Assemblage de complexes inorganiques sur nanotubes de carbone monoparoi (Applications à la spintronique moléculaire et à la photocatalyse)

La spintronique moléculaire et la photocatalyse sont deux domaines en constante évolution. Le premier s attache à exploiter la possibilité de coupler deux phénomènes physiques, à savoir le transport d un flux de porteurs de charges et le spin de l électron, tandis que le second se concentre sur l exaltation des propriétés chimiques de transfert d électrons d une espèce donnée grâce au phénomène physique d irradiation lumineuse. Depuis quelques années, les nanotubes de carbone ont suscité un grand intérêt à la fois en tant que composant pour la spintronique moléculaire, en raison de leur grande cohérence de spin, et en tant que support idéal pour la catalyse moléculaire, grâce à leurs exceptionnelles propriétés électroniques de surface. Au cours de ce travail de thèse, nous nous sommes attachés à concevoir des complexes inorganiques possédant des propriétés physiques, (magnétiques ou optiques) et des propriétés chimiques (permettant leur assemblage non-covalent sur des nanotubes de carbone monoparoi) de manière à former des adduits complexes inorganiques-nanotubes aux propriétés exploitables en spintronique moléculaire et en photocatalyse. Les propriétés des complexes synthétisés ont été extensivement caractérisées (Chapitre 2), et les plus prometteurs de ces composés ont été assemblés avec succès sur les nanotubes de carbone (Chapitre 3), comme en attestent les mesures spectroscopiques réalisées. Enfin, les deux domaines d applications concernés par nos travaux faisant intervenir des phénomènes de transport électronique, des études spécifiques sur des dispositifs électriques de type transistor à effet de champ dont le canal de conduction est constitué de nanotubes de carbone ont été réalisées (Chapitre 4). Celles-ci mettent à chaque fois en évidence l existence d une communication électronique entre les complexes inorganique et les nanotubes de carbone sur lesquels ils sont assemblés au sein des dispositifs. Bien qu au final un couplage entre les propriétés magnétiques des complexes synthétisés et les propriétés de transport des nanotubes n ait pas pu être mis en évidence, de nombreux phénomènes inattendus et extrêmement intéressants tels que des effets ambipolaires, des transferts de charge ou des ruptures de liaisons ont été observés. Par contre, un fort couplage opto-électronique a pu être obtenu entre un complexe et le flux de porteurs de charge des dispositifs, ce qui s avère être de très bon augure pour des futures applications en photocatalyse.Molecular spintronic and photocatalysis are two fields in constant evolution. While the first deals with the coupling of two physical properties, the flux of charge carriers and the spin of the electron, the second is focusing on the enhancement of the electron transfer of chemical species under light irradiation. Recently, there has been an increasing interest in carbon nanotubes as new components for molecular spintronics, since they possess high spin coherence, and as ideal materials for molecular catalysis, for their tremendous electronic surface properties. Our work consisted in conceiving inorganic complexes with both physical (magnetic or optic) and chemical (ability of realizing non covalent assembly on single-walled carbon nanotubes) properties, in order to create new nanotube-complex nanohybrids which could be exploited for molecular spintronics or photocatalysis applications. The properties of the synthesized complexes were extensively characterized (Chapter 2), and the most promising molecules were successfully assembled onto carbon nanotubes, as is proven by the spectroscopic measurement which were performed (Chapter 3). Finally, since both domains of applications we considered involve electronic transportation, specific studies were realized on field effect transistor devices with carbon nanotubes as the conduction channel (Chapter 4). They evidence strong electronic communications between the inorganic complexes and the carbon nanotubes onto which they are assembled in the devices. Even if in the end no coupling was observed between the magnetic properties of the inorganic complexes and the transport ones of the carbon nanotubes, numerous unexpected and very interesting phenomena such as ambipolar behavior, charge transfer effect or bond cleavage were evidenced. As for the optoelectronic coupling which was investigated for photocatalytic applications, a first step was made as the transport of the carbon nanotube field effect transistor devices onto which a complex was assembled shows a strong dependence with the applied light irradiation.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Long-Range Electron Transport in Prussian Blue Analog Nanocrystals

We report electron transport measurements through nano-scale devices consisting of 1 to 3 Prussian blue analog (PBA) nanocrystals connected between two electrodes. We compare two types of cubic nanocrystals, CsCoFe (15 nm) and CsNiCr (6 nm), deposited on highly oriented pyrolytic graphite and contacted by conducting-AFM. The measured currents show an exponential dependence with the length of the PBA nano-device (up to 45 nm), with low decay factors \b{eta}, in the range 0.11 - 0.18 nm-1 and 0.25 - 0.34 nm-1 for the CsCoFe and the CsNiCr nanocrystals, respectively. From the theoretical analysis of the current-voltage curve for the nano-scale device made of a single nanoparticle, we deduce that the electron transport is mediated by the localized d bands at around 0.5 eV from the electrode Fermi energy in the two cases. By comparison with previously reported ab-initio calculations, we tentatively identify the involved orbitals as the filled Fe(II)-t2g d band (HOMO) for CsCoFe and the half-filled Ni(II)-eg d band (SOMO) for CsNiCr. Conductance values measured for multi-nanoparticle nano-scale devices (2 and 3 nanocrystals between the electrodes) are consistent with a multi-step coherent tunneling in the off-resonance regime between adjacent PBAs, a simple model gives a strong coupling (around 0.1 - 0.25 eV) between the adjacent PBA nanocrystals, mediated by electrostatic interactions

