Exploring a new rapid colorimetric detection method of Cu2+ with high sensitivity and selectivity

In this study, we propose a new rapid colorimetric detection method of Cu2+ with high sensitivity and selectivity utilizing starch-stabilized silver nanoparticles (AgNPs), which are synthesized by a green chemistry way. AgNPs gradually become smaller in the presence of Cu2+ due to redox reaction between Ag and Cu2+, which results in color change and UV–vis absorption decrease of the nanoparticle dispersion. Therefore, Cu2+ could be recognized by visualizing the color change of AgNPs dispersed by naked eyes, and quantitatively measured by UV–vis spectra. There is a linear relationship between the absorbance ratio (A0/A, at 400 nm) and the concentration of Cu2+ ranging from 0.1 μM to 10 μM. The linear coefficient is 0.9968. The lowest detectable concentration is 0.5 μM by naked eyes. Furthermore, the selectivity of this detection system for Cu2+ is excellent comparing with other metal ions, such as Hg2+, Co2+, Ba2+, Zn2+, Na+, Fe3+, Sr2+, Pb2+, Cd2+, Ni2+, Ca2+, Mg2+, Mn2+ and K+. The high sensitivity and selectivity of the Cu2+ detection system are ascribed to the unique redox reaction between Ag and Cu2+.