Dopamine dithiocarbamate functionalized silver nanoparticles as colorimetric sensors for the detection of cobalt ion

A colorimetric assay has been developed for facile, rapid and sensitive detection of Co2+ using dopamine dithiocarbamate functionalized silver nanoparticles (DDTC-Ag NPs) as a colorimetric sensor based on unique surface plasmon resonance properties. The presence of Co2+ induces the aggregation of Ag NPs through coordinate covalent bonds between the catechol groups of DDTC on the surface of Ag NPs and cobalt ions, resulting in a color change from bright yellow to reddish. These color changes are measured by UV-vis spectrophotometry, and can be directly read out with the naked eye. For the detection, UV-visible absorption spectra were measured by the absorbance ratio A570nm/A390nm. Under the optimum conditions, the analytical response was linear over the range from 1.0 mM to 15 mM (R2 = 0.993) with a detection limit of 14 μM. The proposed DDTC-Ag NPs-based colorimetric method is simple and sensitive for the detection of cobalt ions and allows for the monitoring of cobalt ions directly with naked eye.