of C80(Ih).
A new two-parameters, namely temperature and pressure relaxation times, model was proposed based on the basis of the isothermal-isobaric MD methods and both the parameters optimized by using the orthogonal test are 2 fs. The maximal deviation of system volume simulated under the optimal conditions was within the limit of 10%. The new model was used to simulate the selfdiffusion coefficients of argon and supercritical carbon dioxide at different temperatures, and the influence of temperature and pressure on selfdiffusion coefficients was analyzed qualitatively by the use of the kinetics theory. Good agreement is obtained between the simulated results and the experimentally measured data.
Based on the atomic and molecular reaction statics, the ground electronic states for Se2(3Σg), Se2+(2Πg),Se2-(2Πg)and Se22+(1Σg)and the corresponding reasonable dissociative limits were derived. Using density functional method (B3LYP)and 6311G** basis sets, the molecular equilibrium geometry and dissociation energy for Se2x(x=0,+1,-1,+2) were calculated. Then, with MurrellSorbie function form, spectroscopic date for Se2x(x=0,+1,-1,+2) were derived. The calculated results for Be, αe, ωe and ωeχe are 0.0790, 0.0002, 379.5760 and 0.9309 cm-1 respectively for Se2, 0.0849, 0.0002, 464.0401, 0.9754 cm-1 respectively for Se2+, 0.0564, 0.0002, 323.0775 and 0.8482 cm-1 respectively for Se2; 0.1001, 0.0001, 603.4454 and 0.0299 cm-1 respectively for Se22+, which are in good agreement with experimental or calculated values in references. It shows that Se2, Se2+, Se2- and Se22+can be stable.
The structures and stability of triplet HFSiS system were investigated by density functional theory(DFT)in detail. The optimized geometrical parameters and vibrational frequencies of all species were obtained at the level of B3LYP/6-311G** and the assignments of them were performed. At the same theoretical level, IRC calculations were carried. In addition, the singlet-point energies and relative energies were calculated by high level electron-correlation CCSD(T)/6-311G**. The isomerized and dissociated processes were explained by vibrational mode analysis method. The triplet PES is compared to the singlet one. The results are as the following: there are six isomers on the triplet PES. Moreover, 3HFSiS is found to be the most thermodynamically and kinetically stable and is able to be observed in experiments. Structures2 are the more stable ones between the two group bond cycled isomers and are predicted to be detected. 3SiSHF is the most unstable isomer in thermodynamics and kinetics.
Ultrasoft pseudopotential was generated for uranium and the plane waves pseudopotential formalism was used to study its crystal structures at zero temperature as a function of pressure. The alpha phases of uranium were fully relaxed. The zero-pressure zero-temperature equilibrium volumes and bulk moduli are consistent with previous calculations, and in excellent agreement with the experiment. This is also the case for cell parameters and pressure-induced phase transitions. In the calculation of NaCl and CaF2 structure type of compound of uranium, the difference of theoretical lattice constant and the experimental value is less than 3%. For UO2+x the trend of the lattice shinking with the x value increase is in accord with the experiment. For large U2C3 and U2N3 complex cells the difference of theoretical lattice constant and the experimental value is less than 3%, and the difference of coordination of atom is less than 5%.
The reaction for SiH3+O(3P) was studied by ab initio method. The geometries of the reactants, intermediates, transition states and products were optimized at MP2/6-311+G(d,p) level. The singlepoint calculations for all the stationary points were carried out at the QCISD(T) /6-311+G(d,p) level using the MP2/6-311+G(d,p) optimized geometries. The results of the theoretical study indicate that the major pathway is the SiH3+O(3P)→IM1→TS3→IM2→TS8→HOSi+H2. The other minor products include the HSiOH+H, H2SiO+H and HSiO+H2. Furthermore, the products HOSi, HSiO and HSiOH(cis) can undergo dissociation into the product SiO. In addition, the calculations provide a possible interpretation for disagreement about the mechanism of the reaction SiH4+O(3P). It suggests that the products HSiOH, H2SiO and SiO observed by Withnall and Andrews are produced from the secondary reaction SiH3+O(3P) and not from the reaction SiH4+O(3P).
