A ratiometric and colorimetric probe for detecting Hg(2+) based on naphthalimide–rhodamine and its staining function in cell imaging

In this work, a rhodamine derivative was developed as a colorimetric and ratiometric fluorescent probe for Hg(2+). It exhibited a highly sensitive fluorescence response toward Hg(2+). Importantly, studies revealed that the probe could be used for ratiometric detection of Hg(2+), with a low detection limit of 0.679 μM. The mechanism of Hg(2+) detection using compound 1 was confirmed by ESI-MS, (1)H NMR, and HPLC. Upon the addition of Hg(2+), the rhodamine receptor was induced to be in the ring-opening form via an Hg(2+)-promoted hydrolysis of rhodamine hydrazide to rhodamine acid. In addition to Hg(2+) detection, the naphthalimide–rhodamine compound was proven to be effective in cell imaging.