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排序方式: 共有229条查询结果,搜索用时 15 毫秒
21.
Dr. Nina Erini Vera Beermann Martin Gocyla Manuel Gliech Dr. Marc Heggen Dr. Rafal E. Dunin-Borkowski Prof. Peter Strasser 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(23):6633-6638
Direct ethanol fuel cells are attractive power sources based on a biorenewable, high energy-density fuel. Their efficiency is limited by the lack of active anode materials which catalyze the breaking of the C−C bond coupled to the 12-electron oxidation to CO2. We report shape-controlled PtNiRh octahedral ethanol oxidation electrocatalysts with excellent activity and previously unachieved low onset potentials as low as 0.1 V vs. RHE, while being highly selective to complete oxidation to CO2. Our comprehensive characterization and in situ electrochemical ATR studies suggest that the formation of a ternary surface site ensemble around the octahedral Pt3Ni1Rhx nanoparticles plays a crucial mechanistic role for this behavior. 相似文献
22.
23.
Rafal Sitko Beata Zawisza Ewa Talik Paulina Janik Grzegorz Osoba Barbara Feist Ewa Malicka 《Analytica chimica acta》2014
Graphene oxide (GO) is a novel material with excellent adsorptive properties. However, the very small particles of GO can cause serious problems is solid-phase extraction (SPE) such as the high pressure in SPE system and the adsorbent loss through pores of frit. These problems can be overcome by covalently binding GO nanosheets to a support. In this paper, GO was covalently bonded to spherical silica by coupling the amino groups of spherical aminosilica and the carboxyl groups of GO (GO@SiO2). The successful immobilization of GO nanosheets on the aminosilica was confirmed by scanning electron microscopy and X-ray photoelectron spectroscopy. The spherical particle covered by GO with crumpled silk wave-like carbon sheets are an ideal sorbent for SPE of metal ions. The wrinkled structure of the coating results in large surface area and a high extractive capacity. The adsorption bath experiment shows that Cu(II) and Pb(II) can be quantitatively adsorbed at pH 5.5 with maximum adsorption capacity of 6.0 and 13.6 mg g−1, respectively. Such features of GO nanosheets as softness and flexibility allow achieving excellent contact with analyzed solution in flow-rate conditions. In consequence, the metal ions can be quantitatively preconcentrated from high volume of aqueous samples with excellent flow-rate. SPE column is very stable and several adsorption–elution cycles can be performed without any loss of adsorptive properties. The GO@SiO2 was used for analysis of various water samples by flame atomic absorption spectrometry with excellent enrichment factors (200–250) and detection limits (0.084 and 0.27 ng mL−1 for Cu(II) and Pb(II), respectively). 相似文献
24.
Malgorzata Baranska Rafal Baranski Ewa GrzebelusMaciej Roman 《Vibrational Spectroscopy》2011,56(2):166-169
It is the first report of direct, in situ detection of carotenoids at the subcellular level by using Raman microspectroscopy. Single crystals sequestered in a carrot cell were measured using FT-Raman spectrometer equipped with a microscope and 40× objective. The observed characteristic bands centered at 1518 cm−1 and 1156 cm−1 proved the crystals were composed of carotenoids with β-carotene being predominant. The obtained results show the potential of Raman microspectroscopy for identification and analysis of compounds localized in cytoplasm by taking measurements directly from a single plant cell. 相似文献
25.
Raut S Heck A Vishwanatha J Sarkar P Mody A Luchowski R Gryczynski Z Gryczynski I 《Journal of photochemistry and photobiology. B, Biology》2011,102(3):241-245
The antioxidant properties of aminobenzamide cysteine (ABZ Cys) makes it a molecule that can potentially be used as a drug in oxidative stress related diseases and delivered in the form of a nanoparticles. Here we have studied the photo-physical properties of ABZ Cys, a fluorescent analogue of a popular antioxidant N-acetyl cysteine (NAC). We have compared ABZ Cys steady state and time-resolved fluorescence properties with its parent compounds anthranilic acid and anthranilamide in solution as well as in poly-vinyl alcohol (PVA) polymer films. ABZ Cys did not show any significant shift in absorption after entrapment in PVA film, but there was a shift towards shorter wavelengths in the emission peak compared to the phosphate buffer solution. Fluorescence lifetimes and quantum yields indicated a slight quenching of ABZ Cys fluorescence in comparison to the cysteine-less parent compounds. We also demonstrated that very low concentrations of ABZ Cys, such as 100 nM, are readily detected by a commercial spectrofluorometer. Hence we have established the possible use of ABZ Cys in biomedical applications. 相似文献
26.
The direct dehydrogenative C-N coupling of azoles or polyfluoroarenes with N-H sulfoximines proceeds effectively in the presence of a copper catalyst at room temperature under air to afford the corresponding N-arylsulfoximines in good to high yields. 相似文献
27.
