Fluorescence is of crucial importance in a variety of studies, ranging from organic light-emitting diode (OLED) for display and lighting, chemosensors for poisonous ions and explosive detection, bioprobes for macro and small biomolecules tracing and contrast reagents for in vitro and in vivo imaging. Application of these materials usually takes place in aqueous solution or solid state. Incongruously, however, most fluorophores are constructed from π-conjugated hydrophobic and are inclined to form aggregates in water. Emission for these molecules can be quenched through formation of excimer or exciplex, a phenomenon notoriously known as aggregation-caused quenching.

Recently, a completely different phenomenon is observed on a species of propeller-shaped molecules, such as hexa...[ Read more ]

Fluorescence is of crucial importance in a variety of studies, ranging from organic light-emitting diode (OLED) for display and lighting, chemosensors for poisonous ions and explosive detection, bioprobes for macro and small biomolecules tracing and contrast reagents for in vitro and in vivo imaging. Application of these materials usually takes place in aqueous solution or solid state. Incongruously, however, most fluorophores are constructed from π-conjugated hydrophobic and are inclined to form aggregates in water. Emission for these molecules can be quenched through formation of excimer or exciplex, a phenomenon notoriously known as aggregation-caused quenching.

Recently, a completely different phenomenon is observed on a species of propeller-shaped molecules, such as hexaphenylsilole and tetraphenylethene. They are non-emissive in the solution state but are highly emissive in the aggregated state. The phenomenon is termed as aggregation-induced emission (AIE).

Systematic studies have shown restriction of intramolecular motion is the main cause for the AIE phenomenon. In this work, I will present our recent studies on the substituent effect of the silole ring. Our results show that substituents at different positions affect silole emission profile in significant manner but in different way.

AIE luminogens (AIEgens) enjoy the advantages of high brightness, low background emission, excellent photostability and good biocompatibility and are thus applied to bacterial studies. AIEgens with different functionalities are applied to differentiate live and dead bacteria, high-throughput screening of antibiotics and fast evaluation of bacterial susceptibility, respectively.

I discovered that some AIEgens can promote the generation of reactive oxygen species under light illumination and then applied them to photodynamic killing of bacteria and cancer cell, respectively. In the aggregated state, AIEgens demonstrates higher efficiency in ROS generation than in the solution. Besides, AIEgens are very photostable, which ensures the efficient killing of bacteria and cancer cells.

We discovered the fluorescence property of poly(maleic anhydride-alt-vinyl acetate) (PMV), a pure oxygen-containing non-conjugated polymer. The origin of its emission was proved to be associated with conformational lockage of the anhydride group. Interestingly, after interacting with nitrogen-rich solvent, the polymer demonstrates longer wavelength absorption and emission. In this way, we can tune the emission wavelength and efficiency by varying the solvent, without the need of changing the chromophore.