Silver ion-induced fluorescent quenching in aqueous graphene oxide suspensions

In this work, we demonstrate that the fluorescence of aqueous graphene oxide (GO) suspensions is significantly quenched upon the introduction of silver ions (Ag⁺). The extent of quenching exhibits a clear dependence on both Ag⁺ concentration and interaction time. Comprehensive characterization using TEM, SEM, AFM, and UV-visible spectroscopy confirms that Ag⁺ ions undergo in situ reduction and subsequently deposit onto the GO surface. Altogether, GO was shown to drive the spontaneous reduction of silver ions to silver nanoparticles while providing a support structure for the particles to nucleate and grow. The reduction mechanism was attributed to galvanic displacement driven by the relative reduction potential difference between GO and silver. An ultraviolet photoelectron spectroscopy study was carried out on GO to support this hypothesis. Finally, the type of interaction between silver and GO was investigated using FT-IR and XPS studies. Both studies confirmed that the main point of interaction is through the hydroxyl moieties of GO. Based on the obtained data, three possible mechanisms for fluorescent quenching behaviour were presented. It's anticipated that GO would provide a convenient pathway for silver ion sensing and silver-based nanophotonic applications through the discussed interaction pathways.