Multi-coloration of Calixarene-coated Silver Nanoparticles for the Visual Discrimination of Metal Elements.

Upon mixing with metal ions such as Cd, Tb, Cu, Ni, Pb, Zn, and Co at pH 10.0, solutions of silver nanoparticles (AgNPs) coated with calix[4]arene-p-tetrasulfonate (CAS-AgNP) exhibited multi-coloration from yellow to orange, violet, and green, depending on the metal elements present, which allowed for visual discrimination of the ions. This is contrary to the AgNP sensors exhibiting a uniform color change from yellow to red upon binding of a receptor molecules at the surface of AgNPs to an analyte.