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Reducing aggregation caused quenching effect through co-assembly of PAH chromophores and molecular barriers
摘要： The features of well-conjugated and planar aromatic structures make π-conjugated luminescent materials suffer from aggregation caused quenching (ACQ) effect when used in solid or aggregated states, which greatly impedes their applications in optoelectronic devices and biological applications. Herein, we reduce the ACQ effect by demonstrating a facile and low cost method to co-assemble polycyclic aromatic hydrocarbon (PAH) chromophores and octafluoronaphthalene together. Significantly, the solid photoluminescence quantum yield (PLQYs) for the as-resulted four micro/nanococrystals are enhanced by 254%, 235%, 474 and 582%, respectively. Protection from hydrophilic polymer chains (P123 (PEO20-PPO70-PEO20)) endows the cocrystals with superb dispersibility in water. More importantly, profiting from the above-mentioned highly improved properties, nano-cocrystals present good biocompatibility and considerable cell imaging performance. This research provides a simple method to enhance the emission, biocompatibility and cellular permeability of common chromophores, which may open more avenues for the applications of originally non- or poor fluorescent PAHs.
关键词： cocrystals,aggregation caused quenching,bioimaging,polycyclic aromatic hydrocarbon,photoluminescence quantum yield
更新于2025-09-23 15:23:52
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Morphology‐Dependent Luminescence and Optical Waveguide Property in Large‐Size Organic Charge Transfer Cocrystals with Anisotropic Spatial Distribution of Transition Dipole Moment
摘要： Organic cocrystals exhibiting active optical waveguide behaviors are strongly related to the total internal reflection, molecule stacking modes, and the spatial distribution of transition dipole moment (μ) in crystals. However, organic charge transfer (CT) cocrystals as new materials that exhibit optical waveguide property responses to anisotropic spatial distribution of μ are still unknown. Herein, prepared is a novel organic CT cocrystal 9AC-TCNB (9AC = 9-anthracene carboxylic acid, TCNB = 1,2,4,5-tetracyanobenzene) with a mixed stacking structure of donor (D) and acceptor (A) along two different orientations on the same lattice plane. According to various spectroscopic analyses, two direction-oriented asymmetric light propagate in the cocrystal derived from the anisotropic spatial distribution of μ have been confirmed. Photo luminescence (PL) microscopic images and spatial resolution PL spectra of 1D and 2D 9AC-TCNB cocrystals further demonstrate that the CT cocrystals possess morphology and color-dependent optical waveguide properties with anisotropy, which confirms the principle theory of light propagation. This result can open new potential applications of organic cocrystals in large-scale optical waveguide devices and integrated optics.
关键词： large-size organic cocrystals,charge transfer,optical waveguide,transition dipole moment
更新于2025-09-12 10:27:22
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Ultralong Organic Phosphorescence in the Solid State: the Case of Triphenylene Cocrystals with Halo- and Dihalo-penta/tetrafluorobenzene
摘要： The polycyclic aromatic hydrocarbon (PAH) triphenylene (TP) has been reacted with halo-pentafluorobenzene (XF5, X = Br, I) and 1,4-dihalo-tetrafluorobenzene (X2F4, X = Br, I) to yield the corresponding cocrystals TP·BrF5, TP·Br2F4, TP·IF5, and TP·I2F4 form I. These materials have been synthesized by dissolving TP into an excess of liquid or molten co-former, and single crystals have been grown via seeding chloroform solutions. They have been fully characterized by a combination of techniques including X-ray diffraction, Raman, and luminescence spectroscopy in the solid state. TP·I2F4 form I was found to undergo a single-crystal to single-crystal (SCSC) polymorphic phase transition induced by temperature (when cooled down to 100K) leading to the new form TP·I2F4 form II, which is transformed back into the first structure when brought again at RT. This behavior was confirmed also by Raman spectroscopy. Upon cocrystallization and as a result of the external heavy atom effect, all crystalline materials exhibited bright room temperature phosphorescence clearly visible by naked eye. The latter was almost exclusive for cocrystal TP·I2F4, whereas for TP·Br2F4 both fluorescence and phosphorescence were detected. In TP·Br2F4, the phosphorescence lifetime was of the order of 200 ms, and with the visual outcome of an orange phosphorescence lasting for a couple of seconds upon ceasing the excitation, that makes this compound classifiable as an Ultralong Organic Phosphorescent (UOP) material. The results evidenced the role of the nature of the heavy atom in governing the phosphorescence output from organic cocrystals.
关键词： Room Temperature Phosphorescence,Triphenylene Cocrystals,Ultralong Organic Phosphorescence,Dihalo-tetrafluorobenzene,Halo-pentafluorobenzene
更新于2025-09-09 09:28:46