Silica Nanoparticle Coating of NaYF₄:(Yb³⁺, Er³⁺) Upconversion Phosphor

Figure 3

SEM images of NaYF₄:(Yb³⁺, Er³⁺) phosphors coated with nanoparticles at several colloidal silica concentrations and noncoated phosphor ((a) noncoated 0 wt%, (b) 0.3 wt%, (c) 1.4 wt%, (d) 2.7 wt%, and (e) 5.0 wt%). The dotted circles represent nanoparticles coated on the surface of NaYF₄:(Yb³⁺, Er³⁺) microphosphors.

(a)

(b)

(c)

(d)

(e)