Reduction of Eu-activated nanoparticles by unique TCRA treatment

The Eu2+ ion-doped CaF2 nanoparticles were synthesized by means of the sol-gel method. As prepared, the typical luminescence due to the intra 4f-f transitions of only Eu3+ ion was observed. The TCRA (thermal-carbon reducing atmosphere) treatment using activated carbon realized efficient reduction from Eu3+ to Eu2+ ions. Afterward TCRA treatment, a strong and broad luminescence with the peak at 425nm due to the parity allowed 4f7-4f65d1 transition of Eu2+ ion was observed. The average size of particles as estimated using XRD patterns proportionally increased from 15 to 120nm with increasing heating temperatures from 300 to 700 deg C. The particle sizes were evaluated by the AFM morphologies exhibiting a good accordance with the results from XRD.