Advanced Materials Research Vols. 554-556

Abstract: A macro-cyclic Schiff base ligand and the corresponding Cu (II) and Ni (II) complexes were synthesized and characterized. And the catalytic efficiency of the metallomicelles made of these complexes and noninonic micelle Brij35, as mimetic hydrolytic metalloenzyme, was investigated in the catalytic hydrolysis of bis(p-nitrophenyl) phosphate (BNPP) in this paper. The results show that the rate of the BNPP hydrolysis in the metallomicelles is about 106 -fold faster than that of the BNPP spontaneous hydrolysis in aqueous solution at the same conditions. The analysis of the characteristic absorption spectra of the hydrolytic reaction systems indicates that the key intermediate, composing of BNPP and Ni(II) or Cu(II) complexes, has been formed and the catalytic hydrolysis of BNPP is an intramolecular nucleophilic substitution reaction. Based on the results of characteristic absorption spectra, the mechanism of BNPP catalytic hydrolysis has been proposed and also the corresponding kinetic mathematical model has been established.

Abstract: The influences of three kinds of polyethylene glycol (PEG), namely PEG-200, PEG-1000 and PEG-20000, on the dispersion stability of pyrite powder in aqueous solution were investigated by spectrophotometry. The results indicated that the stability of pyrite powder dispersed in aqueous solution was remarkably dependent upon the molecular weight and content of PEG, pH value of suspension, and ultrasonication power. Among three kinds of polyethylene glycol, PEG-20000 was the most effective additive to improve the dispersion stability and wettability of pyrite powder in water. When 8% PEG-20000 was employed as the dispersant, the best dispersion stability of pyrite powder in aqueous solution could be obtained under the conditions of pH at 5-6 and 100-W ultrasonication power. The FTIR spectroscopic analysis showed that the adsorption between the polyethylene glycol and pyrite ore powder was formed by hydrogen bonding. The adsorption of polyethylene glycol onto the surface of pyrite powder via hydrogen bonding provided a high degree of steric stabilization, which effectively prohibited the aggregation of pyrite powder, and thus the dispersion stability of as-formed aqueous suspension was promoted.

Abstract: The catalytic hydrolysis of Bis(p-nitrophenyl) phosphate ester (BNPP) in the metallomicelle made up of Ce³⁺-diethylenetriamine and LSS (N-lauroyl sarcosinate) was investigated by UV/VIS method. The effect of the catalytic efficiency and stability of the system was studied under the different conditions. The results indicated that the catalytic system exhibited high activity, stability and reproducibility in the BNPP catalytic hydrolysis under proper proportion of Ce³⁺ ion and diethylenetriamine, pH and temperature when the concentration of LSS is higher than its CMC (critical micelle concentration). The results also showed that the active species is the complex made up of Ce³⁺ ion and diethylenetriamine.

Abstract: The influence of step and domain boundary on growth of Si(111)-√ 3×√3-Ag has been studied in situ using optical surface second-harmonic generation and low energy electron diffraction. The second harmonic intensity shows a difference of about 50% for Si(111) surfaces with different miscut angles and domain boundary densities, although no significant difference has been observed in low energy electron diffraction patterns, indicating a significant impediment to the growth of Si(111)-√ 3×√3-Ag by step and domain boundaries. Simulation results reveal a 90% coverage of Si(111)-√ 3×√3-Ag on the vicinal substrate with an miscut angle of 0.41o, consistent with the dynamics of Ag atoms on Si(111)-7×7 surface. The influence of two dimentional adatom gas on surface structure has also been discussed.

Abstract: LiMn_1-xMg_xPO₄/C(x=0, 0.01, 0.04, 0.05, 0.1) were synthesized by using wet-ballmilling and solid-state calcining with phenolic resin as the carbon source. All samples are single phase with a similar morphology, but the cation substitution results in a crystal lattice shrink because of the smaller ionic radii of Mg²⁺, the particles are small and homogeneous. CV, EIS and charge/discharge measurement shows that the Mg substitution leads to a significantly increased reversible capacity due to the enhanced electrochemical kinetics. LiMn_0.96Mg_0.04PO₄/C calcined at 600°C has a discharge capacity of 144mAh/g at 0.05C. When charging-discharging by CC-CV-CC mode at high rates, LiMn_0.96Mg_0.04PO₄/C composite exhibits a good cycle and rate performance.