The 1H and 13C-NMR of 2,4,6-trimethoxyphenol-1-O-D-glucopyranoside(Compound 1) isolated from Celastrus angulatus (Celastraceae) was calculated theoretically at the both levels HF/6-311+G(2d,p)//B3LYP/6-31G(d) and HF/6-311+G(2d,p)//B3LYP/6-31G(d,p) using the GIAO (gauge-independent atomic orbital) method. Statistical error analysis for theoretically predicted δH and δC values versus those experimentally observed for compound 1 was discussed. The results show that the theoretically predicted δH and δC values of β conformer of compound 1 are more close to the experimentally observed values than α conformer, and the β conformer of compound 1 is more stable than α conformer according to molecular energy theoretically calculated. So compound 1 is assigned to be 2,4,6-trimethoxyphenol-1-O-β-D-glucopyranoside, which is in good consistence with the conclusion deduced by the anomeric proton signal (δH=4.80, J=7.3 Hz) experimentally observed.
The structures and energies of reactant, product, intermediate, transition and second order saddlepoint in the transfer reaction of inner hydrogen atoms in porphine(PH2), m-tetra-fluorineporphyrin(m-TFPH2), β-octa-fluorine-porphyrin (β-OFPH2) and m-tetra-fluorine, β-octa-fluorine-porphyrin(12FPH2) were calculated by using B3LYP/6-31G** method under certain symmetry restriction. In the transfer reaction of inner hydrogen atoms in all various matters, the comparison of structures and the energies shows that the probabilities of asynchronous mechanism are larger than that of synchronous mechanism via a second-order saddle-point, and substitutents to porphyrin in hydrogen migration have no influence on mechanism choice. But the substitutents can affect speed differences between the synchronous mechanisms and the asynchronous mechanisms. In addition, fluoro substitutents decrease speeds of positive and negative reactions in asynchronous mechanisms, which is in agreement with chemical intuition.
The reaction for CH3CH2+N(4S) was studied by ab initio method. The geometries of the reactants, intermediates, transition states and products were optimized at MP2/6-311+G(d,p) level. The corresponding vibration frequencies were calculated at the same level. The singlepoint calculations for all the stationary points were carried out at the QCISD(T)/ 6-311+G(d,p) level using the MP2/6-311+G(d,p) optimized geometries. The results of the theoretical study indicate that the major products are the CH2CH2+3NH and H2CN+CH3, and the minor products are the CH3CHN+H in the reaction. The majority of the products CH2CH2+3NH are formed via a direct hydrogen abstraction channel. The products H2CN+CH3 are produced via an addition/dissociation channel. The products CH3CHN+H are produced via an addition/dissociation channel.
Theoretical studies on the α- and β-forms nitroguanidine were carried out using ab initio theoretical methods, at the MP2/6-31G(d,p) level. The predicted geometrical parameters were in good agreement with the available theoretical values, which calculated by other author. The three C-N bond lengths in α-form nitroguanidine were different, the longest bond length was 1.430 A, the shortest was 1.283 A. But they were almost similar in β-form, the longest was 1.375 A, the shortest was 1.322 A. Therefore there were conjugative effects in β-form but not in α-form. The calculated results also show that the β-form is stable with respect to the α-form from energetically, lower 28.16 kJ/mol corrected with zero point vibrational energy. The transition-state for the unimolecular isomerization was conformed by the IRC calculation. The calculated energy barrier for the direct intramolecular hydrogen atom transfer isomerization process was 132.95 kJ/mol. The isomerization reaction, exothermal reaction, is a typical intramolecular hydrogen atom synfacial transfer reaction. Rate constants of the isomerization reaction were evaluated within the temperature range of 200-1773 K by the classical transition state theory. The rate constant was 1.99×10-11 s-1 and the equilibrium constant was 1.00×105 at 298 K. With the temperature increasing, the equilibrium value decayed and the reaction process was more difficult.
