We report potentiometric performances of ion-to-electron transducer based on reduced graphene oxide (RGO) for application of all-solid-state potassium ion sensors. A large surface area and pore structure of RGO are obtained by a hydrothermal self-assembly of graphene oxide. The extensive electrochemical characterization of RGO solid contact at the interface of ionselective membrane and gold electrode shows that the potassium ion-selective electrode based on RGO had a high sensitivity (53.34 mV/log[K+]), a low detection of limit (− 4.24 log[ K+], 0.06 mM) a good potential stability, and a high resistance to light and gas interferences. The potentiometric K+- sensor device was fabricated by combining of screen-printed electrodes and a printed circuit board. The K+- sensor device accurately measures the ion concentration of real samples of commercial sports drinks, coke and orange juice, and then transfers the collected data to a mobile application through a Bluetooth module. The screen-printed ion sensors based on RGO solid contact show a great potential for real-time monitoring and point-of-care devices in human health care, water-treatment process, and environmental and chemical industries.

    Abstract
    1 Introduction
    2 Experimental
        2.1 Materials
        2.2 Preparation of RGO hydrogel
        2.3 Preparation of ISM–RGOAu electrode
        2.4 Fabrication of a screen-printed K+-sensor
        2.5 Characterization
    3 Results and discussion
    4 Conclusions
    Acknowledgements 
    References

• Jo Hee Yoon(Department of Chemical Engineering, Kangwon National University)
• Hong Jun Park(Department of Chemical Engineering, Kangwon National University)
• Seung Hwa Park(Department of Chemical Engineering, Kangwon National University)
• Kyoung G Lee(Nano‑bio Application Team, National Nanofab Center)
• Bong Gill Choi(Department of Chemical Engineering, Kangwon National University)