(Copyright 2015, 2012 and 2015. American Chemical Society. Reproduced with permission.)
a Schematic illustration of the hydrothermal preparation synthetic procedure of UCNPs@TiO2 NCs . b TEM images of the original NaYF4:Yb3+,Tm3+ cores (scale bar = 50 nm). c Sol–gel method for synthesized 2-aminoethyl dihydrogen phosphate-stabilized NaYF4:Yb3+,Er3+ nanoparticles (scale bar: 100 nm) . d UPP@ovalbumin were prepared by microemulsion synthesis .