Nonmodified Laser-Induced Graphene Sensors for Lead-Ion Detection

Electrochemical detection, especially anodic stripping voltammetry (ASV), has been widely used in the detection of heavy metal ions because of its high sensitivity, low detection limit, as well as on-site and real-time detection capability. However, ASV detection typically relies on modified sensors, which complicates the preparation process and introduces contaminants to the tested solutions. Herein, we developed a preconcentration relaxation strategy to improve detection performances of bare sensors without modification. Specifically, in the preconcentration step of ASV, the solution stirring did not run throughout the whole preconcentration process but stopped before the end of preconcentration, remaining as a relaxation period for metal ions fully depositing. To verify this strategy, we fabricated porous laser-induced graphene sensors without modification to detect lead ions. With the preconcentration strategy, the detection linear range was widened from 30–100 to 1–100 μg·L–1, and the sensitivity was increased from 0.1362 μA·(μg·L–1)−1 to 0.1772 μA·(μg·L–1)−1 in 1–5 μg·L–1 and 0.7081 μA·(μg·L–1)−1 in 10–100 μg·L–1. Moreover, the limit of detection reached 0.5 μg·L–1 (S/N = 3). This work sheds light on the accurate and effective detection of heavy metal ions.