The aim of this research was to prepare high performance and fully biodegradable polymer nanocomposites. The most representative polymers classified as biodegradable are poly(!-caprolactone) (PCL) (issued from petrochemistry) and polylactide (PLA) (issued from renewable bio-resources). Biodegradable nanoparticles purposely extracted from biomass were selected, namely Cellulose NanoWhiskers (CNW) and Starch NanoCrystals (SNC). CNW are rod-like nanoparticles with 2 nanometric dimensions while SNC consists in nanosheets, thus with 1 nanometric dimension. A 3 nanometric-dimension particle often considered as “silica- type nanocage” was selected to complete this study, namely Polyhedral Oligomeric Silsesquioxane (POSS). The addition of such nanoparticles was expected to enhance several properties of the filled polymer matrix, especially thermo-mechanical performances and extent of crystallinity. In this field, the quality of the nanoparticle dispersion throughout the matrix is an essential parameter to produce nanocomposite materials with largely improved properties. One of the most cited techniques to overcome nanofiller aggregation and even agglomeration relies upon the creation of strong chemical bonds between the nanoparticle and the polymer matrix, leading to the preparation of so-called nanohybrids. For that purpose, the surface of the nanoparticles was first modified by chemical grafting and polymerization reactions. The ring-opening polymerization (ROP) of e-caprolactone and L,L-lactide catalyzed by tin(II) 2- ethylhexanoate (tin octoate, Sn(Oct)2) was initiated from functional groups available on the nanoparticle surface. The grafting efficiency was demonstrated for the three investigated nanofiller/polyester systems. Different characterization techniques were approached depending on the nanofiller nature. In a second step, the so-formed nanohybrids were used as “masterbatches” and dispersed in their corresponding commercial polyester matrices, i.e. PCL and PLA, by melt-compounding using a mini-lab twin screw extruder. The nanocomposite materials were fully characterized, correlating morphological observations with thermal, mechanical and rheological properties. To highlight the beneficial effect of the surface covalent grafting, simple melt-blends, i.e., containing unmodified nanofillers and polyester matrices (PCL or PLA) were prepared. The level of property improvement was most of the time directly related to the degree of nanofiller dispersion, and proved systematically better in case of masterbatch-based materials. Keeping in mind the effect of the nanoparticle geometry, as well as its mechanical modulus, crystallinity or extent of dispersion within the polyester matrix, the rod-like 2D-nanofiller, namely cellulose nanowhiskers extracted from ramie, appeared as the most efficient candidate for polyester reinforcement. The incorporation of PCL chains surface-grafted onto CNW contributed to substantially increasing the overall thermo- mechanical properties, most likely due to the formation of a strong physical chain network between surface- grafted chains and chains composing the matrix. Additionally, CNW-based nanohybrids revealed their potential as both nucleating sites dramatically increasing the crystallization rate of PLA matrix and compatibilizing PCL/PLA immiscible blends.

A combinação de nanopartículas de dióxido de titânio com nanotubos de carbono de parede múltiplas possibilita a geração de um nanomaterial híbrido, com atividade fotocatalítica aprimorada, denominado TiO2-MWCNT. Existe um grande interesse científico e tecnológico em materiais fotocatalíticos, estes apresentam potencial para o desenvolvimento de novos agentes antimicrobianos, nanocompósitos, catalisadores e remediação ambiental. Apesar de muitos trabalhos enfatizarem os benefícios na utilização de nanohíbridos, ainda são escassos estudos de impactos ambientais e toxicidade. O objetivo deste trabalho foi sintetizar e caracterizar o nanohíbrido TiO2-MWCNT, bem como avaliar sua ecotoxicidade aquática através de ensaios in vivo (embriões de Zebrafish - Danio rerio) e in vitro (linhagem celular RTG-2 - fibroblastos de Oncorhynchus mykiss). O TiO2-MWCNT foi sintetizado pelo método mecanoquímico (moagem em estado sólido) e caracterizado empregando as seguintes técnicas: microscopia eletrônica de varredura e de transmissão, espectroscopia Raman, análise termogravimétrica, espalhamento dinâmico de luz e espalhamento de luz eletroforético. O nanohíbrido sintetizado apresentou atividade fotocatalítica aprimorada, confirmada através de ensaios de fotocatálise. Nos ensaios in vivo, o TiO2-MWCNT não apresentou ecotoxicidade aguda até 100 µg mL-1 (na presença ou ausência de radiação UV). No entanto, foi observada a ingestão do nanohíbrido pelos embriões (via oral) através da técnica microfluorescência de raios-X (µ-XRF). Também não foi observado ecotoxicidade para o nanohíbrido nos ensaios in vitro até 100 µg mL-1; porém foi verificado a capacidade de internalização celular deste material. Em geral, aspectos coloidais (agregação/aglomeração) e a formação de protein corona apresentaram importantes implicações para a determinação precisa da ecotoxicidade. Os resultados obtidos neste trabalho suportam futuras aplicações do nanohíbrido TiO2-MWCNT na área de fotocatálise, e contribui de maneira proativa para sua avaliação ecotoxicológica / The combination of titanium dioxide nanoparticles with multiwall carbon nanotubes enables the generation of a hybrid nanomaterial with improved photocatalytic activity, called TiO2-MWCNT. There is great scientific and technological interest in photocatalytic materials, which present potential for the development of new antimicrobial agents, nanocomposites, catalysts and environmental remediation. Although many papers emphasize the benefits of using nanohybrids, there are still a small number of studies about its environmental impacts and toxicity. The objective of this work was to synthesize and characterize a TiO2-MWCNT nanohybrid. As well as to evaluate its aquatic ecotoxicity through in vivo (Zebrafish embryos - Danio rerio) and in vitro (RTG-2 cell line - Oncorhynchus mykiss fibroblasts) assays. TiO2-MWCNT was synthesized by the mechanochemical method (solid state milling) and characterized using the following techniques: scanning and transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis, dynamic scattering light and electrophoretic scattering light. The synthesized nanohybrid showed enhanced photocatalytic activity, confirmed by photocatalysis studies. In the in vivo assays, TiO2-MWCNT did not show acute ecotoxicity up to 100 ?g mL-1 (in the presence or absence of UV radiation). However, the ingestion of the nanohybrid by the embryos (oral route) was observed through ?-probe X-ray fluorescence spectroscopy (?-XRF). Also, no toxicity was observed in the in vitro assays up to 100 ?g mL-1; however, the cellular internalization capacity of this material was verified. In general, colloidal aspects (aggregation / agglomeration) and the formation of protein corona presented important implications for the precise determination of ecotoxicity. The results obtained in this work support future applications of the nanohybrid TiO2-MWCNT in the area of photocatalysis and contributes proactively to its ecotoxicological evaluation

