Reactions of small molecules on gold single crystal surfaces

Supported heterogeneous gold catalysts (also called “real” catalysts) have been far more studied than gold single crystal surfaces. However, the surface science approach — fundamental studies of chemistry on well defined gold surfaces under controlled conditions — is extremely important, as it contributes to the understanding of the reaction mechanisms and of the nature of active centers, which allows a better knowledge of the “real” systems. This paper presents a brief overview concerning the work carried out on gold single crystal surfaces from 2004 until recently. Results on the reactions of several molecules on gold surfaces, experimental and computational (DFT) are discussed.     

NITROGEN REAGENTS IN METAL ION SEPARATION. PART VIII SUBSTITUTED IMIDAZOLES AS EXTRACTANTS FOR Cu3+

ABSTRACT

A number of derivatives of imidazole have been synthesized. Their extraction behaviour towards Cu²⁺ in dilute acid medium have been investigated in both chloride and perchlorate media. The influence of electronic and stereochemical effects are discussed. Two-phase potentiometric titrations were employed to determine the two-phase protonation constants and Cu(II) complex species present in the organic phases. The N-decylimidazole derivative has a higher extraction efficiency than the other C-ring substituted imidazoles in spite of their greater protonation constants.     

Hybrid sol gel coating: A solution to prevent interactions between plasticized poly(vinyl chloride) and injectable drugs?

During the infusion of drugs with medical devices in plasticized poly(vinyl chloride) (PVC) release of plasticizers in the injectable solution and/or sorption of drugs on PVC may occur. Thus, patient safety and/or effectiveness of his therapy may be altered. In this study, we assessed the efficiency of a sol gel hybrid coating in preventing plasticizers' release (di‐(2‐ethylhexyl) phthalate (DEHP)) from PVC matrix and drug sorption into PVC. Remaining concentrations of drugs and plasticizer's concentration released after migration tests were assessed by liquid chromatography. Migration processes were followed by Fourier Transform Infrared – Attenuated Total Reflectance (FTIR‐ATR) spectroscopy and PVC surface changes were characterized by scanning electron microscopy (SEM). An evaluation of the mechanical properties of both uncoated and coated polymer was done. The hybrid coating protects PVC from plasticizers leaching. Sorption of drugs tested is also limited. However, the protection against plasticized PVC interactions isn't optimal, probably due to a degradation of the layer, as shown on SEM microphotographs. Furthermore improvements might provide an efficient barrier to advert risks impaired to PVC interactions, to provide patient care safety. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40145.     

Modification of cellulose nanocrystals as reinforcement derivatives for wood coatings

Cellulose nanocrystal (CNC), an emerging renewable nanomaterial, was subjected to carbon chains grafting in order to improve its dispersion and its ability to transfer its rigidity properties into less polar matrixes, especially acrylic wood coatings. Chemical modifications used to this purpose are required to be simple, not affecting the CNC main structure and compatible or synergistic to oligomer reticulation inside the targeted UV-waterborne formulation. Those modifications were carried out using either alkyl quaternary ammonium bromides or acryloyl chloride. These new chemical functionalities, not inducing deep structural changes in modified CNCs, were highlighted through nuclear magnetic resonance, infrared and nitrogen content analyses. CNC derivatives were better dispersed in aqueous acrylic coating as suggested by atomic force microscopy, with a mean surface roughness falling from 9 to 6 nm on the coatings containing unmodified and treated CNCs, respectively. For mechanical evaluations, the coatings including various CNC derivatives were applied on sugar maple wood, a much appreciated material as indoor timber or wooden furniture which requires an efficient surface protection. The abrasion tests indicated that the modified CNCs confer a higher scratch resistance, with an improvement from 24% to 38% for coatings containing CNC derivatives over those with unmodified CNC.     

Microcystin ecotypes in a perennial Planktothrix agardhii bloom

The dynamics and microcystins (MC) concentrations of a perennial Planktothrix agardhii bloom were investigated in a eutrophic lake (Viry-Chatillon, France). A weak relationship was observed between P. agardhii population biomass and the MC concentrations in a 1-year survey. To further investigate the causes of MC concentration changes, we concurrently conducted experiments on 41 strains isolated from this lake. We first checked the clonal diversity of P. agardhii population (i) by molecular techniques, to assess the presence of MC synthetase gene (mcyB), (ii) by biochemical assay (PP2A inhibition assay), for MC production, and (iii) by mass spectrometry (MS), to identify the MC chemotypes. Our results illustrated the diversity of genotype and MC chemotypes within a P. agardhii natural population. Eleven chemotypes among the 16 possible ones were found by MS. Furthermore, we noticed major differences in the MC content of isolated strains (from 0.02 to 1.86 microg equiv. MC-LR mg DW(-1), n=25). Growth and MC production of one MC-producing strain and one non-MC-producing strain were also assessed at two temperatures (10 and 20 degrees C). We showed that growth capacities of these strains were similar at the two tested temperatures, and that the MC production rate was correlated to the growth rate for the MC-producing strain. On the basis of these results, several hypotheses are discussed to explain the weakness of relationships between natural P. agardhii biomass and MC concentration. One of the main reasons could lie in the proportion of MC-producing clones and non-MC-producing clones that may change during the sampling period. Also, the MC-producing clones may present different intracellular MC content due to (i) MC chemotypes diversity, (ii) changes in MC variants proportions within a strain, and (iii) changes in MC rate production depending on the physiological state of cells. Finally, we concluded that various biological organization levels have to be considered (population, cellular and molecular), through an integrative approach, in order to provide a better understanding of P. agardhii in situ MC production.