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Les bactéries sont les organismes les plus abondants dans le monde. Des études sur les bactéries peuvent être bénéfiques pour la recherche médicale, la qualité des ressources en eau et l'industrie alimentaire. La détection et le marquage fluorescent est une des méthodes les plus utilisées pour des objectifs bioanalytiques. Dans la recherche de marqueurs luminescents et stables, des nouvelles nanoparticules fluorescentes et auto-stabilisées à base de polymères (FNPs, 60 nm) et des chaînes de polymères fluorescents (FPCs, 5nm) ont été développées. Dans un premier chapitre, une méthodologie pour insérer ces FNPs dans la bactérie E.coli a été développée. Pour contrôler si les FNPs sont en effet internalisé, nous avons développé un protocole basé sur l'extinction de luminescence des FNPs par le bleu de méthylène. Dans un second chapitre, les biotines conjuguées de FNPs peuvent être utilisées pour étudier les protéines membranaires spécifiques. En utilisant un lien streptavidine-biotine, un "sandwich" est formé pour construire un pont entre des particules, des anticorps spécifiques et des bactéries. Les images de fluorescence SPR et les images SEM ont démontré l'interaction de la biotine conjuguée de FNPs avec la bactérie E.coli. Dans un troisième chapitre, les chaînes de polymères fluorescents de couleur verte (GFPCs) peuvent facilement entrer dans des bactéries E.coli. Les GFPCs peuvent marquer le cyctoplasme mais pas l'ADN. Les chaînes de polymères fluorescents de couleur rouge (RFPCs) peuvent marquer facilement et efficacement la membrane de bactérie E.coli. Les deux FPCs sont extrêmement brillantes et non toxiques, les chaînes sont solubles dans l'eau. Ce sont de nouveaux matériaux fluorescents pour le marquage interne et externe des bactéries. Dans le dernier chapitre, il est démontré que les FANPs sont sensibles au pH et peuvent être utilisées pour mesurer la croissance de la bactérie E.coli. Les nano-objets détectent rapidement et précisément la croissance des cellules. En effet, leur fluorescence est sensible au changement de pH résultant du métabolisme cellulaire. De plus, ces particules permettent une surveillance en continu d'un grand nombre d'échantillons pour des applications de criblage à haut débit. Les nanomatériaux présentés dans ce manuscrit sont des outils prometteurs pour les applications en biocapteurs et bioimagerie en raison de leur luminosité/brillance et photostabilité élevées ainsi que les possibilités de post-fonctionnalisation. / Bacteria are the most abundant organisms in the world. Investigations and studies on bacteria can be beneficial to medical research, water resources research and food industry. Fluorescent sensing and labeling are commonly used for bioanalytical purposes. In the quest for very bright and stable labels, novel polymer-based, self-stabilized, fluorescent nanoparticles (FNPs, 60 nm) and fluorescent polymer chains (FPCs, 5 nm) have been developed. In the first part, a methodology to insert these FNPs into E.coli bacteria was developed. To control if the FNPs are indeed internalized, we developed a protocol based upon FNPs luminescence quenching by methylene blue. In the second part, a "sandwich" system is built. By using a streptavidin-biotin link, a bridge between particles (FNP), specific antibodies and bacteria is built. SPR, fluorescent images and SEM images demonstrated the interaction of biotin conjugated FNPs with E.coli bacteria. In the third part, interactions of fluorescent polymer chains with bacteria are investigated. Green fluorescent polymer chains (GFPCs) can easily enter into E.coli bacteria. GFPCs can label the cytoplasm but not the DNA. Red fluorescent polymer chains (RFPCs) can label the membrane of E.coli bacteria easily and efficiently. Both FPCs are highly water-soluble, bright and non-toxic, they are novel fluorescent labels for internal and external biological labeling of bacteria. In the last part, it is demonstrated that pH sensitive FANPs can be used to measure the growth of E.coli. They detect rapidly and accurately bacterial growth by signaling the change of pH resulting from cellular metabolism. Moreover, these particles allow for continuous monitoring a large number of samples for high-throughput screening applications. The studied fluorescent nanomaterials are promising tools for biosensing and bioimaging applications due to their brightness, high photostability and rich functionalisation ability.

