Carbon-doped aluminium oxide, α-Al₂O₃:C, is a ultra-sensitive dosimeter of topical research interest. The aim of this project was to investigate the dynamics of luminesce in this material. The methods of investigation consisted of thermoluminescence and time-resolved optical stimulation. Thermoluminescence measurements provide information on trap distribution and kinetic parameters of the traps involved in luminescence whereas time-resolved optical stimulation is a handy technique in investigation of luminescence lifetimes and provides an insight into the charge transitions between traps and recombination centres. Measurements were made on samples annealed at a nominal temperature of 900⁰C for 15 minutes. The material shows the presence of five thermoluminescence peaks at 37⁰C, 160⁰C, 300⁰C 410⁰C, and 480⁰C at a heating rate of 0.03k/s when irradiated to 6.0 Gy of beta. The main peak at 160⁰C, shows a linear dose response for doses between 0.1 Gy and 10 Gy and then goes sublinear above 10 Gy, the peak at 37⁰C shows a sublinear dose response for doses between 0.1 Gy and 10 Gy and appears to saturate thereafter, whereas the dose response of the peak at 300⁰C goes from linear to supralinear then apparently quadratic behaviour in the dose range of 0.1 Gy to 16.0 Gy. The trap depth of the main peak, that is, its activation energy as determined below the conduction band, has been approximated at 1.3 eV with a kinetic order of approximately 1.2. Time-resolved optical stimulation has been used to investigate luminescence lifetimes. The mean luminescence lifetime obtained for the sample at ambient temperatures is 35.0±1.0 ms. The investigations of the dependence of luminescence lifetimes on measurement temperature show that the material suffers from thermal quenching effects at measurement temperatures above 140⁰C with the activation energy of thermal quenching estimated at 1.045±0.002 eV. Shallow traps i.e. traps lying close to the conduction band, seem to elongate the lifetimes of optically stimulated luminescence in the material at temperatures between 30⁰C - 80⁰C due to charge retrapping. The material exhibits both fading and recuperation of the optically stimulated luminescence signal with storage time.

Ce travail porte sur la conception de nouveaux systèmes luminescents à partir de complexes hexanucléaires de terres rares et l'étude de leurs propriétés physico-chimiques. Ces complexes de formule chimique [Ln6(μ6-O)(μ3-OH)8(NO3)6(H2O)n](NO3)2.mH2O avec 0 n 14 et 0 m 6 pour Ln = Pr-Lu, Y peuvent être synthétisés et isolés par hydrolyse contrôlée de sels de terres rares. Ces complexes sont structuralement caractérisés : les ions terres rares occupent les sommets d'un octaèdre moléculaire d'une dizaine d'angströms de diamètre. Ils présentent un intérêt en tant que précurseurs moléculaires. Les complexes hétéro-hexanucléaires, associant plusieurs terres rares, affichent potentiellement des interactions de forte amplitude en termes de luminescence. L’ordre local de ces complexes a été étudié notamment par RMN du noyau 89Y à l’état solide et en solution. Ces complexes ne montrent pas de ségrégation macroscopique, et sont des solutions solides où les terres rares sont statiquement et aléatoirement réparties sur les sommets de chaque entité moléculaire. Ces interactions ont été exploitées afin d’optimiser les propriétés inédites de luminescence d’un polymère de coordination à base d’entités hexanucléaires. Ces propriétés sont modulables en fonction de la sélection des précurseurs. Ces complexes présentent une affinité particulière pour les solvants de type polyol, notamment l’éthylène glycol. En solution, les entités moléculaires se regroupent par le biais de ponts glycol et forment des nano-agrégats. Enfin, cette affinité particulière pour les polyols, nous a poussé à étudier les propriétés de luminescence en solution lorsque les complexes sont fonctionnalisés par des dérivés aromatiques du glycol. / This work focuses on the design of new luminescent systems built from rare earth based-hexanuclear complexes and on the study of their properties. These complexes of general formula [Ln6(μ6-O)(μ3-OH)8(NO3)6(H2O)n](NO3)2.mH2O with 0 n 14 and 0 m 6 when Ln = Pr-Lu, Y can be synthesized and isolated by controlled hydrolysis of rare earth salts. These complexes are structurally characterized: metal cations are located at each vertex of the molecular octahedron, whose diameter is around 10 . They are of interest as molecular precursors. Hetero-hexanuclear complexes, involving several rare earth ions, potentially exhibit efficient interactions in terms of luminescence. Local order of these complexes was investigated on the basis of NMR spectroscopy with 89Y nucleus at solid and solution state. No macroscopic segregation is observed, heterohexanuclear complexes are solid solution compounds where rare earth ions are randomly and statistically dispersed over the vertices of each molecular entities. Interactions in terms of luminescence have been exploited in order to optimize the rare optical properties of a coordination polymer built from hexanuclear entities. The luminescent properties can be modulated depending on the selection of the starting precursors. Hexanuclear complexes have a particular affinity for polyol solvents, especially ethylene glycol. In solution, molecular entities are bridged together to form nano-agregates. Finally, this particular affinity for polyol, prompted us to investigate luminescence properties of aromatic glycol derivatives functionalized complexes.

