Study of the interaction between mercaptoacetic acid (MAA) capped CdS quantum dots with denatured bovine serum albumin (dBSA)

The highly fluorescent thiol capped CdS quantum dots were synthesized by a novel aqueous synthesis route. In this method we used CdCl₂.2.5H₂O and sodium sulfide (Na₂S) as the Cd and S source, respectively with thioglycolic acid (TGA) as stabilizer. The structure of CdS nanocrystals was investigated by means of X–ray diffraction (XRD), energy–dispersive X–ray analysis (EDX), UV–visible, Fourier transform infrared (FT–IR) spectroscopy and transmission electron microscopy (TEM). The results showed the crystallinity of the CdS nanocrystals and the average size of CdS QDs was 3.15 nm. An aqueous solution of CdS capped with thioglycolic acid (TGA) shows a characteristic fluorescent peak at 560 nm, which decrease under the influence of both the pH and temperature. The interaction between water soluble colloidal mercaptoacetic acid (MAA) capped CdS quantum dots and denatured bovine serum albumin (dBSA) has been studied by using absorption and steady state fluorescence measurements. The interaction between quantum dots and dBSA occurs through static quenching mechanism.