Exploring the molecular interaction between tryptophan and β-cyclodextrin modified ZnS quantum dots using spectroscopic analysis.

The luminescent properties of water-soluble β-cyclodextrin surface-modified capped ZnS QDs (β-CD/ZnS QDs) were investigated for host-guest interactions. The optical properties of the β-CD/ZnS QDs complex revealed selectivity for L-tryptophan (L-Trp) through aggregation-induced emission. Fluorescence titration and Dynamic Light Scattering analysis revealed the fluorescence enhancement effect and aggregation state of β-CD/ZnS QDs in the presence of L-Trp, respectively. The apparent binding constant was determined 1.75x10-8M-1 determine, along an LOD of 420 nM for L-Trp. UV-Visible, Raman, Fourier transform infrared, and Matrix-Assisted Laser Desorption/Ionization (MALDI) - mass spectrometry were used to investigate the interaction of β-CD/ZnS QDs with L-Trp. Moreover, the β-CD/ZnS QDs probe was used for L-Trp detection in soybeans, yielding 91-97% recovery using fluorescence titration.