Solvent- and Light-Sensitive AIEE-Active Azo Dye: From Spherical to 1D and 2D Assemblies
Mina Han1, Ikue Abe2, Jihun Oh3
1Department of Chemistry Education, Kongju National University, Gongju 32588, Korea.
International Journal of Molecular Sciences
|January 21, 2022
Summary
Researchers explored how solvent polarity affects the structure and fluorescence of a novel azo dye. This understanding is key for developing new stimuli-responsive fluorescent materials.
Area of Science:
- Materials Science
- Supramolecular Chemistry
- Organic Chemistry
Background:
- Stimuli-responsive materials are crucial for advanced optical, electronic, and sensing applications.
- Understanding the interplay between molecular structure, solvent, and self-assembly is vital for designing functional nanomaterials.
Purpose of the Study:
- To investigate the relationship between solvent polarity, molecular structure, spectroscopic properties, and self-assembly of a sterically hindered triangular azo dye (3Bu).
- To explore the formation of diverse nano-, micro-, and macrostructures influenced by solvent environment and concentration.
- To demonstrate reversible fluorescence switching and morphological restoration in the self-assembled dye structures.
Main Methods:
- Synthesis and characterization of a sterically crowded triangular azo dye (3Bu).
- Solvent-dependent spectroscopic analysis (UV-Vis absorption, fluorescence) in N,N-dimethylformamide (DMF), tetrahydrofuran (THF), and toluene.
- Microscopy techniques (e.g., SEM, TEM) to observe self-assembled structures (nanoparticles, 1D fibers, 2D sheets).
- Investigation of stimuli-responsive behavior (solvent vapor, light irradiation) and fluorescence switching.
Main Results:
- The azo dye exhibited distinct color changes (yellow to pink-red) and spectroscopic features based on solvent polarity, correlating with molecular conformation (twisted azo vs. planar keto-hydrazone).
- Self-assembled structures ranged from nanoparticles to 1D sticks/fibers in DMF and 1D micro/millimeter structures in toluene, controlled by concentration and solvent.
- Two-dimensional (2D) sheets were formed from stacked fibers in THF-H2O mixtures at low temperatures.
- Reversible fluorescence switching (off↔on) and morphological recovery were achieved upon exposure to solvent vapor after visible light irradiation.
Conclusions:
- Solvent polarity significantly dictates the molecular conformation, aggregation behavior, and resulting morphology of the azo dye.
- The study highlights the potential of rational dye design and solvent selection for creating tunable, reusable fluorescent materials.
- The observed stimuli-responsive properties, including reversible fluorescence switching, offer promising avenues for advanced sensor and smart material development.
