Colorimetric captopril assay based on oxidative etching-directed morphology control of silver nanoprisms.

Oxidative etching is an effective approach to control the morphology of nanomaterials. Taking silver nanocrystals (AgNCs) as an example, oxidative etching-directed morphological transformation from a triangular prism shape to a disk shape is achieved and then applied to the determination of captopril. As a mediator, trace amount of halides play important roles in the shape-controlled evolution of AgNCs. Etching causes the color of the triangular silver nanoprims (AgNPRs) to change from blue to yellow on formation of round nanodisks. On addition of captopril, the oxidative etching of the AgNPRs is prevented owing to the protection by the drug via Ag-S bonding. In this case, the solution color does not change. This finding was used to design an assay of captopril that has a linear response in the 10-600 nM concentration range and a 2 nM limit of detection. This method also allows digital camera read-out. It was successfully applied to quality control of captopril in tablets. Graphical abstractOxidative etching-directed morphological transformation of silver nanocrystals is well manipulated and successfully applied in colorimetric determination of captopril in tablets.