Self-assembling fluorescent hydrogel for highly efficient water purification and photothermal conversion

Employing fluorescent hydrogels for hazardous Hg(II) detection and removal is an efficient method for water purification. However, it remains challenging to establish a fluorescent system with low detection limit and high adsorption capacity that can readily be upcycled into a valuable material resource. Herein, we report on a fluorescent hydrogel with 0D sulfydryl-based carbon dots that are self-assembled with a 3D hydrogel network. The cellulose-based hydrogel exhibited good sensitivity for the detection of Hg(II) over a range from 0 to 40 µM with a limit detection of 3.0 × 10^-6 M. The adsorption experiments confirmed that the cellulose-based hydrogel exhibits good Hg(II) extraction capacity of over 662.25 mg g⁻¹ at room temperature, and can effectively reduce the Hg concentration to attain acceptable levels that comply with industrial water standards (0.05 mg L^-1). Subsequently, we used a facile strategy to convert the exhausted waste adsorbent by in-situ sulfurization into a suitable material for solar steam generation. The as-prepared upcycled aerogel evaporators exhibited excellent evaporation rates of ∼ 1.30 kg m⁻² h⁻¹ under one sun irradiation. These results not only provide a strategy for heavy metal ion recognition and adsorption, but also provide a route to recycle hazardous waste for seawater desalination.