Pure organic room temperature phosphorescence (RTP) has unique advantages and various potential applications. However, it is challengeable to achieve organic RTP under visible and near-infrared (NIR)-light excitation, especially in aqueous solution. Herein we assemble difluoroboron β-diketonate compounds to form organic nanoparticles (NPs) in water. The resulting NPs are able to show efficient RTP, effective uptake, and bright imaging of HeLa cells under both visible-and NIR-light excitation. More strikingly, spectroscopic study, single-crystal Xray diffraction, and DFT calculation reveal that the efficient RTP in organic NPs is originated from dimers in their excited states. The multiple interactions and intermolecular charge transfer in the dimer structures are of significance in promoting the production of dimer triplet excited states and suppressing the nonradiative decays to boost the RTP under visible-and NIR-light irradiation in water.

We report the first highly efficient artificial light-harvesting systems based on nanocrystals of difluoroboron chromophores to mimic the chlorosomes, one of the most efficient light-harvesting systems found in green photosynthetic bacteria. Uniform nanocrystals with controlled donor/acceptor ratios were prepared by simple coassembly of the donors and acceptors in water. The light-harvesting system funneled the excitation energy collected by a thousand donor chromophores to a single acceptor. The well-defined spatial organization of individual chromophores in the nanocrystals enabled an energy transfer efficiency of 95 %, even at a donor/acceptor ratio as high as 1000:1, and a significant fluorescence of the acceptor was observed up to donor/acceptor ratios of 200 000:1.

A carbazole-containing difluoroboron β-diketonate complex (BCZ), which shows strong fluorescence in both the solid state and in organic solutions, is reported. The crystalline materials of BCZ obtained from different solvents display different emission colors. Single-crystal analysis reveals that the enhanced overlap between adjacent molecules induces increased excited-state delocalization and is responsible for the variation of the emission colors from yellow to red. The emission colors of the materials are effectively tuned by external stimuli such as grinding, heating, and solvent vapor. The powder X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and 1 H NMR studies on materials of BCZ reveal that the thermochromic properties of BCZ are closely related to the removal of solvent molecules from the crystalline powders upon heating. Moreover, uniform 1D microstructures of BCZ obtained by solvent exchange in solution exhibit optical waveguide property with low optical loss.The ORCID identification number(s) for the author(s) of this article can be found under http://dx.