Biomimetic synthesis of CdS nanocrystals in the pepsin solution

CdS nanocrystals with an average size of 6.3 nm and narrow size-distribution were synthesized in the pepsin aqueous solution at room temperature. The obtained CdS nanocrystals were characterized by XRD, TEM, UV-vis, photoluminescence (PL) and thermal gravity-differential thermal analysis (TG-DTA). The results indicate that the pepsin not only induce the nucleation, but inhibit the further growth of CdS nanocrystals. The effect of Cd2+ on pepsin and the change of the pepsin secondary structure were studied. The possible mechanism of CdS nanocrystals formation was also discussed.