The hydration state of a compound depends on the activity of water (aH2O) in its crystallizing medium. This study utilized powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) to investigate the crystalline states of ciprofloxacin precipitation. In these long equilibrated water-methanol systems, a series of water activities were obtained by adjusting the water-methanol volume ratios. We used high performance liquid chromatography (HPLC) to measure the solubility of ciprofloxacin hydrate, anhydrate, and their mixtures in these solutions with various water activities. The results showed that ciprofloxacin's solubility basicallychanged according to the crystallization state of the precipitated solid. A relationship was determined between the phase stability of the ciprofloxacin anhydrate/hydrate and the water activity of the solutions. By comparing the relationships we established above with the PXRD data of the ciprofloxacin samples that were stored for 12 weeks under constant relative humidity and room temperature, we found that the methodology employed in this experiment was able to accurately and efficiently predict the phase conversion between ciprofloxacin anhydrate and hydrate. We also demonstrated how the water activity could affect the relative stability of these crystalline solids in water-methanol solutions.

To investigate the enthalpy relaxation behavior of xylitol glass and the influence of carbon chain length on the glass transition and relaxation of polyalcohols, differential scanning calorimetry (DSC) was employed to obtain the specific heat capacity (Cp) near the glass transition temperature (Tg) at different cooling rates. A curve-fitting method was used to obtain the TNM (Tool-Narayanaswamy-Moynihan) model parameters and the results were compared to the published data of other polyalcohols. Although the TNM model can be used to reproduce the experimentally normalized Cp curves of xylitol, different model parameters were found at different cooling rates, indicating that the TNM model parameters are not material constants but are sensitive to the thermal history. The pre-exponential parameter (A), non-linear parameter (x), and non-exponential parameter (β) decreased as the cooling rate increased while the apparent relaxation activation enthalpy (△h*) changed inversely. We found that Tg, △h*, and the dynamic fragility (m) increased as the alkyl carbon chain increased while x and β showed an approximate decrease except for the case of xylitol.

First-principles theoretical study of the elastic and thermodynamic properties of ZnTe in zinc-blende (ZB) structure at high temperature and pressure was performed by using the plane-wave pseudopotential method. The calculated lattice parameter of 0.6095 nm is in excellent agreement with the experimental value of 0.6103 nm and is only 0.1% smaller. The elastic constants and bulk modulus at p =0 GPa and T =0 K are also in agreement with experimental data. From the values of the elastic constants at high pressures, the transition pressure is about 10 GPa judged by the mechanical stability conditions of cubic crystals and this is consistent with available experimental data. The Debye temperature (249 K) at the normal temperature (T=300 K) and the values for heat capacity (CV) at different pressures and temperatures were also obtained by applying the quasi-harmonic Debye model. We found that the CV decreased with the increase of pressure and was close to the Dulong-Petit limit at high temperature and pressure.

Nanosecond transient Raman spectroscopy is a widely used technique to investigate ultrafast structural dynamics in molecules. We studied the rebinding kinetics between deoxymyoglobin (DeoxyMb) and NO using nanosecond transient Raman spectroscopy. By monitoring the ratio between the intensity of the υ4 vibrational mode in the photoproduct (DeoxyMb) and in the reactant (MbNO) at different incident laser fluxes, we obtained the recombination kinetics between DeoxyMb and NO in MbNO. For comparison, the kinetics of NO rebinding to DeoxyMb in MbNO was also studied using picosecond time-resolved Raman and absorption experiments. The kinetics results obtained with nanosecond transient Raman were consistent with those obtained by picosecond time-resolved Raman and absorption experiments.

Low pressure premixed laminar dimethyl ether (DME)/oxygen/ar n and ethanol/oxygen/ar n flames (equivalence ratio: 1.0) were studied by molecular-beam sampling mass spectrometry (MBMS) combined with the tunable synchrotron radiation photoionization technique. Combustion intermediates were identified by measuring photoionization efficiency (PIE) spectra, and the mole fraction profiles of these species at different flame positions were presented. Similarities and differences of main intermediate formation characteristics between the two flames were analyzed based on derived reaction mechanisms. Experimental results show that both flames contain the same intermediates such as CH3, CH4, C2H2, C2H4, CH2O, CH3OH, CH2=C=O, CH3CHO, and CH2CHOH. In the DME flame, the concentration of the C1 species is much higher than that of the C2 species, i.e., C1 intermediates tend to form rather than C2 intermediates in a DME flame. In addition, formaldehyde is the dominant C1 species in each flame. The concentrations of C2 species like ethylene, acetaldehyde, acetylene, and ketene in the ethanol flame are remarkably higher than that found in the DME flame.

NiCo2O4 nanoparticles were synthesized using a sol-gel method. Their structures and morphologies were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Results indicate that NiCo2O4 has a spinel structure and an average diameter of around 15 nm. The catalytic behavior of NiCo2O4 for H2O2 electroreduction in alkaline medium was investigated by linear potential sweep and chronoamperometry. NiCo2O4 shows considerable activity and stability for the electrocatalytic reduction of H2O2. The electroreduction occurs mainly via a direct pathway at H2O2 concentrations lower than 0.6 mol·L-1. An Al-H2O2 semi-fuel cell was constructed using NiCo2O4 as the cathode catalyst. The cell displays an open circuit voltage of 1.6 V and a peak power density of 209 mW·cm-2 at a current density of 220 mA·cm-2 running on 1.0 mol·L-1 H2O2 at ambient temperature.

