Theoretical Study of the Flame Synthesis of Titanium Dioxide Nanoparticles Kui Ting Lam, Doug DePrekel, Kevin Ngo, Phu Vo, and Yingbin Ge Department of Chemistry, Central Washington University, Ellensburg, WA Introduction Titanium dioxide (TiO 2 ) nanoparticles are widely used in our daily lives. For example, TiO 2 nanoparticles are used as whitening agent, coating for polymers, surface support for photocatalysis and for solar energy conversion. Compared to the sol-gel synthesis of the TiO 2 nanoparticles, the flame synthesis is a cheaper and faster alternative. The mechanism of the flame synthesis of the TiO 2 nanoparticles, however, is not well understood. In this research, we will study theoretically the chemical mechanism of the flame synthesis of the TiO 2 nanoparticles, which involves both gas-phase and surface reactions. Density functional theory methods will be used to model these gas-phase and surface reactions. We aim to propose the mechanism of the flame synthesis of the TiO 2 nanoparticles through the density functional theory study. The ultimate goal is to provide theoretical guidance on the size and surface control of the flame-synthesized TiO 2 nanoparticles. References 1.Sung, Y.; Raman, V.; Fox, R. O.; Chem. Eng. Sci., 2011, 66, Wang, T.; Dixon, D. A.; Navarrete-lo, A. M.; Li, S.; Gole, J. L., J. Phys. Chem. A, 2010, 114, Zhao, W-N; Liu Z-P, Chem. Sci., 2014, 5, Production of TiO 2 nanoparticles Computational methods The coupled-cluster and density function theory (DFT) methods were used to study small Ti x O y Cl z species theoretically. The coupled-cluster method is highly accurate but extremely slow. DFT methods are in general less accurate but much faster than the coupled-cluster method. We need to first assess the accuracy of the DFT methods for the Ti-O-Cl species before studying the mechanism of the flame synthesis of TiO 2. Future Studies Kinetic modeling of reactions between the Ti-O-Cl gas phase species using the B98 or B97-1 method.. Kinetic modeling of reactions between the gas phase species and the surfaces of the rutile, brookite, and anatase TiO 2 solid surfaces. Conclusions Accurate thermodynamic data of 28 Ti-O-Cl species were obtained at the coupled-cluster level of theory. Calculations of 42 density functional theory (DFT) methods were compared with the coupled-cluster results. B98 and B97-1 methods were found to be the most accurate among the 42 DFT methods. The calculations of the 42 DFT methods were compared to Dixon’s coupled- cluster calculations of the Ti-O-Cl-H species. B98 and B97-1 are still the most accurate among all assessed DFT methods. For molecular complexes, the inclusion of the empirical description of the dispersion energy may enhance the accuracy of the calculations. Dye sensitized solar cell Toothpaste (whitening agent) Sol-gel method by mixing CH 3 CH 2 OH, CH 3 COOH, Ti[OCH(CH 3 ) 2 ] 4. cheaper faster Self-cleaning: with vs. without TiO 2 coating Results and Discussion Reactions between the gas-phase species and the TiO 2 surfaces. 3 Flame synthesis 1 TiCl 4 + O 2 + CH 4 → TiO 2 (solid) + CO 2 + H 2 O + HCl Acknowledgements K.T. Lam thanks the CWU School of Graduate Studies and Research for the Undergraduate Research Fellowship. Department of Chemistry, Central Washington University.