Investigation on the red shift of charge transfer excitation spectra for nano-sized Y2O3:Eu3+

► Based upon the local structure data, the differences of energy bands between bulk and nano-sized Y2O3:Eu3+ have been presented. ► The differences in configurational coordinate diagrams for the optical centers in bulk and nano-sized Y2O3:Eu3+ has been given in this Letter. ► The theories on the CT energy that apply to bulk phosphors are equally applicable for nano-sized phosphors, and the red shift of the CT excitation spectra is originated from the changes in specific parameters for nano-sized phosphors.