The geometries and their harmonic frequencies of the difluoroethylene isomers were gradient optimized using ab initio methods at the different levels. High-level methods give very good structural parameters in comparison to experiment. The single energy of stable structure and the frontier orbital energy gap were calculated using MP4SDTQ/6-311++G(2df,2pd) method, and it is found that the single energy of stable structure of cis isomer is lower than that of trans isomer. This is consistent with the experimental result. Mulliken population analyses were also performed to interpret the internal nature of cis preference of difluoroethylene isomers.
The energies, equilibrium geometries and harmonic frequencies of the three electronic states (the ground state X 1Σ+, the first excitation state A 1Σ+ and the second excitation degenerate state B 1Π) of LiH molecule have been calculated by using the GSUM (Group Sum of Operators) method of SAC/ SAC-CI with the basis sets D95(d), 6-311G**, and cc-PVTZ. Comparing with the above-mentioned three basis sets, the conclusion is gained that the basis set D95(d) is the most suitable for the energy calculation of LiH molecule. The whole potential curves for these three electronic states are further scanned, using SAC/D95(d) method for the ground state and SAC-CI/D95(d) methods for the excited states. Murrell-Sorbie function were fitted using a least square and then the spectroscopy constants are calculated, which are in good agreement with the experimental data.
Based on the FS(Finnis-Sinclair) many-body potential model, the rapid cooling process of a system, which consists of 375 Cu atoms and 125 Au atoms, controlled by period boundary condition was simulated. The dependence of pair distribution function of melten compound AuCu3 on the temperature under these conditions was researched. It can be concluded that the noncrystal exists under 700 K, and the liquid-glass transition temperature is approximately 680 K according to the Abraham′s method. Furthermore, the feature of version of cluster in melten AuCu3 was investigated by Honeycutt pair analysis technique. It is demonstrated that the structural configuration in melten AuCu3 has remarkable variation during the formation of noncrystal according to the relationship between the bonded pairs and polyhedron and temperatures. The defective polyhedra in liquid AuCu3 have greatest changes accompanying the changing temperatures.
The electron ionization time-of-flight (TOF) mass spectra of a series of 5-ethoxycarbonyl-4-substituted-6-methyl-3,4-dihydropyrimidin-2(1H)-ones were studied to establish their fragmentation processes. Using the high resolution capabilities of the TOF instrument, exact masses for each fragment were determined. These data were used to infer molecular formulas and elemental compositions for all molecular ions and fragments through software interpretation and according to the established fragmentation rules the majority of ions were fully assigned. Two main fragmentation routes can be found in this work. First of them, for all the title compounds, includes the formation of three cations, by loss of R1 from the position 4, C2H4 (via a McLafferty rearrangement) from the ester group and H2O via a cyclic-six-membered transition state. The second route, for 4-aromatic compounds, consists of the formation of a cation by loss of EtCO2. Several additional fragmentations for individual compounds are proposed.
The core-level X-ray photoelectron emission spectra of the quasi-one dimensional spin 1/2 antiferromagnetic system Sr14-xCaxCu24O41(x=0, 3.5, 6, 7, 8.4) were measured. The main peak of Cu2p3/2 was about 933.8 eV, and the full width of half maximum height was about 3.3 eV. Simulation of Cu2p3/2 by XPSPEAK41 shows that the percents of Cu2+ and Cu3+ in Sr14Cu24O41 are 92.13% and 7.87%, no obvious change to Cu2p core-level is observed by the partial substituting Ca for Sr, and the average valence of Cu in this system is estimated to be 2.08. The main peak of O1s is about 531.0 eV, and the weak shoulder toward the low binding energy direction can be considered as the contribution of Ca-O bond. The binding energies of Ca2p3/2 and Sr3d5/2 indicate that their valence in this system are both +2, without mixed valence.
A series of N-bonded donor-acceptor derivatives of phenothiazine containing benzene (PHPZ), anisole (ANPZ), pyridine (PYPZ), naphthalene (NAPZ), acetophenone (PEPZ), and benzonitrile (BNPZ) as an electron acceptor was synthesized. Their photophysical properties were investigated in solvents of different polarities by absorption and emission techniques. These studies clearly reveals the existence of an intramolecular charge transfer (ICT) excited state in the latter four compounds. The solvent dependent Stokes shift values were analyzed by the modified Lippert-Mataga equation to obtain the excited state dipole moment values. The large excited state dipole moment suggests that the full electron transfer takes place in the A-D systems. The obtained values of redox potentials indicate that both subunits of all the A-D molecules studied interact very weakly in the ground states. The results obtained from the analysis of the CT fluorescence spectra confirm that the small conformational changes accompanying excited state charge transfer, the twist angle between the donor and acceptor moieties in the excited 1CT state seems to be similar to that in the ground state.
