Blinking statistics of colloidal quantum dots at different excitation wavelengths

In imaging applications the blinking of quantum dots is an ambiguous phenomenon. Although unwanted in conventional imaging, blinking is of significant relevance for super-resolution microscopy. Recent studies report on excitation-wavelength dependent quantum dot blinking, while other studies do not observe this effect. To investigate this disagreement we have systematically studied the effect of the excitation wavelength on blinking of CdSe/ZnS core-shell quantum dots that are commonly used in imaging applications. We recorded single quantum dot intensity traces for 14 different excitation wavelengths and determined for each excitation wavelength the probability to find short- (<0.5 s) and long- (>0.5 s) lasting bright state periods. This represents a systematic study of a larger set of excitation wavelengths than heretofore reported in the literature. For the quantum dots analyzed, we find minor variations in blinking with excitation wavelength. These variations do not follow a trend and do not correlate with features in the absorbance spectrum of the quantum dots. Our results show that in practice changing the excitation wavelength for CdSe/ZnS quantum dots does not allow optimization of blinking for e.g. super-resolution microscopy and that the effect of blinking as a function of excitation wavelength is not a salient parameter in imaging applications.