The clinical management of cancer has principally relied upon surgery, radiation therapy, and chemotherapy for many decades. Despite recent advances in molecularly-targeted diagnostic and therapeutic agents, the long-term survival rates in patients with solid malignancies including ovarian cancer have improved only incrementally. Nanotechnologies designed to locally interrogate and modulate the tumor microenvironment offer a promising opportunity to enhance existing treatment modalities and establish new therapeutic paradigms. By virtue of their elemental composition, geometry, and surface chemistry, nanomaterials can be engineered with optical and pharmacokinetic properties which permit these agents to localize, fluoresce, and deposit energy within tumors. Nanomaterials therefore provide a clear route towards future approaches for sensitive diagnosis and imaging of tumors and targeted therapeutic delivery.

Philosophiae Doctor - PhD / There has been extensive growth in nanoscale technology in the last few decades to such a degree that nanomaterials (NMs) have become a constituent in a wide range of manufactured commercial and domestic products. This surge has resulted in uncertainties regarding their environmental impact, due to the significant increases in the amount of NMs released into the environment (Dowling et al., 2004) through intentional and unintentional releases. Like many other toxins, the aquatic environment is particularly vulnerable as it acts as a sink for nanoparticles (NPs) (Scown et al., 2010). The escalating growth of NMs has not advanced without efforts to understand its properties. Despite the dramatic advances in both the production and application of NMs, very little is known regarding their interaction with and effects on environmental and human health. Given the lack in scientific knowledge, particularly under various environmental conditions, it is often difficult to accurately assess the potential exposure pathways to ecological receptors of all NMs, silver nanoparticles (AgNPs) are the most widely used NPs, present in several consumer products mainly because of their anti-bacterial properties. It is estimated that the annual production exceeds 1000 tons/year (Piccinno et al., 2012). The increase uses of AgNPs in consumer products (e.g. textiles, cosmetics and personal hygiene), household appliances (e.g. washing machines and vacuum cleaners) and medical equipment have led to their increase release into the environment, thereby posing an environmental risk and human health concern. Silver NPs are known to induce the production of Reactive Oxygen Species (ROS) (Ahamed et al., 2010; Levard et al., 2012; Piao et al., 2011). Also since AgNPs are oxidized to ionic Ag (Ag+), it is still unclear whether the effects of ROS can be attributed to Ag+ release or to the AgNP itself (Fabrega et al., 2009; Miao et al., 2009). The behaviour of AgNPs is collectively influenced by inherent (nanoparticle size, shape, surface area, surface charge, crystal structure, coating, solubility/dissolution) and environmental factors (temperature, pH, ionic strength, salinity, organic matter). Climate change predictions indicate that the frequency, intensity and duration of extreme natural events (such as temperature elevations) will increase in the future (IPCC, 2001; IPCC, 2007). Global warming and climate change could increase atmospheric temperatures by 2.4 – 6.4 °C (IPCC, 2001; IPCC, 2007). The main feature associated with global climate change is the anticipation of wetter winters (i.e. increased flood events) and drier, warmer summers (i.e.extreme temperatures). These changes are likely to affect the inputs of contaminants into the environment as well as affect their behaviour, fate and transport, and toxicity in aquatic environments. It is known that the current temperature predictions in climate change scenarios could directly affect aquatic ecosystem communities (Carpenter et al., 1992), since temperature is also regarded as an important abiotic factor influencing growth and production of primary producers (i.e. algae, macrophytes etc.), and may also affect species distribution. For example, Liu et al. (2010) reported higher dissolution rates of AgNPs with increased temperature. Similarly, sudden hydrographic activity like high flood conditions may cause resuspension and redistribution of sediments. Few studies have linked the foreseeable climate change with contaminant release and ecosystem impacts. Similarly, few studies have analyzed the behaviour of NMs in the environment considering these predicted changes in mean temperatures. This thesis focuses on the effects of AgNPs on oxidative stress responses in the Cape River crab Potamonautes perlatus. The present work was undertaken to interpret the biological effects of AgNPs (< 100 nm) on P. perlatus, as well as to assess its effects under different environmental conditions. To understand the uptake, accumulation and biological effects of AgNPs, freshwater microcosms were produced to mimic a typical aquatic environment and temperature manipulated microcosms to which a commercially-available AgNP powder was added. Nanoparticles were characterized in the dry state and in suspension under different environmental conditions. Dissolution of total Ag was measured by inductively coupled plasma mass spectrometry (ICP-OES). Nanoparticle toxicity