Highly selective and sensitive method for Cu detection based on chiroptical activity of L-Cysteine mediated Au nanorod assemblies.

Herein, we demonstrated a simple and efficient method to detect Cu based on amplified optical activity in the chiral nanoassemblies of gold nanorods (Au NRs). L-Cysteine can induce side-by-side or end-to-end assembly of Au NRs with an evident plasmonic circular dichroism (PCD) response due to coupling between surface plasmon resonances (SPR) of Au NRs and the chiral signal of L-Cys. Because of the obvious stronger plasmonic circular dichrosim (CD) response of the side-by-side assembly compared with the end-to-end assemblies, SS assembled Au NRs was selected as a sensitive platform and used for Cu detection. In the presence of Cu, Cu can catalyze O oxidation of cysteine to cystine. With an increase in Cu concentration, the L-Cysteine-mediated assembly of Au NRs decreased because of decrease in the free cysteine thiol groups, and the PCD signal decreased. Taking advantage of this method, Cu could be detected in the concentration range of 20pM-5nM. Under optimal conditions, the calculated detection limit was found to be 7pM.