Room‐Temperature and Ultrafast Synthesis of Sub‐4 nm Yb³⁺/Nd³⁺ Ions‐Doped CaMoO₄ Nanocrystals with Near‐Infrared Photoluminescence Quantum Yield of 40%

Abstract Rare‐earth doped metal oxide nanocrystals with high visible luminescence have been widely used in lighting and display applications owing to their low toxicity, and excellent thermal and chemical stability. However, the room‐temperature preparation of near‐infrared (NIR) luminescent rare‐earth doped metal oxide nanocrystals remains a challenge. Herein, sub‐4 nm Yb 3+ /Nd 3+ ‐doped CaMoO 4 nanoparticles are prepared by a facile room‐temperature ligand‐assisted coprecipitation method, which can be completed within 1 min under ambient conditions. Short‐chain butyric acid and butylamine as binary ligands play a crucial role in the synthesis of NIR luminescent nanoparticles. The as‐prepared nanocrystals can be well dispersed in organic solvents such as chloroform since they are capped with butyric acid and butylamine. The energy transfers from ions to Yb 3+ and Nd 3+ ions are systematically investigated in CaMoO 4 :Yb 3+ and CaMoO 4 :Nd 3+ nanoparticles, respectively. More importantly, this ultrafast and room‐temperature synthesis strategy is particularly suitable for the large‐scale preparation of Yb 3+ /Nd 3+ ‐doped CaMoO 4 nanoparticles (≈23 g) with NIR emission, which provides new ideas and possibilities for the commercial production of extremely small and NIR‐emitting nanophosphors.