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+ Mg2+ Ca2+ (C) 2010 Elsevier Ltd All rights reserved