Ion-selective detection of non-intercalating Na + using competitive inhibition of K + intercalation in Prussian blue nanotubes sensor

Abstract

A nanotubes sensor for Na + is fabricated using electrodeposition of iron hexacyanoferrate polymer within the nanochannels of a nanoporous metal-coated membrane. The sensing signal is derived from the influence of Na + on the cathodic peak potential of the voltammetric response of the Prussian blue (PB) nanotubes immersed in a background solution containing K +, giving a 2K +:1e − Nernstian response, instead of the usual 1K +:1e − process in the absence of Na +. A competitive-inhibition reaction scheme is proposed which gives excellent agreement of theoretical values derived from equilibrium consideration, with experimental data obtained under reversible, slow scan rate conditions. A wide linear range over three orders of magnitude for Na sensing can be achieved by simple adjustment of background K + levels. Specific and accurate detection of Na + using the PB nanotubes sensor is demonstrated in a solution containing potential interfering ions: K +, Mg 2+, Ca 2+.