O presente trabalho apresenta a síntese e a caracterização de derivados de quitosana, bem como o preparo e caracterização de filmes de nanocompósitos à base de quitosana comercial (ou seus derivados), argila (MMT) e nanopartículas de prata (NPs-Ag), obtidas via Fotoquímica. Para tanto, foram preparados, a partir da quitosana comercial (QC), os derivados: quitosana desacetilada (Q30des), quitosana purificada (QP), quitosanas parcialmente despolimerizas (QD30, QD21 e QD5), quitosanas hidrofílicas (QD21-40DEAE e QD5-49DEAE) e quitosanas anfifílicas (QD21-40DEAE-6DD, QD21-40DEAE-18DD, QD5-49DEAE-6DD e QD5-49DEAE-17DD). O grau médio de desacetilação das QC, QP e Q30des e de substituição por grupos DEAE e dodecila foram determinados por Espectroscopia de Ressonância Magnética Nuclear de Hidrogênio (RMN de 1H). Ademais, os biopolímeros foram caracterizados por Espectroscopia no Infravermelho (FTIR-ATR), Viscosimetria, Análise Termogravimétrica e Microscopia Eletrônica de Varredura (MEV). Em seguida, foi estudada a síntese de nanopartículas de prata, sob radiação UV, em filmes de nanocompósitos de quitosana comercial ou seus derivados e argila. Em um primeiro momento, estudou-se a formação das NPs-Ag em filmes de QC com diferentes formulações e posteriormente em filmes de derivados de quitosana contendo 10% de MMT (m/m). A técnica de Difração de Raios-X (DRX) foi utilizada para a determinação do espaçamento interlamelar da argila montmorilonita pura e nos compósitos preparados. A síntese das NPs-Ag foi acompanhada por Espectrofotometria de Absorção Molecular no UV-vis, e monitorada após um ano de sua formação, sendo suas características morfológicas, bem como a dispersão da argila nos nanocompósitos examinados por Microscopia Eletrônica de Transmissão (MET). Por fim, a atividade antimicrobiana dos filmes de nanocompósitos foi avaliada pelo método de Disco de Difusão contra as bactérias Escherichia coli e Bacillus subtilis. / The present work presents the synthesis and characterization of chitosan derivatives, as well as the preparation and characterization of nanocomposite films based on commercial chitosan (or its derivatives), clay (MMT) and silver nanoparticles (NPs-Ag) obtained by photochemical method. Therefore, were prepared from commercial chitosan (QC): deacetylated chitosan (Q30des); purified chitosan (QP); partially depolymerized chitosans (QD30, QD21 and QD5); hydrophilic chitosans (QD21-40DEAE and QD5-QD5) and amphiphilic chitosans (QD21-40DEAE-6DD, QD21-40DEAE-18DD, QD5-49DEAE-6DD and QD5-49DEAE-17DD). The deacetylation degrees of QC, QP and Q30des were determined by Nuclear Magnetic Resonance Spectroscopy (1H-NMR). This technique also used to determine the degrees of substitution by DEAE and dodecyl groups. In addition, the biopolymers were characterized by Infrared Spectroscopy (FTIR-ATR), Viscosimetry, Thermogravimetry and Scanning Electron Microscopy. Moreover, the NPs-Ag synthesis under UV radiation was studied on nanocomposite films of commercial chitosan or its derivatives and clay. At first, the Ag-NPs formation was studied on QC films with different formulations and secondarily, on films of chitosan derivatives containing 10 wt % of MMT. The X-Ray Diffraction (XRD) was used to determine the interlamellar spacing of pure montmorillonite clay and in the nanocomposites prepared. The synthesis of the NP-Ag was accompanied by UV-vis Spectroscopy. Its morphological characteristics, as well as the clay dispersion in the nanocomposites were examined by Electron Transmission Electron Microscopy (TEM). Finally, the antimicrobial activities of materials were investigated by the disk diffusion method against the bacteria Escherichia coli e Bacillus subtilis.

