Metal-Free Nanoarchitectonics of Fluorescent Transparent Materials via Co-Assembling Non-Aromatic Amino Acids and Tetrafluorophthalic Acid for Adhesion, Coating, and Information Encryption Applications.

Realizing fluorescence emission from non-aromatic amino acids is a difficult challenge in the development of optical materials in the absence of polymeric backbones and covalent cross-linkers. Herein, a non-covalent approach is used to fabricate a series of bulk glasses exhibiting strong fluorescence from non-aromatic amino acids (ʟ-arginine, ʟ-lysine, ʟ-proline, and ʟ-histidine) by co-assembling them with tetrafluorophthalic acid (FA). FA, amino acids, and non-covalent bonding between them play essential roles in both glass formation and fluorescent properties. The high viscosity and rapid annealing process of the glass formation process effectively prevent the crystallization and packing of FA and amino acids, slow the free internal rotations of the amino acids, and reduce the intermolecular collisions, thus increasing the fluorescence emissions of glasses. FA-amino acids glasses display high fluorescence quantum yields (> 44%) and large Stokes shifts. Their fluorescence performance is maintained even under various harsh conditions, including low temperatures, exposure to organic solvents, and coating with porous materials. Based on their robust anti-freezing adhesion capacity (4.77 MPa at -40°C, 3.30 MPa at -196°C) and long-term stable solid-state luminescence characteristics, these materials show great potential as fluorescent coatings and labeling agents suitable for use at low temperatures.