Direct determination of graphene quantum dots based on terbium-sensitized luminescence

Graphene quantum dots (GQD) were determined in water samples using terbium-sensitized luminescence (TSL). Terbium ions complex with GQD due to the carboxylic groups that are usually present in these nanomaterials, increasing the luminescence signal of terbium. In Tb(III)-GQD complexes, GQD absorb energy at their characteristic excitation wavelength and transfer it to terbium ion, which emits at its particular emission wavelength. The analytical signal, measured at lambda(exc) =257 nm and lambda(em) = 545 nm, increases proportionally to GQD concentration between 50 and 500 mu g L-1. Under optimum conditions, the proposed method presents a detection limit of 15 mu g L-1 and is selective to cQp in the presence of other nanomaterials of similar size. As GQD are highly water-soluble, they are potential contaminants in environmental or drinking waters water samples, and hence the method was applied to the analysis of different drinking waters which were the target samples for the application of the developed method. (C) 2018 Elsevier B.V. All rights reserved.