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排序方式: 共有243条查询结果,搜索用时 0 毫秒
21.
Marek Stach Zuzana KronekováPeter Kasák Jozef KollárMartin Pentrák Matej Mi?ušíkDušan Chorvát Jr. Tim S. NunneyIgor Lacík 《Applied Surface Science》2011,257(24):10795-10801
The sulfobetaine films were prepared on stainless steel and golden surfaces. In the first step, the poly(2-(dimethylamino)ethyl methacrylate) film was created by employing the electrografting polymerization technique. In the second step, this film was modified to polysulfobetaine, i.e. the polymer film bearing the zwitterionic groups. The presence of the electrografted film and its modification were determined by contact angle measurements, infrared spectroscopy in reflectance mode and X-ray photoelectron spectroscopy. The prepared films were homogeneous with the thickness from about 5 to 26 nm as determined by X-ray photoelectron spectroscopy. The atomic force microscopy measurements showed the increase of surface roughness upon the surface coating. In vitro tests using adherent RAT-2 fibroblast cells and fluorescently labelled bovine serum albumin proteins showed that prepared polysulfobetaine films can be used in applications requiring the resistance against cell attachment and biofouling. 相似文献
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Recently, Balogh et al. (2018) answered in negative the question that was posed in several earlier papers whether the packing chromatic number is bounded in the class of graphs with maximum degree 3. In this note, we present an explicit infinite family of subcubic graphs with unbounded packing chromatic number. 相似文献
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Dr. Matej Huš Dr. Miha Grilc Dr. Janvit Teržan Dr. Sašo Gyergyek Prof. Blaž Likozar Prof. Anders Hellman 《Angewandte Chemie (International ed. in English)》2023,62(31):e202305804
Ethylene epoxidation is industrially and commercially one of the most important selective oxidations. Silver catalysts have been state-of-the-art for decades, their efficiency steadily improving with empirical discoveries of dopants and co-catalysts. Herein, we perform a computational screening of the metals in the periodic table, identify prospective superior catalysts and experimentally demonstrate that Ag/CuPb, Ag/CuCd and Ag/CuTl outperform the pure-Ag catalysts, while they still confer an easily scalable synthesis protocol. Furthermore, we show that to harness the potential of computationally-led discovery of catalysts fully, it is essential to include the relevant in situ conditions e.g., surface oxidation, parasitic side reactions and ethylene epoxide decomposition, as neglecting such effects leads to erroneous predictions. We combine ab initio calculations, scaling relations, and rigorous reactor microkinetic modelling, which goes beyond conventional simplified steady-state or rate-determining modelling on immutable catalyst surfaces. The modelling insights have enabled us to both synthesise novel catalysts and theoretically understand experimental findings, thus, bridging the gap between first-principles simulations and industrial applications. We show that the computational catalyst design can be easily extended to include larger reaction networks and other effects, such as surface oxidations. The feasibility was confirmed by experimental agreement. 相似文献
25.
Novel type of Pd(II)-catalysed transformation of sugar-derived alkenitols furnishing 7-benzyloxy-2,5-dioxabicyclo[2.2.1]heptanes was discovered. The investigated bicyclisation displays an exceptional substrate selectivity towards xylo-configured unsaturated polyols. Moreover, a newly build stereogenic centre is formed in a diastereospecific cis-manner. The observed stereochemical preference was corroborated by modelling of pertinent transition states at the semiempirical level of theory (PM5). In addition, the single crystal X-ray analysis of an acylated analogue d-glycero-l-gulo-21 was done in order to establish the relative configuration of related bicyclic products. 相似文献
26.
Kargl R Mohan T Bračič M Kulterer M Doliška A Stana-Kleinschek K Ribitsch V 《Langmuir : the ACS journal of surfaces and colloids》2012,28(31):11440-11447
The adsorption of carboxymethyl cellulose (CMC), one of the most important cellulose derivatives, is crucial for many scientific investigations and industrial applications. Especially for surface modifications and functionalization of materials, the polymer is of interest. The adsorption properties of CMC are dependent not only on the solutions state, which can be influenced by the pH, temperature, and electrolyte concentration, but also on the chemical composition of the adsorbents. We therefore performed basic investigation studies on the interaction of CMC with a variety of polymer films. Thin films of cellulose, cellulose acetate, deacetylated cellulose acetate, polyethylene terephthalate, and cyclo olefin polymer were therefore prepared on sensors of a QCM-D (quartz crystal microbalance) and on silicon substrates. The films were characterized with respect to the thickness, wettability, and chemical composition. Subsequently, the interaction and deposition of CMC in a range of pH values without additional electrolyte were measured with the QCM-D method. A comparison of the QCM-D results showed that CMC is favorably deposited on pure cellulose films and deacetylated cellulose acetate at low pH values. Other hydrophilic surfaces such as silicon dioxide or polyvinyl alcohol coated surfaces did not adsorb CMC to a significant extent. Atomic force microcopy confirmed that the morphology of the adsorbed CMC layers differed depending on the substrate. On hydrophobic polymer films, CMC was deposited in the form of larger particles in lower amounts whereas hydrophilic cellulose substrates were to a high extent uniformly covered by adsorbed CMC. The chemical similarity of the CMC backbone seems to favor the irreversible adsorption of CMC when the molecule is almost uncharged at low pH values. A selectivity of the cellulose CMC interaction can therefore be assumed. All CMC treated polymer films exhibited an increased hydrophilicity, which confirmed their modification with the functional molecule. 相似文献
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This study deals with O2− generation in corona discharge (CD) in point to plane geometry for single flow ion mobility spectrometry (IMS) with gas outlet located behind the ionization source. We have designed CD of special geometry in order to achieve the high O2− yield. Using this ion source we have achieved in zero air conditions that up to 74% all negative ions were O2− or O2−(H2O). It has been demonstrated that the non-electronegative nitrogen positively influences the efficiency of O2− generation in O2/N2 mixtures. The reduced ion mobility of 2.27 cm2 V−1 s−1 has been measured for O2−/O2−(H2O) ions in zero air. Additional ions detected in zero air (less than 200 ppb CO2) using the mass spectrometric and IMS technique were, NO2−, N2O2− (2.37 cm2 V−1 s−1), NO3−, N2O3− and N2O3−(H2O). The CO3− and CO4− ions have been detected after the introduction of 5 ppm CO2 into zero air. 相似文献
30.
Karamov O. G. Rybalkin V. P. Makarova N. I. Metelitsa A. V. Kozyrev V. S. Borodkin G. S. Popova L. L. Breń V. A. Minkin V. I. 《Russian Chemical Bulletin》2011,60(1):168-174
New dihetarylethenes containing the six-membered bridging moiety, viz., N
2-alkyl-5-furyl-4-thienylpyridazinones, were synthesized. These compounds have photochromic properties in solution. The hindered
rotation of the thiophene and furan rings around the single bonds that link these rings to the double bond of the pyridazinone
moiety results in the formation of mixtures of chiral diastereomers in solution, the lifetimes of the diastereomers being
no longer than 0.2 s. The photochromic rearrangement of pyridazinones is characterized by the highly efficient photocoloration
and the photobleaching, which is an order of magnitude less efficient, in the absence of thermal relaxation processes. 相似文献