Hybrid nanostructures based on gold nanoparticles and functional coordination polymers: Chemistry, physics and applications in biomedicine, catalysis and magnetism

During the last decade, the scientific community has become interested in hybrid nanomaterials, especially the ones that combine gold nanoparticles with a second functional component. In this context, coordination polymers are materials that possess potential advantages over conventional inorganic nanomaterials and organic compounds such as chemical versatility, easy processability, high specific area, low toxicity, biodegradability and electronic and magnetic functionalities to name a few. In this manner, the wise integration of Au nanoparticles with coordination polymers in different types of nanostructures has allowed extending the scope of properties and applications of these systems, allowing also overcoming some of the limitations of Au nanoparticles for certain applications. Therefore, in this review, we discuss the different reported hybrid nanostructures based on the integration of colloidal Au nanoparticles with coordination polymers exhibiting either physical properties of interest (e.g. ferromagnetism, photo-magnetism, spin switching, etc.) or chemical properties (e.g. electrocatalysis). We have paid particular attention to the enhanced properties and the synergistic effects that can emerge from this association. Along this front, thanks to their improved and/or novel properties, these hybrid materials have become promising nanostructures for several applications, especially in biomedicine, catalysis, magnetism and sensing

Hysteresis in a bimetallic holmium complex : A synergy between electronic and nuclear magnetic interactions

We report a bimetallic holmium(III) complex showing a S-shaped magnetic hysteresis at low temperature. The complex is investigated by x-ray crystallography, magnetometry, single crystal microsquid measurements, and first-principles calculations. A model Hamiltonian including electronic and nuclear magnetic moments is used to fit all experimental data. We conclude that the Ho(III) may be described as non-Kramers doublets with respective gaps of Delta(A) = 0.8 and Delta(B) = 10 cm(-1) and that there is a small ferromagnetic coupling of J = 1 cm(-1) ((H) over cap (S) = -JS(A) . S-B). As in previous works, the hysteresis arise from the hyperfine structure of the Ho(III) ions. The S-shaped form of the hysteresis reflects the avoided crossing of the electronic states in the non-Kramers doublets.Peer reviewe

Coupling Nanostructured CsNiCr Prussian Blue Analogue to Resonant Microwave Fields

Collective spin excitations in magnetically ordered materials are exploited for advanced applications in magnonics and spintronics. In these contexts, conditions for minimizing dissipative effects are sought in order to obtain long living excitations that can be coherently manipulated. Organic and coordination magnetic materials may offer alternative options for their flexibility and low spin-orbit effects. Likewise, ferromagnetic nanostructures provide a versatile platform for hybrid architectures, yet downsizing affects the dynamics of magnetic excitations and needs to be controlled. Here we report a systematic investigation on insulating CsNiCr Prussian blue analogue with different degree of nanostructuring. Combining complementary microwave spectroscopic techniques, we performed magnetic resonance in a wide temperature range across the bulk ferromagnetic transition occurring at TC=90 K. This allows us to monitor key parameters of the spin dynamics through different types of nanostructured samples. We found that, below TC, the Gilbert damping parameter of 10 nm nanoparticles compares well (10-3) with values reported for prototypical inorganic analogues (YIG). Strong coupling with the microwave field of a planar microstrip resonator is then observed for bulk CsNiCr as well as for mutually interacting NPs. These results clarify conditions for the coherent manipulation of collective spin degrees of freedom in nanostructured coordination materials

Electrical-field-induced structural change and charge transfer of lanthanide-salophen complexes assembled on carbon nanotube field effect transistor devices.

International audienceThe application of a negative gate voltage on a carbon nanotube field effect transistor decorated by a binuclear Tb(III) complex leads to the generation of a negatively charged mononuclear one, presenting an electron density transfer to the nanotube and ambipolar behaviour

The Influence of Voluntary Disclosure, Stock Beta, and Firms Size on Cost of Equity Capital

This study aimed to examine the effect of voluntary disclosure, stock beta, and firm sizeon the cost of equity capital in manufacturing companies in the period 2013-2015. Thisresearch used purposive sampling method and analyzed by multiple regression, totalsample 39 manufacturing companies listed in BEI period 2013-2015. The results showedthat voluntary disclosure did not affect the cost of equity disclosure, the more voluntarydisclosure had not been able to decrease the occurrence of cost of equity disclosure, betaof stock variables affected the cost of equity capital, because the stock beta was an indicatorto see the condition of the company\u27s financial health, the company had no effect onvoluntary disclosure, this result showed that the size of a company\u27s size could notreduce the risk level