Le multiplexage optique basé sur des nanoparticules offre de nombreux avantages pour la biodétection et l'imagerie à multiparamètres. Toutefois, les modifications apportées à un paramètre entraînent également la modification d’autres paramètres. Par conséquent, la couleur, la durée de vie ou l’intensité ne peuvent pas être utilisées, respectivement, comme paramètre indépendant. Cette thèse peut être divisée en deux aspects. Le premier concerne le développement d'un multiplexage à une seule nanoparticule avec un temps résolu, basé sur le transfert d'énergie par résonance de type Förster (FRET) des complexes de lanthanides aux points quantiques (QD) et ensuite aux colorants fluorescents. Une investigation systématique de toutes les différentes combinaisons avec une large gamme de donneurs et d'accepteurs sur le QD est présentée, et les résultats expérimentaux sont comparés à la modélisation théorique. Le résultat ne contribue pas seulement à une compréhension complète de ces voies de transfert d'énergie compliquée entre multi donneurs / accepteurs sur des nanoparticules, mais offre également la possibilité d'utiliser les modèles pour développer de nouvelles stratégies permettant de préparer le QD avec une couleur, une durée de vie et une intensité réglables de manière indépendante. Le deuxième aspect porte sur le mécanisme de transfert d'énergie du Tb à la nanoparticule d'or (AuNP). Le transfert d'énergie par nanosurface (NSET) s'est révélé être un mécanisme opérationnel pour l'extinction des PL par les AuNP, une information importante pour le développement, la caractérisation et l'application de nanobiocapteurs basés sur l'extinction des PL par les AuNP. / Optical multiplexing based on nanoparticles provides many advantages for multiparameter biosensing and imaging. However, the changes in one parameter also lead to changing of other parameters, and thus, color, lifetime, or intensity could not be used as an independent parameter, respectively. This thesis can be divided into two aspects. The first one focuses on developing time-resolved single-nanoparticle multiplexing based on Förster resonance energy transfer (FRET) from lanthanide complexes to quantum dot (QD) to fluorescent dyes. Systematical investigation of all different combinations with a broad range of numbers of donors and acceptors on QD are presented, and the experimental results are compared with theoretical modelling. The result do not only contribute to a full understanding of such complicated multi donor-acceptor energy transfer pathways on nanoparticles but also open the opportunity to use the models for developing new strategies to achieve the QD with independent tunable color, lifetime and intensity. The second aspect focuses on the energy transfer mechanism from Tb to gold nanoparticle (AuNP). Nanosurface energy transfer (NSET) proved to be an operational mechanism in PL quenching by AuNPs, which is important information for the development, characterization, and application of nanobiosensors based on PL quenching by AuNPs.

A major limitation of silica-based high-Q microcavities is the lack of functionalities such as gain, plasmonic resonance, and second-order nonlinearity. Silica possesses third order nonlinearity but cannot produce second order nonlinearity, plasmonic resonances, or fluorescence emission. The key to overcome this deficiency is to develop versatile methods that can functionalize the surface of a silica microsphere with appropriate nanomaterials. The goal of this thesis is to present and characterize an electrostatic self-assembly based approach that can incorporate a large number of functional materials onto the surface of a silica resonator with nanoscale control. We consider several types of functional materials: polar ionic self-assembled multilayer (ISAM) films that possess second order nonlinearities, Au nanoparticles (NPs) that support plasmonic resonances, and fluorescent materials such as CdSe/ZnS core/shell QDs. A major part of this thesis is to investigate the relationship between cavity Q factors and the amount of nanomaterials deposited onto the silica microspheres. In particular, we fabricate multiple functional microspheres with different ISAM film thickness and Au NPs density. We find that the Q factors of these microspheres are mainly limited by optical absorption in the case of the ISAM film, and a combination of optical absorption and scattering in the case of the Au NPs. By controlling the number of polymer layers or the NPs density, we can adjust the Q factors of these functional microspheres in the range of 106 to 107. An agreement between theoretical prediction and experimental data was obtained. The results may also be generalized to other functional materials including macromolecules, dyes, and non-spherical plasmonic NPs. We also study the adsorption of Au NPs onto spherical silica surface from quiescent particle suspensions. The surfaces consist of microspheres fabricated from optical fibers and were coated with a polycation, enabling irreversible nanosphere adsorption. Our results fit well with theory, which predicts that particle adsorption rates depend strongly on surface geometry. This is particularly important for plasmonic sensors and other devices fabricated by depositing NPs from suspensions onto surfaces with non-trivial geometries. We use two additional examples to illustrate the potential applications of this approach. First, we explored the possibility of achieving quasi-phase-matching (QPM) in a silica fiber taper coated with nonlinear polymers. Next, we carry out a preliminary investigation of lasing in a silica fiber coated with CdSe/ZnS core/shell quantum dots (QDs). / Ph. D.

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No description available.

