Chiral H-aggregation-induced large stokes shift with CPL generation assisted by α-helical poly(L-lysine) substructure

Area of Science:

• Materials Science
• Photochemistry
• Supramolecular Chemistry

Background:

• Fluorescent materials with large Stokes shifts are crucial for advanced optical applications.
• Current methods often rely on complex synthetic design strategies.
• Achieving large Stokes shifts is a key challenge in fluorescent material development.

Purpose of the Study:

• To demonstrate a novel, non-synthetic method for creating fluorescent materials with large Stokes shifts.
• To investigate the role of chiral templates in inducing specific fluorescent properties.
• To explore the potential for generating circularly polarized luminescence.

Main Methods:

• Utilizing α-helical poly(L-lysine) as a chiral template.
• Binding the chiral template to a nonchiral fluorescent dye (NK2751) without chemical modification.
• Analyzing the induced luminescence and Stokes shift under different template conformations (α-helical vs. random coil).

Main Results:

• A large Stokes shift of 230 nm was achieved when the dye interacted with the α-helical poly(L-lysine) template.
• Excimer luminescence and H-aggregated dimer formation were observed, dependent on the template's α-helical structure.
• Minimal Stokes shift (<40 nm) was observed when the template was in a random coil state.
• Successful generation of circularly polarized luminescence was demonstrated.

Conclusions:

• Chiral templates can induce large Stokes shifts in nonchiral fluorescent dyes through specific aggregation states.
• The formation of a chirally twisted H-aggregated dimer state is key to enabling fluorescence despite aggregation-caused quenching.
• This approach offers a new pathway for designing advanced fluorescent materials and circularly polarized luminescence emitters.