Anthryl-doped conjugated polyelectrolytes as aggregation-based sensors for nonquenching multicationic analytes.

Area of Science:

• Polymer Chemistry
• Analytical Chemistry
• Fluorescence Spectroscopy

Background:

• Developing selective and sensitive fluorescence-based sensors is crucial for detecting small molecules.
• Poly(p-phenylene ethynylene) (PPE) polymers offer tunable optical properties for sensing applications.
• Detecting multicationic small molecules often requires specialized approaches due to their charge and size.

Purpose of the Study:

• To demonstrate a fluorescence-based detection method for nonquenching, multicationic small molecules.
• To utilize a blue-emitting, polyanionic poly(p-phenylene ethynylene) (PPE) doped with green-emitting exciton traps.
• To investigate the analyte-induced aggregation and subsequent fluorescence color change.

Main Methods:

• Synthesis of a blue-emitting polyanionic poly(p-phenylene ethynylene) (PPE) doped with anthryl exciton traps.
• Solution-based experiments to observe the interaction of multicationic amines with the PPE.
• Spectroscopic analysis of fluorescence changes (color shift) upon analyte addition.
• Testing sensor sensitivity towards amines with varying cationic charges (mono-, di-, and multicationic).

Main Results:

• Multicationic amines (spermine, spermidine, neomycin) induced tightly associated aggregates of the PPE chains in solution.
• Analyte-induced aggregation enhanced exciton migration within the PPE.
• A visually noticeable blue-to-green fluorescence color change was observed, indicating successful detection.
• The sensor showed poor sensitivity to dicationic and monocationic amines, suggesting some selectivity.

Conclusions:

• A conjugated polyelectrolyte sensor based on analyte-induced aggregation can effectively detect multicationic amines.
• The sensor achieves detection through a visually distinct fluorescence color change.
• Nonspecific electrostatic interactions can lead to selective sensing, even for complex analytes like multicationic amines.