Enhancing upconversion luminescence of NaYF4:Yb/Er nanocrystals by Mo3+ doping and their application in bioimaging

Abstract

Enhancement of upconversion luminescence is imperative for the applications of upconversion nanocrystals (UCNs). In this work, we investigated the upconversion luminescence enhancement of NaYF₄:Yb/Er by Mo³⁺ ion doping. It was found that the upconversion luminescence intensities of the green and red emissions of UCNs co-doped with 10 mol% Mo³⁺ ions were enhanced by 6 and 8 times, respectively. This enhancement offers a potential increase in the overall detectability of upconversion nanocrystals. HeLa cell imaging using NaYF₄:Yb/Er/Mo as luminescent probes showed bright upconversion fluorescence. Moreover, the Mo³⁺ doping endowed the UCNs with excellent paramagnetic behavior. It is expected that the as-prepared UCNs with a high upconversion luminescence and excellent paramagnetic properties could be promising bi-functional nanoprobes for sensitive multi-modal bioimaging and other optical applications.