The LaXO(3):Tb(3+) (X = Al(3+), Ga(3+), In(3+)) perovskite nanoparticles were obtained using the nonhydrolytic treatment (Bradley reaction) of the molecular precursors of the La(O(i)Pr)(3), Al(O(i)Pr)(3), Ga(O(i)Pr)(3), In(5)O(O(i)Pr)(13), and Tb(acac)(3), respectively. It was shown that crystal structure and morphology evolution in the LaXO(3), X = Al, Ga, In nano-oxide series depended on the size and chemical properties of the X-metal atom. Formation of the LaInO(3):Tb(3+) nanoparticles is distinctly less thermodynamically demanding on contrary to the LaAlO(3):Tb(3+) and LaGaO(3):Tb(3+) since it provided crystalline product directly in the solution synthesis at 202 °C, which is the lowest reported synthesis temperature for this compound up-to-date. This behavior was ascribed to the effects directly connected with the dopant substitution (exchange of bigger La(3+) cation with smaller Tb(3+)) as well as reduction of the particle size. The size effects are mostly reflected in the expansion of the cell volume, changes of the cell parameters as well as shifting and broadening of the Raman bands. Indirectly, size reduction has also an effect on the luminescence properties through the higher probability of presence of surface and net defects as well as heterogeneous distribution of the Tb(3+) ions caused by high surface-to-volume ratio. The prepared nanophosphors show basically green emission with exception of white-green in case of the LaInO(3):Tb(3+). Strong emission quenching was found in the latter case being most likely a consequence of the nonradiative energy transfer between Tb(3+) and In(3+) as well as the presence of defects. In comparison to the Pechini's method, the LaXO(3) nanoparticles required significantly lower annealing temperature (700 °C) necessary for complete crystallization. Generally the resulting particles are distinctly smaller (5 to 25 nm) and less agglomerated (50-100 nm) depending on the reaction conditions as well as thermal treatment. For the first time, it was shown that the LaGaO(3):Tb(3+) nanopowder has crystallized in the high-temperature rhombohedral R3c phase. 相似文献
28.
Bas B. Van Aken Martial Duchamp Chris B. Boothroyd Rafal E. Dunin-Borkowski Wim J. Soppe 《Journal of Non》2012,358(17):2179-2182
The p-type Si layer in a-Si and μc-Si solar cells on foil needs to fulfil several important requirements. The layer is necessary to create the electric field that separates the photo-generated charge carriers; the doping also increases the conductivity to conduct the photocurrent to the front contact; on the other hand, the p-layer should transmit the incident light efficiently to the intrinsic absorber layer. We show that it is possible to study TEM samples prepared, for analysis of possible layer defects, by focussed ion beam milling to detect boron and carbon concentrations as low as 1020 cm-3, using core-loss EELS combined with numerical analysis. We control the band gap and activation energy of p-a-SiC by varying the B2H6 and CH4 flow during deposition in the process chamber. We have found a linear relation between the activation energy of the dark conductivity Eact and the optical band gap E04. Modelling shows that the optimum efficiency in nip solar cells is obtained when the p-a-SiC band gap is slightly larger than the band gap of the absorber layer. We have assessed the potential of core-loss EELS for detecting B and C concentrations as low as 1020 cm-3 in a spatially resolved manner, and of low-loss EELS as a probe of the local variations in plasmon energy. 相似文献
29.
The structure of tetraaqua-bis(nitrato-O,O′)-(1,10-phenanthroline-N,N′)-lanthanum(III) 1,3,5,7-tetraazatricyclo[3.3.1.13,7]decane nitrate dihydrate, [La(NO3)2 · phen · (H2O)4]+ · hmt · NO
3
−
· 2H2O, is presented. The lanthanum ion exhibits tenfold coordination and the polyhedron can be described as tetradecahedron. The
complex cations, nitrate ions, water and hexamethylenetetramine molecules are assembled via hydrogen bonds, H–π rings and π–π stacking interactions into 3D supramolecular network. The bond strength of coordination sphere was calculated by means of
the bond-valence method. The influence of La:phen stoichiometry and additional ligand on the changes of lanthanum(III) coordination
sphere geometry in ten-coordinated complexes with 1,10-phenanthroline was discussed. The infrared spectrum of structure optimised
by means of quantum mechanical calculations was analysed and compared with measured one. The obtained compound was characterised
by thermogravimetric analysis in conjunction with evolved gases in the air atmosphere. 相似文献
30.
Cage-like ordered mesoporous silica, FDU-1, with about twice the pore volume and a narrower pore size distribution compared with those for previously reported samples was synthesized in a much shorter time by doubling the amount of block copolymer, adding sodium chloride and lowering the acid concentration. 相似文献