1,721,031 research outputs found
Two photon absorption and photochromism of ruthenium complexes : application optical data storage
No full textLe développement des nouvelles technologies, de l'informatique et d'internet ces dernières décennies s'est accompagné d'une demande croissante de supports de stockage de l'information. En particulier, le stockage optique de données. Les supports conventionnels (Cd-Rom, Blue-ray…), basés sur un stockage en surface du disque, ont atteint aujourd'hui leurs limites. Une nouvelle technologie en cours de développement, basée sur un stockage de données en trois dimensions, est une alternative prometteuse pour supplanter les supports conventionnels. Les matériaux doivent intégrer des entités aux propriétés photochromes (commutateur moléculaire) et d'absorption multi-photonique démontrées. Au cours de cette thèse, nous avons envisagé la synthèse de molécules fonctionnelles qui présenteraient ces deux caractéristiques. Dans un premier temps, nous nous sommes intéressés à la synthèse et à l'étude comparative de complexes homo et hétéroleptiques de ruthénium présentant une certaine potentialité pour l'absorption à deux photons. Nous avons montré que ces systèmes étaient très actifs et qu'ils permettaient d'accueillir une entité photochrome sans perte des propriétés bi-photoniques. Nous avons par la suite étudié les propriétés en photochromisme de complexes de ruthénium tris-bipyridine originaux comprenant un motif azobenzène. La complexation au métal bouleverse profondément le photochromisme de l'azobenzène avec des caractéristiques cinétiques notablement différentes de celles des ligands. Enfin, nous avons étudié les propriétés de complexes hybrides composés de ligands pour l'absorption à deux photons et d'autres pour le photochromisme, ces composés sont actifs dans ces deux domaines. Nous discutons finalement du potentiel du comportement optique de films composés de ces complexes. Nous avons procédé à des essais préliminaires de modulation du signal SHG sur ces films. Nous souhaitons optimiser toutes les composantes du processus afin de déterminer le potentiel de ces composés en stockage optique de données.The development of new technologies , computer and internet in recent decades has been accompanied by an increasing demand for media storage information. In particular , the optical data storage .Conventional media ( CD-ROM , Blu-ray ... ) based on a storage disk surface, have now reached their limits. A new technology being developed , based on a data storage in three dimensions, is a promising alternative to replace conventional materials. Materials must include entities for photochromic properties (molecular switch) and multi- photon absorption demonstrated. In this thesis , we considered the synthesis of functional molecules which present these two characteristics. As a first step , we are interested in the synthesis and comparative study of homo and heteroleptic ruthenium complex having a certain potential for two-photon absorption . We have shown that these systems were very active and they allowed to host a photochromic entity lossless bi- photonic properties. We then studied the properties of originals photochromic ruthenium tris- bipyridine containing an azobenzene motif. The metal complexing profoundly changes the photochromism of azobenzene with significantly different from those ligands kinetics . Finally, we studied the properties of hybrid complexes of ligands for the two-photon absorption and others to photochromism , these compounds are active in both areas. We finally discuss the potential of the optical behavior of compounds of these complex films. We conducted preliminary tests of the SHG signal modulation on these films. We want to maximize all components of the process to determine the potential of these compounds in optical data storage
Design of ruthenium-alkynyl complexes as nonlinear optical chromophores
No full textInternational audienceThis review paper focuses on the design and non linear optical properties of trans-Ru(dppe)2 (dppe = 1,2-bis(diphenylphosphino)ethane) alkynyl complexes and their derivatives. These systems constitute remarkable second and third-order non linear optical active chromophores. Furthermore, modifying the environment around the ruthenium affords the possibility of tuning their non linear optical performances and accessing facile non linear optical switching. The coverage is focused on quadratic (second-order) and cubic (third-order) non linear optical properties measured at molecular level from solution studies as well as on non linear optical properties of bulk material
Ruthenium (II) polypyridyl complexes as two-photon absorbers and sensitizers: Design, structure-properties relationships and applications
No full textInternational audienceThis review addresses recent advancements in understanding multiphoton excitation of ruthenium polypyridyl complexes, highlighting their relevance in the fields of molecular materials and bio-medical applications. Emphasis is placed on two-photon absorption and two-photon excited photoluminescence for which these complexes meet several requirements as two-photon sensitizers. Alongside their appealing one-photon properties, these complexes are photostable under two-photon excitation and can exhibit noticeable two-photon absorption cross-sections in the near-infrared (NIR) region. Moreover, the presence of the ruthenium atom favors spin–orbit coupling, facilitating rapid and efficient population of triplet excited states, thereby extending emission lifetimes, or uncaging reactions, according to their structural characteristics. Indeed, ruthenium polypyridyl complexes offer great versatility in terms of functionalization, enabling property fine-tuning. This review also outlines forthcoming challenges and prospects in the field through representative examples in the area of materials, bio-imaging and phototherapies
Design of surface-grafted molecular sensors for the detection of metallic trace elements
