Letteratura scientifica selezionata sul tema "Particule phosphorescente"

Photoluminescence is known to have huge potential for applications in studying biological systems. In that respect, phosphorescent dye molecules open the possibility to study the local slow solvent dynamics close to hard and soft surfaces and interfaces using the triplet state (TSD: triplet state solvation dynamics). However, for that purpose, probe molecules with efficient phosphorescence features are required with a fixed location on the surface. In this article, a potential TSD probe is presented in the form of a nanocomposite: we synthesize spherical silica particles with 2-naphthalene methanol molecules attached to the surface with a predefined surface density. The synthesis procedure is described in detail, and the obtained materials are characterized employing transmission electron microscopy imaging, Raman, and X-ray photoelectron spectroscopy. Finally, TSD experiments are carried out in order to confirm the phosphorescence properties of the obtained materials and the route to develop phosphorescent sensors at silica surfaces based on the presented results is discussed.

Organic room temperature phosphorescent (ORTP) materials with stimuli-responsive, multicomponent emissive behaviour are extremely desirable for various applications. The derivative of cyclic triimidazole (TT) functionalized with an ethynyl group, TT-CCH, is isolated and investigated. The compound possesses crystallization-enhanced emission (CEE) comprising dual fluorescence and dual phosphorescence of both molecular and supramolecular origin with aggregation-induced components highly sensitive to grinding. The mechanisms involved in the emissions have been disclosed thanks to combined structural, spectroscopic and computational investigations. In particular, strong CH⋯N hydrogen bonds are deemed responsible, for the first time in the TT family, together with frequently observed π⋯π stacking interactions, for the aggregated fluorescence and phosphorescence.

An innovative phosphorescence probe based on Mn-doped ZnS quantum dots (Mn:ZnS QDs) was developed for selective detection of chloramphenicol (CAP) via inner-filter effect (IFE). Mn:ZnS QDs were synthesized by water method and modified with L-Cysteine for better stability, and the average diameter of the nanometer particle was 3.8[Formula: see text]nm. With the excitation wavelength at 289[Formula: see text]nm, the strong phosphorescence of Mn:ZnS QDs can be emitted at 583[Formula: see text]nm. The excitation spectrum of Mn:ZnS QDs was substantially overlapped with the absorption spectrum of the target CAP. The excited light of Mn:ZnS QDs can be absorbed partially by CAP when they coexist, the phosphorescence intensity decreased with the increasing concentration of CAP, and it has a good linear relationship. Under optimal conditions, the linear relational concentration range achieved four orders of magnitude from 25 to [Formula: see text] ([Formula: see text]), with a detection limit (LOD; [Formula: see text]) down to 0.81[Formula: see text][Formula: see text]. The simple, rapid and low cost IFE phosphorescent probe exhibited satisfactory recoveries ranging from 88.9% to 98.5% for CAP analysis in spiked honey, which shows a potential for routine screening of CAP in ensuring the food safety.

Nonaqueous dispersions of poly(methyl methacrylate) (PMMA) particles, sterically stabilized with polyisobutylene (PIB), were prepared with naphthalene (N) groups covalently incorporated into the PMMA chains. These materials have a complex morphology of phase-separated PMMA and PIB microdomains, with the N groups in the PMMA microphases. The phosphorescence intensity and decay times of the N groups were measured as a function of temperature over the range 77–295 K for dispersions in methylcyclohexane and for freeze-dried powder samples. An Arrhenius treatment of the radiationlcss decay rate showed a change in slope at −35 °C. The activation energy for the radiationless decay process is 3.8 kcal/mol in the −35 – +22 °C temperature region, identical to that found for pure PMMA by nmr for chain motion associated with the a-methyl relaxation process. We believe that the phosphorescence experiment is sensitive to the diffusion of oxygen and other impurities in the sample. These rates increase as the temperature is raised, enhancing the rate of phosphorescence quenching. These experiments indicate that phosphorescence measurements on labelled samples are suitable for studying relaxation processes within individual microphases of a polyphasic composite material.

