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Electrochemical behaviors and redox properties of polyoxometalate (POM)/SBA-15 mesoporous hybrid materials, prepared by co-condensation and post-synthesis, were investigated using carbon paste electrodes by cyclic voltammetric measurement. In acetonitrile solution and the range of potentials studied, the cyclic voltammograms of free species in the solution and the same species loaded on mesoporous silica by impregnation showed two one-electron waves corresponding to redox processes of WVI. For the same POM species bonded covalently onto mesoporous silica, however, the current of first wave increased and reduction potentials shifted towards positive direction as compared with the impregnated sample, indicating that these species not only retained the redox property of POM perfectly, but also possessed more intense oxidbillity than the impregnated POM species. The plots of current versus scan rate showed that the redox processes of the hybrid samples were surface-controlled at lower scan rates but diffusion-controlled at higher scan rates. It was also found that the oxidbillity of tungstophosphate was higher than that of tungstosilicate; and the similar electrochemical behaviors were presented for the hybrid samples prepared by both routes.
Six possible reaction channels for the reaction of HNCX (X=O, S) and F have been studied at the G3B3//B3LYP/6-311++G(d,p) levels. The breakage and formation of the chemical bonds in the reactions have been discussed by the topological analysis method of electronic density, and the T-shaped structure transition states and ring-shaped structure transition regions have been found in the reactions.
The ground states of TiO2 molecule under different electric fields are optimized using density functional theory DFT/B3P86 at 6-311+G* level. Based on the optimized molecular geometries, the transition wavelengths and oscillator strengths of the first six different excited states for TiO2 molecule are studied by employing the revised hybrid single-excitation configuration interactions, i.e. CIS-B3P86 method with basis set 6-311+G*. It is shown that the many excited states of TiO2 molecule satisfied the selection rules of electric dipole radiation, manifold transition spectra would come forth when transitions from excited states to ground state of TiO2 molecule took place. Therefore, the new functional materials at molecular dimension level will enhance the sunlight absorption ability. When the external electric field strengths become stronger, the energy gaps between the highest occupied molecular orbital HOMO and the lowest unoccupied molecular orbital LUMO will become smaller and the electrons of the occupied orbital are more apt to be excited to the virtual orbital. The transition wavelengths of the first six excited states for TiO2 molecule shift from ultraviolet region to visible one, the longest wavelength achieves 589 nm. Therefore the luminescence spectrum of TiO2 molecule can be expanded in visible light region by the use of external electric fields.
To investigate how many water molecules may induce the zwitterionic glycine isoenergetic with respect to the neutral form, mp2/6-31++g**//b3lyp/6-31++g** method has been applied to study the micromechanism of the glycine-H2O interaction. It is found that the answer is five water molecules which confirms the experimental result. The most stable conformation of pentahydrated zwitterionic glycine com- plexes is a pair-chains structure, whose energy is near to the energy of the most stable pentahydrated neutral glycine conformation (the error is only 2.26 kJ/mol), so they can coexist. Via proton transfering, a pentahydrated neutral glycine complex can convert into the corresponding pentahydrated zwitterionic glycine com- plex. There are two kinds of proton transfer route in glycine-H2O system, one is “direct proton transfer” and the other is “water-assisted proton transfer”. In the proton transfer process of the corresponding pair-chains structures, there is a lower energy barrier or no barrier, and the reaction can proceed spontaneously.
Enthalpy relaxation dynamics of amorphous D-sorbitol has been studied by differential scanning calorimetry (DSC). A series of specific heat capacity curves (cp(T)) were measured on heating (10 K•min-1) after cooling the sample at different rates ranged between 0.5 and 20 K•min-1. A phenomenological model of enthalpy relaxation based on the evolution of configurational entropy (GR model) was used to simulate the experimental data. All the experimental traces can be fairly well reproduced by this model, no matter whether a metastable limit state of relaxation process is assumed. The physically reasonable model parameters seemed to be independent of thermal history, except the nonexponential parameter, which increased slightly as the cooling rate increasing. The model parameter sets obtained under lower cooling rates show better predictive ability than those obtained under higher ones. Since the calculated relaxation time value is strongly dependent on the “fixed parameter” value, the predictive ability to the cp(T) curves is not the only criterion for the determination of relaxation time. Take the limit fictive temperature as Tg in the fragility calculation leads to an significantly smaller value than the published data.
