Modified Rhodamine B Immobilized on Silica Nanoparticles (MRB@SiNPs) as a Fluorescent Probe for Selective Metal Ion Detection

Abstract

Rhodamine derivatives have demonstrated efficacy as chemosensory probes for the selective and sensitive detection of various metal ions in solution, primarily within aqueous-organic media, where the interaction between the probe and metal ion is conveyed through a signaling module. This study developed a highly sensitive and selective fluorescent probe based on modified Rhodamine B Immobilized on Silica Nanoparticles (MRB@SiNPs) for Fe³⁺ ion detection in a “turn-on” system. The spiro-lactam ring opening upon Fe³⁺ complexation triggered enhancements in absorption and fluorescence spectra, accompanied by a color change. This indicates the structure-function relationship of signaling expressions, which influences selectivity, sensitivity, interaction affinity, response time, reversibility, and other parameters essential for effective detection. Furthermore, the probe’s optical response was impacted by pH and chelation time, where a reduction in pH and longer interaction with Fe³⁺ enhanced both absorbance and fluorescence intensity. The detection limit was calculated at 0.0496 μM, and the probe showed good efficiency for reversibility. These characteristics highlight the potential of MRB@SiNPs as a promising platform for Fe³⁺ detection, offering real-time, highly sensitive, and visually perceptible detection capabilities for environmental and analytical applications.