A new spectroscopic protocol for selective detection of water soluble sulfides and cyanides: Use of Ag-nanoparticles synthesized by Ag(I)–reduction via photo-degradation of azo-food-colorants

Slow and controlled visible photo-reduction of AgNO3 by synthetic azo food-dyes in aqueous media produces spherical silver nanoparticles (Ag NPs). These show excellent selectivity toward inorganic anions (sulfide (S2−) and cyanide (CN−) with lowest detection limit (LOD) of ∼60 ppb. Complete photo-degradation of these dyes during nanoparticle formation can be very useful for environmental remediation and removal of dye toxicity. Detection of water soluble S2− and CN− is achieved by spectroscopic technique (fluorescence turn-on process), based on the etching of Ag NPs. Selectivity with respect to either of these two ions (S2− or CN−) is achieved by using suitable masking agents. This simple, rapid, and significantly low-cost sensing protocol can be employed at ease.