RGO/MWCNTs-COOH 3D hybrid network as a high-performance electrochemical sensing platform of screen-printed carbon electrodes with an ultra-wide detection range of Cd(II) and Pb(II)

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• Developed a high-performance SPCE sensor based on rGO-MWCNTs-COOH 3D hybrid. • The detection of Cd 2+ and Pb 2+ with an ultra-wide linear range was performed. • The electrochemical behaviour of modified SPCE reveals the sensing mechanism. • Shows an application potential for directly detecting high-concentration samples. In this study, we develop a high-performance screen-printed carbon electrodes (SPCE) based on reduced graphene oxide (rGO) - carboxy-functionalized multi-walled carbon nanotubes (MWCNTs-COOH) hybrids for simultaneous detection cadmium ions (Cd 2+ ) and lead ions (Pb 2+ ). The surface morphology and electrochemical behaviour of the modified SPCE was characterised by SEM, AFM, EIS and CV. The control steps of the redox reaction on the modified SPCE and the influence of the morphology of modified SPCE on the shape of stripping peak have also been studied. In addition, Nafion and in-situ bismuth film (BFE) methods were introduced in this detection system to enhance the stability and stripping performance. Under the optimal experimental conditions, the Nafion/rGO-MWCNTs-COOH/SPCE showed excellent catalytic activity towards Cd 2+ and Pb 2+ (pH = 4.5) with a significantly increased SWASV peak current compared to the unmodified SPCE. The developed sensor obtains an ultra-wide dynamic concentration range from 0.1 to 1350 μg·L −1 due to the introduction of 3D hybrid material and the optimisation of the detection parameters. The limit of detection (S/N = 3) for Cd 2+ and Pb 2+ was 0.04 μg·L −1 and 0.02 μg·L −1 , respectively. Furthermore, the applicability of the developed SPCE was demonstrated by detecting Cd 2+ and Pb 2+ in tap water and lake water.