Anti-aggregation of gold nanoparticles for metal ion discrimination: A promising strategy to design colorimetric sensor arrays

The first report of anti-aggregation-based sensor arrays is presented. The strategy is based on the competitive interaction of citrate-capped gold nanoparticles (AuNPs) and heavy metal ions (Le., Hg(II), Ag(I), Fe(III), and Pb (II)) with three aggregation reagents (Le., cysteine, melamine, and arginine). In the presence of aggregation reagent, the color and UV-vis spectra of AuNPs are changed indicating the aggregation of AuNPs. Addition of the aggregation reagents which are firstly treated with the ions, causes AuNPs turn from the aggregation to the dispersion state. The anti-aggregation capability of ions towards various aggregation reagents is different because of distinct stability constants of ion-aggregation reagent complexes. The combinatorial colorimetric response of all sensor elements enables discrimination among the ions in various concentrations, as well as mixtures of them by linear discriminant analysis (LDA). Moreover, heavy metal ions are well-distinguished in river and fish samples with an accuracy of 100%.