Self-assembly of l -cysteine–gold nanoparticles as chiral probes for visual recognition of 3,4-dihydroxyphenylalanine enantiomers

A simple protocol to distinguish enantiomers is extremely intriguing and useful. Herein, we report on a method for the visual recognition of 3,4-dihydroxyphenylalanine (Dopa) enantiomers. It is based on the chirality of l -cysteine-capped gold nanoparticles ( l -Cys-capped AuNPs) that can be used as a chiral selector for l - and d - forms of Dopa. On addition of l -Dopa to a solution of the l -Cys-capped AuNPs, a color change from red to blue can be seen, while no color change is found on addition of d -Dopa. The chiral recognition can be achieved by eye and simple spectrophotometry. Notably, this method does not require complicated chiral modification. The method excels through its low-cost, good availability of materials, and its simplicity.