Fig. 4: The influence of TBO concentration and the choice of intercalated molecules on the barrier performance of the as-fabricated films.

a, b Measured normalized conductivity of Ca films at 25 °C and 45% RH, covered by double-layer graphene intercalated by TBO with different concentrations, as a function of measurement time (a) and the summary of the obtained WVTR values as a function of TBO concentrations (b). The data were presented as the means ± SD, n = 3. c Calculated adsorption energies and structures of water molecules adsorbed on pristine graphene, hydroxyl-decorated graphene (Gr.-OH) and hydroxyl-decorated graphene surface with backside fluorination (F-Gr.-OH). d Calculated friction coefficients in x (zigzag), y (armchair) direction, and the average friction coefficient value of graphene with 0.12 % hydroxylation within 1 ns simulation calculated by the Green-Kubo equation. Inset: schematic illustration of the structure containing water molecules and double-layer graphene for MD simulation. e The obtained slip length of water molecules on graphene with 0%, 0.12 %, 0.28%, 0.42%, and 0.56% hydroxylation. f The adsorption energies of H₂O with TBO, pyrenyl-1-boronic acid pinacol ester (PBA), 1-phenyl-1H-benzo[d]imidazol-2(3H)-one (PBI), 4,5-diazafluoren-9-one (DAFO) and sulfinpyrazone. White, pink, black, blue, red, pale blue, orange, and cyan balls are the H, B, C, N, O, F, S, and Cl atoms, respectively. g–j Measured conductivity of Ca films as a function of measurement time. Note that the Ca films are covered by double-layer graphene films that were intercalated by PBA (g), PBI (h), DAFO (i), and sulfinpyrazone molecules (j).