Dithio-N,N'-dimethoxypropyldipropionamide (DPDA) was investigated as a corrosion inhibitor for mild steel in 1 mol·L-1 hydrochloric acid using weight loss test, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), quantumchemical study, and Raman spectroscopy. The weight loss test results showed that DPDA was an excellent inhibitor for mild steel in acid media with an inhibition efficiency of 90.2% at the DPDA concentration of 1×10-3 mol·L-1. The polarization curves indicated that DPDA behaved as a mixed-type inhibitor while the single capacitive loop in the Nyquist plots revealed that the corrosion was a charge transfer controlled process. Inhibition efficiencies increased with the increase of DPDA concentrations, and the values of the inhibition efficiencies, obtained from the weight loss test, potentiodynamic polarization, and EIS, were in reasonable agreement. The absorption of DPDA was found to obey the Langmuir adsorption isotherm. The free energy of adsorption (△G0ads) was found to be -38.65 kJ·mol-1 and this value indicated that the adsorption was mainly chemisorption. This results from the sharing or/and transfer of electrons from the DPDA molecules to the metal surface to form coordinate bonds. The negative △G0ads value revealed that the adsorption of DPDA was a spontaneous process. Raman spectra suggest that DPDA adsorbed well onto the mild steel surface, and the quantumchemical study showed that the sulphur atoms in the DPDA molecule were the main active sites that resulted in absorption on the surface of the mild steel.

Steel pipe corrosion and scaling is a universal problem during the exploitation and use of geothermal resources. Scanning electron microscopy (SEM), energy dispersion spectrometry (EDS), X-ray diffraction (XRD), and electrochemistry test were used to characterize and investigate the scaling and corrosion behaviors of galvanized steel and 304 stainless steel pipes in a simulated geothermal water environment (Chinese central plain geothermal water). Results indicated that the scale formed on the 304 stainless steel pipe consisted of a needle-like substance and its main components were CaCO3 and MgCO3. The corrosion and scaling morphology of the galvanized steel pipe consisted of a ball-like substance and a needle-like substance with main components of Zn(OH)2, ZnO, and CaCO3. Corrosion and scaling often appeared simultaneously and acted synergistically during the formation and growth of the crystal nuclei and they prevented further corrosion of the galvanized steel pipe in geothermal water.

We investigated the use of a novel organic compound, 1,4,5,8-tetrahydroxy-9,10-anthraquinone (THAQ), and its oxidized product (O-THAQ) as cathode materials for lithium batteries. Cyclic voltammetric (CV) and charge-discharge tests of the two materials showed that during the discharge process a carbonyl-lithium enolate transformation and a hydroxyl-lithium enolate transformation occurred and the former reaction was reversible. The initial and 20th cycle capacities of O-THAQ were 250 and 100 mAh·g-1, respectively. These values were higher than those for THAQ, which showed that pre-oxidizing THAQ effectively improved its electrochemical performance. We propose a reason for this improvement.

The oxalate co-precipitation method was used to synthesize LiNi0.5Mn0.5O2. The effects of pH on the structure, morphology, and electrochemical performance of LiNi0.5Mn0.5O2 were investigated. The crystal structures and surface morphologies of the oxalate precursor and LiNi0.5Mn0.5O2 obtained at pH=4.0, 5.5, 7.0, 8.5 were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. The electrochemical performance of LiNi0.5Mn0.5O2 was evaluated by galvanostatic charge/discharge tests. Results show that the LiNi0.5Mn0.5O2 obtained at pH=7.0 has a smaller particle size, more uniform distribution, better layered characteristics and a smaller degree of cation mixing. Electrochemical tests confirmed that the sample obtained at pH=7.0 had the best electrochemical performance. At 0.1C rate, its discharge capacity reached 185 mAh·g-1 at the first cycle and remained over 160 mAh·g-1 after the 20th cycle. X-ray photoelectron spectroscopy (XPS) results indicated that the oxidation states of Ni and Mn in the LiNi0.5Mn0.5O2 obtained at pH=7.0 were +2 and +4, respectively.

Heavy oil is an extremely complex colloidal system where asphaltenes, as the core of micelles, are dispersed in the continuous phase of other saturated fractions. We used dissipative particle dynamics (DPD) to simulate the mesoscopic colloidal structure of heavy oil and to determine its effective factors. Coarse-grained DPD model molecules were constructed in accordance with molecular structures of the component fractions in heavy oil. A modification of the standard DPD program was used to calculate the motion of rigid polycyclic aromatic rings. The simulations show that the coarse-grained DPD models used in this paper predict the colloidal structure of heavy oil well. The ordered structure of micelles depends greatly on the molecular structure of asphaltenes. Higher ordered micelles contain highly fused aromatic rings whereas the alkyl side-chains exhibit dispersing behavior. Deflocculation of the resins was observed in the simulations. A critical concentration ratio for the resin and asphaltene exists. The coagulation of heavy oil occurs when the concentration ratio of resin and asphaltene is less than this critical value.

