The precise control of the resonance frequency of plasmonic nanostructures is critical and depends on the size, composition, shape, and dielectric nature of the environment. The ability to control the shape and size of nanomaterials acutely depends on the fabrication technique and material design. We used a cheap and scalable method known as nanosphere lithography (NSL) to fabricate plasmonic nano-prism (NP) on glass and indium tin oxide substrate (ITO). The methods involve substrate hydrophilicity treatment, polystyrene nanosphere masking, metal deposition, and mask removal. The array and specific morphology of the fabricated NP was established using scanning electron microscope (SEM) and atomic force microscope (AFM). Finally, we used UVVis spectroscopy to determine the plasmonic resonance frequencies of fabricated NP on different substrates. The results reported herein have potential applications in surface-enhanced Raman spectroscopy (SERS), and biosensing. We also used scanning tunneling microscope to obtain high spatial resolution images of supramolecular trigrams.

Les métamatériaux forment une nouvelle classe de matériaux composites artificiels aux propriétésélectromagnétiques extraordinaires. Ces propriétés inédites reposent sur l’inclusion, dans le métamatériau,de résonateurs plasmoniques dont la fabrication et l’assemblage posent un défi auquel se heurtent lestechniques de gravure habituellement utilisées. Cette thèse est consacrée à la de ces nano-résonateurs demorphologie framboise, constitués d’un coeur diélectrique et de nanoparticules plasmoniques, sphériquesou triangulaires. Ces objets ont été élaborés en grande quantité tout en respectant la contrainte du milieueffectif qui impose des tailles très inférieures à la longueur d’onde. La réponse optique des nanorésonateursindividuels a été mesurée et comparée aux modélisations. Des résonances électriques etmagnétiques intenses ont été mises en évidence. Ces objets sont prometteurs pour la première réalisationde matériau massif à perméabilité magnétique artificielle. / Metamaterials are artificial composites materials exhibiting extraordinary electromagnetic properties.These original properties are based on the inclusion in the metamaterial of plasmonic resonators for whichthe fabrication and the assembly remain challenging. This thesis is dedicated to the synthesis throughcolloidal approach and the structural and optical characterization of these “raspberry-like nanoresonators”constituted of a dielectric core and spherical or triangular plasmonic nanoparticles.These objects are elaborated in large amount while respecting the constraint of effective medium whichrequires sizes much smaller than the wavelength. The optical response of individual nanoresonators wasmeasured and compared with theoretical simulations. Intense electric and magnetic resonances arehighlighted. These objects are promising for the first elaboration of a bulk material with artificial magneticpermeability.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-06-07T11:31:21Z No. of bitstreams: 1 brunoguilhermedafonseca.pdf: 3400228 bytes, checksum: 5e2e24048845084805ad960c6e33ecac (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-07-02T13:29:49Z (GMT) No. of bitstreams: 1 brunoguilhermedafonseca.pdf: 3400228 bytes, checksum: 5e2e24048845084805ad960c6e33ecac (MD5) / Made available in DSpace on 2016-07-02T13:29:49Z (GMT). No. of bitstreams: 1 brunoguilhermedafonseca.pdf: 3400228 bytes, checksum: 5e2e24048845084805ad960c6e33ecac (MD5) Previous issue date: 2016-02-29 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho investigou-se a adsorção do triptofano (Trp), seus derivados e do 2-mercaptoetanol (MET) na superfície de nanopartículas metálica de prata ou ouro. Utilizou-se como ferramentas para o estudo, as técnicas espectroscópicas de absorção no ultravioleta e visível (UV-VIS), espalhamento Raman normal e intensificado pela superfície (surface-enhanced Raman scattering – SERS) e cálculos teóricos baseados na teoria do funcional da densidade (density functional theory – DFT). A banda da ressonância do plásmon de superfície localizado (localized surface plasmon resonance – LSPR) foi monitorada nos espectros UV-VIS para a investigação das propriedades eletrônicas das nanopartículas metálicas, envolvidas nas interações com os adsorbatos e nas distribuições de tamanhos. Foram sintetizados nanoprismas de prata estabilizados por citrato de sódio em diferentes condições de temperatura, envolvendo múltiplas etapas de crescimento