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941.
Min Wei 《Journal of solid state chemistry》2004,177(7):2534-2541
Layered double hydroxides, novel anionic clay, meet the first requirement as inorganic matrices for encapsulating functional drugs or biomolecules with negative charge in aqueous media. In this study, naproxen has been intercalated into Mg-Al layered double hydroxide by the methods of ion exchange. The structure and composition of the intercalated material have been studied by X-ray diffraction (XRD), UV-vis spectroscopy and inductively coupled plasma emission spectroscopy. A schematic model has been proposed. Furthermore, in situ Fourier transform infrared spectroscopy, in situ high-temperature XRD, and thermogravimetry (TG) have been used to characterize the thermal decomposition of the hybrid material. It has been found that the thermal stability of the intercalated naproxen is significantly enhanced compared with the pure form before intercalation, which suggests that this drug-inorganic layered material may have prospective application as the basis of a novel drug delivery system. 相似文献
942.
Photoluminescence (PL) measurement has been made on P-doped p-GaS. The 2.35 and 2.12 eV emission bands are observed in the PL spectrum of P-doped sample at 77 K. The temperature dependence of full-width at half-maximum and the shape of the PL spectrum of the 2.12 eV emission band are characterized by the recombination mechanism of the configurational coordinate model. It is found that the 2.12 eV emission band is related to the complex center of vacancy and acceptor due to P atoms. It is found from the presence of the complex center that the P-doped samples include a high concentration of defects or defect complexes. 相似文献
943.
This work is concerned with the determination of the effective behavior of sequentially laminated composites with nonlinear behavior of the constituting phases. An exact expression for the effective stress energy potential of two-dimensional and incompressible composites is introduced. This allows to determine the stress energy potential of a rank-N sequentially laminated composite with arbitrary volume fractions and lamination directions of the core laminates in terms of an N-dimensional optimization problem.
Stress energy potentials for sequentially laminated composites with pure power-law behavior of the phases are determined. It is demonstrated that as the rank of the lamination becomes large the behaviors of certain families of sequentially laminated composite tend to be isotropic. Particulate composites with both, stiffer and softer inclusions are considered. The behaviors of these almost isotropic composites are, respectively, softer and stiffer than the corresponding second-order estimates recently introduced by Ponte Castañeda (1996). 相似文献
944.
Zhi Hua WANG Min CAI Shu Jun WANG 《中国化学快报》2006,17(6):809-812
As a novel type builder for phosphate-free detergent1,2, layered crystal sodium disilicate has many advantages over other builders for phosphate detergents. The raw material of layered crystal sodium disilicate is sodium silicate. Because of the effects o… 相似文献
945.
Everson Kandare Dongyan Wang Jeanne M. Hossenlopp 《Polymer Degradation and Stability》2006,91(8):1781-1790
Composites of poly(vinyl ester) (PVE) with copper hydroxy dodecyl sulfate (CHDS) were prepared by thermal curing. The efficiency of the additive, CHDS, in reducing flammability is demonstrated via cone calorimetry and thermogravimetric analysis (TGA). The addition of 1-10% by mass of the CHDS additive resulted in significant increments in char formation (∼4-11%) from thermogravimetric analysis (TGA). Incorporation of the CHDS into the polymer matrix at these low concentrations leads to substantial reductions in the total heat release (∼20-30%) but no significant change in the peak heat release rate. The composite materials generally ignite more quickly, however, the flame extinguishes faster for the composites relative to the virgin polymer. X-ray diffraction (XRD) and infrared spectroscopic analyses of the residues collected at various stages during thermal decomposition of the composites, suggest the participation of copper-containing species in promoting enhanced thermal stability of PVE. 相似文献
946.
Three manganese sulfate-oxalates, namely, H2pip·Mn2(SO4)2(ox)(H2O)2·2H2O (1), H3ipa⋅Mn2(SO4)(ox)2.5·H2O (2), and H3dpta⋅Mn2(SO4)2(ox)1.5(H2O)3 (3), were prepared under solvent-free conditions, where pip = piperazine, ox = oxalate, ipa = 3,3′-iminobis(N,N-dimethylpropylamine), and dpta = dipropylenetriamine. These compounds have different layered structures intercalated with organic cations. Their pore apertures range from small 8-membered ring (8 MR) to large 12 MR and extra-large 20 MR. The temperature dependence of the magnetic susceptibility of these compounds were also investigated. 相似文献
947.
