Colorimetric detection of thiocyanate based on inhibiting the catalytic activity of cystine-capped core-shell Au@Pt nanocatalysts

In this work, core-shell Au@Pt nanocatalysts (Au@Pt NCs) with ultrathin Pt shell were synthesized and demonstrated high peroxidase-like activity. Thiocyanate ions (SCN - ) were found to effectively inhibit the peroxidase-like activity of Au@Pt NCs, and the mechanism was discussed by the characterization of TEM , DLS, EPR and XPS, etc. The inhibition of the catalytic activity of Au@Pt NCs by SCN - was mainly due to the decreased ability of the Au@Pt NCs for capturing • OH radicals and the increased ratio of Pt 2+ to Pt° on the surface of the Au@Pt NCs. A sensitive colorimetric detection of thiocyanate (SCN - ) was developed, based on the activity inhibition of Au@Pt NCs by SCN - . Interestingly, cystine modification of Au@Pt NCs was found to significantly improve the selectivity of SCN - recognition. After optimization, a colorimetric assay for SCN - was established with a detection limit of 5.0   nM and a broad linear calibration over the range of 20   nM to 40   µM. This assay has the advantages of highly sensitive, selective and low-cost. Moreover, this assay demonstrated highly potential application in the quantitative determination of SCN - in water and raw milk samples.