Solvothermal synthesis of Zn2GeO4:Mn2+ nanophosphor in water/diethylene glycol system

The influence of aging of the suspension containing the amorphous precusors on structural, compositional and photoluminescent properties is studied to understand the mechanism on the formation of Zn2GeO4:Mn2+ nanoparticles during the solvothermal reaction in the water/diethylene glycol mixed solvent. Aging at 200 degrees C for 20 min forms the crystalline Zn2GeO4 nanorods and then they grow up to similar to 50 nm in mean length after aging for 240 min. Their interplanar spacing of (410) increases with increasing the aging time. The photoluminescence intensity corresponding to the d-d transition of Mn2+ increases with increasing the aging time up to 120 min, and then decreases after aging for 240 min. The photoluminescence lifetime decreases with increasing the aging time, indicating the locally concentrated Mn2+ ions. These results reveal that Mn2+ ions gradually replace Zn2+ ions near surface through repeating dissolusion and precipitation processes during prolonged aging after the complete crystallization of Zn2GeO4. (C) 2011 Elsevier Inc. All rights reserved.