Epigallocatechin-3-gallate (EGCG) was successfully extracted from Huangshan green tea using an ion-precipitation and extraction technique. In the Tween 80/EGCG/H2O system, the critical micelle concentration of Tween 80 and the hydrodynamic radius of the Tween 80 micelles increase with increasing the EGCG concentration. As the concentration of Tween 80 increases, the intrinsic UV-Vis absorption and fluorescence intensities of EGCG increase, but the electrochemical diffusion coefficients of EGCG and Tween 80 decrease. We discuss the location of EGCG in the micelles.

Poly(6-dodecyl-2-(acrylamidomethoxy)-1,3,6,2-dioxaza borocane) (PADB) is a novel amphiphilic polyborate. The surface activity of the polyborate PADB with various weight-average molecular weights (Mw) in an aqueous solution was measured by surface tension methods. Using regular solution theory, the interaction between PADB and sodium dodecylbenzene sulfonate (SDBS) in 0.5 mol·L-1 NaCl aqueous solution was studied and compared with the monomeric ADB/SDBS mixed system. Results showed that the Mw of the polyborate PADB ranges from 1.5×104 to 3.5×104. The increasing Mw of PADB raises their critical micelle concentration (cmc) in aqueous solutions, however, the surface tension at cmc (γcmc) can also reach about 31 mN·m-1 (298 K), which indicates excellent surface activity. By PADB addition, two transitions occurred in the curves of the surface tension (γ) vs logarithmconcentration of SDBS (lgcSDBS) and were labeled c1 and c2, respectively, and with c1<c2<cmcSDBS. The surface activity of the SDBS aqueous solution increases with PADB addition and the reduction of its Mw. The PADB solution can be regarded as a special monomeric ADB solution. The micellization parameters of the PADB/SDBS mixed solution were calculated by regular solution approximation. The interaction parameter βm value of the PADB/SDBS mixed micelles is about -2.4 - -4.7, the activity coefficient f1m<1, demonstrating a strong synergistic interaction between PADB and SDBS. |βm| reaches a maximum when the molar fraction (x1) of the monomeric ADB unit of PADB in the mixed surfactants is 0.47. By comparison to the monomeric ADB/SDBS mixed system, the PADB/SDBS system possesses a larger |βm| value when x1 is below 0.8 and a stronger interaction effect is apparent. As x1 increases, the molar fraction (x1m) of the monomeric ADBunit of PADBin the PADB/SDBS mixed micelles increases linearly but this increase is less than that of the monomeric ADB/SDBS mixed system.

TiO2 catalysts deposited on activated carbon (TiO2/AC) were prepared by sol-gel and dip-hydrothermal methods to investigate the effect of preparation methods on the structure and catalytic performance of TiO2/AC catalysts. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and nitrogen adsorption. Results show that the TiO2 produced by the sol-gel method consists of irregular fragments coated onto the carbon surface and that the dip-hydrothermal method leads to nanorods being deposited onto the AC surface. The mesoporous and microporous specific surface areas of the TiO2/AC samples prepared by the dip-hydrothermal method were larger than those of the sol-gel samples, and the diameters of the TiO2 particles prepared by the former method were smaller. The performance of the TiO2/AC composite photocatalysts was evaluated by the degradation of methyl orange (MO). We found that 600 ℃ was the optimal temperature for the calcination of TiO2. Furthermore, the photocatalytic activities of TiO2/AC samples prepared by the dip-hydrothermal method were obviously better than those prepared by the sol-gel method.

Salicylic acid (SA), the active ingredient of aspirin, is effective in various medical treatments such as cosmetology and anticancer therapy. We investigated the photophysical and photochemical behavior of SA using 266 nm laser flash photolysis. Results demonstrate that SA can be photoionized and photoexcited by 266 nm photons to give SA+· and 3SA*. SA is highly photosensitive and can be photoionized via a monophotonic process with a quantum yield of 0.21. Under the aerobic conditions we find that in cells, hydrated electrons easily combine with oxygen to generate O-·20 , which can kill cancer cells. SA+·can be converted into neutral radicals by deprotonation and its pKa value is 2.95. SA also can be oxidized by SO-·4 and the rate constant is 2.28×109 L·mol-1·s-1, which further confirms the photoionization ability of SA. In addition, SA can be excited to 3SA*, which then generates 1O2*. This research provides introductory theory for the potential of SA to be used as an anticancer drug.

The absorption spectrum of the N2O molecule in the wavelength range of 143.6-146.9 nm was measured under the jet-cooled condition by using the high resolution vacuum ultraviolet radiation, which was generated by resonance-enhanced difference-frequency mixing, corresponding to the C1∏←X1∑+ transition. Three vibrational bands were observed with frequency intervals of 521 and 482 cm -1, and they were superimposed on a wide absorption background. Previous high-level quantum chemical calculations indicate that the C1∏ state of N2O is dissociative along the N—O elongation, while it is bound along the N—N bond stretching or N2O bending. Therefore, the observed vibrational progression is a Feshbach resonance of the dissociative transition state. From an anti-Fourier transformation analysis, the recurrence period of the unstable periodic orbit of the Feshbach resonance was found to be 61 fs and the corresponding vibrational frequency was 546 cm-1. Since this vibrational frequency is close to the frequency of the bending motion, the unstable periodic orbit is mostly composed of the bending motion of the C1∏ state coupled with dissociation. The N—N stretching vibration does not participate in its formation. Therefore, we describe the excitation-dissociation dynamics of the C1∏state of N2O clearly.

