Influence of gamma-radiation on room-temperature ionic liquid [bmim][PF6] in the presence of nitric

Stability of ionic liquid 1-methyl-3-butylimidazolium hexafluorophosphate ([bmim][PF6]) in the presence of nitric acid (HNO3) was investigated under gamma-radiation. It was found that incorporating HNO3 into [bmim][PF6] obviously inhibits the radiation-induced darkening of [bmim][PF6] due to the oxidizability of HNO3. More detailed UV-vis analysis reveals linear decrease of light absorbance of irradiated [bmim][PF6]/HNO3 with increasing concentration of HNO3 to 2 mol L-1, which is consistent with the color evolution observed by the naked eye. FTIR and NMR measurements indicates that HNO3 slightly accelerates the radiolysis of [bmim][PF6] at high dose (550 kGy), the amount of nonvolatile radiolysis products, however, is less than 1 mol%. (C) 2009 Elsevier Ltd. All rights reserved.