Spectral band shifts in the electronic spectra of rare earth sesquioxide nanomaterials doped with europium

The UV-visible and vacuum ultraviolet emission and excitation spectra of Y₂O₃:Eu^3- (1 and 0.1 atom %) nanomaterials, prepared by combustion syntheses with use of glycine or hydrazine, have been recorded in order to investigate spectral band shifts as a function of particle size. FT-IR spectra and site-selective emission spectra at low temperature show the presence of impurities for all of these samples, with the least impurities for the samples prepared using stoichiometric ratios of reactants, where (i) the relative intensity of the free exciton (FE) and the charge transfer (CT) bands changes significantly with Eu³⁺ concentration, (ii) there is a small red-shift of the CT band position with decreasing particle size, and (iii) the shifts of the FE and band-to-band (CB) transitions are within a separation of 116 cm^-1 (14 meV) at room temperature for samples of size 20-40 nm. The band positions change for samples synthesized when not using stoichiometric ratios of reactants. © 2009 American Chemical Society.