posted on 2007-10-11, 00:00authored byNada M. Dimitrijevic, Zoran V. Saponjic, Bryan M. Rabatic, Oleg G. Poluektov, Tijana Rajh
The continuous wave and pulsed electron paramagnetic resonance study of the photogenerated charges in
differently shaped anatase nano-objects dispersed in aqueous solution is presented. Excitation of TiO2 nano-objects (spherical, faceted, rods, and bricks) at temperatures <80 K results in the formation of paramagnetic
species that correspond to electrons trapped at lattice titanium within the bulk, (Ti3+)latt, and holes trapped at
oxygen atoms at the surface of nano-objects, as confirmed by the electron spin echo envelope modulation
technique. The distortion of the Ti−O bond, which is a result of reconstruction of the surface of nano-objects, causes variations in g-tensor values and spin relaxation processes of lattice-trapped electrons. On the
other hand, size and shape do not affect spin−spin relaxation times of surface-trapped holes as it was found
that relaxation is determined by dipolar coupling with 1H nuclei from surrounding water.