Evolution of dynamical motions in monolayer protected metal-clusters

Abstract

Here we report orientational dynamics in monolayer protected metal-cluster (MPC) systems as studied by quasielastic neutron scattering (QENS) technique. Experiments carried out using two different instruments having very different energy windows, thus covering a time scale of 10^-9-10^-12 s. Clear evidence of absence of 'rotator phase' has been found in isolated MPCs (Au-SC₁₈H₃₇, Au-SC₁₂H₂₅, Au-SC₈H₁₇ and Au-SC₆H₁₃), a superlattice MPC (Ag-SC₁₈H₃₇) as well as planar thiolates (Ag-SC₆H₁₃, Ag-SC₁₂H₂₅, Ag-SC₁₈H₃₇) at room temperature. However, dynamics were found to evolve on increase of temperature and its behaviour is found to be different in the superlattice and isolated cluster systems. Detailed dynamical informations for MPCs are obtained for the first time in these systems.