Morphological control and upconversion luminescence of hollow CeO2 and Er3+–Yb3+ codoped CeO2 particles

Abstract

Hollow CeO₂ particles with three types of morphologies (rod, rhombus, and dumbbell) were synthesized by retention of the morphology of Ce(OH)CO₃ precursors during interfacial reactions of Ce(OH)CO₃ with aqueous hydrogen peroxide solution. The wall areas of the hollow CeO₂ particles comprised crystalline CeO₂ nanoparticles. The pH of the aqueous hydrogen peroxide solution played a crucial role in the formation of the hollow structure. The mechanism underlying formation of the hollow structure was also evaluated. The hollow structures of the CeO₂ particles with rod-shaped morphology were maintained even after calcination at 1000 °C, although the structures collapsed after calcination at 1250 °C. Similar reactions using CePO₄ nanorods and plate-shaped Ce₂(CO₃)₃·8H₂O particles instead of Ce(OH)CO₃ particles demonstrated that the plate-shaped Ce₂(CO₃)₃·8H₂O particles could be transformed into plate-shaped CeO₂ particles, although the CePO₄ nanorods were non-reactive. CeO₂ rattle particles composed of CeO₂ porous wall and dense CeO₂ rod were also synthesized. Furthermore, by utilizing the excellent thermal stability of the hollow CeO₂ particles with rod-shaped morphology, hollow Er³⁺–Yb³⁺ codoped CeO₂ rods that display upconversion luminescence were synthesized by hydrogen peroxide treatment and subsequent calcination of Er³⁺–Yb³⁺ codoped Ce(OH)CO₃ rods at 1000 °C.