The TiO2 nanoparticles capped with sodium dodecylbenzenesulfonate (DBS) were synthesized by a sol-hydrothermal method, and were also characterized by XRD, TEM, Surface Photovoltage Spectroscopy (SPS) and Photoluminescence (PL). The effects of capping DBS on photovoltage and photoluminescence performances of TiO2 nanoparticle as well as appropriate capping conditions were principally investigated. The results show that the capping situation is desirable when the pH value and adding DBS amount are in the range of 4.5-5.5 and 1.0%-3.0% of TiO2 weight in advance of the hydrothermal process, respectively. The added DBS could inhibit the growth of anatase crystallite during the hydrothermal process. Moreover, the intensities of SPS and PL of TiO2 nanoparticle decreased after DBS was capped, which is possibly attributed to the electrophilic property of sulfonic acid group (-SO3-) as well as the decrease of surface defect.
V2O5 thin films were successfully prepared on ITO substrate with electrophoresis deposition (EDP) through V2O5 sol. X-ray diffraction and scanning electron microscopy were used for studying the structure of the films. The optical and electrochemical properties were measured by the transmittance spectra and cyclic voltammetry measurements, respectively. It is found that V2O5 thin films deposited by EDP are a compact microstructure with finer adhesive force with ITO substrate and the thickness is uniform. During the cycle experiment, the films exhibited reversible two-color (yellow at oxidation and green at reduction) with a maximum transmittance change of around 30%. Moreover, the films had an excellent cycle for lithium intercalation/deintercalation and good cycle stability, the cycle efficiency for the 50th cycle was 88.02% and the films still had fine adhesive force with ITO substrate with no dissolving over more than 50 cycles. The Li+ diffusion coefficient in V2O5 thin film was 5.10×10-12 cm2/s by the electrochemical impedance spectra method. All results indicate that V2O5 thin films by the electrophoresis deposition may be suitable for the use in the electrochromic devices.
The photochromism of a new star-like liquid crystal that was written by Si(AZO)4 centered by Si and containing four butoxyazobenzene mesogens in its periphery was described. The quantum yield, photoisomerization and photo back-isomerization of Si(AZO)4 in CHCl3 and THF are studied by UV/Vis absorption spectra. The results indicate that the photochromism and photo back-isomerization of Si(AZO)4 in CHCl3 and THF were in accordance with the first order kinetics. The photochromism and photo back-isomerization rate constants are 10-1 s-1, which are 107 times larger than that of side-chain liquid crystalline polymers containing the same azobenzene moieties. These results indicate that the star-like structure does not significantly affect the photoisomerization activity of the azobenzene mesogen in its periphery. The kt/kc of Si(AZO)4 is less than that of azobenzene mesogen which shows that the Si(AZO)4 has better photo-reversibility. So the star-like liquid crystal has potential applications and will become a new type photocontrolable switch and information functional material.
The solid material of coupled semiconductor SnO2-TiO2 was prepared by sol-gel method. The Photocatalyst SnO2-TiO2 supported metallic Cu was prepared by an isovolumic impregnation method. The surface structure, particle size, photo absorption performance and photocatalysis performance of the materials were characterized by X-ray diffraction, Laser Raman spectroscopy, Temperature programmed reduction and Infrared spectroscopy, Transmission electron microscopy, Ultraviolet-visible diffuse reflectance spectroscopy and Micro-photoreactor. The experiment results show that 10%SnO2 disperses on the surface of TiO2 support with one monolayer of non-crystalline phase, and the average particle size of 1%Cu/10%SnO2-TiO2 is about 22 nm. Blue shifting of photo absorption edges is observed clearly after addition of SnO2 on the surface of TiO2. The crystalline phase SnO2 forms and photo absorption performance decreases when supporting amount of SnO2 is more than the monolayer phase(>10%). The formation of Ti-O-Sn bond in the solid systems promotes transfer of generating charge carriers between TiO2 and SnO2. Loaded metallic Cu increases the photo absorption capacity of the photocatalyst and enlarges photo absorption range to visible light. Photo absorption performance and quantum efficiency of the photocatalysts have a corresponding relationship with various Sn content. Both photo absorption performance and quantum efficiency of the reaction on 1%Cu/10%SnO2-TiO2 are the best among the others, and the quantum efficiency reaches 13.9%.
