Colorimetric detection of mercuric ion (Hg2+) in aqueous media using chemodosimeter-functionalized gold nanoparticles

In this paper, the synthesis of a selective chemodosimeter for mercury ion based on the mercury-promoted intramolecular cyclic guanylation of thiourea connected with 1,8-naphthalimide and its immobilization on the surface of gold nanoparticles (AuNPs) was described. The chemodosimeter preserves its sensory ability after being attached to AuNPs and displays significant absorption spectral changes when being employed in acetonitrile in the presence of Hg(II) which can be easily read out by the naked eye. However, the nanoparticles-based system still results in poor optical absorbance response to Hg(II) in water. Fortunately, the addition of anionic surfactant sodium dodecyl sulfate (SDS) ensures more effective communication between receptors and Hg(II) ions and thus leads to a more sensitive colorimetric response to Hg(II) in water. Hg(II) ions induce no emission changes of the nanoparticles-based system due to the ultra-high quenching efficiency of AuNPs towards anchored organic fluorophores.