Search results for "Plasmonic"

Manufacturing of graphene nanodisks for surface plasmon measurements

2017

Grafeeni on ilmestynyt tieteen rintamalle kovalla ryminällä vasta viimeisen 13 vuoden aikana, mutta on jo nyt yksi mielenkiintoisimmista tutkimuskohteista, jolla voisi olla lukuisia sovelluksia tulevaisuudessa. Grafeeni on ilmestynyt myös plasmoniikan tutkimuskohteeksi sen lukuisten ainutlaatuisten sähköisten ja optisten ominaisuuksien takia ja sen ominaisuuksien muokattavuuden helppouden takia. Grafeeni voisi mahdollisesti korvata yleisesti käytössä olleet jalot metallit kuten kullan ja hopean pintaplasmonien tuotossa ja tutkimuksessa ja voisi johtaa uudenlaiseen valon kontrollointiin nanoskaalassa ja optiikan ja elektroniikan yhdistämiseen tässä pienessä mittakaavassa. Tässä työssä tavoit…

Kohn-Sham Decomposition in Real-Time Time-Dependent Density-Functional Theory An Efficient Tool for Analyzing Plasmonic Excitations

2017

The real-time-propagation formulation of time-dependent density-functional theory (RT-TDDFT) is an efficient method for modeling the optical response of molecules and nanoparticles. Compared to the widely adopted linear-response TDDFT approaches based on, e.g., the Casida equations, RT-TDDFT appears, however, lacking efficient analysis methods. This applies in particular to a decomposition of the response in the basis of the underlying single-electron states. In this work, we overcome this limitation by developing an analysis method for obtaining the Kohn-Sham electron-hole decomposition in RT-TDDFT. We demonstrate the equivalence between the developed method and the Casida approach by a be…

Plasma polymer films and gold nanoparticles: coupling of properties to design a biosensor

The present investigation deals with the functionalization of gold nanoparticles (Au NPs) with primary amine-based plasma polymer films (NH2-PPF), to improve their properties for bioanalytical applications. Cyclopropylamine (CPA) plasma polymerization, in pulsed and continuous wave radio frequency discharges, was employed to growth CPA amino-based PPFs coatings (18 nm) onto Au NPs of 12 nm of diameter deposited on glass and silicon substrates. A multi-technique investigation, based on FT-IR and XPS spectroscopies, AFM and SEM microscopies and Tof-SIMS spectrometry, revealed peculiar features of the CPA PPFs. In particular, by FT-IR it was possible to obtain an overview about the rich chemis…

Localized surface plasmon resonance in silver nanoparticles: Atomistic first-principles time-dependent density-functional theory calculations

2015

We observe using ab initio methods that localized surface plasmon resonances in icosahedral silver nanoparticles enter the asymptotic region already between diameters of 1 and 2 nm, converging close to the classical quasistatic limit around 3.4 eV. We base the observation on time-dependent density-functional theory simulations of the icosahedral silver clusters Ag$_{55}$ (1.06 nm), Ag$_{147}$ (1.60 nm), Ag$_{309}$ (2.14 nm), and Ag$_{561}$ (2.68 nm). The simulation method combines the adiabatic GLLB-SC exchange-correlation functional with real time propagation in an atomic orbital basis set using the projector-augmented wave method. The method has been implemented for the electron structure…

Optical properties of conductive carbon-based nanomaterials

2016

The interaction of light with carbon nanomaterials is the main focus of this thesis. I explore several nanostructured systems involving different allotropes of carbon, and characterize them both electrically, if applicable, and optically. Special attention is paid to search for plasmon-like excitations on the systems, or utilizing surface plasmons on characterization. The first objective is to achieve control of carbon nanotube (CNT) conductivity with surface plasmon polaritons (SPPs), which resulted in the first CNT field-effect transistor (FET) that can be gated definitively with SPPs. The second objective is the investigation of optical properties of various thin carbon-based molecular n…

Image formation with plasmonic nanostructures

2015

En 1873, Ernst Abbe concluyó que debido a la difracción de la luz el límite de resolución de un sistema óptico es aproximadamente la mitad de la longitud de onda de trabajo. Este límite, llamado el límite de difracción produce porque las ondas evanescentes no contribuyen a la formación de la imagen. En cualquier sistema óptico formado por materiales presentes en la naturaleza los detalles espaciales del objeto que sean más pequeños que el límite de resolución son transportados por ondas evanescentes. Normalmente estas ondas se pierden debido a la fuerte atenuación que experimentan viajando del objeto a la imagen. // En 1968, Veselago mostró que un material con permitividad y permeabilidad n…