was assessed by measuring mortality and biomarkers of oxidative stress (CYP450, SOD, CAT, GST) evaluated in crab tissues. The overall results demonstrated that: (1) AgNPs may be transformed in both size and state under variable environmental conditions. The formation of smaller aggregates at higher temperatures suggests higher toxicity, (2) the release of free metal ions from NPs and NPs aggregates contribute to a higher toxicity towards aquatic organisms, (3) oxidative stress is a significant mechanism of AgNP toxicity and consequently enzymatic activation/inhibition with increasing AgNP concentration and temperatures, (4) oxidative stress responses to AgNPs particles were significantly modulated by temperature stress in P. perlatus, (5) mortality was observed from day 2 with maximum mortality achieved at day 7, (6) enzymes involved in detoxification, i.e. CYP450, has functional significance in the haemocytes, (7) P. perlatus has proved to be a significant target for AgNP exposure and, furthermore, has proved to be a suitable species to assess the ecotoxicity of AgNP in the aquatic environment, (8) antioxidant enzymes activities (are valuable tools to assess the oxidative status of crab tissues co-exposed to AgNPs and temperature. Furthermore, the results obtained in this study contributed to the understanding of the behaviour, bioavailability, uptake and toxicity of AgNPs under variable temperatures. / National Research Foundation (NRF) Thuthuka Fund and CSIR

Nanoscience and nanotechnology offer potential routes towards addressing critical issues such as clean and sustainable energy, environmental protection and human health. Specifically, metal and metal oxide nanomaterials are found in a wide range of applications and therefore hold a greater potential of possible release into the environment or for the human to be exposed. Understanding the aqueous phase behavior of metal and metal oxide nanomaterials is a key factor in the safe design of these materials because their interactions with living systems are always mediated through the aqueous phase. Broadly the transformations in the aqueous phase can be classified as dissolution, aggregation and adsorption which are dependent and linked processes to one another. The complexity of these processes at the liquid-solid interface has therefore been one of the grand challenges that has persisted since the beginning of nanotechnology. Although classical models provide guidance for understanding dissolution and aggregation of nanoparticles in water, there are many uncertainties associated with the recent findings. This is often due to a lack of fundamental knowledge of the surface structure and surface energetics for very small particles. Therefore currently the environmental health and safety studies related to nanomaterials are more focused on understanding the surface chemistry that governs the overall processes in the liquid-solid interfacial region at the molecular level. The metal based nanomaterials focused on in this dissertation include TiO2, ZnO, Cu and CuO. These are among the most heavily used in a number of applications ranging from uses in the construction industry to cosmetic formulation. Therefore they are produced in large scale and have been detected in the environment. There is debate within the scientific community related to their safety as a result of the lack of understanding on the surface interactions that arise from the detailed nature of the surfaces. Specifically, the interactions of these metal and metal oxide nanoparticles with environmental and biological ligands in the solutions have demonstrated dramatic alterations in their aqueous phase behavior in terms of dissolution and aggregation. Dissolution and aggregation are among the determining factors of nanoparticle uptake and toxicity. Furthermore, solution conditions such as ionic strength and pH can act as controlling parameters for surface ligand adsorption while adsorbed ligands themselves undergo surface induced structural and conformational changes. Because, nanomaterials in both the environment and in biological systems are subjected to a wide range of matrix conditions they are in fact dynamic and not static entities. Thus monitoring and tracking these nanomaterials in real systems can be extremely challenging which requires a thorough understanding of the surface chemistry governing their transformations. The work presented in this dissertation attempts to bridge the gap between the dynamic processing of these nanomaterials, the details of the molecular level processes that occur at the liquid-solid interfacial region and potential environmental and biological interactions. Extensive nanomaterial characterization is an integral part of these investigations and all the materials presented here are thoroughly analyzed for particle size, shape, surface area, bulk and surface compositions. Detailed spectroscopic analysis was used to acquire molecular information of the processes in the liquid-solid interfacial region and the outcomes are linked with the macroscopic analysis with the aid of dynamic and static light scattering techniques. Furthermore, emphasis is given to the size dependent behavior and theoretical modeling is adapted giving careful consideration to the details of the physicochemical characterization and molecular information unique to the nanomaterials.

