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PRINCIPAL PUBLICATION AND AUTHORS

De Novo Synthesis of Free-Standing Flexible 2D Intercalated Nanofilm Uniform over Tens of cm2, P. Ravat (a), H. Uchida (a), R. Sekine (a), K. Kamei (a), A. Yamamoto (b), O. Konovalov (c), M. Tanaka (b,d), T. Yamada (a), K. Harano (a), E. Nakamura (a), Adv. Mater. 34(22), e2106465 (2022); https:/doi.org/10.1002/adma.202106465 (a) Department of Chemistry, The University of Tokyo (Japan) (b) Institute for Advanced Study, Kyoto University (Japan) (c) ESRF (d) Institute of Physical Chemistry, Heidelberg University (Germany)

REFERENCES

[1] W. Abuillan et al., J. Am. Chem. Soc. 140, 11261-11266 (2018).

Fig. 57: a) XRR and GIWAXS at the air/water interface. b) Reconstructed scattering length density profile of CFA nanofilms on the water surface. c) CFA films transferred on a gold comb-electrode exhibited proton

conductivity through a 2D hydrogen-bonded network.

to reflect the near-C5 symmetry. Intriguingly, the scattering length density (SLD) profile reconstructed from the best-fit result (Figure 57b) indicated that the film consists of a denser bottom layer in contact with water, flanked by a less dense upper layer. Although the CFA possesses an amphiphilic structure, the total film thickness of 22 - 23 Å suggests that CFA forms a bilayer, sandwiching carboxylic acid legs [1]. Notably, the formation of a hydrophobic fullerene bilayer on the water surface occurs via dissipative solvent quenching, which is distinct from the construction of a monolayer by an excess majority of organic surfactant molecules, which requires compression to achieve a high lateral order.

The entangled, hydrogen-bonded network between two fullerene layers forms a unique 2D hydrophilic channel that serves as a pathway for proton transfer. The double

bilayers of CFA transferred on a gold comb-electrode (5-µm-gap on quartz glass, Figure 57c) exhibited proton conduction as high as 10 4 S/cm at 95% relative humidity. Fourier Transform Infrared Spectroscopy (FTIR) demonstrated that the high proton conductivity could be explained by the formation of hydrogen-bonded networks in CFA films that could not be detected for CFA powders.

In summary, an operationally simple, de novo synthesis of an intercalated nanofilm at the air/water interface showed unique structural and physicochemical properties that could not be achieved by commonly taken top-down/bottom-up approaches. The unique material properties of the nanofilms, such as structural uniformity over tens of cm2, outstanding mechanical robustness and fast proton conductivity, suggest a wide range of applications in materials science.