Time filter

Source Type

Barbieri A.,CNR Institute for Organic Syntheses and Photoreactivity | Ventura B.,CNR Institute for Organic Syntheses and Photoreactivity | Ziessel R.,CNRS The Institute of Chemistry and Processes for Energy, Environment and Health
Coordination Chemistry Reviews | Year: 2012

Transfer of excitation energy in natural systems is a fundamental process for light harvesting and propagation of information. The deep understanding of the energy transfer mechanisms and of the strategies for governing the directionality of the energy flow in artificial multichromophoric arrays is at the basis of their use in demanding fields such as solar energy conversion and optoelectronic applications. This review describes the recent activity of the authors in the synthesis and photophysical characterization of supramolecular arrays containing transition metal polypyridine complexes and organic units, with attention on the mechanisms and the pathways of the energy transfer processes that occur in the arrays. A topic of interest has been the exploitation of antenna effects as well as energy conduction in molecular wires. The design of the systems took into consideration several aspects that need to be balanced in the construction of efficient and useful arrays, in particular the spatial displacement of the units, their energy content distribution and the nature of the linkers that connect them. The latter point was of great relevance and the most recent studies afforded the preparation and the analysis of systems where the ligand is a large aromatic unit, that can both provide a structural role, a suitable electronic communication between the chromophores and an additional photoactive partnership. © 2012 Elsevier B.V. Source

Imfeld G.,CNRS The Institute of Chemistry and Processes for Energy, Environment and Health | Vuilleumier S.,University of Strasbourg
European Journal of Soil Biology | Year: 2012

Extensive application of industrially-produced pesticides in agriculture has resulted in contamination of soil ecosystems. A variety of both cultivation-dependent and cultivation-independent methods can be applied to measure and interpret the effects of pesticide exposure. We review here the expanding panel of these methods in the specific context of responses of the soil bacterial microflora to pesticide exposure, and of ongoing advances in microbial molecular ecology, including metagenomics and new approaches for DNA sequencing. Several issues still need to be addressed in order to routinely evaluate the effect of pesticides on bacterial communities in soil in the future, and to make way for a widely accepted framework for risk assessment in agro-ecosystems that include bacterial indicators. © 2011 Elsevier Masson SAS. Source

Rodriguez-Manzo J.A.,CNRS Institute of Genetics and of Molecular and Cellular Biology | Pham-Huu C.,CNRS The Institute of Chemistry and Processes for Energy, Environment and Health | Banhart F.,CNRS Institute of Genetics and of Molecular and Cellular Biology
ACS Nano | Year: 2011

Single and few-layer graphene is grown by a solid-state transformation of amorphous carbon on a catalytically active metal. The process is carried out and monitored in situ in an electron microscope. It is observed that an amorphous carbon film is taken up by Fe, Co, or Ni crystals at temperatures above 600 °C. The nucleation and growth of graphene layers on the metal surfaces happen after the amorphous carbon film has been dissolved. It is shown that the transformation of the energetically less favorable amorphous carbon to the more favorable phase of graphene occurs by diffusion of carbon atoms through the catalytically active metal. © 2011 American Chemical Society. Source

Iehl J.,CNRS Molecular Chemistry Laboratory | Nierengarten J.-F.,CNRS Molecular Chemistry Laboratory | Harriman A.,Northumbria University | Bura T.,CNRS The Institute of Chemistry and Processes for Energy, Environment and Health | Ziessel R.,CNRS The Institute of Chemistry and Processes for Energy, Environment and Health
Journal of the American Chemical Society | Year: 2012

A sophisticated model of the natural light-harvesting antenna has been devised by decorating a C 60 hexa-adduct with ten yellow and two blue boron dipyrromethene (Bodipy) dyes in such a way that the dyes retain their individuality and assist solubility of the fullerene. Unusually, the fullerene core is a poor electron acceptor and does not enter into light-induced electron-transfer reactions with the appended dyes, but ineffective electronic energy transfer from the excited-state dye to the C 60 residue competes with fluorescence from the yellow dye. Intraparticle electronic energy transfer from yellow to blue dyes can be followed by steady-state and time-resolved fluorescence spectroscopy and by excitation spectra for isolated C 60 nanoparticles dissolved in dioxane at 293 K and at 77 K. The decorated particles can be loaded into polymer films by spin coating from solution. In the dried film, efficient energy transfer occurs such that photons absorbed by the yellow dye are emitted by the blue dye. Films can also be prepared to contain C 60 nanoparticles loaded with the yellow Bodipy dye but lacking the blue dye and, under these circumstances, electronic energy migration occurs between yellow dyes appended to the same nanoparticle and, at higher loading, to dye molecules on nearby particles. Doping these latter polymer films with the mixed-dye nanoparticle coalesces these multifarious processes in a single system. Thus, long-range energy migration occurs among yellow dyes attached to different particles before trapping at a blue dye. In this respect, the film resembles the natural photosynthetic light-harvesting complexes, albeit at much reduced efficacy. The decorated nanoparticles sensitize amorphous silicon photocells. © 2011 American Chemical Society. Source

Bura T.,CNRS The Institute of Chemistry and Processes for Energy, Environment and Health | Ziessel R.,CNRS The Institute of Chemistry and Processes for Energy, Environment and Health
Organic Letters | Year: 2011

Water-soluble BODIPY dyes have been readily obtained by introduction of phosphonate fragments either on the boron for the green and yellow emitting dyes or on the side chain for the red emitting dyes. Hydrolysis of the phosphonate is realized at the end of the reaction sequence and allows isolation of the targets by precipitation. All these novel dyes are soluble and fluorescent in water with quantum yields in the 23-59% range and emission wavelength spanning from 667 to 509 nm. © 2011 American Chemical Society. Source

Discover hidden collaborations