We determined the structures of amorphous diboron trioxide and sodium pentaborate hydrate by X-ray diffractometry. Radial distribution functions (RDF) of those samples were obtained from precisely diffraction data processing. Their short-range ordered structures were determined by model design and quantitative calculations. In amorphous diboron trioxide hydrate, 75% of boron atoms construct planar six-membered boroxol ring and the interatomic distance and the interactions numbers of intra-ring ortho-B—O, meta-O—O, meta-B—B and para-B—O were listed out, where boron-oxygen branched-chain intersects with the plane at a terminal-oxygen with a intersect angle of 125°±15°. The basic structure unit of non-crystalline sodium pentaborate hydrate is formed by two planar six-membered boroxol rings deformed, composed of two boron-oxygen triangles (B△) and a boron-oxygen tetrahedron (B□), through the shared B□. The highly ordered intra-anion interactions are the upmost interactions. Six coordinated Na+ connects with the terminal-oxygen of pentaborate to form a contact ion pair with a characteristic distance (B—Na) of 0.330 nm.
Micro/nano Ni-Fe-P wave absorbing materials were prepared on the surface of Nocadia pretreated by electroless plating technique. The morphology, component, structure and magnetic property were characterized by SEM, EDS, XRD and VSM. The results clearly demonstrated that one-step method was in a condition to deposit on the surface of Nocadia, and the surface of plating was roughed with the increase of the spherical particles and decomposition products due to the effects of the load, the quality of plating and the utilization of electroless solution were the best when the load was 80 mL. The average contents of Ni, Fe and P element of the metal layer with 80 mL load (w) were about 83.17%, 6.12% and 10.71%, respectively. The magnetic property was changed little by increasing of the load, and the plating was amorphous. The electromagnetic parameters were measured by VNA, the results showed that the reflection loss could reach 27 dB at the frequency of 10~12 and 15~17 GHz when the thickness was 2 mm.
The preparation of porous gas diffusive electrodes is the key to an excellent electrochemical sensor for determination of formaldehyde, in which the microstructure of catalyst direct affects the response capability. The catalysts of gold nanoparticles/activated carbon and gold nanoparticles/carbon nanotubes were prepared by sodium citrate reduction method. The gas diffusion porous electrodes have been obtained and characterized by SEM (scanning electron microscopy). The formaldehyde gas sensor C had the best response when formaldehyde concentration was 0.24 and 0.63 mg/m3. The linear regress equation was y=10.515x+4.4049 (R2=0.9917) when concentration of formaldehyde ranged from 0.1 to 0.84 mg/m3, and the response time was about 80 s. The relationship between microstructure of the gas diffusion electrode and response characteristic of formaldehyde was studied.
Self-consistent field theory was employed to calculate the morphology of A/B/A-b-B/(A-b-B)4 quaternary blending system, which can be used for simulating the phase structure of high impact polypropylene (HIPP). We focused on the influence of chain length as well as the volume fraction of each component on the phase behavior of blends and confirmed that the system can phase-separate into various core-shell structures.
The research on the biological effect of rare earth compound has aroused wide concerns. In this paper, the results reveal that nano Eu2O3 can be internalized by live HEK-293T cells and accumulate in the perinuclear region in (Dulbecco s Modified Eagle Medium) DMEM with 10% (Fetal bovine serum) FBS by laser scanning confocal microscope. In vitro culture conditions, the effects of nano Eu2O3 on cell viability and the cell cycle were investigated using flow cytometry. The results showed that cell activity was free from nanoparticles with concentration less than 200 μg•mL-1. When nanoparticles concentration is more than 400 μg•mL-1, the cell activity was inhibited. Eu2O3 nanoparticles at low concentration (≤50 μg•mL-1) had no effect on the cell cycle, while high concentrations (≥200 μg•mL-1) cell cycle was significantly inhibited, which showed DNA synthesis in the late stagnation. These results indicated that nano Eu2O3 on HEK-293T cells have obvious biological effects.
The Li-rich cathode materials Li[CoxLi(1/3-x/3)Mn(2/3-2x/3)]O2 with different Co contents (x=0.4, 0.5, 0.6) were synthesized by modified Pechini method. The results of XRD confirmed that the crystals of the Li-rich compounds possess layered structure and have good crystallinity. The initial discharge capacities of the compounds are high between 200~220 mAh/g, increasing with the increase of Co contents. The material with x=0.4 exhibits the best cycling property. The capacity retainment is about 75% after 50 cycles at 0.5 C (100 mA/g). The peak of Mn4+/Mn3+occurred below 3.5 V in the plots of dQ/dV, and the area of the peak increases with the cycle numbers. The results of the XRD during the cycling process show the layer structure of the Li-rich materials transfers to the spinel phase, and the impurities appears during the cycling, resulting in the capacity fade.
