Publications

2012

• Mechanical properties of suspended few layers graphene sheets
  
  • Sridi Nawres
  • Lebental Bérengère
  • Merliot Érick
  • Cojocaru Costel Sorin
  • Azevedo J.
  • Benattar J.J.
  • Nowodzinski A.
  • Gabriel Aurélie
  • Ghis Anne
  Technical Proceedings of the 2012 NSTI Nanotechnology Conference and Expo, 2012, pp.147-149. We present a method for the experimental determination of the mechanical properties of ultrathin films, whichever the material, and a comparative application to graphene sheets obtained with different fabrication and transfer processes
• Mechanical properties of suspended few layers graphene sheets
  
  • Sridi Nawres
  • Lebental Bérengère
  • Merliot Erick
  • Cojocaru Costel-Sorin
  • Azevedo Joel
  • Nowodzinski Antoine
  • Gabriel Jean Christophe
  • Ghis Anne
  , 2012, pp.4p. In this paper, we present first a fabrication process of suspended graphene stripes. This process is done on two types of graphene sheets. One is a reduced graphene oxide and the second is a few layer graphene grown by CVD. In the second part, we introduce a new method to derive the value of the local Young’s modulus of ultrathin films using atomic force microscopy for experimental measurements and a continuum mechanics model for analytical fitting. Measurements are performed on few nanometers thick suspended graphene sheets grown by CVD.
• Laser heating versus phonon confinement effect in the Raman spectra of diamond nanoparticles
  
  • Chaigneau Marc
  • Picardi Gennaro
  • Girard Hugues
  • Arnault Jean-Charles
  • Ossikovski Razvigor
  Journal of Nanoparticle Research, Springer Verlag, 2012, 14, pp.955. Nanodiamond particles with typical diameters of 20 and 6 nm produced by high pressure high temperature or detonation processes have been studied by micro-Raman spectroscopy. We show that the frequency downshift and broadening of the first-order diamond phonon band is not uniquely related to phonon confinement, as commonly assumed. Local heating caused by the focused laser light must be also taken in account, since it may affect the Raman spectrum in a similar fashion, even at relatively low laser power levels. A combined theoretical model considering both effects (quantum confinement and local heating) on the excited phonon modes is presented and adopted for the simulation of the experimental data. We observe different heating behaviours upon laser illumination depending on the particles origin, thus underscoring the importance to compensate for this effect before retrieving structural parameters. (10.1007/s11051-012-0955-9)
  DOI : 10.1007/s11051-012-0955-9
• Structural and Functional Characteristics of Chimeric Avidins Physically Adsorbed onto Functionalized Polythiophene Thin Films
  
  • Albers Willem M
  • Pelto Jani M
  • Suspène Clément
  • Määttä Juha A
  • Yassar Abderrahim
  • Hytönen Vesa P
  • Vikholm-Lundin Inger M
  • Tappura Kirsi
  ACS Applied Materials & Interfaces, Washington, D.C. : American Chemical Society, 2012, 4 (8), pp.4067-4077. Stabilized bioreceptor layers are of great importance in the design of novel biosensors. In earlier work, chimeric avidins enabled immobilization of biotinylated antibodies onto gold surfaces with greater stability compared to more conventional avidins (wild-type avidin and streptavidin). In the present study, the applicability of chimeric avidins as a general binding scaffold for biotinylated antibodies on spin-coated functionalized polythiophene thin films has been studied by surface plasmon resonance and atomic force microscopy. Novel chimeric avidins showed remarkably increased binding characteristics compared with other avidins, such as wild-type avidin, streptavidin, and bacterial avidin when merely physically adsorbed onto the polythiophene surface. They gave the highest binding capacities, the highest affinity constant, and the highest stability for biotinylated probe immobilization. Introduction of carboxylic acid groups to polythiophene layer further enhanced the binding level of the avidins. Polythiophene layers functionalized with chimeric avidins thus offered a promising generic platform for biosensor applications. (10.1021/am3008517)
  DOI : 10.1021/am3008517
• Graphene-based resistive humidity sensor for in-situ monitoring of drying shrinkage and intrinsic permeability in concrete
  
