Fig. 6From: Glutathione-capped Syzygium cumini carbon dot-amalgamated agarose hydrogel film for naked-eye detection of heavy metal ionsCalibration graph plotted between the color intensities of hydrogel films and different concentrations of a Pb2+ ion in the range of 0.005–0.075 mM, b Fe3+ ion in the range of 0.0075–0.1 mM, and c Mn2+ ion in the range of 0.0075–0.1 mMBack to article page