Microcapsules having of a fluidic photon upconverting UC core and photonic shell were microfluidically prepared using a triple emulsion as the template. The photonic shell consisted of a cholesteric liquid crystals (CLC) with a periodic helical structure, which exhibited a photonic band gap. The shell has planar anchoring at the boundaries and serves as a resonance cavity for tiplet-triplet annihilation photon upconversion (TTA-UC). The dimensions and composition of the layers can be varied for spectral tuning of the UC under low-power-density excitation. The results suggest a range of opportunities provided by these systems for the design of low-threshold photonic devices.
From J. Am. Chem. Soc. 2017, 139, 5708: Amplified Photon Upconversion by Photonic Shell of Cholesteric Liquid Crystals