Reduced Au3+ species in methanol in presence of iodide ions: A radiation chemical study

The reduction of Au3+ with free radicals such as esolv− and ∙CH2OH in methanol is reported. The rate constant values for esolv− and ∙CH2OH reactions with Au3+ were determined to be 6.5±1.0×109 M−1 s−1 and 1.6×109 M−1 s−1, respectively. In esolv−–Au3+ reduction process, the time resolved spectra recorded exhibit three absorption bands with peaks maxima at 270, 370 and 470 nm along with a strong bleaching around 320 nm. Similarly, in presence of I−, the transient absorption spectrum obtained exhibits four well-defined bands with peaks maxima at 290, 355, 505 and 720 nm, which were significantly different from those observed in the absence of I− under identical conditions. The difference in spectral and kinetics parameter in I− systems reveals the significance of I−, which helps in stabilization of various time-dependent transients formed in Au3+ reduction in methanol. The gold nanoparticles generated in γ-radiolysis were inert to oxygen.