Abstract:
Recently, Minghua Liu, Guanghui Ouyang, and colleagues from the Institute of Chemistry, Chinese Academy of Sciences, reported a novel strategy to significantly enhance circularly polarized luminescence (CPL): by employing a cooperative noncovalent–covalent approach, they covalently anchored anthraquinone chromophores into a preorganized chiral liquid crystal (CLC) network. This strategy achieved a high luminescence dissymmetry factor (glum) of up to 1.73. Furthermore, taking advantage of the material’s outstanding photochromic and enhanced CPL properties, they demonstrated its application in photo-patterning and Morse code-based multi-level information encryption. This work provides a new pathway for developing high-glum CPL liquid crystal materials and exploring their functional applications.
Background:
Circularly polarized luminescence (CPL), a chiroptical emission phenomenon, has attracted growing attention due to its potential applications in 3D displays, optoelectronics, quantum computing, and bioimaging. Ideal CPL materials require not only high quantum yields and tunable emission wavelengths, but also large luminescence dissymmetry factors (glum), with a theoretical maximum absolute value of 2.0. However, most current CPL-active materials based on organic molecules, polymers, or coordination compounds exhibit glum values typically in the range of 10⁻⁴ to 10⁻¹, which falls short of practical requirements. Thus, developing new design strategies for chiral materials with enhanced CPL is a key challenge in the field.
Highlights:
Unlike conventional methods that enhance glum via noncovalent doping of luminophores into chiral liquid crystals, this work introduces a cooperative noncovalent–covalent strategy. Anthraquinone (AQ) chromophores were first noncovalently pre-doped into the commercial SLC1717 liquid crystal matrix. Under UV irradiation, they undergo a topochemical radical-mediated addition reaction with the diarylacetylene components of the matrix, resulting in covalent anchoring of green-emitting luminophores embedded within the liquid crystal network. This single-layer CLC structure produced significantly enhanced CPL with a glum value as high as 1.73.
As a proof of concept, the researchers leveraged the photochromic properties and high CPL of the system to design a multi-level Morse code encryption scheme, which could only be decrypted using circular polarization filters with matched chirality. This offers an innovative design for CPL-based information encryption applications.
Conclusion and Outlook:
In summary, this study presents a novel strategy for generating CPL in liquid crystals via in situ formation of emissive species through noncovalent doping and subsequent topochemical covalent anchoring. The approach relies on the synergistic effect of anthraquinone chromophore pre-doping and UV-induced covalent bonding to the liquid crystal’s diarylacetylene units. Spectroscopic, EPR, and MS analyses confirmed the formation of green-emitting luminophores via radical-mediated reactions, which retain ordered alignment within the CLC helical structure and emit nearly pure circularly polarized light.
The remarkable photochromic and CPL properties of this system enabled successful implementation of photo-patterning and Morse code encryption. Although CPL-active cholesteric liquid crystals have previously been conceptually used in encrypted devices, this work innovatively proposes a “photo-triggered emission → CPL encoding → circular polarizer decoding” concept, demonstrating strong potential for multi-level information encryption. This covalent anchoring strategy can be extended to other liquid crystal or polymer systems containing diarylacetylene units, offering a new direction for high-performance CPL materials and encryption technologies.
Article Details:
A Cooperative Noncovalent-Covalent Strategy for Amplified Circularly Polarized Luminescence and Multiple Information Encryption within Chiral Liquid Crystals
Jingxiao Ren†, Lukang Ji†, Chengyu Jiang, Pengfei Duan, Guanghui Ouyang*, and Minghua Liu*
Cite this by DOI: 10.31635/ccschem.025.202505596
Article link: https://doi.org/10.31635/ccschem.025.202505596