Non-cytotoxic Dy3+ activated La10W22O81 nanophosphors for UV based cool white LEDs and anticancer applications

Abstract

White-light-emitting La10W22O81 (LWO): xDy3+ (0.5 ≤ x ≤ 10 mol%) nanocrystalline phosphors were developed by a facile hydrothermal assisted solid-state reaction. X-ray diffraction (XRD) pattern indicated that the prepared samples adopted orthorhombic crystal structures. The agglomeration of uniform nanorods was identified from the FE-SEM analysis of the optimized LWO: 1.5 mol% Dy3+ nanocrystalline phosphors. Additionally, transmission electron microscope, scanning transmission electron microscopy, selected area electron diffraction, and X-ray photoelectron spectroscopy were employed to explore the surface morphology, size, interplanar distance, and chemical composition with valence states of the LWO: 1.5 mol% Dy3+ phosphors, respectively. By exciting with 387 nm, the LWO: Dy3+ emission spectra showed two intense peaks at 476 nm (4F9/2→6H15/2) and 571 nm (4F9/2→6H13/2) and a shoulder peak at 659 nm (4F9/2→6H11/2). Optimum emission intensity was achieved for 1.5 mol% Dy3+ in the LWO host lattice. The luminescence quenching beyond 1.5 mol% Dy3+ is attributed to the dipole–dipole interactions when the Dy3+ (donor) and Dy3+ (acceptor) ions are at a critical distance of 58.53 Å. Photometric studies were conducted to evaluate the performance and practical applicability of the phosphors. The CIE chromaticity diagram suggests that the LWO: 1.5 mol% Dy3+ nanophosphor conspicuously exhibits cool white light. Therefore, this material could be a promising and potential white light-emitting nanocrystalline phosphor material for white light emitting diodes (LEDs) under near-UV excitation. In addition, the toxicity of the optimized nanophosphor in normal WI-38 lung fibroblast cells and MCF-7 breast cancer cells was examined. Surprisingly, LWO: 1.5 mol% Dy3+ nanophosphor was found to be non-cytotoxic to normal cells, but extremely toxic to cancer cells. Therefore, the nanophosphor materials can be considered potential candidates for biomedical applications, particularly for cancer treatment.