Europium-Doped Calcium Silicate Nanoparticles as High-Quantum-Yield Red-Emitting Phosphors

Europium ion-activated calcium silicate phosphors (Ca2SiO4:Eu3+) with sharp red-light emissionwerefabricated via the hydrothermal method. The size of Ca2SiO4:Eu3+ phosphors was controlled between20 and 200 nm by precursor silicate particle sizes. Systematic studiesto determine morphology, crystal phase, and photoluminescence (PL)were carried out for all the phosphors, and their optical efficiencieswere compared. We found that the luminescence intensity and emissionwavelength of Ca2SiO4:Eu3+ phosphorsdepend on their particle sizes. Particularly, the Ca2SiO4:Eu3+ synthesized with 20 nm silica seed containsthe most intense red emission, high color purity, and high PL quantumyield. For the 20 nm-sized Ca2SiO4:Eu3+ phosphor, PL quantum yields are measured to be above 87.95% andhigh color purity of 99.8%. The unusually high intensity of D-5(0) -> F-7(4) emission (712 nm)is explained by structural distortion arising from silicate particlesize reductions. We show that the obtained phosphor is a suitablecandidate for solid-state lighting as a red component through CIEchromaticity coordinate and color purity measurements. Furthermore,the Ca2SiO4:Eu3+ particles are examinedfor their validity as promising bio-imaging probes through cell labelingand imaging experiments and biodegradability studies.

Automated summary

Europium ion-activated calcium silicate phosphors (Ca2SiO4:Eu3+) with sharp red-light emission were synthesized by the hydrothermal method. The particle size of Ca2SiO4:Eu3+ phosphors was controlled between 20 and 200 nm by adjusting the precursor silicate particle sizes. The luminescence intensity and emission wavelength of the phosphors were found to depend on their particle sizes, with the 20 nm-sized Ca2SiO4:Eu3+ phosphor exhibiting the most intense red emission, high color purity, and high PL quantum yield. The suitability of the obtained phosphor as a red component for solid-state lighting and its potential as bio-imaging probes were also investigated.