부산대학교 도서관

We report up-conversion emission from an aqueous solution of YVO4:Yb3+,Er3+nanocrystals synthesized by an original method that produces nanoparticles with excellent crystallinity and no porosity. We show that these YVO4:Yb3+,Er3+nanocrystals are not very sensitive to nonradiative relaxations, leading to a high green-to-red emission ratio of 6.3. Using a comparison with YVO4:Eu3+particles, we determined the quantum yield of the up-conversion emission of the aqueous YVO4:Yb3+,Er3+dispersion to be 0.09 ± 0.04% for an excitation intensity of only 0.55 kW·cm−2at 970 nm. Furthermore, single YVO4:Yb,Er particles with an estimated size down to 10 nm can be detected using a wide-field microscope under a 970 nm, 8 kW·cm−2excitation. Because of their unexpectedly high up-conversion emission without intermittency, their water dispersibility, and their photostability, YVO4:Yb3+,Er3+nanoparticles are highly appropriate both for single-biomolecule and for in vivo imaging.