  • Lebental Bérengère
  • Moujahid Waleed
  • Lee Chang-Soek
  • Maurice Jean Luc
  • Cojocaru Costel-Sorin
  , 2012, pp.8p. Nanosensors dedicated to the structural health monitoring of concrete structures have been only marginally studied. They would however be particularly well-suited to monitor durability-related processes, as these phenomena involve transport of gas and liquids through micro and nano-porosity. In this paper we discuss the relevance and feasibility of embedding rela-tive humidity nanosensors within concrete. It appears that the localized, continuous knowledge of relative humidity within a concrete structure could provide a useful insight into drying shrinkage; it could also contribute to improved intrinsic permeability measurements, leading to improved assessment of structural durability. For the task, we propose a low-cost, downscalable resistive device made of a 10 nm graphene sheet grown directly on glass and atop which are ink-jet printed silver electrodes. The device resistance increases significantly with relative humidity (RH), especially above 40% RH. Relative amplitude of variations are only of about 3% for the two tested devices, but absolute variations (80 Ohms/sq and 480 Ohms/sq) appear measurable by a low-cost and robust signal conditioning electronics. Thus, the idea of using our graphene-based resistive device for embedded humidity monitoring in concrete ap-pears quite promising.
• High-Rate Capability Silicon Decorated Vertically Aligned Carbon Nanotubes for Li-Ion Batteries
  
  • Gohier Aurelien
  • Laik Barbara
  • Kim Ki Hwan
  • Maurice Jean Luc
  • Pereira-Ramos Jean Pierre
  • Cojocaru Costel Sorin
  • Van Pierre Tran
  Advanced Materials, Wiley-VCH Verlag, 2012, 24 (19), pp.2592-2597. The concept of a hybrid nanostructured collector made of thin vertically aligned carbon nanotubes (CNTs) decorated with Si nanoparticles provides high power density anodes in lithium-ion batteries. An impressive rate capability is achieved due to the efficient electronic conduction of CNTs combined with well defined electroactive Si nanoparticles: capacities of 3000 mAh g−1 at 1.3C and 800 mAh g−1 at 15C are achieved. (10.1002/adma.201104923)
  DOI : 10.1002/adma.201104923
• Thin graphene layers (TGL) by carbon implantation into nickel films and thermal diffusion towards surface
  
  • Le Normand F.
  • Lee C.S.
  • Maurice J.L.
  • Cojocaru C.S.
  • Châtelet Marc
  • Chaigneau M.
  • Muller D.
  • Speisser C.
  , 2012.
• Radial junction amorphous silicon solar cells on PECVD-grown silicon nanowires
  
  • Yu Linwei
  • O'Donnell Benedict
  • Foldyna Martin
  • Cabarrocas Pere Roca I.
  Nanotechnology, Institute of Physics, 2012, 23, pp.4011. Constructing radial junction hydrogenated amorphous silicon (a-Si:H) solar cells on top of silicon nanowires (SiNWs) represents a promising approach towards high performance and cost-effective thin film photovoltaics. We here develop an all-in situ strategy to grow SiNWs, via a vapour-liquid-solid (VLS) mechanism on top of ZnO-coated glass substrate, in a plasma-enhanced chemical vapour deposition (PECVD) reactor. Controlling the distribution of indium catalyst drops allows us to tailor the as-grown SiNW arrays into suitable size and density, which in turn results in both a sufficient light trapping effect and a suitable arrangement allowing for conformal coverage of SiNWs by subsequent a-Si:H layers. We then demonstrate the fabrication of radial junction solar cells and carry on a parametric study designed to shed light on the absorption and quantum efficiency response, as functions of the intrinsic a-Si:H layer thickness and the density of SiNWs. These results lay a solid foundation for future structural optimization and performance ramp-up of the radial junction thin film a-Si:H photovoltaics. (10.1088/0957-4484/23/19/194011)
  DOI : 10.1088/0957-4484/23/19/194011
• Charge Transfer and Tunable Ambipolar Effect Induced by Assembly of Cu(II) Binuclear Complexes on Carbon Nanotube Field Effect Transistor Devices
  