Packaging plays an important role in ensuring food safety and quality. The development antimicrobial packaging enables actively inhibiting/killing the spoilage microorganisms, and thus extending food product's shelf life. Generally, 50% shelf life extension is possible. The interest for using metallic nanoparticles in active packaging derives from its superior antimicrobial efficacy and no negative impact on the food sensory properties. In this thesis, the packaging material of concern is a PLA (Polylactic Acid) coated paper incorporating zinc oxide nanoparticles (ZnO NPs) in the coating layer. The material was characterized and its antimicrobial activity was evaluated. The SEM images show that the nanoparticles were homogenously distributed across the surface thanks to its surface modification. Antimicrobial assay indicates that the active material was effective in inactivating E. coli and S. aureus. Furthermore, E. coli was found to be more susceptible to this type of agent, showing 3.14 log reduction for 0.5 wt% agent loading in the PLA coating layer. This result was compared across the publications using the same agent for treating both Gram-positive and Gram-negative microorganisms. The discrepancy between the results can be explained by the fact that ZnO nanoparticles have multiple action mechanisms, and different antimicrobial testing methods may activate part of the action mechanisms. On the other hand, recyclability is regarded as an important attribute for paper-based packaging material, as it enables to conserve the resources and reduce the environmental impacts. Accordingly, when it comes to the nano-enabled paper packaging material, recyclability should be maintained. In this case, a recyclability test was carried out in a lab-scale paper recycling line. The protocol was based on a method adapted from the ATICELCA MC501-13, which enabled to recover over 99% of the solids material. The mass balance result indicates that 86%-91% zinc oxide nanoparticles ended up in the rejected material stream, mostly embedded within the polymer coating; whereas 7%-16% nanoparticles ended up in the accepted material stream. Besides, the tensile strength of the recycled handsheets suggests that the nano-enabled coating had no negative impacts on the recovered fibre quality. Active packaging plays a positive role in reducing food losses. If food and packaging are considered as a whole system, its overall environmental impact can be justified by incorporating the food loss reduction due to the application of active packaging. The LCA calculation shows that a breakeven point can be easily achieved for the case of red meat products of high environmental impact. / El envase juega un papel importante asegurando la seguridad y calidad de los alimentos. El desarrollo de envases activos, especialmente envase antimicrobiano, permite inhibir o matar los microorganismos causantes del deterioro de los alimentos, alargando por tanto su vida útil. De forma general es posible extender la vida útil de los alimentos en un 50%. El interés por el uso de nanopartículas metálicas en el envasado activo se deriva de su gran efectividad antimicrobiana sin causar un efecto negativo en sus propiedades sensoriales. En la presente tesis, se ha desarrollado un papel recubierto de PLA (ácido poliláctico) con nanopartículas de óxido de zinc (ZnO NPs) incorporadas en la capa de recubrimiento. Se ha caracterizado el material y se ha evaluado su capacidad antimicrobiana. Las imágenes obtenidas mediante SEM muestran que las nanopartículas fueron distribuidas a lo largo de la superficie gracias a su modificación. Los ensayos de efectividad antimicrobiana indicaron una actividad del material frente a E. coli y a S. aureus. Además, E. coli resultó ser más susceptible a este agente activo incorporado al 0.5 % en peso en el recubrimiento de PLA, mostrando una reducción de 3.14 log. Este resultado fue comparado con publicaciones donde se emplearon los mismos agentes activos para frente a microorganismos Gram-positivos y Gram-negativos. Las discrepancias encontradas entre los resultados pueden deberse a que las nanopartículas de ZnO tienen múltiples mecanismos de acción, y los diferentes métodos de ensayo poder estimular parte de estos mecanismos. Por otra parte, el reciclado juega un importante papel en la conservación de los recursos y en la reducción de los impactos medioambientales. Por tanto, cuando se trata de un material de envase de papel con sustancias de tamaño nano, el reciclado debe tratarse adecuadamente. El ensayo de reciclabilidad fue llevado a cabo a escala laboratorio en una línea de reciclado de papel. El protocolo de ensayo se basó en el método adaptado de ATICELCA MC501-13, permitiendo una recuperación del 99% de material sólidos. Los resultados del balance de materia indicaron que el 86%-91% de las nanopartículas de óxido de zinc llegaron al flujo de material de rechazo, principalmente mezclado en el recubrimiento polimérico. Además, los resultados de