Figure 6.

(A) Luminescence spectrum of the UCNPs excited at 980 nm and TEM image of the UCNPs. (B) Cell imaging using UCNPs (top left) brightfield image of a cell with internalized UCNPs, (top middle) fluorescence imaging of stained cell with UCNPs excited at 980 nm, and (top right) merged. (Bottom left) brightfield image of a cell without UCNPs, (bottom middle) fluorescence imaging of cell without UCNPs, and (bottom right) cellular autofluorescence excited at 532 nm. (A, B) Reproduced from Wu S, Han G, Milliron DJ, et al. Non-blinking and photostable upconverted luminescence from single lanthanide-doped nanocrystals. Proc Natl Acad Sci. 2009;106(27):10917–10921.¹⁵³ (C) The fluorescent microscopy images from the trapped droplets by microfluidic array involving: iI) droplets with lanthanide-doped NPs, ii) droplets with GFP-expressing cell, iii) droplets with co-encapsulated NPs and GFP-expressing cell, and iv) empty droplets. Reprinted by permission from Springer Nature: Anal Bioanal Chem, Luminescent nanomaterials for droplet tracking in a microflui- dic trapping array, Vaithiyanathan M, R Bajgiran K, Darapaneni P, Safa N, Dorman JA, Melvin AT, Copyright 2019, doi:10.1007/s00216-018-1448-1.¹⁵⁴