Mesoporous gold electrodes for sensors based on electrochemical double layer capacitance

The use of mesoporous gold as electrode material for measurement of electrochemical capacitance is investigated. The electrodes possess a pore size in the range of 10–30 nm and are prepared by de-alloying films of AuAlx, where x ≥ 2. Analyses conducted with X-ray photoelectron spectra (XPS) show that their surfaces are essentially pure gold, with only traces of aluminium remaining. The electrodes show near-ideal capacitor behaviour under both cyclic voltammetry and potential-step conditions. The higher capacitance of the mesoporous electrodes leads to a better dynamic range in potential-step experiments, resulting in improved accuracy of measurement. The sensitivity of the new material as a capacitive sensor is demonstrated in a milk fouling experiment, and is improved by up to 30 times compared to the control sample of ordinary planar gold. We propose that the use of mesoporous gold electrodes offers a convenient way to sensitively and accurately amplify the capacitance signal of an electrochemical sensor.