  • Magadur Gurvan
  • Lauret Jean-Sébastien
  • Charron Gaëlle
  • Bouanis Fatima
  • Norman Evgeny
  • Huc Vincent
  • Cojocaru Costel-Sorin
  • Gómez-Coca Silvia
  • Ruiz Eliseo
  • Mallah Talal
  Journal of the American Chemical Society, American Chemical Society, 2012, 134 (18), pp.7896-7901. (10.1021/ja301362r)
  DOI : 10.1021/ja301362r
• Diffusion Mechanism of Lithium Ion through Basal Plane of Layered Graphene
  
  • Yao Fei
  • Gunes Fethullah
  • Ta Hui Quang
  • Lee Seung Mi
  • Chae Seung Jin
  • Sheem Kyeu Yoon
  • Cojocaru Costel Sorin
  • Xie Si Shen
  • Lee Young Hee
  Journal of the American Chemical Society, American Chemical Society, 2012, 134 (20), pp.8646--8654. Coexistence of both edge plane and basal plane in graphite often hinders the understanding of lithium ion diffusion mechanism. In this report, two types of graphene samples were prepared by chemical vapor deposition (CVD): (i) well-defined basal plane graphene grown on Cu foil and (ii) edge plane-enriched graphene layers grown on Ni film. Electrochemical performance of the graphene electrode can be split into two regimes depending on the number of graphene layers: (i) the corrosion-dominant regime and (ii) the lithiation-dominant regime. Li ion diffusion perpendicular to the basal plane of graphene is facilitated by defects, whereas diffusion parallel to the plane is limited by the steric hindrance that originates from aggregated Li ions adsorbed on the abundant defect sites. The critical layer thickness (lc) to effectively prohibit substrate reaction using CVD-grown graphene layers was predicted to be ∼6 layers, independent of defect population. Our density functional theory calculations demonstrate that divacancies and higher order defects have reasonable diffusion barrier heights allowing lithium diffusion through the basal plane but neither monovacancies nor Stone-Wales defect. (10.1021/ja301586m)
  DOI : 10.1021/ja301586m
• Charge Transfer and Tunable Ambipolar Effect Induced by Assembly of Cu (II) Binuclear Complexes on Carbon Nanotube Field Effect Transistor Devices
  
  • Magadur Gurvan
  • Lauret Jean‐sébastien
  • Charron Gaëlle
  • Bouanis Fatima
  • Norman Evgeny
  • Huc Vincent
  • Cojocaru Costel Sorin
  • Goìmez-Coca S.
  • Ruiz E.
  • Mallah Talal
  Journal of the American Chemical Society, American Chemical Society, 2012, 134 (18), pp.7896--7901. Assembly of paramagnetic Cu2 complexes with a Schiff base scaffold possessing extended electron delocalization together with a quasi-planar structure onto carbon nanotubes induces a diameter-selective charge transfer from the complex to the nanotubes leading to an interestingly large and tunable ambipolar effect. We used complementary techniques such as electron paramagnetic resonance, absorption spectroscopy, and photoluminescence to ensure the success of the assembly process and the integrity of the complex in the nanohybrid. We carried out density functional theory type calculations to rationalize the experimental results,evidencing the selective enhanced interaction of the metal complexes with one type of nanotube. (10.1021/ja301362r)
  DOI : 10.1021/ja301362r
• Carbon nanotubes and graphene-based microsonar for embedded monitoring of microporosity
  
