Boucle J.,University of Limoges |
Ackermann J.,CNRS Interdisciplinary Nanoscience Centre of Marseille
Polymer International | Year: 2012
In the field of photovoltaic energy conversion, hybrid inorganic/organic devices represent promising alternatives to standard photovoltaic systems in terms of exploiting the specific features of both organic semiconductors and inorganic nanomaterials. Two main categories of hybrid solar cells coexist today, both of which make much use of metal oxide nanostructures based on titanium dioxide (TiO 2) and zinc oxide (ZnO) as electron transporters. These metal oxides are cheap to synthesise, are non-toxic, are biocompatible and have suitable charge transport properties, all these features being necessary to demonstrate highly efficient solar cells at low cost. Historically, the first hybrid approach developed was the dye-sensitized solar cell (DSSC) concept based on a nanostructured porous metal oxide electrode sensitized by a molecular dye. In particular, solid-state hybrid DSSCs, which reduce the complexity of cell assembly, demonstrate very promising performance today. The second hybrid approach exploits the bulk heterojunction (BHJ) concept, where conjugated polymer/metal oxide interfaces are used to generate photocurrent. In this context, we review the recent progress and new concepts in the field of hybrid solid-state DSSC and BHJ solar cells based on TiO 2 and ZnO nanostructures, incorporating dyes and conjugated polymers. We point out the specificities in common hybrid device structures and give an overview on new concepts, which couple and exploit the main advantages of both DSSC and BHJ approaches. In particular, we show that there is a trend of convergence between both DSSC and BHJ approaches into mixed concepts at the borderline which may allow in the near future the development of hybrid devices for competitive photovoltaic energy conversion. © 2011 Society of Chemical Industry.
Pieper H.H.,University of Osnabrück |
Barth C.,CNRS Interdisciplinary Nanoscience Centre of Marseille |
Reichling M.,University of Osnabrück
Applied Physics Letters | Year: 2012
The structure and polarity of step edges on cleaved CaF 2(111) are investigated by non-contact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy. Ledges produced by cleaving the crystal appear with two distinctly different polarities denoted as type I and type II arising from the sectioning of ledges with steps having different polarities. With respect to the stoichiometric terrace, the surface potential is slightly reduced at ledges predominately composed of type I steps, while the potential of ledges predominantly composed of type II steps is significantly higher (typically 100 mV). We propose that the positive potential of type II steps stems from low coordinated Ca 2 ions inducing a dipole at step edges and confirm this by atomically resolved NC-AFM images revealing the Ca 2 ion sub-lattice with repulsive-mode imaging contrast. © 2012 American Institute of Physics.
Weissker H.-Ch.,CNRS Interdisciplinary Nanoscience Centre of Marseille |
Weissker H.-Ch.,European Theoretical Spectroscopy Facility |
Mottet C.,CNRS Interdisciplinary Nanoscience Centre of Marseille
Physical Review B - Condensed Matter and Materials Physics | Year: 2011
Pseudopotential time-dependent density-functional theory (TDDFT) calculations are carried out to investigate the optical absorption spectra of magic-number noble-metal nanoparticles of 13, 38, 55, 140, and 147 atoms. In particular, we study the differences between isomeric structures such as Ag 13 in both cubic and icosahedral structures. Differences are well visible up to sizes of about 55 atoms, demonstrating the need for proper treatment of the structural details on the atomic level. For the largest sizes of about 150 atoms, our calculations confirm earlier results of TDDFT using a structureless jellium model. In particular, we recover the surface plasmon resonance for silver nanoclusters. The bimetallic Ag32Au6 core-shell cluster displays an intense peak corresponding to the surface-plasmon resonance in the Ag cluster, but the spectrum does not lie between the spectra of the pure Ag38 and Au38 clusters. By contrast, a copper core in a Ag38Cu6 cluster leads to a strong damping of this peak. © 2011 American Physical Society.
