Layer-by-layer assembly of electroactive dye/inorganic matrix film and its application as sensor for ascorbic acid

A novel inorganic–organic composite ultrathin film was fabricated by layer-by-layer assembly of naphthol green B (NGB) and layered double hydroxides (LDHs) nanoplatelets, which shows remarkable electrocatalytic behavior for oxidation of ascorbic acid. LDHs nanoplatelets were prepared using a method involving separate nucleation and aging steps (particle size: 25 ± 5 nm; aspect ratio: 2–4) and used as building blocks for alternate deposition with NGB on indium tin oxide (ITO) substrates. UV–vis absorption spectroscopy and XRD display regular and uniform growth of the NGB/LDHs ultrathin film with extremely c-orientation of LDHs nanoplatelets (ab plane of microcrystals parallel to substrates). A continuous and uniform surface morphology was observed by SEM and AFM image. The film modified electrode displays a couple of well-defined reversible redox peaks attributed to Fe2+/Fe3+ in NGB (ΔEp = 68 mV and Ia/Ic = 1.1). Moreover, the modified electrode shows a high electrocatalytic activity towards ascorbic acid in the range 1.2–55.2 μM with a detection limit of 0.51 μM (S/N = 3). The Michaelis–Menten constant was calculated to be K M a p p = 67.5   μ M .