Assessment of the Sensitivity of a Fluorescent Squaraine Dye to Heavy Metal Ions
DOI:
https://doi.org/10.26565/2312-4334-2025-4-78Keywords:
Squaraine dye, Metal detection, Heavy metalsAbstract
The contamination of natural water systems with heavy metal ions poses a significant global environmental and public health threat due to their persistence, bioaccumulation, and severe toxicological effects. Consequently, the development of rapid and sensitive detection methods is essential for effective water quality monitoring. Squaraine dyes represent a promising class of chemosensors for heavy metal detection owing to their high molar extinction coefficients, near-infrared fluorescence, and pronounced spectral responsiveness to metal binding. In this study, we evaluate the sensitivity of the symmetric squaraine dye SQ-1 toward four environmentally relevant heavy metal ions – Cu²⁺, Zn²⁺, Ni²⁺, and Pb²⁺ – and explore its applicability within a β-lactoglobulin/SQ-1 nanosystem for metal sensing in aqueous media. Spectroscopic analysis revealed metal-dependent modulation of SQ-1 optical properties, driven largely by alterations in dye aggregation and metal–dye coordination. Ni²⁺ and Pb²⁺ promoted SQ-1 deaggregation and enhanced fluorescence emission, whereas Cu²⁺ induced pronounced quenching consistent with strong coordination. Our results indicate that, SQ-1 retained its responsiveness in the presence of β-lactoglobulin fibrils, exhibiting metal-specific fluorescence changes indicative of combined dye–metal–fibril interactions. Further studies are warranted to assess SQ-1 performance toward additional metal ions and to elucidate the molecular mechanisms underlying metal-induced modulation of its photophysical behavior.
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