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.

A Room-Temperature Strategy to Synthesize Ce/Tb-Codoped NaYF4 Nanoparticles with a Photoluminescence Quantum Yield Exceeding 50%

“…Consequently, the preparation of highly luminescent and ultrasmall NaYF 4 :RE 3+ nanocrystals remains a significant challenge. To our knowledge, there are seldom reports on the preparation of highly luminescent RE-doped nanocrystals at room temperature, − especially from the ultrasmall RE-doped fluoride nanocrystals (<5 nm).…”

“…Recently, we have developed a room-temperature and universal ligand-assisted coprecipitation method to rapidly synthesize extremely small and highly luminescent Ce/Te-doped LaPO 4 nanoparticles, Eu-doped YVO 4 nanoparticles, and Eu/Tb-doped CaMoO 4 nanoparticles . Short-chain butyric acid and butylamine were used as the capping agents, and these room-temperature-synthesized RE-doped phosphate, vanadate, and molybdate nanoparticles have particle sizes less than 5 nm and PLQYs in the range of 60–85%.…”

“…Recently, we have developed a room-temperature and universal ligand-assisted coprecipitation method to rapidly synthesize extremely small and highly luminescent Ce/Tedoped LaPO 4 nanoparticles, 33 Eu-doped YVO 4 nanoparticles, 34 and Eu/Tb-doped CaMoO 4 nanoparticles. 35 Short-chain butyric acid and butylamine were used as the capping agents, and these room-temperature-synthesized RE-doped phosphate, vanadate, and molybdate nanoparticles have particle sizes less than 5 nm and PLQYs in the range of 60−85%. In this paper, this facile and general ligand-assisted coprecipitation method was extended to synthesize NaYF 4 :Ce 3+ ,Tb 3+ down-conversion nanocrystals with an average size of 2.7 nm by using hexanoic acid and hexylamine as capping agents.…”

Low-temperature in situ preparation of Eu3+/Tb3+-doped CaMoO4/SrMoO4 nanoparticle thin films and their application in anti-counterfeiting

“…36–38 In particular, the nanocrystals with high photoluminescence quantum yields have been successfully synthesized on a large scale at low temperatures. 39–42 This compelling evidence suggests that rare earth-doped molybdates can exhibit favorable luminescent performance even at lower temperatures. The alkaline-earth metal molybdates belong to the tetragonal crystal system with a scheelite structure, exhibiting excellent chemical and thermodynamic stability as well as superior luminescent performance.…”