Room-Temperature, Ultrafast, and Aqueous-Phase Synthesis of Ultrasmall LaPO 4 :Ce 3+ , Tb 3+ Nanoparticles with a Photoluminescence Quantum Yield of 74.

LaPO 4 :Ce 3+ , Tb 3+ nanoparticles with a particle size of 2.7 nm are prepared by a facile room-temperature ligand-assisted coprecipitation method in an aqueous solution. Short-chain butyric acid and butylamine are used as binary ligands and play a critically important role in the synthesis of highly luminescent LaPO 4 :Ce 3+ , Tb 3+ nanoparticles. The absolute photoluminescence quantum yield as high as 74% can be achieved for extremely small LaPO 4 :Ce 3+ , Tb 3+ nanoparticles with an optimal composition of La 0.4 PO 4 :Ce 0.1 3+ , Tb 0.5 3+ , which is different from La 0.4 PO 4 :Ce 0.45 3+ , Tb 0.15 3+ for bulk phosphor. The energy transfer from Ce 3+ ions to Tb 3+ ions is investigated in sub-3 nm LaPO 4 :Ce 3+ , Tb 3+ nanoparticles, and Ce 3+ ion emission is almost completely suppressed. This room-temperature, ultrafast, and aqueous-phase synthetic strategy is particularly suitable for the large-scale preparation of highly luminescent LaPO 4 :Ce 3+ , Tb 3+ nanoparticles. LaPO 4 :Ce 3+ , Tb 3+ nanoparticles (110 g) can be synthesized in one batch, which is perfectly suited to the needs of industrial production.