Plasmonic properties of silver nanostructures coated with an amorphous silicon-carbon alloy and their applications for sensitive sensing of DNA hybridization

The use of an amorphous silicon-carbon alloy overcoating on silver nanostructures in a localized surface plasmon resonance (LSPR) sensing platform allows for decreasing the detection limit by an order of magnitude as compared to sensors based on gold nanostructures deposited on glass. In addition, silver based multilayer structures show a distinct plasmonic behaviour as compared to gold based nanostructures, which provides the sensor with an increased short-range sensitivity and a decreased long-range sensitivity.     

Crystallization mechanism of hard sphere glasses

In supercooled liquids, vitrification generally suppresses crystallization. Yet some glasses can still crystallize despite the arrest of diffusive motion. This ill-understood process may limit the stability of glasses, but its microscopic mechanism is not yet known. Here we present extensive computer simulations addressing the crystallization of monodisperse hard-sphere glasses at constant volume (as in a colloid experiment). Multiple crystalline patches appear without particles having to diffuse more than one diameter. As these patches grow, the mobility in neighboring areas is enhanced, creating dynamic heterogeneity with positive feedback. The future crystallization pattern cannot be predicted from the coordinates alone: Crystallization proceeds by a sequence of stochastic micronucleation events, correlated in space by emergent dynamic heterogeneity.     

Cationic Biphotonic Lanthanide Luminescent Bioprobes Based on Functionalized Cross-Bridged Cyclam Macrocycles

Cationic lanthanide complexes are generally able to spontaneously internalize into living cells. Following our previous works based on a diMe-cyclen framework, a second generation of cationic water-soluble lanthanide complexes based on a constrained cross-bridged cyclam macrocycle functionalized with donor-π-conjugated picolinate antennas was prepared with europium(III) and ytterbium(III). Their spectroscopic properties were thoroughly investigated in various solvents and rationalized with the help of DFT calculations. A significant improvement was observed in the case of the Eu³⁺ complex, while the Yb³⁺ analogue conserved photophysical properties in aqueous solvent. Two-photon (2P) microscopy imaging experiments on living T24 human cancer cells confirmed the spontaneous internalization of the probes and images with good signal-to-noise ratio were obtained in the classic NIR-to-visible configuration with the Eu³⁺ luminescent bioprobe and in the NIR-to-NIR with the Yb³⁺ one.     

Comparative Analysis of Conjugated Alkynyl Chromophore–Triazacyclononane Ligands for Sensitized Emission of Europium and Terbium

A series of europium and terbium complexes based on a functionalized triazacyclononane carboxylate or phosphinate macrocyclic ligand is described. The influence of the anionic group, that is, carboxylate, methylphosphinate, or phenylphosphinate, on the photophysical properties was studied and rationalized on the basis of DFT calculated structures. The nature, number, and position of electron‐donating or electron‐withdrawing aryl substituents were varied systematically within the same phenylethynyl scaffold in order to optimize the brightness of the corresponding europium complexes and investigate their two‐photon absorption properties. Finally, the europium complexes were examined in cell‐imaging applications, and selected terbium complexes were studied as potential oxygen sensors.     

Core‐shell type dually fluorescent polymer nanoparticles for ratiometric pH‐sensing

The synthesis and pH‐sensing properties of fluorescent polymer nanoparticles (NPs) in the 20 nm diameter range with a sensitive dye covalently attached to the particle surface and a reference dye entrapped within the particle core are presented. Fluorescein‐functionalized NPs were readily obtained by conjugation of fluorescein isothiocyanate (FITC) to amine‐coated crosslinked polystyrene‐based nanoparticles prepared by microemulsion polymerization followed by postfunctionalization. This all water‐based method gave access to stable aqueous suspensions of pH‐sensing fluorescent NPs. The encapsulation of the insensitive reference fluorescent dye (1,9‐diphenylanthracene, DPA) was then conveniently achieved by soaking leading to dual fluorescent NPs containing about 20 DPA and 55 fluorescein, as deduced from spectroscopic analyses. This core‐shell type architecture maximizes the interactions of the sensing dye with the medium while protecting the reference dye. The variations of the ratio of the fluorescence emission intensities of the sensitive dye (fluorescein) to the reference dye (DPA) with pH show that the dual fluorescent NPs act as a ratiometric pH sensor with a measuring range between pH 4 and pH 8. This pH nanosensor was found to be fast, fully reversible, and robust without any leaching of dye over a long period of time. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6206–6213, 2008     