M.Phil. (Chemistry) / This project concerns the study of , specifically, the incomplete fusion mechanism. The nuclear reaction 7Li + 176Yb at 50 MeV was therefore carried out using the AFRODITE and DIAMANT facility of iThemba LABS. A 7Li nuclide is considered suitable for the breakup fusion (incomplete fusion) reaction because of its well developed cluster structure of an -particle and triton which are weakly bound in this nucleus. One of the breakup fragments may be captured by the target while the other escapes at the beam velocity. Light charged-particles (alpha, tritons, deuterons and protons) were detected with the DIAMANT (CsI) array in co-incidence with gammarays detected by the AFRODITE (HPGe) spectrometer. The light particle detection in co-incidence with gamma detection was an important innovation that allowed exclusivity in the reconstruction of the mechanism by which specific residues were produced. Off-line data processing was used to produce charged-particle-gated gamma-gamma coincidence matrices which were analysed with the RADWARE software package. The level scheme exclusive to a particular channel for the production of the 178Hf was extracted. The relative cross-section for the various reaction channels could also therefore be extracted. In particular, the intensity ratios of gamma transitions as function of spin for proton to triton-gated matrices populating the 178Hf isotope were extracted. Insights could be developed into the incomplete fusion reaction mechanisms initiated by the breakup of the incident 7Li projectile.

No description available.

Ce travail est consacré à la synthèse et à la caractérisation de commutateurs et de fils moléculaires. La première partie est une étude bibliographique qui présente les avantages et les applications des unités moléculaires utilisées dans le contexte de l’électronique moléculaire. La deuxième partie de ce manuscrit traite de la préparation, des études électrochimiques et photophysiques de complexes de ruthénium bimétalliques portant un coeur triarylamine. Le but est ici de moduler la luminescence de ce cœur en changeant l’état redox des groupements acetylure de ruthénium. Dans la troisième partie, des combinaisons de précurseurs de complexes de Ln (Ln = Eu ou Yb) et de groupements vinyl-ruthénium redox-actifs ont été formées afin de moduler la luminescence des centres Ln via l’oxydation des groupements vinyl-ruthénium. La quatrième partie décrit l'association d'un précurseur de complexe de Ln (Ln = Eu ou Yb) à un ligand portant une unité dithienylethene (DTE), afin de commuter l'émission de lumière du centre Ln. Ces composés ont été synthétisés avec succès et leur luminescence a été reversiblement modulée par irradiation lumineuse. Dans la dernière partie, nous décrivons la synthèse d'une série de fils moléculaires composée de complexes bis(acetylure) de ruthénium (II) terminés par des groupes fonctionnels amine, et comprenant un complexe bimétallique photochrome avec une unité DTE. Ces molécules ont été conçues de manière à être insérées entre deux électrodes de graphène pour étudier leur conductance dans les différents états redox. En outre, le complexe photochrome doit pouvoir permettre la commutation de la conductance par voie optique et électrochimique dans des jonctions moléculaires de graphène. / This work is devoted to the synthesis and characterization of novel molecular switches and wires that incorporate ruthenium organometallic moieties. First, a bibliographic chapter presents the advantages and applications of the building blocks used in the following chapters and discuss the general context of molecular electronics. The second part of this manuscript deals with preparation, electrochemical and photophysical studies of bimetallic ruthenium complexes bearing a triarylamine core. The goal is to modulate the luminescence of this core by changing the states of the redox-active ruthenium acetylide moieties. In the third part, combinations of Ln (Ln = Eu or Yb) complexes and redox-active ruthenium vinyl bipyridine moieties were formed in order to tune the luminescence of Ln center via oxidation of the redox-active ruthenium vinyl moieties. The fourth part describes an association of a Ln (Ln = Eu or Yb) precursor and a ligand bearing a dithienylethene (DTE) unit, in order to commute the light emission of the Ln center. These DTE-Ln compounds were successfully synthesized and their luminescence was reversiblely modulated by photo irradiation. In the last part, we report the synthesis of a series of redox-active molecular wires, which are ruthenium (II) bis(σ-arylacetylide) complexes terminated with amine functional groups, one of them including a photochromic DTE unit. These molecules are designed to covalently bridge a gap between graphene electrodes for probing the electrochemical gating of conductance via oxidation of the molecules. Furthermore, the photochromic complex should allow combined optical and electrochemical conductance switching in single molecule graphene junctions.

