Condensed state fluorescence switching of hexaarylbiimidazole-tetraphenylethene conjugate for super-resolution fluorescence nanolocalization

Abstract

This paper reported the synthesis of hexaarylbiimidazole- tetraphenylethene (HABI-TPE) conjugated photochromic fluorophore, which simultaneously exhibited photochromic property, condensed state enhanced emission and reversible fluorescence switching. Upon UV irradiation, a green species with a broad absorption band between 550 and 800 nm ( the absorption maximum at 697 nm ) was observed, which readily faded to colorless in the darkness. HABI-TPE launched strong fluorescence with the maximum emission wavelength at 520–580 nm under the excitation with 450–500 nm visible light in condensed state, which is in contrast to nonfluorescence in solution. The maximum emission wavelength in condensed state was dependent of excitation wavelength. More interestingly, HABI-TPE exhibited reversible fluorescence switching upon alternating irradiation with blue or near-UV light (wavelength less than 490 nm) and green light (more than 490 nm) in condensed state. Our evaluation demonstrated that HABI-TPE exhibited great photoswitchable fluorescence, which is a promising photoswitchable fluorophore for localization-based super-resolution microscopy, evidencing by resolving nanostructures with sub-100 nm resolution in polymethylmethacrylate films.