Subnanoparticles (SNPs) with ultrasmall particle sizes (<1 nm) have potential to provide catalytic activity that is superior to that of nanoparticles. Size-controlled Cu n O x (n = 12, 28, and 60) materials supported on zirconia, prepared using a dendritic macromolecular reactor, exhibited increased ionicity of the Cu−O bonds with a decrease in size of the particles, which was suggested on the basis of the peak intensity in the Cu 2p 3/2 region. The polarization of the Cu−O bonds in the ultrasmall copper oxides provides size-dependent catalytic activity in aerobic oxidation of the CH 3 group bonded with aromatic rings. The smallest Cu 12 O x materials achieved an excellent large turnover number (TON = 40 206) without any significant deactivation.
Subnanoparticles (SNPs) with sizes of approximately 1 nm are attractive for enhancing the catalytic performance of transition metals and their oxides. Such SNPs are of particular interest as redox‐active catalysts in selective oxidation reactions. However, the electronic states and oxophilicity of copper oxide SNPs are still a subject of debate in terms of their redox properties during oxidation reactions for hydrocarbons. In this work, in situ X‐ray absorption fine structure (XAFS) measurements of Cu28Ox SNPs, which were prepared by using a dendritic phenylazomethine template, during temperature‐programmed reduction (TPR) with H2 achieved lowering of the temperature (T50=138 °C) reported thus far for the CuII→CuI reduction reaction because of Cu−O bond elongation in the ultrasmall copper oxide particles.
Atomic arrangements and their symmetries govern the physical
properties
of materials, including nanosheets that are low-dimensional nanomaterials.
Although they have the same composition, symmetric changes associated
with atomic displacements sometimes induce unexpected physical properties.
Herein, we report that symmetric breakage induces a semimetallic state
in chemically exfoliated ruthenate nanosheets. The atomic arrangements
and symmetries are determined by a pair distribution function (PDF);
subsequently, the physical properties are discussed using ab initio
calculations and resistivity measurements. Ruthenate nanosheets can
adopt an electronic structure similar to that of graphene owing to
symmetric breakage. We experimentally confirmed the polymorphism in
ruthenate nanosheets that highlights the importance of symmetric analysis,
even in low-dimensional materials.
Finely size-controlled ultrasmall iron oxide particles (IOPs) on graphene nanosheets were usefully prepared by using pulsed arc plasma deposition. The IOPs are composed of a high crystallinity single γ-Fe2O3 component without annealing.
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