No description available.

Chapter 1: Luminescence property of lanthanide and its applications Lanthanides are well-known for their unique luminescence property and have found widespread applications in sensing, bioimaging, lasers, optoelectronic devices, etc. Due to Laporte forbidden f-f transitions, lanthanides have very low intrinsic emission. The problem can be overcome by use of an ‘antenna’, which is an organic chromophore with excited state energy higher than the lanthanides’ emitting levels. Thereby it is possible to get highly emitting lanthanide complexes through energy transfer from the ‘antenna’. Due to long lifetime of lanthanides’ excited states, it's possible to perform time delayed measurement which is useful in bioassays and bioimaging since the short-lived background emission is effectively filtered. Research in supramolecular metallogels has grown rapidly in recent years, and already proven to have potential for designing advanced materials for a variety of applications, such as sensing, optoelectronics, catalysis, nanoparticle synthesis, biomedicine etc. A supramolecular gel where a lanthanide is an integrated part of it can combine the advantages of the supramolecular gel along with the unique property of lanthanide luminescence and thus such materials can be explored for potential applications. This chapter discusses the background information on the unique luminescence of lanthanides, and some examples of the applications of lanthanide complexes and lanthanide based gels. Chapter 2: Lanthanide luminescence based enzyme sensing in hydrogels This chapter describes the use of Tb/Eu luminescence in the sensing of biologically important enzymes. We discovered the sensitization of Eu(III) in Eu-cholate gel by 1-hydroxypyrene, and of Tb(III) in Tb-cholate gel by 2,3-dihydroxynaphthalene. These two sensitizers were covalently modified and sensitizer-appended hybrid (artificial) enzyme substrates were prepared for a few biologically important hydrolases. The covalently modified sensitizer termed as “pro-sensitizers”, didn't sensitize Tb(III)/Eu(III) in the hydrogel and no photoluminescence was observed. In the presence of the appropriate enzyme in the hydrogel, the pro-sensitizer was cleaved to liberate the sensitizer, which led to an enhancement of luminescence with time. Alkaline phosphatase and β-lactamase were assayed using pyrene phosphate and pyrene-oxo-cephalosporanic acid derivatives, respectively, in Eu-cholate hydrogel (Figure 1). β-Galactosidase was assayed using Tb(III) luminescence in Tb-cholate gel. The enzyme detection was based on red/green luminescence response from the gel. To understand the behaviour of the enzymes in the hydrogel, kinetic parameters were determined. The detection of different enzymes was also demonstrated in natural/biological samples like blood serum, milk and almond extract. Figure 1. Three different pro-sensitizers used for alkaline phosphatase, β-lactamase and β-galactosidase assays Chapter 3: Enzyme sensing on paper discs using lanthanide luminescence Developing a user-friendly biosensor is of considerable importance in clinical and analytical chemistry. Paper based biosensor design is an emerging field of research and paper based point of care (PoC) testing devices have already found applications in clinical, veterinary, environmental, food safety, security etc. Paper is made out of natural cellulose fibres, and has advantages of low cost, biodegradability, biocompatibility, and user friendliness. Paper based sensors have been used for the detection of ions, glucose, proteins, nucleic acids, antigens etc., with mostly colorimetric, fluorescent, electrochemical, chemiluminescence and Electrochemiluminescence readouts. In this work, the non luminescent Tb(III) and Eu(III) were embedded on paper as their cholate hydrogels and were used for detecting different hydrolases. Pro-sensitizers, as reported in Chapter 2, were immobilized on paper for the detection of a specific enzyme. The “pro-sensitizer” released the sensitizer upon enzyme action and led to luminescence enhancement from the gel coated paper disc. By this way, four different hydrolase enzymes