Three-dimensional aggregation of fullerene C60 at the air–water interface

This paper seeks to get a mechanistic insight into homomolecular aggregation of fullerenes in low-dimensional systems. For this purpose, the forced aggregation of fullerene C60 on two subphases (pristine water and aqueous 1% NaCl solution) has been studied by analysis of the compression curves and Brewster angle microscopy (BAM). The analysis indicates that the highest ordered structure being achievable upon multi-cycle compression is the C60 hexalayer. The lower aggregation stages are directly observable by BAM. The floating layers are stated to be organized as a binary colloid system C60–H2O, where the C60 component behaves as a guest initially but becomes a host towards the tetralayer stage. In turn, the H2O component inhibits the structural collapse and promotes the smooth vertical growth of the C60 aggregates. The polylayers exhibit a variety of morphological features, both aggregated species and structural defects, whose evolution is discussed in terms of the vertical and lateral phase separation.

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► Using cyclohexene as a spreading solvent, we prepared the highly homogeneous 2D system C60–H2O.
► On water, the system suffers the vertical phase separation into the C60 polylayers and free water.
► On saline, the holed and pitted C60 polylayers arise because of the lateral phase separation.