Nano-crystalline porous anatase TiO2 for environmental applications: Synthesis process and transport characteristics study
Protein adsorption onto brush displaying surfaces is strongly affected by collapse, an effect utilized in protein chromatography and in harvesting cell sheets for tissue engineering applications. For relatively small particles, the free energy penalty incurred upon insertion into the brush F(ins) is related to the work expended against the osmotic pressure of the unperturbed brush. Within the self-consistent field (SCF) theory of brushes, the scale of F(ins) decreases with the brush thickness < z > because the value of the osmotic pressure at the grafting surface Pi(0) similar to < z > irrespective of the interaction free energy. Brush collapse thus favors adsorption because it reduces F(ins) via two effects: (i) lowering of the osmotic pressure and (ii) a possible decrease of the inserted volume of the particle. These general results are supplemented by numerical solutions of SCF equations for the collapse of thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) brushes as described by the empirical free energy of Afroze et al. (J. Mol. Struct. 2000, 554, 55). These yield the monomer concentration profiles c(z) and the corresponding osmotic pressure profiles Pi(z) as functions of the altitude z and the temperature T. c(z) and Pi(z) are then used to characterize F(ins) for collapsed and swollen brushes as well as the adsorption isotherms for three adsorption mechanisms of relevance to ex vivo biotechnology applications involving PNIPAM brushes: (a) primary adsorption at the wall, (b) adsorption onto a ligand embedded within the brush, and (c) ternary adsorption within the brush due to weak attraction between the polymer and the adsorbing particle. Our results rationalize existing experimental results concerning the interactions between proteins and PNIPAM brushes and predict the effects of tuning parameters such as grafting density, polymerization degree and protein dimensions. [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 ►28 March 2024 mk