  • Lebental Bérengère
  • Sridi Nawres
  • Bouanis Fatima
  • Cojocaru Costel-Sorin
  • Bourquin Frédéric
  • Ghis Anne
  , 2012, pp.18p. Nanoporosities play a most significant role in the durability of cementitious materials, so that nanoscale features are a promising target for SHM. However, to this day, no sensor features the resolution required to investigate non-destructively these nanofeatures. To fill in this loophole, we are devising a SHM-targeted, carbon nanotubes and graphene based capacitive ultrasonic nanotransducer for microporosity assessment in concrete. In this paper, we report on the feasibility of the key building block of the proposed sensor: we have fabricated ultra-thin graphene and single-walled carbon nanotubes membranes. A breakthrough laser vibrometry experiment shows that the membranes can feature above-nanometer amplitudes of vibration over a large range of frequencies spanning from 100 kHz to 5 MHz. A detailed numerical model of the nanotransducer shows that upon embedding in a cementitious material it could determine the volume and content of the porosity in its vicinity. Such information would be invaluable in the evaluation of structural durability.
• Effect of speckle on APSCI method and Mueller Imaging
  
  • Upadhyay Debajyoti
  • Richert Michael
  • Lacot Eric
  • de Martino Antonello
  • Orlik Xavier
  Optics Express, Optical Society of America - OSA Publishing, 2012, 19 (5), pp.4553-4559. The principle of the polarimetric imaging method called APSCI (Adapted Polarization State Contrast Imaging) is to maximize the polarimetric contrast between an object and its background using specific polarization states of illumination and detection. We perform here a comparative study of the APSCI method with existing Classical Mueller Imaging(CMI) associated with polar decomposition in the presence of fully and partially polarized circular Gaussian speckle. The results show a noticeable increase of the Bhattacharyya distance used as our contrast parameter for the APSCI method, especially when the object and background exhibit several polarimetric properties simultaneously. (10.1364/OE.19.004553)
  DOI : 10.1364/OE.19.004553
• Persistent photoexcitation effect on the poly(3-hexylthiophene) film: Impedance measurement and modeling
  
  • Kim Chang Hyun
  • Kisiel Krzysztof
  • Jung Jaroslaw
  • Ulanski Jacek
  • Tondelier Denis
  • Geffroy Bernard
  • Bonnassieux Yvan
  • Horowitz Gilles
  Synthetic Metals, Elsevier, 2012, 162, pp.460. We report on the equivalent circuit modeling of the relaxation behavior of an optically excited thick poly(3-hexylthiophene) (P3HT) film by means of impedance spectroscopy. Fabricated metal-semiconductor-metal devices with Au electrodes showed a nearly perfect ohmic behavior under ambient conditions. Impedance measurements on illuminated P3HT device showed a dramatical decrease of the impedance modulus under illumination and very slow relaxation to the initial state. Impedance-frequency data obtained during relaxation could not be explained by a simple parallel resistance-capacitance circuit but it could be best fitted by incorporating a constant-phase element instead of a normal capacitance. By observing the variation of the circuit parameters, it is found that the relaxation process is dominated by slow recombination (elimination) of the excess photogenerated carriers, which is confirmed by the time-varying photoconductivity of the device. (10.1016/j.synthmet.2011.12.021)
  DOI : 10.1016/j.synthmet.2011.12.021
• Low temperature plasma deposition of silicon thin films: From amorphous to crystalline
  
  • Roca I Cabarrocas Pere
  • Cariou Romain
  • Labrune Martin
  Journal of Non-Crystalline Solids, Elsevier, 2012, 358 (17), pp.2000-2003. We report on the epitaxial growth of crystalline silicon films on (100) oriented crystalline silicon substrates by standard plasma enhanced chemical vapor deposition at 175 °C. Such unexpected epitaxial growth is discussed in the context of deposition processes of silicon thin films, based on silicon radicals and nanocrystals. Our results are supported by previous studies on plasma synthesis of silicon nanocrystals and point toward silicon nanocrystals being the most plausible building blocks for such epitaxial growth. The results lay the basis of a new approach for the obtaining of crystalline silicon thin films and open the path for transferring those epitaxial layers from c-Si wafers to low cost foreign substrates. (10.1016/j.jnoncrysol.2011.12.113)
  DOI : 10.1016/j.jnoncrysol.2011.12.113
• Developing low-cost graphene devices
  
