Incorporating silicon-doped carbon dots into europium chelated silica microspheres for the ratiometric fluorescent and colorimetric detection of Fe3+ ions

Abstract

In this study, a novel hybrid luminescent microsphere, Si-CDs@SiO₂-Eu was designed and successfully synthesized by encapsulating blue-emitting silicon-doped carbon quantum dots (Si-CDs) into carboxyl-modified SiO₂ microsphere and coordinating with Eu³⁺ ions. The SiO₂ matrix provides a stable dispersion environment for Si-CDs and serves as an effective platform for anchoring Eu³⁺ on the surface of microsphere, thereby realizing the spatial isolation and establishing dual-emission characteristic. The dual-emission microspheres can be served as a ratiometric fluorescent probe for the detection of Fe³⁺ in water with the red emission of Eu³⁺ ion as response and the blue emission of Si-CDs as reference. It displays high selectivity and sensitivity for Fe³⁺ with a detection limit of 1.41 μM. It is worth noting that an easy-to-differentiate color change for visual detection is also observed. In addition, the luminescence quenching mechanism study reveals that absorption competition quenching (ACQ) mechanism and cation exchange cause luminescence quenching at 617 nm, but have little effect at 400 nm, thus realizing the fluorescent ratiometric detection of Fe³⁺. Si-CDs@SiO₂-Eu functions as a dual-mode probe that integrates ratiometric (quantitative) and colorimetric (qualitative) detection, enabling real-time monitoring of Fe³⁺ and enhancing detection reliability.