Static quenching of bovine serum albumin conjugated with small size CdS nanocrystalline quantum dots

The author reports on a strong fluorescence quenching of a model transport protein, bovine serum albumin BSA, when bioconjugated with CdS quantum dots QDs. The 4.4 nm size CdS QDs were synthesized using wet chemistry method and were characterized using UV-vis spectroscopy, scanning electron microscopy SEM and X-ray diffraction XRD techniques. It was found that the BSA fluorescence quenching increases linearly with increasing the CdS QDs concentrations in the range of 3×10⁻⁷-2.0×10⁻⁶ mol L⁻¹. This quenching is explained in terms of Stern-Volmer equation and is ascribed to static quenching with quenching constant 1.321×10⁴ L mol⁻¹ at 300 K.