Self-exothermic redox reaction-driven green synthesis of fluorescent poly(dopamine) nanoparticles for rapid and visual detection of Fe3+

The development of fluorescent poly(dopamine) (PDA) nanoparticles have attracted considerable attention in the last few years, owing to their excellent physicochemical properties and good biocompatibility compared with fluorescent inorganic nanoparticles. Although great advances have been made to synthesize the fluorescent PDA nanoparticles (PDANPs), the development of a convenient and effective method for the large-scale synthesis of highly fluorescent PDANPs is still highly desirable. Herein, we first report a rapid, facile and green strategy for the large-scale synthesis of fluorescent PDANPs at room temperature via self-exothermic redox reaction. After a series of characterizations, it was established that the large amount of reaction heat generated by the redox reaction system composed of sodium periodate (SP) and sodium borohydride (NaBH4) could effectively accelerate the oxidation and polymerization rates of dopamine (DA), leading to the rapidly spontaneous formation of PDANPs within 1 min. The PDANPs prepared under the optimum conditions showed intense fluorescence (quantum yield, 6.3%) greater than that of previously reported fluorescent PDANPs, high production yield (about 21.0%), excellent water dispersibility and good photostability. Moreover, it was found that the fluorescence of PDANPs could be selectively quenched by Fe3+. After optimizing the sensing conditions, this method shows a wide linear ranged from 0.3 to 100 mu M, while the detection limit is 0.1 mu M. Furthermore, this fluorescent probe was successfully utilized for detecting Fe3+ in environmental water. Ultimately, the fluorescent PDANPs were further used for the preparation of fluorescent paper sensor to visually and semi-quantitatively detect Fe3+. Thus, the prepared PDANPs show great application potential for detecting Fe3+ in the fields of sensing and environmental monitoring.