Gold clusters are extremely interesting nanosystems with a high catalytic activity, exploited for sensing applications and to promote the growth of nanostructures [1,2]. All these potential applications motivated numerous structural studies on Au nano-clusters. The mean electrostatic potential (MIP) is a fundamental quantity and its value is crucial for accurate evaluation and simulation of experimental data from TEM imaging and electron diffraction. Recently, a dependence of the MIP on particle size has been reported, measured by electron holography (EH): the increase of the MIP over the bulk value for particle sizes lower than 5 nm has been shown, suggesting a correlation with the catalytic behaviour of gold [3,4]. Despite these very promising results, a similar effect was observed in amorphous carbon films as the result of a thickness independent phase shift [5]. EH is capable of providing a quantitative …