Dual mode emission of core-shell rare earth nanoparticles for fluorescence encoding

The demands for multiplexed biological detection have driven the development of fluorescence encoding nanoprobes. We have synthesized water-soluble dual mode emission core-shell rare earth nanoprobes (∼30 nm) for fluorescence encoding. The nanoprobes were composed of ytterbium (Yb), erbium (Er) and/or thulium (Tm) ions co-doped heterogeneous NaYF₄/NaLuF₄ nanocrystals as cores and amorphous SiO₂ embedded with europium (Eu) or terbium (Tb) complexes as shells. Excited by both infrared light and ultraviolet light, the nanoprobes exhibited dual characteristic emissions, which enable a novel spectral encoding strategy. The core nanocrystals exhibited tunable up-conversion emissions through various lanthanide ions doping. Combining these multiple upconversion emissions of core nanocrystals with downconversion emissions of shell containing rare earth complexes, a large amount of distinct fluorescence codes can be generated.