Electrochemical Impedance Spectroscopy at Well‐Controlled dc Bias for Nanoporous Platinum Microelectrodes in Rat Embryo Brain

Nanoporous Pt with extremely small (1-2 nm) and uniform nanopores, L2-ePt, was electrochemically investigated in embryo brain. For comparison study under precise control of electrochemical potential, we constituted an electrochemical cell beneath the embryo surface by introducing a flat and a nanoporous Pt twisted wires around which a Ag/AgCl wound. L2-ePt and flat Pt in the brain were compared with each other by conventional voltammetry and electrochemical impedance spectroscopy at the dc bias, which was carefully selected to minimize faradaic interference. The electrochemical behavior at L2-ePt implanted in embryo brain is immune to severe passivation and closer to an ideal capacitor than flat Pt. Lower electrode impedance of L2-ePt leads to less potential drop at the interface between the electrode and the extracellular solution, protecting the implanted system from unwanted faradaic reactions. Various aspects including the low electrode impedance and electrochemical stability of L2-ePt in the embryo brain suggest L2-ePt as a promising electrode material for effectively stimulating distant neuronal cells and recording local field potential signals.