Liquid crystal displays (LCDs) are widely used for diverse purposes in many aspects in daily life from handle personal devices to professional applications and large-panel LCD televisions. Since LCD is a passive emission display device, it usually shows narrow viewing angle and reduced brightness. Nowadays, LCDs with light-emitting properties is suggested as a less energy consuming displays. To date, fluorescent materials with dichroic properties and strong fluorescence emission are required. However, many molecular emitters, which are highly efficient in solution, will suffer from heavy aggregation-caused quenching (ACQ) effect in the aggregate state, which has greatly limited their applications. In order to overcome these weaknesses, we have designed and synthesized a novel luminescent liquid crystalline compound consisting of a tetraphenylethene (TPE) core, TPE-PPE, as a luminogen with mesogenic moieties. As a result, the TPE-PPE exhibits both the aggregate-induced emission (AIE) and thermotropic liquid crystalline characteristics. By dissolving 1 weight% (wt%) of TPE-PPE into the nematic LC host PA0182, a linearly polarized emission was obtained on the unidirectional orientated LC cell. The photoluminescence polarization ratio of the LC cell has reached to 4.16 between the directions perpendicular and parallel to the rubbing direction. Utilizing the emissive anisotropic TPE-PPE, we have fabricated the photoluminescent liquid crystal display (PL-LCD). This approach has simplified the device design, lowered the energy consumption and increased brightness of the LCD.
Luminescent materials have been widely applied in chemo- and bio-sensing applications because these luminescent materials offer high signal-to-background ratio, superior sensitivity and broad dynamic ranges in various detections. Conventional luminogens suffer from aggregation-caused quenching (ACQ) effect due to strong π–π stacking interaction upon aggregate formation of the luminogens with analytes. Such ACQ effect limits the scope of practical sensing applications. Luminogens with aggregation-induced emission (AIE) characteristics enjoy high emission efficiency in solid or aggregated state while they are non-emissive in solution. AIE luminogens (AIEgens) tackle the lethal problem of ACQ materials in the sensing applications. Siloles and tetraphenylethene (TPE) are archetypal AIE cores and possess advantages of facile synthesis and readily functionalization. AIEgens have been utilized to develop various fluorescent chemosensors. For example, hyperbranched AIE polymers with different topologies can be worked as turn-off explosive sensor with high sensitivity. The explosive detections can be done in solid film, which facilitates practical usage. The AIEgens can also be used as sensors for volatile organic compounds and metal ions through alternating fluorescence on/off mechanisms. Besides chemosensor, the AIEgens have been applied in the fields of biology. Water-soluble AIEgens have been developed for quantifying nucleic acids and proteins. They can serve as bioprobes for real-time monitoring and studying the kinetic of protein conformational changes, making them promising for diagnostic and therapeutic applications. These demonstrations significantly expand the scope of analysis applications of AIEgens and offer new strategies to the design of new fluorescent chemo- and bio-sensors.
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