posted on 2018-11-06, 00:00authored byDonghui Kou, Wei Ma, Shufen Zhang, Jodie L. Lutkenhaus, Bingtao Tang
Colorimetric
sensors, as a key branch of the application of photonic crystals (PCs),
brings enthusiasm to scientists to do research. Here, simple mesoporous
and structurally colored one-dimensional photonic crystals (1DPCs)
constructed by alternating assembly of poly(acrylamide-N,N′-methylene
bis(acrylamide))
(P(AM-MBA)) nanogels and TiO2 nanoparticles are reported
as high-performance colorimetric humidity sensors. The sensors with
bright colors display rapid response to relative humidity (RH) change
and reach sensing balance in 0.5 s. By varying RH from 47.0% to 89.3%,
stopband of a sensor changes from 426 to 668 nm, almost spanning the
whole visible range. Meanwhile, visual sensing of RH possesses good
reversibility and repeatability. Moreover, the sensors with delicate
patterns are facilely fabricated by partial UV photodegradation of
the polymer layers with nano TiO2 as catalyst. The delicate
patterns and backgrounds show different colors and change color simultaneously
and quickly by varying the ambient humidity. Accurate QR code pattern
is also realized on the PC sensor; it is found successful reading
of the data is only achieved by increasing RH to realize high color
contrast between the code and background. Given their excellent properties,
the porous hybrid PCs are promising as high-performance humidity sensors
with potential display, decoration, information-storage, and encryption
functions.