Semiconductor colloidal quantum dots have an interesting potential to increase solar cell efficiency, with strong absorption in the infrared region and a tunable band gap. In this work an attempt was made to adopt a manufacturing process for PbS quantum dot solar cells, proven successful at Uppsala University. Two optimizations were investigated and the stability of the quantum dot films was analyzed with regards to three storage conditions, varying oxygen accessibility and light exposure, and measured with UV-Vis spectroscopy and X-ray photoelectron spectroscopy. Functioning solar cells were obtained but with lower performance than the results from Uppsala. Optimizations were partly successful with regards to improved spreading of the EDT solution on the PbS quantum dot film using ethanol and methanol as solvents. No improved cell performance was observed by applying both QD films inside argon atmosphere, as opposed to only the first one. Clear differences in oxidization of the films and loss of iodine ligand could be identified for the different storage conditions, with best stability exhibited by films stored under argon atmosphere. / Kvantprickar av halvledande material har en intressant potential att förbättra solcellers verkningsgrad genom en stark absorption inom de infraröda spektrat och ett justerbart bandgap. I detta arbete gjordes ett försök att återskapa en tillverkningsprocess av kvantprickssolceller av PbS, som visat sig framgångsrik vid Uppsala universitet. Två optimeringar undersöktes och stabiliteten av kvantpricksfilmerna analyserades med avseende på tre förvaringsmiljöer med olika exponering för ljus och syre, och mättes med UV-visspektroskopi samt röntgenfotoelektronspektroskopi. Fullt fungerande solceller framställdes men med en lägre prestanda jämfört med resultaten i Uppsala. Optimeringarna var delvis lyckade gällande spridning av EDTlösningen på kvantpricksfilmen av PbS genom att använda etanol och metanol som lösningsmedel. Ingen förbättrad prestanda observerades hos cellerna genom att applicera båda kvantpricksfilmerna i argonatmosfär, jämfört med endast den första. Tydliga skillnader i oxidation för filmerna samt förluster av jodligand kunde identifieras för de olika förvaringsmiljöerna, med bäst stabilitet uppvisad av filmerna som förvarades i argonatmosfär.

En erhållen gymnasieexamen minskar risken för arbetslöshet, därmed är det viktigt att elever fattar väl genomtänkta gymnasieval för att öka deras möjligheter att erhålla gymnasieexamen. Därmed är det intressant att undersöka elevers upplevelser av gymnasievalsprocessen och möjligheten att fatta väl genomtänkta gymnasieval. Syftet med den här studien är att undersöka elevers upplevda känsla av sammanhang i övergången från grundskolan till gymnasiet i samband med gymnasievalsprocessen. Frågeställningarna för studien är följande: 1) Hur begriplig upplevde eleverna gymnasievalsprocessen? 2) Hur hanterbar upplevde eleverna gymnasievalsprocessen? 3) Hur meningsfull upplevde eleverna gymnasievalsprocessen? Studiens teoretiska utgångspunkt är en integrering av Aaron Antonovskys teori om känsla av sammanhang och DOTS av Law och Watts. Studien använder en kvalitativ metod för insamling och analys av data. Insamlingen skedde genom totalt sju stycken semistrukturerade intervjuer, fyra enskilda och tre parintervjuer. Datan analyseras genom en tematisk innehållsanalys. Studien visar att elever har en begränsad begriplighet av gymnasievalsprocessen då de förstår själva valprocessen och vilka gymnasieprogram som finns men inte programmens djupare innebörd. Eleverna upplever gymnasievalsprocessen som hanterbar genom stöd från familj och vänner samt studie- och yrkesvägledningen i grundskolan. Gymnasiet upplevs som mer meningsfullt än grundskolan och meningsfulla val upplevs kunna fattas trots begränsningar.

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No description available.

Quantum dots are a part of very important our technological future because of their intriguing and useful properties. These properties are different in character from those of the corresponding bulk material. Quantum dots are inorganic artificial semiconductor nanocrystal whose electrons influence their physical and chemical properties. Zinc oxide quantum dots were synthesized through an ethanol based precipitation via colloidal synthesis method at various pH values. Various emission colors were obtained because the excited quantum dots of various sizes emitted specific wavelengths of light. The emission spectra indicated that the pH dependent quantum dots were successfully synthesized. Zinc oxide quantum dots were also encapsulated and the luminescence properties examined. The quantum dots that were immobilized in polyisoprene (PI) through chemiluminescence (CL) analyses were found to be stable and were capable of continuing their luminescence properties with extended uses and long- term storage. Linear calibration curves were acquired for concentration of 8.75 x 10-5 M H2O2 in TCPO-CL.

Quantum dots are semiconductive particles whose properties are highly influenced by the presence of at least one electron. Cadmium selenide quantum dots were synthesized via colloidal synthesis. Contrary to previous preparations, more focus was placed on the temperature rather than the duration of time at which they form. A series of colored solutions were obtained because the excited quantum dots of various sizes emitted specific wavelengths of light. The emission spectra showed that the temperature-dependent quantum dots were successfully synthesized. The quantum dots were also immobilized on various surfaces, and the luminescence properties were examined. The quantum dots that were immobilized in sol-gels through chemiluminescence (CL) analyses were found to be stable and were able to maintain their luminescence properties with extensive uses and long-term storage. Linear calibration curves were obtained for concentrations of hydrogen peroxide from 1.75 x 10-4 M to 1.75 x 10-2 M in TCPO-CL.