This article reviewed recent progresses in the design of a new class of chemical oscillators and developed a generic model that could qualitatively reproduce those photochemical oscillations seen in experiments. The two oscillators discussed in this report are based on the photolysis of 1,4-benzoquinone and its derivatives, in which external illumination is vital in initiating and sustaining the reaction processes. Nonlinear behavior in these two photo-controlled chemical oscillators are analyzed as a function of light intensity and the initial concentration of reagents including 1,4-benzoquinone, 1,4-hydroquinone, 2-methyl-1,4-benzoquinone, bromate, and sulfuric acid. A generic model proposed initially for the uncatalyzed bromate-aromatic compound reactions was modified here to account for the photolysis of 1,4-benzoquinone or 2-methyl-1,4-benzoquinone. The modified model qualitatively reproduced chemical oscillations and their dependence on light intensity.

meso-substituted porphyrin derivatives show great potential for use as red light-emitting materials. We used density functional theory (DFT) with the B3LYP method to optimize the porphyrin derivatives Zn-5,10,15,20-tetra(2-[thiophen-2-yl]thiophene)porphyrin (SPZ) and 5,10,15,20-tetra(2-[thiophen-2-yl]thiophene)porphyrin (TSP) with the 2-[thiophen-2-yl]thiophene (S) group as an energy transport donor. Based on the optimized molecular structures, the ionization potentials (IP), electron affinities (EA), hole extraction potentials (HEP), electron extraction potentials (EEP), as well as hole and electron reorganization energy (λ) were calculated to investigate the charge injection and transport properties. We used the time dependent density functional theory (TDDFT)/B3LYP//6-31G(d) method to calculate the electronic absorption spectra of SPZ and TSP. Then the lowest excited singlet state (S1) of SPZ and TSP were optimized by the ab initio configuration interaction singlets (CIS) method. The fluorescence spectra of SPZ and TSP were calculated by the time dependent Hartree-Fock (TDHF) method. These theoretical calculations indicated that the introduction of the S groups significantly affected the photophysical properties of the porphyrin, especially the electron injection and transport properties.

Density functional theory (DFT) and the configuration interaction with single excitations (CIS) method were used to optimize the ground state and excited state structures of five indolocarbazole molecules using the 6-31G(d,p) basis set. Based on their geometric structures, the absorption and emission spectra were calculated using time-dependent DFT (TD-DFT) with the same basis set and employing the polarizable continuum medium model (PCM). There are obvious differences in the emission spectra of these isomers as isomer 5 has larger oscillator strength in its emission spectrum, but its transition energies are the lowest among the isomers. The emission peak value of isomer 4 is the highest and the oscillator strengths of isomer 2 are the weakest from 250 to 450 nm. This is because the structures change from ground state to the excited state and the molecular orbital (MO) energy levels of these molecules are different. We also evaluated the nonlinear optical response (first hyperpolarizability) of this series of molecules. The calculated polarizabilities are similar but the static first hyperpolarizabilities (β0) are different. The β0 of isomer 2 is the largest among the compounds investigated.

The UB3LYP(B3LYP)/6-31+G** method of density functional theory (DFT) was employed to optimize the geometrical structures of bisimidazole and bistriazole benzenes and their derivatives. In addition, the nonlinear optical (NLO) coefficients of these systems were calculated with a finite field (FF) approach. Results show that the polarizability α and second hyperpolarizability γ values of all systems increase by introducing a donor NH2 or an acceptor NO2. For the diradical systems, the α and γ values of these systems with a donor are larger than those with an acceptor, which is opposite to the behavior of closed shell systems. By analyzing the effect of the diradical character and charge on the second hyperpolarizability, we demonstrate that the neutral molecule with intermediate diradical character exhibits a much larger γ value than the neutral closed shell molecule with a similar π conjugation property. The charged diradical systems with a donor and an acceptor exhibited larger γ values compared to the neutral diradical systems.

To explore the relationship between the structures and color of a quinoid lignin, quantum chemical calculations on fivemodel lignin compounds: 2-methoxy-1,4-benzoquinone (I), 1,2-benzoquinone (II), 4-acrol-2-methoxy-2,5-cyclohexadienone (p-quinone methide) (III), 5-methoxy-1,4-benzoquinone-2-oxygen anion (IV), 5-methyl-1,4-benzoquinone-2-oxygen anion (V) were performed using density functional theory at the B3LYP/6-311++G(2d,p) level. Optimized structures were obtained using ethanol as a solvent. Electronic spectra were produced using time dependent density functional theory (TD-DFT) at the same level. Results indicated that the maximumabsorption band in the visible region of the five model compounds was caused by a π→π* transition. The location of the maximum absorption band increased according to: III<I<II<IV<V. The oscillation strength at the maximum absorption band increased according to: IV<I<V<II<III. The quinone oxygen anion and the o-quinone model compounds that were produced during the bleaching process had average extinction coefficients (ε=1978-3197) at 445.47-552.36 nm in the visible light region, which would be an important color source for pulp after bleaching. Although the p-quinone model compound had an average extinction coefficient (ε=2094) and quinone methide had a large extinction coefficient (ε=31935), they did not have much effect on the color of the bleached pulp because of their comparatively short absorption wavelengths (414.91 and 407.90 nm, respectively).

