Electrochemically Generated Nanoparticles of Halogen‐Bridged Mixed‐Valence Binuclear Metal Complex Chains

Spherical nanoparticles composed of MMX chains can be made by a polymerization strategy driven by electrochemical processes. In particular, the [Pt₂(MeCS₂)₄I₂] (MMI₂) dimetal subunit is employed as a monomer for the formation of [Pt₂(MeCS₂)₄I]_n spherical nanostructures on surfaces. We have paid particular attention to elucidating the general mechanism of the deposition process on the basis of in situ electrochemical measurements. The reduction of MMI₂ to give the electrodeposition of nanostructures agrees well with formation of the reduced [MMI₂]^? species followed by a disproportionation mechanism mediated by iodide anions. The chemical composition of the particles was determined by energy‐dispersive X‐ray spectroscopy (EDX) and X‐ray photoelectron spectroscopy (XPS) to reveal the MMI₂ polymer.     

Structure and Dynamics of Oligonucleotides in the Gas Phase

By combining ion‐mobility mass spectrometry experiments with sub‐millisecond classical and ab initio molecular dynamics we fully characterized, for the first time, the dynamic ensemble of a model nucleic acid in the gas phase under electrospray ionization conditions. The studied oligonucleotide unfolds upon vaporization, loses memory of the solution structure, and explores true gas‐phase conformational space. Contrary to our original expectations, the oligonucleotide shows very rich dynamics in three different timescales (multi‐picosecond, nanosecond, and sub‐millisecond). The shorter timescale dynamics has a quantum mechanical nature and leads to changes in the covalent structure, whereas the other two are of classical origin. Overall, this study suggests that a re‐evaluation on our view of the physics of nucleic acids upon vaporization is needed.     

Spectroscopies and Electron Microscopies Unravel the Origin of the First Colour Photographs

The first colour photographs were created by a process introduced by Edmond Becquerel in 1848. The nature of these photochromatic images colours motivated a debate between scientists during the XIX^th century, which is still not settled. We present the results of chemical analysis (EDX, HAXPES and EXAFS) and morphology studies (SEM, STEM) aiming at explaining the optical properties of the photochromatic images (UV‐visible spectroscopy and low loss EELS). We rule out the two hypotheses (pigment and interferences) that have prevailed since 1848, respectively based on variations in the oxidation degree of the compound forming the sensitized layer and periodically spaced photolytic silver planes. A study of the silver nanoparticles dispersions contained in the coloured layers showed specific localizations and sizes distributions of the nanoparticles for each colour. These results allow us to formulate a plasmonic hypothesis on the origin of the photochromatic images colours.     

Modification of Cross-Linked Rubber Particles by Free Radical Polymerization

The synthesis of polystyrene chains covalently bound to the surface of cross-linked rubber particles from recycled tires (ground tire rubber, GTR) was investigated via free radical polymerization in situ by using azobisisobutyronitrile (AIBN) and dibenzoyl peroxide (BPO) as initiators. Indeed, the graft polymerization provides a significant route to modify the physical and chemical properties of these particles allowing to improve their compatibility with other polymers. Polymerization reactions were carried out in bulk by changing the styrene/GTR ratio as well as the amount of free radical initiator. Appreciable amounts of polystyrene (PS) were grafted on GTR when BPO was used as confirmed by particle characterizations.     

The continuous-flow cycloaddition of azomethine ylides to carbon nanotubes

This communication demonstrates a straightforward continuous-flow method for efficient exohedral functionalisation of carbon nanotubes which affords soluble samples in a much shorter time over conventional batch processing.     

DMT-MM mediated functionalisation of the non-reducing end of glycosaminoglycans

Efficient functionalisation of the non-reducing end of uronic acid derivatives and glycosaminoglycan-derived disaccharides using peptide coupling has been achieved, mediated by the water-soluble agent DMT-MM.     

Adapting the semi-explicit assembly solvation model for estimating water-cyclohexane partitioning with the SAMPL5 molecules

We describe here some tests we made in the SAMPL5 communal event of ‘Semi-Explicit Assembly’ (SEA), a recent method for computing solvation free energies. We combined the prospective tests of SAMPL5 with followup retrospective calculations, to improve two technical aspects of the field variant of SEA. First, SEA uses an approximate analytical surface around the solute on which a water potential is computed. We have improved and simplified the mathematical model of that surface. Second, some of the solutes in SAMPL5 were large enough to need a way to treat solvating waters interacting with ‘buried atoms’, i.e. interior atoms of the solute. We improved SEA with a buried-atom correction. We also compare SEA to Thermodynamic Integration molecular dynamics simulations, so that we can sort out force field errors.     

Changes in the reactivity of the fluorescent reagents carbazole-9-carbonyl chloride and 9-carbazolylacetic acid in the presence of cyclodextrins

Carbazole-9-carbonyl chloride (C9CC) and 9-carbazolylacetic acid (9CAA) were selected as model fluorescent reagents. The effect of different chemically modified cyclodextrins (CDs) added to the aqueous solutions of these reagents was studied in water and in buffered aqueous solutions at pH 4.5 and 8.8. The CDs employed were 2-hydroxypropyl-β-cyclodextrin (HP-βCD), 2,3-di-O-methyl-β-cyclodextrin (DM-βCD) and 2,3,6-tri-O-methyl-β-cyclodextrin (TM-βCD). The inclusion of these reagents inside the cavities of the CDs was verified and this process can affect the derivatization reaction because CDs can modify the reactivity of the guest molecules. The basic conditions necessary for the derivatization reaction between C9CC and amines lead to the formation of carbazole anion through hydrolysis followed by decarboxylation. In the presence of CDs, the hydrolysis-decarboxylation of carbazole-9-carbonyl chloride is faster than in buffered aqueous homogeneous solutions. The behaviour observed for these reagents in aqueous solutions of CDs was compared to the one observed in basic ethanolic solutions. These changes are particularly noticeable in the case of 2,3-di-O-methyl-β-CD and 2-hydroxypropyl-β-CD. The characteristics of the fluorescent reagents are compared to carbazole and 9-methylcarbazole as model compounds. This paper was presented at XIIIth International Cyclodextrin Symposium. Torino, Italy, May 14–17, 2006.