A poly (vinylpyridine-ethylene dimethacrylate) monolithic material was synthesized and selected as stir bar sorptive extraction (SBSE) medium. The influences of polymerization conditions on the extraction efficiency were investigated using phenol and p-nitrophenol as target analytes. Based on this, six strongly polar phenols in water were directly concentrated by the new SBSE and determined with high performance liquid chromatography equipped with diode array detector. To achieve the optimum extraction performance, several main parameters, including extraction and desorption time, pH value and contents of inorganic salt in the sample matrix were investigated. The method showed good linearity and acceptable recoveries, as well as advantages such as sensitivity, simplicity, low cost and high feasibility. The proposed method was successfully applied to the determination of phenolic compounds in lake and sea waters. 相似文献
Cu–Ni/γ-Al2O3 bimetallic catalysts were developed for anaerobic dehydrogenation of non-activated primary aliphatic alcohols to aldehydes. Systematic investigation about the promotion effect of nickel on the catalytic performance was carried out. Hydrogenation of C=C bond rather than C=O bond, was significantly improved over Cu–Ni/γ-Al2O3 catalyst by introducing nickel, which interprets the good conversion of primary aliphatic alcohols. This work would contribute to design new catalysts for dehydrogenation of primary aliphatic alcohols. 相似文献
We describe an electrochemical sensor for melamine based on a glassy carbon electrode (GCE) modified with reduced graphene oxide that was decorated with gold nanoparticles (AuNP/rGO). The AuNPs/rGO nanocomposite was synthesized by co-reduction of Au(III) and graphene oxide and characterized by transmission electron microscopy, Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The response of the modified GCE to melamine was investigated by using hexacyanoferrate as an electrochemical reporter. It is found that the electrochemical response to hexacyanoferrate is increasingly suppressed by increasing concentration of melamine. This is attributed to competitive adsorption of melamine at the AuNP/rGO composite through the interaction between the amino groups of melamine and the AuNPs. The presence of rGO, in turn, provides a platform for a more uniform distribution of the AuNPs and enhances the electron transfer rate of the redox reaction. The findings were used to develop a sensitive method for the determination of melamine. Under optimized conditions, the redox peak current of hexacyanoferrate at a working voltage of 171 mV (vs. SCE) is linearly related to the concentration of melamine in 5.0 to 50 nM range. The method was successfully applied to the determination of melamine in food contact materials.
A simple electrochemical sensor based on gold nanoparticles decorated reduced graphene oxide was developed for highly sensitive measurement of melamine in food contact materials.
Cellulose - Al/CuO nanothermites have displayed unique catalytic activities in accelerating the thermolysis of nitrocellulose (NC) and combustion characteristics of AP/HTPB propellant depending on... 相似文献
A new copper-thiolate cluster assembled framework [Cu2(μ4-SCH3)Cl]n (1), has been solvothermally synthesized through in situ reaction viz., in situ ligand generation and metal reduction. Compound 1 represents the first 3D framework based on Atlas-sphere functionalized by single μ2-Cl- groups. DOS calculation reveals the interaction of electronic structures. It is found that the HOMO is mainly distributed on Cl, Cu and S bonding orbitals, while the LUMO is dominated by Cu-Cl antibonding orbitals. 相似文献
Summary. In this paper, we derive quasi-norm a priori and a posteriori error estimates for the Crouzeix-Raviart type finite element
approximation of the p-Laplacian. Sharper a priori upper error bounds are obtained. For instance, for sufficiently regular
solutions we prove optimal a priori error bounds on the discretization error in an energy norm when . We also show that the new a posteriori error estimates provide improved upper and lower bounds on the discretization error.
For sufficiently regular solutions, the a posteriori error estimates are further shown to be equivalent on the discretization
error in a quasi-norm.
Received January 25, 1999 / Revised version received June 5, 2000 Published online March 20, 2001 相似文献
Pulsed laser ablation epitaxial Strancky-Krastanow growth of self-organized complex oxide Ce:BaTiO3 quantum dots on MgO(lOO) substrates is demonstrated. Atomic force microscopy and X-ray diffraction are used to observe the
structure and the growth process of the self-organized complex oxide quantum dots. The average dimension, height, and the
density of self-organized complex oxide Ce:BaTiO3 quantum dots are given. The nonlinear refractive indexes of the wetting layer and the selforganized ordered quantum dots
are determined by the single beam Z-scan method. The mechanisms of the nonlinear effect enhancement for these low-dimensional
structure are discussed. 相似文献
The aromatization of n hexane and mixed C 4 hydrocarbon was investigated under microwave heating over ZnNi/HZSM 5 catalyst of lower activity in order to compare with that under the conventional heating. For the n hexane aromatization, the selectivity for benzene and toluene by the microwave heating at 450 ℃ increases by 4% and 5%, respectively, and the aromatics yield by the microwave heating at 480℃ increases by 4% , compared with those by the conventional heating. For the mixed C 4 olefine aromatization, the BTX yield by the microwave heating at 400 ℃ increases by 17 08% and the aromatics selectivity is also higher than that by the conventional heating. 相似文献