Norman L.,University of Maryland University College |
Sengupta K.,CNRS Interdisciplinary Nanoscience Centre of Marseille |
Aranda-Espinoza Helim H.,University of Maryland University College
European Journal of Cell Biology | Year: 2011
Cell spreading is a critical component of numerous physiological phenomena including cancer metastasis, embryonic development, and mitosis. We have previously illustrated that cellular blebs appear after abrupt cell-substrate detachment and play a critical role in regulating membrane tension; however, the dynamics of bleb-substrate interactions during spreading remains unclear. Here we explore the role of blebs during endothelial cell spreading using chemical and osmotic modifications to either induce or inhibit bleb formation. We track cell-substrate dynamics as well as individual blebs using surface sensitive microscopic techniques. Blebbing cells (both control and chemically induced) exhibit increased lag times prior to fast growth. Interestingly, lamellae appear later for blebbing compared to non-blebbing cells, and in all cases, lamellae signal the start of fast spreading. Our results indicate that cellular blebs play a key role in the early stage of cell spreading, first by controling the initial cell adhesion and then by presenting a dynamic inhibition of cell spreading until a lamella appears and fast spreading ensues. © 2010 Elsevier GmbH.
D'Aleo A.,CNRS Interdisciplinary Nanoscience Centre of Marseille |
Pointillart F.,CNRS Chemistry Institute of Rennes |
Ouahab L.,CNRS Chemistry Institute of Rennes |
Andraud C.,CNRS Chemistry Laboratory |
Maury O.,CNRS Chemistry Laboratory
Coordination Chemistry Reviews | Year: 2012
Since the pioneering studies of Weissman in the 1940s, the sensitization of lanthanide luminescence via the antenna effect is becoming extremely classical. The photophysical sensitization process generally involves an energy transfer from the triplet excited state of an organic or a transition metal containing an antenna chromophore. Recently, the direct lanthanide sensitization from charge transfer excited state appears as an alternative process resulting in a red-shift of the excitation wavelength far in the visible thanks to the design of ligands with appropriate donor-acceptor charge transfer transitions. This review presents the research endeavor in this area and underlines related applications in nonlinear optics. © 2012 Elsevier B.V.
Saul A.,CNRS Interdisciplinary Nanoscience Centre of Marseille |
Radtke G.,CNRS Institute Materials Microelectronics nanosciences of Provence
Physical Review Letters | Year: 2011
Concerning its magnetic properties, the layered vanadate CsV 2O5 has long been considered as formed by isolated spin-1/2 dimers characterized by a large antiferromagnetic coupling of about 146K. This interpretation was supported by both magnetic susceptibility measurements and the obvious presence of magnetically active strongly dimerized V4+ ions. In this work we investigate the magnetic properties of this compound through an extensive use of the broken-symmetry formalism in the framework of density-functional theory. Our calculations demonstrate that the system is built from strongly dimerized alternating chains where the structural and magnetic dimers are distinct from each other. © 2011 American Physical Society.
De Padova P.,National Research Council Italy |
Quaresima C.,National Research Council Italy |
Olivieri B.,National Research Council Italy |
Perfetti P.,National Research Council Italy |
Le Lay G.,CNRS Interdisciplinary Nanoscience Centre of Marseille
Applied Physics Letters | Year: 2011
Silicene nanoribbons grown on a silver (110) substrate have been studied by reflection electron energy loss spectroscopy as a function of the electron beam incidence angle α. The spectra, taken at the Si K absorption edge (1.840 keV), reveal the presence of two distinct loss structures attributed to transitions 1s→ π and 1s→ σ, according to their intensity dependence on α. Such behavior, when compared to graphite, attests the s p2 -like hybridization of the silicon valence orbitals in the silicene nanoribbons as is, indeed, for carbon atomic bonds of graphene. © 2011 American Institute of Physics.
Lamanna C.M.,Boston University |
Lusic H.,Boston University |
Camplo M.,CNRS Interdisciplinary Nanoscience Centre of Marseille |
McIntosh T.J.,Duke University |
And 3 more authors.