detection were carried out using Tb(III)/Eu(III) luminescence as the readout (Figure 2) and the practical utility was demonstrated by the detection of specific enzymes in natural/biological samples. This paper disc based enzyme sensing provides a simpler and user friendly approach over the contemporary approach of enzyme sensing typically carried out in solution. Figure 2. Paper based biosensors for hydrolase enzymes Chapter 4: Luminescence resonance energy transfer in self-assembled supramolecular hydrogels Luminescence resonance energy transfer is a phenomenon of energy transfer between a FRET (Förster resonance energy transfer) pair, where a lanthanide is the donor. Lanthanides have attracted attention for the last several decades for their unique luminescence properties. LRET is a FRET process along with added advantages of Lanthanides, i.e. long lifetime of the lanthanides and characteristics emission spectra. LRET has been used for studying interaction of biomacromolecues, immunoassay, bioassays, etc. LRET in either a supramolecular organogel or a hydrogel is still an unexplored field. In this work we showed the energy transfer from Tb(III) to two different red emitting dyes in Tb-cholate hydrogel (Figure 3). The self assembly processes during hydrogelation assisted the energy transfer process without any need for laborious synthesis. The energy transfer was confirmed by time delayed emission, excitation spectra and lifetime measurement in the hydrogels. Energy transfer was observed both in the gel and the xerogel states. These luminescent materials may find applications in optoelectronics. Figure 3. Energy transfer from DHN to Tb3+ and then to red emitting dyes (Rhodamine B & Sulforhodamine 101) in the Tb-Cholate hydrogel Chapter 5: Room temperature synthesis of Lanthanide phosphate nanoparticle using a gel as a soft template Lanthanide orthophosphates are an important class of rare earth compounds, and have widespread applications in laser materials, optical sensors, heat resistance materials, solar cell etc. There are several methods in the literature for the synthesis of rare earth phosphate nanoparticles. Most of these are based on hydrothermal, microwave assisted, micro emulsion, arrested precipitation etc., which invariably dependent on stringent conditions such as (i) high temperatures and pressures, (ii) inert atmosphere and (iii) the use of external capping agents as stabilizers. Synthesis of such nanoparticles under milder conditions would always be preferable. In this context, the preparation of nanoparticles using hydrogel as template can be a possible alternative approach. The LnPO4 nanoparticle synthesis was done by diffusion of Na3PO4 in Ln-cholate hydrogels. The particles were characterized by transmission electron microscopy (TEM) and powder XRD analysis. TEM showed the formation of 3-4 nm size particles with an ordered arrangement on the gel fibre. This work demonstrated that the lanthanide cholate gels have high potential for the synthesis, and immobilization of lanthanide phosphate nanoparticles at room temperature to produce new types of composite materials. (For structural formula pl see the abstract pdf file)

Flat dendrimers, consisting of a hexavalent aromatic core and rigid ethynyl units locked in place by ether connections were developed based upon the divergent synthetic method. Alternating functional groups were adopted on each site of the hexa-substituted benzene, in order to avoid undesired cyclization pathways. The flat structures of conjugated dendrimers would allow investigation on the discotic liquid crystal properties. In addition, these ethylnyl dendrimers are expected to show directed energy and electron transfer with a highly conjugated system, and thus are effective in the preparation of photoreactive materials such as electronic sensors or light harvesting materials. Conjugated polycyclic aromatic hydrocarbons, consisting of naphthalene, anthracene, pyrene, and phenanthrene groups connected via 1,3,5-triethynylbenzene cores, were synthesized. These molecules exhibited luminescence properties and the π-complexation with a mercury trifunctional lewis acid are expected to enhance the phosphorescence in the presence of the heavy metal due to the spin-orbit coupling. Besides, owing to the presence of heavy metal atom in the Au (I) complexes linked by s-bonded triethynyltriphenylene luminophore, the phosphorescence occurs from a metal-centered emission. The conjugated organic luminophores have been developed to produce excellent quantum efficiencies, brightness, and long lifetimes.

