Graphene oxide-derived carbonaceous sensor: turn-off fluorescence sensor for nanomolar detection of ruthenium ions in aqueous medium

Abstract

Ruthenium is a vital transition metal widely employed in diverse applications from medicinal to material applications. Though ruthenium has been positioned as safe and relatively less toxic than other metals, continuous exposure will cause undesirable effects. Due to the constantly increasing usage of ruthenium, a simple and straightforward detection methodology is immediately necessary. In the present study, a covalently functionalized graphene oxide derived chemosensor has been developed to detect Ru(III) under a complete aqueous medium. For this, graphene oxide (GO) is covalently functionalized on the edge carboxylic acid group with 2-(bis(pyridine-2-ylmethyl)amino)ethan-1-ol (PAE) through esterification, followed by further grafting on the basal plane with a dansyl fluorophore motif through a silyloxy propyl linkage. Each functionalization has been designed to create a feasible pathway for a Förster Resonance Energy Transfer (FRET) donor and acceptor energy transfer, where the metal-binding site is introduced through esterification and the signalling unit by the dansylation process. When exploring the application of the newly prepared GOPND carbonaceous material, a selective fluorescence quenching response has been observed with Ru(III) in an aqueous medium, which is utilized for the detection of Ru(III). A GOPND probe showed high selectivity towards Ru(III) over the presence of other common metal ions with a lower detection limit of 15 nM. The origin of this ‘turn-off’ sensing response is explained through the presence of both the bis(pyridyl) probe and the dansyl fluorophore in close proximity on GO, which facilitates the energy transfer. The specific turn-off fluorescence response of the GOPND with Ru(III) ions is rationalized through the FRET mechanism.