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Amino Acid Adhesion on TiO2 Surface DFT Model

Amino Acid Adhesion on TiO2 Surface DFT Model. Francesco Buonocore Caterina Arcangeli , Massimo Celino , Ivo Borriello ENEA - C.R. Casaccia and NAST Centre Computational Material Science and technology (CMAST) Laboratory www.afs.enea.it/project/cmast

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Amino Acid Adhesion on TiO2 Surface DFT Model

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  1. Amino Acid Adhesion on TiO2 Surface DFT Model Francesco Buonocore CaterinaArcangeli, Massimo Celino, IvoBorriello ENEA - C.R. Casaccia and NAST Centre Computational Material Science and technology (CMAST) Laboratory www.afs.enea.it/project/cmast ”Biosystems, Energy, and Cultural Heritage: Materials Enhancement for technological application” July 3rd 2013 - Universitàdi Roma Tor Vergata

  2. Why density functional theory? • Density functional theory (DFT) let us model the following interactions that molecular dynamics cannot describe: • Covalent bond formation • Electron charge distribution • Therefore we give a close look to the region of the amino acid/TiO2 surface interaction by means of DFT methods

  3. We focus on the following amino acids R D -CH2-COO -NH-C-(NH2)2 Terminal groups of side-chains interacting with TiO2 surface

  4. TiO2 (101) anataserecontruction • Anatase is the most probable phase of TiO2 oxide surface formation • The 101 orientation represents the most stable recontruction in TiO2 anatase phase Low coordinated Ti(5c) and O(2c) on surface layer: they represent the most reactive points of the surface TiO2 (101) anatase reconstructed surface Ti(6c) O(2c) Ti(5c) O(3c) Bulk O are bonded to 3 Ti atoms -> O(3c) Bulk Ti are bonded to 6 O atoms -> Ti(6c)

  5. ARGININE on TiO2(101) anatase: bound configurations 5) O(2c) & O(2c) 4) 2 x O(2c) 3) O(2c) & O(3c) Free ARG O(2c)-H bonds lenght lying in 1.7 – 2.2Å 2) O(2c) Free ARG = 10 Å far away from TiO2 surface

  6. ASPARTIC ACID on TiO2(101) anatase : bound configurations 6) 2 x Ti(5c) COOH towards O(3c) 5) 2 x Ti(5c) COOH towards O(2c) 4) 2 x Ti(6c) Free ASP 2) Ti(5c) Ti-O bonds lenght lying in 1.9 – 2.2Å Free ASP = 10 Å far away from TiO2 surface

  7. ARGININE on TiO2(101) anatase: charge density analysis Electron charge moves on N and H-O bond Electron charge is removed from H and TiO2 Negativecharge density difference charge depletion charge density Positivecharge density difference charge accumulation

  8. ASPARTIC ACID on TiO2(101) anatase: charge density analysis Electron charge moves on O-Ti bond and TiO2 Electron charge is not removed from TiO2 Negativecharge density difference charge depletion charge density Positivecharge density difference charge accumulation

  9. Challenges • The mediation of a water layer can be included in the DFT models • The role of van der Waals interactions can also be investigated • How to include environmental water effects?

  10. Conclusions • The adhesion of the amino acid side-chains to TiO2 substrate has been modeled for arginine and aspartic acid. • The most stable configurations and their binding energies have been calculated. • Arginine (positive ion) adhesion does involve a charge transfer from TiO2 to amino acid. In aspartic acid (negative ion) this effect is reversed. • DFT models provide information complementary to that provided by MD

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