Carboxymethyl cellulose and sodium alginate-enhanced hydrogel for carbon dots loading: A novel platform for pH sensing and sensitive detection of Al3+ and Ag+

To address the challenges associated with the storage and application of traditional carbon dot (CDs) solutions, this study introduces a cyan fluorescent carbon dot-based hydrogel (CDs-SCH). The hydrogel was synthesized by integrating cyan fluorescent CDs, derived from penicillamine and m -phenylenediamine, with carboxymethylcellulose (CMC) and sodium alginate (SA), which was then mixed with acrylamide (AM). The resulting CDs-SCH hydrogel was extensively characterized, focusing on its morphology, chemical structure, and fluorescence behavior. The fluorescence intensity of the hydrogel was enhanced by 3.23 times compared to the original CDs. The fluorescence response of the CDs-SCH hydrogel to pH variations was examined, demonstrating its capability to visually monitor the freshness of aquatic products such as fish and shrimp. Furthermore, Al 3+ and Ag + ions were found to significantly modulate the fluorescence, with Al 3+ enhancing and Ag + quenching the fluorescence, displaying reliable detection limits and linearity. The hydrogel's ability to detect glutathione (GSH) via Ag + reduction to Ag was also explored. Additionally, the hydrogel exhibited stable Al 3+ adsorption, with the process following pseudo-second-order kinetics and the Langmuir adsorption model. As a versatile and responsive material, the CDs-SCH hydrogel holds potential for applications in intelligent food packaging and environmental ion detection.