Fluorescence and phosphorescence quantum yields and fluorescence and phosphorescence lifetimes were obtained for 4-phenylphenol adsorbed on filter paper with either NaCl, NaBr, or Nal at 296 and 93 K. From these data several photophysical parameters were calculated and compared. In general, the photophysical data showed that the heavy-atom effect was operative, with NaI showing the greatest effect. However, NaBr at 93 K showed both the heavy-atom effect and another effect which was particular to NaBr. For 4-phenylphenol with NaI, very little increase occurred for the phosphorescence quantum yield from 296 to 93 K, which indicated that almost maximum phosphorescence quantum yield was achieved at room temperature for 4-phenylphenol with NaI present. The increase in phosphorescence lifetime for 4-phenylphenol from room temperature to low temperature was shown to be related to the increase in the Young's modulus of filter paper as the temperature was lowered. Calculated phosphorescence lifetimes at room temperature and at low temperature with equations that included Young's modulus values agreed very well with experimental lifetime values.

Fluorescent textile products are manifold used. Compared to fluorescent textiles, phosphorescent textile products exhibit an afterglow effect even after the illumination is stopped. Phosphorescent textiles are less present as commercial products on the market. With this background the aim of the actual presentation is to investigate the properties of commercially available phosphorescent textile materials. Investigations are performed by illumination under different light arrangement. Microscopy is performed by scanning electronic microscopy (SEM) and advanced light microscopy using UV light. Light emission of the samples is recorded by fluorescence spectroscopy. The chemical composition is determined by using electron dispersive spectroscopy (EDS). Depending on the type of sample, an afterglow effect can be determined up to 5 to 30 minutes after stopping the illumination with UV light. By SEM and EDS methods it is observed that the phosphorescent effects are realized by application of phosphorescent pigments, which can be best described as phosphorescent micromaterials. Depending on the product category, two different types of phosphorescent materials are used – doped strontium aluminates (SrAl2O4) and zinc sulfide (ZnS). Products based on doped strontium aluminates exhibit longer afterglow effects compared to products with ZnS pigments. However, the use of doped strontium aluminate is quite surprising for a commercial textile product, because of cost reasons. Finally, it can be stated that phosphorescent micromaterials are established materials for realization of functional textile products. These micromaterials can be found in every day products and are examples for innovative particle technology used in commercial consumer products.

Ce projet de recherche de doctorant concerne l’élaboration et l’utilisation de matériaux multifonctionnels imprimable, en mettant l’accent sur les compromis entre propriétés matériaux et spécification applicative, avec un focus autour des fonctions de chauffage par effet joule et d’électroluminescence. L’originalité des travaux repose sur une approche couplée entre matériaux multifonctionnels et intégration textile. Le premier point de l’étude concerne la sélection des matériaux multifonctionnels jugés comme potentiellement intéressants pour la création de textiles intelligents adaptés aux secteurs cibles de la société TESCA-groupe. Cette sélection impliquait la caractérisation des propriétés électriques et thermiques des matériaux conducteurs ainsi que du substrat textile. De plus, des analyses à l'aide d'appareils de microscopie électronique à balayage (MEB)/ spectroscopie à dispersion d'énergie (EDS) et diffraction de rayon X (DRX) étaient effectuées pour étudier la microstructure, notamment l'adhérence, l'épaisseur des couches déposées et la composition chimique des matériaux. Le second aspect met l’accent sur une étude du vieillissement accéléré sur des éprouvettes unitaires des substrats textiles revêtus d'encre conductrice, en conformité avec les spécifications requises de la société Tesca. L'objectif de cette démarche était d'identifier les limites inhérentes à chaque matériau, telles que la déformation maximale, les variations de température, l'adhérence, la compatibilité des processus, etc., dans le but de proposer des axes d'optimisation ou de tenir compte de ces limitations lors de la conception des transducteurs intégrés sur substrat textile. Cette première étape nous permettait d'établir une base de matériaux multifonctionnels pouvant être utilisés pour des applications spécifiques, telles que les nappes chauffantes, les interrupteurs capacitifs ou résistifs, les transducteurs, les capteurs de grandeurs mécaniques, entre autres. Le troisième volet de cette recherche consistait à assembler ces éléments de base pour créer des sous-fonctions qualifiées d’intelligente. En effet, la réalisation de transducteurs impliquait généralement la combinaison de différents matériaux multifonctionnels afin de répondre aux exigences spécifiques de l'application visée
This PhD student research project concerns the development and use of printable multifunctional materials, focusing on the trade-offs between material properties and application specification, with a particular emphasis on joule heating and electroluminescence functions. The originality of the work lies in a coupled approach between multifunctional materials and textile integration. The first part of the study concerned the selection of multifunctional materials deemed potentially interesting for the creation of intelligent textiles adapted to TESCA-groupe's target sectors. This involved characterizing the electrical and thermal properties of both the conductive materials and the textile substrate. In addition, analyses using scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were carried out to study the microstructure, including adhesion, the thickness of the deposited layers and the chemical composition of the materials. The second aspect focused on an accelerated ageing study on unit specimens of textile substrates coated with conductive ink, in compliance with the specifications required by Tesca. The aim of this approach was to identify the inherent limitations of each material, such as maximum deformation, temperature variations, adhesion, process compatibility, etc., with a view to proposing areas for optimization or taking these limitations into account when designing transducers integrated on textile substrates. This first step enabled us to establish a base of multifunctional materials that could be used for specific applications, such as heating mats, capacitive or resistive switches, transducers, sensors for mechanical quantities, among others. The third aspect of this research consisted in assembling these basic elements to create sub-functions described as "intelligent". In fact, the production of transducers generally involved combining different multifunctional materials to meet the specific requirements of the target application

