title: Dynamics of localized charges in dopamine-modified TiO(2) and their effect on the formation of reactive oxygen species.
abstract: Modification of TiO(2) nanoparticles with dopamine enables harvesting of visible light and promotes spatial separation of charges. The formation of reactive oxygen species (OH, (1)O(2), O(2)(-), HO(2), H(2)O(2)) upon illumination of TiO(2)/dopamine was studied using complementary spin-trap EPR and radical-induced fluorescence techniques. The localization of holes on dopamine suppresses oxidation of adsorbed water molecules at the surface of nanoparticles, and thus formation of OH radicals. At the same time, dopamine does not affect electronic properties of photogenerated electrons and their reaction with dissolved oxygen to produce superoxide anions. Superoxide anions are proposed to generate singlet oxygen through dismutation reaction, resulting in a low yield of (1)O(2) detected.
authors.affiliation: Center for Nanoscale Materials, and Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA. Dimitrijevic@anl.gov
authors.forename: Nada M
authors.initials: NM
authors.lastname: Dimitrijevic
authors.forename: Elena
authors.initials: E
authors.lastname: Rozhkova
authors.forename: Tijana
authors.initials: T
authors.lastname: Rajh
mesh_terms: D003497:Cyclic N-Oxides / Q000737:chemistry; D004298:Dopamine / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005456:Fluorescent Dyes; D017665:Hydroxyl Radical / Q000737:chemistry; D018796:Immunoconjugates / Q000737:chemistry; D007074:Immunoglobulin G / Q000737:chemistry; D008958:Models, Molecular; D053758:Nanoparticles / Q000737:chemistry; D017382:Reactive Oxygen Species / Q000737:chemistry*; D026082:Singlet Oxygen / Q000737:chemistry; D013113:Spin Labels; D013481:Superoxides / Q000737:chemistry; D014025:Titanium / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D003497:Cyclic N-Oxides; D005456:Fluorescent Dyes; D018796:Immunoconjugates; D007074:Immunoglobulin G; D017382:Reactive Oxygen Species; D013113:Spin Labels; D014867:Water; D013481:Superoxides; C009495:titanium dioxide; D026082:Singlet Oxygen; D017665:Hydroxyl Radical; D014025:Titanium; C001803:tempol; D004298:Dopamine