Unprecedented Multicolor Photoluminescence from Hyperbranched Poly(amino ester)s

A novel kind of water-soluble fluorescent hyperbranched poly(amino ester) (PAE) is prepared through a one-pot polycondensation reaction of citric acid (CA) and N-methyldiethanolamine (NMDEA). The PAE exhibits enhanced and red-shift fluorescence with increasing solution concentration, showing distinct aggregation-induced emission character. Interestingly, the resulting PAE exhibits tunable photoluminescence from blue, cyan, and green to red irradiated by altering the excitation wavelengths. Such unique emission of non-conjugated PAE is attributed to the clustering of ester and tertiary amine groups derived from PAE self-assembly aggregates. Moreover, the fluorescence of PAE is very sensitive to Fe³⁺ ions. The facile preparation and unique optical features make PAE potentially useful in numerous applications such as multicolor cellular imaging, Fe³⁺ ions probe, and light-emitting diodes.