In situ bismuth ion exchange plating micro-electrochemical sensor based on laser-induced graphene for trace Cd2+ and Pb2+ detection

Rapid, sensitive, and on-site detection of heavy metal ions in the environment is of great significance for protecting human health and maintaining ecological balance. This work presents a novel approach for the synthesis of nitrogen and bismuth co-doped, homogeneous porous petaloid graphene on polyimide films through ion exchange plating and laser direct writing techniques. The electrochemical sensing platform constructed by this technique exhibits excellent detection performance for trace amounts of the heavy metals lead and cadmium ions. Particularly, the mild surface ion exchange and self-metallization strategy enables in situ incorporation of bismuth elements with ultra-low material consumption. At the same time, the laser direct writing method can be utilized to create multiple electrode patterns, enhancing the sensor's versatility. The synergistic effect between the homogeneous porous structure of graphene and the abundant bismuth and nitrogen functional groups endows the new micro-electrochemical sensor with satisfactory sensing performance for simultaneous detection of Cd2+ and Pb2+ using differential pulse stripping voltammetry. The fabricated sensor exhibits superior performance with a linear range of 1.0–100.0 μg/L, a detection limit of 0.207 μg/L and 0.410 μg/L (S/N = 3) for Cd2+ and Pb2+, respectively, and demonstrates good anti-interference capability, stability, and repeatability. When applied to detecting Cd2+ and Pb2+ in actual porcelain applique and tea samples, it demonstrates good recovery rates ranging from 95.3% to 106.3%. Consequently, this portable and sensitive micro-electrochemical sensor based on laser-induced graphene shows promising potential for application in environmental monitoring and protection.