Influence of Defects on Photoconductivity and Photocatalytic Activity of   Nitrogen-Doped Titania
  Samples of nitrogen-doped titanium dioxide (anatase, $0.2 \leq N \leq 1.0~wt\%$) prepared by the sol-gel method were investigated using X-band EPR spectroscopy, photoconductivity and photocatalysis measurements. $N\bullet$ and $NO\bullet$ paramagnetic defects in N-TiO2 have been observed; their concentrations and spin-Hamiltonian parameters were calculated. An increase both in the rate of the generation of free charge carriers and in the rate of photocatalysis was found in N-TiO2 in contrast with non-doped titania under visible light. The correlation of the density of the observed radicals with the photoconductivity and photocatalysis data is discussed. 
A. A. Minnekhanov, N. T. Le, E. A. Konstantinova, P. K. Kashkarov
cond-mat.mtrl-sci cond-mat.mes-hall