Luminescent Naphthalene Diimide-Based Peptide in Aqueous Medium and in Solid State: Rewritable Fluorescent Color Code

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Biophysical Chemistry

Background:

• Naphthalene diimide (NDI)-based compounds are known for their electronic properties.
• Self-assembly of peptides into functional aggregates is a growing area of research.
• Fluorescent materials with tunable properties are sought for advanced applications.

Purpose of the Study:

• To demonstrate the self-assembly of an NDI-appended peptide into a fluorescent J-aggregate in aqueous media.
• To characterize the self-assembled structure and its photophysical properties.
• To investigate the potential of this system for information encryption and security applications.

Main Methods:

• Transmission Electron Microscopy (TEM) for morphology.
• Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) for structural analysis.
• Time-Correlated Single Photon Counting (TCSPC), UV-Vis, and Photoluminescence spectroscopy for photophysical characterization.

Main Results:

• A unique self-assembly of an NDI-appended peptide into a fluorescent J-aggregate was observed in aqueous solution.
• The aggregated species exhibited cross-linked nanofibrillar morphology and enhanced fluorescence lifetime.
• The fluorescence was pH-dependent, showing reversible erasing and rewriting, with alkali erasing and acid rewriting the signal.

Conclusions:

• The NDI-appended peptide self-assembles into a functional J-aggregate with unique photophysical properties in water.
• The reversible, pH-dependent fluorescence switching suggests potential for rewritable optical data storage and security features.
• This system offers a novel platform for developing advanced fluorescent materials for encryption and authentication.