Thin chitosan-carbon nanoparticle films (ca. 2 nm average thickness increase per layer) are assembled onto tin-doped indium oxide (ITO) electrode substrates in a layer-by-layer deposition process employing carbon nanoparticles of ca. 8 nm average diameter and an aqueous solution of chitosan (poly-D-glucosamine, low molecular weight, 75-85% deacetylated). Chitosan introduces amine/ammonium functionalities which are employed for the immobilization of redox systems (i) via physisorption of indigo carmine and (ii) via chemisorption of 2-methyleneanthraquinone. The number of binding sites within the chitosan-carbon nanoparticle film is controlled by changing the thickness of the film deposit or by changing the chitosan content, which is varied by changing the chitosan concentration during layer-by-layer deposition. Voltammetric characteristics and stability of the chemisorbed and physisorbed redox systems are reported as a function of pH. The physisorbed redox system is expelled from the film at a pH consistent with the pK(A) of chitosan ( approximately 6.5). However, the 2-methyleneanthraquinone redox system remains stable even in alkaline media and only a minor inflection in the plot of midpoint potentials vs. pH indicates the film deprotonation process at the pKA of chitosan.
Rassaei, L., Bonne, M. J., Sillanpaa, M., & Marken, F. (2008). Binding site control in a layer-by-layer deposited chitosan-carbon nanoparticle film electrode. New Journal of Chemistry, 32(7), 1253-1258. https://doi.org/10.1039/b800331a