Anodically oxidized porous silicon as a substrate for EIS sensors

We study the electrochemical response of a field effect capacitor composed by a porous silicon (PS)/silicon dioxide (SiO2) structure as transducer's surface and p-tert-butylcalix[6]arene molecules as a recognizing agent towards nickel ions. Silicon samples were electrochemically anodized in a hydrofluoric acid (HF) electrolyte leading to PS formation. SiO2 layers were obtained by anodic oxidation (AO) of PS in aqueous solution. Electrochemical measurements of the sensor with an Electrolyte/Insulator/Semiconductor (EIS) structure have been performed in the Capacitance/Voltage (C/V) mode. A comparative study of sensor responses depending on AO solutions is presented. We have observed a closer Nernstian response, of the coated and oxidized PS, to the Ni2+ ions that were anodically oxidized in a KNO3 (1 M) solution.