Encoded beads for electrochemical identification.

Encoded redox beads, based on the encapsulation of different quantum dots (QD) within polystyrene microspheres, have been developed for electrochemical identification. Encoded redox rods, prepared by sequential plating of different metal tracers into the pores of a host membrane, have also been designed. By incorporating different predetermined levels of multiple metal markers, such redox-encoded particles lead to a large number of recognizable voltammetric signatures and, hence, offer great promise for covert tagging of commercial products. The resulting voltammetric signatures correlate well with the predetermined loading ratio, indicating a reproducible encapsulation process. As desired for effective authenticity testing, QD-based "identification layers" were reproducibly cast and removed from packages of commercial products to display their distinct voltammetric profiles. Factors affecting the preparation of such identification layers were optimized.