Figure 6.

(a) Schematic illustration of spectral overlap of the absorption (red) of the BFO shell and emission (blue) of the upconverting core. (b) Energy level diagrams of Yb³⁺ and Er³⁺ ions, as well as the upconverting luminescence process upon NIR excitation; the energy transfer from upconverting core to BFO shell. (c) SPR enhanced the photoactivity of Ag@SiO₂@UC@BFO-Au under VIS and NIR excitation. (d) Schematic process of the AAS photo-polymerization using Ag@SiO₂@UC@BFO-Au as a photoinitiator [31].