Luminescence Enhancement based Sensing of L-Cysteine by Doped Quantum Dots

The interaction of a presynthesized orange emitting Mn²⁺-doped ZnS quantum dots (QDs) with L-Cysteine (L−Cys) led to enhance emission intensity (at 596 nm) and quantum yield (QY). Importantly, the Mn²⁺-doped ZnS QDs exhibited high sensitivity towards L−Cys, with a limit of detection of 0.4±0.02 μM (in the linear range of 3.3–13.3 μM) and high selectivity in presence of interfering amino acids and metal ions. The association constant of L−Cys was determined to be 0.36×10⁵ M⁻¹. The amplified passivation of the surface of Mn²⁺-doped ZnS QDs following the incorporation and binding of L−Cys is accounted for the enhancement in their luminescence features. Moreover, the luminescence enhancement-based detection will bring newer dimension towards sensing application.