Characterization of gold electrodes in phosphate buffered saline solution by impedance and noise measurements for biological applications

Impedance spectroscopy and noise measurements have been used to study gold electrodes of three different surface areas in phosphate buffered saline (PBS) solution. The gold-PBS solution interface can be modeled by a charge transfer resistance in parallel with an interfacial constant phase element (CPE) which are in series with the solution resistance. The voltage noise fluctuations were analyzed using the fast Fourier transform (FFT) method. It is found that the voltage noise power is characterized by a 1/f(alpha) spectrum in the low frequency range. The value of alpha is observed to be double that of the CPE coefficient beta. The authors suggest a link between the interface impedance and the measured noise.