Study on the resistance to aging of CdS quantum dots encapsulated by PAMAM dendrimers

CdS quantum dots (QDs) of 2.5 nm were prepared using G4.5 PAMAM dendrimer templates and characterized by HRTEM and EDS. The aging of synthesized QDs stored in the dark at room-temperature was studied through UV-vis and PL spectrophotometer. The width at half-maximum of the peak (WHM) of the UV-vis and PL spectra becomes narrower, meanwhile the PL intensity increases obviously during the first 5d. Afterwards, the WHM gets broader and the PL intensity decreases slowly during the following 6 months. The results suggest that CdS QDs show a size-focusing growth within the first 5d, but a size-defocusing growth in the following 6 months. However, the increment of CdS QDs size is less than 0.3 nm, and the decrement of PL intensity is about 22% after 6 months of aging. The excellent resistance to aging of CdS QDs is attributed to the coordination and template effects of PAMAM dendrimers.