SYNTHESIS AND APPLICATION OF UPCONVERSION LUMINESCENT NANOMATERIALS AND 2D MATERIALS

Abstract

Lanthanide doped upconversion nanoparticles (UCNPs) have attracted a lot of interests in recent years due to their unique optical properties. UCNPs can generate short wavelength ultraviolet (UV) or visible luminescence under the excitation of long wavelength near-infrared (NIR) light. So far most of UCNPs are in nanoparticles form and they emit upconversion luminescence under excitation at a single wavelength. In this project, new upconversion luminescent materials including core-shell structured UCNPs with orthogonal luminescent emissions and two dimensional (2D) upconversion materials are developed. For the first stage, new core-shell structured UCNPs with orthogonal luminescent emissions are designed and synthesized. Use of these orthogonal UCNPs (OUCNPs) for real-time imaging and detection of explosive residues from the fingerprint has been explored. For the second stage, 2D bismuth fluoride nanosheets are synthesized in solution at room temperature by using graphene oxide (GO) nanosheets as a template. Unconventional stoichiometry is achieved in the bismuth fluoride nanosheets by adjusting the F/Bi ratio. After that, lanthanide ions are combined with bismuth fluoride nanosheets without the GO template. Various lanthanide ions are in-situ doped in the 2D nanosheets and strong upconversion luminescence is obtained.