e usando cobre como dopante indutor de geometria. A inclusão de pequena quantidade de cobre, em relação a prata, levou à maior formação de nanoprismas triangulares que o método original. Estas superfícies foram utilizadas nos estudos da adsorção do MET. Os nanoprismas, dopados ou não, mostraram-se inadequados para uso como substrato SERS de outros adsorbatos que não fossem mercaptanas. Sintetizou-se também nanoesferas de prata ou ouro para o estudo da adsorção do Trp e seus derivados em diferentes ambientes químicos. Os nanoprismas foram utilizados para estudos LSPR na presença do MET em diferentes concentrações, além da obtenção do espectro SERS da molécula. Observou-se que a concentração possui papel determinante na auto-organização de uma monocamada molecular, fazendo com que a conformação predominante se altere na superfície metálica. Os cálculos por DFT permitiram a simulação da adsorção do MET em superfície (111) de prata e obtenção de resultados relacionados às estruturas e estabilidades dos confôrmeros. Teoria e experimento mostraram-se em acordo dentro das condições estudadas e permitindo inferir que a ligação de hidrogênio possui um papel chave nas propriedades da monocamada. Estudou-se a adsorção dos isômeros L-Trp e D-Trp e dos peptídeos Ala-Trp, Trp-Gly, pGlu-Lys-Trp-Ala-Pro e Trp-His-Trp-Leu-Gln-Leu através das espectroscopias SERS e UV-VIS. Em prata, os espectros mostraram que os aminoácidos e os dipeptídeos adsorvem preferencialmente através dos grupos carboxilato e amina. Em ouro, a análise espectral permitiu identificar a adsorção das moléculas de Trp via nitrogênio do anel indólico. Os espectros foram obtidos em concentração de 10-3 mol L-1 nos diferentes metais, contudo a adição de HCl permitiu a obtenção de espectros em 10-5 mol L-1. As diferenças entre os espectros em ouro permitiram concluir que o Trp interage mais intensamente com a superfície na presença de HCl. A partir de todos os resultados obtidos, pode-se sugerir que as nanopartículas de ouro mostram-se úteis para o estudo de estruturas mais complexas por diferencia o triptofano adsorvido à superfície de outros presentes na estrutura de interesse. / The adsorption of tryptophan (Trp), his derivatives and 2-mercaptoethanol (MET) on metallic nanoparticle surface had been studied on this thesis. For such investigations it was employed the following tools: ultraviolet and visible absorption spectroscopy (UV-VIS), Raman scattering spectroscopy, surface enhanced Raman spectroscopy (SERS) and density functional theory. The localized surface plasmon resonance (LSPR) band was monitored on UV-VIS spectra to study the electronic properties of metallic nanoparticles involved in the interactions with the adsorbates and the size distributions. Silver nanoplates were synthesized in different conditions of temperature, multiple growing steps and using copper as a stabilizing doping. A small addition of copper, compared to silver, increased the triangular nanoprism yield of the original synthesis. These nanoparticles were used for adsorption study of MET. It was synthesized gold and silver nanospheres for studying Trp adsorption and other peptides on different chemical surroundings. The nanoprisms were utilized for LSPR study in the presence of MET at different concentrations, in addition to SERS spectra of this molecule. It has been observed the molecule concentration has a key role for self-assembled monolayer formation, which changes the most common conformer on the metallic surface. DFT calculation allowed us to simulate MET adsorption on silver surface (111) obtaining results related to the structures and stabilities of the conformers. Theory and experiment showed in agreement in the conditions studied and conclude the hydrogen bond is a key player in the monolayer properties. It was studied the adsorption of the isomers, L-Trp and D-Trp, and the peptides, Ala-Trp, Trp-Gly, pGlu-Lys-Trp-Ala-Pro and Trp-His-Trp-Leu-Gln-Leu, through SERS spectroscopy. In silver, the spectra showed amino acids and dipeptides tend to adsorb by the acid and amine group. In gold, an enhancement and shifting of the bands allowed us to identify the adsorption by the indole ring, specifically by the nitrogen atom. The spectra were obtained at concentration of 10-3mol.L-1 on different metals, however in presence of HCl the molecular concentration was 10-5mol.L-1. When HCl was added, the spectra showed a slightly different pattern, which suggest us that, in this condition, Trp interacts stronger to the surface.