A hybrid nanosensor based on novel fluorescent iron oxide nanoparticles for highly selective determination of Hg2+ ions in environmental samples

Abstract

Iron oxide nanoparticle-based chemosensors composed of fluorescent components have recently been examined as promising platforms for the separation, imaging, and, especially, determination of heavy metal ions. Among the heavy metal ions, Hg²⁺ has the most toxic effects and poses an important risk to the environment and living organisms due to its prevalence, widespread use, and tendency to accumulate. In response to the immediate necessity for the sensitive and selective determination of Hg²⁺ ions, novel fluorescent iron oxide nanoparticles (Py@Fe₂O₃) were systematically prepared via surface modification with pyrene base fluoroionophore groups via a click reaction. The novel Py@Fe₂O₃ and fluoroionophore were characterized structurally, morphologically and thermally using MALDI-TOF, ¹H, ¹³C NMR, UV-Vis, FTIR, SEM, TEM and TGA. The effects of the pH, buffer concentration, initial concentration of the sensor, photostability and measurement time on the relative fluorescence signal of Py@Fe₂O₃ were evaluated and optimized for “turn-off” determination of Hg²⁺. The LOD and LOQ were determined to be 3.650 nmol L⁻¹ and 10.960 nmol L⁻¹ in the linear working range of 0.010–1.000 μmol L⁻¹ Hg²⁺. These values were lower than the permissible limit for Hg²⁺ in drinking water set by the World Health Organization. ICP-MS and a spike/recovery test were carried out to evaluate the sensor accuracy, and the results demonstrated that the “turn-off” signal change of Py@Fe₂O₃ could be sensitively, easily, and selectively used for reliable quantification of Hg²⁺ in environmental samples.