2007 Vol. 20, No. 1

Letter
Happy New Year!
Happy New Year again! This year is very special for CJCP since it is the 20th anniversary. We have seen a tremendousdevelopment in the field of chemical physics in China in the last 20 years. CJCP has always been there in this important period of development in Chinese science, and CJCP has made significant and important contributions to the development of the chemical physics research field in China. And we certainly will continue to do so in the future.
In the beginning of last year, we changed the journal into a full English journal in an effort to enhance the journal impact in the international scientific community. In this transition period, CJCP has encountered many difficulties, and we have also made great progresses. We deeply believe that making CJCP a full English journal is an important step to increase its influence in the international research community. We hope this is the moment of a new start for the great traditionof CJCP to serve the Chinese chemical physics and physical chemistry community, and beyond. Now, our new web based editorial and review system is in place, we hope CJCPwill serve our community in a more efficient and direct way (Website: http://cjcp.ustc.edu.cn ). With the support of the chemical physics and physical chemistry community, I am confident that this journal will make more significant contributions to the development of the chemical physics researchfield.
At this 20th anniversary of CJCP, I want to take this special opportunity to thank many people who have lead this journal through difficulties and triumphs in the most part of the last 20 years, especially the former Editor-in-Chief, Professor Nanquan Lou, and the former senior associate editor, Prof. Shuqin Yu. And I also want to thank the editorial staff members who have made great efforts in producing a high quality scientific journal. At last, I hope everybody who cares about the Chinese chemical physics development will support our effort to make this journal better.

Xue-ming Yang
Editor-in-Chief
February 12, 2007
Magnetization of Bi0:9-xGdxLa0:1FeO3 (x=0.3, 0.5, 0.6 and 0.7) is reported. An abnormal negative magnetization appears in the temperature-dependent magnetization curves, and the temperature-dependent coercive field shows a maximum in the vicinity of the compensation temperature where the total magnetization is zero. These results suggest that in the ferrimagnetic-like Bi0:9-xGdxLa0:1FeO3 system the Gd and Fe magnetic sublattices are coupled antiferromagnetically.
Article
The reaction kinetics of cyanomethylidyne radical, CCN( eX2Π), with a series of primary alcohols were studied at about 1.33 kPa total pressure and room temperature using pulsed laser photolysis/laser-induced fluorescence (LP/LIF) technique. The CCN radical was produced via laser photolysis of CCl3CN with the fourth harmonic output of a Nd: YAG laser (266 nm). The relative concentration of the CCN( eX2Π) radical was monitored by LIF in the (0, 0) band of the CCN( ~ A2¢? eX2Π) transition at 470.9 nm. Under pseudofirst-order conditions, the reaction rate constants of CCN( eX2Π) with a series of primary alcohol molecules (n-CnH2n+1OH, n=1-6) were determined by measuring the time evolution of the relative concentration of CCN( eX2Πi). The measured rate constants increased monotonously with the number of carbon atoms in the alcohols, and the values for reactions of CCN( eX2Π) with alcohols were larger than those for reactions of CCN( eX2Π) with alkanes (C1-C5). Based on the bond dissociation energies and linear free energy correlations, it was believed that the reactions of CCN( eX2Π) with alcohols proceeded via a hydrogen abstraction mechanism that was analogous to CCN( eX2Π) with alkanes. The experimental results indicated that the H atoms on the C-H bonds were activated at the presence of the OH group in alcohol molecules and the hydrogen abstraction from the C-H bonds in the alcohol molecules was the dominant reaction pathway. The relation between the rate constants and the long-distance attractive potentials between the CCN radical and the alcohol molecules was discussed.
Three-dimensional time-dependent quantum wave packet calculation was performed to study the reaction dynamics of Cl+H2(D2) on two potential energy surfaces (CW PESs). The first CW PES is with spin-orbit correction; the second is without spin-orbit correction. The integral cross-section and reaction probability as a function of collision energy are calculated in the collision energy range of 0.1 eV to 1.4 eV. For reaction of Cl with D2, the reaction section with spin-orbit correction has a shift toward the high energy because the barrier height increases. As for the reaction of Cl with H2 at low collision energy, it is more reactive on the PES with spin-orbit correction than on the low barrier height PES without spin-orbit correction, due to the tunnel effect for the reaction of the Cl with H2. When the collision energy is higher than 0.7 eV, the reactivity on the low barrier height PES is larger than that on the high barrier height PES. It is believed that the barrier height plays a very important role in the reactivity of Cl with (H2, D2). For the Cl+H2 reaction the barrier width is also very important because of the tunneling effect.
