Synthesis and Characterization of Multicolor Lanthanide Luminescent Nanoparticles Based on Dipicolinic Acid

Multicolor SiO2 nanoparticles containing different lanthanide complexes were prepared by the reverse microemulsion method. The lanthanide complexes are binary complexes of Tb(III), Eu(III) or Dy(III) with dipicolinic acid; dipicolinic acid is the common luminescent ligand. These nanoparticles are highly luminescent in aqueous solution, and have a long fluorescence lifetime of millisecond level for the time-resolved fluorescence assays. The emission wavelength and intensity of multicolor nanoparticles can be adjusted by changing the molar ratio of mixed complexes. Because of the use of a same ligand of dipicolinic acid, they can be excited simultaneously by a single wavelength. Compared with other lanthanide nanolabels, the lanthanide nanoparticles based on dipicolinic acid are non-complicated organic synthesis, easy to prepare and inexpensive. These features made them easier to be used in multiplexed bioassays and ultrasensitive time-resolved fluorescence assays and imaging.