Highly Emissive Nanoparticles Based on AIE-Active Molecule and PAMAM Dendritic “Molecular Glue”

The highly emissive nanoparticles Gn-TCMPE (n = 0–4) were prepared by using PAMAM dendrimers as “molecular glue” to adhere an AIE-active molecule tetra­(4-(carboxymethoxy)­phenyl)­ethylene (TCMPE). The electrostatic interaction of ammonium–carboxylate ion pairs provides a driving force between TCMPE and PAMAM dendrimers to form the nanoparticles Gn-TCMPE (n = 0–4), which is validated by the FTIR and 1H NMR spectra. The formation of nanoparticles dramatically blocks the nonradiative pathway and enhances the fluorescence of TCMPE. The quantum yields of Gn-TCMPE gradually boost at first and then reach to a plateau with increasing the generation of PAMAM dendrimers, and the highest absolute quantum yields are obtained to be 0.42 and 0.64 for Gn-TCMPE (n = 2–4) in methanol dispersion and solid phases, respectively. The fluorescence of the nanoparticles can be tuned by addition of trifluoroacetic acid (TFA). Furthermore, the G4-TCMPE has been successfully applied to selectively image cytoplasm of Hela cells with excellent photostability and low cytotoxicity. This study provides a novel noncovalent strategy for developing highly emissive and robust organic materials fitting for cell fluorescence imaging.