Highly sensitive and selective turn-on fluorescent chemodosimeter for Hg2+ based on thiorhodamine 6G-amide and its applications for biological imaging

• Highly sensitive and selective recognition toward Hg2+ in nearly neutral conditions.
• Hg2+-induced desulfurisation reaction.
• Detecting Hg2+ in living cells through biological imaging.

An easily available novel fluorescent chemodosimeter based on thiorhodamine 6G-amide has been synthesized and displayed highly selective and sensitive Hg2+-amplified fluorescence emission and absorbance above 500 nm in aqueous solution with a broad pH range 6–10. The mechanism for the high selectivity of the probe to Hg2+ has never been reported, which is the Hg2+-induced desulfurization reaction and spirolactam opening of rhodamine. This sensor was applied for biological imaging to confirm that it can be used as a fluorescent probe for monitoring Hg2+ in living cells with satisfying results, which further demonstrates its value of practical applications in environmental and biological systems.