Organic microbelt array based on hydrogen-bond architecture showing polarized fluorescence and two-photon emission

While organic micro/nanostructures for optoelectronic applications have attracted increasing recent attention, the assembly of aligned micro/nanostructure arrays continues to be a challenge. Herein, a one-dimensional (1D) microbelt has been fabricated by a hydrogen bonding assembly strategy with guanidinium cations and stilbene-based sulfonate anions as the building blocks. X-ray diffraction and high-resolution transmission electron microscopy demonstrate that the microbelt possesses a periodic layered structure with guanidinium cations and anionic stilbene-based chromophores regularly assembled within the microcrystal. The individual 1D microbelts show enhanced luminescent properties compared with pure stilbene-based units, with strong blue emission with a photoluminescent quantum yield of 46% and fluorescence lifetime of 2.8 ns, as well as well-defined polarized luminescence (an anisotropy value of 0.71). Moreover, a macroscopic 1D microbelt array can be fabricated by means of the spontaneous alignment of individual microbelts resulting from an evaporation-induced deposition process. The regularly oriented microbelt array maintains a uniform and highly polarized fluorescence and also exhibits both strong two-photon emission and an interesting second-harmonic response upon excitation with near-infrared laser pulses. Therefore, this work provides a procedure for the facile bottom-up self-assembly of highly ordered 1D organic microcrystal and microarray structures with high luminescent efficiency as well as polarized emission, which have potential applications in the areas of light displays, polarized thin films, frequency doubling materials and miniaturized optoelectronic devices.