Discovery of aggregation-induced emission luminogens (AIEgens) from orange peel

In recent years, aggregation-induced emission luminogens (AIEgens) have been widely developed for bio-imaging, theranostics, organic photoelectronics, and chemo/biosensors. While, the existing AIEgens are almost all obtained by organic synthesis, experiencing complicated synthesis routes, high cost, environmentally unfriendly, and poor biocompatibility. Therefore, exploration of AIEgens from natural products is an attractive alternative approach. In this contribution, two natural AIE-active materials, Tangeretin and Nobiletin, were found, which can be extracted from orange peel. Single crystal structure, fluorescence spectra and viscosity analyses verified that restriction of intramolecular rotation was responsible for the AIE phenomenon of Tangeretin and Nobiletin. The theoretical calculation results indicated that the intermolecular charge transfer (ICT) was related with the bathochromic-shift in the solid-state. Moreover, Tangeretin and Nobiletin were biocompatible and could selectively target lysosomes. In short, these natural products provided a new approach for obtaining new kinds of AIEgens, and showing great potential in bioimaging.