The catalytic activity of Ni3Al foils for methane steam reforming was investigated by isochronal test from 873 to 1173 K, and the stability at 973 K for 20 h was also studied by isothermal test. Further, the effect of pretreatment, which was steam-oxidation then reduction at 873 K on the catalytic property, was also investigated. The results of catalytic reactions and the microstructure observations by SEM showed that the Ni3Al foils whether or not through the pretreatment all had certain activities and stabilities. The pretreatment significantly enhanced the catalytic activity of Ni3Al foils. Ni-enriched outer surface formed after the pretreatment was thought as the main reason of the enhancement. It was also considered that the Ni atoms moved from the matrix of Ni3Al foils to the outer surface during the reactions were attributed to the catalytic stabilities.
Rule of electrolyte volume change was studied when the all vanadium redox flow battery was running stably with a cation exchange membrane. Electric transfer of ions will make the volume change linearly with the changing of charge-discharge capacity, that is, the positive electrolyte will be less and the negative electrolyte will be more during the charge process, which will be reversed in the discharge process. The direction of net infiltration of vanadium ions is from the negtive electrolyte to the positive electrolyte, which will make the volume of positive electrolyte larger in a couple of cycles. The direction of net water transfer is the same as the vanadium ions.
The methotrexatum (MTX) was intercalated into the layered double hydroxides (LDHs) to form the MTX/LDH compounds, by the coprecipitation method in the alcohol-water mixed solvent (alcohol-water co-precipitation for short) and NaOH as precipitator. The influence of alcohol-water solvent on the structure of MTX/LDH compounds was systematically investigated by X-ray diffraction (XRD), transmission electron micrograph (TEM), fourier transform infrared spectroscopy (FTIR) and differential thermal analysis (DTA) techniques. The studies indicated that compared with the conventional coprecipitation method in water solvent, the morphology of the particles prepared by the alcohol-water coprecipitation was spherical shape with smaller size and had a good dispersion. MTX anions were intercalated into the LDH sheets as a delined monolayer and the declined angles changed with the variation of the volume ratio of ethanol to water. Our results showed that when the volume ratio of alcohol to water was 1∶3, the particles are the smallest and uniform without agglomeration. At last, the drug release rates with different particles size were studied in phosphate buffer and it showed that the smaller MTX/LDH nanoparticles have the longer release time than those of the larger ones.
Actin polymerization is coupled with the hydrolysis of adenosine triphosphate (ATP). The hydrolysates of ATP are adenosine diphosphate (ADP) and inorganic phosphate (Pi). Therefore, each protomer within the actin filament can exhibit three different nucleotide states corresponding to bounded ATP, ADP/Pi and ADP molecules. These protomer states cause the filaments to form different spatial patterns, which will change various properties of the filament. The related model has been made to simulate the process of polymerization, depolymerization and hydrolysis via Brownian dynamics simulations, where the time evolution of depolymerization and hydrolysis is described as a continuous-time Markov process. In this paper, we focus on how to realize the chemical equilibrium between two ends of the filament, and study the growth behavior of long filaments as a function of ATP-actin monomer concentration.
The rheological fluctuation behavior of apparent viscosity η with t was found in Mg-Al-Hydrotalcite-like compound/kaolinite (Mg-Al-HTlc/kaolinite for short) suspensions by steady shear experiment, and the influence of mass ratio of HTlc to kaolinite (R), steady shear rate (DL), pH, electrolytes and polymers was investigated. It was found that the fluctuation behavior would disappear when DL and the concentration of electrolytes were relatively high. The pH value and polymers would change the amplitude of the fluctuation behavior. The results were discussed on the basis of the interactions between the HTlc and kaolinite particles.