Chiralization in mesogenic 1,3-diacylaminobenzenes

The effect of molecular chirality in thermotropic mesomorphic H-bonded polymeric systems has not really been investigated so far. Therefore, five new chiral mesogenic diamides have been prepared and described. Besides more ordered mesophases, the enantiomers exhibit a chiral nematic polymorphism detected by microcalorimetry and probably corresponding to different modes of chiral coiling to give these singular twisted nematic phases.     

Comparing the 2,2′‐Biphenylenedithiophosphinate Binding of Americium with Neodymium and Europium

Advancing our understanding of the minor actinides (Am, Cm) versus lanthanides is key for developing advanced nuclear‐fuel cycles. Herein, we describe the preparation of (NBu₄)Am[S₂P(^tBu₂C₁₂H₆)]₄ and two isomorphous lanthanide complexes, namely one with a similar ionic radius (i.e., Nd^III) and an isoelectronic one (Eu^III). The results include the first measurement of an Am?S bond length, with a mean value of 2.921(9) Å, by single‐crystal X‐ray diffraction. Comparison with the Eu^III and Nd^III complexes revealed subtle electronic differences between the complexes of Am^III and the lanthanides.     

A novel small molecule that alters shelterin integrity and triggers a DNA-damage response at telomeres

We describe a novel synthetic small molecule which shows an unprecedented stabilization of the human telomeric G-quadruplex with high selectivity relative to double-stranded DNA. We report that this compound can be used in vitro to inhibit telomerase activity and to uncap human POT1 (protection of telomeres 1) from the telomeric G-overhang. We also show that the small molecule G-quadruplex binder induces a partial alteration of shelterin through POT1 uncapping from telomeres in human HT1080 cancer cells and the presence of gammaH2AX foci colocalized at telomeres.     

Synthesis, and two photon absorption properties of 7,7'-(iminundecahydro-closo-dodecaborate)-9,9'-(dihexyl)-2,2'-bifluorene

Hybrid organic-inorganic bis-tetrabutylammonium-7,7'-(iminundecahydro-closo-dodecaborate)-9,9'-(dihexyl)-2,2'-bifluorene (5) was prepared, and the influence of the closo-dodecaborate cluster on the two-photon absorption properties of bi-fluorene derivatives was demonstrated.     

Partition and water/oil adsorption of some surfactants

Adsorption isotherms have been determined at the water/oil interface for five biphasic systems involving surfactants (non-ionic and ionic) present in both phases at partition equilibrium. The systems studied were polyoxyethylene(23)lauryl ether (Brij35) in water/hexane and four ionic surfactants, hexadecyltrimethylammonium bromide (CTAB), and a series of three tetraalkylammonium dodecylsulfate (TEADS, TPADS, and TBADS) in water/CH 2Cl 2. Interfacial tension measurements performed at the water/air and water/oil interfaces provided all the necessary information for the determination of the adsorption parameters by taking partition into account. These measurements also allowed the comparison of the adsorption properties at both interfaces which showed an increase of the adsorption equilibrium constant and a decrease of the maximum surface concentration at the water/oil interface compared to water/air. The values of the critical aggregation concentration showed, in all cases, that only the surfactant dissolved in the aqueous phase contribute to the decrease of the water/oil interfacial tension. In the case of the four ionic surfactants, the critical aggregation concentration obtained in biphasic conditions were lowered because of the formation of mixed surfactant-CH 2Cl 2 aggregates.