排序方式: 共有126条查询结果,搜索用时 15 毫秒
91.
Sendroiu IE Mertens SF Schiffrin DJ 《Physical chemistry chemical physics : PCCP》2006,8(12):1430-1436
The effects of interparticle distance on the UV-visible absorption spectrum of gold nanocrystals aggregates in aqueous solution have been investigated. The aggregates were produced by ion-templated chelation of omega-mercaptocarboxylic acid ligands covalently attached to the nanoparticles surface. Variation of the ligand chain length provides control over the interparticle separation in the aggregates. The UV-visible spectra consist typically of a single particle band and a secondary band at higher wavelengths associated with the formation of aggregates in solution. The position of the latter depends on interparticle separation up to distances of approximately 8 nm, in accordance with existing models. Potential applications therefore include distance sensitive labels or proximity probes. Conversely, variation of the ligand length allows the preparation of nanostuctured materials with tuned optical properties. 相似文献
92.
F. van Stijn M. A. T. Kerkhoff B. G. M. Vandeginste 《Journal of chromatography. A》1996,750(1-2):263-273
Various off-line methods for clean-up and sample enrichment are available for the analysis of polycyclic aromatic hydrocarbons (PAHs) in edible oils and fats. These methods consist of laborious and time consuming procedures. This study reports an on-line method using LC-LC coupling. After clean-up of the sample on a donor-acceptor complex chromatography (DACC) column the PAHs are transferred to and separated on an analytical HPLC column. Quantification is carried out with fluorescence detection. The DACC column clean-up is fast and is carried out during the HPLC run of the previous sample. Compared to the traditional methods this automated on-line method saves considerable time and significantly reduces the amount of solvent waste. The method uses common HPLC equipment and its performance has been evaluated. 相似文献
93.
Van Deun R Nockemann P Fias P Van Hecke K Van Meervelt L Binnemans K 《Chemical communications (Cambridge, England)》2005,(5):590-592
The 9-hydroxyphenal-1-one ligand forms stable 3:1 complexes with trivalent lanthanides, in which it acts as an antenna suitable for the visible light excitation (up to 475 nm) of the trivalent europium ion. 相似文献
94.
Abad JM Mertens SF Pita M Fernández VM Schiffrin DJ 《Journal of the American Chemical Society》2005,127(15):5689-5694
This paper presents an efficient strategy for the specific immobilization of fully functional proteins onto the surface of nanoparticles. Thioctic acid-derivatized gold clusters are used as a scaffold for further stepwise modification, leading to a cobalt(II)-terminated ligand shell. A histidine tag introduced by genetic engineering into a protein is coordinated to this transition metal ion. The specific immobilization has been demonstrated for the cases of a genetically engineered horseradish peroxidase and ferredoxin-NADP(+) reductase, confirming the attachment of the fully functional proteins to the Co(II)-terminated nanointerface. The absence of nonspecific protein adsorption and the specificity of the binding site have been verified using several analogues of the enzymes without the histidine tag. 相似文献
95.
Fias S Fowler PW Delgado JL Hahn U Bultinck P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(10):3093-3099
Using multicentre delocalization indices, the ring current maps of a large set of polycyclic aromatic hydrocarbons (PAH) are reconstructed and compared with ab initio computations of the same maps in the pseudo-pi version of the ipsocentric approach to magnetic response. The quality of the comparison indicates that both delocalization and ring current approaches capture the same information about the aromatic nature of the PAH. Aromaticity as a global property, requires knowledge of more than single circuits, but the present results suggest no need to introduce a "multidimensional character" for aromaticity. 相似文献
96.
Bram Verbelen Lucas Cunha Dias Rezende Stijn Boodts Jeroen Jacobs Prof. Luc Van Meervelt Prof. Johan Hofkens Prof. Wim Dehaen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(36):12667-12675
A one‐step synthetic procedure for the radical C?H alkylation of BODIPY dyes has been developed. This new reaction generates alkyl radicals through the oxidation of boronic acids or potassium trifluoroborates and allows the synthesis of mono‐, di‐, tri‐, and tetraalkylated fluorophores in a good to excellent yield for a broad range of organoboron compounds. Using this protocol, multiple bulky alkyl groups can be introduced onto the BODIPY core thus creating solid‐state emissive BODIPY dyes. 相似文献
97.
Radical CH Arylation of the BODIPY Core with Aryldiazonium Salts: Synthesis of Highly Fluorescent Red‐Shifted Dyes
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Bram Verbelen Stijn Boodts Prof. Johan Hofkens Prof. Noël Boens Prof. Wim Dehaen 《Angewandte Chemie (International ed. in English)》2015,54(15):4612-4616
We describe herein the first radical C? H arylation of BODIPY dyes. This novel, general, one‐step synthetic procedure uses ferrocene to generate aryl radical species from aryldiazonium salts and allows the straightforward synthesis of brightly fluorescent (Φ>0.85) 3,5‐diarylated and 3‐monoarylated boron dipyrrins in up to 86 % yield for a broad range of aryl substituents. In this way, new and complex dyes with red‐shifted spectra can be easily prepared. 相似文献
98.
Dr. Stijn Van de Vyver Prof. Yuriy Román‐Leshkov 《Angewandte Chemie (International ed. in English)》2015,54(43):12554-12561
The use of metalloenzyme‐like zeolites as Lewis acid catalysts for C? C bond formation reactions has received increasing attention over the past few years. In particular, the observation of direct aldol condensation reactions enabled by hydrophobic zeolites with isolated framework metal sites has encouraged the development of catalytic approaches for producing chemicals from biomass‐derived compounds. The discovery of new Diels–Alder cycloaddition/dehydration routes and experimental and computational studies of Lewis acid catalyzed carbonyl–ene reactions have given a further boost to this rapidly evolving field. 相似文献
99.
Stijn Cambie Wouter Cames van Batenburg Ewan Davies Ross J. Kang 《Random Structures and Algorithms》2024,64(1):62-93
List coloring is an influential and classic topic in graph theory. We initiate the study of a natural strengthening of this problem, where instead of one list-coloring, we seek many in parallel. Our explorations have uncovered a potentially rich seam of interesting problems spanning chromatic graph theory. Given a -list-assignment of a graph , which is the assignment of a list of colors to each vertex , we study the existence of pairwise-disjoint proper colorings of using colors from these lists. We may refer to this as a list-packing. Using a mix of combinatorial and probabilistic methods, we set out some basic upper bounds on the smallest for which such a list-packing is always guaranteed, in terms of the number of vertices, the degeneracy, the maximum degree, or the (list) chromatic number of . (The reader might already find it interesting that such a minimal is well defined.) We also pursue a more focused study of the case when is a bipartite graph. Our results do not yet rule out the tantalising prospect that the minimal above is not too much larger than the list chromatic number. Our study has taken inspiration from study of the strong chromatic number, and we also explore generalizations of the problem above in the same spirit. 相似文献
100.
Walraevens Joris Van Giel Thomas De Vuyst Stijn Wittevrongel Sabine 《Queueing Systems》2022,100(3-4):221-223
Queueing Systems - We analyze the asymptotics of waiting time distributions in the two-class accumulating priority queue with general service times. The accumulating priority queue was suggested by... 相似文献