Fig. 2. PL spectra (a) and ML spectra (b) of p-P₄Ac, p-P₄A and p-FP₂A; (c) ML images of p-P₄A: (I) performed in dark, (II) capital letters ‘AITL’ displayed using ML in the dark; (III) performed under daylight. The PL spectra were recorded under excitation of 365 nm UV light.