New fluorescent and colorimetric chemosensors based on the rhodamine detection of Hg2+ and Al3+ and application of imaging in living cells

Employing the “Off–On” switching of the spirocyclic moiety in Rhodamine B derivatives, three sensors were designed and characterized as new fluorescent probes for detecting Hg2+ and Al3+ in the environment, respectively. The first probe exhibited chromogenic and fluorogenic selectivity to detection of Hg2+ in methanol-H2O (4:6, v/v, HEPES, pH 7.0). The first and second probes displayed fluorescence intensity enhancement following Hg2+ coordination with limits of detection for Hg2+ at the ppb level. The limit of detection based on 3 blank/k was calculated to be 2.5 × 10−8 M and 4.2 × 10−8 M, respectively. The third probe contained a benzyl group which resulted in better selectivity for Al3+. Job's plot clearly suggested the formation of 1:1 complexation behavior between the three probes and Hg2+ or Al3+. The three probes can be used as a fluorescent probe for monitoring Hg2+ or Al3+ in living cells with satisfying results, which demonstrates the value of the probes in practical applications in environmental and biological systems.

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► Three new sensors were designed and characterized.
► Two of these probes can be used as efficient fluorescent probes for detecting Hg2+.
► Their recognizing behavior toward Hg2+ has been investigated.
► The third probe bearing a benzyl group has good selectivity for Al3+.
► The probes have been successfully used for the detection of Hg2+ in the living cells.