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Abstract:
Nanometal particles show characteristic features in chemical and
physical properties depending on their sizes and shapes. For keeping and
further enhancing their features, the particles should be protected from
coalescence or degradation. One approach is to encapsulate the nanometal
particles inside pores with chemically inert or functional materials,
such as carbon, polymer, and metal oxides, which contain mesopores to
allow permeation of only chemicals not the nanometal particles. Recently
developed low-voltage high-resolution scanning electron microscopy was
applied to the study of structural, chemical, and electron state of both
nanometal particles and encapsulating materials in york-shell materials
of Au@C, Ru/Pt@C, Au@TiO2, and Pt@Polymer. Progresses in the following
categories were shown for the york-shell materials: (i) resolution of
topographic image contrast by secondary electrons, of atomic-number
contrast by back-scattered electrons, and of elemental mapping by X-ray
energy dispersive spectroscopy; (ii) sample preparation for observing
internal structures; and (iii) X-ray spectroscopy such as soft X-ray
emission spectroscopy. Transmission electron microscopy was also used
for characterization of Au@C.