The reaction mechanism of the reaction N2O (1∑+)+CO (1∑+) → N2 (1∑+g)+CO2 (1∑+g) catalyzed by alkaline-earth metal cations 2Sr+ and 2Ba+ have been investigated by using the UB3LYP density functional theory (DFT, UB3LYP) with the relativistic effective core potential (RECP) of basis sets (SDD) for 2Sr+, 2Ba+ and the 6-311+G(2d) basis set for C, N and O on doublet energy surfaces. The geometries for reactants, the transition states and the products are completely optimized. All the transition states are verified by the vibrational analysis and the internal reaction coordinate (IRC) calculations. The results show both main reactions process in a two-step manner to products. NBO analysis has been used to discuss the structure of reactant-complexes, our calculated results for the title reactions are in close agreement with experimental observations.
Mechanical properties of cellulose Iβ crystal were studied using molecular dynamics. Firstly, mechanical properties of the cellulose Iβ crystal model offered by Nishiyama were calculated. By analyzing the mechanical parameters of cellulose Iβ crystal, it was found that the cellulose Iβ crystal was the anisotropic elastic material whose elasticity was much bigger in the direction of chains of cellulose molecules than other two directions and had good ductility. The Young s modulus also agreed with the data which was calculated by Tanaka. Subsequently, the mechanical properties of cellulose Iβ crystals were calculated under the transformer operating temperatures. The changes of mechanics parameters were not obvious under the transformer temperatures. The same law was also found when calculating the density of hydrogen bond in the crystals under different temperatures, but the standard deviation of the density of hydrogen bond became bigger when the temperature increased, reflecting the influence of temperature to the stability of cellulose crystals. Through analysis of density distribution in the direction of crystal layer, with the temperature increasing, the standardized crystal structure became weakened. Finally the movement of chains had been studied and found that the higher the temperature was, the more intensely the movement of chains were, which agreed with the result manifested by the density of hydrogen bond.
Dissipative particle dynamics (DPD) simulation method and experimental study were used to study the formation of starch microspheres (SM). Cyclohexane was selected as oil phase, amylose as aqueous phase, meanwhile Span60 and Tween60 as emulsifiers, respectively. It is shown from DPD simulations that the forming process of SM is consisted of four steps: (1) irregular dispersion of amylose and emulsifiers, (2) the formation of small aggregates, (3) the formation of microspheres aggregates, (4) stabilization of microspheres. The simulation results represent that the oil-aqueous volume ratio is the key influencing factor to the formation of microspheres aggregates. When the oil-aqueous volume ratio is smaller than 7, aggregate morphologies of the aqueous phase as lamellar, columnar, crisscross and ellipsoidal structures are observed. Microspheres are formed only when oil-aqueous volume ratio is 8, and the particle sizes are decreased with the increase of oil-aqueous volume ratio. And the experiments show that the microspheres can not get good sphericity when oil-aqueous volume ratio is 8, and the particle sizes are decreased with the increase of oil-aqueous volume ratio when the ratio is 10 to 20. The experimental results could be interpreted with the simulation results. DPD simulation provides an insight into the microstructure of SM and help to analyze the experimental results, which is helpful in synthesis of SM.
A series of quantum calculation have been done to investigate the excited state property of laser dye molecule LDS751 by density function theory. The possible configuration and processes have been predicted by the theoretical point of view. Two major isomization pathways which may have influence on the excitation spectral property have been analyzed, it is indicated that rotation corresponding to the bridge C—C bond and terminal C—N maybe the comparable reaction channels in the first excited state. The intramolecular charge transfer and the degree have been estimated by the comparison of the summary of the charge re-distribution during different function group in the excitation. The conclusion can give some evidence and support to the relative absorption and emission spectra in different time scale experimental investigation.
Silver nanoparticles were prepared by NaBH4 reduction procedure. An aptamer-modified Ag nanoprobe (AgSH-ssDNA) for thrombin was prepared. In the media of pH 7.0 Tris-HCl and KCl, the AgSH-ssDNA specifically combined with thrombin to form G-quadruplex and Ag cluster, which resulted in the resonance scattering intensity at 480 nm (I480 nm) increasing. As the amount of thrombin increased, the amount of Ag clusters increased, and the I480 nm value increased. At the same time, Ag/Au nanoparticles of different Ag/Au molar ratio were also prepared for the thrombin RS analysis. The results showed the Ag system had some advantages such as high sensitivity, wide linear range, low-cost, and the simplicity of nanoparticles preparation. Its increased intensity ΔI480 nm was linear to the thrombin concentration in the range of 0.14~11.5 nmol/L, with a regression equation of ΔI480 nm=19.1C+2.2, a correlation coefficient of 0.9833, and a detection limit of 17 pmol/L. This method was applied to detect thrombin in human plasma samples with satisfactory results.