A technique for measuring fluid velocities by means of neutrally-buoyant, phophorescent particles was investigated in a small-scale water jet facility. A nitrogen laser briefly illuminated the flow, exciting only those particles resident within the pulsed beam. The particles luminesce for a short while following excitation, during which time they also move with the flow. This creates a visible particle streak, the intensity of which decays along the direction of motion. A strobe illuminates the particles again a known time following the laser pulse. The magnitude and direction of a particle's velocity in the plane of view are deduced from an image of it streak captured by a video camera and recorded by a digital image processing system.

Cette thèse se concentre sur la synthèse et l’analyse photophysique de complexes de Pt(II) luminescents and leur assemblage après agrégation. Multiples motifs supramoléculaires ont été utilisé pour acquérir un contrôle sur l’assemblage de ces complexes plan-carrés.Des ossatures de type couronne-éther furent attachés à des complexes métalliques phosphorescents pour donner un bouton supramoléculaire qui peut être actionné par des cations potassium. De plus, l’altération de l’arrangement de l’empilage des Pt(II) après coordination d’un ligand fut exploité pour la réalisation d’un senseur chimique qui peut être utilisé pour la détection différentielle d’aza-hétérocylces. Par ailleurs, l’installation d’un motif pont hydrogène à un complexe de Pt(II) luminescent fut établie, donnant un composé ayant un organisation 2D sur graphène. Finalement, des complexes de Pt(II) amphiphiles qui s’auto-assemblent en solution aqueuse dans des agrégats hautement luminescents furent synthétisés. La série de complexes soluble dans l’eau, chargés négativement ou neutres furent caractérisés par rapport à leurs paramètres photophysiques et leurs interactions avec des protéines capsides virales
The presented thesis focused on the synthesis and photophysical investigation of luminescent Pt(II) complexes and their resulting assemblies that form upon aggregation. Multiple supramolecular motifs were utilized in order to gain control over the assembling behavior of the square-planar complexes. Crown-ether scaffolds were tethered with the phosphorescent metal complexes rendering a supramolecular switch that can be triggered by potassium cations. Moreover, alteration of the Pt(II)-stacking arrangement upon ligand coordination was exploited to realize a chemosensor that can be employed for of differential detection of aza-heterocycles. Furthermore, the installation of a H-bond motif to a luminescent Pt(II) complex was established, which resulted in a compound forming a two-dimensional organization on graphene. Finally, amphiphilic Pt(II) complexes were synthesized that self-assemble into highly luminescent aggregates in aqueous solutions. The series of water soluble neutral and negatively charged metal complexes were characterized with respect to their photophysical parameters and their interactions with virus coat proteins

