QUANTUM-SIZE EFFECTS INDUCED BY CONFINEMENT OF C-60 IN MCM41

Siliceous mesoporous MCM-41 type solids of pore diameters 17 and 26 An gstrom have been used for occlusion of fullerene C-60 molecules by sub limation of C-60 at 873 K under vacuum. The resulting nanocomposite ex hibits quantum size effects in its electronic and magnetic properties. The C-60 adsorbed by the MCM-41 shows an intense ESR spectrum between 4 and 300K. The electron spin resonance linewidth is greater for the sample with pore diameter 17 than for that with diameter 26 Angstrom, suggesting that the linewidth is inversely dependent on the particle s ize. Furthermore, the linewidth shows no temperature dependence in the range 30 to 300K, indicating a quenching of the bulk C-60 relaxation mechanisms. The intensity of the signal obeys Curie's law over this ra nge. These effects are consistent with the modification of the electro nic band structure of the fullerene as a result of spatial confinement . Copyright (C) 1996 Elsevier Science Ltd