Single-crystalline LaF3 flakes was synthesized through a facile solution-phase approach in aqueous ammonia and ethylenediamine. Applying the thermal treatment at 100 ℃ for 20 h, the LaF3 recrystallized, grew epitaxially and precipitated into flakes in aqueous ammonia or ethylenediamine. The formation of flakes could be attributed to the coordination effect of the solvent.
Nanocrystalline anatase-type TiO2 was prepared by the hydrolysis-precipitaiton method, the rare earth hydrogen storage alloys were modified with the as-prepared TiO2 and the photocharging behavior, and cyclic voltammetry curves and EIS spectra were measured. The experimental results show that the potential has little shift under the light irradiation for the unmodified electrode. However, for the TiO2modified electrode, a remarkable shift of the potential to negative direction (up to -0.835 V) takes place under the light irradiation, which means the generation of H atom on the electrode surface under the light irradiation. The EIS results also indicate that there exists the absorption of H atom and the following diffusion of H atom into the hydrogen storage alloys under the light irradiation. The FEM observations on the electrode surface show that a large amount of microcracks appear on the electrode surface. These microcracks may be induced by the bulk expansion when the generated hydrogen atoms were absorbed by the hydrogen storage alloys.
An admixture of acrylonitrile, methyl methacrylate, styrene and commercial liquid electrolyte (LB302, 1 mol/L solution of LiPF6 in 1∶1 EC/DEC) was enclosed in CR2032 cells. The assembled cells were then γ-ray irradiated using configurations of LiNi0.8Co0.2O2/Li half cells. Through this in-situ irradiation polymerization process, rechargeable lithium cells with poly(acrylonitrile-co-methyl methacrylate-co-styrene) (PAMS) were obtained based gel polymer electrolytes. The structure and thermal stability of PAMS were characterized by FTIR and DSC analyses. The electrochemical properties and chargedischarge performance of PAMS-based gel-polymer lithium cells were evaluated by AC impedance spectroscopy, cyclic voltammetry and gavanostatic battery cycling. The results indicate that the in-situ gama-ray irradiation approach is convenient to prepare gel-polymer lithium cells with good charge-discharge performance.
Emphasis of this work was paid to the study on the sound absorption mechanism of gradient polymer solution. A specially designed gradient polymer solution and an uniform polymer solution were synthesized. The sound attenuation properties of the gradient polymer solution and the uniform polymer solution were measured in sound tube. Results show that the sound attenuation of the gradient polymer solution is larger than that of the uniform. Depending on the experimental result and the theory of sound wave propagation in layered medium, a mathematical model of sound attenuation in the gradient polymer solution was established. And a calculating program was carried out by Maple and Matlab. The calculated results are fairly in good agreement with the measured. So mechanism of the gradient polymer solution was developed. This mechanism can be described as follows: a polymer solution with the concentration gradient layer forms the gradient polymer solution. This gradient layer led to multiple reflection and absorption of sound when the sound wave propagated in it. Finally the sound energy was transferred into heat.
A differential scanning calorimeter was used to study the thermal behaviors of polyalcohols aqueous solutions, such as supercooling degree of heterogeneous nucleating temperature, hydration properties. The experimental results show that the variation of supercooling and hydration behavior does not have obvious rules at the low concentrations. However, the supercooling degree and the content of unfrozen water increased with the solution concentration at the high concentrations. The difference of hydration properties shows the important effects of function groups (methyl groups and hydroxyl groups).