Rhodamine-Triazole Functionalized Fe3O4@SiO2 Nanoparticles as Fluorescent Sensors for Heavy Metal Ions

Abstract

Rhodamine-triazole sensor functionalized Fe3O4@SiO2 nanoparticles were developed for the detection of heavy metal ions, namely Cu2+, Ni2+, Hg2+, Co2+, Fe3+, and Pb2+. Rhodamine conjugated with a triazole moiety (RBT) was utilized as the metal ion binding site. The RBT-Fe3O4@SiO2 nanoparticles were fully characterized by XRD, FTIR, TGA, SEM and TEM techniques. Additionally, RBT-functionalized Fe3O4@SiO2 nanoparticles can be separated from the aqueous phase by application of an external magnet, leading to clear naked-eye observation of the color changes and fluorescence enhancement. From UV-Vis absorption spectra, aqueous solutions of RBT-Fe3O4@SiO2 in the presence of heavy metal ions show an absorption peak at 554 nm. Fluorescence titration experiments reveal that the intensity of the fluorescence emission band at 574 nm is linearly dependent on Cu2+ concentration, over a 100-800 µM range. Furthermore, complexation of Cu2+ by RBT-Fe3O4@SiO2 nanoparticles can induce ring-opening of the rhodamine spirolactam ring followed by hydrolysis, confirmed by mass spectrometry.

Fluorescent Composite Nano‐ and Microparticles Based on Xanthene Dyes and Iron Oxides

“…The MPs were prepared by sonochemical method [70], coprecipitation [71], and thermal decomposition of iron acetyl acetonate [55]. The Fe 3 O 4 nanoparticles had different average diameters, for example, about 10 nm with a rough surface and SiO 2 shell thickness of about 90 nm [72] or spherical with a diameter of about 67 nm [73].…”

“…Fe 3 O 4 @SiO 2 nanoparticles were functionalized with 3‐azidopropyltriethoxysilane and rhodamine‐N‐propargylalkyne in the presence of copper compound [73]. 3‐Azidopropyltriethoxysilane was prepared by the reaction of sodium azide and 3‐chloropropyltriethoxysilane in DMF.…”