Quantitative Luminescence Switching in CePO4:Tb by Redox Reactions

Luminescence-switching behaviors of CePO 4:Tb 3+ upon redox reactions were examined using KMnO 4 and l (+)-ascorbic acid as an oxidant and a reductant, respectively. Powdery nanorod-like CePO 4:Tb 3+ particles were synthesized by liquid-phase reactions of rare-earth ions and phosphate ions in aqueous solutions at low temperatures. According to X-ray diffractometry, X-ray photoelectron spectroscopy, and transmission electron microscopy, the oxidizing treatment of CePO 4:Tb 3+ was found to bring about partial oxidation of Ce 3+ to Ce 4+ and a small degree of structural damage in the particle surface, which could be recovered by the subsequent reducing treatment. Photoluminescence (PL) intensity of CePO 4:Tb 3+ due to 5 D 4 → 7 F J ( J = 3−6) electronic transitions of Tb 3+ was decreased with increasing KMnO 4 concentration in an exponential manner, resulting from excitation cutoff by an intervalence Ce 3+ → Ce 4+ charge transfer and emission cutoff by a Ce 3+ absorption red-shifted to the visible region. Reversely, PL intensity was increased also in the exponential manner by increasing the l (+)-ascorbic acid concentration in reducing the previously oxidized CePO 4:Tb 3+, thereby achieving the quantitative, repetitive luminescence switching. Our results demonstrate that the luminescence switching is regarded as a surface phenomenon without a whole change of structure and valence in the CePO 4:Tb 3+ material.