Barium Titanate (BaTiO3 or BTO) has attracted an ever increasing research interest because of its wide range of potential applications. Nano-sized or nanostructured BTO has found applications in new, useful smart devices, such as sensors and piezoelectric devices. Not only limited to one material, multi-layers or multi-phases can lead to multifunctional applications; for example, nanocomposites can be fabricated with ferrite or metal phase with BTO. In this study, I synthesized various BTO-ferrites, ranging from nanoparticles, nanowires to thin films. BTO-ferrite coaxial nanotubes, BTO-ferrite self-assemble thin films, and BTO single phase films were prepared by pulsed laser deposition (PLD) and sol-gel process. BTO-ferrite nanocomposites were grown by solid state reaction. Furthermore, BTO-metal nanostructures were also synthesized by solid state reaction under hydrogen gas which gave us a great inspiration to fabricate metal-ceramic composites. To understand the relationship between metal and BTO ceramic phase, I also deposited BTO film on Au buffered substrates. A metal layer can affect the grain size and orientation in BTO film which can further help us to control the distribution of dielectric properties of BTO films. After obtaining different nanomaterials, I am interested in the applications of these materials. Recently, many interesting electric devices are developed based on nanotechnology, e.g.: memristor. Memristor is a resistor with memory, which is very important in the computer memory. I believe these newly-synthesized BTO based nanostructures are useful for development of memristor, sensors and other devices to fit increasing needs. / Ph. D.

O muco protege o corpo humano de partículas externas, mas também representa uma barreira para a entrega de controlada de medicamentos através de nanocarregadores. Para ultrapassar a barreira do muco e impedir mucoadesão, nanopartículas sólidas são normalmente revestidas com polímeros inertes, tais como o polietileno glicol (PEG). No entanto, trata-se de um procedimento relativamente complexa. Nesta tese, estudamos métodos para fabricar nanocarreadores com uma excepcional combinação de propriedades, incluindo uma boa capacidade de mucopenetração e uma grande capacidade de carga. Ao contrário dos métodos convencionais de revestimento, usamos um copolímero dibloco, que consiste em dois blocos hidrofóbicos e hidrofílicos, que se auto-organiza em polimerosomos sob hidratação. Devido à inércia do bloco hidrofílico, estes polimerosomos devem ser, por natureza, muco penetradores. Além disso, sua estrutura oca fornece os polimersomos para serem carregados com carga hidrofílica, enquanto a carga hidrofóbica pode ser transportada através da membrana. Por conta da utilização de um polímero hidrolisável na presença de ácido, ácido poli láctico (PLA) como a espinha dorsal copolímero, demonstramos que estes polimerosomos podem liberar o conteúdo, após aplicação do estímulos externo relacionado ao pH. Os experimentos de rastreamento de partículas demonstraram que os polimersomos se difundem mais rápido do que as partículas não revestidas, em muco de intestino de porco, e testes de biodistribuição apresentaram resultados encorajadores para a entrega localizada de fármacos de maneira mais homogênea, melhorando a biodisponibilidade e efeitos terapeuticos. Mais estudos relacionados ao aumento da eficiência de encapsulação e testes de efetividade in vivo no tratamento de doenças devem ser promovidos. Acreditarmos que combinação das vantagens relacionadas à estrutura vesicular dos polimerossomas, estabilidade, e muco penetração possibilitam o desenvolvimento de uma nova plataforma para a entrega controlada de medicamentos na mucosa. / Mucus protects the human body by trapping foreign particulates but also poses a barrier for drug delivery by slowing down the mobility of drug carriers. To design mucus penetrating carriers, solid particles are typically coated with inert polymers such as polyethylene glycol (PEG) to prevent mucoadhesion. However, the solid structure of these particles limits their loading capabilities and the process to coat them requires a complex synthesis. In this thesis we studied methods to fabricate nanocarriers with an exceptional combination of properties including a good mucus-penetration capability and loading capacity of hydrophilic and hydrophobic cargos. Unlike conventional coating methods, we use a diblock copolymer, consisting of both hydrophobic and hydrophilic blocks, which self-assembles into polymersomes under hydration. Because of the inertness of the hydrophilic block, these polymersomes should be mucus-penetrating by nature. Moreover, their hollow structure provides the polymersomes to be loaded with hydrophilic cargo, whereas hydrophobic cargo can be carried through the membrane. Importantly, by using a hydrolysable acid-catalyzed polymer (poly lactic acid, PLA) as the copolymer backbone, we demonstrate that these polymersomes can release contents upon application of external pH stimuli. Particle Tracking experiments demonstrated that polymersomes diffuse faster than uncoated particles in porcine intestine mucus, and biodistribution tests displayed encouraging results towards more homogeneous local drug-delivery, helping bioavailability as well as therapeutic efects. More studies related to the increase of encapsulation efficiency, and in vivo disease treatment tests should be promoted. Although we believe that combining the advantages of polymersome carrier, and tunning the membrane composition, this mucus-penetrating carrier we propose may provide as a new platform for mucosal drug delivery.

