Fig. 1
Characterizations of NaGdF4:5%Nd@NaLuF4 NPs. a Schematic illustration of Nd-RENP fabrication. b TEM image of NaGdF4:5%Nd cores (scale bar, 100 nm). c TEM image of NaGdF4:5%Nd@NaLuF4 core–shell NPs (scale bar, 100 nm). d Diameter distribution of core and core–shell RENPs. e Downconversion photoluminescence spectra of core RENPs (NaGdF4:5%Nd) and core–shell RENPs (NaGdF4:5%Nd@NaLuF4) under 808 nm excitation laser. f The fluorescence image of H2O, core, and core–shell RENPs was obtained using an 808 nm excitation laser. The fluorescence signals were collected via a 1000 nm long-pass filter. g Fluorescence emission spectra of OA-modified Nd-RENPs and PEGylated Nd-RENPs under 808 nm laser