Far-red triplet sensitized Z-to-E photoswitching of azobenzene in bioplastics

We report the first example of direct far-red triplet sensitized molecular photoswitching in a condensed phase wherein a liquid azobenzene derivative (Azo1) co-assembled within a liquid surfactant–protein film undergoes triplet sensitized Z-to-E photoswitching upon far-red/red light excitation in air. The role of triplet sensitization in photoswitching has been confirmed by quenching of sensitizer phosphorescence by Z-Azo1 and temperature-dependent photoswitching experiments. Herein, we demonstrate new biosustainable fabrication designs to address key challenges in solid-state photoswitching, effectively mitigating chromophore aggregation and requirement of high energy excitations by dispersing the photoswitch in the trapped liquid inside the solid framework and by shifting the action spectrum from blue-green light (450–560 nm) to the far-red/red light (740/640 nm) region.

We report the first example of direct far-red endothermic triplet sensitized Z-to-E photoswitching of azobenzene derivative (Azo1) in a condensed phase of a liquid Azo1 co-assembled within a liquid surfactant-protein bioplastic film in air.     

An Enantiopure Cyclometallated Iridium Complex Displaying Long‐Lived Phosphorescence both in Solution and in the Solid State

A new enantiopure cyclometallated iridium complex bearing a [4]helicenic ‐coordinating and two ‐coordinating dfppy (2‐(2,4‐difluorophenyl)‐pyridyl) ligands was prepared. This complex displayed long‐lived phosphorescence both in solution and in the solid state. Its chiroptical properties, namely electronic circular dichroism and circularly polarized luminescence, were also examined. Comparison with former chiral complexes enabled assignment of the Δ_Ir‐(?) and Λ_Ir‐(+) absolute configurations.     

Analysis of changes in attenuated total reflection FTIR fingerprints of Pseudomonas fluorescens from planktonic state to nascent biofilm state

Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy is a useful method for monitoring biofilm in situ, non-destructively, in real time, and under fully hydrated conditions. In this work we focused on changes in Pseudomonas fluorescens ATR-FTIR fingerprint accompanying the very early stages of biofilm formation: initial bacterial adhesion and the very beginning of biofilm development in the presence of nutrients. To help interpreting variations in the ATR-FTIR fingerprint of sessile bacteria, ATR-FTIR spectra of planktonic bacteria in different growth phases were also examined, and the average surface coverage and spatial arrangement of bacteria on the ATR crystal were determined by epifluorescence microscopy. The proteins, nucleic acids and polysaccharides ATR-FTIR spectral data recorded during growth of sessile bacteria were shown to be linked to changes in the physiological state of the bacteria, possibly accompanied by extracellular polymeric substances production. This work clearly showed by spectroscopic method how bacteria change drastically their metabolism during the first hours of biofilm formation.     

Engineered inorganic core/shell nanoparticles

It has been for a long time recognized that nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic structures. At first, size effects occurring in single elements have been studied. More recently, progress in chemical and physical synthesis routes permitted the preparation of more complex structures. Such structures take advantages of new adjustable parameters including stoichiometry, chemical ordering, shape and segregation opening new fields with tailored materials for biology, mechanics, optics magnetism, chemistry catalysis, solar cells and microelectronics. Among them, core/shell structures are a particular class of nanoparticles made with an inorganic core and one or several inorganic shell layer(s). In earlier work, the shell was merely used as a protective coating for the core. More recently, it has been shown that it is possible to tune the physical properties in a larger range than that of each material taken separately. The goal of the present review is to discuss the basic properties of the different types of core/shell nanoparticles including a large variety of heterostructures. We restrict ourselves on all inorganic (on inorganic/inorganic) core/shell structures. In the light of recent developments, the applications of inorganic core/shell particles are found in many fields including biology, chemistry, physics and engineering. In addition to a representative overview of the properties, general concepts based on solid state physics are considered for material selection and for identifying criteria linking the core/shell structure and its resulting properties. Chemical and physical routes for the synthesis and specific methods for the study of core/shell nanoparticle are briefly discussed.     

Multi-step reactions of N-monosubstituted (polyfluoroalkane)thioamides with alkyllithium reagents

Reactions of N-alkyl- or N-aryl(perfluoroalkyl)thiocarboxamides with alkyl lithium reagents are described. Trifluorothioacetamides are converted into the corresponding lithium salts. Compounds bearing a long polyfluorinated chain terminated by a CHF₂ group and compounds containing an N-alkyl substituent with a proton adjacent to nitrogen react further via a multi-step reaction sequence involving HF elimination and then vinylic fluorine substitution and/or S_N′ type fluorine substitution. These transformations led to unsaturated N-monosubstituted polyfluorinated thioamides.     

Comparative structural analysis of 4,5- and 3,6-dialkylsulfanylphthalonitriles of different bulkiness

Phthalonitriles disubstituted by alkylsulfanyl moieties of different bulkiness (tert-butyl, adamantly, cyclohexyl and hexyl) and in 4,5- or 3,6-positions, respectively, set A and set B, have been prepared for comparative structural analyses. Miscellaneous parameters such as melting points and related polarity of the compounds are summarized. Substituents position and bulkiness effects on NMR and IR spectroscopy as well as refined X-ray structural data were examined.     

Synthetic Usefulness of the Sugar Cyclopentylidene Ketals

ABSTRACT

Cyclopentylidene ketals, moderately more acid-labile than their isopropylidene analogs, offer an alternative to the latter blocking groups. They have been shown to resist a large variety of reaction conditions commonly encountered in carbohydrate chemistry.     

Large deviations for Brownian motion in a random scenery

We prove large deviations principles in large time, for the Brownian occupation time in random scenery . The random field is constant on the elements of a partition of ^d into unit cubes. These random constants, say consist of i.i.d. bounded variables, independent of the Brownian motion {B_s,s0}. This model is a time-continuous version of Kesten and Spitzer's random walk in random scenery. We prove large deviations principles in ``quenched' and ``annealed' settings.Mathematics Subject Classification (2000):60F10, 60J55, 60K37