A conjugated oligoelectrolyte for the recognition of uranyl ion in aqueous and soil samples via RGB method

Abstract

The development of selective and practically applicable sensors for monitoring trace uranyl ions (UO₂²⁺) in an aqueous medium is the biggest challenge. This study presents the development of a conjugated oligoelectrolyte-based probe (COE) for the selective detection of UO₂²⁺ ions in water bodies. The COE is a water-soluble probe having an organic backbone with two ionic pendants at the terminal points. It changes its color to a dark yellow selectively in the presence of UO₂²⁺ ions. This visible change was integrated with a smartphone RGB color quantification method. The COE displayed an RGB chemo-dosimeter to selectively monitor UO₂²⁺ ions without interference from other metal ions. In the parallel experiment, COE displays a spectrofluorimetric emission signal at λ_ems. = 525 nm (with λ_exc. = 420 nm), which exhibits quenching of signal when interacted with UO₂²⁺ ions. The limit of detection (LOD) is found to be 3.07 × 10⁻² µM and 4.50 µM by spectrofluorimetric and RGB color value methods, respectively. ¹H NMR and XPS analysis investigated the mode of interaction, and it suggested that the quenching of the emission signal was due to the interaction between the electron-rich azomethine site of COE and UO₂²⁺ ion. The smartphone-based RGB color analysis makes COE a potential probe with reduced operation time and offers a fresh approach for the immediate, real-time detection of UO₂²⁺ ions in aqueous and soil samples.