Ce travail porte sur la stabilisation de flammes prémélangées et swirlées de mélanges combustibles méthane/hydrogène/air avec différents taux de dilution d’azote et de dioxyde de carbone. Une tige centrale permet de stabiliser des flammes pour de faibles nombres de swirl. Le sommet de la flamme interagît éventuellement avec les parois de la chambre de combustion. L’objectif ces travaux est d’améliorer la connaissance des mécanismes qui gouvernent la stabilisation et la topologie de ces flammes. Ces travaux démontrent que le nombre de swirl, la composition du mélange combustible, la géométrie de la chambre de combustion ainsi que les conditions aux limites thermiques ont une grande influence sur la forme prise par la flamme. Le dispositif expérimental permet de modifier la forme et la taille de la chambre de combustion, le diamètre du tube d’injection et le nombre de swirl. Des conditions opératoires propices aux transitions de forme de flamme sont ensuite étudiées pour différentes configurations de brûleur. Une caractérisation expérimentale fouillée d’un point de fonctionnement est réalisée grâce à la Fluorescence Induite par Laser sur le radical Hydroxyle (OH-PLIF), la Vélocimétrie par Images de Particules (PIV) et la Phosphorescence Induite par Laser de phosphores sensibles à la température (LIP). Une base de donnée de l’écoulement et des conditions aux limites associées est obtenue sans et avec combustion. Les mécanismes qui contrôlent les transitions de formes de flamme sont ensuite analysés lorsque la flamme interagit avec les parois de la chambre de combustion. L’influence de la composition du mélange combustible, de la vitesse débitante et du nombre de swirl est caractérisée et il est démontré que la transition d’une flamme en V vers une flamme en M est déclenchée par un retour de flamme dans la couche limite le long d’une des parois latérales de la chambre de combustion. Les nombres sans dimension contrôlant ces transitions sont identifiés et un modèle de prévision de la forme de ces flammes est développé. La physique déterminant les transitions de forme de flammes est différente lorsque celles-ci n’interagissent pas avec les parois de la chambre de combustion. En utilisant le signal de chimiluminescence OH* et la OH-PLIF, il est montré que la teneur en hydrogène dans le combustible a une grande influence sur la forme de flamme. L’utilisation de la LIP et de thermocouples a également permis de montrer que les conditions aux limites thermiques jouent un rôle prépondérant sur la forme de flamme. Les effets combinés de l’étirement et des pertes thermiques sont examinés par l’utilisation conjointe de la PIV et de la OH-PLIF. Il est montré que les limites d’extinction de flammes pauvres prémélangées sont réduites par les pertes thermiques et que la transition d’une flamme en M vers une flamme en V est consécutive à l’extinction du front de flamme situé dans la couche de cisaillement externe du jet soumis à un étirement trop important. Ces expériences sont complétées par une analyse de la dynamique de ces flammes. Des modulations de la vitesse débitante à basse fréquence et à haute amplitude modifient la forme de flamme. La stabilisation de flammes CH4/H2/air diluées par du N2 ou du CO2 est finalement examinée. La zone de recirculation produite par la tige centrale permet d’alimenter la base de la flamme avec des gaz brûlés chauds et de stabiliser des flammes fortement diluées. Augmenter la fraction molaire de diluant dans le combustible réduit l’intensité de lumière émise par le radical OH*. Il est également montré que la composition du diluant a un impact sur le champ de température des gaz brûlés et des surfaces de la chambre de combustion. La dilution par du CO2 augmente les pertes thermiques par rayonnement des gaz brûlés. Cela réduit l’efficacité de la chambre de combustion équipée de quatre parois transparentes. [...]
This work deals with the stabilization of premixed turbulent swirling flames of methane/hydrogen/air combustible mixtures with different dilution rates of nitrogen and carbon dioxide. A central bluff body helps stabilizing the flames at low swirl numbers. The flame tip eventually impinges the combustor peripheral wall. The general objective is to gain understanding of the mechanisms governing the stabilization and the topology of these flames. It is found that the swirl number, the combustible mixture composition, the geometry of the combustor, and the thermal boundary conditions have a strong impact on the shape taken by these flames. The experimental setup used to characterize flames topologies is first described. Flames prone to topology bifurcations are selected and are studied for different arrangement of the combustor when the combustion chamber shape and size, the injection tube diameter, and swirl number are varied. One operating condition is fully characterized under non-reactive and reactive conditions using Planar Hydroxyl Laser Induced Fluorescence (OH-PLIF), Particle Imaging Velocimetry (PIV), and Laser Induced Phosphorescence of thermographic phosphors (LIP) to generate a detailed database of the flow and the corresponding boundary conditions. An analysis is then conducted to understand the mechanisms controlling shape bifurcations when the flame interacts with the combustor peripheral wall. Effects of the combustible mixture composition, the bulk flow velocity, and the swirl number are analyzed. It is shown that the transition from a V to an M flame is triggered by a flashback of the V flame tip in the boundary layer of the combustor peripheral wall. Dimensionless numbers controlling these transitions are identified and a simplified model is developed to help the prediction of the flame shapes. The physics of these shape bifurcations differs when the flame does not interact with the combustor wall. The large influence of the hydrogen enrichment in the fuel on the flame shape is analyzed using flame chemiluminescence and OH-PLIF. LIP and thermocouple measurements demonstrate that the thermal boundary conditions still have a strong impact on the flame topology. The combined effects of strain and heat losses are investigated using joint OH-PLIF and PIV experiments. It is shown that flammability limits of premixed flames are reduced due to heat losses and the transitions from M to V shaped flames is consecutive to localized extinctions of flame front elements located in the outer shear layer of the jet flow that are submitted to large strain rates. These experiments are completed by an analysis of the dynamics of methane/hydrogen/air flames. It is shown that low frequency and high amplitude velocity modulations generated by a loudspeaker alter the shape taken by these flames. The stabilization of methane/hydrogen/air flames diluted by nitrogen and carbon dioxide is finally examined. It was possible to stabilize swirled flames featuring important dilution rates due to the presence of the bluff body, installed on the axis of the injection tube. The recirculation zone behind this element supplies hot burnt gases to the flame anchoring point. Using OH* chemiluminescence imaging, it is shown than increasing the molar fraction of diluent in the fuel reduces the light emission from excited OH* radicals. The influence of dilution on the flame chemistry is emphasized with experiments conducted at a fixed thermal power and fixed adiabatic flame temperature. It is also demonstrated that the composition of the diluent has a strong influence on the temperature field of the burnt gases and of the combustor wall surfaces. Dilution with carbon dioxide increases radiative heat losses from the burnt gases in comparison to dilution with nitrogen. This penalizes the combustor efficiency equipped with four transparent quartz walls. [...]

