The growth of graphene on single crystal Cu(111) has been achieved by thermal decomposition of ethylene in an ultrahigh vacuum chamber for the first time. The structural and electronic properties of graphene on Cu(111) have been investigated by scanning tunneling microscopy and spectroscopy. The nucleation of monolayer islands and two predominant domain orientations have been observed, which lead to the formation of numerous domain boundaries with increasing coverage. These results reveal that reducing the density of domain boundaries is one challenge of growing high-quality graphene on copper.
Heterogeneous catalysis involves solid-state catalysts, among which metal nanoparticles occupy an important position. Unfortunately, no two nanoparticles from conventional synthesis are the same at the atomic level, though such regular nanoparticles can be highly uniform at the nanometer level (e.g., size distribution ∼5%). In the long pursuit of well-defined nanocatalysts, a recent success is the synthesis of atomically precise metal nanoclusters protected by ligands in the size range from tens to hundreds of metal atoms (equivalently 1−3 nm in core diameter). More importantly, such nanoclusters have been crystallographically characterized, just like the protein structures in enzyme catalysis. Such atomically precise metal nanoclusters merge the features of well-defined homogeneous catalysts (e.g., ligand-protected metal centers) and enzymes (e.g., protein-encapsulated metal clusters of a few atoms bridged by ligands). The well-defined nanoclusters with their total structures available constitute a new class of model catalysts and hold great promise in fundamental catalysis research, including the atomically precise size dependent activity, control of catalytic selectivity by metal structure and surface ligands, structure−property relationships at the atomic-level, insights into molecular activation and catalytic mechanisms, and the identification of active sites on nanocatalysts. This Review summarizes the progress in the utilization of atomically precise metal nanoclusters for catalysis. These nanocluster-based model catalysts have enabled heterogeneous catalysis research at the single-atom and single-electron levels. Future efforts are expected to achieve more exciting progress in fundamental understanding of the catalytic mechanisms, the tailoring of active sites at the atomic level, and the design of new catalysts with high selectivity and activity under mild conditions.
Coreshell-like Ag2 O/Ag2 CO3 nanoheterostructures with tailored interface are fabricated by a facile, low-cost and one-step phase transformation method. The unique bandgap structure of the Ag2 O/Ag2 CO3 exhibits high separation efficiency of photogenerated electrons and holes, which effectively protects the Ag2 CO3 semiconductor to avoid its photoreduction and gives rise to high activity and stability in degradation of the typical water pollutants.
Kondo resonances are a very precise measure of spin-polarized transport through magnetic impurities. However, the Kondo temperature, indicating the thermal range of stability of the magnetic properties, is very low. By contrast, we find for iron phthalocyanine a Kondo temperature in spectroscopic measurements which is well above room temperature. It is also shown that the signal of the resonance depends strongly on the adsorption site of the molecule on a gold surface. Experimental data are verified by extensive numerical simulations, which establish that the coupling between iron states and states of the substrate depends strongly on the adsorption configuration.
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