Ratiometric fluorescence response of a dual light emitting reduced carbon dot/graphene quantum dot nanohybrid towards As(iii)

Abstract

In this study, we reported a unique, dual light emitting, and fully carbon-based nanohybrid system comprising glutathione-functionalized reduced carbon dots (GSH-f-rCDs) having emission in the violet region and green-emitting graphene quantum dots (GQDs). The rCD component was derived from CDs by a chemical modification process. Compared to the pristine form, the reduced version of the CDs demonstrated superior fluorescence intensity, high quantum yield, and low bandwidth of emission. The ratiometric fluorescence response of the as-prepared nanohybrid was tested to evaluate its efficiency for detecting As(III) in water samples. The detection process primarily relied on the relative quenching of the violet emission over the green emission due to the specific interaction between GSH and As(III). The relative change in the ratiometric intensity could be correlated to the amount of As(III) in the concentration range of 0.5–100 ppb, which possessed a lower detection limit of 0.5 ppb. The ratiometric change in intensity also resulted in the colour variation of the sensory liquid in a dose-dependent manner. Based on this multi-colour variation behaviour, GSH-f-rCD/GQD-coated test papers were prepared and used for the visual detection of As(III). With the successive addition of As(III) (>5 ppb), the test papers underwent a change in colour from blue to green when illuminated in a UV chamber. Thus, GSH-f-rCD/GQD was successfully utilized for the quantitative and semi-quantitative visual detection of As(III) in water samples.