"Three-in-one" integrated self-powered sensor for cadmium ion detection: On-site screening, sensitive quantification,...

Self-powered electrochemical sensors (SPES) have emerged as an eco-friendly detection technology, but reported SPES face challenges in on-site detection, quantitative sensitivity, and result credibility. To address these issues, a three-in-one SPES was developed that integrates on-site screening, sensitive quantification, and built-in verification functions, thereby realizing efficiency, sensitivity, and reliability. In the on-site screening process, the polyaniline (PANI)-based cathode exhibits a rapid multicolorimetric response (6-s signal response) to cadmium ions (Cd²⁺), enabling efficient semi-quantitative analysis without complex instrument. In the sensitive quantification process, V₂C MXene drives e^--h⁺ separation and enhances the power generation capacity. A linear relationship between the output power and Cd²⁺ concentration was established in the range between 1.5 nM and 10 μM with the limit of detection (LOD) of 0.5 nM (S/N = 3). During the built-in validation process, K₂S₂O₈ activation enhances the open-circuit voltage in the non-ohmic region, and K₂S₂O₈ transformation reduces ohmic loss (η_ohmic) in the ohmic region. This double reaction enables the orthogonal generation and effective separation of two power peaks, establishing an interdependent and verifiable mapping model. In summary, the novel SPES design offers a practical and versatile platform for efficient, sensitive and reliable detection.