White Light-Emitting Multistimuli-Responsive Hydrogels with Lanthanides and Carbon Dots

Polymers that confer changes in optical properties in response to chemical or mechanical cues offer diverse sensing applications, particularly if this stimuli response is accessible in humid or aqueous environments. In this study, luminescent hydrogels were fabricated using a facile aqueous process by incorporating lanthanide ions and carbon dots (CD) into a network of polyacrylamide and poly(acrylic acid). White luminescence was obtained by tuning the balance of blue-light-emitting CD to green- and red-light-emitting lanthanide ions. Exploiting the combined specific sensitivities of the different emitters, the luminescent hydrogel showed chromic responsiveness to multiple stimuli, including pH, organic vapors, transition-metal ions, and temperature. The white-light-emitting hydrogel was also stretchable with a fracture strain of 400%. We envision this photoluminescent hydrogel to be a versatile and multifunctional material for chemical and environmental sensing.