An electrochemical sensor for the detection of ascorbic acid (AA) has been constructed. Initially, a layer of poly-2,6-pyridinediamine (pPA) was fastened on the glassy carbon (GC) electrode surface through electropolymerization technique, then negatively charged nano-Au and positively charged 2,6-pyridinediamine (PA) were alternately adsorbed on the pPA-modified GC electrode by layer-by-layer technique to prepare PA/naono-Au/pPA/GC modified electrode. The preparation and electrochemical characteristics of the modified electrode were described through cyclic voltammetry and chronoamperometry. The modified electrode exhibits enhanced electrocatalytic behavior to the oxidation of AA for 2,6-pridinediamine bilayer films, providing abundant amino groups and positive charge, which promote the electron transfer between electrode and AA and enhance the sensitivity of electrode. Moreover, the oxidation peak potential of ascorbic acid shifts from 0.5 V on the bare glassy carbon electrode to 0.2 V on the PA/nano-Au/pPA/GC modified electrode, i.e., the oxidation potential of ascorbic acid shifts by 0.3 V in the negative direction, exhibiting hard evidence for the electrocatalytic oxidation of ascorbic acid. Under optimal conditions, the modified electrode was highly sensitive to oxidation of AA with a detection of 3.3 x 10(-8) mol L-1 and the linear range was from 1.0 x 10(-7) to 5.5 x 10(-3) mol L-1 (r = 0.9983) by cyclic voltammetry. (c) 2006 The Electrochemical Society.