In this study, Fe₃O₄/Ag magnetite-silver (MSx) nanocomposites were investigated as catalysts for advanced oxidation processes by coupling the plasmonic effect of silver nanoparticles and the ferromagnetism of iron oxide species. A surfactant-free co-precipitation synthesis method yielded pure Fe₃O₄ magnetite and four types of MSx nanocomposites. Their characterisation included structural, compositional, morphological and optical analyses, revealing Fe₃O₄ magnetite and Ag silver phases with particle sizes ranging from 15 to 40 nm, increasing with the silver content. The heterostructures with silver reduced magnetite particle aggregation, as confirmed by dynamic light scattering. The UV–Vis spectra showed that the Fe:Ag ratio strongly influenced the absorbance, with a strong absorption band around 400 nm due to the silver phase. The oxidation kinetics of organic pollutants, monitored by in situ luminescence measurements using rhodamine B as a model system, demonstrated the higher performance of the developed catalysts with increasing Ag content. The specific surface area measurements highlighted the importance of active sites in the synergistic catalytic activity of Fe₃O₄/Ag nanocomposites in the photo-Fenton reaction. Finally, the straightforward fabrication of diverse Fe₃O₄/Ag heterostructures combining magnetism and plasmonic effects opens up promising possibilities for heterogeneous catalysis and environmental remediation.

This study investigates the inhibition of asphaltene precipitation using alumina–iron nanocomposite (NCP). Al:Fe NCP, successfully synthesized from pure aluminum and iron chloride, is crystalline mixture of hematite and alumina phases with a purity of 99%. Decreasing the content in hematite lowers the particle size from ∼60 to 10 nm. To evaluate the inhibition potential of Al:Fe, a series of experiments consisting of the addition of Al:Fe NCP into a model crude oil followed by a precipitation using n-heptane were conducted. The model oil was a solution consisting of 3 mg of asphaltene extracted from a dead Middle Eastern heavy oil (29.2^oAPI) dissolved into 10 g of toluene. 35 vol. % of heptane was required to precipitate asphaltene from the model crude oil. Hereinafter termed as asphaltene onset precipitation (AOP), adding 0.05 wt.% Al:Fe NCP to the model oil requires up to 30 mL of heptane to precipitate the same amount of asphaltenes. The increase in molar ratio in alumina decreases AOV up to 63.5%. The spectral studies revealed that the inhibition of asphaltene precipitation involves both the polar interactions of alumina phase with asphaltene and the decrease of the π–π stacking interaction upon addition of NCPs.

Iron oxide nanoparticles were synthesized by the chemical precipitation method at 25 and 80 °C using polyvinylpyrrolidone (PVP) and aloe vera/polyvinyl pyrrolidone (AP) as capping agents. FTIR bands at 1584-1455 and 522-561 cm-1 confirm the formation of PVP- and AP-capped iron oxide nanoparticles. The formation of magnetite and hematite phases was confirmed by powder X-ray Diffraction patterns. The elemental composition of the synthesized particles was confirmed by EDX. SEM analysis revealed a mixed morphology of spherical and irregular-shaped particles of average crystallite sizes ranging from 9 to 58 nm, as estimated from XRD and SEM measurements. Both PVP- and AP-capped nanoparticles were used as catalysts for the photocatalytic degradation of methylene blue under ultraviolet (UV) irradiation. After 180 min of irradiation with 20 mg of photocatalyst, degradation efficiencies of 53-82% were obtained, with AP-capped nanoparticles being more efficient, suggesting their potential as effective materials for the photocatalytic degradation of toxic dyes in wastewater.

The dinuclear compound, [Mn2(Pyala)2(Dca)2(H2O)]n·2H2O (1) (Pyala = N-(2-pyridylmethyl)-L-alanine and Dca = dicyanamide anion) has been synthesized and characterized by elemental analysis, IR and single crystal X-ray diffraction techniques. The crystal data for C22H26Mn2N10O6: orthorhombic, space group P212121 (no. 19), a = 10.3728(8) Å, b = 15.9780(12) Å, c = 16.3585(13) Å, V = 2711.2(4) Å3, Z = 4, T = 198(2) K, μ(MoKα) = 0.989 mm-1, Dcalc = 1.559 g/cm3, 129607 reflections measured (3.564° ≤ 2Θ ≤ 60.046°), 7923 unique (Rint = 0.0324, Rsigma = 0.0155) which were used in all calculations. The final R1 was 0.0169 (I > 2σ(I)) and wR2 was 0.0458 (all data). The obtained non-centrosymmetric dinuclear Mn(II) complex contains two unique Mn(II) cations with similar octahedral coordination environment. Photoluminescent measurements on the complex in the solid state show that it displays strong photoluminescence at 442 nm.

List of contributors was published in Nanostructured Materials on page XIII.

Ce travail de thèse visait la conception de marqueurs à base d’ions lanthanides pour le diagnosticprécoce de la maladie d’Alzheimer, à travers un transfert d’énergie avec des nanocristaux semi- conducteurs luminescents. Notre choix s’est porté sur des ligands polyaminophosphonatés de type pyridine-bis-pyrazolyl rendus réactifs vis-à-vis des biomolécules par la présence de groupements activés. Nous présentons la synthèse d’un ligand modèle incorporant seulement l’unité de photosensibilisation tridentate et des groupes phosphonatés. À partir de ce ligand, les complexes d’europium et de terbium synthétisés ont été caractérisés. Une grande stabilité et des propriétés de luminescence avantageuses ont été mises en évidence par nos études, notamment en ce qui concerne le complexe de terbium. Une méthode synthèse de ligands de ce type, fonctionnalisés par la présence de groupements réactifs a été développée et le marquage de biomolécules dont des marqueurs de la maladie d’Alzheimer a été réalisé avec succès. La synthèse d’un autre ligand phosphonaté associé de façon covalente à la biotine et l’utilisation de son complexe de terbium comme donneur d’énergie a permis de réaliser des expériences de transfert d’énergie avec divers accepteurs luminescents dont des nanocristaux semi-conducteurs.