in diameter were used to enhance upconversion (UC) emission of YF 3: Yb 3+, Er 3+
nanoparticles, respectively. The red or green UC emission of YF 3: Yb 3+, Er 3+
nanoparticles can be selectively enhanced when the red or green UC emission wavelength
overlapped with the photonic bandgaps of opals, which is attributed to Bragg reflection of
photonic bandgap. In addition, when the 980 nm excitation light wavelength was in the …