On constate une forte demande mondiale d' énergie propre et renouvelable en raison de la consommation rapide des combustibles fossiles non renouvelables et l'effet de serre qui en résulte. Une solution prometteuse pour produire une énergie propre et renouvelable est d'utiliser des cellules solaires pour convertir l' énergie solaire directement en électricité. Comparativement à leurs homologues inorganiques, les cellules solaires organiques (OSCs) sont maintenant intensivement étudiées en raison des avantages tels que le poids léger, la flexibilité, la compatibilité avec les procédés de fabrication à faibles coûts. Malgré ces avantages, l'efficacité de conversion (PCE) des OSCs doit encore être améliorée pour la commercialisation à grande échelle. Les cellules solaires organiques sont réalisées en pile de couches minces comprenant des électrodes, la couche de transport d' électrons, la couche de polymère actif et la couche de transport de trous. Dans cette étude, nous sommes concernés par la couche de PEDOT:PSS qui est couramment utilisée comme une couche tampon entre l'électrode anodique et la couche de polymère actif de cellules solaires organiques. Cette étude vise à intégrer différentes concentrations de nanoprismes (NPSMs) d'argent de taille sub-longueur d'onde dans du PEDOT: PSS afin de profiter de leurs propriétés optiques uniques nées de résonances de plasmons de surface localisées (LSPR) pour améliorer la collecte lumineuse et l'efficacité de génération de charge en optimisant l' absorption et la diffusion de la lumière. Nous avons constaté que les facteurs clés qui contrôlent les performances des cellules solaires plasmoniques comprennent non seulement les propriétés optiques, mais également les propriétés structurelles et électriques des couches hybrides de PEDOT:PSS comprenant des NPSMs d' Ag. D'une part, l'ajout de NPSMs d' Ag conduit ¨¤ (1) une augmentation de l'absorption optique; (2) de la diffusion de la lumière ¨¤ de grands angles ce qui pourrait conduire ¨¤ un meilleur piégeage de la lumière dans les OSCs. D'autre part, (1) la rugosité de surface est augment¨¦e en raison de la formation d'agglomérats de NPSMs d' Ag, ce qui conduit ¨¤ une meilleure efficacité de collecte de charge; (2) la résistance globale des films hybrides est également augment¨¦e en raison de l'excès de PSS introduit par les NPSMs d' Ag incomplètement purifiées, inférieur courant de court-circuit (Jsc) qui en résulte; (3) les Ag NPSMs et leurs agglomérats ¨¤ l'interface PEDOT:PSS/couche photo-active pourraient agir comme des centres de recombinaison, conduisant ¨¤ une réduction de la résistance de shunt, du Jsc et de la tension en circuit ouvert (Voc). Afin de résoudre partiellement l'inconvénient (2) et (3), en intégrant des NPSMs d¡¯Ag davantage purifiés et une petite quantité de glycérol dans le PEDOT:PSS, la résistance des couches hybrides de PEDOT:PSS-Ag-NPSMs peut ¨être réduite à une valeur comparable ou inférieure ¨¤ celles couches vierges. Les futurs progrès en chimie de surface colloïdale et l'optimisation sur le processus d'incorporation des nanoparticules seront nécessaires pour produire des cellules solaires organiques plasmoniques de meilleures performances. / Nowadays there has been a strong global demand for renewable and clean energy due to the rapid consumption of non-renewable fossil fuels and the resulting greenhouse effect. One promising solution to harvest clean and renewable energy is to utilize solar cells to convert the energy of sunlight directly into electricity. Compared to their inorganic counterparts, organic solar cells (OSCs) are now of intensive research interest due to advantages such as light weight, flexibility, the compatibility to low-cost manufacturing processes. Despite these advantages, the power conversion efficiency (PCE) of OSCs still has to be improved for large-scale commercialization. OSCs are made of thin film stacks comprising electrodes, electron transporting layer, active polymer layer and hole transporting layer. In this study, we are concerned with PEDOT:PSS layer which is commonly used as a buffer layer between the anodic electrode and the organic photoactive layer of the OSC thin film stack. We incorporated different concentrations of silver nanoprisms (NPSMs) of sub-wavelength dimension into PEDOT:PSS. The purpose is to take advantage of the unique optical properties of Ag MPSMs arisen from localized surface plasmon resonance (LSPR) to enhance the light harvest and the charge generation efficiency by optimizing absorption and scattering of light in OSCs. We found that the key factors controlling the device performance of plasmonic solar cells include not only the optical properties but also the structural and electrical properties of the resulting hybrid PEDOT:PSS-Ag-NPSM-films. On one