Gum acacia-based silver nanoparticles as a highly selective and sensitive dual nanosensor for Hg(ii) and fluorescence turn-off sensor for S2− and malachite green detection

Abstract

A facile and green method was adopted to synthesize highly selective gum acacia-mediated silver nanoparticles as dual sensor (fluorescence turn-on and colorimetric) for Hg(II) and fluorescence turn-off sensor for S²⁻ and malachite green. The mechanism proposed for a dual response towards Hg(II) is the redox reaction between Ag(0) and Hg(II), resulting in the formation of Ag(I) and Hg(0) and electron transfer from gum acacia to Ag(I), which further leads to the formation of an Ag@Hg nanoalloy. The enhanced fluorescence signal was quenched selectively by S²⁻ owing to the formation of Ag₂S and HgS. The reported nanosensor was found to be useful for sensing malachite green via the inner filter effect. The linear ranges were 3 nmol L⁻¹ to 13 μmol L⁻¹ for Hg(II), 3–170 μmol L⁻¹ for S²⁻ and 7–80 μmol L⁻¹ for malachite green, and the corresponding detection limits were 2.1 nmol L⁻¹ for Hg(II), 1.3 μmol L⁻¹ for S²⁻ and 1.6 μmol L⁻¹ for malachite green.