Journal of Materials Science, Vol.51, No.6, 3191-3199, 2016
Morphology and photophysical properties of dual-emissive hyperbranched zinc phthalocyanines and their self-assembling superstructures
Hyperbranched zinc phthalocyanines (HBZnPCs) showing dual-emissive fluorescence in N, N-dimethylformamide (DMF) solution were synthesized via a facile one-step cycloaddition of conjugated bisphthalonitrile precursors. The chemical, crystalline structures, surface morphology, and photophysical properties of synthesized HBZnPCs for different reaction times were systematically studied. It was found that HBZnPCs synthesized for 4 h exhibit the strongest dual fluorescent emission at similar to 440 and 690 nm in DMF, respectively, when excited at 365 nm, and micrometer scale sheet-like morphology was obtained in this case. In addition, the fluorescent emission of HBZnPCs dramatically changed in different solvents: the red emission was amplified in solvent of strong polarity, while blue emission dominated in non-co-ordinated solvent. More interestingly, we found for the first time that the fluorescence of initially "dark" H-aggregates of HBZnPCs in DMF/H2O mixed solvent was gradually recovered through self-assembling driven by the poor solvent, leading to a strong emission around 460 nm, which contributed to the formation of stable J-type superstructures.