THESIS
2015
iv leaves, v-xxxii, 207 pages : illustrations (some color) ; 30 cm
Abstract
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...[
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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.
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