A fluoride selective dipyrromethane-TCNQ colorimetric sensor based on charge-transfer.

Area of Science:

• Chemical Sensing
• Materials Science
• Analytical Chemistry

Background:

• Colorimetric sensors offer a simple method for ion detection.
• Developing selective sensors for fluoride ions is crucial for environmental and health monitoring.
• Charge-transfer compounds are promising candidates for sensor development.

Purpose of the Study:

• To develop a selective colorimetric sensor for fluoride ion (F-) determination.
• To investigate the sensing mechanism based on charge-transfer interactions.
• To evaluate the sensor's performance in the presence of other halide ions.

Main Methods:

• Synthesis of a dipyrromethane(donor)-7,7',8,8'-tetracyanoquinodimethane (acceptor) charge-transfer compound.
• Colorimetric and spectrophotometric analysis for fluoride ion detection.
• Testing sensor selectivity in the presence of chloride (Cl-), bromide (Br-), and iodide (I-) ions.
• Solid-state sensing using reflectance measurements.

Main Results:

• The sensor exhibited excellent selectivity for fluoride ions (F-) over other halides.
• A color change was observed, enabling naked-eye detection.
• Spectrophotometric analysis confirmed the quantitative determination of F-.
• The sensing mechanism involves the interruption of donor-acceptor charge-transfer by F-.
• Solid-state sensing performance mimicked solution-based detection.

Conclusions:

• The developed charge-transfer compound serves as a highly selective colorimetric sensor for fluoride ions.
• The sensor demonstrates potential for practical applications in fluoride determination.
• The mechanism of interrupted charge-transfer provides a basis for designing similar sensors.