Sol–gel processed ionic liquid – hydrophilic carbon nanoparticles multilayer film electrode prepared by layer-by-layer method

Abstract

Multilayer hydrophilic carbon nanoparticles modified electrodes are prepared by a layer-by-layer method combined with sol–gel processing. A tin doped indium oxide substrate is alternatively immersed in sulfonated carbon nanoparticles solution and a sol containing the ionic liquid precursor 1-methyl-3-(3-trimethoxysilylpropyl)imidazolium bis(trifluoromethyl-sulfonyl)imide together with tetramethyl orthosilicate. The thickness of the film is proportional to the number of immersion and withdrawal steps. Scanning electron microscopy image reveals relatively uniform distribution of carbon nanoparticles within the film. The resistance of the electrode increases only slightly after film deposition. More importantly the electrochemical behaviour of the electrode connected with double layer charging, irreversible hydrogen peroxide reduction and oxidation–reduction of the immobilised redox liquid – t-butyloferrocene and the simple redox reaction of 1,1′-ferrocenedimethanol correlates with the number of immersion and withdrawal steps. Clearly the subsequent immobilisation of a larger number of carbon nanoparticles increases the electrochemically active surface and provides an extended solid|organic liquid|aqueous solution boundary. The electrode also acts as a reversible sponge for Fe ( CN ) 6 3 - anions due to an excess of imidazolium functional groups. 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) anion – a popular enzyme mediator is irreversibly accumulated on the electrode. The electrode modified with it exhibits catalytic behaviour in dioxygen saturated aqueous solution in the presence of laccase.