Bis-(4-stearoylaminophenyl) ether (BSADE) can aggregate and self-assemble in water. Transmission electron microscopy (TEM) indicated that the morphology of BSADE aggregates in water was entanglement and thin fiber-like, and that a three dimensional network structure was formed. Water molecules were entrapped in this three dimensional network structure and formed a new type of condensed system (so-called water molecular gel). Water molecular gel is a typical mesoporous material which can be characterized by the fractal dimension D. Using gas adsorption method along with measurement of porosity and specific surface area, the fractal dimension D of the complicated pores was 2.1-2.2 for this water molecular gel. Using viscosity method and the Cayley fractal tree, the fractal dimension D of the fiber-like three dimensional network was determined to be 1.98. The formation process of water molecular gel can be described as nucleation followed by a repeated growing and branching cycle.
Molecular dynamics simulations were carried out to study the structure of ion clusters and hydration properties of KNO3 solution. The water molecule was treated as a simple-point-charge (SPC) model, and a four-site model for the nitrate ion was adopted. Both the Coulomb and Lennard-Jones interactions between all the charged sites were considered, and the long-range Coulomb electrostatic interaction was treated using Ewald summation techniques. The configuration of ionic pairs, the radial distribution function of the solution, and the effect of solution concentration on ionic hydration were studied in detail. It was found that there are ionic association phenomena in KNO3 solution and that the dimeric, triplet, solvent-separated ion pairs, and other complex clusters can be observed at high ionic concentration condition. As the concentration of solution decreases, the ionic hydration number increases, 5-7 for cation K+ and 3.5-4.7 for anion NO3-, which is in good agreement with former Monte Carlo and time-of-flight neutron diffraction results.
The elementary reaction of the CH3 radical with NO2 was investigated by time-resolved FTIR spectroscopy and quantum chemical calculations. The CH3 radical was produced by laser photolysis of CH3Br or CH3I at 248 nm. Vibrationally excited products OH, HNO and CO2 were observed by the time-resolved spectroscopy for the first time. The formation of another product NO was also verified. According to these observations, the product channels leading to CH3O+NO, CH2NO+OH and HNO+H2CO were identified. The channel of CH3O+NO was the major one. The reaction mechanisms of the above channels were studied by quantum chemical calculations at CCSD(T)/6-311++G(df,p)//MP2/6-311G(d,p) level. The calculated results fit with the experimental observations well.
The hydrogen bonding interaction of 1:1 dimer formed between HNO and HArF molecule has been completely investigated in the present study using Second-order M?ller-Plesset Perturbation (MP2) method in conjunction with 6-311+G**, 6-311++G** and 6-311++G(2d,2p) basis sets. The standard and CP-corrected calculations have been employed to determine the equilibrium structures, the vibrational frequencies and interaction energies. The interaction energies of the dimers were also calculated at G2MP2 level. Two stable structures are found as the minima. Dimer I(H···F)is a five-membered cyclic hydrogen bonded structure and is more stable than the Dimer II(H···O). The blue-shifted N-H···F hydrogen bond is confirmed with standard and CP-corrected calculations by the MP2 and DFT methods in conjunction with different basis sets. The results obtained at MP2 in conjunction with different basis sets show there is a red-shifted hydrogen bond (Ar-H···O) in the Dimer II(H···O). The topological and electronic properties, the origin of red- and blue-shifted hydrogen bonds were investigated at MP2/6-311++G(2d,2p) with CP corrected calculations. From the NBO analysis, the reasonable explanations for the red- and blue-shifted hydrogen bonds were proposed.
The microphase diagrams of special A2B copolymer melts were presented by using the self-consistent field theory for star copolymer systems. Unlike the phase diagram of diblock copolymer, only three classical structures, namely spherical phase, cylindrical phase and lamellar phase were discovered in the diagram of the A2B system. The change in chain architectures allowed sufficient shifts of phase boundaries and widened the range of fB for which lamellar phase occurred, to some degree. Simply, an asymmetric architecture for copolymer allowed control of the morphology independent of the volume fraction.
JP-10 (exo-tetrahydrodicyclopentadiene, C10H16) ignition delay times were measured in a preheated shock tube. The vapor pressures of the JP-10 were measured directly by using a high-precision vacuum gauge, to remedy the difficulty in determining the gaseous concentrations of heavy hydrocarbon fuel arising from the adsorption on the wall in shock tube experiments. The whole variation of pressure and emission of the OH or CH radicals were observed in the ignition process by a pressure transducer and a photomultiplier with a monochromator. The emission of the OH or CH radicals was used to identify the time to ignition. Experiments were performed over the pressure range of 151-556 kPa, temperature range of 1000-2100 K, fuel concentrations of 0.1%-0.55% mole fraction, and stoichiometric ratios of 0.25, 0.5, 1.0 and 2.0. The experimental results show that for the lower and higher temperature ranges, there are different dependency relationships of the ignition time on the temperature and the concentrations of JP-10 and oxygen.