No full textLe but de ce travail de recherche était de développer une nouvelle génération de capteurs moléculaires, à l’échelle micrométrique, pour la détection, par luminescence, d’éléments-traces métalliques, également appelés métaux lourds. Nous nous sommes orientés vers la conception de structures moléculaires polyfonctionnelles greffables sur des surfaces polymères, par voie photochimique. Ces structures moléculaires sont divisibles en trois fragments : une partie photocliquable permettant de greffer le système sur la surface, un récepteur pouvant interagir avec les analytes, et un transducteur luminescent servant à traduire ces interactions. La conception des surfaces a été réalisée par photopolymérisation à deux photons. Cette méthode autorise une précision de polymérisation de l’ordre du micromètre amenant ainsi à la miniaturisation des nos systèmes. Le développement d’une méthode de greffage « photo-click » activée, au moyen de dérivés binaphtyles de tétrazoles, nous a permis de réaliser la fonctionnalisation des surfaces. Ces tétrazoles ont été conçus au titre d’absorbeurs mono- et bi-photoniques. Cette méthode permet d’atteindre un contrôle spatial précis du greffage des sondes, un objectif étant l’obtention d’une surface dite « multiplexée » visant à la détection luminescente simultanée de plusieurs analytes. La détection luminescente des analytes a été conçue sur la base de transferts d’électron photoinduits (PET) : en l’absence d’analyte, l’émission de luminescence est éteinte, par un transfert d’électron du récepteur au transducteur. La fluorescence est retrouvée lorsqu’un analyte spécifique interagit avec le récepteur, ce qui permet de révéler sa présence. Le modèle moléculaire (tétrazole-BODIPY-récepteur) développé au cours de cette thèse permet de réunir ces trois propriétés : greffage par photo-activation contrôlée, interaction récepteur-analyte, détection par luminescence. Leurs utilisations à l’interface solide-liquide, permettent d’envisager le développement de surfaces multiplexées de taille micrométrique pour la détection d’éléments-traces métalliques, intégrables dans des dispositifs miniaturisés.The aim of this research work was to develop a new generation of molecular sensors, at the micrometric scale, for the detection, by luminescence, of metallic trace elements, also called heavy metals. We have moved towards the design of polyfunctional molecular structures that can be grafted onto polymer surfaces, by photochemical means. These molecular structures are divisible into three fragments: a photoclickable part allowing the system to be grafted onto the surface, a receptor that can interact with the analytes, and a luminescent transducer used to translate these interactions. The surface design was carried out by two-photon photopolymerization. This method allows polymerization precision of the order of a micrometer, thus leading to the miniaturization of our systems. The development of an activated “photo-click” grafting method, using binaphthyl derivatives of tetrazoles, allowed us to achieve surface functionalization. These tetrazoles were designed as mono- and bi-photon absorbers. This method makes it possible to achieve precise spatial control of the grafting of the probes, one objective being the obtaining of a so-called “multiplexed” surface aimed at the simultaneous luminescent detection of several analytes. Luminescent detection of analytes was designed on the basis of photoinduced electron transfers (PET): in the absence of analyte, the luminescence emission is extinguished, by an electron transfer from the receiver to the transducer. Fluorescence is found when a specific analyte interacts with the receptor, revealing its presence. The molecular model (tetrazole-BODIPY-receptor) developed during this thesis makes it possible to bring together these three properties: grafting by controlled photo-activation, receptor-analyte interaction, detection by luminescence. Their uses at the solid-liquid interface make it possible to consider the development of micrometric-sized multiplexed surfaces for the detection of metallic trace elements, which can be integrated into miniaturized devices
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Selectivite de processus organometalliques induite par des ligands phosphores : synthese de nouveaux complexes soufres du fer
No full textSIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
Design of photoactivables molecular bricks : from the molecule towards the materials
No full textL’absorption à deux-photons est un phénomène d’optique non-linéaire dans lequel une molécule absorbe simultanément deux photons et fait l’objet d’une attention considérable en raison de ces nombreux avantages tels que le contrôle spatio-temporel, une excellente résolution tridimensionelle, ainsi qu’une profondeur de pénétration accrue des tissus et matériaux. Ces avantages répondent aux prérequis pour des applications dans des domaines allant de la science des matériaux à la médecine avec la limitation optique, la bio-imagerie et le photothérapie dynamique. L’objectif de ces travaux est de synthétiser de nouvelles familles de complexes de ruthénium(II) et de comprendre les mécanismes photophysiques impliqués dans ces différentes familles et d’explorer la synthèse et étude d’un complexe pour la photothérapie dynamique. La première partie de ce manuscrit est centrée sur la synthèse de nouveaux ligands de types bipyridyles et des compexes hétéro- et homoleptiques de ruthénium(II) correspondants ainsi qu’à leurs caractérisations par résonance magnétique nucléaire. Nous cherchons ensuite à comprendre l’influence des ligands sur les propriétés d’absorption à un-photon et d’émission en s’appuyant sur des études théoriques TD-DFT. Ensuite, nous tentons de faire la corrélation entre l’absorption à deux-photons et ce que nous avions observé précédemment en absorption à un-photon. Finalement, nous avons synthétisé et fais l’étude préliminaire (RMN, absorption à un-photon et émision) d’un nouveau complexe pour la photothérapie dynamique à deux-photons.Two-photon absorption, in which a molecule absorbs two low energy photons of identical or different frequencies at the same time, has received considerable attention owing its advantages over one-photon based processes. These advantages include the ability for spatiotemporal control of excitation and intrinsic three-dimensional resolution together with increased penetration depth in tissues or materials, while causing less damage to material or biological samples Such benefits meet the prerequisites for promising applications, from optical materials science to medicine such as optical limiting, bio-imaging and photodynamic therapy. The aim of this work is to synthesize three new ruthenium(II) complexes family and to understand the photo-physics involved in these models as well as to explore the synthesis and photophysical studies of a complex for the photodynamic therapy. The first part of this manuscript is devoted to the synthesis of three new bipyrdyls ligands and their corresponding hetero- and homoleptics ruthneium(II) complexes as well as their nuclear magnetic resonance spectroscopy characterisation. We seek to understand the one-photon absorption and emission behavior of these ligands and corresponding complexes with the TD-DFT theoritical studies. Then, we try to undertand the relationship between the two-photon absorption and the one-photon absorption observed previously. Finally, we synthesize and study a new ruthenium(II) complex for the two-photon photodynamic therap
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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