Synthesis of functionalized mesoporous silica nanoparticles for colorimetric and fluorescence sensing of selective metal (Fe3+) ions in aqueous solution

Abstract

The fabrication of red fluorescent hybrid mesoporous silica-based nanosensor materials has promised the bioimaging and selective detection of toxic pollutants in aqueous solutions. In this study, we present a hybrid mesoporous silica nanosensor in which the propidium iodide (PI) was used to conveniently integrate into the mesopore walls using bis(trimethoxysilylpropyl silane) precursors. Various characterization techniques including X-ray diffraction (XRD), Fourier-transform infrared (FTIR), N₂ adsorption-desorption, zeta potential, particle size analysis, thermogravimetric, and UV-visible analysis were used to analyze the prepared materials. The prepared PI integrated mesoporous silica nanoparticles (PI-MSNs) selective metal ion sensing capabilities were tested with a variety of heavy metal ions (100 mM), including Ni²⁺, Cd²⁺, Co²⁺, Zn²⁺, Cr³⁺, Cu²⁺, Al³⁺, Mg²⁺, Hg²⁺ and Fe³⁺ ions. Among the investigated metal ions, the prepared PI-MSNs demonstrated selective monitoring of Fe³⁺ ions with a significant visible colorimetric pink color change into orange and quenching of pink fluorescence in an aqueous suspension. The selective sensing behavior of PI-MSNs might be due to the interaction of Fe³⁺ ions with the integrated PI functional fluorophore present in the mesopore walls. Therefore, we emphasize that the prepared PI-MSNs could be efficient for selective monitoring of Fe³⁺ ions in an aqueous solution and in the biological cellular microenvironment.

Keywords: Colorimetric sensor; Fe(3+) ion sensing; Mesoporous silica nanoparticles; Nanosensors; Recyclability.