Using buckyballs to cut off light! novel fullerene materials with unique optical transmission characteristics

A simple rule governing the light transmission through a fullerene solution or solid is revealed, and a group of fullerene derivatives, glasses, and polymers are found to be able to continuously cut off lights of any wavelength in almost the entire UV and visible spectral region in a predictable and reliable manner. The solutions of aminated fullerenes 1-4 give structureless light transmission spectra well-resembling those of cutoff optical filters. The spectrum bathochromically moves with an increase in concentration (c), whose cutoff wavelength (λ_c) increases logarithmically with bc, i.e., λ_c = γ log bc + k, where b is the path length and α and k are constants. The spectra are reproducible and stable, changing little over a long period of time. In the solutions, the fullerene molecules aggregate into nanoclusters and their average sizes increase with increasing concentration, suggesting that the formation and growth of the fullerene nanoaggregates are responsible for the concentratochromism. The chromic effects are also observed in the solid state: the transmission spectra of the fullerenated glasses and polymers 5-7 all red shift with increasing C ₆₀ content. The spectrum of the parent polymer virtually does not vary with concentration, proving that the buckyball is the origin of the novel concentratochromism.