O muco protege o corpo humano de partículas externas, mas também representa uma barreira para a entrega de controlada de medicamentos através de nanocarregadores. Para ultrapassar a barreira do muco e impedir mucoadesão, nanopartículas sólidas são normalmente revestidas com polímeros inertes, tais como o polietileno glicol (PEG). No entanto, trata-se de um procedimento relativamente complexa. Nesta tese, estudamos métodos para fabricar nanocarreadores com uma excepcional combinação de propriedades, incluindo uma boa capacidade de mucopenetração e uma grande capacidade de carga. Ao contrário dos métodos convencionais de revestimento, usamos um copolímero dibloco, que consiste em dois blocos hidrofóbicos e hidrofílicos, que se auto-organiza em polimerosomos sob hidratação. Devido à inércia do bloco hidrofílico, estes polimerosomos devem ser, por natureza, muco penetradores. Além disso, sua estrutura oca fornece os polimersomos para serem carregados com carga hidrofílica, enquanto a carga hidrofóbica pode ser transportada através da membrana. Por conta da utilização de um polímero hidrolisável na presença de ácido, ácido poli láctico (PLA) como a espinha dorsal copolímero, demonstramos que estes polimerosomos podem liberar o conteúdo, após aplicação do estímulos externo relacionado ao pH. Os experimentos de rastreamento de partículas demonstraram que os polimersomos se difundem mais rápido do que as partículas não revestidas, em muco de intestino de porco, e testes de biodistribuição apresentaram resultados encorajadores para a entrega localizada de fármacos de maneira mais homogênea, melhorando a biodisponibilidade e efeitos terapeuticos. Mais estudos relacionados ao aumento da eficiência de encapsulação e testes de efetividade in vivo no tratamento de doenças devem ser promovidos. Acreditarmos que combinação das vantagens relacionadas à estrutura vesicular dos polimerossomas, estabilidade, e muco penetração possibilitam o desenvolvimento de uma nova plataforma para a entrega controlada de medicamentos na mucosa. / Mucus protects the human body by trapping foreign particulates but also poses a barrier for drug delivery by slowing down the mobility of drug carriers. To design mucus penetrating carriers, solid particles are typically coated with inert polymers such as polyethylene glycol (PEG) to prevent mucoadhesion. However, the solid structure of these particles limits their loading capabilities and the process to coat them requires a complex synthesis. In this thesis we studied methods to fabricate nanocarriers with an exceptional combination of properties including a good mucus-penetration capability and loading capacity of hydrophilic and hydrophobic cargos. Unlike conventional coating methods, we use a diblock copolymer, consisting of both hydrophobic and hydrophilic blocks, which self-assembles into polymersomes under hydration. Because of the inertness of the hydrophilic block, these polymersomes should be mucus-penetrating by nature. Moreover, their hollow structure provides the polymersomes to be loaded with hydrophilic cargo, whereas hydrophobic cargo can be carried through the membrane. Importantly, by using a hydrolysable acid-catalyzed polymer (poly lactic acid, PLA) as the copolymer backbone, we demonstrate that these polymersomes can release contents upon application of external pH stimuli. Particle Tracking experiments demonstrated that polymersomes diffuse faster than uncoated particles in porcine intestine mucus, and biodistribution tests displayed encouraging results towards more homogeneous local drug-delivery, helping bioavailability as well as therapeutic efects. More studies related to the increase of encapsulation efficiency, and in vivo disease treatment tests should be promoted. Although we believe that combining the advantages of polymersome carrier, and tunning the membrane composition, this mucus-penetrating carrier we propose may provide as a new platform for mucosal drug delivery.

