Sensitive and selective detection of l-tryptophan using Mn–ZnS QDs as the ratiometric emission probe

A ratiometric fluorescence method for the detection of L-tryptophan based on mono-6-SH-β-cyclodextrin modified Mn-doped ZnS quantum dots has been developed. It exhibits a highly selective ratiometric emission response (400/598 nm) to L-tryptophan over other amino acids. β-Cyclodextrin still retained the ability of molecular recognition when it was coated on the surface of Mn–ZnS QDs, and this is also the cause for the identification of L-tryptophan.