>Magister Scientiae - MSc / Magnetic luminescent nanoparticles of an iron oxide (Fe₃O₄) superparamagnetic core and an indium phosphide/zinc selenide (InP/ZnSe) quantum dot shell are reported. The magnetic nanoparticles (MNP’s) and quantum dots (QD’s) were each synthesized separately before conjugation. The MNP’s were functionalized with a thiol-group allowing the QD shell to bind to the surface of the MNP by the formation of a thiol-metal bond. The nanocomposite was capped with 3-mercaptopropionic acid, 1-propanethiol, 2-methyl-1-propanethiol and their properties investigated using the characterization techniques: high- resolution transmission electron microscopy (HR-TEM), energy-dispersive spectroscopy (EDS), UV-vis, scanning electron microscopy (SEM), superconducting quantum interference device (SQUID), and photoluminescence. These techniques yielded significant information on particle size, morphology, dispersion, and chemical composition including luminescence and florescence.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-08-01T14:57:13Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação com a Data.pdf: 5044606 bytes, checksum: c09a234cd8ad3e6e1590e833910723e3 (MD5) / Made available in DSpace on 2017-08-01T14:57:13Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação com a Data.pdf: 5044606 bytes, checksum: c09a234cd8ad3e6e1590e833910723e3 (MD5) Previous issue date: 2017-03-28 / CNPQ / Inicialmente confirmamos a intensificação da luminescência em complexos de európio com ligantes não-iônicos mistos do tipo Eu(DBM)3(L, L’), onde DBM (1,3-difenilpropano-1,3diona) é o ligante iônico do tipo β-dicetonato e L são ligantes não-iônicos (DBSO (dibenzil sulfóxido), PTSO (ρ-toluil sulfóxido) e TPPO (óxido de trifenilfosfina)), quando comparados com complexos muito conhecidos do tipo Eu(DBM)3(L)2. A rota empregada no laboratório foi a partir da mesma metodologia de outros exemplos semelhantes de complexos mistos. Os rendimentos obtidos de cada etapa ficaram na faixa de 51-70%. Também, comprovamos experimentalmente que existe uma ordem ligantoquímica para os ligantes não-iônicos: TPPO>PTSO>DBSO>H2O. Esses dados foram corroborados a partir de cálculos teóricos do software MOPAC utilizando o modelo RM1 orbitais. As medidas de Arad obtidas para estes complexos fizeram a previsão da mesma conjectura usada anteriormente pelo nosso grupo de pesquisa: que o aumento da luminescência está relacionado com o aumento da assimetria dos complexos mistos sintetizados. Além disso, desenvolvemos uma nova metodologia de síntese, que denominamos síntese rápida (SR), para complexos do tipo Eu(β-dic)3(L)2 com diminuição no tempo de obtenção dos complexos puros (diminuição em 50% na média global) e aumento nos rendimentos globais de reação (aumento de 27% na média global). Este procedimento baseia-se na ordem de adição invertida dos ligantes (primeiramente não-iônicos e em seguida os iônicos) em relação à rota usualmente empregada na literatura. Sintetizamos também complexos de európio com ligantes iônicos mistos do tipo Eu(β’, β’’, β’’’)(TPPO)2 para comprovar que a assimetria de complexos com a utilização de ligantes iônicos também intensifica a luminescência. Os dados da luminescência obtidos comprovaram. Aperfeiçoamos a rota sintética anterior (SR) e aplicamos esta nova rota em complexos de európio que contêm ligantes iônicos mistos, realizando-a integralmente no balão de reação via One Pot. Isso proporcionou um menor tempo de reação, melhores rendimentos globais e redução na quantidade utilizada dos reagentes de partida. Foi possível também observar o efeito da