hand, the addition of Ag NPSMs led to (1) an increased optical absorption; (2) light scattering at high angles which could possibly lead to more efficient light harvest in OSCs. On the other hand, the following results have been found in the hybrid films: (1) the surface roughness was found to be increased due to the formation of Ag agglomerates, leading to increased charge collection efficiency; (2) the global sheet resistance of the hybrid films also increases due to the excess poly(sodium styrenesulphonate) introduced by incompletely purified Ag NPSMs, resulting in lower short circuit current (Jsc); (3) the Ag nanoprisms and their agglomerates at the PEDOT:PSS/photoactive layer interface could act as recombination centers, leading to reductions in shunt resistance, Jsc and open circuit voltage (Voc). In order to partially counteract the disadvantage (2) and (3), by incorporating further purified Ag NPSMs and/or a small amount of glycerol into PEDOT:PSS, the sheet resistance of hybrid PEDOT:PSS-Ag-NPSM-films was reduced to a resistance value comparable to or lower than that of pristine film.

Diabetes is a disease that causes many complications in human normal function. This disease represents the sixth-leading cause of death in USA. Prevention of diabetes-related complications can be accomplished through tight control of glucose levels in blood. In the last decades many different glucose sensors have been developed, however, none of them are really non invasive. Herein, we present the study of the application of gold and silver nanoparticles with different shapes and aspect ratios to detect glucose traces in human fluids such as tears and sweat. This is to our knowledge the first truly non invasive glucose optical sensor, with extraordinary limit of detection and selectivity. The best proven nanoparticles for this application were gold nanospheres. Gold nanospheres were synthesized using chloroauric acid tri-hydrated (HAuCl4.3H2O) in solution, in the presence of glucose and ammonia hydroxide. The higher the glucose concentration, the higher the number of nanoparticles generated, thus the higher the extinction efficiency of the solution. The linear dependence of the extinction efficiency of the gold nanoparticles solution with glucose concentration makes of this new sensor suitable for direct applications in biomedical sensing. Our approach is based on the well known Tollens test.

Ionic self-assembled multilayers (ISAMs) can be formed by alternately dipping a substrate in anionic and cationic polyelectrolytes. Each immersion deposits a monolayer via electrostatic attraction, allowing for nanometer-scale control over film thickness. Additionally, ISAM films can be applied to arbitrary substrate geometries and can easily incorporate a variety of polymers and nanoscale organic or inorganic inclusions. The ISAM technique was used to tune and functionalize a rapid, sensitive fiber optic biosensor for textit{Brucella}, a family of bacteria that are detrimental to livestock and can also infect humans. The sensor was based on a turn-around point long period fiber grating (TAP-LPG). Unlike conventional LPGs, in which the attenuation peaks shift wavelength in response to environmental changes, TAP-LPGs have a highly sensitive single wavelength peak with variable attenuation. ISAMs were applied to a TAP-LPG to tune it to maximum sensitivity and to facilitate cross-linking of receptor molecules. Biotin and streptavidin were used to attach biotinylated hybridization probes specific to distinct species of textit{Brucella}. The sensor was then exposed to lysed cell cultures and tissue samples in order to evaluate its performance. The best results were obtained when using samples from textit{Brucella} infected mice, which produced a transmission change of 6.0 ± 1.4% for positive controls and 0.5 ± 2.0% for negative controls. While the sensor was able to distinguish between positive and negative samples, the relatively short dynamic range of the available fiber limited its performance. Attempts to fabricate new TAP-LPGs using a CO2 laser were unsuccessful due to poor laser stability. A second application of the ISAM technique was as a source of second-harmonic generation (SHG). SHG is a nonlinear optical process in which light is instantaneously converted to half its wavelength in the presence of intense electric fields. Localized surface plasmons (LSPs) in metal nanoparticles produce strong electric field enhancements, especially at sharp tips and edges, that can be used to increase SHG. Colloidally grown silver nanoprisms were deposited onto nonlinear ISAM films and conversion of 1064 nm Nd:YAG radiation to its 532 nm second-harmonic was observed. Little enhancement was observed when using nanoprisms with LSP resonance near 1064 nm due to their