Hydrothermal Synthesis of β-NaYF4:Yb, Er Nanocrystals with Upconversion Fluorescence Using Tetraethylene Pentamine as Chelating Ligand

Figure 12

FE-SEM images of NaYF₄:Yb, Er nanocrystals prepared under different rare earth concentration: (a) 8.33 mmol/L; (b) 16.7 mmol/L; (c) 33.3 mmol/L (RE/TEPA = 1 : 1; 𝑡 = 6 h; water/ethanol = 1 : 1).

(a)

(b)

(c)