Catalytic and antibacterial evaluation of silver nanoparticles synthesized by a green approach

In this work, silver nanoparticles were synthesized using Salvia microphylla Kunth leaves extract as reducing agent and stabilizing agent. The effect of reaction time and plant extract amount on the biosynthesized nanoparticles were studied. The UV–Vis spectrum indicated that silver nanoparticles show a characteristic surface plasmon resonance at 427 nm. X-ray diffraction experiments show that the silver nanoparticles have a face-centered cubic crystal structure. The density of nanoparticles increases with increasing extract concentration and reaction time. TEM and SEM observations showed well-dispersed quasi-spherical nanoparticles sized in the range of 15–45 nm. The FT-IR analysis suggested the involvement of phenolic compounds in the reduction and stabilization of silver nanoparticles. Synthesized silver nanoparticles showed good antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Finally, the catalytic properties of silver nanoparticles were demonstrated through the degradation of congo red and methyl orange.     

Color and fastness of natural dyes encapsulated by a sol-gel process for dyeing natural and synthetic fibers

Natural dyes, namely, indigo carmine, cochineal carmine, curcumin and annatto, were encapsulated in silica by a sol-gel method and applied in the dyeing of different textile fibers by exhaustion. For comparative reasons, dyeing using the free (non-encapsulated) bare dyes was also carried out. The hybrid materials were analyzed by a set of techniques to investigate their elemental, structural, textural and morphological properties, and the results showed that it was possible to obtain stable natural dyes for applications in textile dyeing. The silica-structured dyes showed better affinities with the fibers (WO, PA, PAC and PET) in dyeing with cochineal carmine, while cotton (CO) showed better affinities with the encapsulated curcumin and annatto dyes. The performances of the encapsulated dyes were evaluated by color and washing fastness measurements and resulted in improved dye absorption and wash fastness properties. The color change and color transfer measurements of the encapsulated dyes were better (rated at 4–5 on a scale of 1–5) compared to the bare dyes.

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Palladium-catalyzed olefin migration and 7-endo-trig cyclization of dehydroalanines

1,4- or 1,5-migration of a double bond of dehydroalanines under palladium catalysis is reported. The process occurred with several highly-substituted dehydroalanines under mild typical Heck reaction conditions. Although this was one of the first reports of a palladium-catalyzed 1,5-olefin migration, the outcome of the reaction was susceptible to the starting material. Mechanistically, the process involved a five- (1,4-migration) or six-membered ring (1,5-migration) organopalladium intermediate, which cleaved a C–N bond in an β-amino elimination process.     

Synthesis of Bifunctional Allylic Compounds by Using Cyclopropenes as Functionalized Allyl Equivalents

The synthesis of uncommon bifunctional allylic derivatives bearing a silane and an alcohol within the same allylic framework is reported. This method relies on the coupling of hydrosilanes with substituted and functionalized cyclopropenes, which deliver the allyl fragment. Rhodium(II) catalysts provide regioselective access to vinyl carbene intermediates, which easily undergo Si?H bond insertions. The transformation occurs with complete atom economy and shows a remarkably broad scope, including a intramolecular version for the synthesis of cyclic O?Si‐linked compounds as well as the synthesis of the corresponding allyl amines.     

Multi-electrode Harmonized Kingdon Traps

Based on the analysis of the results of the study of various designs of multi-electrode harmonized Kingdon traps, we propose a new type of trap with two merged internal electrodes that has the ability to capture and accumulate ions formed inside. We also investigated the influence of inaccuracies in the manufacture of the electrodes on the field inside such trap. The four-electrode trap, which actually degenerates into a two-electrode device with traces of two other electrodes present at the ends of the internal electrodes (their splitting) has been found as the less sensitive to inaccuracies caused by manufacturing and cutting the ends of trap electrodes. We show that a mass spectrometer with a relatively high resolving power can be created on the basis of such a trap. The creation of the traps requires the manufacture of complex electrodes with demanded accuracy of their surfaces. This becomes possible with the advent of 3D printers.

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Graphical Abstract Multi electrode harmonize Kingdon trap with fused elctrode pares

     

Reversible Clustering of Gold Nanoparticles under Confinement

A limiting factor of solvent‐induced nanoparticle self‐assembly is the need for constant sample dilution in assembly/disassembly cycles. Changes in the nanoparticle concentration alter the kinetics of the subsequent assembly process, limiting optical signal recovery. Herein, we show that upon confining hydrophobic nanoparticles in permeable silica nanocapsules, the number of nanoparticles participating in cyclic aggregation remains constant despite bulk changes in solution, leading to highly reproducible plasmon band shifts at different solvent compositions.     

Pyrrole β-amides: Synthesis and characterization of a dipyrrinone carboxylic acid and an N-Confused fluorescent dipyrrinone

Pyrrole β-amides are useful building blocks for the preparation of novel molecular architectures that can be used in supramolecular chemistry and sensor development. Under basic conditions, pyrrole β-amides with an α-aldehyde produce different condensation products when reacted with pyrrolinones depending on the amide substitution. Secondary amides form the expected dipyrrinones, but unexpectedly undergo a subsequent trans-amidation with the pyrrolinone nitrogen to produce an unsymmetrical imide (an N-confused fluorescent dipyrrinone). Under the same conditions, tertiary amides produce the expected dipyrrinone carboxylic acids, which have been shown to have strong self-association properties as determined by vapor pressure osmometry measurements, NMR studies, and X-ray crystal structure determination. Furthermore, an N-confused fluorescent dipyrrinone was produced from the same trans-amidation reaction during attempts to decarboxylate a dipyrrinone amide with a 9-carboxylic moiety.     

On universal entire functions with zero-free derivatives

We prove in this note a generalization of a theorem due to G. Herzog on zero-free universal entire functions. Specifically, it is shown that, if a nonnegative integer q and a nonconstant entire function φ of subexponential type are given, then there is a residual set in the class of entire functions with zero-free derivatives of orders q and q + 1, such that every member of that set is universal with respect to φ (D), where D is the differentiation operator. This work is supported in part by DGICYT grant PB93-0926.     

Le polymorphisme du picrate d'atropine

Résumé On a étudié le système atropine-acide picrique et obtenu son diagramme de fusion. On signale une nouvelle forme cristalline de picrate d'atropine fondant à 147°. Le point de transformation de cette forme en la forme stable se trouve aux environs de 95°. On met en évidence une segrégation des phases à 152° et fournit 188°, avec un léger doute, comme température critique de dissolution.

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Summary The atropine-picric acid system has been studied and its fusion diagram has been obtained. A new crystalline form of atropine picrate has been pointed out; it melts at 147°. The transformation point of this form into the stable form is around 95°. There is a segregation of phases at 152° and the critical temperature of solution is given, with a slight doubt, as 188°.

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Zusammenfassung Das System Atropin-Pikrinsäure wurde untersucht und dessen Schmelzdiagramm festgelegt. Hierbei zeigte sich eine neue Kristallform des Atropinpikrates mit dem Fp. 147°. Die Umwandlungstemperatur dieser Kristallform in das stabile Pikrat wurde bei etwa 95° gefunden. Bei 152° tritt eine Mischungslücke auf; die kritische Lösungstemperatur wurde bei etwa 188° festgelegt.

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Avec 1 figure.