Fluorescent materials with large Stokes shifts have significant potential for use in optical applications. Typically, a synthetic design strategy is utilized for this purpose. In this study, we demonstrated a novel method by binding a chiral template to a nonchiral fluorescent agent without chemical modification. Specifically, α-helical poly(L-lysine) was employed as the chiral template, which interacted with a disulfonic fluorescent dye, such as NK2751. The dye caused excimer luminescence by inducing the formation of a chirally H-aggregated dimer only when poly(L-lysine) was in an α-helical shape. The result was a Stokes shift of 230 nm. Similar effects were not observed when the chiral template was in a random coil condition and the Stokes shift was less than 40 nm. These findings imply that H-aggregated dimerization, which often results in quenching, permits the electronic transitions necessary for fluorescence events by the formation of the chirally twisted state. In addition, we introduce for the first time the generation of circularly polarized luminescence using the chirality induction phenomena in a dye supported by poly(L-lysine).
Keywords: chiroptical; circularly polarized luminescence; enhanced chirality; induced circular dichroism; poly (amino acid).
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