  • Lee Chang-Soek
  • Moujahid Waleed
  • Lebental Bérengère
  • Châtelet Marc
  • Le Normand François
  • Maurice Jean Luc
  • Cojocaru Costel-Sorin
  , 2012. In spite of numerous efforts for developing the applications of graphene, it remains difficult to put the remarkable physical properties of this material into devices. This is mainly due to the fact that large-area (industrial) graphene includes in its structure and on its surfaces a significant density of defects that make as many traps and scattering centres for charge carriers. The idea of the present work, contrary to diminishing the defect density, is to use the defects and the very large surface to volume ratio of that 2D material, to transform it into high sensitivity sensors. When defects are useful, low-temperature growth becomes the method that best satisfies both physical and financial demands. Here, we further decrease preparation costs by performing growth not only at low temperature directly on the final insulating substrate (glass), but also by printing the device contacts by ink-jet printing. Graphene layers actually develop at the interface between a metallic catalytic film and the insulating substrate during plasma-enhanced chemical vapour deposition (PE-CVD).1,2. Resistivity of the graphene foils was measured by the four-point methods using ink-jet printed electrods, and a resistivity as low as 820 ohms/sq were obtained. Moreover, the sensitivity of such graphene foils to water vapour was evaluated, with the prospect to use them in humidity sensors for civil engineering. In this presentation, we explain how graphite may precipitate at the interface in addition to the surface.2,3 Then we show examples of graphene obtained at temperatures in between 450 and 550°C, on glass (Fig.), fused silica, alumina and SiO2//Si. Transmission electron microscopy indicates that the structure is nanocrystalline. We finally show the humidity response of the fabricated device. Results seem to indicate that high-defect density, thin deposits are more sensitive to water vapour than thicker ones.
• White organic light-emitting diodes with ultra-thin mixed emitting layer
  
  • Jeon Taewoo
  • Forget Sebastien
  • Chenais Sebastien
  • Geffroy Bernard
  • Tondelier Denis
  • Bonnassieux Yvan
  • Ishow Eléna
  Proceedings of SPIE, the International Society for Optical Engineering, SPIE, The International Society for Optical Engineering, 2012, 8258 (17), pp.82580G-1. White light can be obtained from Organic Light Emitting Diodes by mixing three primary colors, (i.e. red, green and blue) or two complementary colors in the emissive layer. In order to improve the efficiency and stability of the devices, a host-guest system is generally used as an emitting layer. However, the color balance to obtain white light is difficult to control and optimize because the spectrum is very sensitive to doping concentration (especially when a small amount of material is used). We use here an ultra-thin mixed emitting layer (UML) deposited by thermal evaporation to fabricate white organic light emitting diodes (WOLEDs) without co-evaporation. The UML was inserted in the hole-transporting layer consisting of 4, 4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl (α-NPB) instead of using a conventional doping process. The UML was formed from a single evaporation boat containing a mixture of two dipolar starbust triarylamine molecules (fvin and fcho) presenting very similar structures and thermal properties and emitting in complementary spectral regions (orange and blue respectively) and mixed according to their weight ratio. The composition of the UML specifically allows for fine tuning of the emission color despite its very thin thickness down to 1 nm. Competitive energy transfer processes from fcho and the host interface toward fvin are key parameters to control the relative intensity between red and blue emission. White light with very good CIE 1931 color coordinate (0.34, 0.34) was obtained by simply adjusting the UML film composition. (10.1117/12.908156)
  DOI : 10.1117/12.908156
• Experimental validation of Mueller matrix differential decomposition
  
  • Ortega-Quijano Noé
  • Haj-Ibrahim Bicher
  • García-Caurel Enric
  • Arce-Diego José Luis
  • Ossikovski Razvigor
  Optics Express, Optical Society of America - OSA Publishing, 2012, 20 (2), pp.1151-1163. Mueller matrix differential decomposition is a novel method for retrieving the polarimetric properties of general depolarizing anisotropic media [N. Ortega-Quijano and J. L. Arce-Diego, Opt. Lett. 36, 1942 (2011), R. Ossikovski, Opt. Lett. 36, 2330 (2011)]. The method has been verified for Mueller matrices available in the literature. We experimentally validate the decomposition for five different experimental setups with different commutation properties and controlled optical parameters, comparing the differential decomposition with the forward and reverse polar decompositions. The results enable to verify the method and to highlight its advantages for certain experimental applications of high interest. (10.1364/OE.20.001151)
  DOI : 10.1364/OE.20.001151
• Stability to photo-oxidation of rubrene and fluorine-substituted rubrene
  
