| [Visitor (112.0.*.*)]answers [Chinese ] | Time :2023-04-28 | The development of organic systems with circularly polarized luminescence (CPL) is becoming increasingly important in various fields including stereo optical information storage and processing, optical identification sensors, quantum computing, and circularly polarized electroluminescence for 3D displays. The CPL response of molecular systems is usually quantified with asymmetric factors (GLUMs). Here, glum=2(IL-IR)/(IL IR), where IL and IR represent the emission intensity of left-circularly polarized luminescence and right circular-polarized luminescence, respectively.
The general strategy for implementing CPL is to build molecules with specific chiral configurations characterized by fluorescence, delayed fluorescence, or phosphorescent optical properties. However, materials with CPL properties depend not only on the function of the molecule itself, but also on macroscopic properties of molecular assembly through multi-level structures.
Multi-level self-assembly is ubiquitous in nature and is one of the most complex bottom-up approaches for organisms to build ideal structures using molecular building blocks. Systems with structural integrity derived from multi-stage self-assembly are much superior to non-multi-stage self-assembly systems. Multi-stage self-assembly systems exhibit greater stability to environmental changes such as pH, temperature, and pressure, and greater resistance to external stimuli such as mechanical, electrical, or magnetic forces. Due to these advantages, multi-stage self-assembly strategies have been widely used to complete the construction of nanoscale and microscale functional materials for applications ranging from optoelectronic materials to biomedicine.
Through multi-stage self-assembly methods, nanostructured chiral materials can transfer and amplify molecular functions to macro-scale CPL properties at specific scales. Therefore, studying the multi-level structure of molecular assembly and the corresponding CPL properties is an important issue for the development and realization of effective CPL materials.
Typically, fluorescence normalized asymmetric factors (GLUMs) in organic systems are between 10-4 and 10-2. In rare cases, polyfluorene films or cholesterol organic systems have extremely high GLUM values with values greater than 0.2 or even as high as 1. The spiral axis of the system is perpendicular to the direction of the substrate. In cholester-type films, the strong CPL response can come from the sum of two main contributions, including the intrinsic chiral supramolecular structure and birefringence pattern (Bragg reflection).However, these doped cholesterol systems often experience incompatibility and instability issues. Therefore, the search for strong chiral optical signals from pure organic compounds remains challenging. Previous studies have reported a galum of 0.29 in chiral bishiophene-benzene copolymer films in the chiral nematic annealing state and a high glolum of -0.23 in chiral disubstituted polyacetylene without chiral dopants...
Recently, chiral molecular assemblies with aggregation-induced luminescence (AIE) have received attention. Benefiting from the enhanced emission intensity when AIEGEN is aggregated, these assemblies can produce an efficient CPL response in the solid state, allowing them to obtain high-performance CPL characteristics at the macro scale. Although significant progress has been made in obtaining efficient circularly polarized emission, it is difficult to establish a link between controlling the mesoscopic structure and its corresponding CPL characteristics.
Therefore, there is a great need for AIEGEN, which exhibits CPL properties in condensed matter or solid state. |
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