Reduction of the copper ion to its metal and clusters in alcoholic media: A radiation chemical study

Reduction of Cu2+ ions with and without I- as a ligand was studied in N-2-purged alcoholic solutions by pulse radiolysis. In the absence of iodide ion, the initial rate constant for e(sol)(-) reaction with Cu2+ was determined following the decay of solvated electrons indifferent alcohols, k(bimol) values are in the range of 0.8 1.1 x 10(10) dm(3) mol(1) s(-1). In the presence of 10(-3) mol dm(-3) KI, the respective k(bimol) remained almost same, Generally, on reduction, Cu(II) ion changes to Cu(I) ion initially and later it produces metallic copper (Cu-), and the stability of these intermediates depends on the conditions of the matrix. In the presence of I-, Copper ions such as Cu(II) or Cu(I) ions get reduced to metallic copper (Cu-o) having initial absorption around 740 and below 400 nm. Later, at 100 mu s time after the electron pulse, it gets transformed into a nanoparticle with an absorption band at 580 nm. Such formation or copper nanoparticle was observed only in 2-propanolic medium in the presence of iodide ions, During gamma-radiolysis of N-2-purged 1.5 X 10(-4) CuSO4 solutions in 2-propanol, reddish pink colored copper nanoparticles were formed, which are quite similar to those reported earlier in aqueous solution. But, in the presence of I (2-propanolic solutions), Such phenomenon was not noticed on gamma-radiolysis. Interestingly, the formation of copper nanoparticle was observed also it) the reactions of copper (II) ions with alcohol radicals formed during gamma-radiolysis in N2O-purged system. where e(sol) were scavenged by N2O. The nanoparticles generated both in N-2 and N2O-purged alcoholic systems, viz, methanol, ethanol and 2-propanol, were found to be oxygen sensitive. The contradictory results from Pulse and gamma-radiolysis studies in the presence and absence of iodide ions are explained to account for the nanoparticle generation. (C) 2005 Elsevier Ltd. All rights reserved.