Photoreaction Boosting Phosphorescence Cascade Energy Transfer Based on Cucurbit[8]Uril Biaxial Polypseudorotaxane
Wen‐Wen Xing, Hui‐Juan Wang, Zhixue Liu, Zhen‐Hai Yu, Heng‐Yi Zhang, Yu Liu
Abstract
Abstract Cascade energy capturers based on supramolecular assembly have recently generated great research interest in the field of luminescent materials. Herein is reported a cucurbit[8]uril (CB[8])‐encapsulated coumarin‐bridged phenylpyridinium salt (G) to form biaxial polypseudorotaxane (G⊂CB[8]), which not only induces the phosphorescence of the guest G, but also activates the photodimerization of coumarin functional group in the CB[8] cavity (G‐dimer⊂CB[8]) to further boost its phosphorescence emission, extending the phosphorescence lifetime from 271.3 to 430.3 µs and the quantum yield from 5.1% to 25.7% in aqueous solution. After co‐assembly with amphiphilic calixarene (SC4AD), the supramolecular biaxial polypseudorotaxane G‐dimer⊂CB[8] is changed to the nanoparticle. Compared with the alone G‐dimer⊂CB[8], the phosphorescence intensity of G‐dimer⊂CB[8]@SC4AD is significantly enhanced with the phosphorescence lifetime extending to 2.11 ms. Subsequently, by doping commercial dye rhodamine B (RhB) in the G‐dimer⊂CB[8]@SC4AD assembly, an ultrahighly efficient phosphorescence‐harvesting energy transfer process occurs with an energy transfer efficiency (Φ ET ) of 72.3% and an antenna effect of 396.8. Furthermore, the cascaded room temperature phosphorescence harvesting system is constructed via introducing the secondary near‐infrared (NIR) acceptors Nile blue or Cy5 in the G‐dimer⊂CB[8]@SC4AD:RhB system, which possesses a good biocompatibility and is successfully applied to NIR delayed fluorescence targeted imaging in HeLa cell.