Upconversion Emission Enhancement of NaYF₄:Yb,Er Nanoparticles by Coupling Silver Nanoparticle Plasmons and Photonic Crystal Effects

Metal nanoparticle plasmons or the photonic crystal effect are being widely used to modify luminescence properties of materials. However, coupling of surface plasmons with photonic crystals are seldom reported for enhancing luminescence of materials. In this paper, a new method for upconversion emission enhancement of rare-earth doped nanoparticles is reported, attributed to the coupling of surface plasmons with photonic band gap effects. Opal/Ag hybrid substrates were prepared by depositing Ag nanoparticles on the top layer of opals by magnetron sputtering. The selective enhancement of red or green upconversion emission of NaYF₄:Yb³⁺,Er³⁺ nanoparticles on the opal/Ag hybrid substrates is attributed to the coupling effect of surface plasmons and Bragg reflection of the photonic band gap. In addition, the upconversion emission enhancement of NaYF₄:Yb³⁺,Er³⁺ nanoparticles on the opal/Ag hybrid substrate is attributed to the excitation enhancement was obtained when the excitation light wavelengths overlap with the photonic band gaps of opal/Ag hybrid substrates. We believe that these enhancement effects based on the coupling of metal nanoparticles with the photonic band gap could be extended to other light-emitting materials, which may result in a new generation of lighting devices