Highly Selective and Scalable Molecular Fluoride Sensor for Naked-Eye Detection

Area of Science:

• Chemical Sensors
• Materials Science
• Environmental Monitoring

Background:

• Fluoride is ubiquitous, and high intake poses health risks.
• Accurate and accessible fluoride detection is crucial for public health.
• Existing detection methods often require specialized equipment.

Purpose of the Study:

• To synthesize novel Schiff base-derived molecular sensors for fluoride detection.
• To develop a selective and visually detectable colorimetric response for fluoride ions (F⁻).
• To establish a practical and scalable method for fluoride sensing.

Main Methods:

• One-pot synthesis of diaminomaleonitrile-based Schiff base sensors.
• Colorimetric analysis for naked-eye detection of fluoride ions.
• Anion selectivity testing against common interfering species.
• ¹⁹F Nuclear Magnetic Resonance (NMR) for mechanism elucidation.
• Theoretical calculations to understand the sensing mechanism.

Main Results:

• A terephthalaldehyde adduct Schiff base sensor exhibited a distinct color change at 2 ppm fluoride.
• The sensor demonstrated high selectivity for fluoride over other tested anions.
• ¹⁹F NMR confirmed the formation of the HF₂⁻ intermediate.
• Theoretical studies indicated a deprotonation-triggered bathochromic shift mechanism.
• Scalable synthesis from accessible materials was achieved.

Conclusions:

• A highly selective and visually detectable Schiff base sensor for fluoride has been developed.
• The sensor provides a practical, low-cost solution for on-site fluoride monitoring.
• The facile synthesis and scalability enhance its potential for widespread application in public health surveillance.