“On-plant” wearable electrochemical sensor for atmospheric lead monitoring

Considering the extremely high toxicity of lead (Pb), early detection of atmospheric Pb levels is paramount for the implementation of preventive measures, to contain sources of emission, to minimize both human and plant exposure and to prevent accumulation in the biosphere. This work demonstrates a wearable "on-plant" sensor for electrochemical Pb detection in atmospheric aerosol samples. The sensor is screen-printed onto a flexible self-adhesive vinyl-based matte substrate which enables its attachment on plant leaves. It features a bismuth/Nafion-coated carbon working electrode transducer covered with a polyvinyl alcohol (PVA) membrane which serves as a passive in-situ gas collection layer and as an electrolyte-containing matrix. The Pb collected at the interface between the sample in the gas phase and the acetate buffer solution (ABS) embedded within the PVA membrane is measured by square wave anodic stripping voltammetry (SWASV). Different steps of the fabrication process were optimized and the detection of on plant leaves was demonstrated. Simulation experiments were conducted with a Pb-containing aerosol sprayed on the leaves to evaluate the effect of various operational parameters such as long-term stability, spraying time, accumulation time, or sensor/leaf bending. The "on-plant" sensor allows remote near real-time monitoring of Pb levels as low as 50 μg L^-1 in ambient air using a portable miniaturized potentiostat, and can be expanded to other target metals, forming the basis of an early warning system for atmospheric heavy metals exposure.