Protein-Localized Bright-Red Fluorescent Gold Nanoclusters as Cyanide-Selective Colorimetric and Fluorometric...

Herein, we describe a bright-red-emitting ovalbumin-protected gold nanoclusters (OVA-AuNCs) that were prepared and applied as a luminescent probe for a simple, rapid, and highly sensitive determination of cyanide ions (CN^- ions) based on an emission quenching and colorimetric method. Initially, an intense red-emissive fluorescence of the OVA-AuNCs successfully disappeared upon the addition of CN^- ions. The resultant emission-quenching process involved CN^- ions etching the OVA-AuNC surface, which produced AuCN₂ ^- complexes in the presence of ambient oxygen. Under optimized experimental conditions, the relative emission intensity is inversely relative to CN^- ion concentrations ranging from 5.00 × 10^-7 to 75.00 × 10^-7 mol/L with a linear correlation coefficient of 0.9932. Furthermore, OVA-AuNC-based optical detection systems on both colorimetric and fluorometric assays were tested, which expose highly sensitive and specific determination of CN^- ions, and it is easily visualized by the naked eye (day light and UV light). Because of the distinct Elsner reaction between Au atoms of OVA-AuNCs and CN^- ions, the recent nanoprobe offered ultrasensitivity and good selectivity with the lowest limit of detection value of 68.00 × 10^-9 mol/L. In addition, this fluorescence "turn-off" CN^- ion detection method was executed in real water samples. The demonstrated route of OVA-AuNC preparation is extremely easy and quick, making the proposed selective and sensitive CN^- ion sensing assay based on the fluorescence response of the OVA-AuNCs for numerous practical applications.