A colorimetric electronic tongue for rapid discrimination of antioxidants based on the oxidation etching of nano-triangular silver by metal ions.

We present a simple, rapid, and effective 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 TriAgNPs 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 TriAgNPs etching in varying degrees, forming different etching morphologies with rainbow-like color. Surface plasmon resonance (SPR) peak shift (Δλ) values of final TriAgNPs were captured as the colorimetric signal outputs for the further data processes. Linear discriminant analysis (LDA), hierarchical clustering analysis (HCA), heat map, etc. were adopted in 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.