Force-triggered hypso- and bathochromic bidirectional fluorescence switching beyond 120 nm and its anticounterfeiting...

Area of Science:

• Materials Science
• Organic Chemistry
• Photophysics

Background:

• Developing single-component molecules for tunable emission via external stimuli is crucial for advanced optical materials.
• Aggregation-induced emission (AIE) luminogens offer unique photophysical properties, but controlled multi-color switching remains a challenge.
• Mechanofluorochromism, the change in fluorescence upon mechanical force, provides a pathway for external stimulus-responsive materials.

Purpose of the Study:

• To design and synthesize a novel aggregation-induced emission (AIE) luminogen capable of high-contrast, tricolor emissive regulation.
• To investigate the mechanofluorochromic properties of the AIE luminogen in response to anisotropic mechanical grinding.
• To explore the potential applications of this material in information anticounterfeiting systems.

Main Methods:

• Synthesis of a symmetric acceptor-donor-acceptor (A-D-A) type AIE luminogen.
• Anisotropic mechanical grinding applied to the solid-state luminogen to induce morphological changes.
• Spectroscopic analysis (fluorescence emission spectra) to quantify color changes (hypsochromic and bathochromic shifts).
• Morphological characterization to understand the solid-state transformations.

Main Results:

• The A-D-A luminogen exhibited sequential, high-contrast fluorescence switching upon mechanical grinding.
• Light grinding induced an orange-yellow-to-blue hypsochromic shift (Δλ_em,max = 122 nm).
• Vigorous grinding resulted in a blue-to-red bathochromic shift (Δλ_em,max = 185 nm), demonstrating simultaneous wide-range mechanochromism.
• The observed tricolored phenomenon is attributed to distinct crystalline-to-crystalline and crystalline-to-amorphous morphological transitions.
• Three distinct information anticounterfeiting systems were successfully developed using this luminogen.

Conclusions:

• A single-component AIE luminogen was successfully developed, enabling simultaneous wide-range hypso- and bathochromic fluorescence mechanochromisms.
• The material demonstrates controllable tricolor emission switching solely through mechanical grinding, attributed to morphological changes.
• The developed luminogen shows significant promise for practical applications, particularly in advanced information anticounterfeiting technologies.