Preparation of Ultrasmall AIE Nanoparticles with Tunable Molecular Packing via Freeze Assembly

Advances
in the development of aggregation-induced emission luminogens
(AIEgens) depend on understanding how the molecular packing affects
their luminescent properties and on making nanoparticles (NPs) with
desired sizes. Although reported strategies have advanced the field,
rational control of molecular packing and efficient fabrication of
AIEgen NPs sub-5.5 nm in diameter remain pressing issues. Here we
report a “freeze assembly” strategy, in which the diameter
of AIEgen NPs can be precisely tuned from ∼3 nm to hundreds
of nanometers, and a molecular packing in kinetically trapped states
that are not easily captured by conventional assembly methods can
be obtained, leading to tunable fluorescence emissions. Therefore,
this study provides a significant tool to fabricate organic luminescent
nanomaterials with diameters smaller than 5 nm, which is of critical
importance for biomedical applications; meanwhile, tuning molecular
packing in nanoparticles displaying different fluorescence may help
to shed new light on the mechanism of AIEgens.