A study of the optical properties of metal-doped polyoxotitanium cages and the relationship to metal-doped titania.
To what extent the presence of transition metal ions can affect the optical properties of structurally well-defined, metal-doped polyoxotitanium (POT) cages is a key question in respect to how closely these species model technologically important metal-doped TiO2. This also has direct implications to the potential applications of these organically-soluble inorganic cages as photocatalytic redox systems in chemical transformations. Measurement of the band gaps of the series of closely related polyoxotitanium cages [MnTi14(OEt)28O14(OH)2] (1), [FeTi14(OEt)28O14(OH)2] (2) and [GaTi14(OEt)28O15(OH)] (3), containing interstitial Mn(II), Fe(II) and Ga(III) dopant ions, shows that transition metal doping alone does not lower the band gaps below that of TiO2 or the corresponding metal-doped TiO2. Instead, the band gaps of these cages are within the range of values found previously for transition metal-doped TiO2 nanoparticles. The low band gaps previously reported for 1 and for a recently reported related Mn-doped POT cage appear to be the result of low band gap impurities (most likely amorphous Mn-doped TiO2).
Chemistry Department, Cambridge University, Lensfield Road, Cambridge CB2 1EW, UK. dsw1000@cam.ac.uk.
Yaokang
Y
Lv
Jun
J
Cheng
Peter D
PD
Matthews
Juan Pedro
JP
Holgado
Janina
J
Willkomm
Michal
M
Leskes
Alexander
A
Steiner
Dieter
D
Fenske
Timothy C
TC
King
Paul T
PT
Wood
Lihua
L
Gan
Richard M
RM
Lambert
Dominic S
DS
Wright