Fig. 4. Tuning the subnanometer pores of the AlO_x membranes for molecular sieving.

Schematic diagrams of a ethanol-modulated and b isopropanol-modulated ALD deposition. Both processes consist of four steps: (1) TMA pulse; (2) TMA purge; (3) co-reactant pulse (a mixture of H₂O and ethanol for ethanol-modulated process, and a mixture of H₂O and isopropanol for isopropanol-modulated process); and (4) co-reactant purge. c Water permeability coefficient of the AlO_x membranes fabricated with methanol, ethanol, and isopropanol as co-reactants. In each measurement, 1 M NaCl was utilized as the concentrated solution and DI water was used on the dilute side. Error bars represent standard deviations from measurements with three membranes. d Permeation rate of neutral solutes through the AlO_x membranes with tunable subnanometer pores. For each test, 0.1 M single solute solutions were placed on the concentrated side and the permeation rate was calculated by measuring the TOC increase on the permeate side. Error bars represent standard deviations from measurements with at least two membranes. e Amplification of the solute flux through the AlO_x membranes fabricated with methanol in d.