This paper presents ab initio and density functional theory (DFT) calculations on the excited state intramolecular proton transfer (ESIPT) of a chromophore linked to 2-(2-hydroxyl-phenyl)-benzotriazole: {2-hydroxyl-5-[(p-nitro-styrene)yl-oxymethylene]-phenyl}-(2H-benzotrizole) (C1) and 4'-nitro-3,4-bis-[2-hydroxyl-(2H-benzotrizole)-benzyloxy]-stilbene (C2). We undertook a comprehensive investigation on the ground state and excited state changes of the ESIPT tautomers including their bond lengths, bond angles, Mulliken charges, dipole moments, frontier orbitals, and potential surface curves. A stable keto form (K) was not obtained for C1 in the ground state and a ground state intramolecular proton transfer (GSIPT) was, therefore, impossible. The hydrogen bond strength of the keto form (K*) was higher than that of the enol form(E*) at their excited states. When excited, the negative charge of the hydrogen donor was diminished while the negative charge of the hydrogen acceptor was enhanced. For the excited state of keto from, the electron density moved from a“phenol cycle”to a protonated heterocycle because of the HOMO→LUMO electron transition. A small energy barrier from E* to K*(ca 41 kJ·mol-1) was also observed. These results indicated that the possibility of ESIPT occurring was high for C1. For C2, stable structures for the EK(including keto and enol (E) forms simultaneously), 2K (including two keto forms simultaneously), and 2K* (the excited state of 2K) tautomers could not be obtained because of their high energies. As a consequence, the probability of intramolecular single or double proton transfer at the ground state or excited state intramolecular double proton transfer occurring was negligible. The low transition energy for 2E* (the excited state of 2E)→EK* (the excited state of EK) suggested that an excited state intramolecular single proton transfer was very possible for C2. UV-Vis absorption and fluorescence spectra were calculated and an ESIPT fluorescence emission with a large Stoke's shift was observed.

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Molecular structures, electronic spectra, and the thermal trans-cis isomerization of azobezene (AB) confined inside an armchair (8,8) single-walled carbon nanotube (CNT(8,8)) were calculated at the ONIOM(B3LYP/6-31+G*:UFF) level.We found that the entrance of azobenzene into CNT(8,8) was exothermic. The geometric parameters of azobenzene were not evidently affected by its confinement in CNT(8,8). Rotation of the phenyl rings was found to occur around the CN bond to some extent for both trans-and cis-azobenzene, which resulted in a twist configuration for the confined trans-azobenzene. The relative energy between the cis-and trans-azobenzene confined inside the CNT (8,8) increased by ca 8.1 kJ·mol-1 with respect to the case of the isolated azobenzene, suggesting that the relative thermal stability of the isomers of azobenzene is affected by their confinement in CNT(8,8). Electronic spectrum calculations showed that the lowest three singlet excitation energies of the confined azobenzene were blue-shifted by 1-5 nm in comparison to those of isolated azobenzene. By analyzing the potential energy surfaces, we found that the confinement in CNT(8,8) resulted in the increase in the activation barrier of the trans-to-cis isomerization of azobenzene but had little influence on the barrier of cis-to-trans backward reaction, which means that the confinement in CNT(8,8) restrained the trans-to-cis isomerization of azobenzene. The trans-cis isomerization process of the confined azobenzene mainly involved the bending of the CNN bond angle.

Density functional theory (DFT) calculations and periodic slab models were used to investigate the geometrical structures and surface energies of two different WC(0001) surfaces. The adhesion energies and separation work of Pt monolayer adhesion on the two WC(0001) surfaces at high-symmetry sites were calculated. Results show that the W-terminatedWC(0001) is favored and that theW-terminated surface with Pt monolayer adhesion at the hcp site is the most stable PtML/WC(0001) structure. On the basis of the above results, the adsorption behavior of the CO molecule and hydrogen atom on the PtML/WC(0001) surface was compared with those obtained on the Pt(111) surface with a surface structure similar to the PtML/WC(0001) surface. At a low coverage of 0.25 ML (monolayer), an obvious elongation of the Pt—C distance and a decrease in CO adsorption energy show that the PtML/WC(0001) surface, relative to the Pt(111) surface, exhibits much improved resistance to CO poisoning. The density of states further explains the bonding mechanism of CO and Pt atoms on different surfaces. At the same coverage, the maximum hydrogen adsorption energy on the PtML/WC(0001) surface is equal to or even slightly higher than that on the Pt(111) surface. This suggests that Pt/WC possesses od catalytic activity during the hydrogen oxidation reaction and is a promising alternative anode catalyst for proton exchange membrane fuel cells (PEMFC).

A simplified slab model was used to evaluate the effect of Pb content at the Al(100) surface on the chemical potentials and electrochemical dissolution potentials for pure Al and Al-Pb alloys using first-principles density functional theory calculations. Results indicated that the chemical potentials of the surface Al atoms, increased 0.13, 0.17, 0.57, and 0.64 eV, and their dissolution electrode potentials shifted -0.04, -0.06, -0.19, and -0.21 V with regards to pure Al when the content of Pb on the Al(100) surface was 1/9, 1/4, 1/2, and 3/4 monolayer coverages, respectively. The negative potential shift of the Pb-containing Al alloy indicates easier dissolution compared to the pure Al surfaces. The presence of Pb results in an inner relaxation of the Al surface atoms, and the surface structure as well as chemical environment changes. The chemical potential and the dissolution electrode potential are shown to be dependent on the chemical environment of the surface atoms. A Mulliken charge population analysis also indicate that at higher Pb content, the electron exchange between Pb and Al atoms increase, which results in a negatively charged aluminum surface and a reduced surface potential; the surface work function decreases, and this promotes the electrochemical corrosion of the aluminumsurface.

