One-pot synthesis of fluorescent non-conjugated polymer dots for Fe detection and temperature sensing.

The facile preparation of highly fluorescent polymer dots (PDs) still attracts substantial interest. Here, temperature/Fe dual-responsive PDs are synthesized under mild conditions via the amidation reaction and self-assembly between hyperbranched polyethyleneimine and 5-aminosalicylic acid. The prepared PDs display strong green fluorescence with quantum yield of 15.5% and 53.3% in water and dimethylsulfoxide, respectively. The PDs also possess unique features, including excellent solubility, solvent polarity-dependent emission, remarkable photostability, as well as good salt-tolerance. Interestingly, the fluorescence intensity of PDs exhibits a reversible and sensitive response to temperature within 20-65 °C, which renders the PDs useful as a thermometer probe. Importantly, Fe ion has the specific coordination ability toward the surface groups of PDs, leading to the aggregation and fluorescence quenching of PDs. Thus, the PDs are employed as a fluorescence probe for sensitive detecting Fe. The fluorescent intensity linearly decreases with increasing Fe from 2 to 60 μM. Besides, Fe concentration in river water samples is successfully assayed with this developed probe. The non-conjugated PDs with facile preparation, sensitive response to temperature and Fe may hold potential applications in environmental monitoring.