Redox behavior of Fe(CN)₆^3-/4- ions on the electrodes coated with a layer-by-layer film composed of carboxymethylcellulose

Multilayer thin films were prepared on the surface of a gold (Au) electrode using sodium carboxymethylcellulose (CMC) to elucidate the suitability of the polysaccharide-based thin film as a scaffold for constructing chemical sensors. A quartz crystal microbalance study revealed that an alternate deposition of CMC and poly(allylamine hydrochloride) (PAH) gives an exponentially growing multilayer films on the surface of a quartz resonator. The PAH-CMC film-coated Au electrodes exhibited a redox response to Fe(CN)₆^3-/4- ions in solution, depending on the number of layers in the film. The PAH-CMC films were permeable to Fe(CN)₆^3-/4- ions irrespective of the thickness and the sign of electric charges on the outermost surface of the film, suggesting a loosely-packed porous nature of the film. It was found that the film contained electrostatic binding sites to which Fe(CN)₆ ^3-/4- ions can be strongly immobilized.