Colloidal LaF3 : Yb,Er, LaF3 : Yb,Ho and LaF3 : Yb,Tm nanocrystals with multicolor upconversion fluorescence

The IR-to-visible upconversion fluorescent nanocrystals, Yb-Er, Yb-Ho and Yb-Tm co-doped LaF3 were chemically synthesized and investigated. The ligand-capped nanocrystals were easily dispersed in organic solutions and subsequently formed a transparent colloidal solution. Under 980 nm IR excitation, green, red and blue emission bands were observed from these colloidal solutions, respectively. Compared with the recently reported colloidal NaYF4:Yb,Er nanocrystals, our nanocrystals produced a fluorescence output which was 5 times higher. These nanocrystals have potential applications as bio- probes and displays.