Nanotechnologie des Semi-conducteurs Quantiques III-V pour la Détection de Legionella pneumophila en Milieu Aqueux

Abstract: It has been known that GaAs and AlGaAs could be decomposed in aqueous environments and, if irradiated with photons of energy exceeding bandgap of these materials, their decomposition accelerates through a well-known photocorrosion process. The sensitivity of photoluminescence (PL) of semiconductors to the presence of surface states has been investigated quite extensively for many years, however it was not until recently that the measurements of PL were proven to be sensitive to monitor in situ photocorrosion with a sub-monolayer precision. One important consequence of this characteristics is a strong sensitivity of PL to the perturbation of a near surface electric field and transfer of the electric charge. This made photocorrosion of GaAs/AlGaAs nanoheterostructures appealing, as a propitious transducer, for sensing the near surface electric charge perturbations induced by the negatively charged bacteria. In this thesis, the mechanisms of photo-induced III-V semiconductor dissolution have been investigated by conducting inductively coupled plasma mass spectrometry (ICP-MS) of aqueous photocorrosion products. The experiments carried out for GaAs/Al0.35Ga0.65As nanoheterostructures photocorroding in DI H2O and NH4OH milieus confirmed that the digital photocorrosion (DIP) of these nanoheterostructure could be controlled with a sub-monolayer precision. The conditions leading to a congruent decomposition, defined by a constant photocorrosion rate, were investigated with ICP-MS measurements and a set of surface/interface characterization methods employing FTIR, XPS and AFM. This allowed demonstrating that, in contrast to the DI H2O supporting photocorrosion, the NH4OH environment leads to formation of stoichiometric surfaces of the investigated nanoheterostructures photocorroding by at least 100 nm. The constant photocorrosion rate was also observed in situ by monitoring temporal positions of PL revealed interfaces between GaAs and AlGaAs layers. These results demonstrate the feasibility of a simple and relatively inexpensive process for in situ diagnostics of atomic layer etching of compound semiconductors that could lead to formation of stoichiometric surfaces of such materials. The study of digital photocorrosion were expanded on investigation of this process for sensitive detection of electrically charged Legionella pneumophila in an aqueous environment. The enhanced immobilization of these bacteria on the biosensor surface was confirmed with electrically biased GaAs/AlGaAs biochip. Thus, a central hypothesis was that decorating naturally found L. pneumophila with negatively charged biomolecules should lead to a digital photocorrosion based detection with a much-enhanced limit of detection (LOD). In agreement with the zeta potential measurements, the sodium dodecyl sulfate (SDS) decorated L. pneumophila interacted much stronger with the photocorroding GaAs/AlGaAs biochips. This allowed detecting these bacteria in a diluted phosphate buffered saline (PBS) solution at 103 colony forming units (CFU) per ml. The results of this research give a deeper insight into the capability of DIP process for tracking down the conditions leading to formation of stoichiometric surfaces of etched compound semiconductors. Furthermore, this thesis contributes towards development of an innovative method of detecting electrically charged molecules in liquid environments.Il a été avéré que le GaAs et l'AlGaAs peuvent être décomposés dans des environnements aqueux et que s'ils sont irradiés avec des photons d'énergie dépassant la bande interdite de ces matériaux, leur décomposition s'accélère grâce à un processus de photocorrosion bien connu. La sensibilité de la photoluminescence (PL) des semi-conducteurs à la présence d’états de surface a fait l’objet des études approfondies pendant de nombreuses années. Cependant, ce n'était que récemment qu’il a été démontré que les mesures de PL étaient sensibles à la photocorrosion in situ avec une précision de sous-monocouche. Une conséquence importante de ces caractéristiques est la forte sensibilité de PL à la perturbation d'un champ électrique proche de la surface et au transfert de la charge électrique. Ceci a rendu la photocorrosion des nano-hétérostructures de GaAs/AlGaAs attrayante, en tant que transducteur propice, pour détecter les perturbations de la charge électrique proche de surface induite par les bactéries chargées négativement. Dans cette thèse, les mécanismes de dissolution des semi-conducteurs III-V photo-induits ont été étudiés en réalisant une spectrométrie de masse à plasma à couplage inductif (ICP-MS) de produits aqueux de photocorrosion. Les expériences réalisées pour la photocorrosion de nano-hétérostructures GaAs/Al0.35Ga0.65As dans des milieux DI H2O et NH4OH ont confirmé que la photocorrosion digitale (DIP) de ces nano-hétérostructures pouvait être contrôlée avec une précision inférieure à la monocouche. Les conditions conduisant à une décomposition congruente, définie par un taux de photocorrosion constant, ont été étudiées avec des mesures ICP-MS et un ensemble de méthodes de caractérisation de surface/interface utilisant FTIR, XPS et AFM. Cela a permis de démontrer que, contrairement à l'environnement DI H2O, l'environnement NH4OH conduit à la formation des surfaces stœchiométriques des nano-hétérostructures étudiées, d'au moins 100 nm. Le taux de photocorrosion constant a également été observé in situ en analysant les positions temporelles des interfaces révélées par PL entre les couches de GaAs et d'AlGaAs. Ces résultats démontrent la faisabilité d'un procédé simple et relativement peu coûteux pour le diagnostic in situ de la gravure par couche atomique de semi-conducteurs composés qui pourrait conduire à la formation de surfaces stœchiométriques de tels matériaux. L'étude de la photocorrosion digitale a été étendue à l'étude de ce processus pour la détection sensible de Legionella pneumophila chargée électriquement en milieu aqueux. L'immobilisation efficace de ces bactéries sur la surface du biocapteur a été confirmée avec une biopuce GaAs/AlGaAs polarisée électriquement. Ainsi, l’hypothèse principale proposée est que la décoration de L. pneumophila avec des biomolécules chargées négativement devrait mener à une détection à base de la photocorrosion digitale avec une limite de détection améliorée. En concordance avec les mesures du potentiel zêta, la bactérie L. pneumophila décoré avec du dodécylsulfate de sodium (SDS) a montré une interaction beaucoup plus forte avec les biopuces GaAs/AlGaAs photo-corrodées, ce qui a permis de détecter ces bactéries dans une solution saline tamponnée au phosphate (PBS) à 103 UFC/ml (unités formant colonies). Les résultats de cette recherche permettent de mieux comprendre la capacité du processus DIP à identifier les conditions conduisant à la formation de surfaces stœchiométriques de semi-conducteurs gravés. De plus, cette thèse contribue au développement d'une méthode innovante de détection de molécules chargées électriquement dans des environnements liquides

