A colorimetric assay method for Co2+ based on thioglycolic acid functionalized hexadecyl trimethyl ammonium bromide modified Au nanoparticles (NPs)

A simple, rapid and sensitive colorimetric assay method for detection of Co2+ through thioglycollic acid (TGA) functionalized hexadecyl trimethyl ammonium bromide (CTAB) modified Au NPs has been discovered in our work. TGA functionalized CTAB modified Au NPs can be aggregated quickly in the presence of Co2+ through a cooperative metal-ligand interaction. Transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDS), and UV-vis spectra were used to characterize the Au NPs aggregation. The presence of Co2+ is monitored by a colorimetric response of functionalized Au NPs, and had a detection limit of 3.0 x 10(-7) M. Moreover, the selectivity of this method has been investigated by comparing with other metal ions (Hg2+, Na+, Cu2+, Cd2+, Ba2+, Pb2+, Mn2+, Ni2+, Zn2+, Fe2+ and Fe3+).