A study on the interaction between CdTe quantum dots and chymotrypsin using optical spectroscopy

Thioglycolic acid (TGA) capped CdTe quantum dots (QDs) with the diameter of 2-3 nm were synthesized. The interaction between CdTe QDs and chymotrypsin (chy) was investigated by ultraviolet-visible (UV-vis) absorption, fluorescence and resonance Rayleigh scattering (RRS) spectroscopy. Under pH 7.2, CdTe QDs effectively quenched the intrinsic fluorescence of chy via static quenching. The binding constants for the formation of a complex between CdTe QDs and chy were 2.85, 2.58, 2.48 × 103 M−1 at 293, 298 and 303 K, respectively. ΔS° (49.72 kJ mol−1) and ΔH° (−4.61 kJ mol−1) indicated that electrostatic attraction was the dominant intermolecular forces in stabilizing the complex. The interaction between CdTe QDs and chy lead to the remarkable enhancement of RRS and the enchantments were in proportional to the concentration of chy in a certain range. The reasons for the enhancement of RRS were discussed. The experimental results showed that chy molecules have a relatively high affinity with CdTe QDs.