Alizarin Complexone as a highly selective ratiometric fluorescent probe for Al3+ detection in semi-aqueous solution

A simple and selective spectrofluorimetric method for the determination of trace levels of aluminum has been developed using Alizarin Complexone (AC). Exhibiting absorption and fluorescence changes in the presence of Al3+ in EtOH-H2O solution at pH 4.6, AC could be used as a colorimetric and fluorescent chemosensor for the detection of Al3+. In the presence of Al3+ ions, AC undergoes fluorescence quenching at 487 nm and shows the formation of a new red-shifted band at 558 nm. A good linear relationship could be obtained between the fluorescence intensity ratio (I-487/I-558) and the concentration of Al3+ ions in the range of 0.3-4.5 x 10(-5) M (R-2=0.9825). The intensity changes allow a ratiometric detection of Al3+ in acid semi-aqueous solution with the detection limit of 5.2 x 10(-7) M. Moreover, the colorimetric and fluorescent response of AC to Al3+ can be conveniently detected by the naked eye, which provides a facile method for visual detection of Al3+. The optimized ground state geometry and corresponding UV-vis absorption spectral characteristics of AC and AC-Al3+ complex have also been calculated using Density Functional Theory (DFT) with CEP-31G basis sets. (C) 2014 Elsevier B.V. All rights reserved.