Electrochemical behaviors of polyaniline confined in highly ordered micro-sized SiO2 cavities

• An array of tunable polyaniline cavity microelectrode was fabricated.
• Polyaniline grew independently in ordered SiO2 cavities and eventually covered entire electrode.
• The cavity structure enlarged effective electrode area.
• The radial diffusion enhanced the electrochemical oxidation of ascorbic acid.

An array of microelectrodes is fabricated with highly ordered SiO2 cavities modified on an indium-doped tin oxide (ITO) electrode, benefiting from the confinement of the insulating SiO2 cavities. Aniline can be electrochemically polymerized to form polyaniline (PANI) independently inside each SiO2 cavity. The edge effect of the microelectrodes leads to the radial diffusion of aniline in the SiO2 cavities; as a result, the PANI grows uniformly along the wall of the cavities and eventually covers the whole surface area of the SiO2 cavities to form an array of PANI cavities. Thus, the effective area of the PANI modified electrode could be greatly enlarged through such a surface structure modification. Moreover, it is demonstrated that the electrochemical reaction of ascorbic acid can be enhanced due to the radial diffusion of ascorbic acid inside PANI cavities. The specific features of the PANI cavity array enables us to develop a sensing platform of ascorbic acid detection with a detection limit of 0.14 μM (S/N = 3) and a linear range of 0.5–131 μM.