Seeded Growth of Three-Dimensional Block Heterojunctions Featuring Photoinduced Emission Enhancement

Three-dimensional (3D) block heterojunctions composed
of different
individual blocks may bring forth emergent properties beyond those
of one-dimensional and two-dimensional block heterojunctions. However,
the strategies to construct 3D block heterojunctions are still lack.
Here, we report a living self-assembly of size-controlled 3D block
heterojunctions that show remarkable photoinduced emission enhancement.
A carefully designed near-infrared (NIR) donor–acceptor (D–A)
molecule is assembled into a unique 3D architecture as a heteroseed.
The NIR D–A molecules in this seed are circularly interconnected
with 1-propanol through hydrogen bonding to create string-like building
blocks, which are then packed laterally through electrostatic attraction
and weak π-interactions into a 3D structure. The unique heteroseed
can guide the continuous growth of another D–A molecule in
the same manner to create a 3D block heterojunction with a nonphotostable
outer block. Under ultraviolet irradiation, the intermolecular rearrangement
of another D–A molecule can occur within the outer block, leading
to an interfacial phase separation from the core block. The separation
disrupts the efficient energy transfer from the outer block to the
heteroseed core, thereby significantly enhancing the emission of the
outer block. The utilization of heteroseed-guided self-assembly in
the construction of photoresponsive 3D block heterojunctions represents
a novel strategy for the advancement of photoresponsive functional
materials.