Abstract: The molecular imprinted polymer (MIP) was synthesized by precipitation polymerization with caffeine as template, methacrylic acid (MAA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker. A selective electrode for the potentiometric determination of caffeine in the aqueous medium was developed using the MIP-modified coated-wire electrode. The electrode shows response for caffeine in a concentration range of 1.0×10-8 to 1.0×10-5 M with a lower detection limit of 5.0×10-9 M. The electrode can be used for more than 100 times. The response time is 15 s and the signal is constant in the pH range 6.4 to 9.0. The electrode can be successfully applied for the monitoring of caffeine in syrup sample.

Abstract: Based on the Planck's quantum hypothesis and the Einstein's light quantum hypothesis , the Zhongjizi (a new elementary particles) hypothesis is proposed. It revealed the quantum nature of light. Light quantum (which is photon) was essentially a collection of Zhongjizi, light was constituted of Zhongjizi, the essence of light was the nature of particle, and the quantum nature of light was essentially the Zhongjizi nature of light. The quantum nature of light revealed out: atomic spectra was produced by the light of different frequencies that emitted and absorbed by the extranuclear electrons of different motion states (different rotation frequencies) under certain conditions. The rotation frequency of extranuclear electrons was equal to the frequencies of light that emitted and absorbed by the electrons. By using this law, and according to the atomic spectra, we can know the state of the electron structure of atoms and the movement of electrons ,according to the frequency (the cycle )that rotate round the nuclear of the extranuclear electron in a state of motion , and the relationship of the distance between the electrons and the atomic nucleus .

Abstract: Pyrite utrafine powder was yielded through processing natural pyrite, including gravity separation, flotation and airflow grinding, which the contents of Fe and S are 45.30wt% and 50.95wt% respectively and the mean grain size is 13μm. Pyrite powder modified by fatty acid salt A was investigated by TG/DSC, XPS and XRD. The results indicate that the phase of powder is mostly pyrite FeS₂ coating with organic modifier, and S exists in the form of [S₂]^2- principally on modified pyrite surface. Furthermore, electrochemical impedance spectroscopy, cyclic voltammetry measurement and galvanotactic current charge and discharge methods were applied to exhibit the electrochemical performance of pyrite sample. The results show that modified pyrite has lower charge transfer resistance and higher conductivity than that of natural pyrite, and the specific discharge capacity is as high as 850mAh/g under 0.354A current at room temperature and the cutoff of 0.5V closing to the theoretical specific capacity of pyrite (890mA•h/g), and the voltage plateau is 1.44V.

Abstract: Electrodeposition was carried out on mild steel surface in 0.3 M sodium hydroxide solution (70% distilled water: 30% ethanol) containing 0.1 M salicylideneaniline using cyclic voltammetry and chronoamperometry techniques. Both techniques show the formation of the films on the mild steel surface. The corrosion behavior of electrodeposited mild steel was studied using electrochemical impedance spectroscopy (EIS) technique at various immersion times in 0.5 M sodium chloride solution (NaCl). The study indicates that the resistance of mild steel against corrosion increases after being electrodeposited with salicylideneaniline. However the films tend to diminished after 24 hours being immersed in 0.5 M NaCl solution.

Abstract: Amorphous nickel hydroxide codoped with Y and Mg was synthesized by micro-emulsion precipitation method combined with rapid freezing technique. The physical properties and micro-structural features of the prepared sample were characterized and high-temperature electrochemical performance was analyzed by cyclic voltammetry and charge/discharge tests, respectively. The results indicate that this amorphous nickel hydroxide codoped with Y and Mg has more structural defects and better thermal stability, therefore results in a relatively high specific capacity(332.46 mAh•g-1 at a charge/discharge rate of 0.2C) and a high middle discharge voltage of 1.265V at 60°C. Moreover, the Y and Mg codoped amorphous nickel hydroxide exhibits good electrochemical reaction reversibility and structural stability.