Analysis of Excitation Energy Transfer in LaPO(4) Nanophosphors Co-Doped with Eu(3+)/Nd(3+) and Eu(3+)/Nd(3+)/Yb(3+) Ions

Nanophosphors are widely used, especially in biological applications in the first and second biological windows. Currently, nanophosphors doped with lanthanide ions (Ln(3+)) are attracting much attention. However, doping the matrix with lanthanide ions is associated with a narrow luminescence bandwidth. This paper describes the structural and luminescence properties of co-doped LaPO(4) nanophosphors, fabricated by the co-precipitation method. X-ray structural analysis, scanning electron microscope measurements with EDS analysis, and luminescence measurements (excitation 395 nm) of LaPO(4):Eu(3+)/Nd(3+) and LaPO(4):Eu(3+)/Nd(3+)/Yb(3+) nanophosphors were made and energy transfer between rare-earth ions was investigated. Tests performed confirmed the crystal structure of the produced phosphors and deposition of rare-earth ions in the structure of LaPO(4) nanocrystals. In the range of the first biological window (650–950 nm), strong luminescence bands at the wavelengths of 687 nm and 698 nm ((5)D(0) → (7)F(4):Eu(3+)) and 867 nm, 873 nm, 889 nm, 896 nm, and 907 nm ((4)F(3/2) → (4)I(9/2):Nd(3+)) were observed. At 980 nm, 991 nm, 1033 nm ((2)F(5/2) → (2)F(7/2):Yb(3+)) and 1048 nm, 1060 nm, 1073 nm, and 1080 nm ((4)F(3/2) → (4)I(9/2):Nd(3+)), strong bands of luminescence were visible in the 950 nm–1100 nm range, demonstrating that energy transfer took place.