Interaction between nitroxyl radicals and CdTe quantum dots: Determination of fluorescence-quenching mechanisms in aqueous solution

The present work characterizes the optical properties of CdTe quantum dots (CdTe QDs) after interaction with nitroxyl radicals based on steady-state and time-resolved fluorescence spectroscopy studies. QDs of different sizes were exposed to 2 different nitroxyl radicals, i.e., TEMPO and 4-amino-TEMPO radicals. A clear dependence of dynamic and static Stern-Volmer constants values, K_D and K_S, respectively, was observed as a function of the size of QDs used, with a change from a mostly static mechanism (for smaller QD sizes) to a dynamic mechanism predominating as the nanoparticles increase in size. All observed effects are dependent on both the concentration of the radical and the size of the nanoparticles. These results allow causal relationships to be established that could be used as a basis for the design of a potential sensor for this type of reactive species in aqueous media.