Effect of gamma-ray irradiation on the size and properties of CdS quantum dots in reverse micelles

• Gamma irradiation method has been used successfully to change the size and optical properties of CdS quantum dots synthesized in micellar solutions.
• γ-Irradiation reduces the size polydispersity of quantum dots in the micellar system.
• Fluorescence intensity of CdS quantum dots is enhanced after γ-irradiation.
• Fluorescence lifetime of single CdS quantum dots increases after γ-irradiation.

Cadmium sulfide quantum dots 1.3–5.6 nm in size have been synthesized in sodium bis(2-ethylhexy1)sulfosuccinate (AOT)–water–isooctane micellar solutions with various [H2O]/[AOT] molar ratios (w=2.5, 5.0 or 10). Gamma irradiation method has been used to change the size and optical properties of quantum dots. It has been found that γ-irradiation reduces the size polydispersity of quantum dots in the micellar system and alters their fluorescent properties. Fluorescence intensity is enhanced after γ-irradiation. The average fluorescence lifetime of single quantum dots sized 5.2±0.4 nm increases from 5.14 to 6.39 ns after γ-irradiation at a dose of 7.9 kGy. To the best of our knowledge, this is the first report on fluorescence lifetime of single CdS quantum dots in micellar solution.