Robust color purity of reddish-orange emission from Sm3+-activated La10W22O81 biocompatible microphosphors for solid state lighting and anticancer applications

Abstract

We synthesized reddish-orange luminescent La10W22O81 (LWO):Sm3+ microphosphors by hydrothermal-assisted solid-state reaction. X-ray diffraction analysis reveals that all the studied phosphors crystallize in an orthorhombic structure in the Pbcn space group (60). Field emission scanning electron microscopy indicates that the LWO:1.5 mol% Sm3+ phosphor displays a smooth-surfaced hexagonal rod-like shape, with a closed shape at both ends, and high-resolution transmission electron microscopy demonstrates a robust crystalline structure. The chemical composition and valence states of the phosphor were investigated using X-ray photoelectron spectroscopy. At 403 nm excitation, LWO:1.5 mol% Sm3+ exhibits maximum intensity with the strongest band at 596 nm (4G5/2 → 6H7/2) in the reddish-orange region. The intensity of Sm3+ emission decreases beyond 1.5 mol% owing to concentration quenching regulated by dipole？quadrupole interaction between Sm3+ ions. The optimized microphosphor LWO:1.5 mol% Sm3+ exhibits color coordinates (0.5760, 0.4207), which is close to that of the Amber LED-NSPAR 70 BS (0.570, 0.420), displaying the highest color purity of 99.2% and correlated color temperature of 1694 K. In addition, both breast cancer cells MCF-7 and normal lung fibroblasts WI-38 were tested for toxicity with the optimized microphosphor. It is found that the LWO:1.5 Sm3+ microphosphor is extremely toxic to cancer cells, but not to normal cells. Based on these results, LWO:Sm3+ microphosphor can serve as a biomedical candidate for the treatment of cancer, as well as a potential multicolor emitting material for w-LEDs.