posted on 2021-09-20, 16:09authored byTingting Xu, Sufang Guo, Miaomiao Li, Zhen Zhang, Baobao Pang, Yingmo Hu
Here, we report a composite film that shows multibending behaviors
upon ultraviolet/visible (UV/vis) and near-infrared (NIR) light irradiations.
First, an azobenzene-modified graphene oxide (AZO-GO) hybrid was prepared
by the covalently grafting of 4-(3-triethoxysilylpropyl-ureido)azobenzene
(TSUA) onto the surface of GO. A reversible change in the hydrophilicity
of AZO-GO was observed upon UV/vis irradiations, due to the effective trans–cis-photoisomerization of
azobenzene groups. Then, the AZO-GO hybrid powder was dispersed in
ethanol and homogeneously mixed with the poly(vinyl alcohol) (PVA)
aqueous solution to give a uniform and thin composite film (AZO-GO/PVA)
with good flexibility by casting. Upon UV irradiation, this film bends
rapidly toward the light source with a large amplitude and recovers
to the original shape upon subsequent visible irradiation, due to
the reversible trans–cis-photoisomerization
of azobenzene groups. Upon NIR irradiation, the film curls slightly
away from the light source, which is considered to be caused by the
photothermal effect of the GO component. This composite film is also
low-cost and uses facile manufacturing, with enhanced mechanical properties.
Finally, by combining three pieces of the composite films, mimicking
the reversible grabbing–release motions of a claw upon UV/vis
irradiation was achieved.