A new immunoassay method for Carcinoembryonic Antigen based on fluorescence induced by laser and labeled with nanoparticles is presented. Core-shell SiO2 fluorescent nanoparticles were used as labels, “sandwich” model was used. Mouse anti-carcinoembryonic antigen (CEA) monoclonal antibody was immobilized on slides, then 1~2 µL CEA was added, and the other mouse anti-CEA monoclonal antibody labeled with nanoparticles was added, after CEA and antibody recognized, the fluorescent signal was quantified with an laser-induced fluorescence millimeter array detection platform based on optical fiber. The fluorescence intensity has a linear relationship with the concentration of CEA in the range of 1~80 pg, with the absolute limit detection of CEA being 0.3 pg. The relative standard deviation (RSD) for 5 parallel measurements of CEA (40 pg) was 5.5%.
The fingerprint chromatograms of the extracts from Compound Indigowoad Root Granule was established by HPLC-UV. Nineteen common peaks were found in fingerprint chromatograms of the extracts from Compound Indigowoad Root Granule and good similarities with correlation coefficients over 93% were found between the fingerprint chromatograms of the extracts from different sources. The main common peaks were identificated by HPLC-MSn. Pharmacodynamic studies have shown that the extract from Compound Indigowoad Root Granule had anti-viral activity. This method with desirable accuracy, stability and repeatability can be used for the quality evaluation of Compound Indigowoad Root Granule.
Under microwave assisted heating, uridine imprinted polymer was prepared rapidly using uridine as template, acrylamide (AA) as monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker. The results indicated that the polymerization time was shorten significantly, only one eight of the conventional heating. Infrared spectroscopy and scanning electron microscopy were used to characterize the structure and morphology of the imprinted polymer, and the results showed that the imprinted polymer was coated on the surface of silica microspheres successfully. Well-dispersed particles are observed and the thickness of the imprinted shell is about 100 nm. Combined with high liquid chromatography technique, on-line imprinted enrichment and determination of nucleotide ingredients from the extracting solution of isatidis root were performed successfully.
St-BA-AOS copolymer emulsion was synthesized via the preemulsified emulsion polymerization, with styrene (St), butyl acrylate (BA), and sodium alpha-olefin sulfonate (AOS) as the polymerizable emulsifier. Semi-continuous method of the polymerization was determined by measuring the reactivity ratios of AOS and two monomers. The influences of the feeding method, the reaction temperature, time and AOS amount on the emulsion polymerization were investigated, then the most suitable polymerizing conditions were obtained. The analysis of the profiles of IR, NMR, DSC and Laser particle size demonstrated that the copolymerization occurred among St, BA and AOS to generate P(St-BA-AOS) successfully, and hydrophilic sulfonic acid groups containing the copolymer were conducive to emulsion stability. Based on the study, the influences of the dosages of AOS on the latex solid content and average particle size were discussed. The result showed that with the increase of AOS amount, the latex solid content increased and average particle size of latex reduced, e.g., at the 2% mass amount of AOS 45.01% of the latex solid content, 74 nm of average diameter, 0.08 of particle size distribution and 23.17 ℃ of Tg were obtained. The results of TEM showed that the copolymer emulsion with smaller particle size and more uniform size distribution could be obtained by using polymerizable emulsifier AOS instead of the same amount of sodium lauryl sulfate.
The critical properties of square-well dimer with range λ=1.5 are calculated by grand ensemble Monte Carlo simulation. The critical temperature and density obtained with the help of histogram reweighting technique and finite-size scaling theory are and , respectively. Vapor-liquid equilibria properties far from the critical point are explored by hyper-parallel tempering method which can greatly improve simulation efficiency. The result of critical properties is much more precise than previous simulation result.
The interactions between Bcl-2 and three protoberberine alkaloids: berberine hydrochloride, jatrorrhizine and palmatine hydrochloride were studied by fluorescence spectroscopy. The binding constants and the number of binding sites were measured, respectively, and the quenching mechanism was proposed. The results indicated that the protoberberine alkaloids could decrease the intrinsic fluorescence of Bcl-2 mainly through static quenching. By comparing the structures of the three alkaloids, it was found that the binding affinity to Bcl-2 protein increased with molecular flexibility of the alkaloids.