Colorimetric Electronic Tongue for Rapid Discrimination of Antioxidants Based on the Oxidation Etching of Nanotriangular Silver by Metal Ions

We present a simple, rapid, and effe/ctive colorimetric sensor array (or colorimetric electronic tongue) for discrimination of antioxidants, which is based on the oxidation etching of triangular silver nanoparticles (TriAgNPs) by three metal ions (Se2+, Sn4+, and Ni2+) as array's recognition elements and the inhibition of TriAgNP etching by antioxidants. Since highly reactive edges/tips of TriAgNPs are easier to be etched than other regions, the morphology of TriAgNPs undergoes a transition from nanoprism to nanodisk, accompanied by a color change from blue to yellow. The addition of diverse antioxidants inhibits TriAgNP etching in varying degrees, forming different etching morphologies with rainbowlike color. Surface plasmon resonance peak shift (Delta lambda) values of final TriAgNPs were captured as colorimetric signal outputs for further data processes. Linear discriminant analysis, hierarchical clustering analysis, heat map, etc. were adopted in the further data analysis process, showing the excellent discrimination ability of the sensor array for six antioxidants at 1 nM level. Moreover, selectivity experiments and practical application tests show that our sensor array had considerable selectivity and great potential in real samples.