The understanding of the interaction between protein and quantum dots (QDs) has significant implications for biological applications of QDs. Herein, we studied the effect of Ag 2 S QDs on human serum albumin (HSA) using UV-Vis absorption spectra and fluorescence spectroscopy and found that the fluorescence intensity of HSA was gradually decreased with increasing Ag 2 S QDs concentrations. By using the Stern-Volmer equation for the fluorescence quenching constant ( SV ) of the response of Ag 2 S QDs to HSA as well as thermodynamic equations, the values of thermodynamic enthalpy change (Δ ), entropy change (Δ ), and free energy change (Δ ) were calculated to be −10.79 KJ⋅mol −1 , 37.80 J⋅mol −1 ⋅K −1 , and −22.27 KJ⋅mol −1 , respectively. The results indicate that Ag 2 S QDs exert an obvious static fluorescence quenching effect on HSA and electrostatic interaction plays a key role in the binding process. Furthermore, Raman spectral analysis reveals that Ag 2 S QDs alter the external environment of tyrosine and tryptophan or the C-H bending of HSA but not the -helical content
