Polymerization in ferrocene-doped C60 nanosheets under high pressure and light irradiation

In this study, pressure-induced transformation in ferrocene (Fc)–doped C60 nanosheets containing alternating layers of C60 and Fc is investigated using in situ Raman spectroscopy. In particular, the change in the Ag(2) mode of C60, which is very sensitive to the state of C60 in the crystals, is examined at pressures up to 12.5 GPa. Orientational ordering and polymerization, mainly one-dimensional (1D) polymerization, in the C60 layers are observed with increasing pressure. High pressure can also lead to the formation of higher-order polymers, such as two-dimensional or branched 1D polymers, similar to parts of molecular arrangement in C60 layers. Such transformations are reversible with pressure. Notably, pressure-induced polymerization, mainly 1D polymerization, is promoted and stabilized by light irradiation. In addition, under high pressure, higher-order polymers can be broken and reformed as stabilized 1D polymers via light irradiation. Under pressure, photo-induced 1D polymerization is irreversible. Thus, light irradiation can allow more stable polymers or 1D photo-polymers even under high pressure.