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1.
Lenaerts J Van Vaeck L Gijbels R Van Luppen J 《Rapid communications in mass spectrometry : RCM》2004,18(3):257-264
Organic carbocyanine dye coatings have been analyzed by time-of-flight static secondary ion mass spectrometry (TOF-S-SIMS) using three types of primary ions: Ga(+) operating at 25 keV, and Xe(+) and SF(5) (+) both operating at 9 keV. Secondary ion yields obtained with these three primary ions have been compared for coatings with different layer thickness, varying from (sub)-monolayer to multilayers, on different substrates (Si, Ag and AgBr cubic microcrystals). For (sub)-monolayers deposited on Ag, Xe(+) and SF(5) (+) primary ions generate similar precursor ion intensities, but with Ga(+) slightly lower precursor ion intensities were obtained. Thick coatings on Ag as well as mono- and multilayers on Si produce the highest precursor and fragment ion intensities with the polyatomic primary ion. The yield difference between SF(5) (+) and Xe(+) can reach a factor of 6. In comparison with Ga(+), yield enhancements by up to a factor of 180 are observed with SF(5) (+). For the mass spectrometric analysis of dye layers on AgBr microcrystals, SF(5) (+) again proves to be the primary ion of choice. 相似文献
2.
Abstract Broadband UV-irradiation of methylacetate isolated in argon matrices causes rather strong modifications to appear in the IR spectrum. Evidence was obtained for a photochemical interconversion of the stable Z-conformer into the less stable E-conformer followed by photolytic decomposition of the latter into stable products. Most of these products could be identified from their IR absorptions. The reverse E→Z interconversion is a thermal process with an activation energy of about 10 kJmole?1. A normal coordinate analysis based on a transferable valence force field obtained from the literature allowed to assign approximate IR frequencies of E-methylacetate. 相似文献
3.
Armand Gellis Charline Kieffer Nicolas Primas Gilles Lanzada Michel Giorgi Pierre Verhaeghe Patrice Vanelle 《Tetrahedron》2014
We report herein a new methodology for synthesizing quinazoline derivatives bearing a heteroarylamino moiety at position-4 of the quinazoline ring. As an alternative to the Buchwald–Hartwig cross-coupling reaction, which appears, until now, as the only efficient way to react 4-chloroquinazolines with numerous amino nitrogen-containing heterocycles displaying poor nucleophilicity, we developed a DMAP-catalyzed reaction involving microwave irradiation. Optimization of the reaction conditions led to the use of 30 mol % of DMAP in toluene, using a monomode microwave reactor and sealed vials. Moreover, the SNAr reaction intermediate salt was isolated and fully characterized. Finally, the procedure was extended to two different 2-substituted-quinazoline series and also to various anilines, demonstrating that this approach was a general efficient way to access to such 4-substituted quinazoline scaffolds of high pharmaceutical interest. 相似文献
4.
Eric Messens Alfons Lenaerts Marc Van Montagu André De Bruyn Arnold W.H. Jans Georges Van Binst 《Journal of carbohydrate chemistry》2013,32(4):683-699
The 1H NMR data of agrocinopine in D2O solution as extracted from standard 2D NMR experiments, along with 1D 31P and 13C NMR experiments allow to support the trisaccharide structure originally proposed on basis of comparative 13C NMR measurements. 相似文献
5.
In the present study a methodology for TOF-S-SIMS measurements is developed to gain information on the distribution of molecules on and in polymer coatings (thickness ∼100 μm). Experiments were carried out on model systems consisting of one or more additive-containing polyvinylbutyral coatings. Several organic additives were selected: carbocyanine dyes, basonyl blue and the pharmaceutical risperidone. The additives have been measured as pure compounds on a Si substrate to obtain good reference spectra. After optimisation of the sample preparation method, the coatings were embedded in epoxy resin and stored in an oven (60 °C) for 24 h. Cross-sections were made by means of a microtome. S-SIMS spectra were taken on the prepared cross-sections before and after Au was deposited on the sample surface. Compared to the untreated samples, the Au covered samples give rise to more intense secondary ion signals. Generally, signals of the intact cations were more intense than those of the fragment ions. Apart from mass spectra, images of the additive distribution in the coatings could also be acquired by recording structural ion signals. It was possible to make secondary ion images of the additive molecule ions with a (sub)-micrometer lateral resolution. 相似文献
6.
Hierarchical MoS2@TiO2 Heterojunctions for Enhanced Photocatalytic Performance and Electrocatalytic Hydrogen Evolution 下载免费PDF全文
Yu Dong Sheng‐You Chen Yi Lu Yu‐Xuan Xiao Jie Hu Si‐Ming Wu Dr. Zhao Deng Prof. Ge Tian Prof. Gang‐Gang Chang Prof. Jing Li Prof. Silvia Lenaerts Prof. Christoph Janiak Prof. Xiao‐Yu Yang Prof. Bao‐Lian Su 《化学:亚洲杂志》2018,13(12):1609-1615
Hierarchical MoS2@TiO2 heterojunctions were synthesized through a one‐step hydrothermal method by using protonic titanate nanosheets as the precursor. The TiO2 nanosheets prevent the aggregation of MoS2 and promote the carrier transfer efficiency, and thus enhance the photocatalytic and electrocatalytic activity of the nanostructured MoS2. The obtained MoS2@TiO2 has significantly enhanced photocatalytic activity in the degradation of rhodamine B (over 5.2 times compared with pure MoS2) and acetone (over 2.8 times compared with pure MoS2). MoS2@TiO2 is also beneficial for electrocatalytic hydrogen evolution (26 times compared with pure MoS2, based on the cathodic current density). This work offers a promising way to prevent the self‐aggregation of MoS2 and provides a new insight for the design of heterojunctions for materials with lattice mismatches. 相似文献
7.
