Excitation Wavelength Dependent Quantum Yield in Water Soluble CdTe Quantum Dots

The quantum yield (QY) of semiconductor quantum dots (QDs) is severely hampered by the inherent fluorescence intermittency. The QY of QDs typically increases with an increase in the excitation wavelength. Here, we present a distinctive behavior, where the QY is found to decrease with an increase in the excitation wavelength in water-soluble CdTe QDs (CQDs). Single-particle level measurements highlight the increase in permanent single dark particles at longer wavelengths that comprehend the overall QY of the CQDs in bulk solution. Fluorescence correlation spectroscopy further revealed an increase in the number of dark particles at longer wavelengths. As confirmed by D