A new scheme is proposed to suppress stable and meandering spiral waves in excitable media by generating a self-exciting target wave in a local area. An arbitrary selected grid in the media is sampled, and the sampled signal is fed back into a local area in the media. Numerical simulation results confirm its effectiveness when the scheme is introduced into anisotropic (the diffusion coefficient is perturbed vs. time and/or space) and isotropic media. Results also show the scheme's robustness to spatiotemporal noise.
Electronic structure and photophysical properties of 2-(N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine are studied theoretically with quantum chemical methods as well as 2D site and 3D cube representations. The theoretical results reveal that the first excited state is an intramolecular charge transfer excited state. The change in dipole moment for the first excited state of the excitation is fitted, and the calculated result the change in dipole moment ¢1=6.40 D is consistent with the experimental result ¢1=6.90 D. The polarizability is also fitted. The large changes in dipole moment and the polarizability of the excitation show that S1 is of large nonlinear optical (NLO) effect. The NLO will promote efficient two-photon-absorption cross sections. The excited state properties of dpbt with different external electronic fields are also discussed theoretically.
The thermoelastic properties of MgO over a wide range of pressure and temperature are studied using the first-principles plane wave pseudopotential method within the generalized gradient approximation. It is shown that MgO remains in the B1 (NaCl) structure at all pressures existing within the Earth, and transforms into the CsCl-type structure at 397 GPa. The athermal elastic moduli of MgO are calculated, as a function of pressure up to 150 GPa. The calculated results are in excellent agreement with experimental data at zero pressure and compare favorably with other pseudopotential predictions over the pressure regime studied. MgO is found to be highly anisotropic in its elastic properties, with the magnitude of the anisotropy first decreasing between 0 and 20 GPa and then increasing from 20 GPa to 150 GPa. The Cauchy condition is found to be strongly violated in MgO, reflecting the importance of noncentral many-body forces. The thermodynamic properties of MgO are consistent with the experimental data at ambient condition.
Ample evidence suggests that the local structures of peptide fragments in native proteins are to some extent encoded by their local sequences. Detecting such local correlations is important but it is still an open question what would be the most appropriate method. This is partly because conventional sequence analyses treat amino acid preferences at each site of a protein sequence independently, while it is often the inter-site interactions that bring about local sequence-structure correlations. Here a new scheme is introduced to capture the correlation between amino acid preferences at different sites for different local structure types. A library of nine-residue fragments is constructed, and the fragments are divided into clusters based on their local structures. For each local structure cluster or type, chi-square tests are used to identify correlated preferences of amino acid combinations at pairs of sites. A score function is constructed including both the single site amino acid preferences and the dual-site amino acid combination preferences, which can be used to identify whether a sequence fragment would have a strong tendency to form a particular local structure in native proteins. The results show that, given a local structure pattern, dual-site amino acid combinations contain different information from single site amino acid preferences. Representative examples show that many of the statistically identified correlations agree with previously-proposed heuristic rules about local sequence-structure correlations, or are consistent with physical-chemical interactions required to stabilize particular local structures. Results also show that such dual-site correlations in the score function significantly improves the Z-score matching a sequence fragment to its native local structure relative to nonnative local structures, and certain local structure types are highly predictable from the local sequence alone if inter-site correlations are considered.
Density functional theory (DFT) calculations were performed to study the monotungsten-oxide WO4 cluster in the anionic and neutral charge states. The results show the two most stable WO4- isomers have C2v and D2d symmetries and both have the four oxygen atoms attached to the tungsten W monomer atomically. The WO4- species previously suggested with a molecular adsorption of di-oxygen is found to be a metastable isomer of WO4-, whose geometric, vibrational properties and electron affinities are in good agreement with the ultraviolet photoelectron spectroscopy (UPS) experimental results. The reason why this metastable isomer could be observed in the experiment is given by a molecule formation mechanism. The UPS spectrums compare well with the excitation spectrum computed by time-dependent DFT method.
