A curcumin-based AIEE-active fluorescent probe for Cu²⁺ detection in aqueous solution

Area of Science:

• Materials Science
• Analytical Chemistry
• Organic Chemistry

Background:

• Curcuminoids are explored as metal ion probes, but their aggregation-caused-quenching (ACQ) limits aqueous applications.
• Tetraphenylethylene (TPE) incorporation imparts aggregation-induced emission (AIE) or aggregation-induced enhanced emission (AIEE), counteracting ACQ.
• Developing novel probes with enhanced fluorescence properties for aqueous environments is crucial.

Purpose of the Study:

• To synthesize and investigate TPE-modified curcumin derivatives (L1-4) for AIEE properties.
• To evaluate the potential of these derivatives as fluorescence probes for metal ion detection in aqueous solutions.
• To develop a sensitive and reliable method for detecting Cu²⁺ ions.

Main Methods:

• Synthesis of four TPE-curcumin analogues (L1-4).
• Characterization of AIEE properties and fluorescence titration experiments for Cu²⁺ detection.
• Determination of detection limit, binding ratio, and binding constant using techniques like mass spectrometry, Job's plot, and Benesi-Hildebrand analysis.
• Fabrication of L1-based indicator paper for practical Cu²⁺ sensing.

Main Results:

• Only L1 particles exhibited successful AIEE properties and functioned as an on-off fluorescence probe for Cu²⁺.
• The detection limit for Cu²⁺ was determined to be 1.49 × 10^-7 mol L^-1.
• The binding ratio of L1 to Cu²⁺ was 2:1, with a binding constant of 6.77 × 10² M^-1.
• L1-based indicator paper demonstrated a significant fluorescence response to Cu²⁺.

Conclusions:

• The TPE-modified strategy effectively overcomes ACQ limitations of curcumin, enhancing its utility in aqueous solutions.
• The developed L1 probe offers a sensitive and selective method for detecting Cu²⁺ ions.
• This approach provides a feasible pathway for designing other ACQ-based probes with improved detection capabilities.