Chirality, as a universal asymmetric feature in our world, exists from the microscopic single molecules, to mesoscopic assemblies such as DNA and proteins, and finally macroscopic tissues and our hands. Ever since the discovery of chirality in the 19^th century, the generation and utilization of chirality are always popular topics due to the desire of exploring the mysteries of nature. To emphasize the significance of chirality, the Nobel Prize in Chemistry in 2001 was awarded for asymmetric catalysis. With the development of modern technology, chiral materials have been exploited into biological, optical, and electronic application fields.

Amongst all the manifestation aspects of chirality, circularly polarized luminescence (CPL) is one of the most alluring features that convert...[ Read more ]

Chirality, as a universal asymmetric feature in our world, exists from the microscopic single molecules, to mesoscopic assemblies such as DNA and proteins, and finally macroscopic tissues and our hands. Ever since the discovery of chirality in the 19^th century, the generation and utilization of chirality are always popular topics due to the desire of exploring the mysteries of nature. To emphasize the significance of chirality, the Nobel Prize in Chemistry in 2001 was awarded for asymmetric catalysis. With the development of modern technology, chiral materials have been exploited into biological, optical, and electronic application fields.

Amongst all the manifestation aspects of chirality, circularly polarized luminescence (CPL) is one of the most alluring features that converts such an invisible characteristic into observable light emission. As a result, pursuing highly emissive CPL systems has become a general target of developing novel chiral materials. These obtained CPL-emitting materials have been successfully applied into biological sensors and display devices. However, conventional luminogens, including a series of chiral luminogens, often suffer from the phenomenon that exhibits strong emission in solution state but weakened or even annihilated emission in aggregate state, which is defined as aggregation-caused quenching (ACQ) effect. This effect restricts the performance of chiral luminophores in condensed state for application, resulting in poor CPL performance in practical devices. The creation of AIE luminogens (AIEgens) could prevent the emitters from ACQ phenomenon due to their opposite photophysical properties of weak or no emission in solution state but enhanced emission once the aggregates formed. Combining the merits of AIE and CPL, several projects about constructing novel emitting materials were carried out in this thesis work.

Firstly, concerning about the mechanism of supramolecular chirality formation, we have developed a chiral AIEgen undergoing spontaneous hierarchical self-assembly in aggregate state from vesicles to helical fibers, which can be monitored by in situ and real-time CD spectra. CPL signals were further induced by co-assembly of the complexes as chiral templates and achiral luminogens.

Then, inspired by muscular filament sliding in human bodies, muscle-like molecular motion was found to switch on the CPL emission in a synthesized chiral Au(I) complex. The pristine powder of both enantiomers was non-emissive, whereas the emission could be triggered by scratching force. Structural studies revealed no crystal phase change occurred but only subtle solid-state molecular motion that turned on the CPL emission.

After that, aiming for novel approach to chirality, a simple CPL-emitting device was fabricated by achiral twisted nematic liquid crystals (TN-LC) doped with achiral AIEgens. Relatively high-performance CPL emissions from blue to red with luminescence dissymmetry factor (glum) up to 10^-2 were obtained from those devices without chiral components.

At last, in order to improve the chiral behavior, another chiral AIEgen encountering aggregation-annihilated circular dichroism (AACD) effect was converted into CPL-emitting material by doping in liquid crystals (LCs). Additional achiral AIEgens were further added to the obtained chiral nematic liquid crystal (N*-LC) to gain amplified CPL emission.