The medium-chain-length polyhydroxyalkanoate (PHAMCL) produced by Pseudomonas putida PGA1 using saponified palm kernel oil as the carbon source could degrade readily in water taken from Kayu Ara River in Selangor,
Malaysia. A weight loss of 71.3% of the PHA film occurred in 86 d. The pH of the river water medium fell from 7.5 (at d 0)
to 4.7 (at d 86), and there was a net release of CO2. In sterilized river water, the PHA film also lost weight and the pH of the water fell, but to lesser extents. The C8 monomer
of the PHA was completely removed after 6 d of immersion in the river water, while the proportions of the other monomers (C10,
C12, and C14) were reversed from that of the undegraded PHA. By contrast, the monomer composition of the PHA immersed in sterilized
river water did not change significantly from that of the undegraded PHA. Scanning electron microscopy showed physical signs
of degradation on the PHA film immersed in the river water, but the film immersed in sterilized river water was relatively
unblemished. The results thus indicate that the PHAMCL was degraded in tropical river water by biologic as well as nonbiologic means. A significant finding is that shorter-chain
monomers were selectively removed throughout the entire PHA molecule, and this suggests enzymatic action. 相似文献
The (0001) surface of alpha-Al(2)O(3) single crystals has been imaged by atomic force microscopy in water. The observed hexagonal lattice arrangement has a period of 4.7 A, in good agreement with the known bulk unit cell. The sample cleaning procedure was found to be crucial in obtaining clean terraces and achieving lattice resolution. 相似文献
The photoassisted charge behavior of hydrogen storage alloy modified with TiO2/Pt nanocomposites (HSA-TiO2/Pt electrode) was investigated. The HSA-TiO2/Pt electrode can be photocharged under current. The mechanism of photoassisted behavior of the HSA-TiO2/Pt electrode was explained through the results of cyclic voltammogram and impedance measurements of the HSA-TiO2/Pt electrode. Upon illumination, the photogenerated electrons can charge the electrode, but the photogenerated holes may oxidize the hydrogen storage alloy to form a layer of metal oxide. Because the current could keep the electrode active, the H atoms produced by photogenerated electrons diffused to the hydrogen storage alloy and a metal hydride formed. The electrode delivered a higher discharge capacity due to the assistance of photocharge. 相似文献
Preparation and photochromic behavior of ormosil containing encapsulated AgTCNQ molecules were studied in this paper. The
ormosil resulted from hydrolysis and polycondensation of glycidoxypropyltrimethoxysilane, dimethyldimethoxysilane and methyltrimethoxysilane.
The time to add AgNO3 water solution into the resultant sol was a key factor to synthesize AgTCNQ molecules inside ormosil matrix. AgTCNQ molecules
encapsulated in the ormosil showed different photochromic behavior compared with pure AgTCNQ film: normal photochromic reaction
can be realized, while reverse photochromic reaction can not. The “cage” model was used to explain this phenomenon. 相似文献
Two new azo dyes of alpha-isoxazolylazo-beta-diketones and their Ni(II) and Cu(II) complexes with blue-violet light wavelength were synthesized using a coupling component, different diazo components and metal (II) ions (Ni2+ and Cu2+). Based on the elemental analysis, MS spectra and FT-IR spectral analyses, azo dyes were unequivocally shown to exist as hydrazoketo and azoenol forms which were respectively obtained from the solution forms and from the solid forms. The action of sodium methoxide (NaOMe) on azo dyes in solutions converts hydrazoketo form into azoenol form, so azo dyes are coordinated with metal (II) ions as co-ligands in the azoenol forms. The solubility of all the compounds in common organic solvents such as 2,2,3,3-tetrafluoro-1-propanol (TFP) or chloroform (CHCl3) and absorption properties of spin-coating thin films were measured. The difference of absorption maxima from the complexes to their ligands was discussed. In addition, the TG analysis of the complexes was also determined, and their thermal stability was evaluated. It is found that these new metal (II) complexes had potential application for high-density digital versatile disc-recordable (HD-DVD-R) system due to their good solubility in organic solvents, reasonable and controllable absorption spectra in blue-violet light region and high thermal stability. 相似文献
The preparation and fractionation of oligomeric proanthocyanidins (OPCs) are particularly important for the application of tannins in the biomedical field. By use of two different methods—gel filtration chromatography (GFC) with Sephadex LH-20 and progressive solvent precipitation—the OPCs were prepared and fractionated from mangosteen pericarp. The fractions were compared by reversed-phase and normal-phase high-performance liquid chromatography–electrospray ionization mass spectrometry and gel permeation chromatography. GFC directly purified oligomers (monomer to pentamer) with polydispersity values close to 1 and generated fractions with a higher level of total phenols (800.59 mg gallic acid equivalents per gram) but a lower yield (7.72%). Progressive solvent precipitation rapidly prepared and fractionated OPCs with a lower level of total phenols (609.57 mg gallic acid equivalents per gram) but a higher yield (24.74%) and higher polydispersity. Additionally, we found pronounced structural and quantitative differences among different tannin-rich fractions, and fractions obtained by GFC better reflected the structural diversity and complexity of OPCs from mangosteen pericarp. This study presents different ways of preparing and fractionating OPCs in the biomedical field.
The reactions of pyrimidine‐phosphine ligand N‐[(diphenylphosphino)methyl]‐2‐pyrimidinamine ( L ) with various metal salts of PtII, PdII and CuI provide three new halide metal complexes, Pt2Cl4(μ‐L)2·2CH2Cl2 ( 1 ), Pd2Cl4(μ‐L)2 ( 2 ), and [Cu2(μ‐I)2L2]n ( 3 ). Single crystal X‐ray diffraction studies show that complexes 1 and 2 display a similar bimetallic twelve‐membered ring structure, while complex 3 consists of one‐dimensional polymeric chains, which are further connected into a 2‐D supramolecular framework through hydrogen bonds. In the binuclear complexes 1 and 2 , the ligand L serves as a bridge with the N and P as coordination atoms, but in the polymeric complex 3 , both bridging and chelating modes are adopted by the ligand. The spectroscopic properties of complexes 1 ‐ 3 as well as L have been investigated, in which complex 3 exhibits intense photoluminescence originating from intraligand charge transfer (ILCT) π→π* and metal‐to‐ligand charge‐transfer (MLCT) excited states both in acetonitrile solution and solid state, respectively. 相似文献