Novel nanosensor of cobalt(II) and copper(II) constructed from graphene quantum dots modified with Eriochrome Black T

Detection of heavy transition metals is of importance protecting humans and the environment from their toxicity. Amongst them, copper(II) and cobalt(II) need more attention due to their wide applications in industry, in which exposures with excess amounts of them cause heathy concerns. Hence, fast and efficient distinguishing copper(II) and cobalt(II) could be worthy. While electrochemical approaches could determine these cations, expensive instrumentation and time-consuming analysis are significant drawbacks, leading to concentrations on spectroscopic and colorimetric pathways. Herein, graphene quantum dot was modified with Eriochrome Black T (EBT) to generate a novel sensor with the ability of sensing mentioned cations. This new nanocompound demonstrated new optical properties when complexed with cobalt(II) in natural pH, and copper(II) in acidic media. Both cations successfully were detected by the new nanosensor through revealing distinct spectroscopic signals. Moreover, cobalt(II) was distinguished by this sensor colorimetrical, appearing green solution. Linear ranges of cobalt(II) and copper(II) were obtained as 0.02-0.08 M and 0.015-0.2 M, with the limit of detections 0.014 and 0.018 M, respectively.