L'objectif de cette thèse est le développement d’une nouvelle technique expérimentale de détermination de la distribution des temps de séjour (DTS) des particules solides dans les enceintes de manutention et de transformation de solides particulaires ainsi que le développement d’un modèle. Dans un premier temps, une nouvelle méthode optique a été développée pour mesurer la DTS des particules. Les expériences sont réalisées avec le carbure de silicium (SiC) et le pigment phosphorescent (Lumilux® Green SN-F50 WS) a été utilisé en tant que traceur. Une étude expérimentale préliminaire a été réalisée dans un lit fluidisé bouillonnant simple afin de valider la méthodologie proposée de mesure de la DTS. Dans un deuxième temps, la technique développée de la mesure de concentration a été appliquée à la détermination de la DTS dans un lit fluidisé profond. Les courbes de la DTS des particules sont déterminées expérimentalement dans différentes conditions opératoires. Dans un troisième temps, un modèle basé sur une combinaison de réacteurs idéaux est proposé pour prédire la DTS des particules du lit fluidisé étudié. Les valeurs de sortie prédites sont ensuite comparées aux données expérimentales pour l’ajustement du modèle
The aim of the present thesis is to develop a novel experimental technique for determining the residence time distribution (RTD) of solid particles in solid unit operations as well as model development. Initially, a novel optical method was developed to measure the particle RTD. Experiments are carried out with Silicon Carbide (SiC) and the pigment phosphorescent (Lumilux® Green SN-F50 WS) as tracer particle. A preliminary experimental study was conducted in a simple bubbling fluidized bed in order to validate the proposed RTD measurement methodology. In the second step, the developed technique of the concentration measurement was applied to measure the RTD of a deep fluidized bed. The particle RTD curves are determined experimentally in different operating conditions. Finally, a model consisting of the combination of the ideal reactors is proposed to predict the particle residence time distribution in the studied fluidized bed. The predicted output values are then compared with the experimental data to establish a good model fitting data

