Colorimetric detection of Cu based on the formation of peptide-copper complexes on silver nanoparticle surfaces.

We developed a colorimetric method for the rapid detection of copper ions (Cu) in aqueous solution. The detection of Cu is based on coordination reactions of Cu with casein peptide-functionalized silver nanoparticles (AgNPs), leading to a distinct color change of the solution from yellow to red. The developed method has a good detection limit of about 0.16 µM Cu using 0.05 mL of AgNPs stock solution and a linearity in the range of 0.08-1.44 µM Cu with a correlation coefficient of R = 0.973. The developed method is a useful tool for the detection of Cu ions. Furthermore, it can be used for monitoring Cu in water at concentrations below the safe limit for drinking water set by the World Health Organization.