Effect of charge transfer band on luminescence properties of Yb doped   Y2O3 nano particles for blue-far yellow emission
  The photoluminescence properties of Yb doped Y2O3 nanoparticles are investigated in visible region. The presence of peaks at 335 nm and 370 nm in the excitation spectra of bulk as well as in nano Yb: Y2O3 and their absence in pure Y2O3 confirm its origin due to Yb3+ dopant. The Yb doping in nano Y2O3 not only modify the charge transfer bands (CTB) but also helps in transition of electron from these CTBs to ground 2F5/2 and 2F7/2 levels of Yb. This results in strong intense broad emission from ~400 to ~650 nm (white light emission range) for 335 nm excitation. 
Pratik Deshmukh, S. Satapathy, Anju Ahlawat, Khemchand Sahoo, and P.   K. Gupta
cond-mat.mtrl-sci