Mesostructured Arrays of Nanometer‐spaced Gold Nanoparticles for Ultrahigh Number Density of SERS Hot Spots

A novel one‐trough synthesis via an air‐water interface is demonstrated to provide hexagonally packed arrays of densely spaced metallic nanoparticles (NPs). In the synthesis, a mesostructured polyoxometalate (POM)‐silicatropic template (PSS) is first self‐assembled at the air‐water interface; upon UV irradiation, anion exchange cycles enable the free‐floating PSS film to continuously uptake gold precursors from the solution subphase for diffusion‐controlled and POM‐site‐directed photoreduction inside the silica channels. NPs ≈ 2 nm can hence be homogeneously formed inside the silica‐surfactant channels until saturation. As revealed via X‐ray diffraction, small‐angle X‐ray scattering (SAXS), grazing incidence SAXS, and transmission electron microscopy, the Au NPs directed by the PSS template are arrayed into a 2D hexagonal lattice with inter‐channel spacing of 3.2 nm and a mean along‐channel NP spacing of 2.8 nm. This corresponds to an ultra‐high number density (≈10¹⁹ NPs cm^?3) of narrowly spaced Au NPs in the Au‐NP@PSS composite, leading to 3D densely deployed hot‐spots along and across the mesostructured POM‐silica channels for surface‐enhanced Raman scattering (SERS). Consequently, the Au‐NP@PSS composite exhibits prominent SERS with 4‐mercaptobenzoic acid (4‐MBA) adsorbed onto Au NPs. The best 4‐MBA detection limit is 5 nm , with corresponding SERS enhancement factors above 10⁸.     

Availability Analysis of a Fault-Tolerant Computer System

Queueing network theory is applied in order to determine the availability of a fault-tolerant multiprocessor computer system. Mean repair times and utilizations of system units are computed. Subsystem availabilities are obtained by the decomposition technique of queueing network theory.     

Azide‐based Cross‐Linking of Polymers of Intrinsic Microporosity (PIMs) for Condensable Gas Separation

Cross‐linked polymers of intrinsic microporosity (PIM)s for gas separation membranes, were prepared by a nitrene reaction from a representative PIM in the presence of two different diazide cross‐linkers. The reaction temperature was optimized using TGA. The homogenous membranes were cast from THF solutions of different ratios of PIM to azides. The resulting cross‐linked structures of the PIMs membranes were formed at 175 °C after 7.5 h and confirmed by TGA, XPS, FT‐IR spectroscopy and gel content analysis. These resulting cross‐linked polymeric membranes showed excellent gas separation performance and can be used for O₂/N₂ and CO₂/N₂ gas pairs, as well as for condensable gases, such as CO₂/CH₄, propylene/propane separation. Most importantly, and differently from typical gas separation membranes derived from glassy polymers, the crosslinked PIMs showed no obvious CO₂ plasticization up to 20 atm pressure of pure CO₂ and CO₂/CH₄ mixtures.

     

Dansyl and dabsyl analytical constructs as tools for the accurate estimation of compounds in solid-phase synthesis

The presence of dansyl or dabsyl chromogenic moieties in a solid-phase analytical construct, an assembly of linkers/spacers/sensitizers for improving analytical characterization, allows the accurate estimation of products from solid-phase synthesis by UV detection during liquid chromatography-mass spectrometry analysis in the cleavage solution. The spectroscopic properties of dansylated molecules have been evaluated to verify the "compound-independent UV absorption" necessary for using the chromophore in the accurate estimation. First, measurements on commercial dansylated compounds were made, then a series of construct-like molecules were prepared by solution-phase synthetic procedures and their UV properties were determined. Compound calibration curves were determined, and UV absorption was shown to be both proportional to the compound concentration and compound-independent. An example of a dansyl construct derivative was then prepared on a polymeric matrix, and an accurate estimation using the calibration curves was carried out in the cleavage solution. Good agreement was found between the calculated amount of released compound using the UV calibration curves and the calculated amount using both (1)H NMR and LC/chemiluminescent nitrogen detection quantitative techniques. Preliminary studies using the dabsyl moiety as an improved chromophore with higher wavelength and extinction coefficient are also reported.     