This thesis reports on the development and application of a new method for the measurement of particles transported within a moving fluid and subjected to high fluxes of radiant heating. The comprehensive understanding of heat transfer in particle-laden flows is important as it is a key factor in enabling optimisation of various industrial and scientific applications such as combustion, mineral processing plants, and pharmaceutical manufacturing, as well as aid in the development of new technologies based on the two-phase flow. However, one of the major factors that limits the furtherance of understanding of the field is the difficulty in measuring temperatures of moving, micron-sized particles. Previously, most publications on heat transfer in particle-laden flows focus on gas temperature measurements, where the temperatures of particles are inferred through fundamental heat transfer equations. However, this technique is not applicable in systems where a large disparity exist between the gas and particle temperatures, and does not take into account inter-particle relationships which could have a significant effect on the overall heat transfer where the interparticle spacing is sufficiently low. In order to distinguish between the particle and gas phase temperatures, a radiative heat source capable of delivering continuous heat fluxes of up to 36.6MW/m2 in the form of a Solid-State Solar Thermal Simulator (SSSTS) was used throughout this dissertation. This is because the SSSTS operates at a wavelength of 910nm, which is only absorbed by the particle phase and not the gas phase. Importantly, the operation of the SSSTS at this wavelength does not interfere with the excitation signal (355nm) used in the LIP technique. However, the performance of the SSSTS is not well understood due to the system being the first of its kind. Chapter 4 of this dissertation addresses this by characterising in detail the SSSSTS. The next part of this dissertation describes the development and application of single-shot, nonintrusive particle temperature measurement techniques based on laser-induced phosphorescence (LIP), a thermometry that makes use of the phosphorescent emission properties of thermophosphors (TPs) governed by the temperature-dependent Boltzmann distribution. Here, ZnO:Zn TPs were selected to be used as they have the highest temperature sensitivity below 625°C. The TPs were suspended in unsteady flow in an optically-accessible fluidised bed and subjected to high radiative heat fluxes of up to 21.1 MW/m2. Two types of thermometry are reported – with Chapter 5 describing the development of an in-situ, areaaveraged, temporally-resolved particle temperature measurement technique by analysing the change in phosphorescent emission spectra of the selected TP with respect to wavelength, collected using a fibre-optic cable connected to a spectrometer; and Chapter 6 detailing a single-shot, planar particle temperature measurement. For the planar thermometry, the phosphorescent emissions of the TPs were collected using a single ICCD camera fitted with an image splitter and two interference filters specifically selected. Each measurement derives from two 15mm × 10.8mm images collected simultaneously to avoid errors associated with timedelays and/or angular distortions. The resultant spatial resolution for each image was 51pixels/mm, with an average of 30 particles recorded within the imaging region. It was demonstrated that the particle temperatures measured with the LIP technique was found to be approximately 44°C higher on average than the gas temperatures measured with a thermocouple in the same system. A strong dependence of heat flux, as well as particle attenuation (mass loading) on particle temperature was also reported. Additionally, a maximum particle temperature rise of 350°C was recorded with a heat flux of 21.1 MW/m2, where the maximum particle residence time in the heating region is 0.05s. The next section of this thesis details the study of application of the developed thermometry technique in a laminar particle-laden jet flow issued from a 12.8mm pipe downwards into a wind tunnel and the particles radiatively heated by the SSSTS. The measured data were analysed by comparison with the results from a simple first-order analytical model that considers the radiative heating, convective cooling, radiative heat loss and heat gain of a single particle. It was found that heat flux, particle concentration and to a lesser extent, particle diameter all affect particle temperatures. At low heat fluxes, 𝑄̇𝑟𝑎𝑑 ≤ 6.1 MW/m2, particle concentrations and temperatures were found to be higher in jet edge, consistent with previous investigations. At heat fluxes above that, where 𝑄̇𝑟𝑎𝑑 > 6.1 MW/m2, thermophoresis was observed, as evidenced by the migration of the smaller particles to the jet edge where the local temperature is lower. The effect of buoyancy was also observed at 𝑄̇𝑟𝑎𝑑 ≥ 20.6 MW/m2, as evidenced by two distinct regions of high particle temperatures upstream from the heating region (one at the jet axis, and one at the jet edge). These results were presented in Chapter 7 of the present dissertation.
Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2020

