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|Autori: ||Greco, Enrico|
|Titolo: ||Development of new Lithium-Transition Metals co-doped Nanotitania. A perspective for sustainable photocatalytic materials and a comparative study between benefits and health risks.|
|Abstract: ||During this century, rapid population growth has led to an increased exploitation of oil and nuclear power to satisfy energy demands. This situation has created a growing tension between the deteriorating condition of the natural environment and the needs of society. Several research projects have sought to improve the situation through the development of innovative products and eco-friendly technologies: for example, the purification of the gaseous emissions emitted by industrial sources, or the manufacture of vehicles using sunlight as a renewable and clean energy. In addition, newly created materials are able to reduce air pollutants (organic and inorganic) through the process of photocatalysis, which consists of using solid semiconductors able to oxidize harmful substances until complete mineralization. In this context, the production of photocatalytic building materials could constitute a very interesting solution, and become an integral part of the strategy to reduce environmental pollution. Titanium dioxide (TiO2) is one of the most common photocatalytic materials. It can be used in many fields of application, including the building industry. The combination of titanium dioxide with cement makes it possible to obtain a binder that has both traditional properties, such as mechanical strength and durability, and new properties allowing the preservation of the environment and the conservation of the aesthetic value of the buildings. For instance, researchers have managed to create a material capable of accelerating the oxidation of the organic pollutants that are deposited on the external walls of the buildings.
This dissertation focused on the design, synthesis and characterization of a new family of titanium dioxide 1D, 2D and 3D nano-systems, doped with lithium and some transition metals in order to decrease the band gap and to enable visible light photoactivation even in indoor conditions.
The NPs samples showed an increment of the relative surface areas that was better than the increments observed in all the nanosheet samples (446 m2/g-1). The use of lithium, cobalt, cerium, and tungsten ions as dopants was evaluated through the UV-Vis absorption technique. The results showed both an increased absorption in the visible range and a decrease of band gap for the doped samples in comparison to the sample of pure TiO2.
We used several methods to evaluate the photocatalytic efficiency of all the nanoparticles and nanosheets we produced. The Li-Co and Li-Ce doped nanoparticles showed very good results both in water solution and in gas phase. The photocatalytic activity of our nanosystems was comparable with the standard samples under UVb light, but the doped NPs, in particular those doped with Au@TiLi(5) and TiLi(5)Co(5), showed better results under visible light than the control samples.
Our new synthesis method achieved very interesting results. It allowed us to obtain nanoparticles, nanosheets, xerogels, and aerogels covered with Li+ ions in place of the H+ ion at the surface in order to maintain them in a good dispersion in solution.
In order to evaluate the toxicity of the NPs, a comparative study on human lung cells and E. coli cells was carried out in vitro. All the analyzed nanoparticles exhibited different photocatalytic activities for human cells and bacteria, in particular under irradiation. Some transition metal ions doped nanoparticles exhibited cytotoxicity even in absence of illumination, a phenomenon that was probably caused by their dopant content. The use of such systems could constitute a risk for human health; however, once inhaled, the lack of illumination within the human body could reduce such a risk, and for TiLi and Au@TiLi(5) groups the danger is virtually absent. The toxicity on E. coli cells is significantly higher in almost all cases. In the case of the TiLiCo group, in particular, there is a high contrast between the low toxicity for human cells and the high toxicity for E. coli.|
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|GRCNRC89B06B202K-EGreco_PhDdissertation.pdf||EGreco_PhDdissertation||12,87 MB||Adobe PDF||Visualizza/apri
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