Search results for "quantum dot"

Functional CdSe and CdSe/ZnS nanoparticles capped with thiols: photophysical and photochemical properties and applications as sensors

2013

Esta tesis se centra en el efecto simbiótico entre los QDs de CdSe o CdSe/ZnS y sus ligandos orgánicos, y las ventajas de este efecto para mejorar la funcionalidad del QD y/o del ligando, o crear una nueva funcionalidad del sistema. Así : 1. la superficie de las nanopartícula recubierta con ligandos orgánicos puede permitir al QD i) permanecer estable en disolventes orgánicos o acuosos, debido a la repulsión estérica o iónica entre las nanopartículas, ii) mantener o aumentar sus propiedades emisivas (pasivación de los defectos de superficie, aumento de distancia entre nanopartícula y moléculas desactivadoras), y/o iii) para proporcionar funcionalidad a la nanopartícula. 2. la forma esférica…

Exciton and multiexciton optical properties of single InAs/GaAs site-controlled quantum dots

2013

We have studied the optical properties of InAs site-controlled quantum dots (SCQDs) grown on pre-patterned GaAs substrates. Since InAs nucleates preferentially on the lithography motifs, the location of the resulting QDs is determined by the pattern, which is fabricated by local oxidation nanolithography. Optical characterization has been performed on such SCQDs to study the fundamental and excited states. At the ground state different exciton complex transitions of about 500 μeV linewidth have been identified and the fine structure splitting of the neutral exciton has been determined (≈65 μeV). The observed electronic structure covers the demands of future quantum information technologies.…

DNA-based applications in molecular electronics

2011

This thesis is mainly focused on DNA molecules and especially on self-assembled DNA constructs and their potential applications in nanotechnology and molecular electronics. In the field of molecular electronics the conductivity of DNA is a crucial - yet open - question, and it is of great concern, since DNA is a very promising molecule in a context of bottom-up based nanodevices due to its superior selfassembly characteristics. A key tool in all the experiments presented in this thesis is a dielectrophoretic trapping technique, which was exploited in spatial manipulation of individualDNA molecules, DNA constructs and also semiconducting quantum dots. In the case of DNA, the technique provid…

Gamma-Ray-Induced Structural Transformation of GQDs towards the Improvement of Their Optical Properties, Monitoring of Selected Toxic Compounds, and …

2022

Structural modification of different carbon-based nanomaterials is often necessary to improve their morphology and optical properties, particularly the incorporation of N-atoms in graphene quantum dots (GQDs). Here, a clean, simple, one-step, and eco-friendly method for N-doping of GQDs using gamma irradiation is reported. GQDs were irradiated in the presence of the different ethylenediamine (EDA) amounts (1 g, 5 g, and 10 g) and the highest % of N was detected in the presence of 10 g. N-doped GQDs emitted strong, blue photoluminescence (PL). Photoluminescence quantum yield was increased from 1.45, as obtained for non-irradiated dots, to 7.24% for those irradiated in the presence of 1 g of …

An Overview of Functionalized Graphene Nanomaterials for Advanced Applications

2021

Interest in the development of graphene-based materials for advanced applications is growing, because of the unique features of such nanomaterials and, above all, of their outstanding versatility, which enables several functionalization pathways that lead to materials with extremely tunable properties and architectures. This review is focused on the careful examination of relationships between synthetic approaches currently used to derivatize graphene, main properties achieved, and target applications proposed. Use of functionalized graphene nanomaterials in six engineering areas (materials with enhanced mechanical and thermal performance, energy, sensors, biomedical, water treatment, and c…

Facile Synthesis of Fluorescent Polymer Nanoparticles by Covalent Modification-Nanoprecipitation of Amine-Reactive Ester Polymers

2015

Emission wavelength control in fluorescent nanoparticles (NPs) is crucial for their applications. In the case of inorganic quantum dots or dye-impregnated silica NPs, such a control is readily achieved by changing the size of the particles or choosing appropriate fluorescent dyes, respectively. A similar modular approach for controlling the emission wavelength of fluo-rescent polymer NPs, however, is difficult. This article reports on fluorescent polymer NPs, the synthesis of which provides a platform for a modular approach towards the preparation of fluorescent NPs of desired emission wavelength. Atom-transfer radical polymerization (ATRP) is employed to synthesize reactive ester polymers,…

Fluorescent quantum dot labeling of canine transferrin receptor with biotin ligase

2007

Síntesis y caracterización de compuestos de Cu(II) con derivados triazólicos. Estudio de su actividad como potenciales nucleasas químicas

2014

The main goal of this PhD thesis concerns the development of artificial metallonucleases based on copper(II)-1,2,4-triazole compounds. In order to do so, we have obtained metal compounds of different nuclearities by reaction of a new family of 1,2,4-triazole ligands with copper(II) salts. The ligands own the characteristic triazole properties upon coordinating to metals and also integrate DNA binding units (aromatic moieties) with the aim of increasing the affinity of the corresponding metal complexes to double strand DNA. We have also chosen the copper(II) ion due to its intrinsic redox and coordination properties. Here we present our conclusions in relation with their structure/activity a…

Ge quantum well plasmon-enhanced quantum confined Stark effect modulator

2014

ABSTRACTWe theoretically and experimentally investigate a novel modulation concept on silicon (Si) based on the combination of quantum confinement and plasmon enhancement effects. We experimentally study the suitability of Ge/SiGe quantum wells (QWs) on Si as the active material for a plasmon-enhanced optical modulator. We demonstrate that in QW structures absorption and modulation of light with transverse magnetic (TM) polarization are greatly enhanced due to favorable selection rules. Later, we theoretically study the plasmon propagation at the metal-Ge/SiGe QW interface. We design a novel Ge/SiGe QW structure that allows maximized overlap between the plasmonic mode and the underlying Ge/…

Toward Quaternary QCA : Novel Majority and XOR Fuzzy Gates

2022

As an emerging nanotechnology, quantum-dot cellular automata (QCA) has been considered an alternative to CMOS technology that suffers from problems such as leakage current. Moreover, QCA is suitable for multi-valued logic due to the simplicity of implementing fuzzy logic in a way much easier than CMOS technology. In this paper, a quaternary cell is proposed with two isolated layers because of requiring three particles to design this quaternary cell. Moreover, due to the instability of the basic gates, the three particles cannot be placed in one layer. The first layer of the proposed two-layer cell includes a ternary cell and the second one includes a binary cell. It is assumed that the over…