Design of surface-imprinted ratiometric fluorescent materials for rapid and visual on-site detection of copper ions

Abstract

A core-shell structured mesoporous ion-imprinted ratiometric fluorescent sensor (CdTe@SiO₂@CDs-MIIPs) was constructed for the visual and quantitative detection of Cu²⁺. The sensor integrates red-emitting CdTe quantum dots as an internal reference and blue-emitting carbon dots as a responsive signal within a mesoporous imprinted layer, enabling ratiometric fluorescence detection with enhanced sensitivity, selectivity, and visual distinguishability. Under optimized conditions, the system exhibited a linear response in the 200–1000 nM range, with a detection limit of 54.53 nM and a rapid response time of 4 min. To eliminate reliance on bulky analytical instruments, a smartphone-assisted RGB analysis method was introduced, enabling direct image-based quantification of fluorescence signals. The RGB-derived results were consistent with those obtained using a fluorescence spectrophotometer, demonstrating the potential of this sensor platform for on-site, instrument-free monitoring of Cu²⁺ in complex environments.