Responsive photonic crystals (PCs)
with a nanoscale band gap assembled
by colloidal nanospheres have been increasingly utilized in detection
and sensing devices owing to their attractive ability to change color
in response to external conditions. However, most of the reported
works have been dedicated to single-functional PCs, which can only
be used as sensors or detectors in a specific situation. Thus, producing
a multi-functional PC for various industrial applications remains
a challenge. In this work, multi-functional soft PC films (SPCFs)
with a brilliant structural color and a robust structure are fabricated
by using polystyrene@poly(methyl methacrylate-butyl acrylate) [PS@P(MMA-BA)]
nanospheres with size in the range of 200–350 nm as building
blocks. The SPCFs possess both the mechanochromic and solvatochromic
properties owing to the adjustable photonic band gap under stress
and polar solvent conditions. The mechanochromic effect of the SPCF
under stretching results in a blue shift of the structural color due
to the decrease in lattice spacing. In contrast, the solvatochromic
mechanism of the SPCF is that it can be swollen by polar solvents,
resulting in the increase in the lattice spacing of PCs and a red
shift of the structural color. Meanwhile, the SPCF can keep its original
structural color while stretched for 20 cycles or when the organic
solvent is completely evaporated. Therefore, robust multi-functional
SPCFs fabricated by the self-assembly of PS@P(MMA-BA) nanospheres
under gravity sedimentation can respond to stress and organic solvents,
showing great potential for use in sensors and detectors.
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