We report a versatile optical sensor by incorporating the indicator dye 4-phenyl-2,6-bis(2,3,5,6-tetrahydrobenzo[b][1,4,7]trioxononin-9-yl)pyryl ium perchlorate into a sol-gel layer. The proposed optical sensor that is stable, fast and highly selective to Hg2+ ions shows a significant absorbance signal change on exposure to an aqueous solution containing mercury(II) ion. The sensing film is able to determine mercury(II) ion in aqueous solution with a high selectivity over a wide dynamic range between 1.52 x 10(-9) and 1.70 x 10(-2) M, at pH 5, and a lower detection limit of 1.11 x 10(-9) M. Validation of the assay method revealed excellent performance characteristics for Hg2+ ions over a wide variety of other metal ions, including good selectivity, long-term response stability and high reproducibility. Applications, for the direct determination of mercury(II) in real samples, gave the results with good correlation with the data obtained by using cold vapor atomic absorption spectrometry. (C) 2010 Elsevier B.V. All rights reserved.