As for the stabilization of chemically sensitive bioactive molecule in this study, gallic acid (GA) with antioxidant property was intercalated into interlayer space of layered double hydroxide (LDH), which was realized by exfoliation and reassembling reaction. At first, the pristine nitrate-type Zn2Al-LDH in solid state was synthesized via co-precipitation followed by the hydrothermal treatment at 80 °C for 6 h, and then exfoliated in formamide to form a colloidal solution of exfoliated LDH nanosheets, and finally reassembled in the presence of GA to prepare GA intercalated LDH (GA-LDH) desired, where the pH was adjusted to 8.0 in order to deprotonate GA to form gallate anion. According to the XRD analysis, GA-LDH showed well-developed (00l) diffraction peaks with a basal spacing of 1.15 nm, which was estimated to be larger than that of the pristine LDH (0.88 nm), indicating that gallate molecules were incorporated into LDH layers with perpendicular orientation. From the FT-IR spectra it was found that gallic acid was completely deprotonated into gallate, and stabilized in between LDH lattices via electrostatic interaction. The content of GA in GA-LDH was determined to be around 23 wt% by UV–vis spectroscopic study, which was also confirmed by HPLC analysis. According to the in-vitro release of GA out of GA-LDH in PBS solution (pH 7.4) at 4 °C, GA was sustainably released from GA-LDH nanohybrid up to 86% within 72 h. The antioxidant property of GA-LDH was almost the same with that of intact GA which was examined by DPPH. The photostability of GA-LDH under UV light irradiation was immensely enhanced compared to intact GA. It is, therefore, concluded that the present GA-LDH nanohybrid can be considered as an excellent antioxidant material with high chemical- and photo-stabilities, and controlled release property. 相似文献
948.
Marzieh Piryaei 《Natural product research》2018,32(2):243-245
Zn/Al layered double hydroxide (LDH) films were fabricated in situ with anodic aluminium oxide aluminium as both the substrate and the sole aluminium source by means of urea hydrolysis. Headspace solid phase microextraction using LDH fibre in combination with capillary GC–MS was utilised as a monitoring technique for the collection and detection of the volatile compounds of Origanum vulgare. Experimental parameters, including the sample weight, microwave power, extraction time and humidity effect, were examined and optimised. 相似文献
949.
Rodica Zăvoianu Ruxandra Bîrjega Emilian Angelescu Octavian D. Pavel 《Comptes Rendus Chimie》2018,21(3-4):318-326
This contribution investigates the obtaining of layered double hydroxides (LDHs) modified with different concentrations of yttrium and the effect of the yttrium concentration and temperature during the rehydration of the mixed oxides derived from these solids. Mg3Al(1?x)Yx-LDH (where x = 0.04–0.6) have been prepared using the standard coprecipitation method under low supersaturation conditions. After the calcination of these solids (460 °C, 18 h), the corresponding mixed oxides were obtained. The reconstruction of the layered structure was attempted by rehydration of the mixed oxides under two different conditions: (1) at 25 °C and (2) at 70 °C. All the aforementioned solids have been characterized by chemical analysis, X-ray diffraction, DRIFTS spectra, N2 adsorption–desorption isotherms, and determination of base sites. Their catalytic activity was tested in cyanoethylation of ethanol with acrylonitrile. The results obtained after the characterization and the catalytic activity tests were compared with those obtained for a standard hydrotalcite Mg3Al. 相似文献
950.
The nitridomagnesogermanate Ca2Mg5GeN6 was synthesized at 780 °C using a sodium flux in sealed tantalum ampules. Pure metals were used as starting materials and sodium azide NaN3 was added as nitrogen source. Ca2Mg5GeN6 was obtained as a byproduct in the form of colorless platelet‐like crystals. Solution and refinement of the crystal structure [space group P63/mmc (no. 194), Z = 1, a = 3.453(2), c = 17.506(13) Å and V = 180.8(2) Å3] were performed on the basis of single‐crystal X‐ray diffraction data. Ca2Mg5GeN6 represents the first layered nitridogermanate. Its structure is made up of corner‐sharing (Mg/Ge)N4 tetrahedra and corner‐sharing trigonal planar (Mg/Ge)N3 units with mixed occupancy of Mg and Ge. Ca2+ ions are located in between the sheets. The crystal structure is closely related to that of the nitridomagnesoaluminate CaMg2AlN3 as well as to the carbides ScAl3C3 and UAl3C3. 相似文献