Visible Discrimination of Broadband Infrared Light by Dye-Enhanced Upconversion in Lanthanide-Doped Nanocrystals

Figure 5

TEM image NaYF₄:Yb³⁺, Tm³⁺ nanoparticles with nominal 12 nm thick silica shell ((a); scale bar is 50 nm). TEM image NaYF₄:Yb³⁺, Ho³⁺ nanoparticles with a thinner silica shell estimated to be 2 nm or less ((b); scale bar is 20 nm). In both cases, the silica shell includes the attached infrared dye, which is not discernible in the TEM image.

(a)

(b)