A reversible solid optical sensor (SGIR) for Hg(2+) based on silica gel was designed and synthesized. The binding and adsorption abilities of SGIR for metal cations were investigated with fluorophotometry and cold vapor atomic absorption spectrometry, respectively. The SGIR exhibits high selectivity for sensing Hg(2+) over other metal cations in aqueous media because the Hg(2+) ion selectively induces a ring opening of the rhodamine fluorophores, and the SGIR was also found to adsorb 72% of Hg(2+) ion. The determination of Hg(2+) in both tap and lake water samples displays satisfactory results, and the SGIR can also be easily recovered by treatment of a solution of TBA(+)OH(-).