Polymorphism and anisotropy are fundamental phenomena of crystalline materials. However, the structure-dependent photoluminescent (PL) anisotropy in polymorphic organic crystals has remained unexplored.
Recently, a joint research team led by Prof. Yu-Wu Zhong, Yong Sheng Zhao, and Jiannian Yao at Institute of Chemistry, Chinese Academy of Sciences (CAS), demonstrated polymorphism-dependent photoluminescent anisotropy of organometallic nanostructures.
Two polymorphic nanocrystals, green-emitting nanorods (PtD-g) and yellow-emitting nanoplates (PtD-y), were obtained from a platinum(II)-diketonate complex. The PtD-y crystals display remarkable PL anisotropy with an anisotropy ratio of up to 0.87 whereas the PtD-g crystals are nearly unpolarized. The polarization properties are rationalized on the different molecular packing of these crystals. In addition, by light-harvesting energy transfer, the PtD-y crystals are successfully used to amplify the emission polarization of a red-emitting platinum acceptor (PtA) doped into the donor crystalline matrix, which is otherwise weakly polarized as pure crystals.
This work demonstrates that packing mode has a significant impact on the excited state and PL anisotropy properties of crystalline materials, suggesting the great potential of polymorphic nanostructures for applications in multifunctional nanophotonic devices.
This study entitled “Photoluminescent Anisotropy Amplification in Polymorphic Organic Nanocrystals by Light-Harvesting Energy Transfer” was recently published in Journal of the American Chemical Society (DOI: 10.1021/jacs.9b02055) and selected as the front cover of JACS (issue 17, 01-May-2019).
The research work was financially supported by National Natural Science Foundation of China, and the Strategic Priority Research Program of the Chinese Academy of Sciences.

Crystalline structure-dependent photoluminescent anisotropy and its amplification by energy transfer (Image by Prof. ZHONG Yu-Wu)

Contact:
Prof. ZHONG Yu-Wu
Institute of Chemistry, Chinese Academy of Sciences
Email: zhongyuwu@iccas.ac.cn