Tunable emission from spatially confined luminescent dye blending cholesteric liquid crystals within Au-nanocages

Liquid crystals (LCs) have been widely employed in laser applications, with their performance often enhanced through the incorporation of nanomaterials. In this study, we investigated cholesteric liquid crystals (CLCs) exhibiting a UV-tunable photonic bandgap (PBG), and demonstrated a notable enhancement in the emission of the embedded luminescent dye (4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM)) by progressively red-shifting the PBG. When confined within hollow nanocages, the CLCs exhibited a substantial nano-confinement effect, particularly under UV irradiation. Accordingly, Au-nanocages (Au-NCs) were incorporated into the CLCs. The resulting hybrids exhibited the PBG characteristics of the pristine CLCs, while displaying a substantially broadened reflection diagram and an accelerated rate of PBG shifting. Moreover, the gold-nanocages (Au-NCs) blending CLCs-hosts required significantly lower pumping energy to excite the DCM dye compared to pure CLCs. It also enabled an augmentation of the tunable emission intensity subjected to PBG modulation. With the incorporation of 0.10 wt.% Au-NCs, the threshold pumping energy of DCM in such hybrid was reduced to 0.432 µJ/pulse, corresponding to a 4.63% decrease, while the tunable range of emission intensity was expanded by 16.02%. Additionally, the DCM emission demonstrated improved long-term stability over an eight-week period, thereby substantiating the viability of such hybrids for the fabrication of high-performance LC-lasers.