Ion selective gate based on silica/gold cavity array for electrochemical detection of dopamine

• Silica/gold cavity array microelectrodes were fabricated.
• Silica surface was sulfonated to provide negative charges.
• The modified cavities exhibited excellent ion selectivity.
• The ion selective gate of the cavities selectively detected dopamine in the presence of ascorbic acid and uric acid.

A silica/gold (SiO2/Au) cavity array microelectrode was fabricated on a gold film-coated glass slide by using highly ordered monodispersed polystyrene spheres as a template. The surface of the silica, as the upper part of the cavity, was sulfonated by 1,3-propanesultone, providing negative charges on the surface of the cavities in a media with pH > 2. The ion selectivity of the sulfonated SiO2/Au cavities was revealed by voltammetric response of potassium ferricyanide and methyl viologen dichloride as the electrochemical probes. Due to the electrostatic interaction, the positively charged methyl viologen cations can transport through the negatively charged SiO2 gate and react on active sites at the bottom of the cavities, whereas the diffusion access of the negatively charged ferricyanide anions into the cavities is blocked by the SiO2 gate. The ion selective gate of the cavities enables the electrode to selectively detect dopamine in the presence of ascorbic acid and uric acid, giving a linear range from 15 μM to 160 μM and a low detection limit of 85 nM.

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