Nano-crystalline porous anatase TiO2 for environmental applications: Synthesis process and transport characteristics study
The morphology of a phase separating and gelling biopolymer mixture (gelatin-maltodextrin) is strongly affected not only by thermodynamic conditions, but also by the presence of a restricted geometry. Phase separation within droplets is analysed using confocal laser scanning microscopy and image analysis by varying concentration (4% gelatin and 4%-7.3% maltodextrin), quench temperature (10 degrees C to 25 degrees C) and droplet diameters (10 mu m-120 mu m). The effects of confinement as well as quench temperature increase with increasing maltodextrin concentration in 120 mu m sized droplets. In small droplets below 20 mu m, the confinement and surface dominate the microstructure. The trends observed show good agreement with predictions of the elastic Lennard-Jones (ELJ) model, adapted to handle confinement, that is solved via conventional molecular dynamics. A one-dimensional spin-chain with variable bond length is furthermore introduced and shown to capture a number of qualitative behaviors. The findings reveal that the confined biopolymer mixture can be characterized by the very few parameters of the ELJ model, which incorporates the basic mechanism of short range attraction (collapse, crystallization) versus long range elastic repulsion (osmotic penalty). Accordingly, the study suggests that the model provides a handle towards the morphological design of binary polymer mixtures in microcapsules, droplets or other geometries of well defined size and shape. [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 ►26 April 2024 mk