Stepwise Solution-Interfacial Nanoarchitectonics for Assembled Film with Full-Color and White-Light Circularly Polarized Luminescence

The fabrication of chiral thin films with tunable circularly
polarized
luminescence (CPL) colors is important in developing chiroptical materials
but remains challenging due to the lack of assembly-initiated chiral
film formation methodology. Here, by adopting a combined solution
aggregation and interfacial assembly strategy, we report the fabrication
of chiral film materials with full-color and white-light CPL. A biquinoline
glutamic acid ester (abbreviated as BQGE) shows a typical aggregation-induced
emission property with blue CPL after solution aggregation. Subsequent
interfacial assembly of these solution aggregates on a solid substrate
leads to the formation of a CPL active film consisting of nanobelt
structures. Since the BQGE molecule has a coordination site, the CPL
emission of an individual BQGE film can be extended from blue to green
emission upon coordination with a zinc ion, accompanied by morphology
transition from nanobelts to nanofibers. Further extension to red-color
CPL is successfully achieved by coassembly with an achiral acceptor
dye. Interestingly, the proper combination of coordination ratio and
acceptor loading ratio provides bright white-light CPL emission from
the BQGE/Zn2+/PDA triad composite film. This work provides
a new approach to fabricating chiroptical film materials with controlled
microscopic morphology and tunable CPL properties.