Dual-color and specific luminescence detection of Pd²⁺ ions using iridium(III) complex-based probes in food samples

The toxicity of palladium (Pd) is highly associated with its oxidative states, thus it is important to develop specific detection methods for Pd²⁺ ions in food and environmental systems. However, the reliable and selective detection of Pd²⁺ ions remains challenging. Here, we report two iridium(III) complexes with dual colors (717 nm and 637 nm) for the specific detection of Pd²⁺ ions, with the 3,3'-diamino group being used as a specific recognition unit for Pd²⁺ ions for the first time. The dual-color probes showed a luminescence quenching response to Pd²⁺ ions in aqueous solution within 1 min, along with an obvious color change under UV irradiation. Moreover, complexes 1-2 allow sensitive and selective detection of Pd²⁺ ions with a limit of detection (LOD) of 0.69 μM and 0.26 μM, respectively, showing a good linear response for Pd²⁺ ions in the range of 1-13 μM (R² = 0.985) and 1-9 μM (R² = 0.996). Finally, the probes were successfully applied for the detection of Pd²⁺ ions in food and environmental samples with good recoveries ranging from 85.4 to 118.7 %, providing a robust analytical tool for Pd²⁺ ions quantification for onsite setting.