Novel Stimuli-Responsive Spiropyran-Based Switch@HOFs Materials Enable Dynamic Anticounterfeiting.

Area of Science:

• Materials Science
• Organic Chemistry
• Nanotechnology

Background:

• Developing advanced smart fluorescent materials for encrypted messaging is challenging.
• Photochromic molecules like spiropyran (SP) offer potential for dynamic displays.
• Integrating SP into solid-state frameworks is crucial for stability and functionality.

Purpose of the Study:

• To create a novel composite material for dynamic, encrypted fluorescent messaging.
• To investigate the reversible switching of spiropyran within hydrogen-bonded organic frameworks (HOFs).
• To enhance the material's flexibility and mechanical properties for practical applications.

Main Methods:

• Combining spiropyran (SP) with hydrogen-bonded organic frameworks (HOFs).
• Utilizing fluorescence resonance energy transfer (FRET) between HOFs and the merocyanine (MC) isomer.
• Doping the composite with polydimethylsiloxane (PDMS) to create flexible membranes.

Main Results:

• Achieved reversible fluorescence switching (yellow-green to orange to red) with extended UV irradiation.
• Developed free-standing, flexible membranes with high mechanical strength, capable of repeated bending (>90°).
• Demonstrated significantly improved fatigue resistance (>100 cycles) for SP⊂HOF/PDMS compared to SP/PDMS (≤5 cycles).

Conclusions:

• The HOFs are crucial for enhancing the stability and recyclability of spiropyran-based fluorescent materials.
• This composite system enables dynamic fluorescence emission and visible color changes controlled by UV light.
• The material facilitates dynamic information display and decryption, advancing encrypted messaging capabilities.