Dual-Functional PC/PL/N-CQD Hydrogel for Brilliant Green Degradation and Metronidazole Detection.

3D fluorescent hydrogels have been developed from pullulan, pectin and nitrogen-doped carbon quantum dots (N-CQDs). This hydrogel was fabricated for the metronidazole detection in aqueous solutions and subjected to a dye-degradation test with Brilliant Green (BG). We studied the materials' morphology, elemental composition, and optical properties by several characterization techniques such as SEM, EDS, fluorescence spectroscopy, XRD, XPS, FTIR, and UV-Vis spectroscopy. We explored the photocatalytic efficiency of the nanocomposite in the degradation of BG under different experimental conditions such as dye concentration ranging from 10 to 50 mg/L, catalyst weight from 0.05 to 0.25 g, and pH from 2 to 11. The sample was exposed to daylight for 30 min. The degradation process was consistent with the kinetics of the first-order reaction with an apparent rate constant for the wavelength of dye at 625 nm. The reusability test result indicated that the degradation efficiency of the nanocomposite was retained at 71.36% after six consecutive cycles. Moreover, the nanocomposite was found to be a stable and reliable fluorescence probe for selective and sensitive metronidazole determination. The detection limit of metronidazole is as low as 0.20 µM with a wide linear concentration range of 0-38 µM. On the whole, this research opens a new avenue of PC/PL/N-CQDs nanocomposite as a multifunctional material for the sensitive detection of metronidazole and the efficient removal of BG dye.