O presente trabalho apresenta a síntese e a caracterização de derivados de quitosana, bem como o preparo e caracterização de filmes de nanocompósitos à base de quitosana comercial (ou seus derivados), argila (MMT) e nanopartículas de prata (NPs-Ag), obtidas via Fotoquímica. Para tanto, foram preparados, a partir da quitosana comercial (QC), os derivados: quitosana desacetilada (Q30des), quitosana purificada (QP), quitosanas parcialmente despolimerizas (QD30, QD21 e QD5), quitosanas hidrofílicas (QD21-40DEAE e QD5-49DEAE) e quitosanas anfifílicas (QD21-40DEAE-6DD, QD21-40DEAE-18DD, QD5-49DEAE-6DD e QD5-49DEAE-17DD). O grau médio de desacetilação das QC, QP e Q30des e de substituição por grupos DEAE e dodecila foram determinados por Espectroscopia de Ressonância Magnética Nuclear de Hidrogênio (RMN de 1H). Ademais, os biopolímeros foram caracterizados por Espectroscopia no Infravermelho (FTIR-ATR), Viscosimetria, Análise Termogravimétrica e Microscopia Eletrônica de Varredura (MEV). Em seguida, foi estudada a síntese de nanopartículas de prata, sob radiação UV, em filmes de nanocompósitos de quitosana comercial ou seus derivados e argila. Em um primeiro momento, estudou-se a formação das NPs-Ag em filmes de QC com diferentes formulações e posteriormente em filmes de derivados de quitosana contendo 10% de MMT (m/m). A técnica de Difração de Raios-X (DRX) foi utilizada para a determinação do espaçamento interlamelar da argila montmorilonita pura e nos compósitos preparados. A síntese das NPs-Ag foi acompanhada por Espectrofotometria de Absorção Molecular no UV-vis, e monitorada após um ano de sua formação, sendo suas características morfológicas, bem como a dispersão da argila nos nanocompósitos examinados por Microscopia Eletrônica de Transmissão (MET). Por fim, a atividade antimicrobiana dos filmes de nanocompósitos foi avaliada pelo método de Disco de Difusão contra as bactérias Escherichia coli e Bacillus subtilis. / The present work presents the synthesis and characterization of chitosan derivatives, as well as the preparation and characterization of nanocomposite films based on commercial chitosan (or its derivatives), clay (MMT) and silver nanoparticles (NPs-Ag) obtained by photochemical method. Therefore, were prepared from commercial chitosan (QC): deacetylated chitosan (Q30des); purified chitosan (QP); partially depolymerized chitosans (QD30, QD21 and QD5); hydrophilic chitosans (QD21-40DEAE and QD5-QD5) and amphiphilic chitosans (QD21-40DEAE-6DD, QD21-40DEAE-18DD, QD5-49DEAE-6DD and QD5-49DEAE-17DD). The deacetylation degrees of QC, QP and Q30des were determined by Nuclear Magnetic Resonance Spectroscopy (1H-NMR). This technique also used to determine the degrees of substitution by DEAE and dodecyl groups. In addition, the biopolymers were characterized by Infrared Spectroscopy (FTIR-ATR), Viscosimetry, Thermogravimetry and Scanning Electron Microscopy. Moreover, the NPs-Ag synthesis under UV radiation was studied on nanocomposite films of commercial chitosan or its derivatives and clay. At first, the Ag-NPs formation was studied on QC films with different formulations and secondarily, on films of chitosan derivatives containing 10 wt % of MMT. The X-Ray Diffraction (XRD) was used to determine the interlamellar spacing of pure montmorillonite clay and in the nanocomposites prepared. The synthesis of the NP-Ag was accompanied by UV-vis Spectroscopy. Its morphological characteristics, as well as the clay dispersion in the nanocomposites were examined by Electron Transmission Electron Microscopy (TEM). Finally, the antimicrobial activities of materials were investigated by the disk diffusion method against the bacteria Escherichia coli e Bacillus subtilis.

Cette thèse porte sur la croissance de films minces d’oxydes de zinc/fer (ZnxFe1-xO1+δ par ablation laser pulsée (PLD) et sur la possibilité de contrôler leurs propriétés structurales et physico-chimiques en variant les conditions d’élaboration : pression d’oxygène et température de croissance, proportions respectives de zinc/fer. Pour de fortes valeurs de x (x > 65%), les films sont monophasés de structure wurtzite type ZnO (films Fe:ZnO), avec une transparence optique dans la gamme UV-visible de 80% mais sans propriété ferromagnétique ; en fonction de leur teneur en fer (1-x), ils évoluent de très bons conducteurs électriques à quasi-isolants. Pour de faibles valeurs de x (x < 15%), les films sont également monophasés de structure spinelle type Fe3O4 (films Zn:Fe3O4). Ils présentent de très bonnes propriétés ferromagnétiques dès la température ambiante ainsi qu’une bonne conductivité électrique, les effets de localisation des porteurs de charge se manifestant en dessous de la température de Verwey. Le nombre de parois d’antiphase peut être diminué par une croissance en deux étapes, comme l’atteste les mesures de magnétorésistance. Aux taux intermédiaires de zinc (15% < x < 65%), les films sont nano-composites. Dans le cas d’une coexistence des phases Fe:ZnO et Zn:Fe3O4, la bonne conductivité de Zn:Fe3O4 jointe à la multiplicité des variantes épitaxiales et donc des interfaces fournit un matériau adapté à la thermoélectricité. Dans le cas d’une coexistence de la phase ferrromagnétique Zn:Fe3O4 avec la phase Zn:FeO antiferromagnétique de type sel gemme, un fort couplage d’échange ainsi qu’une anisotropie magnétique perpendiculaire élevée sont mis en évidence. / This thesis deals with the growth of thin films of zinc/iron oxides (ZnxFe1-xO1+δ) by pulsed laser deposition (PLD) and the possibility of controlling their structural and physicochemical properties by varying the elaboration conditions: oxygen pressure and growth temperature, respective proportions of zinc/iron. For high values of x (x> 65%), the films are single-phase with a ZnO-type wurtzite structure (Fe:ZnO films), with 80% optical transparency in the UV-visible range but without ferromagnetic properties; depending on their iron (1-x) content, they evolve from very good electrical conductors to near-insulators. For small values of x (x <15%), the films are also single-phase with a Fe3O4-type spinel structure (Zn:Fe3O4 films). They exhibit very good ferromagnetic properties at ambient temperature as well as good electrical conductivity, the localization effects of charge carriers occurring below the Verwey temperature. The number of antiphase walls can be decreased by a two-step growth, as evidenced by magnetoresistance measurements. At intermediate zinc rates (15% <x <65%), the films are nano-composites. In the case of a coexistence of the Fe:ZnO and Zn:Fe3O4 phases, the good conductivity of Zn:Fe3O4 combined with the multiplicity of epitaxial variants and thus of the interfaces provides a material suitable for thermoelectricity. In the case of a coexistence of the ferrromagnetic Zn:Fe3O4 phase with the Zn:FeO antiferromagnetic rocksalt phase, strong exchange coupling as well as high perpendicular magnetic anisotropy are demonstrated.