This work deals with the preparation of gold nanostructures for future usage in electrochemical sensors and biosensors, methods for their characterization and production. The emphasis is focused on the template-based electrodeposition method of gold and on study of the effect of manufacturing conditions on physical properties, mainly electrical and topological of nanostructures. Thesis is focused also on overall function and sensitivity of the gold nanostructured electrode.

Plasmonic nanocrystals have a unique ability to support localized surface plasmon resonances and exhibit rich and intriguing optical properties. Engineering plasmonic nanocrystals can maximize their potentials for specific applications. In this dissertation, we developed three unprecedented Au nanorod-based plasmonic nanocrystals through rational design of the crystal shape and/or composition, and successfully demonstrated their applications in light condensation, photothermal conversion, and surface-enhanced Raman spectroscopy (SERS). The “Au nanorod-Au nanosphere dimer” nanocrystal was synthesized via the ligand-induced asymmetric growth of a Au nanosphere on a Au nanorod. This dimeric nanostructure features an extraordinary broadband optical absorption in the range of 400‒1400nm, and it proved to be an ideal black-body material for light condensation and an efficient solar-light harvester for photothermal conversion. The “Au nanorod (core) @ AuAg alloy (shell)” nanocrystal was built through the epitaxial growth of homogeneously alloyed AuAg shells on Au nanorods by precisely controlled synthesis. The resulting core-shell structured, bimetallic nanorods integrate the merits of the AuAg alloy with the advantages of anisotropic nanorods, exhibiting strong, stable and tunable surface plasmon resonances that are essential for SERS applications in a corrosive environment. The “high-index faceted Au nanorod (core) @ AuPd alloy (shell)” nanocrystal was produced via site-specific epitaxial growth of AuPd alloyed horns at the ends of Au nanorods. The AuPd alloyed horns are bound with high-index side facets, while the Au nanorod concentrates an intensive electric field at each end. This unique configuration unites highly active catalytic sites with strong SERS sites into a single entity and was demonstrated to be ideal for in situ monitoring of Pd-catalyzed reactions by SERS. The synthetic strategies developed here are promising towards the fabrication of novel plasmonic nanocrystals with fascinating properties for nanoplasmonics and nanophotonics.

Les nanoparticules de fluorures dopées avec des ions lanthanides ont connu un développement croissant ces dernières années. Elles présentent en effet des propriétés optiques d’upconversion remarquables et très intéressantes pour de multiples applications allant du photovoltaïque à l’imagerie médicale. Dans cette thèse, on a élaboré des nanobâtonnets de NaYF4 dopés Yb/Er/Gd, aux propriétés d’émission optimisées. Leur alignement par un champ électrique a ensuite été étudié, nous permettant de tirer parti de leur anisotropie et des propriétés physiques en découlant : biréfringence et luminescence polarisée.Les nanocristaux sont synthétisés par voie solvothermale, à haute température (200 °C) et sous haute pression (20 bars). Leur morphologie et leur structure cristalline sont contrôlées par un choix approprié des paramètres de synthèse comme le dopage en gadolinium ou les conditions de chauffage. A l’issue de la synthèse, l’état d’agrégation des particules de NaYF4 produites limite leur dispersion dans les solvants organiques usuels. Une fonctionnalisation bien spécifique avec des ligands possédant des groupements carboxylate ou phosphonate se révèle alors indispensable. Le greffage des particules avec un ion citrate ou une molécule d’alendronate permet d’obtenir des suspensions colloïdales très stables dans le DMSO. Par ailleurs, la réactivité de l’amine porté par l'alendronate nous a permis de greffer une deuxième molécule active : une rhodamine B, un colorant test, ainsi qu’un cristal liquide cyanobiphényl à tête carboxylique. Grâce à cette fonctionnalisation, de nouveaux matériaux hybrides organo-minéraux ont été développés. La réponse électro-optique des suspensions colloïdales soumises à un champ électrique haute fréquence suit une loi de type effet Kerr, avec une relation quadratique entre la biréfringence induite et l’amplitude du champ appliqué. Les constantes de Kerr sont de l’ordre de 10 8 m/V2 en cohérence avec ce qui a été observé sur d’autres systèmes. La biréfringence observée est majoritairement induite par la structure cristalline anisotrope des particules. Le mécanisme de réorientation de nos particules sous champ est largement dominé par la polarisation de leur nuage électronique. Une luminescence polarisée est finalement décrite, ouvrant la voie à l’usage des nanobâtonnets de NaYF4 comme sondes d’orientation dans des systèmes biologiques ou au sein de fluides en écoulement. / Fluorides nanoparticles doped with lanthanides have seen an increase in interest the last years. They offer outstanding optical properties with a very attractive upconversion for multiple applications from photovoltaics to medical imaging. In this work, we use NaYF4 nanorods doped with Yb/Er/Gd and optimized emission properties. Their alignment by an electric field allows us to access their anisotropic physical properties like polarized luminescence and birefringence.Nanocrystals are synthesized by a hydrothermal route, at high temperature (200 °C) and high pressure (20 bar). Morphology and crystalline structure can be controlled by varying gadolinium doping and heating conditions. At the end of the synthesis, the aggregation of the particles limits their dispersion in all common organic solvents. A particular functionalization with ligands having carboxylate or phosphonate functions is shown to be necessary. The grafting of particles with ions like citrate or alendronate allows to obtain very stable colloidal suspensions in DMSO. Furthermore, the reactivity of the amine function carried by alendronate enables us to graft a second active dye like rhodamine B or a cyanobiphenyl liquid crystal with a carboxylic group. New organo-mineral materials can be produced with this functionalization. The electro-optical response of colloidal suspensions submitted to a high-frequency electric field follows the Kerr law, with a quadratic relation between induced birefringence and the amplitude of the applied field. The system exhibits Kerr constants of the order of 108 m/V2, in agreement with the literature. The birefringence is induced by the anisotropic crystalline structure of the colloid, not by its shape. The mechanism of reorientation of colloids under an electric field is widely dominated by the polarization of their ionic cloud. A polarized luminescence is finally described, which will allow the use of NaYF4 nanorods as orientation probes in biological systems or fluid flows.

