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<p>A dual-responsive fluorescent chemosensor based on a 1,3,4-oxadiazole-linked bis-indole scaffold (FM) was developed for the selective and sensitive detection of 2,4,6-trinitrophenol (TNP) and iron ions (Fe<sup>3</sup>⁺ and Fe<sup>2</sup>⁺) in aqueous media. The probe exhibits strong photophysical properties, including a prominent emission at 438&#xa0;nm and a large Stokes shift of 79&#xa0;nm. Upon interaction with TNP or iron ions, a significant fluorescence “turn-off” response and bathochromic shifts were observed, attributed to π–π stacking, hydrogen bonding, and coordination interactions. Job’s plot analysis revealed a 2:3 binding stoichiometry for TNP and 1:1 for both iron species, indicating distinct recognition mechanisms. For TNP, a high Stern–Volmer quenching constant (K<sub>sv</sub> = 113.98 × 10<sup>3</sup> M⁻<sup>1</sup>) and a low detection limit (LOD = 59 nM) were obtained, outperforming many previously reported sensors. The probe also demonstrated reliable detection of Fe<sup>3</sup>⁺ and Fe<sup>2</sup>⁺ ions with LOD values of 2.95 µM and 16.2 µM, respectively. The FM sensor exhibited excellent photostability, rapid response (&lt; 30&#xa0;s), and high selectivity in the presence of competing analytes. Furthermore, a paper-based detection platform was successfully fabricated, enabling rapid visual detection of TNP under UV and daylight. These results highlight FM as a promising fluorescent sensor for environmental and security-related applications involving nitroaromatic explosives and metal ions.</p>

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A Dual-Responsive 1,3,4-Oxadiazole-Linked Bis-Indole Fluorescent Chemosensor for the Selective Detection of TNP and Iron Ions

  • 期刊论文

  • 发表日期：

    2025年12月18日

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  • Ayhan Altun,
  • Ibrahim F. Sengul,
  • Mehmet F. Saglam

摘要

A dual-responsive fluorescent chemosensor based on a 1,3,4-oxadiazole-linked bis-indole scaffold (FM) was developed for the selective and sensitive detection of 2,4,6-trinitrophenol (TNP) and iron ions (Fe3⁺ and Fe2⁺) in aqueous media. The probe exhibits strong photophysical properties, including a prominent emission at 438 nm and a large Stokes shift of 79 nm. Upon interaction with TNP or iron ions, a significant fluorescence “turn-off” response and bathochromic shifts were observed, attributed to π–π stacking, hydrogen bonding, and coordination interactions. Job’s plot analysis revealed a 2:3 binding stoichiometry for TNP and 1:1 for both iron species, indicating distinct recognition mechanisms. For TNP, a high Stern–Volmer quenching constant (Ksv = 113.98 × 103 M⁻1) and a low detection limit (LOD = 59 nM) were obtained, outperforming many previously reported sensors. The probe also demonstrated reliable detection of Fe3⁺ and Fe2⁺ ions with LOD values of 2.95 µM and 16.2 µM, respectively. The FM sensor exhibited excellent photostability, rapid response (< 30 s), and high selectivity in the presence of competing analytes. Furthermore, a paper-based detection platform was successfully fabricated, enabling rapid visual detection of TNP under UV and daylight. These results highlight FM as a promising fluorescent sensor for environmental and security-related applications involving nitroaromatic explosives and metal ions.