>Magister Scientiae - MSc / In this study PbSe quantum dots (QDs) were successfully synthesized via the organometallic and aqueous routes. Optical characterization was carried out using photoluminescence (PL) spectroscopy, structural and morphological characterization were carried out using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Energy-dispersive X-ray spectroscopy (EDS) was used to determine the composition of the QDs. All the synthesized QDs were found to have emissions within the near-infrared region of the spectrum (≥1000 nm) with most of them being less than 5 nm in size. The aqueous synthesized QDs had a perfect Gaussian emission spectrum with a FWHM of ~23 nm indicating pure band gap emission and narrow size distribution respectively. The QDs were determined to have a cubic rock-salt crystal structure consistent with bulk PbSe. The aqueous synthesized QDs were however not stable in solution with the QDs precipitating after approximately 48 h. The organometallic synthesized QDs were transferred into the aqueous phase by exchanging the surface oleic acid ligands with 11-mercaptoundecanoic acid ligands. The ligand exchanged QDs were however stable in solution for over two weeks. The effects of reaction parameters on the optical and structural properties of the organometallic synthesized QDs were investigated by varying the reaction time, temperature, ligand purity, lead and selenium sources. It was observed that larger QDs were formed with longer reaction times, with reactions proceeding faster at higher reaction temperatures than at lower temperatures. Varying the ligand purity was found to have minimal effects on the properties of the synthesized QDs. The lead and selenium sources contributed largely to the properties of the QDs with lead oxide producing spherical QDs which were smaller compared to the cubic QDs produced from lead acetate. TBPSe was seen to produce smaller QDs as compared to TOPSe. The cytotoxity of the synthesized QDs was determined following the WST-1 cell viability assay with the QDs being found to be non-toxic at all the tested concentrations

Les mono-couches auto-assemblées (SAMs) sont des systèmes de choix pour le développement de plateformes moléculaires aux propriétés physico-chimiques contrôlées. Il s’agit de monocouches organisées de molécules bi-fonctionnelles. Ces molécules se composent d’une fonction terminale modulable, séparée d’un groupement d’ancrage par un espaceur adapté. Ainsi, les propriétés des SAMs peuvent être ajustées pour le développement de systèmes électroniques moléculaires ou de capteurs (bio)-chimiques. De plus, des structurations chimiques supplémentaires peuvent être induites par irradiation.Les méthodes d’irradiation les plus courantes impliquent des particules de haute énergie. Les dommages induits résultent de plusieurs mécanismes en compétition (ionisations, excitations, dissociations). Dans cette thèse, les électrons lents (0-20 eV) sont utilisés comme particules primaires, et les processus d’interaction électron-SAM sont étudiés afin d’identifier les résonances d’attachement électronique. Aux énergies concernées, des processus dissociatifs sélectifs et efficaces peuvent être mis à profit pour proposer des stratégies d’irradiation menant à des modifications chimiques contrôlées et optimisées.Des SAMs modèles de thiols sur or sont étudiées par une technique de spectroscopie vibrationnelle de forte sensibilité de surface, la spectroscopie de perte d’énergie d’électrons lents (HREELS). Elle permet à la fois de caractériser les SAMs et de sonder les processus d'interaction électron-molécule. Les résultats obtenus concernent les : 1) SAMs aromatiques modèles de terphénylthiol (HS-(C₆H₄)₂-C₆H₅), stabilisables par réticulation sous irradiation. Une caractérisation vibrationnelle poussée de la SAM avant et après irradiation, en portant une attention particulière au comportement des modes d’élongation ν(CH), a permis d’opposer les processus de réactivité induite à 1, 6 et 50 eV.2) SAMs d’acide mercaptoundécanoïque (HS-(CH₂)₁ ₀ -COOH), les fonctions acides terminales permettant par exemple le greffage de peptides. L’interface SAM / environnement (COO-/COOH, eau résiduelle) a été caractérisée grâce à la forte sensibilité des modes d’élongation ν(OH) aux liaisons hydrogène. La démarche mise en place peut être facilement transposée à d’autres systèmes. / Self-Assembled Monolayers (SAMs) are good candidates to develop molecular platforms with controlled physico-chemical properties. A SAM is an ordered monolayer of bi-functionnal molecules. These molecules consist of an adjustable terminal function, separated from a headgroup by a chosen spacer chain. Thus, SAMs properties can be adjusted for the development of molecular electronic systems or (bio)-chemical sensors. Furthermore, additional chemical structuration can be induced by irradiation.Most current methods of irradiation involve high energy particles. The induced damages result from several competitive mechanisms (ionisations, excitations, dissociations). In this thesis, low energy electrons (0-20 eV) are used as primary particles, and the interaction processes between electrons and SAMs are studied in order to identify electron attachment resonances. At the associated energies, selective and effective dissociative processes can be induced to propose irradiation strategies leading to controlled and optimized chemical modifications.Model SAMs of thiols on gold are studied by a vibrational spectroscopy technique of strong surface sensibility, high resolution electron energy loss spectroscopy (HREELS). It allows at the same time to characterize SAMs and to probe electron-molecule interaction processes. The result obtained deal with : 1) Aromatic model SAMs of Terphenyl-thiol (HS-(C₆H₄)₂-C₆H₅), which can be stabilized by cross-linking under irradiation. Induced reactive processes at 1, 6 and 50 eV were compared and opposed, thanks to an advanced vibrational characterization of the SAM before and after irradiation, and by paying a particular attention to the stretching mode ν(CH) behaviour.2) Mercaptoundecanoic acid SAMs (HS-(CH₂)₁ ₀ -COOH), whose terminal functions allow for example the peptide anchoring. The interface SAM / environment (COO-/COOH, residual water) was characterized thanks to the strong sensitivity of the stretching modes ν(OH) to hydrogen bonding. The approach that was developped can be easily transposed to other systems.