No description available.

No description available.

Microplastic (MP) pollution has recently been recognized as a threat to the biosphere including humans due to its widespread distribution, persistent nature and infinitesimal size. This study focused on the solid phase degradation of microplastic residues (particularly low density polyethylene, LDPE) in water through heterogeneous photocatalysis process by designed photocatalysts of zinc oxide nanorods (ZnO NRs) and platinum nanoparticles deposited on zincoxide nanorods (Pt NPs-ZnO NRs) under visible light irradiation. These photocatalysts were assessed following standard protocol (ISP 10678: 2010), and characterized using SEM, EDX andoptical spectroscopies (UV-VIS and PL). Deposition of Pt-NPs on ZnO NRs for certain minutes has been found optimum that enhanced the photodegradation process about 38% under UV irradiation and 16.5% under visible light irradiation by improving of both electrons-holes pair separation process and visible light absorption. Photocatalytic degradation of LDPE films was confirmed by FTIR spectroscopy, dynamic mechanical analyzer (DMA), optical and electron microscopes. When LDPE film irradiated in presence of Pt-ZnO, degradation was found quicker than ZnO alone of similar concentration which exhibited formation of a large number of wrinkles, cracks and cavities on the film surface. Dynamic mechanical analyzer (DMA) test indicated stiffness and embrittlement of exposed LDPE films in presence of photocatalysts. Thus, the present work provides a new insight about modified catalysts for the degradation of microplastics in water using visible light.

Bottom-up self-assembly has the potential to fabricate nanostructures with advanced electrical features. DNA templates have been used to enable such self-assembling methods due to their versatility and compatibility with various nanomaterials. This dissertation describes research to advance several different steps of biotemplated nanofabrication, from DNA assembly to characterization. I assembled different nanomaterials including surfactant-coated Au nanorods, DNA-linked Au nanorods and Pd nanoparticles on DNA nanotubes ~10 micrometer long, and on ~400 nm long bar-shaped DNA origami templates. I optimized seeding by changing the surfactant and magnesium ion concentrations in the seeding solution. After successful seeding, I performed electroless plating on those nanostructures to fabricate continuous nanowires. Using the four-point probe technique, I performed resistivity measurements for Au nanowires on DNA nanotubes and obtained values between 9.3 x 10-6 and 1.2 x 10-3 ohm meter. Finally, I demonstrated the directed placement of DNA origami using block copolymer self-assembly. I created a gold nanodot array using block copolymer patterning and metal evaporation followed by lift-off. Then, I used different ligand groups and DNA hybridization to attach DNA origami to the nanodots. The DNA hybridization approach showed greater DNA attachment to Au nanodots than localization by electrostatic interaction. These results represent vital progress in understanding DNA-templated components, nanomaterials, and block copolymer nanolithography. The work in this dissertation shows potential for creating DNA-templated nanodevices and their placement in an ordered array in future nanoelectronics. Each of the described materials and techniques further has potential for addressing the need for increased complexity and integration for future applications.

No description available.

No description available.

No description available.