Nano-crystalline porous anatase TiO2 for environmental applications: Synthesis process and transport characteristics study
Raman spectroscopy technique has been successfully used to study the microscopic nature of structural and/or morphological properties of investigated nanopowders. The phonon confinement model has been applied for the estimation of nanocrystals dimensions (TiO2 and CeO2), as well as the correlation length (ZnO), from the frequency shift and asymmetrical broadening of Raman optical phonon modes. The particle size distribution in nanopowders has been estimated from the low frequency Raman spectra, using the fact that the acoustic phonon modes in nanosized TiO2 and CeO2 can be well described by the elastic continuum model. In addition, the appearance of surface optical phonon modes has been predicted theoretically by the dielectric functions approach and detected experimentally in the Raman spectra of ZnO nanopowders, whereas the resonant behaviour of the first and second order ZnO Raman modes has been used for estimation of the electron-phonon interaction in this kind of nanomaterial. The optical properties of oxide nanopowders have been investigated by spectroscopic ellipsometry and photoluminescence spectroscopy. It has been shown that bandgap energy, as well as the energies of the other interband electronic transitions in investigated nanopowders can be determined by spectroscopic ellipsometry. On the other side, the existence of the broad bands in visible region of the photoluminescence spectra of TiO2 and ZnO nanopowders points out to the various electronic transitions mediated by defect levels within the bandgap. [hide]
Principal Investigators
Igor Stankovic (CoPI)
Scientific Computing Laboratory Belgrade, Serbia ►
Zorana Dohcevic-Mitrovic (CoPI)
Center for Solid State Physics & New Materials Belgrade, Serbia ►
Martin Kroger (PI)
Polymer Physics, ETH Zurich, Switzerland ►
Investigators
Zoran V. Popovic
Center for Solid State Physics & New Materials Belgrade, Serbia ►
Alexsandar Golubovic
Center for Solid State Physics & New Materials Belgrade, Serbia ►
Maja Scepanovic
Center for Solid State Physics & New Materials Belgrade, Serbia ►
Mirjana Grujic-Brojcin
Center for Solid State Physics & New Materials Belgrade, Serbia ►
Alexsandar Belic
Scientific Computing Laboratory Belgrade, Serbia ►
Slobodan Vrhovac
Scientific Computing Laboratory Belgrade, Serbia ►
Involved Students
Sonja Askrabic
Center for Solid State Physics & New Materials Belgrade, Serbia ►
Milan Zezelj
Scientific Computing Laboratory Belgrade, Serbia ►
Dusan Vudragovic
Scientific Computing Laboratory Belgrade, Serbia ►
Jelena Smiljanic
Scientific Computing Laboratory Belgrade, Serbia ►
Jaksa Vucicevic
Scientific Computing Laboratory Belgrade, Serbia ►
Milos Radonjic
Scientific Computing Laboratory Belgrade, Serbia ►
Marko Mladenovic
Scientific Computing Laboratory Belgrade, Serbia ►
Titanium dioxide (TiO2) is an important photo catalyst due to its strong oxidizing power, non-toxicity and long-term photo stability. The interest in nano-crystalline anatase TiO2 has been driven by its potential for a variety of technological applications including photo catalysis, electrochemical solar cells, optoelectronic devices, chemical sensors, and dielectric material of thin-film capacitors. Together with cerium dioxide (CeO2), porous TiO2 is seen as a material for the production of molecular hydrogen from water using sun energy in a photo catalytic reaction process. In addition, nanocrystalline anatase TiO2 is a weak magnetic semiconductor with proven room temperature ferromagnetism. This opens the possibility for the use of TiO2 in second-generation spintronic devices. Its ferromagnetic properties can be enhanced with the addition of transition metals such as iron, cobalt, or vanadium. Approximately 4 million tons of TiO2 are consumed annually worldwide. the principle use today being that of a bright white pigment.The enumerated properties of TiO2: catalytic, porous structure, and ferromagnetism, can be fully utilized only if they are combined: (i) Applications such as pollution monitoring or leak localization in chemical plants require high sensitivity and selectivity. By discriminating between different patterns of diffusion it is possible to enable this class of sensors to recognize different molecules (ii) The distribution of TiO2 pore diameters determines the collision frequency of molecules with the pore walls and thus also the frequency of catalytic reactions. Porous media can be specifically designed and engineered so as to balance between rates of reactant inflow, chemical reaction, and outflow. (iii) In photo-hydrolysis, hydrogen is produced from solar energy. In order to achieve this ambitious goal, it is necessary not only to understand the surface interaction between TiO2 and the molecules of water, hydrogen and oxygen, but also the transport of water into the nanopores as well as the transport of oxygen and hydrogen out of them. (iv) Finally, an external magnetic field could be applied as additional parameter during the technological process in which porous TiO2 media is synthesized. If brought to application, porous structures with anisotropic geometries could be created, i.e., elongated pores in magnetic field direction. In Gräel dye solar cells, such pore geometries would lead to shorter electron diffusion paths towards the metal electrode and improve the efficiency of the whole system.
The main objectives of this project are: (1) synthesis of porous TiO2 nanocrystals through the utilization of a novel and cost effective sol-gel method and the full characterization of the obtained structural and optical properties and (2) creation of multi-scale models and simulations specifically designed for the development of environmental TiO2 based technology.
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Selected conferences (co-)organized by project members
IWNET 2009
08 Sep - 10 Sep 2009, Eternal Spring City of Cuernavaca, Mexico ►20 April 2024 mk