Search results for "quantum dots"
showing 10 items of 121 documents
Semi-local density functional for the exchange-correlation energy of electrons in two dimensions
2010
We present a practical and accurate density functional for the exchange-correlation energy of electrons in two dimensions. The exchange part is based on a recent two-dimensional generalized-gradient approximation derived by considering the limits of small and large density gradients. The fully local correlation part is constructed following the Colle-Salvetti scheme and a Gaussian approximation for the pair density. The combination of these expressions is shown to provide an efficient density functional to calculate the total energies of two-dimensional electron systems such as semiconductor quantum dots. Excellent performance of the functional with respect to numerically exact reference da…
Exploration of the double exchange in quantum cellular automata: proposal for a new class of cells
2020
In this communication we propose to considerably extend the class of systems suitable as cells for quantum cellular automata by including magnetic quantum dots and molecular mixed valence dimers exhibiting double exchange. As distinguished from the previous works we propose to use not only charges as the information carriers but also spin degrees of freedom. In this context we focus on the two key points: (1) properties of the magnetic cell as reservoir for charges carrying binary information, and (2) identification of conditions under which spin degrees of freedom can be employed.
Hybrid Gold/Silica/Quantum-Dots supramolecular-nanostructures encapsulated in polymeric micelles as potential theranostic tool for targeted cancer th…
2018
Abstract Efficient theranostic tools are today more and more frequently represented by the nano-sized systems. In this paper, polymeric micelles were produced and exploited to encapsulate both an antitumor drug (Doxorubicin) and gold core–shell quantum dots nanoparticles (Au-SiO2/QDs). α,β-poly(N-hydroxyethyl)- dl -aspartamide (PHEA) was functionalized with lipoic acid (LA), polyethylenglycol (PEG), and folic acid (FA) pendant moieties to obtain a synthetic derivative (PHEA-LA-PEG-FA) able to self assemble in aqueous medium giving rise to the formation of polymeric micelles exposing on their surface both targeting groups (FA) and hydrophilic chains (PEG). The drug carrying ability of PHEA-L…
Size dependent light absorption modulation and enhanced carrier transport in germanium quantum dots devices
2015
Quantum confinement in closely packed arrays of Ge quantum dots (QDs) was studied for energy applications. In this work, we report an efficient tuning mechanism of the light harvesting and detection of Ge QDs. Thin films of SiGeO alloys, produced by rf-magnetron sputtering, were annealed at 600 degrees C in N-2 to induce precipitation of small amorphous Ge QDs into the oxide matrix. Varying the Ge content, the QD size was tailored between 2 and 4 nm, as measured by high resolution transmission electron microscopy. X-ray photoelectron spectroscopy (XPS) measurements indicate the formation of pure SiO2, as well as the presence of a sub-stoichiometric Ge oxide shell at the QD interface. Light …
Cryopreservation of MHC Multimers: Recommendations for Quality Assurance in Detection of Antigen Specific T Cells
2015
Fluorescence-labeled peptide-MHC class I multimers serve as ideal tools for the detection of antigen-specific T cells by flow cytometry, enabling functional and phenotypical characterization of specific T cells at the single cell level. While this technique offers a number of unique advantages, MHC multimer reagents can be difficult to handle in terms of stability and quality assurance. The stability of a given fluorescence-labeled MHC multimer complex depends on both the stability of the peptide-MHC complex itself and the stability of the fluorochrome. Consequently, stability is difficult to predict and long-term storage is generally not recommended. We investigated here the possibility of…
Uptake of silica covered Quantum Dots into living cells: Long term vitality and morphology study on hyaluronic acid biomaterials
2015
Quantum Dots (QDs) are promising very bright and stable fluorescent probes for optical studies in the biological field but water solubility and possible metal bio-contamination need to be addressed. In this work, a simple silica-QD hybrid system is prepared and the uptake in bovine chondrocytes living cells without any functionalization of the external protective silica shield is demonstrated. Moreover, long term treated cells vitality (up to 14 days) and the transfer of silica-QDs to the next cell generations are here reported. Confocal fluorescence microscopy was also used to determine the morphology of the so labelled cells and the relative silica-QDs distribution. Finally, we employ sil…
Competition between memory-keeping and memory-erasing decoherence channels
2014
We study the competing effects of simultaneous Markovian and non-Markovian decoherence mechanisms acting on a single spin. We show the existence of a threshold in the relative strength of such mechanisms above which the spin dynamics becomes fully Markovian, as revealed by the use of several non-Markovianity measures. We identify a measure-dependent nested structure of such thresholds, hinting at a causality relationship among the various non-Markovianity witnesses used in our analysis. Our considerations are then used to argue the unavoidably non-Markovian evolution of a single-electron quantum dot exposed to both intrinsic and Markovian technical noise, the latter of arbitrary strength.
Ultrafast Carrier Redistribution in Single InAs Quantum Dots Mediated by Wetting-Layer Dynamics
2019
Optical studies of single self-assembled semiconductor quantum dots (QDs) have been a topic of intensive investigation over the past two decades. Due to their solid-state nature, their electronic and optical emission properties are affected by the particular crystal structure as well as many-body-carrier interactions and dynamics. In this work, we use a master equation for microstates (MEM) model to study the carrier capture and escape from single QDs under optical nonresonant excitation and under the influence of a two-dimensional (2D) carrier reservoir (the wetting layer). This model reproduces carrier dynamics from power-dependent and time-resolved microphotoluminescence experiments . Du…
Assemblies of semiconductor quantum dots and light-harvesting-complex II
2010
Abstract A novel hybrid system composed of fluorescent core/shell semiconductor quantum dots and the light harvesting complex II (LHCIIb), a membrane protein of higher plants, has been assembled. Experiments with different mutants show that hybrid formation can be mediated by a C-terminal His 6 tag attached to the protein as well as by positive charges of the first N-terminal amino acids of LHCIIb. Quenching of the quantum dot fluorescence upon binding of LHCIIb was partially attributed to energy transfer from the quantum dots to LHCIIb.
The use of theranostic gadolinium-based nanoprobes to improve radiotherapy efficacy
2014
International audience; A new efficient type of gadolinium-based theranostic agent (AGuIX) has recently been developed for magnetic resonance imaging (MRI)-guided radiotherapy. These new particles consist of a polysiloxane network surrounded by a number of gadolinium chelates, usually 10. Due to their small size (<5 nm), AGuIX typically exhibit biodistributions that are almost ideal for diagnostic and therapeutic purposes. For example, while a significant proportion of these particles accumulate in tumours, the remainder is rapidly eliminated by the renal route. In addition, these particles present no evidence of toxicity, in the absence of irradiation with up to 10 times the planned dose f…