(a) Scheme showing the synthesis and functionalization of UCNP@Fe-MIL-101_NH2 nanostructures. (b) TEM image of UMPs nanoparticles with core-shell structure. (c) Upconversion emission spectra of UMP nanostructures. Inset is the photo of UMPs nanostructures dispersed in water under 980 nm diode excitation. (d) Relaxation rate R2 (1/T2) versus molar concentrations of UMPs nanostructures at room temperature using a 3T MRI scanner (Inset: T2-weighted MR images of UMPs with varied concentrations). Representative upconversion luminescence (e,f) and T2-MRI images (g,h) of subcutaneous KB tumor-bearing mice (tumor diameter: 8–10 mm) and dissected organs of the mice sacrificed 24 h after intravenous injection of UMP-FAs (targeted, e,g) and UMPs (non-targeted, f,h). 1, heart; 2, kidney; 3, lung; 4, liver; 5, spleen; 6, KB tumor. (i) Biodistribution of nanostructures in organs of the tumor-bearing mice 24h after intravenous injection of particles. (j) Biodistribution of intravenously injected UMPs nanostructures in different organs of mice at 0.5 h, 12 h, 24 h, 7 d, and 30 d. Reproduced with permission.[158] Copyright 2015, Wiley-VCH.