  • Uttiya S.
  • Raimondo L.
  • Campione M.
  • Miozzo L.
  • Yassar A.
  • Moret M.
  • Fumagall E.
  • Borghesia A.
  • Sassellaa A.
  Synthetic Metals, Elsevier, 2012, 161 (23), pp.2603-2606. Rubrene, among organic semiconductors, displays very high charge carrier mobility in the solid state and this is why it has become a very promising material for various device applications. Unfortunately, rubrene also exhibits a rather low stability, affecting device lifetime, because it is very prone to photo-oxidation. In order to limit this problem, a new substituted-rubrene was synthesized, which should be more stable, still having a good transport behaviour in the solid state. In this paper, we show how molecule degradation by reaction with oxygen under light makes the solutions and thin films become colorless, as observed by monitoring in time the evolution of absorbance. We found that the degradation of rubrene in both solutions and thin films is faster than that of the fluorine-substituted molecule. These results demonstrate that the introduction of fluorine can be a way to enhance the stability of rubrene to photo-oxidation. (10.1016/j.synthmet.2011.08.006)
  DOI : 10.1016/j.synthmet.2011.08.006
• Amphiphilic conjugated block copolymers for efficient bulk heterojunction solar cells
  
  • Suspene C.
  • Miozzo L.
  • Choi J.
  • Gironda R.
  • Geffroy B.
  • Tondelier D.
  • Bonnassieux Y.
  • Horowitz G.
  • Yassar Abderrahim
  Journal of Materials Chemistry, Royal Society of Chemistry, 2012, 22, pp.4511-4518. The synthesis of random and diblock copolymers of poly(3-alkylthiophene)s bearing polar substituents was successfully developed by GRIM polymerization. 3-Hexyl-thiophene was successfully copolymerised with a new derivative, 3-functionalised-thiophene (propyl 5-(2-(thiophen-3-yl)ethoxy)pentanoate), bearing an ester function. Under optimized conditions, this ester proved to be fully compatible with the Grignard metathesis polymerization. Saponification of the copolymer esters provided the corresponding polyacids. Photovoltaic properties of copolymers were investigated in bulk heterojunction devices with PC61BM as acceptor. Among all the amphiphilic copolymers, P3HT-b-P3AcidHT showed the best performance with a PCE of 4.2%, an open-circuit voltage (Voc) of 0.60 V, a short-circuit current density (Jsc) of 13.0 mA cm−2, and a fill factor (FF) of 0.60. (10.1039/C2JM14960E)
  DOI : 10.1039/C2JM14960E
• Nitrogen-Doped Carbon Nanotubes as a Highly Active Metal-Free Catalyst for Selective Oxidation
  
  • Chizari Kambiz
  • Deneuve Adrien
  • Ersen Ovidiu
  • Florea Ileana
  • Liu Yu
  • Edouard David
  • Janowska Izabela
  • Begin Dominique
  • Pham-Huu Cuong
  ChemSusChem, ChemPubSoc Europe/Wiley, 2012, 5 (1), pp.102-108. (10.1002/cssc.201100276)
  DOI : 10.1002/cssc.201100276
• DNA detection with a water-gated organic field-effect transistor
  
