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Supramolecular arrangements of an organometallic forming nanostructured films
摘要： Drganometallic materials have become subject of intensive research on distinct technological applications. The Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) techniques have proven to be suitable to address challenges inherent to organic devices, in which the film properties can be tuned at molecular level. Here, we report on the supramolecular arrangement of zinc(OO)-protoporphyrin(OX) dimethyl ester (ZnPPOX-DME) using the Langmuir, LB and LS techniques, leading to nanostructured films. The π-A isotherms showed that π-π stacking interaction among ZnPPOX-DME molecules takes place at the air/water interface, favoring the formation of Langmuir films closely packed. The controlled growth of the LB and LS films was monitored via UV-Vis absorption spectroscopy, with the thickness per monolayer within 1.3 and 1.7 nm. The homogeneous topography found at microscale is no longer preserved at nanoscale, which is found rougher according to AFM data. The FTOR indicated that the ZnPPOX-DME is isotropically arranged on both LB and LS films.
关键词： ZnPPIX-DME,Langmuir film,Langmuir-Blodgett (LB),Langmuir-Schaefer (LS)
更新于2025-09-23 15:22:29
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High-Throughput Fingerprinting of Rhizobial Free Fatty Acids by Chemical Thin-Film Deposition and Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry
摘要： Fatty acids (FAs) represent an important class of metabolites, impacting on membrane building blocks and signaling compounds in cellular regulatory networks. In nature, prokaryotes are characterized with the most impressing FA structural diversity and the highest relative content of free fatty acids (FFAs). In this context, nitrogen-fixing bacteria (order Rhizobiales), the symbionts of legumes, are particularly interesting. Indeed, the FA profiles influence the structure of rhizobial nodulation factors, required for successful infection of plant root. Although FA patterns can be assessed by gas chromatography—(GC-) and liquid chromatography—mass spectrometry (LC-MS), sample preparation for these methods is time-consuming and quantification suffers from compromised sensitivity, low stability of derivatives and artifacts. In contrast, matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) represents an excellent platform for high-efficient metabolite fingerprinting, also applicable to FFAs. Therefore, here we propose a simple and straightforward protocol for high-throughput relative quantification of FFAs in rhizobia by combination of Langmuir technology and MALDI-TOF-MS featuring a high sensitivity, accuracy and precision of quantification. We describe a step-by-step procedure comprising rhizobia culturing, pre-cleaning, extraction, sample preparation, mass spectrometric analysis, data processing and post-processing. As a case study, a comparison of the FFA metabolomes of two rhizobia species—Rhizobium leguminosarum and Sinorhizobium meliloti, demonstrates the analytical potential of the protocol.
关键词： bacteria,metabolic fingerprinting,matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS),barium monocarboxylates,free fatty acids (FFAs),chemical deposition technique,Langmuir film technology,rhizobia
更新于2025-09-23 15:21:01
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Features of Wavelet Analysis in X-Ray Reflectometry of Thin Films
摘要： Specific features of the use of wavelet transform for estimating the thickness of layers and their order in a film density profile based on X-ray and synchrotron reflectometry data are considered. Some ways are proposed to reveal the characteristic features of Langmuir film packing by constructing a wavelet transform for the corresponding reflectograms. Dependences of the X-ray attenuation length on the grazing incidence angle are plotted by an example of multilayered box model of film profile; these dependences demonstrate possibilities of mapping the spatial signal delay (which occurs when rays are reflected from layers of different density) in a waveletgram.
关键词： wavelet transform,thin films,attenuation length,Langmuir film packing,X-ray reflectometry
更新于2025-09-23 15:21:01
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Fluorescence anisotropy imaging of a polydiacetylene photopolymer film
摘要： UV-illumination of phase-separated surfactant films prepared from mixtures of photopolymerizable 10,12-pentacosadiynoic acid and perfluorotetradecanoic acid results in the formation of fluorescent polydiacetylene fibers and aggregates. In this work, the orientation of polymer strands that comprise the resulting photopolymer structures has been probed using fluorescence anisotropy imaging in combination with defocused single-molecule fluorescence imaging. Imaging experiments indicate the presence of significant fiber-to-fiber heterogeneity, as well as anisotropy within each fiber (or aggregate), with both of these properties changing as a function of film preparation conditions. This anisotropy can be attributed to various alignments of the constituent polymer strands that comprise the larger fibers and aggregates. Intriguingly, when using defocused imaging, fiber images consisted of a series of discrete 'doughnut' fluorescence emission patterns, which exhibited intermittent on–off blinking behavior; both of these properties are characteristic of individual emission transition dipoles (single molecules). Further, all of the individual emission transition dipoles had a uniform orientation with respect to the axis of the fiber, indicating a common orientation of discrete emitters in the larger polymer fiber. The implications of these results for future studies of the electronic properties of conjugated polymers in larger macroscopic systems are noted.
关键词： 12-pentacosadiynoic acid,polydiacetylene,fluorescence anisotropy imaging microscopy,single-molecule spectroscopy,10,Langmuir film
更新于2025-09-19 17:15:36