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排序方式: 共有365条查询结果,搜索用时 484 毫秒
81.
Lupitskyy R Roiter Y Tsitsilianis C Minko S 《Langmuir : the ACS journal of surfaces and colloids》2005,21(19):8591-8593
A heteroarm star block copolymer made from seven polystyrene and seven poly(2-vinylpyridine) arms was grafted onto a solid substrate to fabricate a responsive polymer surface consisting of a densely packed monolayer of copolymer molecules. The grafted layer demonstrates a two-level hierarchical response upon external stimuli combining core-shell transitions of single stars with cooperative transitions of the interacting arms between "dimple" and "ripple" morphologies of the monolayer. The response allows for the switching of the surface properties upon changing solvent selectivity or pH of the aqueous environment. 相似文献
82.
[reaction: see text] The concecutive Criegee rearrangement reactions were studied for tert-butyl trifluoroacetate, triarylcarbinols, and benzophenone ketales with trifluoroperacetic acid (TFPAA) in trifluoroacetic acid (TFA). The formation of methyl acetate and methyl trifluoroacetate indicates that the consecutive double-O-insertion process has taken place for tert-butyl trifluoroacetate. The intermediate dimethoxymethylcarbonium ion was detected below 5 degrees C. A consecutive triple-O-insertion process has been observed for triarylmethanols and benzophenone ketals. A new high yield method of corresponding diaryl carbonates synthesis was developed. 相似文献
83.
Cascade of coil-globule conformational transitions of single flexible polyelectrolyte molecules in poor solvent 总被引:1,自引:0,他引:1
Kiriy A Gorodyska G Minko S Jaeger W Stepánek P Stamm M 《Journal of the American Chemical Society》2002,124(45):13454-13462
We show that hydrophobic flexible polyelectrolyte molecules of poly(2-vinylpyridine) and poly(methacryloyloxyethyl dimethylbenzylammonium chloride) are trapped and frozen due to adsorption on the mica surface, and the observed AFM single molecule structures reflect the molecular conformation in solution. An increase of the ionic strength of the solution induces the cascade of abrupt conformational transitions due to the intrachain segregation from elongated coil to compact globule conformations through intermediate pearl necklace-globule conformations with different amounts of beads per chain. The length of the necklaces and the number of beads decrease, while the diameter of beads increases with the increase of ionic strength. Coexistence at the same time of extended coils, necklaces with different amounts of beads, and compact globules indicates the cascade of the first-order-type phase transitions. 相似文献
84.
Minko S Kiriy A Gorodyska G Stamm M 《Journal of the American Chemical Society》2002,124(13):3218-3219
Single flexible polyelectrolyte molecules of poly(2-vinylpyridine) undergo conformational transition from a stretched wormlike coil to a necklace-like globule, and to a compact globule depending on pH and ionic strength in aqueous solution in good agreement with recent theoretical reports. AFM investigations allow the visualization of details of the chain conformation on mica and the extraction of quantitative statistics of molecular dimensions. 相似文献
85.
The work deals with the problem of determination of automobile petrol of various octane numbers and petroleum contamination of some objects on the basis of analysis of photoluminescence spectra of automobile petrol samples. For this purpose steady state luminescence properties of samples of automobile petrol of different types being in sale were measured. Samples of automobile petrol diluted in hexane were prepared and their luminescence spectra were measured at room and liquid nitrogen temperatures of samples. We constructed concentration dependences of luminescence intensity of both wide band luminescence of liquid solutions obtained at room temperature and peak intensities of luminescence lines of quasi linear spectra of solutions frozen at 77 K. Possibility to use luminescence method for analysis of petrol pollutions on some objects is illustrated by results of investigation of pine-wood pieces contaminated by automobile petrol. 相似文献
86.
87.
Olga I. Kalchenko Sergiy O. Cherenok Andriy V. Solovyov Vitaly I. Kalchenko 《Chromatographia》2009,70(5-6):717-721
The addition of calix[4]arenes to MeCN/H2O or MeOH/MeCN/THF/H2O mobile phases improves LC separation of benzene or uracil derivatives on Separon SGX C18 or Separon SGX NH2 supports. Structure of the calixarenes and their host–guest supramolecular complexes with the analytes are discussed in context of the LC separation. 相似文献
88.
89.
Inside Back Cover: A Major Advance in the Synthesis of Fluoroalkyl Pyrazoles: Tuneable Regioselectivity and Broad Substitution Patterns (Chem. Eur. J. 32/2016)
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90.
Sergiy Patskovsky Anne‐Marie Dallaire Andre‐Pierre Blanchard‐Dionne Alexis Vallée‐Bélisle Michel Meunier 《Annalen der Physik》2015,527(11-12):806-813
In this article, the implementation of electrochemical plasmonic nanostructures functionalized with DNA‐based structure‐switching sensors is presented. eNanoSPR devices with open and microfluidic measurement cells are developed on the base of nanohole arrays in 100 nm gold film and applied for combined microscopic and electrochemical surface plasmon (eSPR) visualization. eSPR voltammograms and spectroscopy are performed using planar three electrode schematic with plasmonic nanostructure operated as working electrode. Limit of detection of eNanoSPR devices for oligonucleotide hybridization is estimated in the low nanomolar and applications for structure‐switching electro‐plasmonic sensing in complex liquids are discussed. 相似文献