tracción de las láminas recicladas sugieren que el recubrimiento con partículas nano no tiene un efecto negativo sobre la calidad de la fibra recuperada. El envase activo juega un papel positivo en la reducción de los residuos alimentarios. Como resultado del uso del envase activo, considerando el envase y el alimento como un todo, el impacto ambiental sobre este sistema completo puede ser compensado por la reducción de pérdidas de alimentos. El cálculo LCA muestra que el punto de equilibrio se puede conseguir fácilmente en el caso de productos de carne roja de elevado impacto ambiental. / L'envàs té un paper prou important en la seguretat i la qualitat del aliments. El desenvolupament dels envasos actius, especialment l'envàs antimicrobià, el qual permeteix l'inhibició o mort dels microorganismes que produeixen el deteriorament dels aliments i, per tant, allargant la seua vida útil. De manera general, es possible l'allargament de la vida útil dels aliments en un 50%. L'interès per la utilització de nanopartícules metàl·liques en l'envasat actiu es deriva de la seua gran efectivitat antimicrobiana sense produir un efecte negatiu en les seus propietats sensorials. En aquesta present tesis, s'ha desenvolupat un paper recobert de PLA (àcid polilàctic) amb nanopartícules d'òxid de zinc (ZnO NPs) incorporades a la capa de recobriment. S'ha caracteritzat el material i s'ha avaluat la seua capacitat antimicrobiana. Les imatges obtingudes per mitjà del SEM mostren que les nanopartícules foren distribuïdes en tota la superfície gràcies a la seua modificació. Els assajos d'efectivitat antimicrobiana varen indicar una activitat del material front a E.coli i a S. aureus. A més, E. coli va resultar ser més susceptible a aquest agent actiu incorporat al 0.5 % en pes en el recobriment de PLA, mostrant una reducció de 3.14 log. Aquest resultat va ser comparat amb publicacions on es van emprar els mateixos agents actius front a microorganismes Gram-positiu i Gram-negatiu. Les discrepàncies trobades entre els resultats poden deure's a que les nanopartícules de ZnO tenen diversos mecanismes d'acció, i els diferents mètodes d'assaig poder estimular part d'aquestes mecanismes. Per altra banda, el reciclatge també té un paper important en la conservació dels recursos i en la reducció dels impactes mediambientals. Per tant, quan es tracta d'un material d'envàs de paper amb substàncies de la grandària 'nano', el reciclatge ha de tractar-se adequadament. El assaig de reciclabilitat va ser dut a terme a escala de laboratori en una línia de reciclatge de paper. El protocol de l'assaig es va basar en el mètode adaptat d'ATICELCA MC501-13, permetent una recuperació del 99% del material sòlid. Els resultats del balanç de matèria van indicar que el 86-91% de les nanopartícules d'òxid de zinc varen arribar al fluix material de rebuig, principalment mesclat en el recobriment polimèric. A més, els resultats de tracció de les làmines reciclades suggereixen que el recobriment amb nanopartícules nano no tenen un efecte negatiu sobre la qualitat de la fibra recuperada. L'envàs actiu juga un paper positiu en la reducció dels residus alimentaris. Com a resultat de l'ús de l'envàs actiu, considerant l'envàs i l'aliment com un tot conjunt, l'impacte ambiental sobre aquest sistema complet pot ser compensat per la reducció de pèrdues d'aliments. El càlcul LCA mostra que el punt d'equilibri es pot aconseguir fàcilment en el cas de productes de carn roja d'elevat impacte ambiental. / Zhang, H. (2016). Sustainability assessment of active packaging incorporating nanomaterials [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/75348 / TESIS

Interacting cellular systems with nano-interfaces has shown great promise in promoting differentiation, regeneration, and stimulation. Functionalized nanostructures can serve as topological cues to mimic the extracellular matrix network to support cellular growth. Nanostructures can also generate signals, such as thermal, electrical, and mechanical stimulus, to trigger cellular stimulation. At this stage, the main challenges of applying nanostructures with biological systems are: (1) how to mimic the hierarchical structure of the ECM network in a 3D format and (2) how to improve the efficiency of the nanostructures while decreasing its invasiveness. To enable functional neuron regeneration after injuries, we have developed a 2D nanoladder scaffold, composed of micron size fibers and nanoscale protrusions, to mimic the ECM in the spinal cord. We have demonstrated that directional guidance during neuronal regeneration is critical for functional reconnection. We further transferred the nanoladder pattern onto biocompatible silk films. We established a self-folding strategy to fabricate 3D silk rolls, which is an even closer system to mimic the ECM of the spinal cord. As demonstrated by in vitro and in vivo experiments, such a scaffold can serve as a grafting bridge to guide axonal regeneration to desired targets for functional reconnection