Polyethyleneimine as a pH sensitive film for potentiometric transducers

The anodic oxidation of ethylenediamine (EDA) leads to the formation of polyethyleneimine (PEI) as a pH sensitive thin film on conducting and semi-conducting electrode surfaces. The passivated electrodes exhibit a sub-nerstian response which depends strongly on the electrode material. In particular, the PEI-coated silicon electrodes present a linear pH sensitivity close to 50 mV per pH unit over a large pH range. This response could be fitted with the site-binding model applied to the acido-basic equilibrium of amino groups present at PEI/electrolyte interface.