Functionalized mesoporous silica as a fluorescence sensor for selective detection of Hg²⁺ in aqueous medium

We combined the virtues of mesoporous silica and organic functional groups to develop a hybrid fluorescent sensor, PyU-SBA-15, with excellent ability to detect Hg²⁺ in aqueous medium with high selectivity. In this sensor, the pyrene fluorophore acts as the reporter and the urea unit acts as the receptor during Hg²⁺ determination. The control material, PyH-SBA-15, which lacks a carbonyl group in the receptor portion, did not display metal-ion selectivity, thereby demonstrating that introducing an additional metal-chelating unit is necessary to improve the metal-ion selectivity of the hybrid sensor. When the concentration of Hg²⁺ was increased, the fluorescence emission intensities of PyU-SBA-15 at 379, 398, and 476 nm gradually decreased. The emission intensity at 379 nm was linearly proportional to Hg²⁺ concentrations in the range of 0-1.0 × 10^-4 M, and the sensor was determined to have a detection limit of 9.92 × 10^-8 M. This work provides an effective strategy for improving or modulating the metal-ion selectivity of fluorescent sensors based on organic-inorganic hybrid mesoporous silica systems.