Influence of the cathodic polarization on the stability of Ti surface in concentrated KOH solutions

The stability of spontaneous thin layers and thin layers formed upon cathodical polarization of Ti in KOH solutions have been studied by potentiostatic and ellipsometric methods. At open circuit potential (OCP) the strongly adherent films, whose thickness depends on the concentration of the KOH solution, were formed. During the cathodic polarization the transformation of these films to weakly adsorbed precipitated layers on the electrode surface was observed. Comparing the theoretically computed curves with the experimental Ψ vs Δ loci measured ellipsometrically, the complex indices of refraction and the thickness of the generated films, from 3.6 to 60 nm in 1 M KOH and from 36 to 105 nm in 5 M KOH (adherent to the electrode surface), were determined. At OCP the rate of film growth increases with increasing the concentration of KOH solution. Cathodic polarizations change the chemical composition and retard the rate of film growth. Based on the ellipsometric and electrochemical data the chemical compositions of the formed films consisted of TiO₂, Ti₂O₃, TiO₂·H₂O, Ti(OH)₃ and TiOOH·nH₂O.     

Fuzzy Symmetries for Linear Molecules and their Molecular Orbitals

In this paper, the fuzzy symmetry of some prototypical linear molecules has been analyzed. The results show that some molecular orbitals (MOs) are less symmetrical but some others are more symmetrical than the molecular skeleton, which the MOs correspond to. The membership functions of space inversion for MOs are closely related to the chemical characteristics of the MOs. Sometimes, although the symmetry of a molecular skeleton is not obvious, however that of some MO is quite obvious. The membership functions of the fuzzy inversion symmetry depend on the choice of the position of the center of inversion. As compared to those of diatomic molecules and linear tri-atomic molecules, the linear polyatomic molecules in which a distinctive fuzzy symmetry of space translation may exist, and thus a significant effect on their properties can be expected.     

Synthesis and characterization of microencapsulated dicyclopentadiene with melamine–formaldehyde resins

Microcapsules containing healing agents have been used to develop the self-healing polymeric composites. These microcapsules must possess special properties such as appropriate strength and stability in surrounding medium. A new series of microcapsules containing dicyclopentadiene (DCPD) with melamine–formaldehyde (MF) resin as shell material were synthesized by in situ polymerization technology. These microcapsules may satisfy the requirements for self-healing polymeric composites. The chemical structure of microcapsule was identified by using Fourier transform infrared (FTIR) spectrometer. The morphology of microcapsule was observed by using optical microscope (OM) and scanning electron microscope. Size distribution and mean diameter of microcapsules were determined with OM. The thermal properties of microcapsules were investigated by using thermogravimetric analysis and differential scanning calorimetry. Additionally, the self-healing efficiency was evaluated. The results indicate that the poly(melamine–formaldehyde) (PMF) microcapsules containing DCPD have been synthesized successfully, and their mean diameters fall in the range of 65.2∼202.0 μm when the adjusting agitation rate varies from 150 to 500 rpm. Increasing the surfactant concentration can decrease the diameters of microcapsules. The prepared microcapsules are thermally stable up to 69 °C. The PMF microcapsules containing DCPD can be applied to polymeric composites to fabricate the self-healing composites.     

Synthesis,crystal structure,electrochemical properties and large optical limiting effect of a novel 3-(E)-ferrocenyl-vinyl-<Emphasis Type="BoldItalic">N</Emphasis>-hexyl carbazole

The novel compound, 3-(E)-ferrocenyl-vinyl-N-hexylcarbazole (FVHC) was first synthesized and fully characterized by elemental analysis, IR, ¹H-NMR, single-crystal X-ray diffraction, ultraviolet (UV) absorption, cyclic voltammograms (CV) and optical limiting (OL) measurements. The result of single crystal X-ray diffraction for the compound reveals that the ferrocenyl and carbazole groups are approximately coplanar, and bridged by double-bond with E configuration, showing that there is a well-delocalized π-electron system in the molecule. The electrochemical investigation indicated that the electron in the FVHC may partially be delocalized over the π-conjugated system and CT process in functionalized carbazole systems. Besides, the compound exhibited strong UV absorption and large optical limiting effect, indicating promising potential applications as useful OL materials.     

New efficient organocatalytic oxidation of benzylic compounds by molecular oxygen under mild conditions

Efficient aerobic oxidation of benzylic compounds has been achieved under no irradiation using a new organocatalytic system in the presence of acridine yellow and N-hydroxyphthalimide with assistance of a catalytic amount of molecular bromine. Various substrates, especially alkylaromatics, were effectively oxygenated to the corresponding carbonyl compounds with molecular oxygen as oxidant under mild conditions. For instance, indan was oxidized with 92% conversion and 79% selectivity for 1-indanone under 0.3 MPa of O₂ at 75 °C.     

水-乙醇二元体系共沸混合物的热力学研究

用全自动低温绝热量热计测定了水、乙醇以及水和乙醇组成的共沸混合物在不同温区的摩尔热容Cp,m. 建立了共沸混合物Cp,m与温度T的函数关系.结果表明,水和乙醇组成的共沸混合物在98.496 K发生玻璃态转化,在158.939 K 和270.95 K发生固-液相变.获得了其相应的相变焓和相变熵.计算了以298.15 K为基准的该共沸混合物的热力学函数和超额热力学函数.     

Carbon nanotube array-based biosensor

Aligned multi-wall carbon nanotubes (MWNT) grown on platinum substrate are used for the development of an amperometric biosensor. The opening and functionalization by oxidation of the nanotube array allows for the efficient immobilization of the model enzyme, glucose oxidase. The carboxylated open-ends of nanotubes are used for the immobilization of the enzymes, while the platinum substrate provides the direct transduction platform for signal monitoring. It is also shown that carbon nanotubes can play a dual role, both as immobilization matrices and as mediators, allowing for the development of a third generation of biosensor systems, with good overall analytical characteristics.     

Binary mixtures based on polycaprolactone and cellulose derivatives

Pyrolytic process has a promising potential for the environmentally friendly upgrading of lignocellulosic and plastic waste. Thermogravimetry and pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) were used to get information about the reactive decomposition of PCL in binary mixtures with microcrystalline cellulose (MC) or sisal fibres (SF). Preliminary thermogravimetric investigation showed that biomass is thermally degraded at lower temperatures than PCL and this process has a predominant influence on the thermal behaviour of the mixtures. Discrepancies between the experimental and predicted TG/DTG profiles were considered as a measurement of the extent of interactions occurring on co-pyrolysis. It was found that reactivity of PCL was slightly increased in PCL-SF binary mixtures. Evolution of acidic products from cellulose and hemicelluloses decomposition may promote PCL degradation in binary mixtures with SF. It seems that the co-pyrolysis process could have potential for the environmentally friendly transformation of biocomposites.     

ATR-FTIR study of Bacillus sp. and Escherichia coli settlements on the bare and Al2O3 coated ZnSe internal reflection element

FTIR-ATR has been used for understanding the interaction between bacteria and surfaces in the adsorption progress.