Femtosecond relaxation of photoexcited states in nanosized semiconductor particles of iron oxides

Relaxation of photoexcited states in nanosized semiconductor particles of iron oxides was studied by femtosecond laser photolysis techniques: (1) in an aqueous colloidal solution of alpha-Fe2O3; (2) in Fe2O3 particles in the Naflon((R)) cation-exchange polymeric membrane; (3) in an aqueous colloid of gamma-Fe2O3; and (4) in nanocrystals of ferrihydrite 5Fe(2)O(3).9H(2)O, which are contained in the protein shell of ferritine. The photoinduced excited states relax at the femtosecond and picosecond time scale. The spectra of photoinduced absorption of photoexcited states and the relaxation dynamics in the studied iron oxides weakly depend on the structure and surface environment of a nanoparticle.