Carbon dots (CDs) possess outstanding luminescence properties, leading
to their use in a wide range of applications including optical displays,
anti-counterfeiting systems, bioimaging and sensors. Presently, there is
much debate about the classification of CDs, as well as their formation
process, structure and fluorescence mechanisms. Aggregation plays an
important role in both the formation of CDs and their fluorescence (e.g.
aggregation-induced emission), yet is seldom studied in detail. This
review aims fill this knowledge gap, by firstly exploring how
aggregation leads to the formation of different types of CDs (e.g.
graphene quantum dots, carbon quantum dots, and carbonized polymer
dots), followed by a detailed examination of the effect of
aggregation-induced morphology on the luminescence properties and
application of CDs. Finally, opportunities and challenges for the
application of CDs in various applications are discussed, with the need
for better mechanistic understanding of aggregation-induced luminescence
being an imperative.