Roel De Mondt Luc Van Vaeck Andreas Heile Heinrich F. Arlinghaus Frank Vangaever Jens Lenaerts 《Analytical and bioanalytical chemistry》2009,393(8):1917-1921
Recent publications on static secondary ion mass spectrometry (S-SIMS) focus on molecular depth profiling by using polyatomic
or ultra-low energy monoatomic projectiles. Since their applicability depends on the relationship between the ion yield and
the depth, which is hard to obtain without extensive studies, a combination of a wear test method with S-SIMS surface analysis
was performed in the current study. Using this non-sputtering procedure, the relation between the signal intensity and the
local concentration remains in principle the same as that at the surface (which is easy to determine). Mechanical erosion
was successfully applied to expose sub-surface material from organic multilayers. Through surface analysis with S-SIMS on
the gradually exposed deeper planes, molecular depth profiles could be obtained. The study was conducted on a model system
relevant to offset printing, consisting of two polymer layers, containing dyes and a surfactant, cast on an Al substrate.
Figure Concept of mechanical erosion followed by S-SIMS surface analysis to obtain molecular depth profiles 相似文献
8.
Particular effort has been spent in the field of identification of multi-degree-of-freedom non-linear systems. The newly developed methods permit the structural analyst to consider increasingly complex systems. The aim of this paper and a companion paper is to study, by means of two methods, a continuous non-linear system consisting of an experimental cantilever beam with a geometrical non-linearity. In this paper (Part I), the ability of the conditioned reverse path method, which is a frequency domain technique, to identify the behaviour of this structure is assessed. The companion paper (Part II) is devoted to the application of proper orthogonal decomposition, which is an updating technique, to the test example. 相似文献
9.
Lenaerts J Verlinden G Ignatova VA Van Vaeck L Gijbels R Geuens I 《Fresenius' Journal of Analytical Chemistry》2001,370(5):654-662
Secondary-ion mass spectrometry is frequently used for concentration-depth profiling of macroscopic samples, but it is certainly not a common analytical technique for the analysis of sub-micrometer-size particles. This is because of the additional ion-bombardment-induced artifacts which can occur when a three-dimensional microvolume is sputtered, instead of a flat surface. This paper presents a model of how small cubic photographic Ag(Cl,Br) crystals are eroded under primary-ion bombardment, and the extent to which secondary ions generated at different faces are extracted. The latter is studied by means of the program SIMION, which simulates ion trajectories in complex electrical field systems. It is shown that up to 90% of the secondary ions originating from the side face of a cubic crystal are unable to reach the detector, in contrast with most secondary ions originating from the top face. The angular dependence of the sputtering yield and the elemental ratio of Br/Cl sputtered particles have been calculated by using the well-known computer code TRIM (transport of ions in matter) under some limiting assumptions (possible preferential sputtering is disregarded and a steady-state sputtering process is assumed). The validity of the theoretical model and the calculated results were checked with experimental data. On the basis of the depth profiles presented it is explained why it is still possible to measure an interface inside a cubic volume, even though a group of several hundred crystals is sputtered simultaneously, and even though the orientations of the distinct faces of the cubes relative to the angle of incidence of the primary-ion beam are different. 相似文献
10.
Rituraj Borah Rajeshreddy Ninakanti Gert Nuyts Hannelore Peeters Adrián Pedrazo-Tardajos Silvia Nuti Prof. Christophe Vande Velde Prof. Karolien De Wael Prof. Silvia Lenaerts Prof. Sara Bals Prof. Sammy W. Verbruggen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(35):9011-9021
The functionalization of photocatalytic metal oxide nanoparticles of TiO2, ZnO, WO3 and CuO with amine-terminated (oleylamine) and thiol-terminated (dodecane-1-thiol) alkyl-chain ligands was studied under ambient conditions. A high selectivity was observed in the binding specificity of a ligand towards nanoparticles of these different oxides. It was observed that oleylamine binds stably to only TiO2 and WO3, whereas dodecane-1-thiol binds stably only to ZnO and CuO. Similarly, polar-to-nonpolar solvent phase transfer of TiO2 and WO3 nanoparticles could be achieved by using oleylamine, but not dodecane-1-thiol, whereas the opposite holds for ZnO and CuO. The surface chemistry of ligand-functionalized nanoparticles was probed by attenuated total reflectance (ATR)-FTIR spectroscopy, which enabled the occupation of the ligands at the active sites to be elucidated. The photostability of the ligands on the nanoparticle surface was determined by the photocatalytic self-cleaning properties of the material. Although TiO2 and WO3 degrade the ligands within 24 h under both UV and visible light, ligands on ZnO and CuO remain unaffected. The gathered insights are also highly relevant from an application point of view. As an example, because the ligand-functionalized nanoparticles are hydrophobic in nature, they can be self-assembled at the air-water interface to give nanoparticle films with demonstrated photocatalytic as well as anti-fogging properties. 相似文献