Dipole-induced band-gap reduction in an inorganic cage.
Metal-doped polyoxotitanium cages are a developing class of inorganic compounds which can be regarded as nano- and sub-nano sized molecular relatives of metal-doped titania nanoparticles. These species can serve as models for the ways in which dopant metal ions can be incorporated into metal-doped titania (TiO2 ), a technologically important class of photocatalytic materials with broad applications in devices and pollution control. In this study a series of cobalt(II)-containing cages in the size range ca. 0.7-1.3 nm have been synthesized and structurally characterized, allowing a coherent study of the factors affecting the band gaps in well-defined metal-doped model systems. Band structure calculations are consistent with experimental UV/Vis measurements of the Tix Oy absorption edges in these species and reveal that molecular dipole moment can have a profound effect on the band gap. The observation of a dipole-induced band-gap decrease mechanism provides a potentially general design strategy for the formation of low band-gap inorganic cages.
Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (UK); Department of Chemistry, Tongji University, 1239 Siping Road, Shanghai 20092 (P. R. China).
Yaokang
Y
Lv
Jun
J
Cheng
Alexander
A
Steiner
Lihua
L
Gan
Dominic S
DS
Wright
band gap; cobalt; polyoxometalates; structure elucidation; titanium