Particle Size Control of Y2O3 : Eu3+ Prepared via a Coconut Water-Assisted Sol-Gel Method

Eu3+-doped Y2O3 nanoparticles were produced through proteic sol-gel technique, and the adjustment of pH was tested in order to control the particle size of the powders. A strong correlation between the initial pH and the temperature of crystallization was observed, allowing the production of particles with controlled diameter from 4 nm to 50 nm. The samples were characterized by X-ray diffraction, high-resolution transmission electron microscopy, optical microscopy and photoluminescence spectroscopy in both absorption and emission modes. A blue shift of the excitation peak corresponding to energy transfer from Y2O3 host to Eu3+ ions was observed, as the particle size was reduced from 50 to 4 nm. The suppression of a charge transfer band also resulted from the reduction of the particle size. The emission spectrum of the Y2O3:Eu3+ with particles of 50 nm was found to be similar to that of bulk material whereas 4 nm particles presented broadened emission peaks with lower intensities.