Magnetoelectricity (ME) is a physical property that results from an exchange between polar (electric dipole) and spin (magnetic dipole) subsystem: i.e., a change in polarization (P) with application of magnetic field (H), or a change in magnetization (M) with applied electric field (E). Magnetoelectricity can be found both in single phase and composite materials. Compared with single phase multiferroic materials, composite multiferroics have higher ME effects. Through a strictive interaction between the piezoelectricity of the ferroelectric phase and the magnetostriction of the ferromagnetic phase, said multiferroic composites are capable of producing relatively large ME coefficients. This Dissertation focused on the deposition and characterization of two-phase composite magnetoelectric thin films. First, single phase ferroelectric thin films were studied to improve the multiferroic properties of the composite thin films. Then structural, ferroelectric, ferromagnetic, and magnetoelectric properties of composite thin films were researched. Finally, regular nano-array composite films were deposited and characterized. First, for single phase ferroelectric thin films, the phase stability was controlled by epitaxial engineering. Because ferroelectric properties are strongly related to their crystal structure, it is necessary to study the crystal structures in single phase ferroelectric thin films. Through constraint of the substrates, the phase stability of the ferroelectric thin films were able to be altered. Epitaxial thin-layers of Pb(Fe1/2Nb1/2)O3 (or PFN) grown on (001), (110), and (111) SrTiO3 substrates are tetragonal, orthorhombic, and rhombohedral respectively. The larger constraint stress induces higher piezoelectric constants in tetragonal PFN thin film. Epitaxial thin-layers of Pb(Zr0.52Ti0.48)O3 (or PZT) grown on (001), (110), and (111) SrTiO3 substrates are tetragonal, monoclinic C, and rhombohedral respectively. Enhanced ferroelectric properties were found in the low symmetry monoclinic phase. A triclinic phase in BFO was observed when it was deposited on tilted (001) STO substrates by selecting low symmetry (or interim) orientations of single crystal substrates. Then, in two phase composite magnetoelectric thin films, the morphology stability was controlled by epitaxial engineering. Because multiferroic properties are strongly related to the nano-structures of the composite thin films, it is necessary to research the nano-structures in composite thin films. Nano-belt structures were observed in both BaTiO3-CoFe2O4 and BiFeO3-CoFe2O4 systems: by changing the orientation of substrates or annealing condition, the nano-pillar structure could be changed into nano-belts structure. By doing so, the anisotropy of ferromagnetic properties changes accordingly. The multi-ferroic properties and magnetoelectric properties or (001), (110) and (111) self-assembled BiFeO3-CoFe2O4 nano-composite thin film were also measured. Finally, the regular CoFe2O4-BiFeO3 nano-array composite was deposited by pulsed laser deposition patterned using a focused ion beam. Top and cross-section views of the composite thin film showed an ordered CoFe2O4 nano-array embedded in a BiFeO3 matrix. Multiferroic and magnetoelectric properties were measured by piezoresponse force microscopy and magnetic force microscopy. Results show (i) switching of the magnetization in ferromagnetic CoFe2O4 and of the polarization in ferroelectric BiFeO3 phases under external magnetic and electric field respectively, and (ii) changes of the magnetization of CoFe2O4 by applying an electric field to the BiFeO3 phase. / Ph. D.