Single-drop electrodeposition of nanoneedle-like bismuth on disposable graphene electrode for on-site electrochemical detection of cadmium and lead.

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 Cd and Pb using square-wave anodic stripping voltammetry (SWASV) under optimized conditions. In the optimal conditions, the fabricated sensor exhibited sharp, well-defined stripping peaks for Cd and Pb with excellent peak-to-peak separation. The linear detection ranges were from 0.01 to 50 μg mL for Cd and 0.006-50 μg mL for Pb. The detection limits for Cd and Pb were 3.51 and 2.10 ng mL, respectively. The developed portable sensor demonstrated high sensitivity, good repeatability, reproducibility, and anti-interference properties. The proposed portable sensor quantified Cd and Pb in commercial seaweed products with good accuracy, consistent with the results obtained using the standard ICP-OES method.