A novel rhodamine chromone-based "Off-On" chemo sensor for the differential detection of Al(III) and Zn(II) in aqueous solutions

A new fluorescent probe, which contains rhodamine and chromone moieties, was designed and synthesized for selective recognition Al3+ and Zn2+. The sensor showed immediate responses toward Al3+ and Zn2+ in different systems. The sensor exhibited highly selective and sensitive "off-on" fluorescent responses toward Al3+ based on the ring-opening mechanism of the rhodamine spirolactam in an acetonitrile: water solution (excitation 500 nm and emission 550 nm). Whereas, in an ethanol:water solution, the sensor showed a significant fluorescent enhancement for Zn2+ over a wide range of tested metal ions (excitation 424 nm and emission 496 nm), due to chelation-enhanced fluorescence process generated along with the photoinduced electron transfer process suppressed simultaneously. Moreover, the prepared zinc complex of the sensor could detect Al3+ on the basis of fluorescence resonance energy transfer mechanism and the detection limit for Al3+ was as low as 1.83 x 10(-7) M. (C) 2014 Elsevier B.V. All rights reserved.