Morphology evolution, energy transfer and multicolor luminescence of lanthanide-doped Ba2LaF7 nanocrystals via a one-step hydrothermal synthesis

摘要

Lanthanide-doped Ba2LaF7 nanocrystals were successfully synthesized via a one-step hydrothermal method. The phase, size and shape of the lanthanide-doped Ba2LaF7 nanocrystals were systematically investigated by controlling the fluorine source, additive, lanthanide doping, synthesis method and temperature. Regular hexagonal Ba2LaF7 nanocrystals with a side length of 60 nm were obtained by using NaBF4 as the fluorine source. A variety of lanthanide ions (Ho3+, Er3+, Tm3+, Dy3+, Eu3+, Tb3+, Ce3+, and Sm3+) was successfully doped into the Ba2LaF7 host, which showed abundant luminescent colors due to the intrinsic emission of the lanthanide ions. Because of the emission spectrum of Tb3+ (D-5(4) -> F-7(j)) having obvious overlap with the Eu3+ excitation spectrum (F-7(0,1) -> D-5(0,1,2)), the excited state energy of Tb3+ can be transferred to Eu3+. Under ultraviolet excitation, the energy transfer from Tb3+ to Eu3+ in the Ba2LaF7 matrix occurs mainly via the dipole-quadrupole mechanism. The regulation of luminescent color was achieved from green to warm yellow to yellow orange and finally to red by changing the doping concentration of Eu3+ ions from 0.1% to 7%, respectively. The obtained Ba2LaF7:Ln(3+) nanocrystals have potential application in multicolor lighting and displays.