Determination of cyanide based on a dual-emission ratiometric nanoprobe using silver sulfide quantum dots and silicon nanoparticles

A novel ratiometric fluorescent nanoprobe was designed for the sensitive determination of cyanide anion (CN-) by the electrostatic attraction between positively charged silicon nanoparticles (Si NPs) and negatively charged silver sulfide quantum dots (Ag2S QDs). The nanoprobe exhibited two well-resolved emission peaks at 446 nm and 540 nm under a single excitation wavelength (360 nm). In the presence of CN-, the fluorescence of Ag2S QDs at 540 nm was remarkably quenched, while the fluorescence of the Si NPs at 446 nm remained constant, establishing the desired conditions for ratiometric fluorescence detection. Under optimal conditions, the ratiometric fluorescence assay showed good linearity (R2 = 0.9921) within the range 0.05-15 μM, and the limit of detection was calculated to be 56 nM (at an S/N ratio of 3). The proposed Ag2S QD/Si NP nanoprobe has been successfully used to determine CN- in water and sprouting potato samples with satisfactory recoveries in the range 97-110.5%.