NaYbF4@CaF2 core-satellite upconversion nanoparticles: one-pot synthesis and sensitive detection of glutathione.

A new class of core-satellite upconversion nanoparticles (UCNPs) formed through a kinetically controlled oriented attachment is presented. The core-satellite UCNPs comprising an optically active α-NaYbF4 core and several CaF2 satellites are synthesized by a one-pot sequential injection technique. Compared to conventional core-shell UCNPs, these core-satellite UCNPs show larger surface-to-volume ratios and are suitable for further surface modifications. As a proof-of-concept, a biosensing system is constructed by coating MnO2 nanosheets on the α-NaYbF4:Tm@CaF2 core-satellite UCNPs for high-sensitivity biothiol detection. These core-satellite UCNPs show great potential in the development of UCNP-based nanohybrids for biosensing, multimodal imaging and drug delivery.