Engineering Biodegradable and Biocompatible Bio-ionic Liquid Conjugated Hydrogels with Tunable Conductivity and Mechanical Properties

Conventional methods to engineer electroconductive hydrogels (ECHs) through the incorporation of conductive nanomaterials and polymers exhibit major technical limitations. These are mainly associated with the cytotoxicity, as well as poor solubility, processability, and biodegradability of their components. Here, we describe the engineering of a new class of ECHs through the functionalization of non-conductive polymers with a conductive choline-based bio-ionic liquid (Bio-IL). Bio-IL conjugated hydrogels exhibited a wide range of highly tunable physical properties, remarkable in vitro and in vivo biocompatibility, and high electrical conductivity without the need for additional conductive components. The engineered hydrogels could support the growth and function of primary cardiomyocytes in both two dimentinal (2D) and three dimensional (3D) cultures in vitro. Furthermore, they were shown to be efficiently biodegraded and possess low immunogenicity when implanted subcutaneously in rats. Taken together, our results suggest that Bio-IL conjugated hydrogels could be implemented and readily tailored to different biomedical and tissue engineering applications

Wafer-scale detachable monocrystalline Germanium nanomembranes for the growth of III-V materials and substrate reuse

Germanium (Ge) is increasingly used as a substrate for high-performance optoelectronic, photovoltaic, and electronic devices. These devices are usually grown on thick and rigid Ge substrates manufactured by classical wafering techniques. Nanomembranes (NMs) provide an alternative to this approach while offering wafer-scale lateral dimensions, weight reduction, limitation of waste, and cost effectiveness. Herein, we introduce the Porous germanium Efficient Epitaxial LayEr Release (PEELER) process, which consists of the fabrication of wafer-scale detachable monocrystalline Ge NMs on porous Ge (PGe) and substrate reuse. We demonstrate monocrystalline Ge NMs with surface roughness below 1 nm on top of nanoengineered void layer enabling layer detachment. Furthermore, these Ge NMs exhibit compatibility with the growth of III-V materials. High-resolution transmission electron microscopy (HRTEM) characterization shows Ge NMs crystallinity and high-resolution X-ray diffraction (HRXRD) reciprocal space mapping endorses high-quality GaAs layers. Finally, we demonstrate the chemical reconditioning process of the Ge substrate, allowing its reuse, to produce multiple free-standing NMs from a single parent wafer. The PEELER process significantly reduces the consumption of Ge during the fabrication process which paves the way for a new generation of low-cost flexible optoelectronics devices.Comment: 17 pages and 6 figures along with 3 figures in supporting informatio

Photo Atomic Layer Etching of GaAs/AlGaAs Nanoheterostructures

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Electrically biased GaAs/AlGaAs heterostructures for enhanced detection of bacteria

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Optimized duplicated-junction solar cells: An innovative approach for energy harvesting at ultra-high concentrations

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Principal Component Analysis Of Anthropometric and Biomechanical Variables In Adolescent Elite Karateka Athletes

Objective: Despite the importance of identifying people susceptible to sports, there is little documentation and studies related to karate talent identification.The purpose of this study was principal component analysis of anthropometric and biomechanical variables in adolescent elite karateka athletes. Methods: Subjects divided to adolescent elite karateka athletes (n = 19) and non-karateka athletes adolescent (n=20) by convenience sampling method. Besed on the previous literature, some  biomechanical and anthropometric variables including subcutaneous layeres, circumference and length of the limbs, limb velocity, agility, balance and strength of the limbs was selected and measured. The principal component analysis (PCA) was performed to reduce the number of variables and identify the principal component Analysis anthropometric and biomechanical variables. Results: The results of this study showed that the most important anthropometric and biomechanical variables of adolescent elite karate athletes were thoracic subcutaneous fat, height, Sarjent jumping, static balance, handgrip relative strength, chest circumference, ankle circumference, dynamic  balance, abdominal subcutaneous fat and apparent leg length. Conclusion: According to the results of the present study, the extracted anthropometric and biomechanical characteristics can be used for identifiying the talent karateka athletes. &nbsp

Cost‐effective energy harvesting at ultra‐high concentration with duplicated concentrated photovoltaic solar cells

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Modeling of the photoluminescence monitored photocorrosion of GaAs/AlGaAs nano-heterostructures

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