A long-term stable macroporous-type EIS structure for electrochemical sensor applications

A novel macroporous-type EIS (electrolyte–insulator–semiconductor) sensor for the detection of (bio-)chemical substances in aqueous solutions is presented. For the preparation of the macroporous layer, a specific cell configuration has been designed, which allows the formation of macroporous Si during the anodic etching process by means of a liquid contact. After the etching process, the SiO2/Si3N4 double layer insulator can be advantageously deposited by high-temperature processes, like thermal oxidation and low-pressure chemical vapour deposition (LPCVD) to realise the porous pH sensor. The so prepared pH sensors have an averaged sensitivity of about 59 mV/pH (concentration range between pH 4 and 9) during a period of more than 1 year. In order to prepare porous biosensors, the enzyme penicillinase has been additionally immobilised by simple physical adsorption into the porous structure. The sensitivity of the biosensor was about 140 mV/mM in the concentration range between 0.01 and 0.5 mM penicillin G.