Photoswitchable aggregation-induced emission of a dithienylethene-tetraphenylethene conjugate for optical memory and super-resolution imaging

We report the synthesis of a dithienylethene-tetraphenylethene (DTE-TPE) conjugated photochromic fluorophore which simultaneously exhibits aggregation-induced emission and reversible fluorescence switching. Photochromic DTE-TPE turns cyan-blue after 5 s of UV irradiation and exhibits a strong green emission at 520-540 nm upon excitation with visible light when present in nanoparticles and the solid state, in contrast to non-fluorescence in solution. DTE-TPE exhibits reversible fluorescence switching under alternating irradiation with UV and visible light (wavelengths greater than 440 nm), when present in nanoparticles and the solid state. The continuous readout of the emissive DTE-TPE film over 1 h upon 440 nm excitation-irradiation causes only a 7% reduction in emission intensity for DTE-TPE. The super-resolution fluorescence nanolocalization indicates that the vicinal DTE-TPE emitters show sub-100 nm resolution which is higher than for conventional fluorescent imaging. The spectroscopic and imaging data provides initial guidelines for the screening of molecular scale memory units with the corresponding excitation and detection wavelengths for signal readout and super-resolution imaging agents.