Polymorphism and reversible mechanochromic luminescence for solid-state difluoroboron avobenzone

Area of Science:

• Materials Science
• Photophysics
• Supramolecular Chemistry

Background:

• Commercial sunscreens contain UV absorbers like avobenzone.
• Boron complexes can exhibit unique photophysical properties.
• Mechanochromic materials change color in response to mechanical stimuli.

Purpose of the Study:

• To investigate the solid-state luminescence properties of difluoroboron avobenzone (BF(2)AVB).
• To explore the mechanochromic behavior of BF(2)AVB films.
• To assess the potential of BF(2)AVB as a rewritable ink.

Main Methods:

• Synthesis of difluoroboron avobenzone (BF(2)AVB).
• Fabrication of thin films of BF(2)AVB.
• Mechanical stimulation (scratching, smearing, touching) of the films.
• UV-Vis absorption and fluorescence spectroscopy.
• Temperature-dependent fluorescence recovery studies.

Main Results:

• BF(2)AVB exhibits morphology-dependent emission in the solid state.
• Mechanical stress induces a significant red-shift in the emission color of BF(2)AVB films under UV excitation.
• The mechanochromic effect is reversible, with fluorescence recovery occurring slowly at room temperature or rapidly upon heating.
• Demonstrated potential as a rewritable "scratch the surface" ink.

Conclusions:

• BF(2)AVB possesses unique mechanochromic luminescence properties.
• The reversible color change upon mechanical stress and subsequent recovery offers potential for novel applications.
• BF(2)AVB can be utilized as a rewritable ink with potential commercial value.