Perovskite nanocrystals with high chirality and stability were synthesized via chirality transfer from a chiral supramolecular nanoreactor assembled from an achiral block copolymer complexed with racemic alanine.
Chiral metal oxide nanostructures have received tremendous
attention
in nanotechnological applications owing to their intriguing chiroptical
and magnetic properties. Current synthetic methods mostly rely on
the use of amino acids or peptides as chiral inducers. Here, we report
a general approach to fabricate chiral metal oxide nanostructures
with tunable magneto-chiral effects, using block copolymer (BCP) inverse
micelle and R/S-mandelic acid (MA). Diverse chiral
metal oxide nanostructures are prepared by the selective incorporation
of precursors within micellar cores followed by the oxidation process,
exhibiting intense chiroptical properties with a g-factor up to 7.0
× 10–3 in the visible–NIR range for
the Cr2O3 nanoparticle multilayer. The BCP inverse
micelle is found to inhibit the racemization of MA, allowing MA to
act as a chiral dopant that imparts chirality to nanostructures via hierarchical chirality transfer. Notably, for paramagnetic
nanostructures, magneto-chiroptical modulation is realized by regulating
the direction of the external magnetic field. This BCP-driven approach
can be extended to the mass production of chiral nanostructures with
tunable architectures and optical activities, which may provide insights
into the development of chiroptical functional materials.
The
chirality of nanostructured systems has gained growing attention
in catalysis, biotechnology, and optoelectronics owing to their exotic
enantio-/spin-selective interactions and intriguing chiroptical features.
However, large-scale fabrication of chiral inorganic nanostructures
still remains a challenge. Herein, we report a simple but generalized
route for the synthesis of diverse chiral inorganic nanoparticles
(NPs) such as Au, Ag, PdO, and TiO2 NPs using block copolymer
(BCP) templates. The self-assembled BCP inverse micelles offered a
specific environment, wherein dl-alanine induced left-handedness
via hydrogen bonding with the pyridines of polystyrene-block-poly(4-vinyl pyridine), for the evolution of chirality. The BCPs
were then used as a chiral host to transfer their handedness to the
anchored inorganic NPs, resulting in an anisotropy factor of −8.6
× 10–4 for the BCP/Au NP hybrid. Our design
concept pinpoints the steps required to construct an extended library
of viable chiral nanostructures and will aid in the development of
artificial chiral materials.
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