Theoretical study of I-4(13/2) -> I-4(15/2) luminescence quenching by OH for LaF3 : Er3+ nanoparticles in solution

The processes of I-4(13/2)-> I-4(15/2) luminescence quenching by OH vibrations are investigated for LaF3:Er3+ nanoparticles dissolved in solution. The energy transfer (ET) rates, involving the I-4(13/2)-> I-4(15/2) transition of Er3+ and the first overtone absorption of OH, are estimated. In order to calculate the relevant OH transition matrix elements, a model for the OH vibration in solution is developed with the use of a Morse potential. Various multipole-multipole ET mechanisms are considered and their dependences on the distance between Er3+ and OH are studied. Based on these ET mechanisms, the ET rates from an Er3+ in the nanoparticle to all the OH in solution are estimated and compared with respect to changes in location of the ion, size of the nanoparticle and OH concentration in solution. The effective I-4(13/2)-> I-4(15/2) luminescence decay times that are contributed by all the Er3+ in the nanoparticle are then calculated with different Er3+ concentrations. The calculations satisfactorily account for experimental observations.