A novel cost-effective disposable porous graphene electrode (P-GE) modified with bismuth nanoneedles (nano-BiNDs) is proposed as a "mercury-free" sensor for detecting heavy metals through smartphone-assisted electrochemical sensing. The P-GE was fabricated using screen-printing. Nano-BiNDs were generated on the P-GE by potentiostatic electrodeposition. Using an optimal potential of -1.20 V (vs. pseudo-Ag/AgCl) and a deposition time of 200 s, the nano-BiNDs had an average length and width of 189 ± 5 nm and 20 ± 2 nm, respectively. The analytical performances of the fabricated sensing platform were demonstrated by detecting Cd2+ and Pb2+ using square-wave anodic stripping voltammetry (SWASV) under optimized conditions. In the optimal conditions, the fabricated sensor exhibited sharp, well-defined stripping peaks for Cd2+ and Pb2+ with excellent peak-to-peak separation. The linear detection ranges were from 0.01 to 50 μg mL-1 for Cd2+ and 0.006-50 μg mL-1 for Pb2+. The detection limits for Cd2+ and Pb2+ were 3.51 and 2.10 ng mL-1, respectively. The developed portable sensor demonstrated high sensitivity, good repeatability, reproducibility, and anti-interference properties. The proposed portable sensor quantified Cd2+ and Pb2+ in commercial seaweed products with good accuracy, consistent with the results obtained using the standard ICP-OES method.
Keywords: Heavy metal ion; Nano-BiNDs; Porous graphene; SWASV; Screen-printed electrodes.
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