Crown ether functionalized graphene oxide as ultrasensitive electrochemical sensor for detection of potassium ions

Potassium ions play a significant role in human biological systems, however, in excess or less it is considered to be toxic for human health. Therefore the detection of potassium ions is of great importance and challenge. In this work, we synthesize a novel sensing materials of potassium ions based on 1-aza-18-crown-6 functionalized graphene oxide (Crown-GO). The microstructure of the composite is characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy. The results indicate that graphene oxide (GO) has been successfully functionalized by 1-aza-18-crown-6 via the nucleophilic addition reaction resulting in the formation of carbon-nitrogen covalent linkage. Then the Crown-GO composite is used as electrode modified materials to detect potassium ions by an innovative method, electrochemical impedance spectroscopy (EIS). In EIS measurements, 1-aza-18-crown-6 plays the role of molecular recognition probe, which captures potassium ions, and GO increases the binding ability of the composite materials to potassium ions. With the increase of the potassium ion concentration, the charge transfer resistance (Rct) at the surface of Crown-GO modified electrode decreases gradually. And the potassium ion concentration can be indirectly detected based on changes in Rct. This ultrasensitive electrochemical sensor exhibits a linear response to potassium ions in the range of 10−7–10−13 M with a detection limit of 10−15 M.