In situ synthesis of carbon quantum dots@gum Arabic-silver nanoparticles as a 'turn-off–on' fluorescent sensor for rapid detection of hydrogen peroxide and mercury (II) ions in aqueous media.

In this paper, we report on the development of an 'off–on' fluorescent probe for the detection of hydrogen peroxide (H₂O₂) and mercury ions (Hg²⁺) using an in situ synthesized carbon quantum dot and gum Arabic silver nanoparticle composite (CQDs@GA-Ag NPs). Electron microscopy measurement clearly shows that CQDs are attached to the surface of the GA-Ag NPs. The fluorescence intensity of the CQDs was dramatically quenched in the synthesized nanocomposite via the inner filter effect (IFE) mechanism. After adding H₂O₂ to the nanocomposite system, the Ag NPs got oxidized leading to the formation of Ag⁺ ions, and the CQDs regained their photoluminescence (PL) property. This facilitates the detection of H₂O₂ with an extremely low detection limit of 1.02 μM. Furthermore, the as-developed nanocomposite was also tested for the detection of Hg²⁺ ions, obtaining a remarkably low detection limit of 1.82 μM. The developed probe was extremely selective over a wide range of interfering ions and substances. [ABSTRACT FROM AUTHOR]