triboluminescência em complexos mistos. Os complexos intermediários e finais obtidos foram caracterizados por Espectroscopia de Infravermelho, Espectroscopia de Ressonância Magnética Nuclear (RMN) de 1H, Espectroscopia de RMN de 19F, Espectroscopia de RMN de 31P, Espectrometria de Massas MALDI-TOF e Análise Elementar. Por fim, apresentamos rotas eficientes de sintetizar e de intensificar a luminescência em complexos de európio para várias aplicações em ciência dos materiais. / Initially we confirmed that the intensification of the luminescence of mixed europium complexes of the type Eu(DBM)3(L,L’), where DBM (1,3-diphenylpropane-1,3-dione) is the ionic ligand and L or L’ are the non-ionic ligands: DBSO (dibenzyl sulphoxide), PTSO (ptolyl sulphoxide) and TPPO (triphenylphosphine oxide) when compared with known complexes of the type Eu(DBM)3(L)2. They were all synthesized by the same synthetic route mostly used in the literature. The reaction yields obtained ranged from 51% to 70%. It is important to mention that it was experimentally proved that there is a chemical bond order for the non-ionic ligand to attach to the central atom, as follows: TPPO>PTSO>DBSO>H2O. In addition, theoretical calculations performed with the MOPAC software, using the RMI orbitals model comproved this same behavior. Another interesting result that we achieved was concerning the Arad data obtained from these mixed europium complexes, they were able to predict the same conjecture used previously and it was in agreement to the quantum yield data determined for the other mixed L,L’ complexes: luminescence increasesment can be directly related to the assymmetry of the ligands in the europium mixed complex. Furthermore, we developed a new synthetic route named Fast Synthesis (FS), to obtain complexes of the type Eu(β-dic)3(L)2. The application of this methodology brought great advantages: significant decrease in reaction time to obtain the pure complexes (in average 50% decrease in reaction time); increase the global reaction yield (in average 27% of reaction yield increase). This synthetic procedure is based on the inverted order of addition of the ligands to the coordination atom or else, firstly the non-ionic ligands are added, followed by the ionic ones when compared to the synthetic route commonly employed by the inorganic chemists. Using the FS methodology we prepared assymmetric europium complexes coordinated with different ionic ligands like, Eu(β’, β’’, β’’’)(TPPO)2, envisaging to comprove that structure assymmetry enhances luminescence. The data of quantum efficiency obtained were in accodance with previous luminescence results. Another important step was introduced to improve our FS route in obtaining europium complexes with mixed ionic ligands, this time performing the experiment via One Pot procedure. The results of the synthesis One Pot was astonishing: much less reaction time, much better yields and pronounced reduction on initial reagents quantities. Unexpectedly, it was possible to observe the triboluminencence phenomenon, when crystals of the complex Eu(DBM,BTFA,TTA)TPPO2 were frictioned with a spatula and luminescent glares of light appeared. All the complex intermediates and final ones had their structures characterized by IR Spectroscopy, NMR Spectroscopy of 1H, 19F and 31P; Mass Spectrometry MALDI-TOF and Elemental Analysis. To conclude, we have developed two new synthetic routes, synthesized 23 new complexes, including a new class of luminescente europium complexes of the type Eu(β’, β’’, β’’’)(TPPO)2 , opening a new branch for application on Science of Materials.