Synthesis,Crystal Structure and Thermal Properties of <Emphasis Type="Italic">N</Emphasis>-Acetyl-3-(2-furyl)-5-ferrocenyl-2-pyrazoline and <Emphasis Type="Italic">N</Emphasis>-Acetyl-3-(2-thienyl)-5-ferrocenyl-2-pyrazoline

Abstract  

Two novel ferrocenyl substituted N-acetyl-2-pyrazolines, N-acetyl-3-(2-furyl)-5-ferrocenyl-2-pyrazoline (3) and N-acetyl-3-(2-thienyl)-5-ferrocenyl-2-pyrazoline (4), have been synthesized and characterized by FTIR, ¹H-NMR, ¹³C-NMR techniques, elemental analysis and X-ray structure analysis. Thermal properties of these compounds have been determined by TGA, DTA and DSC analysis. Compound 3 (C₁₉H₁₈N₂O₂Fe) crystallizes in the monoclinic space group P21/c and Z = 4, with a = 8.6970(4) ?, b = 18.4725(9) ?, c = 11.0041(5) ?, β = 110.942(3)°. Compound 4 (C₁₉H₁₈N₂OSFe) crystallizes in the orthorhombic space group Fdd2 and Z = 16, with a = 84.242(2) ?, b = 13.5416(5) ?, c = 5.9405(2) ?, β = 90°. In terms of crystal packing, each compound shows different molecular arrangement, which are stabilized by C–H···O intermolecular weak hydrogen bonds, and/or C–H···π interactions.     

The Synthesis and Structure of Two Novel <Emphasis Type="Italic">N</Emphasis>-(Benzothiazol-2-yl)benzamides

Abstract  Two novel benzothiazoles 2-chloro-N-(benzothiazol-2-yl)benzamide (1) and 2-chloro-N-(6-cyanobenzothiazol-2-yl)benzamide (2) were obtained in multistep synthesis. They were characterised by means of IR, ¹H- and ¹³C-NMR spectroscopy and also by single-crystal X-ray diffraction. The compound 1 crystallises with triclinic space group P , a = 9.5923(8) ?, b = 9.8583(8) ?, c = 13.8962(10) ?, α = 89.162(6)°, β = 77.741(7)°, γ = 80.064(7)°, V = 1264.5(2) ?³, Z = 4 and compound 2 crystallises as methanol solvate with monoclinic space group P 2₁/n, a = 7.5093(9) ?, b = 13.0211(14) ?, c = 16.032(2) ?, β = 92.717(10)°, V = 1565.9(3) ?³, Z = 4. Both crystal structures consist of discrete dimers connected into a three-dimensional network by intermolecular C–H···O and C–H···X (X = Cl or S) hydrogen bonds and by face-to-face π–π stacking interactions. Index Abstract  The synthesis and structure of two novel N-(benzothiazol-2-yl)benzamides. Irena Ćaleta, Dominik Cinčić, GraceKarminski-Zamola and Branko Kaitner. Hydrogen bonds and π–π interactions in N-(benzothiazol-2-yl)benzamides N-(benzothiazol-2-yl)benzamides.      

New insight into solid-state molecular dynamics: mechanochemical synthesis of azobenzene/triphenylphosphine palladacycles

Solid-state reactions of dicyclopalladated azobenzenes and triphenylphosphine lead to the thermodynamically favorable bridged complexes. It was demonstrated for the first time that very complex molecular dynamics involving a series of structural transformations is also feasible in the solid state.     

A model of self-supervision

Systems which supervise their behavior by themselves play an increasingly important role, for example in the field of data processing. Self-checking is normally carried out by means of on-line and/or periodical testing. These self-tests, however, are not absolutely reliable as system defects will influence the self-test mechanism. Based on a model of self-supervising systems with periodical self-tests and renewals the diagnosability, the mean up time, and the optimal test interval with respect to cost are determined.

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Zusammenfassung Systeme, die ihre Funktionsweise selbsttätig überwachen können, spielen eine immer größere Rolle vor allem auch auf dem Gebiet der Datenverarbeitung. Selbstüberwachung basiert in der Regel auf funktionsbegleitenden und/oder periodisch durchgeführten Selbsttests. Diesen Selbsttests kann jedoch nicht voll vertraut werden, da Systemdefekte auch den Selbsttestmechanismus beeinflussen können. Anhand eines Modells eines sich selbstüberwachenden Systems mit periodischen Selbsttests und Erneuerungsmöglichkeit wird die Diagnostizierbarkeit, die mittlere Intaktzeit und das kostenoptimale Testintervall bestimmt.