Near-Infrared Upconversion Luminescence and Bioimaging In Vivo Based on Quantum Dots

Abstract

Recently, upconversion luminescence (UCL) has been widely applied in bioimaging due to its low autofluorescence and high contrast. However, a relatively high power density is still needed in conventional UCL bioimaging. In the present study, an ultralow power density light, as low as 0.06 mW cm −2 , is applied as an excitation source for UCL bioimaging with PbS/CdS/ZnS quantum dots (UCL-QDs) as probes. The speculated UCL mechanism is a phonon-assisted single-photon process, and the relative quantum yield is up to 4.6%. As determined by continuous irradiation with a 980 nm laser, the UCL-QDs show excellent photostability. Furthermore, UCL-QDs-based probe is applied in tumor, blood vessel, and lymph node bioimaging excited with an eye-safe low-power light-emitting diode light in a nude mouse with few heat effects.