A Solid-State Fluorescence Sensor for Nitroaromatics and Nitroanilines Based on a Conjugated Calix[4]arene Polymer

Area of Science:

• Materials Science
• Polymer Chemistry
• Analytical Chemistry

Background:

• Conjugated polymers are crucial for advanced material applications.
• Developing sensitive and selective sensors for hazardous materials remains a significant challenge.
• Calixarene-based materials offer unique host-guest chemistry for molecular recognition.

Purpose of the Study:

• To synthesize and characterize a new conjugated polymer incorporating calix[4]arene-oxacyclophane units.
• To investigate the photophysical properties of the synthesized polymer in solution and solid-state.
• To evaluate the polymer's efficacy as a sensory material for detecting nitroaromatic compounds.

Main Methods:

• Sonogashira-Hagihara cross-coupling for polymer synthesis.
• FTIR, NMR (1H, 13C, HSQC), and GPC for structural and molecular weight characterization.
• Fluorescence spectroscopy and vapor-phase analyte exposure for sensing studies.

Main Results:

• A highly emissive conjugated polymer (ΦF = 0.55) with a long excited-state lifetime (1.80 ns) was successfully synthesized.
• The polymer maintained similar photophysical properties in solution and solid-state due to bulky calixarene units preventing aggregation.
• Cast films of the polymer demonstrated high sensitivity in detecting nitroaromatics, with significant fluorescence quenching for 2,4-dinitrotoluene (>85%) and ortho-nitroaniline (90%).

Conclusions:

• The synthesized calixarene-based conjugated polymer is suitable for solid-state fluorescence sensing applications.
• The polymer's unique structure enhances molecular recognition and sensory response to specific analytes.
• The material shows promise for detecting explosive taggants and noxious nitroanilines in vapor phases.