Fig. 3: IL-decoupled bulk/interfacial diffusion mechanism.

a Viscosity and surface tension of ionic liquid (IL) /water solutions of varied IL volume proportions. The error bars are standard deviation of three replicate measurements. b Theoretical bulk diffusion rates (D_b) of PIP molecules in the IL/water solutions of varied IL volume proportions. Insert in b: illustration of bulk PIP diffusion in the IL/water solution. The error bars are standard deviation of three replicate calculations. c, d Interfacial diffusion behavior of PIP molecules. c PIP free energy (ΔG) versus the z coordinates perpendicular to the interface of hexane and IL/water solutions. Insert in c: schematic illustration of the PIP movement pulled from IL/water solution to hexane solution. The initial coordinate is 2 nm away from the interface in the IL/water side and the total displacement is 4 nm. d Simulated interfacial diffusion coefficients of PIP (D_i) at varied IL volume proportions. e Calculated PIP diffusion amount (C_PIP) from the bulk IL/water solution to the opposite hexane side at varied IL volume proportions. C_PIP is calculated based on the above quantified diffusion coefficients, i.e., D_b and D_i. Starting PIP concentration is 100 mol m⁻³ and the cell sizes of hexane and IL/water solutions are both 100 nm ×1000 nm.