An Ultrafast and Room-Temperature Strategy for Kilogram-Scale Synthesis of Sub-5 nm Eu3+ -doped CaMO4 Nanocrystals with a Photoluminescence Quantum Yield Exceeding 85

Abstract

Rare earth-doped metal oxide nanocrystals have a high potential in display, lighting, and bio-imaging, owing to their excellent emission efficiency, superior chemical, and thermal stability. However, the photoluminescence quantum yields (PLQYs) of rare earth-doped metal oxide nanocrystals have been reported to be much lower than those of the corresponding bulk phosphors, group II-VI, and halide-based perovskite quantum dots because of their poor crystallinity and high-concentration surface defects. Here, an ultrafast and room-temperature strategy for the kilogram-scale synthesis of sub-5 nm Eu³⁺ -doped CaMoO₄ nanocrystals is presented, and this reaction can be finished in 1 min under ambient conditions. The absolute PLQYs for sub-5 nm Eu³⁺ -doped CaMoO₄ nanocrystals can reach over 85%, which are comparable to those of the corresponding bulk phosphors prepared by the high-temperature solid state reaction. Moreover, the as-produced nanocrystals exhibit a superior thermal stability and their emission intensity unexpectedly increases after sintering at 600 °C for 2 h in air. 1.9 kg of Eu³⁺ -doped CaMoO₄ nanocrystals with a PLQY of 85.1% can be obtained in single reaction.

Keywords: CaMoO 4; kilogram-scale; ligand-assisted co-precipitation; rare earth doping; room-temperature synthesis.