Inducing enantioselectivity in electrodeposited CuO films by chiral etching

Enantiospecificity was induced in racemic CuO films by etching the films in 10 mM solutions of l(+)- or d(−)-tartaric acid. The CuO films were electrodeposited from an aqueous solution of 5 mM CuSO4, 50 mM glycine, and 200 mM NaOH using a constant anodic current density of 0.1 mA/cm2. Etching of the 112 nm thick films was followed in real time using the quartz crystal microbalance. The enantiospecificity of the films was studied by cyclic voltammetry, using the oxidation of the tartrate ion as the probe reaction. Although the as-deposited film showed no enantioselectivity, the films etched in l(+)-tartaric acid were selective for the oxidation of l(+)-tartrate, whereas the films etched in d(−)-tartaric acid were selective for the oxidation of d(−)-tartrate. The induced selectivity is attributed to the production of chiral surfaces on the electrodeposited CuO as a result of the etching process.