One-dimensional self-assembly of π-conjugated fluorophore as pH probe highlight

One-dimensional self-assembled microwires of π-conjugated chromophore 1,2,4,5-tetrakis(4-pyridylvinyl)benzene (TKPVB) were successfully fabricated by a simple reprecipitation method. The structure, morphology and photophysical properties of the TKPVB microwires were investigated in details by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier Transform Infrared (FTIR) spectroscopy, selected area electron diffraction (SAED), fluorescence microscopy (FM), UV–vis spectroscopy and fluorescence spectroscopy. The crystal structure and FT-IR spectra revealed that the intermolecular hydrogen bonds and the π–π interaction between benzene ring of TKPVB molecules led to the head to tail molecular packing conformation (J-aggregate), which in turn helps forming microwires during the self-assembly process. Compared with isolated molecules in solution, the redshifted emission together with superradiant behavior observed in the microwires was due to the ordered molecular arrangement. Different emission wavelength of these microwires was observed at acidic (such as pH 3.6 and 4.8) and neutral conditions (such as pH 7.0), which made them good candidates for the detection of acidic compartments in living cells.