Selective Detection of Iodide and Cyanide Anions Using Gold-Nanoparticle-Based Fluorescent Probes

We developed two simple, rapid, and cost-effective fluorescent nanosensors, both featuring bovine serum albumin labeled with fluorescein isothiocyanate (FITC))-capped gold nanoparticles (FITC–BSA–Au NPs), for the selective sensing of cyanide (CN^–) and iodine (I^–) ions in high-salinity solutions and edible salt samples. During the preparation of FITC–BSA–Au NP probes, when AuNPs were introduced to the mixture containing FITC and BSA, the unconjugated FITC and FITC-labeled BSA (FITC–BSA) adsorbed to the particles’ surfaces. These probes operated on a basic principle that I^– and CN^– deposited on the surfaces of the Au NPs or the etching of Au NPs induced the release of FITC molecules or FITC–BSA into the solution, and thus restored the florescence of FITC. We employed FITC–BSA to protect the Au NPs from significant aggregation in high-salinity solutions. In the presence of masking agents such as S₂O₈^2–/Pb²⁺, FITC–BSA–Au NPs facilitated the selective detection of CN^– (by at least 150-fold in comparison with other anions). We also demonstrated that the FITC–BSA–Au NPs in the presence of H₂O₂ could selectively detect I^– down to 50 nM. Taking advantages of their high stability and selectivity, we employed our FITC–BSA–Au NP-based probes for the detection of CN^– and I^– in water samples (pond water, tap water, and seawater) and detection of I^– in edible salt samples, respectively. This simple, rapid, and cost-effective sensing system appears to demonstrate immense practical potential for the detection of anions in real samples