THESIS
2013
xxii, 132 pages : illustrations (some color) ; 30 cm
Abstract
Circularly polarized luminescence (CPL), the emission analogue to circular dichroism
(CD), reflects the chirality of materials in the excited electronic state. CPL active materials
with efficient performances are essentially suitable as emitters for optoelectronic devices for
stereoscopic optical processing, display and storage, and sensors for chiral recognition in
pharmaceutical industries and biological systems. However, compared to standard
photoluminescence spectroscopy, CPL spectroscopy is less studied. Typically, CPL is
generated when a luminophore experiences in a dissymmetric environment in the excited state
and thus inevitably requires helical arrangement of the luminophoric molecules. The ordered
assembly of the luminogens, however, results in reduced emission efficie...[
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Circularly polarized luminescence (CPL), the emission analogue to circular dichroism
(CD), reflects the chirality of materials in the excited electronic state. CPL active materials
with efficient performances are essentially suitable as emitters for optoelectronic devices for
stereoscopic optical processing, display and storage, and sensors for chiral recognition in
pharmaceutical industries and biological systems. However, compared to standard
photoluminescence spectroscopy, CPL spectroscopy is less studied. Typically, CPL is
generated when a luminophore experiences in a dissymmetric environment in the excited state
and thus inevitably requires helical arrangement of the luminophoric molecules. The ordered
assembly of the luminogens, however, results in reduced emission efficiency owing to the notorious aggregation-caused quenching (ACQ) effect suffered by most conventional
chromophores. Therefore, overcoming the ACQ effect is a key step towards the design and
fabrication of efficient CPL emitters.
An excellent phenomenon opposite to ACQ was discovered in 2001 by our group: a series
of nonluminescent molecules are induced to emit efficiently by aggregate formation
[aggregation-induced emission (AIE)]. It is envisaged that AIE luminogens can possess
improved CPL performance. Attracted by the intriguing phenomenon and its fascinating
perspectives, I have launched a new program directed towards the development of new AIE
materials with circularly polarized luminescence (CPL).
In order to induce the helical arrangement of the AIE luminogens, chiral peripheral groups
including sugar and amino acid are used to functionalize the silole core. The resultant
molecules are capable of self-assembling into helical structures which have high fluorescent
quantum efficiency and remarkable CPL signals. Interestingly, different fabrication methods
leading to different morphologies can change the preference of either left- or right-handed
circular signals. One of the examples also shows that the preference can be tuned through the
addition of enantio-pure mendalic acids.
In addition, facile oxidative coupling reactions are employed to construct new type of AIE
luminogens with different functionalities.
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