Ultrasensitive fluorescence-quenched chemosensor for Hg(II) in aqueous solution based on mercaptothiadiazole capped silver nanoparticles

► Spectrofluorimetric determination of Hg(II) was carried out by using DMT-AgNPs. ► The emission intensity of DMT-AgNPs was decreased after addition of Hg(II). ► A detection limit of 1.0 pg L−1 was achieved for the first time. ► Quantum yield, association constant and Gibbs free energy changes were calculated. ► The results obtained in the present study were validated with ICP-AES method.