large size and low concentration. When using shorter wavelength nanoprisms, enhancements of up to 35 times were observed when they were applied by immersion, and up to 1380 times when concentrated nanoprisms were applied via dropcasting at high enough densities to broaden their extinction peak towards the excitation wavelength. A maximum enhancement of 2368 times was obtained when concentrated silver nanoprisms with LSP resonance around 900 nm were spincast with an additional layer of PCBS. / Doctor of Philosophy / Polyelectrolytes are long molecules composed of chains of charged monomers. When a substrate with a net surface charge is dipped into an oppositely charged polyelectrolyte solution, a single layer of molecules will be electrostatically deposited onto the substrate. Because the surface charge now appears to match the charge of the solution, no further deposition occurs. However, the process can be repeated by rinsing the substrate and immersing in a solution with the opposite charge. This technique forms ionic self-assembled multilayers (ISAMs), which can be assembled with nanometer-level control over thickness. The flexibility of polymer chemistry allows ISAMs to be formed from polyelectrolytes with a wide variety of properties. Additionally, the technique can easily incorporate other nanoscale materials, such as nanoparticles, clay platelets, and biological molecules, and has been investigated for applications ranging from dye-sensitized organic solar cells to drug delivery and medical implant coatings. This dissertation presents two applications of ISAM films. In one, ISAM films were used to tune and functionalize an optical biosensor for Brucella. Brucellosis primarily infects livestock, in which it causes significant reproductive problems leading to economic losses, but can also cause flu-like symptoms and more serious complications in humans. A rapid, sensitive test for Brucella is required to monitor herds and adjacent wild carriers, such as elk and bison. Optical biosensors, which operate by detecting changes due to the interaction between light and the stimulus, could satisfy this need. Long period fiber gratings (LPGs) are periodic modulations induced in the core of an optical fiber that cause transmitted light to be scattered at a resonant wavelength, resulting in attenuation. Conventional LPGs respond to changes in strain, temperature, or external refractive index by shifting their resonant wavelength. When special conditions are met, an LPG may exhibit a turn-around point (TAP), where dual peaks coalesce into a single peak with a constant wavelength but variable attenuation depth. TAP-LPGs are more sensitive than ordinary LPGs, and could be developed into inexpensive sensors with single-wavelength light sources and detectors. In this work, ISAMs were deposited onto an LPG to tune it near its TAP. Segments of single-stranded DNA, called hybridization probes, that were specific to individual species of Brucella were attached to the ISAM film before the sensor was exposed to lysed bacterial cultures. It was found that the sensor could distinguish between Brucella and other types of bacteria, but was less successful at distinguishing between Brucella species. The project was limited by the available TAP-LPGs, which had less dynamic range than those used in prior work by this group. Attempts were made to establish a new supply of TAP-LPGs by fabrication with a CO2 laser, but these efforts were unsuccessful due to poor laser stability. The second project discussed in this dissertation investigated ISAM films as a source of second-harmonic generation (SHG), a nonlinear optical process in which light is converted to half its fundamental wavelength in the presence of intense electric fields. Nonlinear ISAMs were constructed by choosing a polyelectrolyte with a hyperpolarizable side group in which SHG can occur. The SHG efficiency was increased by factors of several hundred to several thousand by the addition of silver nanoprisms. Metal nanoparticles can produce strong electric field enhancements, especially at their tips and edges, when incident light causes resonant collective oscillations in their electrons called localized surface plasmons (LSPs). It was found that while silver nanoprisms whose LSP resonant wavelength matched the fundamental wavelength were too dilute to produce noticeable enhancement, better results could be obtained by depositing shorter wavelength nanoprisms at sufficient density to broaden their extinction peak via interparticle interactions. The best enhancement observed was for a sample where concentrated silver nanoprisms with LSP resonance around 900 nm were dropcast onto an ISAM film and coated with an additional polymer layer, resulting in 2368 times more SHG than the plain ISAM film.