CdS nanocrystals were prepared and modified with thiolic acid. The functionalized nanocrystals were water soluble and biocompatible. Bioinorganic conjugates between CdS nanocrystals and peptides were formed via electrostatic/coordinate self-assembly. The photoluminescence properties of CdS nanocrystals and their bioinorganic conjugates have been studied. The photoluminescence intensities of the bioinorganic conjugates between CdS nanocrystals and peptides with mercaptophenols were improved obviously with increasing the concentration of peptides due to the perfect wrapping of CdS nanocrystal surface and the elimination of defects on CdS nanocrystal surface. The emission intensities of the bioinorganic conjugates between CdS nanocrystal and peptide with terminal amino groups exhibit maximum at the appropriate concentration of peptide. The fluorescence of functionalized CdS nanocrystal was quenched in the presence of peptides with no mercaptophenols and no terminal amino-groups, the quenching mechanism of the combination of CdS nanocrystal with this kind of peptide is a static quenching procedure, the equilibrium binding constant is about 2×10⁴, and the number of binding sites is in the range of 0.87 to 1.00.

Key words: CdS nanocrystal, peptide, photoluminescence, interaction, self-assembly