Constructing high performance circularly polarized luminescence materials by regulating the chiral physical environment of chromophores

Circularly polarized luminescence (CPL) materials, due to their special chiral luminescence properties, have attracted widespread attention in information encryption, asymmetric catalysis, optoelectronic devices, and biosensing. Traditional methods for preparing CPL materials often require complex and tedious synthesis processes. Besides, it is difficult to enhance the luminescence dissymmetry factor (g(lum)) and meet practical applications. Constructing CPL materials by modulating the chiral physical environment of chromophores has the advantages of simple preparation and strong applicability, compatible with various chiral or achiral chromophores, and generally having large luminescence dissymmetry factor, providing the possibility of practical applications of CPL materials. Self-assembly, a bottom-up construction method, is a common strategy to change the chiral physical environment of chromophores. Chiral self-assembly refers to the phenomenon where assembly elements accumulate into asymmetric structures through one or more non-covalent interactions. There are three possible situations: (1) The chiral chromophore can form a chiral structure through self-assembly, and significantly enlarge CD and CPL; (2) for the achiral chromophore, it can generally assemble with other chiral materials to form a chiral assembly structure by asymmetric stacking arrangement and obtain CPL performance; (3) the completely achiral chromophore can also generate chirality and CPL performance by symmetry breaking during assembly. The non-covalent interactions usually have strong modularity and dynamic modulation of performance can be achieved through reasonable design, which is suitable for constructing the intelligent responsive CPL materials. Besides, thanks to the development of nanofabrication technology, the artificial metasurface, a top-down construction method, has also become a new method to construct efficient CPL materials by changing the chiral physical environment of chromophores. There are two mechanisms for CPL in metasurfaces: Firstly, the chiral electromagnetic field generated by the metasurfaces can change the spin state of emitted light, leading to spontaneous circularly polarized light emission; the second is that chiral metasurfaces can selectively absorb or reflect circularly polarized light of a certain chirality, thereby enhancing circularly polarized luminescence of another chirality. Artificial metasurfaces are typically composed of one or more layers of artificially designed nanostructures so the thickness of metasurfaces is always small. What's more, it also has advantages in controlling material structures. Thanks to these advantages, CPL materials modulated by the chiral physical environment of chromophores have a lot of applications. However, there are still some problems in this kind of material, for example, the low g(lum) factor in self-assembly and there is only a small number of examples of CPL metasurfaces. In this review, based on the construction strategy of CPL materials modulated by the chiral physical environment of chromophores, we introduce the relevant concepts of CPL, summarize the research progress of constructing high-performance CPL materials by self-assembly and metasurfaces, and the application of CPL materials in information encryption, biosensing, and asymmetric photopolymerization, and propose the current problems and the prospect.