Highly crystallization-induced emissive luminophores with mechanoluminescent features for two-photon harvesting fluorescence imaging and latent fingerprint identification

Fluorescence imaging can be employed in fields of medical treatment, astronomical exploration, and national defense security. Traditional fluorescence imaging often takes the single-photon techniques, which is vulnerable to background interference and photobleaching. Remedially, two-photon fluorescence imaging can achieve much higher-resolution fluorescence imaging for reducing scattering and deeper depth. Hence, by assembling the tetraphenylethylene backbones with nontoxic and non-noble K⁺ ions, compound 1 ([(Hdma)K(H₂ettc)]_n, H₄ettc = 4',4''',4''''',4'''''''-(ethene-1,1,2,2-tetrayl)tetrakis(([1,1'-biphenyl]-4-carboxylic acid))) with the crystallization-induced emissions exhibited charming fluorescence imaging under two-photon excitation microscopy (TPEM). Besides, luminescent powders based on compound 1 can achieve high-resolution fingerprint recognition, providing secure access control and identification for a novel authentication method. Compared with the commercial fluorescent dyes coumarin-6, the as-synthesized compound 1 showed great solvent stability, indicating its durability against harsh environment. Moreover, compound 1 shows mechanoluminescent properties for the perturbation of weak supramolecular interactions within ordered arrangements of the H₂ettc²⁻ ligands. This novel compound has provided an important insight to the development of two-photon fluorescence imaging and advanced external-stimuli responsive materials.