Sequence-Dependent DNA-Mediated Fluorescent Polydopamine Nanoparticles for Detection and Removal of Copper(II) ions

Although fluorescent polydopamine nanoparticles (F-PDA NPs) have shown great promise in a variety of fields, there are still some challenges involved with their application, such as low quantum yields, stability, and dispersion. Herein, the effects of the synthesis conditions and different sequences of DNA on the fluorescence intensity of F-PDA NPs were systematically investigated. The results demonstrated that DNA-mediated F-PDA NPs displayed excellent stability and dispersion. Specifically, polycytosine (poly-C) improved the fluorescence intensity of F-PDA NPs, with an optimal sequence of 10 continuous cytosines. Moreover, the F-PDA NPs showed an obvious selective response for Cu2+ but had no response for other metal ions. Based on this discovery, a method involving F-PDA/C10 NPs was designed for the sensitive detection and effective removal of Cu2+. The proposed method demonstrated great sensitivity for Cu2+ detection, with a detection limit of 0.03 μM, and was applied for the determination of Cu2+ in seawater. Through modification of a paper test strip, the method was also applied for Cu2+ detection in seawater. Furthermore, the starch film with F-PDA/C10 NPs displayed a high removal efficiency (≥99.41%) over a wide range of Cu2+ concentrations (20–300 μM). This study offers a chemically tailored approach based on F-PDA/C10 NPs for the simultaneous detection and removal of heavy metal ions.