21
C U R I O S I T Y - D R I V E N
R E S E A R C H @ H K U S
Potential Applications of AIE Materials
Smart material
Wave-guide
Bacterial imaging
Liquid crystal
Cell tracker
Forensic sensor
OLED
Cell imaging
Chemosensor
Circularly polarized
luminescence
Vascular imaging
Biosensor
Traditional light-emitting materials often emit weak or no light in concentrated solutions or in a solid
state. This is known as “aggregation-caused quenching” (ACQ) (Figure a).
In 2001, Prof Tang and his team discovered abnormal emission behavior in some molecules, where
aggregation played a constructive instead of a destructive role. A series of silole derivatives while non-
emissive in dilute solutions were found to be highly luminescent when aggregated or cast into solid
films (Figure b).
Since light emission is induced by aggregate formation, the process was named “aggregation-induced
emission” (AIE), which is the exact opposite of ACQ.
b
in Hong Kong will be headed by Prof Tang
and will concentrate on new luminescent
materials and their hi-tech applications in
biomedical sensors and chemical probes.
Such work could benefit numerous fields,
including detection, imaging, quarantine,
inspection, diagnosis, environmental
protection and homeland security. The
Center will also encourage academic,
research and development, and industry
collaboration.
Earlier, in 2012, the Ministry of
Science and Technology of China
incorporated AIE into its National Basic
Research Program – also known as the
973 Program – and awarded Prof Tang a
RMB30million(US$4.6million) grant for
further development of AIE. In addition,
Prof Tang and his AIE research have been
the subject of high-profile overseas media
reports, including a recent feature in
The
New York Times
, an interview by CNBC
and a news feature article in
Nature
.
Previously, aggregation was seen as
detrimental to light emission because
most light-emitting molecules dimmed
in their solid form/condensed state, a
phenomenon known as “aggregation-
caused quenching” (ACQ).
Through experiments, Prof Tang’s
team discovered that the intriguing
mechanism behind the AIE phenomenon
lies in the shape of the molecule. Most
light-emittingmolecules are flat and stack
together when crowded, which extin-
guishes their luminescence. In contrast,
AIE-gens are often propeller shaped, so
they lock together when crowded and are
forced to release their energy as photons.
“This was conceptually new,” Prof
Tang explained. “Once you have a new
concept, you can build a platform for
future development.” Scientists across
the world responded. Numerous papers
have been published independently or
in partnership with the HKUST chemists
and, in 2013, AIE was among the top 100
research topics, according to Thomson
Reuters.
“The promise of AIE materials is
extensive. They can help improve our
practical capabilities in many different
fields. These benefits for society are what
make such research so worthwhile to
pursue,” Prof Tang said.
a