after spinal cord injuries. Benefited from the robust self-folding techniques, silk rolls can also be used for heterogeneous cell culture, providing a potential therapeutic approach for multiple tissue regeneration directions, such as bones, muscles, and tendons. For achieving neurostimulation, we have developed photoacoustic nanotransducers (PANs), which generate ultrasound upon excitation of NIR II nanosecond laser light. By surface functionalize PAN to bind to neurons, we have achieved an optoacoustic neuron stimulation process with a high spatial and temporal resolution, proved by in-vitro and in-vivo experiments. Such an application can enable non-invasive, optogenetics free and MRI compatible neurostimulation, which provides a new direction of gene-transfection free neuromodulation. Collectively, in this thesis, we have developed two systems to promote functional regeneration after injuries and stimulate neurons in a minimally invasive manner. By integrating those two functions, a potential new generation of the bioengineered scaffold can be investigated to enable functional and programmable control during the regeneration process.

Transition metals complexes have been involved in various catalytic, biomedical and industrial applications, but only lately they have been associated with nanomaterials to produce innovative and well-defined new hybrid systems. The introduction of transition metals into nanomaterials is important to bear the advantages of metals to nanoscale and also to raise the stability of nanomaterials. In this dissertation, we study two approaches of associating transition metals into nanomaterials. The first approach is via spontaneous self-organization based assembly of small molecule amphiphiles and bulky hydrophilic polymers to produce organic-inorganic hybrid materials that have nanoscale features and can be precisely controlled depending on the experimental conditions used. These hybrid materials can successfully act as templates to design new porous material with interesting architecture. The second approach studied is via electroless reduction of transition metals on the surface of nanocarbons (nanotubes and nanodiamonds) without using any reducing agents or catalysts. The synthesis of these systems is highly efficient and facile resulting in stable and mechanically robust new materials with promising applications in catalysis.

<div>Multifunctional characteristics of Bismuth-based oxides offer great opportunities to design a variety of devices exploiting either a single functionality or the synergistic multifunctionalities. In the past decades, strain engineering of thin films arose as a solution for fabrication of novel structures with highly desired properties. In this thesis, strain engineering has been applied to Bismuth-based oxides to explore the strain effect on thin film structures and functionalities.</div><div>BiFeO₃ (BFO) servers as the first study platform, because of its strain-induced phase transition and the corresponding diverse polarization properties. The strain effect of SrRuO₃ (SRO)-buffered substrates on ferroelectric and optical properties of BFO thin films has been investigated. A wide range of strain states have been achieved in BFO films. The ferroelectricity and bandgap have been effectively tuned even with partial strain relaxation. However, pure BFO suffers from high leakage current and large coercive field. To overcome these limitations, Sm-doped BFO (BSFO) systems emerged and has been used in controlling the microstructure and properties of BFO. Our detailed structure analysis proves the Sm doping amount in BSFO thin films can be tuned effectively via deposition temperature. Consequently, the Sm dopant influences phase formation of BSFO and the macroscopic ferroelectric properties. </div><div>Another member in Bismuth-based oxide family, Bi₂WO₆ (BWO), has been selected as the base material for the design of the two-phase nanocomposites, because of its unique layered structure and ferroelectric property. To introduce ferromagnetic component into BWO, two methods have been explored. The first method incorporates Mn cations into the BWO matrix (BWMO), and the second method couples CoFe2O4 (CFO) as secondary phase with BWO to form a vertically aligned nanocomposite (VAN) system. Both systems exhibit robust ferromagnetic and ferroelectric response at room temperature and demonstrate their promise as room temperature multiferroics for future spintronics and memory applications. </div><div>The studies in this dissertation demonstrate the great structure flexibility and tunable functionalities of BFO and BWO systems. It shows the potential structure modification and property control of other Bi-based oxides. In the last chapter, new experimental plans and directions are proposed. The connections between the strain engineering and the tunable material properties are being built for various applications. </div><div><br></div>

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