The nanometer and micrometer molecular sieves MCM-41 were prepared by a hydrothermal method. Cadmium (II) was exchanged into the molecular sieves by ion-exchange, and thioacetamide was then used as a precursor of hydrogen sulfide for sulphidizing the (MCM-41)-cadmium samples to prepare the host-guest composite materials (MCM-41)-CdS. By means of chemical analysis, powder X-ray diffraction, infrared spectroscopy, low temperature nitrogen adsorption-desorption technique, solid state diffuse reflectance absorption spectroscopy and luminescence, the prepared materials were characterized. The chemical analysis shows that the guest is successfully trapped in the molecular sieves. The powder X-ray diffraction suggests that the frameworks of the molecular sieves in the prepared host-guest composite materials are retained during the preparative process. They are intact and the degrees of crystallinity are still very high. The infrared spectra show that the frameworks of the prepared host-guest materials keep intact. The low temperature nitrogen adsorption-desorption studies indicate that the pore volumes, the pore sizes and the surface areas of the prepared composite materials decrease relative to those of the MCM-41 molecular sieve hosts. This shows that the guests are successfully encapsulated in the channels of the molecular sieves. The solid state diffuse reflectance absorption spectra of the prepared host-guest composites show some blue-shifts relative to that of bulk cadmium sulfide, indicating that the guests are trapped in the channels of the molecular sieves. This shows the obvious stereoscopic confinement effect of the molecular sieve host on the nanometer cadmium sulfide guest. The (nanometer MCM-41)-CdS and (micrometer MCM-41)-CdS samples show obvious luminescence.
Er-Y-codoped ZrO2 mixed oxides with monoclinic, tetragonal and cubic structures were prepared by a sol-gel method. The crystal structure of ZrO2 matrix and the effect of the ZrO2 phases on the fluorescence properties of Er3+ were studied using Raman spectroscopy. The results indicated that the fluorescence properties of Er3+ depend on its local ZrO2 crystal structures. As ZrO2 matrix transferred from monoclinic to tetragonal and cubic phase, the Raman and fluorescence bands of Er3+ decreased in intensities and tended to form a single peak. With 632.8 nm excitation, the bands between 640 and 680 nm were attributed to the fluorescence of Er3+ in the ZrO2 environment. However, only the fluorescence was observed and no Raman spectra were seen under 514.5 nm excitation, while only Raman spectra were observed under 325 nm excitation. UV Raman spectroscopy was found to be more sensitive in the surface region while the information provided by XRD mainly came from the bulk. The phase with lower symmetry forms more easily on the surface than in the bulk.
TiO2 thin films with different crystalline structures were prepared by the CVD method. The relationship between photocatalytic activity of a TiO2 thin film and its crystalline type was investigated. These films were characterized by XRD and AFM. Their photocatalytic properties were tested by the degradation of NO2-. The results showed that the crystalline structures of TiO2 thin films are primary anatase and/or rutile when the preparation temperatures were less than 573 K and higher than 773 K respectively. When the preparation temperature was around 623 K, the structures of TiO2 thin films were mixed crystalline structure, which showed the highest catalytic activity. When the ratio of rutile to anatase in TiO2 thin films fell between 0.5 and 0.7, the highest catalytic activity for the degradation of NO2- was found.
EuAl3(BO3)4 and Dy3+:EuAl3(BO3)4 crystals were synthesized and their luminescence properties were studied. The EuAl3(BO3)4 crystals have strong red emission. In the Dy3+ doped EuAl3(BO3)4 crystals, the Dy3+ strongly sensitized the luminescence of the Eu3+. A resonance mechanism of the energy transfer was suggested. The optimum Dy3+ concentration of the sensitization effect was 0.2. When the Dy3+ concentration was higher than 0.2, the quick drop of the Eu3+ 613 nm emission for DyxEu1-xAl3(BO3)4 was attributed to the Dy3+ concentration quenching effect.
A fi-cyclodextrin dimer tethered by photoswitchable dithienylethene moieties was synthesized as a potentially tunable receptor. The dimer exhibits pronounced photochromic properties. Irradiation of the dimer in open form with UV light at 254 nm resulted in immediate photocyclization to the pink closed form; the colorless open form could be regenerated by irradiation with visible light of wavelength >460 nm. The reaction kinetics of the forward photoprocess were also studied. To investigate the binding ability of the dimer in open and closed forms, a fluorescence titration was performed. It was found that the stability constant for the binding of TSPP (meso-tetrakis (4-sulfonatophenyl)porphyrin) by the closed form of the dimer is a factor of 5 higher than that of the open form.
Errata & Comment
Photoinduced Electron Transfer Between Mono-6-p-nitrobenzoyl-fi-cyclodextrin and Adamantanamine-Cn-Co/Ni-porphyrins (Vol. 19, No. 5, Content (2006)
Hui Huang*, Wen-kui Zhang, Yong-ping Gan, Lei Zhang, Chen Wang . . . . . . . . . . . . . . . . . . . . . . . . .428
should be
Photo-electrochemical Lithium Insertion Characteristics of Carbon Nanotubes Modified with SrTiO3 Photocatalyst
Hui Huang*, Wen-kui Zhang, Yong-ping Gan, Lei Zhang, Chen Wang . . . . . . . . . . . . . . . . . . . . . . . . .428