Synthesis of fluorescent naphthalimide functionalized Fe3O4 nanoparticles and their application for the selective detection of Zn2+ present in contaminated soil

Abstract

A fluorescent dopamine–naphthalimide–dipicolylamine (DPA) was synthesized as a sensing receptor for Zn2+. Naphthalimide-DPA (2) was immobilized onto the surface of iron oxide nanoparticle to prepare a hybrid nanomagnet 1-Fe3O4 for the purpose of selective detection of Zn2+ in soil. Naphthalimide–DPA (2) and 1-Fe3O4 were observed to bind with Zn2+, leading to significant increase in fluorescence intensity at 527 nm. The fluorescence increases of 2 (10 μM) and 1-Fe3O4 (0.33 wt%) by addition of Zn2+ were linear over the [Zn2+] range of 0–7 μM and 0–20 μM, respectively. These fluorescence changes were highly selective for Zn2+, which were readily monitored even in the presence of other competitive cations. In particular, 1-Fe3O4 exhibited an excellent limit of detection determined to be 0.0345 ppb. Furthermore, this system was found to be suitable for detecting Zn2+ in a wide pH range of 3–11 and could be reused with the addition of ethylenediaminetetraacetic acid (EDTA). Moreover, nanomagnet 1-Fe3O4 was employed for the selective detection and removal of Zn2+ from a soil sample. These results confirm that the use of 1-Fe3O4 is a novel and simple method for detecting Zn2+ in environmental samples.