Rhodamine-Functionalized Nanosensor for Multimodal, Ultrasensitive, and Stable Detection of Toxic Mercury Ions

Nanoprobes are increasingly investigated for the ultrasensitive detection and monitoring of heavy metal pollutants. Mercury (II), a significant global threat to food safety and public health, has prompted the development of numerous probes. However, existing systems often fail to achieve nanomolar-level detection in aqueous environments. To address this critical challenge, we developed a self-assembled amphiphilic dual rhodamine B nanoprobe (DR) that forms stable nanospheres with an average size of 247.97 nm. This innovative nanosensor exhibits exceptional selectivity and dual-mode responsiveness in aqueous solution, characterized by a rapid 12-s "turn-on" fluorescence response accompanied by visible colorimetric changes. The nanosensor achieves an ultralow detection limit of 0.19 nm for Hg²⁺, outperforming most homologous detection systems. Its practical utility was validated across three complementary platforms: smartphone-based RGB analysis, hydrogel sensors, and paper-based test strips. The nanoprobe demonstrates robust performance in real-world applications, yielding recovery rates between 97.0% and 107.5% across diverse sample types, including agricultural products, soil, aquatic systems, and biological specimens (zebrafish larvae, plant tissues). By integrating cost-effective one-pot synthesis with ultra-sensitive detection and multi-modal platforms, this nanosensor offers a promising and effective solution for monitoring Hg²⁺ levels in diverse environmental and food safety scenarios.