Dynamically crosslinked carbon dots/biopolymer hydrogels exhibiting fluorescence and multi-stimuli logic-gate responses

Intelligent soft materials have been intensively investigated during the past few decades. Herein, nanocomposite hydrogels are constructed for detection of multiple external stimuli by the naked-eye. The nanocomposite hydrogels were prepared by reacting oxidized sodium hyaluronate with carbon dots. As a result, the hydrogels are capable of self-healing and strong fluorescence, as well as having multiple stimuli-responsive properties. The gelation mechanism of the dynamic crosslinked reaction in these hydrogels was demonstrated. Interestingly, the hydrogels exhibit sharp phase transitions and fluorescence changes in response to multiple external stimuli, including various chemical redox reactions, enzymes, biomolecules, cations, and pH values. This stimuli-responsive property has been successfully exploited to design programmable logic-gate responses. This investigation opens the door to developing logic-gate responsive hydrogels, which may become a powerful method to visually detect multiple environmental changes through the observation of the phase transition and fluorescence change.