Within the framework of density functional theory (DFT), a free energy function was formulated in terms of modified fundamental measure theory (MFMT) for hard sphere repulsion and statistical mechanic theory with the weighted density approximation (WDA) for polymerization.Achemical potential for ABg hyperbranched polymerization fluids was determined and an expression of the density profiles of the polymerization fluids confined in parallel plates was derived. The influence of the reaction conversion, the volume fraction, and the number of B-kind functional groups on density profiles was discussed. Furthermore, the relationship between the reaction conversion or the plate width and solvation forces was also analyzed in terms of density profiles.

We proposed a periodic interaction model for the magnesium-tin layered double hydroxides, Mg3Sn-LDHs-yH2O. Based on density functional theory, the geometry of Mg3Sn-LDHs-yH2O was optimized using the CASTEP program. The distribution of CO2-3 and H2O in the interlayer and the supermolecular interaction between host and guest was investigated by analyzing the geometric parameters, charge populations, density of states, and stepwise hydration energies. Results showed that when CO2-3 and H2O were inserted into the layers of [Mg6Sn2(OH)16]4+, there were strong supermolecular interactions between the host layer and the guests, including hydrogen-bonding and electrostatic interactions. Hydrogen-bonding was superior to the electrostatic interaction in the hydration process. In general, layer-water (L-W) type and layer-anion (L-A) type hydrogen bonding were stronger than anion-water (A-W) type and water-water (W-W) type hydrogen bonding. In Mg3Sn-LDHs-yH2O (y=0-3), the interlayer distance increased then decreased slightly with an increase in the number of interlayer water molecules. At y=0 or 1, the plane of CO2-3 and water was parallel to that of the layer and they were approximately in the middle of the two layers. At y=2 or 3, the guests were not parallel to the host layer and their distribution was random. The impact of CO2-3 was more significant than that of H2O on the density of states of the system. Therefore, the interaction between the layer and CO2-3 was stronger than that between the layer and H2O. The absolute value for the hydration energy decreased gradually with an increase in the number of water molecules. This indicated that the hydration of Mg3Sn-LDHs reached a definite saturation state.

We studied the reaction of CH3SH+H theoretically using a dual-level direct dynamics method. Three reaction channels: two H-abstraction (from the —SH and —CH3 groups) and one substitution channels, were found. Optimized geometries, frequencies, and energies of the stationary points as well as extra points along the minimum energy path were calculated at the MP2/6-311+G(d, p) level of theory. The potential energy profiles were then refined by single-point energy calculations at the G3(MP2) level. Furthermore, the rate constants of all three channels were evaluated by canonical variational transition state theory (CVT) with the small-curvature tunneling effect correction (SCT) over the wide temperature range of 220-1000 K. These calculations show that H-abstraction from the —SH group (R1) is the major channel for the title reaction over the whole temperature range. The substitution channel (R3) is a minor pathway at low temperatures and becomes more important as the temperature increases. This would be a competitive channel at high temperature while the contribution of H-abstraction fromthe—CH3 group (R2) to the overall rate constant is almost negligible because of its high energy barrier. The calculated CVT/SCT rate constants agree well with the available experimental values. The three-parameter rate-temperature expression for the total reaction over the whole temperature range of 220-1000 K is shown to be k=5.00×10-18T2.39exp(-119.81/T), which may be a useful expression for future experiments.

A neural network approach was used to correct three parameters (a0, ax, and ac) in the B3LYP method for constructing a new B3LYP exchange correlation functional. A three-layer architecture which consisted of an input layer, a hidden layer, and an output layer, was adopted in the neural network. The total number of electrons, spin multiplicity, dipole moment, kinetic energy, quadrupole moment, and zero point energy were chosen as the most important physical descriptors. In this work, 296 energy values were randomly divided into two subsets: 246 energy values were used as the training set to determine the optimized structure of the neural network and the optimized synaptic weights; 50 energy values were used as a testing set to test the prediction capability of our neural network. Three modified parameters a0, ax, and ac that were obtained from the output layer were used to calculate thermochemical data such as the atomic energy (AE), ionization potential (IP), proton affinity (PA), total atomic energy (TAE), and standard heat of formation (△fHΘ). The newresults obtained, based on the neural network approach, are much better than the results calculated using the conventional B3LYP/6-311+G(3df,2p) method. Upon the neural network correction, the overall root-mean-square (RMS) error for the 296 species decreased from41.0 to 14.2 kJ·mol-1.

Based on the order rule for substituents on a chiral carbon atom, a novel structural parameter, the molecular chiral index (wj ), was investigated in this paper. A quantitative structure-retention index relationship (QSRR) between the retention index (RM) froma chiral thin-layer chromatogramfor 18 chiral organic acids (8 hydroxyl acids and 10 amino acids) and wj, an electrotopological state index for atom types (En) was investigated using multivariate statistical regression. Using leaps-and-bounds regression analysis, an optimal four-parameter QSRR model was set up. The traditional correlation coefficient (R2) and the cross-validation correlation coefficient (Q2) of the leave-one-out (LOO) method were 0.969 and 0.943, respectively. Results demonstrate that the model is highly reliable and that statistically it has a od predictive ability. From the four parameters (wj, E13, E16, E17) of the model, the two-dimensional molecular structure characteristics (such as =O,—OH, —NH2) and the chiral characteristics are shown to be decisive factors that affect the retention index for the chiral organic acids. Results also show that the new parameters wj and En are rational and efficient in the determination of retention indices of chiral organic acids. Therefore, this paper provides an effective method to predict the retention indices of chiral organic acids.

