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Developing materials with improved photocatalytic activity is important for light energy conversion and storage within chemical bonds. Here we present a new type of hybrid film of silver nanoparticles (AgNPs) embedded within TiO x (x ≤ 2) to approach this goal, introducing visible light absorption via surface-plasmon excitation of the AgNPs. Silver nanoparticles were prepared by an ultrahigh vacuum (UHV) based buffer layer assisted growth method. The titania films as a substrate and protective layers were grown by the reactive layer assisted deposition (RLAD) technique; in both cases amorphous solid water (ASW) was the buffer material. The thin titania films and the AgNPs were ex situ characterized by UV−vis, micro-Raman, XRD, XPS, SEM, and TEM techniques. The titania protective layers on top of the silver particles were found to introduce a dielectric environment for the AgNPs, leading to a significant red-shift of their plasmon resonance from 460 to 530 nm, in addition to avoiding oxidation of the small nanoparticles. Photoinduced activity of these hybrid films has been tested following the degradation of methylene blue (MB) in aqueous solution under both UV and visible pulsed laser irradiation. Preliminary results have shown photocatalytic activity of the RLAD titania film with only marginal influence due to the presence of the AgNPs. Possible reasons for this observation are discussed.

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The temporal evolution of the OH stretching modes of a noncrystalline ice deposit upon annealing followed by crystallization near 160 K has been investigated by FT-IR reflection–absorption spectroscopy. Using the earlier theoretical results from Whalley (E. Whalley. Can. J. Chem. 55, 3429 (1977)) and from Buch and Devlin (V. Buch and J.P. Devlin. J. Chem. Phys. 110, 3437 (1999)), the most prominent changes in these modes have been characterized for the first time. A dynamical picture of the structural transformation during crystallization has been developed, and it supports the observation that crystallization proceeds directly from a noncrystalline to a crystalline state without any long-lived intermediate state structurally different from its noncrystalline predecessor.Key words: crystallization, noncrystalline ice, FT-IR reflection–absorption spectroscopy, temporary evolution.

Classical molecular dynamics (MD) simulations of Xe on the basal (0001) face of hexagonal ice at 180 K have been performed in order to investigate the mechanism of adsorption and the initial stage of absorption of a van der Waals particle into crystalline ice. The potential of mean force (PMF) as a function of the relative position of the Xe atom perpendicular to the ice surface is found to increase abruptly as the particle propagates from the disordered outermost region to the deeper hexagonally ordered region. A set of local minima observed in the PMF appears to correspond directly to the layer-by-layer crystal structure of hexagonal ice. Along with the unbound state, the first two minima (with similar free energies) that correspond to the accommodation of the guest particle on and inside the disordered outermost bilayer, respectively, are found to be populated during the MD runs. The multiple transitions of the system among these three states are also observed in accord with the PMF profile, which also suggests that the penetration of any ordered hexagonal bilayer by the Xe atom is unlikely. Furthermore, MD simulations of pristine ice (i.e., without Xe) over a 3-ns simulation period show that the initially perfect-ordered hexagonal crystalline structure of the outermost bilayer undergoes transformation to a noncrystalline phase, in which fragmented domains with hexagonal ordering persist. Moreover, the accommodation of the Xe atom inside the outermost bilayer could facilitate further disordering of the hexagonal structure of this bilayer with the formation of a completely disordered Xe-ice surface phase.