Energy transfer from benzoic acid to lanthanide ions in benzoic acid-functionalized lanthanide-doped CaF2 nanoparticles

The preparation of benzoic acid-functionalized CaF2:Ln3+ (Ln = Eu or Tb) nanoparticles and their sensitized luminescence are described in this report. First, to achieve sufficient proof for energy transfer from benzoic acid (BA) to lanthanide ions doped in nanoparticles, we employ Eu3+ as the microscopic probe and investigate the luminescent spectra of benzoic acid-functionalized CaF2:Eu3+ (BA-CaF2:Eu3+) nanoparticles. Next, to further reveal the difference between sensitized luminescence and common luminescence for Eu3+ doped in CaF2 nanoparticles, we study the emission spectra of BA-CaF2:Eu3+ nanoparticles excited at 286 nm and 397 nm, respectively. Finally, we analyze and compare the luminescent spectra of BA-CaF2:Tb3+ and CaF2:Ce3+, Tb3+ nanoparticles in detail. Our results indicate that both Eu3+ and Tb3+ doped in CaF2 nanoparticles can be efficiently sensitized through benzoic acid.