Synthesis and characterization of boron based nano-sized materials for different application areas

Nowadays, demand of energy sources is increasing rapidly day after day. In particular studies on alternative and renewable energy sources which may take place attracts attention both in scientific and technological way. Looking at the alternative energy sources which can be replaced with fossil fuels, the sun comes into the picture. The sun is limitless and low-cost energy source that everybody can utilize. The reactions that take place on the surface of the sun create tremendous amount of energy. As a result, it can be said that solar energy is one of the best renewable energy source with highest potential among the others. Due to its geographical location, our country is more fortune in comparison with other countries in the name of solar energy potential. When it comes to being able to utilize this potential efficiently, the solar cells come into the picture. In order to use solar energy, there are photovoltaic cells (solar cells) that convert the solar energy directly into electricity. Nowadays the most preferred type of solar cell is single crystal and/or polycrystal silicon based solar cells. The main reason of that is silicon can be found in nature too much. However, due to the high cost single crystal and/or polycrystal silicon based solar cells leave their place to organic solar cells. Especially in dye-sensitized solar cells (DSSC), which has been preferred to use in recent years, the usage of pure and/or dopped TiO2 semiconductor attracts more attention. One of the areas of greatest interest in the usage of dopped TiO2 nano structures is antimicrobial applications. In particular, bacteria and viruses threaten human health and strengthen their resistance and cause new species day after day. TiO2 nano structures have antimicrobial effect on different kinds of bacteria, viruses and so on, however its wide band gap limits its usage. Because of it TiO2 only activates under UV light irradiation. In order to overcome that limitation TiO2 was dopped with other materials and narrow its band gap down. For both application areas, dopping TiO2 with non-metals instead of metals has begun to became a hot topic for today. Especially boron is coming up forward as a dopant in order to have some extraordinary properties. Boron is a very strategically important element all around the world. Our country has almost 70% of boron reserves in comparison with the other countries. Strategic areas like defense, aviation and space industry, the usage of boron is increasing day by day. In this PhD thesis, boron doped TiO2 nano structures were synthesized. As a precursor boron oxide, which is widely used in the literature, was selected. At the same time, the amorphous elemental boron, which had not been studied previously, was also used as a precursor for the first time. The choice of the usage of elemental boron which is produced forum our country sources as a starting material; it is very important to ensure that the usage of boron widespread as an advanced technological material. Our country ranks second in the world order in terms of boron sources. Within this PhD research it is very important to develop and spread the usage area of boron by using it as precursor. Amorphous boron is also a product of another project that supported by national resources. Precursor material was provided from Pavezyum Kimya San. Dış. Ticaret Ltd. Şti. which is the first company in turkey and second in the world that produce nano-sized elemental boron. With the production of boron based nano-structures, boron resources will contribute to the national economy as advanced technological products. The properties obtained from synthesized boron containing nano-structures were discussed comparatively. All nano-structures have been synthesized using different starting materials. Boron dopped TiO2 (B-TiO2) nanoparticles and nanotubes were synthesized. As a synthesize methods, in order to have nanoparticles sol-gel method was used whereas hydrothermal method was preferred to obtain nanotubes. In order to discuss the effect of boron inside the structure, pure TiO2 nanoparticles and nanotubes were also synthesized. All the nano-structures were characterized using number of different characterization methods. Morphology and dimensional properties were discussed with the help of SEM and TEM analyses. XRD analyses were helpful in order to determine phases. Photovoltaic measurements were also performed. As a next step stable colloidal suspension were prepared using B-TiO2 nanoparticles and nanotubes. They were coated onto ITO (indium-din-oxide) glasses using electrophoretic deposition (EPD) method. Those coatings were investigated using SEM. As a last step, antimicrobial efficiency of synthesized nano-structures was investigated using antimicrobial tests.