Cost-Effective and Selective Fluorescent Chemosensor (Pyr-NH@SiO₂ NPs) for Mercury Detection in Seawater

The release of mercury into the environment has adverse effects on humans and aquatic species, even at very low concentrations. Pyrene and its derivatives have interesting fluorescence properties that can be utilized for mercury (Hg²⁺) ion sensing. Herein, we reported the highly selective pyrene-functionalized silica nanoparticles (Pyr-NH@SiO₂ NPs) for chemosensing mercury (Hg²⁺) ions in a seawater sample. The Pyr-NH@SiO₂ NPs were synthesized via a two-step protocol. First, a modified Stöber method was adopted to generate amino-functionalized silica nanoparticles (NH₂@SiO₂ NPs). Second, 1-pyrenecarboxylic acid was coupled to NH₂@SiO₂ NPs using a peptide coupling reaction. As-synthesized NH₂@SiO₂ NPs and Pyr-NH@SiO₂ NPs were thoroughly investigated by ¹H-NMR, FTIR, XRD, FESEM, EDS, TGA, and BET surface area analysis. The fluorescent properties were examined in deionized water under UV-light illumination. Finally, the developed Pyr-NH@SiO₂ NPs were tested as a chemosensor for Hg²⁺ ions detection in a broad concentration range (0-50 ppm) via photoluminescence (PL) spectroscopy. The chemosensor can selectively detect Hg²⁺ ions in the presence of ubiquitous ions (Na⁺, K⁺, Ca²⁺, Mg²⁺, Ba²⁺, Ag⁺, and seawater samples). The quenching of fluorescence properties with Hg²⁺ ions (LOD: 10 ppb) indicates that Pyr-NH@SiO₂ NPs can be effectively utilized as a promising chemosensor for mercury ion detection in seawater environments.