Special properties of luminescent magnetic NaGdF4:Yb3+, Er3+ upconversion nanocubes with surface modifications

Abstract

A one-pot process is developed to produce NaGdF₄:Yb³⁺, Er3+ upconversion nanocubes (UCNCs) with amine surface modifications. The photoluminescence and magnetic properties of the amine modified unpconversion nanocubes (UCNCs) were investigated. The emissions of green light at 540 nm and red light at 660 nm are observed under infrared excitation (λ_ex = 980 nm) to both of UCNCs in aqueous solution and dry form. The emission at 660 nm is inhibited by non-radiative decay process when water interacts with the amine functional group on the surface of nanocubes. In addition, the magnetic susceptibility of the nanocubes is 1.049 × 10⁻⁴ emu g⁻¹ Oe⁻¹ at room temperature, which is 29% larger than the reported value. NIH/3T3 mouse fibroblast cell line was used to study the cytotoxicity of the UCNCs with amine surface modifications. The produced UCNCs with surface modification do not impose toxic effect on cells. The findings could help to better apply upconversion nanocubes in bio-imaging by choosing suitable interfacial media.