Rhodamine 6G hydrazone bearing thiophene unit: A highly sensitive and selective off–on fluorescent chemosensor for Al3+

• A new rhodamine-based fluorescent “off-on” probe for Al3+ has been developed.
• The probe shows a high sensitivity and selectivity for Al3+.
• Response of probe to Al3+ is a cation-catalyzed reaction.
• The probe has been used for monitoring Al3+ in drinking water.

A rhodamine derivative (R1) has been synthesized by a hydrazone formation of rhodamine 6G hydrazide with 3-methylthiophene-2-carbaldehyde, which exhibits high selectivity and sensitivity as an “off–on” fluorescent sensor toward Al3+ in water containing media. The binding process was confirmed by UV–vis absorption, fluorescence measurements, mass spectroscopy and DFT calculation. The probe functions by Al3+ induced hydrolytic cleavage of the imine-bond to produce an intense rhodamine-based emission. To test the practical use of the probe, the determination of Al3+ in real water samples was also evaluated.

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