The active components in salvia miltiorrhiza bunge (danshen) include danshensu, labiatenic acid, and tanshinone, and they are known to be key compounds for danshen's blood-activating effect in traditional Chinese medicine. Studies show that these compounds have some common scaffolds. A systematic investigation was conducted to locate the targets of these active components among proteins with reported crystal structures. A structural informatics knowledgebase derived from protein structure and ligand-binding mode information was employed in this investigation. Furthermore, docking methods were used to rationally discover the relationship between the scaffold characteristics and the binding ability with the proteins. Results indicate that the active components comprehensively inhibit the metabolic network of adrenaline, which is a strong endogenetic cardiovascular activator. Consequently, adrenaline and its derivatives are accumulated and blood circulation is activated. We propose that key enzymes in the metabolic pathway of adrenaline including phenylethanolamine N-methyltransferase, catechol O-methyltransferase, and monoamine oxidases are targets for the active components in danshen. This research aids in the understanding of the mechanismof danshen's activating blood action.

We performed molecular docking andmolecular dynamics (MD) simulations to investigate the interactions between fentanyl analogs and μ-opioid receptors. The AutoDock 4.0 program was used to perform the docking and homology modeling of the μ-opioid receptor structure. MD method as implemented in the GROMACS program was used to model the twelve fentanyl receptor a nists and the μ-opioid receptor protein compounds in water and to optimize the docking complex structure. Based on MM-PBSA methods, the APBS program was used to calculate the binding affinity of the complexes and the binding contant of receptor and liqand (Ki) values determined using MM-PBSA were consistent with the experimental values. Our predictions of compound activity sequences were, therefore, correct. The MD simulations of these complexes revealed that the protein structures in the complexes differed substantially from the structures of the ligand-free receptors. The backbone of the intracellular region segments IL2, IL3 and TM4 showed that the skeleton conformations had changed significantly. Different compounds may influence the receptor structure differently. Compounds with high activities may enhance binding flexibility in certain protein structural regions. These facts imply that fentanyl analogs may result in μ-opioid receptors changing to an active conformation after receptor binding. Physiologic effects may thus be triggered by a mediating signal transduction and by the activation of the G-protein.

 In this study, we demonstrate that the trifluoromethyl-containing 1,2,3-triazole derivative (TF-TZ) inhibits mushroom tyrosinase. TF-TZ could inhibit the monophenolase and diphenolase activities and the inhibition is reversible. IC50 values of 30.4 and 34.5 μmol·L-1 were estimated for the monophenolase activity and the diphenolase activity, respectively. TF-TZ could extend the lag period of the monophenolase activity. Kinetic analysis showed that parabolic-competitive inhibition of TF-TZ occurred on diphenolase. We proposed that two TF-TZ molecules combined with free tyrosinase to formenzyme-inhibitor complexes (EI and EI2), and the inhibition constants (Ki1 for EI and Ki2 for EI2) were 76.9 and 9.71 μmol·L-1, respectively. Moreover, the UV-Visible spectrum of a mixture of tyrosinase and TF-TZ exhibited a characteristic shoulder peak that could be assigned to chelation of TF-TZ to the active site.

Two active components (psoralen and isopsoralen) of Chinese herbs having similar structures were studied. A combination of intrinsic fluorescence spectroscopy, ultraviolet (UV) spectroscopy, circular dichroism(CD), and Fourier transform-infrared (FT-IR) spectroscopy were used to characterize the binding between the two coumarins and human serumalbumin (HSA). The results fromdifferent spectra indicated qualitative and quantitative changes of the secondary structure of HSA. The thermodynamic functions, enthalpies (△H) and entropies (△S), were calculated from fluorescence titration experiments using Vant's Hoff equation. The binding constants and number of binding sites for the drug interactions of both drugs with HSA were evaluated using the relevant fluorescence data at different temperatures (296, 303, 310, and 318 K) and applying modified Stern-Volmer and Scatchard equations. Forster theory of dipole-dipole energy transfer was used to determine the distance between the protein residue and the bound drugs. The competitive experiments suggested that psoralen and isopsoralen bound strongly to HSA and the primary binding site for both drugs was located at site II of HSA.

The vacuum thermal evaporation of KSCN onto the surface of a Ag electrode results in a AgK2(SCN)3 composite film through an interfacial reaction between the Ag and KSCN films. Visible spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and X-ray diffraction (XRD) were used to investigate the film. The Al/AgK2(SCN)3/Ag device exhibited reversible electrical bistability with a resistance ratio of 106 and it was successively operated in a“write-read-erase-read”mode. The reversible writing and erasing performance of the device is attributed to the formation and rupture of conducting channels through the AgK2(SCN)3 composite layer. By fitting the currentvoltage curves, the low-and high-resistance states are shown to follow ohmic conduction and space charge limited current conduction, respectively. We suggest that the annihilation of conducting channels is caused by the electrochemical ionization together with the Joule heating effect.

