It has been reported previously that nanobubbles in LP-TEM investigations of HAuCl4 solutions can etch gold nanostructures. It was concluded that this can only be related to reactive chlorine species within the gas phase, which can cause gold etching. The high concentration of HCl predicted by the kinetic simulations performed within this work fits well with this observation, as HCl is known to be volatile. The formation of gaseous halide species has been reported for different ionizing radiations, as well. It is noteworthy that this phenomenon appears regularly, as shown in Figure . Here, a gold nanostructure is etched when directly contacting gas bubbles. If the gas bubble would mainly contain hydrogen, a passivation of the particle is expected to inhibit oxidative etching. In succession to etching, gold nanoparticles precipitate spatially isotropically in the vicinity of the gas bubbles (Figure )). This is a strong indication of gaseous gold-containing species, because only a gold-transfer mechanism via the gaseous phase explains the isotropic appearance of the gold particles beneath the bubble. This fits well to the predicted formation of Au2Cl6 2-, as such structures have already been reported to exist in gas phase previously. They could therefore cause such a nucleation behavior upon re-dissolution and supersaturation in the interfacing liquid.