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

[Image: see text] 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 AuCN(2)(–) 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.