Pd-Ag alloy nanoparticle chains were fabricated on carbon fibers using three-pulse electrodeposition method. Pd-Ag alloy nanoparticle chains on carbon fiber surfaces can be used as hydrogen sensors. Scanning electron microscopy (SEM) andX-ray spectroscopy (EDX) were used to characterize the morphology and composition of the alloy nanoparticle chains. A CHI660B electrochemical workstation was used to evaluate the hydrogen sensing ability. Results show that Pd-Ag alloy nanoparticle chain arrays with a silver content of 16.0%-25.0%(w) were obtained in the electrolyte with an ion concentration ratio (molar ratio) of palladium to silver of 15:1. At -1.0 - -1.5 V nucleation took place within 5-40 ms and at -0.25 - -0.35 V growth was allowed for 200-300 s. The sensors responded to hydrogen gas at concentrations of 0.30%-5.00% (φ, volume fraction) at roomtemperature. The fastest response time was about 300 s and 31.0% sensitivity was obtained. The response current was linearly proportional to the hydrogen concentrations from 0.30% to 1.20%(φ). The current signal did not change with the hydrogen concentration larger than 4.00%. These hydrogen sensors show od reproducibility at hydrogen concentrations lower than 3.50%.

Co2+ doped ZnS semiconductor quantum dots (QDs) were synthesized in an aqueous solution at 70 ℃ using citric acid (CA) or mercaptopropionic acid (MPA) as a stabilizer. The as-prepared undoped and the Co2+ doped ZnS quantum dots (QDs) were characterized by UV-Vis spectrum, photoluminescence (PL) spectrum, X-ray powder diffraction (XRD), cyclic voltammetry, and transmission electron microscopy (TEM).We studied the dependence of the doped ZnS quantum dots photoluminescence on the dopant and the dopant concentration. Results show that Co2+ ions are doped mainly on the ZnS nanocrystal's surface and as a result, the band-edge and surface defect emissions of the ZnS quantum dots are substituted by a Co2+-related PL emission. The best photoluminescence intensity was obtained for the 5%(molar fraction) cobalt doped ZnS quantumdots with MPA as the stabilizer. The cobalt doped ZnS quantum dots are 4 nmin diameter and are monodispersive.

In this paper, we describe multilayer ZnOthin films prepared by spin-coating precursor solutions of different concentrations. The multilayer ZnO thin films were employed as active layers in thin film transistors (TFTs). A TFT device based on a three-layer ZnO film prepared using precursor concentrations of 0.25, 0.10, and 0.05 mol·L-1 showed a higher mobility of 0.02 cm2 ·V-1·s-1 compared with a TFT device (mobility of 0.013 cm2 ·V-1·s-1) prepared using precursor concentrations of 0.05, 0.10, and 0.25 mol·L-1. Atomic force microscopy (AFM) showed that the former film with a root mean square (rms) of 3.95 nm for the roughness was smoother than the latter with a rms of 4.52 nm. We demonstrate that the roughness of the ZnO film plays an important role in the properties of the semiconductor film. A smoother film allows better contact between the source/drain and the active layer. In TFTs, charge carriers transport in the ZnO grains only near the ZnO/SiO2 insulator layer interface and the crystallinity of the initially formed layer of the filminfluences the performance of the TFT. X-ray diffraction (XRD) patterns showed that the initial layer formed was polycrystalline for the former film and amorphous for the latter. Our work demonstrates that the roughness of the semiconducting film and the crystallinity of the initially formed layer influence the properties of the multilayer semiconducting film.

Epitaxial graphene layers were successfully grown onto Si-terminated 6H-SiC(0001) substrates by thermal annealing using an ultrahigh vacuum molecular beam epitaxy(MBE) chamber. The morphology and  structure of the samples annealed for different time were characterized by reflection high energy diffraction (RHEED), Raman spectroscopy, atomic force microscopy (AFM) and near edge X-ray absorption fine structure spectroscopy (NEXAFS). The graphene diffraction steaks were found in the RHEED patterns for all samples. AFM results showed that as the annealing time increased, the thickness of the graphene layers increased and the surface morphology appeared smoother with the out-of-order voids reduced. Raman results showed that the G peak and the 2D peak of graphene were obviously blue-shifted compared to those of highly-oriented pyrolytic graphite (HOPG). At longer annealing time, the amount of blue-shift decreased. C K-edge NEXAFS results revealed that the intensity of the resonance absorption peaks for 1s→π and 1s→σ for the sp2 hybridized C atoms increased when the samples were annealed over longer periods. The 1s→π peaks of these samples were at higher energies compared to those of HOPG.

Acid orange 7 (AO7)-pillared Zn/Al layered double hydroxides (Zn/Al-AO7 LDHs) were successfully synthesized using the co-precipitation method. In this experiment, synthetic parameters such as the pH value and the ratios of raw materials were varied to study their influences on the structure of Zn/Al-AO7 LDHs. Sample characterization was carried out using X-ray diffraction (XRD), thermal analysis (TG-DTA), and Fourier transform infrared (FT-IR) spectroscopy. The molecular geometries of the Zn/Al-AO7 LDHs model were calculated at the B3PW91/6-31G(d, p) level and the gallery heights were 2.33 nm, which agreed well with the experimental results. Formamide was chosen as a solvent for the layered double hydroxide delamination experiment. XRD patterns showed that all the layers had been delaminated.