Comparative optical study of colloidal anatase titania nanorods and atomically thin wires

Abstract

We present results of a comparative study of colloidal anatase titanium oxide nanorods and extremely thin atomic wires of systematically decreasing (2.6 nm down to 0.5 nm) diameter in terms of their optical absorption as well as steady-state and time-resolved photoluminescence. Steady-state photoluminescence spectra of the titania samples show three well-distinguished spectral components, which are ascribed to excitonic emission (4.26 ± 0.2 eV), as well as radiative recombination of trapped holes with electrons from the conduction band (4.04 ± 0.4 eV) and radiative recombination of trapped electrons with holes in the valence band (3.50 ± 0.2 eV) in nanocrystalline anatase TiO₂. Time-resolved photoluminescence measurements point out the existence of different emissive species responsible for the appearance of high-energetic and low-energetic emission peaks of TiO₂ atomic wires and nanorods.