This chapter introduces the design and fundamental concepts of organic light emitting diodes (OLEDs) and organic semiconductor lasers (OSLs). The chapter begins by describing device architectures used in fluorescent, phosphorescent, and thermally assisted delayed fluorescent (TADF) devices. Device characterization for both white and monochromatic OLEDs with application to displays and white illumination sources is discussed. OLED displays are compared with liquid crystal displays, and quantification of perceived color and luminosity is described. Materials and layer structures leading to high efficiency even at high brightness where exciton annihilation dominates, is followed by a discussion of methods used to efficiently outcouple light from substrate, waveguide, and surface plasmon modes. A discussion of reliability, with particular emphasis of the relatively short operational lifetime of blue phosphorescent and TADF devices, is provided. The last section is devoted to optically pumped OSLs, along with limitations encountered in achieving electrically pumped organic laser diodes.

We report recent progresses made in development of novel molecule-based flow diagnostic techniques, named as Molecular Tagging techniques, to achieve simultaneous measurements of multiple important flow variables (such as flow velocity and temperature) for micro-flows and micro-scale heat transfer studies. Instead of using tiny particles, specially-designed phosphorescent molecules, which can be turned into long-lasting glowing molecules upon excitation by photons of appropriate wavelength, are used as tracers for both velocity and temperature measurements. A pulsed laser is used to “tag” the tracer molecules in the regions of interest, and the movements of the tagged molecules are imaged at two successive times within the photoluminescence lifetime of the tracer molecules. The measured Lagrangian displacement of the tagged molecules between the two image acquisitions provides the estimate of the fluid velocity vector. The simultaneous temperature measurement is achieved by taking advantage of the temperature dependence of phosphorescence lifetime, which is estimated from the intensity ratio of the tagged molecules in the two images. The implementation and application of the MTV&T technique are demonstrated by conducting simultaneous velocity and temperature measurements to qunatify the transient behavior of electroosmotic flow (EOF) inside a microchannel and to reveal the unsteady heat transfer, mass transfer and phase changing process inside micro-sized water droplets pertinent to wind turbine icing phenomena.

Phosphorescence has been applied to measure the temperature. The intensity and the lifetime of phosphor depend on the temperature due to the quenching effect of the phosphor. In the present study, the temperature sensitive particles (TSParticles) with metal complex, phosphor molecules, were synthesized. TSParticles can be also particles for the particle image velocimetry. The particles were illuminated by a pulse laser at 20Hz. A high speed camera was applied to record 30 particle images at intervals of 25∼50 micro seconds (20∼40kHz) for each excitation laser pulse. From each series of images the velocity/temperature field was calculated. The TSParticle technique was applied to measure the velocity/temperature distribution of a water flow in a wire-wrapped rod bundle system, which briefly simulated the fuel rods system in FBR. The working fluid was water and the aim of this study was to contribute to an estimation and a certification of results of numerical simulation for the safety design of the FBR.

