Thermodynamic properties of pinned nanobubbles

We present molecular dynamics simulations to study the thermodynamics of nanobubbles trapped at the mouth of narrow slit pores. Except when the slit dimensions are comparable to typical molecular sizes, the predictions of macroscopic thermodynamic theory are recovered by our simulations. Our simulations confirm that in this case, the internal pressure of stable nanobubbles is independent of the bubble radius and the surface tension and only depends on the bulk properties of the solute-containing solution, i.e., the chemical potential balance. However, in the case of extreme confinement, the pressure is not a suitable quantity to describe the thermodynamics of the bubbles, while the balance of the chemical potentials is.