Electrochemical removal of oxygen and hydrogen from aqueous solution in the vicinity of gold electrodes, with simultaneous measurements of the response of the quartz crystal microbalance, show no evidence of gas nano-bubbles attached to the surface, irrespective of its roughness and hydrophobicity. The contact between gold and frozen electrolyte, which forms a liquid-like layer between them, also does not contain gas bubbles. These statements could be extended to nano-bubbles with characteristic dimensions larger than a few nanometers.

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A device allowing direct optical measurement of the displacement was employed to measure the thickness of the liquid-like layer. The data were correlated with calculations of the thickness based on admittance data of the quartz crystal microbalance, measured simultaneously. Agreement between the two independent measurements lends strong support for the validity of the models assumed in our calculations. The approach developed here allows the direct measurement of the thickness of the LLL in the range of a few tens up to few hundreds of nanometers.

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