This paper describes the development of the Planar Laser-Induced Phosphorescence (PLIP) technique for mapping the fuel temperature and concentration distributions in a jet-in-cross-flow (JICF) spray study. The spray was produced by injecting cold liquid Jet-A into hot cross-flowing air. The application of PLIP required the seeding of liquid fuel with micron-size thermographic phosphor particles before injection. The resulting spray produced phosphorescence and droplets Mie-scattering signals when illuminated by a 355nm planar UV laser sheet of 0.054J/pulse energy. The technique was investigated as a potential alternative to the use of Jet-A Planar Laser-Induced Fluorescence (PLIF) for the mapping of fuel concentration in sprays, because the low signal intensity of Jet-A’s fluorescence at high T prevents the use of the PLIF approach. In contrast, PLIP provides a strong signal at high T, and allows the simultaneous determination of local T and fuel concentration when two spectral bands of the phosphorescence emission are imaged and their ratio-of-intensities (RI) determined. In addition, the locations where liquid fuel droplets exist were imaged from the UV Mie-scattering of the laser-sheet (which can also be done in PLIF). In the present investigation, an optical system that imaged two spectral bands of phosphorescence and one wavelength of Mie-scattering was developed. It consisted of three CCD cameras with dichroic beam-splitters and interference narrow bandpass filters. The spray-pattern within a span of ∼80×30 orifice diameters was captured, with spatial resolution of about 0.1mm/px. The investigated jet-in-cross-flow spray was produced by injecting Jet-A fuel from a 0.671mm diameter orifice located on the wall of a rectangular channel (25.4×31.75mm cross-section). The cross-flow air was preheated to temperatures encountered in modern gas turbines (up to 480°C), while the temperature of the injected Jet-A fuel was in the T = 27–80°C range. YVO4:Eu phosphor particles with a median size of 1.8 microns were used to seed the fuel. Since the emissions of the commonly used Dy:YAG thermographic phosphor were found to be too weak and had wavelengths that overlapped with Jet-A fluorescence signals, YVO4:Eu was used for the JICF studies instead. It was observed that while the emissions of YVO4:Eu were stronger than Dy:YAG, the range of T where it can be applied in the PLIP technique was more limited — just sufficient for the investigated JICF. Preliminary results from the study showed rapid changes in fuel concentration and T from the injector up to z/dinj∼30 for momentum ratios of J = 5, 10 and 20, followed by a more gradual mixing/heat-up downstream. It was also found that deposition of phosphor particles on channel-walls interfered with the spray characterization, reducing the accuracy of the measurements.

Abstract Molecular Tagging Velocimetry (MTV) has been applied to quantify velocity fields associated with convective phenomena which occur during solidification in aqueous ammonium chloride solution (NH4Cl-H2O), a popular transparent low-temperature analog of metal alloys. A phosphorescent line pattern was “written” into the melt to quantify one component of the velocity field within a plume and in the fluid surrounding the plume. These results represent the first quantitative, continuous field measurements of velocity for such studies. The data compare well with the magnitude of the maximum plume velocities estimated in the literature using particle tracking methods. Asymmetric and symmetric plume velocity profiles were quantified. Velocity fields associated with downward flowing sheaths of fluid surrounding the plume were quantified. Although the shape of the velocity profile measured using MTV compares reasonably well with that predicted by an analytical model proposed in the literature, significant differences were detected. The extension of the MTV method using a tagged plane, rather than a tagged line of phosphorescent fluid, for qualitative 3-D dynamic, visualization is described. This realization of the MTV method has the potential for revealing the basic three-dimensional structure of the velocity field. The results presented here demonstrate that it is feasible to apply MTV as an advanced diagnostic measurement method to further improve our knowledge of convective phenomena which occur during solidification.

Abstract Innovative low-carbon aero-engines rely on ultra-compact and high energy density combustors, increasing the thermal loads of the walls. This study aims at experimentally enhancing the understanding of the interrelated physical processes between a flame, a wall and a cooling technology. The test rig operates at atmospheric pressure and generates a methane/air turbulent flame interacting with a wall that is air-cooled by means of a splash cooling plate device. Optical diagnostics are simultaneously implemented, including reactive particle image velocimetry (PIV) to assess the flow field, planar laser induced fluorescence on the OH radical (OH-PLIF) to study the flame structure, and laser induced phosphorescence to measure the wall temperature in contact with the reactive flow. Results show that the mean flame location is shifted away from the wall as the blowing ratio is increased. The wall temperature reveals that to enhance cooling efficiency, blowing ratio and flame location must not be considered without each other. Eventually, a classical flame-wall interaction process is retrieved when the blowing ratio is small, whereas flame strain, originating from the aerodynamic shear layer, pilots the flame dynamics for large blowing ratios.