Bio-nanohybrid materials based on the combination of biomolecules and inorganic supports are interesting by their versatile applications in regenerative medicine, drug delivery, bio-engineering and catalysis. In that context, understanding of organic/inorganic interactions offers an important key to design new and more complex bio-systems with modified interactions. In this thesis, amino acids and synthesised poly-amino acids were immobilised in hydrotalcite-like materials under green, controllable and efficient protocols. Additionally, these nanohybrid materials were used as heterogenized catalysts exhibiting high catalytic activity and selectivity in comparison with their counterpart components. All result data showed that the location and nature of the immobilization had an important role in the final chemical properties; moreover, this novel bio-nanohybrid material exhibited excellent synergistic behaviour which was unique for each material and could be modified according with the reaction requirements. All novel bio-nanohybrid materials were easily synthesised, recovered and, in some cases, reused without appreciable deactivation. / Materiales bio-nanohíbridos compuestos por la combinación de biomoléculas y soportes inorgánicos son interesantes por sus versátiles aplicaciones en medicina regenerativa, transporte de medicamentos, bio-ingeniería y catálisis. En este contexto, el entendimiento de las interacciones orgánico/inorgánicas ofrece importante información para el diseño de nuevos y más complejos bio-sistemas con interacciones modificadas. En esta tesis, amino ácidos y poli-amino ácidos sintéticos fueron inmovilizados en materiales tipo hidrotalcita a través de eficientes y controlables protocolos amigables con el medioambiente. Adicionalmente, estos materiales fueron usados como catalizadores heterogeneizados mostrando alta actividad y selectividad en comparación con sus componentes de partida. En este sentido, la localización y naturaleza de la interacción tuvo un importante rol en las propiedades catalíticas finales; además, estos novedosos materiales mostraron un excelente comportamiento sinérgico el cual fue único y pudo ser modificado de acuerdo a las necesidades en reacción. Todos los materiales bio-nanohíbirdos fueron sintetizados y recuperados con facilidad del medio de reacción y en algunos casos fueron reutilizados sin desactivación apreciable.

Heavy metals are non-degradable and their persistence constitutes ecotoxicological ramifications. Their presence in wastewater is inhibitory to microbial digestion processes and can lead to biomagnification in the environment. Clay minerals have been widely studied as inexpensive sorbent materials of aqueous-phase contaminants. Particularly in the case of kaolinite, a non-swelling clay with a low cation-exchange capacity, chemically enhanced derivatives exposing its OH-rich interlayer space to interactions with its external environment are of exceptional interest. The objective of this study was to prepare a novel functionalised kaolinite with the aim of significantly improving its heavy-metal sorption capacity. Due to the robustness of sulfur-metal linkages, the compound 3,6-dithia-1,8-octanediol (HO(CH2)2S(CH2)2S(CH2)2OH) was grafted onto both urea- and DMSO precursors of two kaolinitic clays: the Source clay KGa-1b and a Portuguese clay sample collected from the Clays of Taveiro formation. All samples were characterised by X-ray diffraction and 13C nuclear magnetic resonance spectroscopy (NMR). Initial materials and final samples were also characterised by thermal gravimetric analysis and infrared spectroscopy. The results describe nanohybrid materials that are resistant to hydrolysis and exhibit different grafting fashions. Application as a heavy metal sorbent was tested in ZnCl2 solutions as well as in zinc-spiked raw wastewater. Zinc concentrations were analysed concomitant with other metal species by inductively coupled plasma – mass spectrometry, demonstrating variable sorption capacities of the different clay samples tested and a consistently greater zinc removal in the wastewater system compared to simple zinc solutions. Measured concentrations of concomitantly analysed metals reveals a potentially alarming release of certain heavy metal species from some clay samples as a result of zinc sorption.