Hybrid composites with elongated functional plasmonic or magnetic nanoparticles for environmental or biomedical applications

Resumo

This thesis is a multidisciplinary study focusing on the design, synthesis, characterization, and application of hybrid nanomaterials exhibiting plasmonic or magnetic properties. The main goal of the thesis is to use these nanomaterials effectively in environmental or biomedical fields, following the fabrication of hybrid nanostructures with improved performances. The thesis goal is divided into two main parts: (i) photocatalysis studies in which enhance the photoactivity of titanium dioxide nanoparticles (TiO2 NPs), a semiconductor, by plasmonic anisotropic nanostructures, and (ii) the design of anisotropic spiky structures by means of the incorporation of elongated magnetic nanostructures on a curved surface as potential remote control tools, and investigation of their interactions with living cells. The present thesis has been structured into five chapters. Chapter 1 includes a literature review covering the synthesis of nanomaterials and their applicability in photocatalysis and biomedical fields. Firstly, the advanced properties of nano-scale materials and the importance of these nanostructures in materials science are briefly summarized. Subsequently, the synthesis methods of nanomaterials including single-phase and anisotropic hybrid structures are explained based on the methods used in the thesis. Regarding to environmental applications, semiconductor photocatalysis and plasmon-induced photocatalysis principles, which are frequently preferred in this field, are presented in detail. There is also a short chapter on plasmonic materials and their optical properties, which are one of the main elements of the thesis. Finally, biomedical applications, which is another focused field in this thesis, are emphasized. The section includes the interaction of nanoparticles with living cells and the effect of the structural and morphological properties of the particles on these interactions are discussed. Here is a brief summary of the functionality of magnetic nanoparticles in this field, the basics of magnetism, and the major biomedical applications for which magnetic nanoparticles are often favoured are presented. The information enclosed in this chapter serve as a fundamental resource for understanding the theoretical and experimental inputs presented in the succeeding chapters. In Chapter 2, it is aimed to quantitatively determine the presence of TiO2 NPs in seawater through their photocatalysis capabilities, taking into account the potential risks that may arise as a result of their arising release into the aquatic environment. For this, elongated titanate nanowires decorated with plasmonic gold nanostars served as a filter system through which seawater containing TiO2 NPs was filtered. The presence of TiO2 NPs effectively accumulated on this filter were determined by their plasmon-induced photocatalytic activity associated with the concentrations of TiO2 NPs. Chapter 3 is a continuation of the system developed in the previous chapter and focuses on improving the efficiency of plasmonic gold nanostars for semiconductor photocatalysis. Differently, polydopamine coated gold-silver alloy nanostructures were developed with the green synthesis method, which includes a wide optimization section in which different seeds are used as nucleation centers. The effects of these anisotropic nanostructures on the photoactivity of TiO2 NPs were investigated considering their enhanced properties. Chapter 4 covers the design, synthesis, and optimization of magnetic particles characterized by spiky surface topography for use in biomedical applications. The chapter describes the production of spiky magnetic materials by growing elongated iron oxide particles on a polystyrene sphere. The synthesis of elongated nanostructures on a spherical PS template, their growth profile, and conversion to iron oxide phase have been extensively studied with the assistance of detailed characterizations. Evaluation of the directed propulsions of the resulting structures with different surface topography and magnetic properties under the influence of magnetic field gradient demonstrated that materials are suitable for use as effective systems in many applications. Chapter 5 reports the detailed investigation the role of surface topography of nanoparticles on their interactions with living cells. Magnetic spiky particles synthesized in the previous chapter were used for this aim. To examine the effect of surface topography during the cellular internalization processes of particles, polystyrene beads decorated with spherical iron oxide nanoparticles were synthesized as control of spiky iron oxide particles. Thus, it is aimed to compare the interactions of two different magnetic materials with smooth and rough surfaces with the cell. Furthermore, the uptake and intracellular fates of magnetically oriented particles to subcellular levels were compared with particles internalized by endocytosis, confirming that magnetically oriented particles are effective tools for biomedical applications. Finally, magnetic manipulation studies were performed with cells containing magnetic particles under an external magnetic field gradient which is an effective method for cell sorting/separation. Altogether, this thesis aims to contribute to the progress in the design and application of plasmonic or magnetic hybrid nanostructures for different implementations in the field of nanotechnology.