Luminescence enhancement and quenching by codopant ions in lanthanide doped fluoride nanocrystals

Luminescence enhancement (LE) and quenching for lanthanide (Ln) doped nanocrystals is obtained by a second Ln(3+) ion doping method. Singly or doubly doped LaOF, LaF(3) and NaYF(4) nanocrystals are studied in detail under selective or two-color excitations. The underlying reason for LE by codoping is explored, and a mechanism of the enhancement based on the low local point symmetry effect of the matrix is proposed. It is found that the modification of the local environment induced by dopant ions can result in LE if the non-radiative relaxation probability can be ignored. The observations reported here should be useful for improving the quality of Ln(3+) doped nanomaterials.