A highly selective pyrazole-hydrazide-based colorimetric and "turn on" fluorometric sensor for fluoride with portable...

Area of Science:

• Analytical Chemistry
• Materials Science
• Organic Chemistry

Background:

• Fluoride ion detection is crucial for environmental monitoring and human health.
• Existing methods for fluoride detection often require complex instrumentation.
• Development of selective and sensitive chemosensors is highly desirable.

Purpose of the Study:

• To design and synthesize a novel pyrazole-hydrazide-based chemosensor, (E)-N'-((5-(4-Chlorophenoxy)-3-methyl-1-phenyl-1H-pyrazol-4-yl)methylene)-4-nitrobenzohydrazide (PNH).
• To achieve selective detection of fluoride ions using dual-mode colorimetric and fluorometric responses.
• To develop practical applications for the chemosensor in portable detection devices.

Main Methods:

• Synthesis of the pyrazole-hydrazide derivative (PNH).
• Spectroscopic analysis (UV-visible and fluorescence) for sensing studies.
• ¹H NMR titrations to confirm the sensing mechanism.
• Density Functional Theory (DFT) calculations to elucidate the binding mechanism.

Main Results:

• PNH exhibits a distinct color change (colorless to yellow) and turn-on fluorescence at 510 nm upon interaction with fluoride ions.
• The sensor demonstrates high selectivity for fluoride ions over other common anions.
• A low detection limit of 12 nM was achieved with satisfactory linearity.
• DFT studies supported the proposed binding mechanism between PNH and fluoride ions.

Conclusions:

• PNH is a highly sensitive and selective chemosensor for fluoride ion detection.
• The developed sensor can be integrated into practical devices like polymer-based films and paper strips.
• These devices offer a rapid, portable, and visible method for fluoride detection, eliminating the need for specialized equipment.