Study of formation of aqueous Tl, Cu and Cd clusters by γ- and electron irradiation

Abstract

The spectral characteristics of the Tl, Cu and Cd clusters produced by both γ- and electron irradiation of solutions containing Tl +, Cu 2+ and Cd 2+ ions in the presence of polyethylene glycol (PEG) stabilizer have been studied in aqueous medium. A comparison of the two reduction methods suggested that the low dose rate conditions of γ-irradiation favours the formation of larger cluster aggregates having higher absorption in the longer wavelength region above ∼500 nm. Whereas, the relatively higher dose rate of electron irradiation, generally, resulted in smaller sized clusters having more absorption mostly in the lower wavelength region below 500 nm. All these clusters of Tl, Cu and Cd, are found to be stable under N 2 atmosphere in close condition, but get oxidized very fast on exposure to air. The clusters of Tl and Cd can reduce methyl viologen (MV 2+) chloride to its radical-cation (MV +), whereas, the copper cluster are unable to reduce it. The γ-radiolytically produced Tl and Cd clusters are found stable to further γ-irradiation, but unstable to electron irradiation and undergo complete dissolution in about 6 and 15 kGy of dose, respectively, mainly due to the decrease in pH and the e aq − reaction with the clusters.