Accounts of Chemical Research | Year: 2012
Twenty years after gene therapy was introduced in the clinic, advances in the technique continue to garner headlines as successes pique the interest of clinicians, researchers, and the public. Gene therapys appeal stems from its potential to revolutionize modern medical therapeutics by offering solutions to myriad diseases through treatments tailored to a specific individuals genetic code. Both viral and non-viral vectors have been used in the clinic, but the low transfection efficiencies when non-viral vectors are used have lead to an increased focus on engineering new gene delivery vectors. To address the challenges facing non-viral or synthetic vectors, specifically lipid-based carriers, we have focused on three main themes throughout our research: (1) The release of the nucleic acid from the carrier will increase gene transfection. (2) The use of biologically inspired designs, such as DNA binding proteins, to create lipids with peptide-based headgroups will improve delivery. (3) Mimicking the natural binding patterns observed within DNA, by using lipids having a nucleoside headgroup, will produce unique supramolecular assembles with high transfection efficiencies. The results presented in this Account demonstrate that engineering the chemical components of the lipid vectors to enhance nucleic acid binding and release kinetics can improve the cellular uptake and transfection efficacy of nucleic acids. Specifically, our research has shown that the incorporation of a charge-reversal moiety to initiate a shift of the lipid from positive to negative net charge improves transfection. In addition, by varying the composition of the spacer (rigid, flexible, short, long, or aromatic) between the cationic headgroup and the hydrophobic chains, we can tailor lipids to interact with different nucleic acids (DNA, RNA, siRNA) and accordingly affect delivery, uptake outcomes, and transfection efficiency. The introduction of a peptide headgroup into the lipid provides a mechanism to affect the binding of the lipid to the nucleic acid, to influence the supramolecular lipoplex structure, and to enhance gene transfection activity. Lastly, we discuss the in vitro successes that we have had when using lipids possessing a nucleoside headgroup to create unique self-assembled structures and to deliver DNA to cells. In this Account, we state our hypotheses and design elements as well as describe the techniques that we have used in our research to provide readers with the tools to characterize and engineer new vectors. © 2012 American Chemical Society.
Kern R.,CNRS Interdisciplinary Nanoscience Centre of Marseille
Crystal Research and Technology | Year: 2013
An all-inclusive review is proposed on the adsorption-absorption phenomena concerning both equilibrium and growth of crystals. The logical path starts with the relations between the adsorption and growth of pure crystals, continues with the change of the crystal shape due to the surface adsorption of foreign substances (without absorption in the crystal bulk) and terminates with the absorption and crystal growth. Historical aspects are widely illustrated along with the fascinating alternation of observations, experimental efforts and theoretical knowledge. An all-inclusive review is proposed on the adsorption-absorption phenomena concerning both equilibrium and growth of crystals. The logical path starts with the relations between the adsorption and growth of pure crystals, continues with the change of the crystal shape due to the surface adsorption of foreign substances (without absorption in the crystal bulk) and terminates with the absorption and crystal growth. Historical aspects are widely illustrated along with the fascinating alternation of observations, experimental efforts and theoretical knowledge. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Xia Y.,CNRS Interdisciplinary Nanoscience Centre of Marseille |
Peng L.,CNRS Interdisciplinary Nanoscience Centre of Marseille
Chemical Reviews | Year: 2013
The article presents photoactivatable lipid probes for studying biomembranes by photo affinity labeling. The lipid probes bear photoactivatable chromophores either at the polar head or within the hydrophobic part, and are able to incorporate into the lipid bilayer. When exposed to light, they generate highly reactive species allowing their covalent cross-linkage with membrane proteins or surrounding lipids. Photoactivatable lipid probes are mainly used for studying biological membranes, and it is believed that the hydrophobic interior of biomembranes provides far more favorable medium for photolabeling than an aqueous medium. Indeed, the relative chemical inertness of the phospholipid bilayer can increase the lifetime of the reactive species and ensure their chance of attacking membrane proteins successfully, notwithstanding the exact impact of apolar core on the individual photoreaction.