Manipulating spectral properties of the Hg (II) sensitive carbazole-oxadiazole derivative by silver nanoparticles: Two different sensing mechanisms for the same probe

In this work, a newly synthesized fluorescent probe was used along with silver nanoparticles (AgNPs) for selective sensing of the sub-nanomolar concentrations of ionic mercury. We offered two different sensing mechanisms for the same probe manipulating its spectral properties by additives. The convenient sensing mechanism was relying on the quenching-based interaction of Hg (II) with the fluoroionophore in plasticized PMMA matrix at a certain wavelength. The second way relies on nanoscale chemistry of the silver and following formation of Ag-Hg solid amalgams on the surface of the sensing materials. The silver-equipped optodes allowed the ratiometric determination of Hg (II) in the working range of 1.0 x 10- 12-1.0 x 10-3 M with a detection limit of 3.9 10-14 and 7.9 10-14 M for the AgNP equipped electrospun fibers and thin films, respectively. The sensor exhibited excellent selectivity for the Hg (II) with respect to the convenient alkali, alkaline earth, and transition metal ions. In addition to the extraordinary sensitivity and selectivity, the dye exhibited high fluorescence quantum yield, long excitation, and emission wavelength, and high Stokes' shifts in the solid matrix which makes it compatible with solid-state optics including fiber optics and LEDs