Lanthanide coordinated multicolor fluorescent polymeric hydrogels for bio-inspired shape/color switchable actuation through local diffusion of Tb3+/Eu3+ ions

Lanthanide coordinated multicolor fluorescent polymeric hydrogels (MFPHs) are quite promising for various applications because of their sharp fluorescence bands and high color purity. However, few attempts have been carried out to locally regulate their fluorescence switching or shape deforming behaviors, but such studies are very useful for patterned materials with disparate functions. Herein, the picolinate moieties that can sensitize Tb3+/Eu3+ luminescence via antenna effect were chemically introduced into interpenetrating double networks to produce a robust kind of lanthanide coordinated MFPHs. Upon varying the doping ratio of Tb3+/Eu3+, fluorescence colors of the obtained hydrogels were continuously regulated from green to orange and then red. Importantly, spatial fluorescence color control within the hydrogel matrix could be facilely realized by controlled diffusion of Tb3+/Eu3+ ions, producing a number of 2D hydrogel objects with local multicolor fluorescent patterns. Furthermore, the differential swelling capacities between the fluorescent patterned and non-fluorescent parts led to interesting 2D-to-3D shape deformation to give well-defined multicolor fluorescent 3D hydrogel configurations. Based on these results, bio-inspired synergistic color/shape changeable actuators were demonstrated. The present study provided a promising strategy to achieve the local fluorescence and shape control within lanthanide coordinated hydrogels, and is expected to be expanded for fabricating useful patterned materials with disparate functions.