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Redox Charging of Nanoparticle Thin Films in Ionic Liquids

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journal contribution
posted on 28.10.2010, 00:00 by Wanzhen Li, Bin Su
Thin films consisting of alkanethiolate protected gold nanoparticles (MPCs) immersed in room temperature ionic liquids (ILs) were investigated by electrochemistry. The anion-dependent oxidative charging of MPC films was observed in imidazolium based ILs, which is similar to that of anion-rectified/limited oxidative charging previously observed in aqueous media. The absence of reductive charging in imidazolium ILs is simply because of the inadequate hydrophobicity of the imidazolium cation. Replacing the imidazolium cation with more hydrophobic tetrahexylammonium, the reductive charging of MPC films was observed. The ionic dependence manifests the charging process to be an ion-coupled electron transfer event, with the oxidative/reductive charging of MPCs at the electrode/film interface concomitant with the ionic partition at the film/IL interface. This system provides a diverse possibility of regulating the electronic properties of nanoparticle thin films by ionic/solvent functions, given that ILs are “designed solvents” with structures and functions easily tuned by ionic components (both anion and cation).