Infrared cascade and cooperative multicolor upconversion emissions in Y₈V₂O₁₇:Eu:Yb nanophosphors

This work reports on the efficient cooperative upconversion and infrared cascade downconversion emissions in a novel Y₈V₂O₁₇:Eu:Yb nanophosphor. The excitation with UV light produces emission in the 950-1000 nm region, corresponding to the Yb³⁺:²F₅/₂-->²F₇/₂ transition, as well as visible emissions of the Eu³⁺ ion. Time-resolved spectroscopy measurements revealed that the mechanism responsible for this transition is the efficient cascade nonresonant energy transfer from VO₄³-->Eu-->Yb. When the same nanophosphor is excited with 976 nm radiation, bright reddish upconversion emission of the Eu³⁺:⁵DJ-->⁷FJ transition is observed as consequence of the Yb + Yb-->Eu cooperative energy transfer mechanism, which was established by analyzing the emission power dependence and the time-resolved spectroscopy of radiative transitions.