A miniaturized and flexible cadmium and lead ion detection sensor based on micro-patterned reduced graphene oxide/carbon nanotube/bismuth composite electrodes

•rGO/CNT nanocomposite was successfully synthesized and micro-patterned on a flexible electrode (Au/PI) substrate by using a simple, low-cost MEMS fabrication method.•Novel rGO/CNT nanocomposite are uniformly distributed and patterned on the flexible substrate for the fabrication of miniaturized electrochemical heavy metal ions sensor. The CNTs was mixed with the rGOs to increase the surface area by preventing the rGO sheets being restacked and aggregated.•The influences of the mixed ratio of CNT and rGO in the composite fabrication on the electrochemical performance of integrated heavy metal ions sensor were investigated.•The physical and electrochemical properties of the as-fabricated CNT/rGO/Bi composite were investigated for being used as working electrode for electrochemical determination of Pb and Cd ions.•The fabricated electrochemical sensor with three electrodes (WE, CE, RE) on a flexible polyimide substrate exhibited high sensitivity, low detection limit, and wide linear range for Pb and Cd ions simultaneous detection.•Supplementary data includes electrochemical analysis, physical analysis and fabrication process. We proposed and fabricated a miniaturized, flexible, and fully integrated electrochemical sensor incorporated with micro-patterned reduced graphene oxide (rGO) and a carbon nanotube (CNT) composite working electrode on a flexible gold substrate. By in situ plating bismuth film, the fabricated sensor exhibited well-defined and separate stripping peaks for cadmium (Cd) and iron (Pb) ions, respectively. The CNT was mixed with the rGO in order to improve the performance of the sensor by increasing the electrode surface area. Several experimental parameters, including an electrolyte environment and electrodeposition conditions, were also carefully optimized to achieve the best stripping performance. Under optimal conditions, high sensitivities of 262nA/ppbcm2 (Cd) and 926nA/ppbcm2 (Pb) along with favorable detection limits of 0.6ppb (Cd) and 0.2ppb (Pb) were obtained. The sensor exhibited good linear responses to both ion types in the concentration range of 20ppb to 200ppb. Due to the enlargement of the electrode surface area, the determination efficiency toward target ions was significantly enhanced by the developed Au/rGOCNT/Bi modified electrode. The developed sensor shows high sensitivity, stability, and reliability for the detection of the target heavy metal ions. Finally, the fabricated sensor was successfully demonstrated to detect th