Carbon thin films as electrode material in neural sensing

• We present a novel way of making sp2 and sp3 hybrid carbon material with varying conductivity.
• The carbon thin films had a wide potential window, which showed strong dependence on conductivity.
• Different adsorption behavior of the dopamine was observed between various surfaces.

For therapeutic purposes, an accurate measurement of dopamine levels in situ would be highly desirable. A novel strategy for the selective determination of dopamine concentrations based on carbon thin film electrodes is presented in this paper. Traditionally, in order to make diamond films conductive, they are doped with different concentration of boron atoms. Here, carbon thin films with varying conductivities were achieved by unbalanced magnetron sputtering. The benefit of the method is that it can be performed at room temperature consequently broadening the selection of suitable substrates. The carbon thin films had a wide potential window, which showed strong dependence on conductivity. The potential window was largest (4.6 V) with the most resistive carbon thin film. On the other hand, the sensitivity of the electrode toward dopamine was not significantly affected by the conductivity. In addition, relatively similar behavior with respect to the dopamine oxidation was observed between various surfaces. The slight differences observed in the electrochemical behavior among the thin films are most likely caused by 1) different conductivities and/or 2) different surface charges and subsequent differences in the chemical properties of the surfaces. In conclusion, it can be stated that a-C thin film is a very potential neural sensing material.