β-Cyclodextrin functionalized Mn-doped ZnS quantum dots for the chiral sensing of tryptophan enantiomersElectronic supplementary information (ESI) available: pH effect on the PL intensity of the as-synthesized β-CD-Mn-ZnS QDs, PL spectra of β-CD-Mn-ZnS QDs/Trp enantiomers at different equilibration time and UV-vis spectra of the mixture of Trp enantiomers and β-CD at various standing time. See DOI: 10.1039/C4PY00618F

Hydrothermally prepared mono-6-SH-β-cyclodextrin capped Mn-doped ZnS quantum dots (β-CD-Mn-ZnS QDs) exhibited dual photoluminescence (PL) at 430 nm and 598 nm, respectively, upon excitation at 315 nm. The PL intensity of β-CD-Mn-ZnS QDs responded to tryptophan enantiomers differently: the d -isomer showed little effect while l -tryptophan displayed a large time-dependent enhancement in the PL intensity of QDs. This chiral selectivity originated from the β-cyclodextrin coating on the surface of Mn-ZnS QDs, which shows different inclusion constants for tryptophan enantiomers. β-CD-Mn-ZnS QDs further selectively hydrolyse l -tryptophan, forming a product that greatly enhances the QD photoluminescence. Based on these findings, a photoluminescence chiral-assay for tryptophan enantiomers was developed. l -Tryptophan can be detected in the presence of its stereoisomer with a detection limit of 5.4 nM in a linear range of 0-6.0 μM. A versatile, multi-functional photoluminescence platform for chiral recognition and sensing of tryptophan enantiomers is fabricated based on cyclodextrin modified Mn-ZnS quantum dots.