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Active Hydrogen Free, Z-Isomer Selective Isatin Derived "Turn on" Fluorescent Dual Anions Sensor
Muthumanickam Shenbagapushpam1,2, Bosco Christin Maria Arputham Ashwin3, Paulpandian Muthu Mareeswaran4
1Department of Chemistry, Thiagarajar College (Affiliated to Madurai Kamaraj University), Madurai, Tamil Nadu, India.
Journal of Fluorescence
|June 19, 2024
Summary
A novel sensor, PQI, selectively detects fluoride (F-) and nitrate (NO3-) ions in water using fluorescence. This "on-off" sensor exhibits high sensitivity and a low limit of detection, crucial for environmental monitoring.
Area of Science:
- Analytical Chemistry
- Materials Science
- Environmental Science
Background:
- Development of selective and sensitive fluorescent sensors for anions is critical for environmental and biological monitoring.
- Isatin-based π-conjugated systems offer promising platforms for chemosensor design due to their tunable electronic properties.
Purpose of the Study:
- To develop an efficient and selective fluorescence "on-off" sensor for the simultaneous detection of fluoride (F-) and nitrate (NO3-) ions in aqueous media.
- To investigate the sensing mechanism and binding interactions between the developed sensor and target anions.
Main Methods:
- Synthesis and characterization of 1-(prop-2-yn-1-yl)-3-(quinolin-3-ylimino)indolin-2-one (PQI) as a fluorescent probe.
- Fluorescence spectroscopy was employed to study the sensing behavior of PQI towards various anions.
- Nuclear Magnetic Resonance (NMR) titrations (1H and 13C) were used to elucidate the binding modes and mechanisms.
- Job's plot analysis was performed to determine the stoichiometry of the complexation.
Main Results:
- The developed PQI sensor demonstrated selective and efficient "on-off" fluorescence sensing for both F- and NO3- ions.
- The sensing mechanism involves Photoinduced Electron Transfer (PET) and non-covalent interactions between PQI and the anions.
- Strong binding interactions were observed with association constants of 2.5 × 10^4 M⁻¹ for F- and 2.2 × 10^3 M⁻¹ for NO3-.
- The sensor exhibited low limits of detection (LOD) of 6.91 × 10⁻⁷ M for F- and 9.93 × 10⁻⁷ M for NO3-, within WHO limits.
Conclusions:
- PQI serves as a highly effective fluorescent probe for the selective and sensitive detection of dual anions F- and NO3- in aqueous solutions.
- The unique buckled structure of the Z-isomer of PQI contributes to the selectivity of anion sensing.
- The low LOD values make PQI a promising candidate for real-world applications in environmental monitoring.
