A flexible ten carbon long-chain salamo-like fluorescent probe for highly efficient and selective recognition of Cr2O72− ions, mechanism and practical application

Based on salicylaldehyde unit, we designed and synthesized a novel fluorescent chemical probe DSS, which has a flexible long chain and contains ten methylene units. The experimental results showed that the fluorescent probe DSS can efficiently and selectively recognize Cr₂O₇²⁻ anions, having a detection limit LOD of 1.14 × 10⁻⁷ M. Additionally, the binding constant (Ka) of the probe was 3.75 × 10⁴ M⁻¹, the minimum quantification limit LOQ was as low as 3.82 × 10⁻⁷ M. We systematically studied the recognition mechanism of fluorescence chemical sensor DSS through fluorescence and UV visible spectroscopy. Significantly, the fluorescence of the chemosensor DSS can be remarkably quenched by Cr₂O₇²⁻ via the Internal Filtering Effect (IFE). Based on this phenomenon, a novel salamo-like fluorescence method for detection of Cr₂O₇²⁻ was established. The proposed fluorescent method was successfully applied to the detection of Cr₂O₇²⁻ in rainwater, tap water, and Yellow River water.