Photoluminescence modulation in the graphene oxide dispersed 4-n-octyl-4’-cyanobiphenyl molecular system

Abstract

Herein, we investigate the mechanism of photoluminescence modulation (PLM) in the 4-n-octyl-4’-cyanobiphenyl liquid crystal (8CB LC) in the presence of various doping concentrations (0.02 to 0.4 wt%) of 2D-GO (two-dimensional graphene oxide) nanoflakes. The role of intermolecular interactions on PLM and the subsequent effect on the decay lifetime is also examined via time-resolved PL measurements. The presence of intermolecular interactions is additionally confirmed by means of differential scanning calorimetry and polarized optical microscopy. The successive addition of GO nanoflakes sharpens the absorption band of pure 8CB LC; consequently, it is blue shifted. The PL properties of the 8CB LC enhance due to the addition of GO nanoflakes which might be attributed to electron–phonon interaction between 8CB molecules and GO nanoflakes. The PL enhancement has been further supported by the time-resolved PL decay time measurement. The longest and shortest fluorescence lifetimes have been recorded for the 0.1 and 0.4 wt% GO/8CB composites, respectively. The investigated composites have shown their potential applications for fluorescent optical devices; however, the quantum efficiency needs to be further improved.