Trace-level simultaneous monitoring of multiple heavy metal ions using AlScN-based flexible electrochemical sensor

The development of a reliable electrochemical sensor for the trace-level detection of hazardous heavy metal ions (HMIs) is a critical challenge, as they are very toxic to the environment and public health. Herein, a flexible electrochemical sensor based on ternary aluminum scandium nitride (AlScN) has been deposited over a flexible stainless-steel mesh (SSM) substrate using a scalable magnetron co-sputtering technique for the simultaneous detection of Pb^2 + , Cd²⁺ and Hg²⁺ at trace levels. The proposed sensor exhibits excellent detection performance for the HMIs under the optimised experimental parameters. The broad linear ranges of 1-5 μM, 1-5 μM and 1-6 μM are obtained for Pb²⁺, Cd²⁺ and Hg²⁺, respectively. The achieved limit of detection (LOD) values are 22.4, 18.53 and 16.4 nM, while the corresponding sensitivities are 80.93, 81.4 and 91.4 μA/μM, respectively. The LOD values are lower than the standard ones reported by the World Health Organisation for drinking water. The AlScN/SSM electrode reveals outstanding reproducibility, stability and selectivity in electrochemical sensing applications. Furthermore, the real-world applicability of the as-fabricated sensor is demonstrated by its ability to determine Pb²⁺, Cd²⁺ and Hg²⁺ in environmental water, including tap and canal water. This work underscores the potential of Transition metal nitrides (TMNs) for next-generation flexible HMI electrochemical sensors for environmental analysis.