A novel rhodamine-based dual-mode fluorogenic probe for sensitive determination of Hg²⁺

Mercury ions (Hg2+) are highly toxic and persistent heavy metal pollutants that pose serious threats to environmental systems and human health. Therefore, developing sensitive and selective detection strategies for Hg2+ is of great significance. In this study, a rhodamine-based dual-mode fluorescent probe (RB-HG) was developed utilizing dimethylthiocarbamate groups as recognition sites. Upon undergoing specific interaction with Hg²⁺, leading to the dissociation of the C-O bond and subsequently triggering an opening-ring reaction to form a ketone structure (RB-C=O), thereby activating the intramolecular charge transfer (ICT) process and generating both fluorescence and colorimetric signals, thereby activating both colorimetric and fluorescence dual - channel signals. In vitro experiments demonstrate that RB-HG (5.0 μM) exhibits high selectivity and sensitivity toward Hg²⁺. The limits of detection for the fluorescence and colorimetric detection modes are 1.16 μM and 3.22 μM, respectively. RB-HG was successfully applied to detect Hg2+ in food samples with excellent recovery rates and to image exogenous Hg2+ in living cells, highlighting its potential for food monitoring and bioimaging applications.