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)-O-center dot radicals and the increased ratio of Pt2+ to Pt-0 on the surface of the Au@Pt NCs. A sensitive calorimetric 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 mu M. 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.