  • Kergoat Laurent
  • Piro B.
  • Berggren M.
  • Pham M. C.
  • Yassar A.
  • Horowitz G.
  Organic Electronics, Elsevier, 2012, 13 (1), pp.1-6. A DNA sensor based on a water-gated organic field-effect transistor is described. The semiconductor is poly [3-(5-carboxypentyl)thiophene-2,5-diyl] onto which DNA probes are covalently grafted via NHS/EDC chemistry. Clear changes in the output characteristic of the device are observed upon DNA immobilization and after DNA hybridization. Experimental data point out the importance of the electrolyte Debye length that can screen negative DNA charges and impede transduction. For this reason, deionized water was used in order to increase the Debye length up to several hundreds of nanometers. In this case, a decrease in the off current was observed upon hybridization, whereas no significant change occurred when using saline solutions. (10.1016/j.orgel.2011.09.025)
  DOI : 10.1016/j.orgel.2011.09.025
• Probing dusty-plasma/surface interactions with a heat flux microsensor
  
  • Abolmasov Sergey
  • Cormier Pierre-Antoine
  • Torres Rios A.
  • Dussart Remi
  • Semmar Nadjib
  • Thomann Anne-Lise
  • Roca I Cabarrocas Pere
  Applied Physics Letters, American Institute of Physics, 2012, pp.100, 1, 011601. Heat flux microsensor--a thermopile with millisecond response time--was employed for direct measurements of total energy flux to a floated surface in a dusty rf discharge. The measurements were performed in silane-hydrogen plasmas at discharge conditions close to those used for the growth of polymorphous silicon films. At rf power between 10 and 50 W, the measured energy flux was in the range of 20-250 mW/cm2. Due to fast time response, the thermopile was also capable of tracing the dynamics of nanoparticle growth. A significant decrease (about 30%) in the energy flux was observed during the agglomeration phase. (10.1063/1.3674290)
  DOI : 10.1063/1.3674290
• 2,2'-Biphospholes: building blocks for tuning the HOMO-LUMO gap of π-systems using covalent bonding and metal coordination.
  
  • Chen Hui
  • Delaunay Wylliam
  • Yu Liujian
  • Joly Damien
  • Wang Zuoyong
  • Li Jin
  • Wang Zisu
  • Lescop Christophe
  • Tondelier Denis
  • Geffroy Bernard
  • Duan Zheng
  • Hissler Muriel
  • Mathey François
  • Réau Régis
  • Réau Régis
  Angewandte Chemie International Edition, Wiley-VCH Verlag, 2012, 51 (1), pp.214-7. new angle: The insertion of a 2,2′-biphosphole subunit into π-conjugated systems offers a new way to control the HOMO-LUMO gap. Tuning of the dihedral angle (θ) between the two phosphorous heterocycles, either by metal coordination or covalent bonding through the P substitution can lead to control of the band gap. These new π-conjugated systems can be used as emitting materials in white organic light-emitting devices (WOLEDs). (10.1002/anie.201105924)
  DOI : 10.1002/anie.201105924
• Genetic framework of cyclin-dependent kinase function in Arabidopsis
  
  • Nowack M.K.
  • Harashima H.
  • Dissmeyer N.
  • Zhao X.
  • Bouyer D.
  • Weimer A.K.
  • de Winter F.
  • Yang F.
  • Schnittger A.
  Developmental Cell, Elsevier, 2012, 22 (5), pp.1030-40. Cyclin-dependent kinases (CDKs) are at the heart of eukaryotic cell-cycle control. The yeast Cdc2/CDC28 PSTAIRE kinase and its orthologs such as the mammalian Cdk1 have been found to be indispensable for cell-cycle progression in all eukaryotes investigated so far. CDKA;1 is the only PSTAIRE kinase in the flowering plant Arabidopsis and can rescue Cdc2/CDC28 mutants. Here, we show that cdka;1 null mutants are viable but display specific cell-cycle and developmental defects, e.g., in S phase entry and stem cell maintenance. We unravel that the crucial function of CDKA;1 is the control of the plant Retinoblastoma homolog RBR1 and that codepletion of RBR1 and CDKA;1 rescued most defects of cdka;1 mutants. Our work further revealed a basic cell-cycle control system relying on two plant-specific B1-type CDKs, and the triple cdk mutants displayed an early germline arrest. Taken together, our data indicate divergent functional differentiation of Cdc2-type kinases during eukaryote evolution. (10.1016/j.devcel.2012.02.015)
  DOI : 10.1016/j.devcel.2012.02.015