Integrated Computational and Experimental Structure Refinement for Nanoparticles

Determining the three-dimensional (3D) atomic structure of nanoparticles is critical to identifying the structures controlling their properties. Here, we demonstrate an integrated genetic algorithm (GA) optimization tool that refines the 3D structure of a nanoparticle by matching forward modeling to experimental scanning transmission electron microscopy (STEM) data and simultaneously minimizing the particle energy. We use the tool to create a refined 3D structural model of an experimentally observed ∼6000 atom Au nanoparticle

Integrated Computational and Experimental Structure Refinement for Nanoparticles

Determining the three-dimensional (3D) atomic structure of nanoparticles is critical to identifying the structures controlling their properties. Here, we demonstrate an integrated genetic algorithm (GA) optimization tool that refines the 3D structure of a nanoparticle by matching forward modeling to experimental scanning transmission electron microscopy (STEM) data and simultaneously minimizing the particle energy. We use the tool to create a refined 3D structural model of an experimentally observed ∼6000 atom Au nanoparticle

Integrated Computational and Experimental Structure Refinement for Nanoparticles

Determining the three-dimensional (3D) atomic structure of nanoparticles is critical to identifying the structures controlling their properties. Here, we demonstrate an integrated genetic algorithm (GA) optimization tool that refines the 3D structure of a nanoparticle by matching forward modeling to experimental scanning transmission electron microscopy (STEM) data and simultaneously minimizing the particle energy. We use the tool to create a refined 3D structural model of an experimentally observed ∼6000 atom Au nanoparticle

Integrated Computational and Experimental Structure Refinement for Nanoparticles

Determining the three-dimensional (3D) atomic structure of nanoparticles is critical to identifying the structures controlling their properties. Here, we demonstrate an integrated genetic algorithm (GA) optimization tool that refines the 3D structure of a nanoparticle by matching forward modeling to experimental scanning transmission electron microscopy (STEM) data and simultaneously minimizing the particle energy. We use the tool to create a refined 3D structural model of an experimentally observed ∼6000 atom Au nanoparticle

Ionic Layer Epitaxy of Nanometer-Thick Palladium Nanosheets with Enhanced Electrocatalytic Properties

Large surface area-to-volume ratio with plenty of accessible electrochemically active sites presents metal nanosheets a highly efficient catalyst material. However, a facile and effective synthesis of metal nanosheets with nanoscale thicknesses, macroscopic sizes, and desired crystal facets is still a grand challenge. Here, we report the synthesis of free-standing Pd nanosheets by ionic layer epitaxy (ILE), which employs a cationic oleylamine monolayer at the water–air interface as a soft template to guide the nanosheet growth. The Pd nanosheets exhibited a quasi-square morphology with a uniform thickness of ∼2 nm and sizes ranging from 1 to 6 μm. Owing to the extremely large surface-to-volume ratio and the exposure of mixed surface crystal facets, the Pd nanosheets exhibited high activity in formic acid oxidation compared to the commercial Pd black and other reported Pd nanostructures. This work presents a simple and effective way to prepare metal nanosheets with nanometer-scale thickness control

Atomic Layer Epitaxy of h‑BN(0001) Multilayers on Co(0001) and Molecular Beam Epitaxy Growth of Graphene on h‑BN(0001)/Co(0001)

The direct growth of hexagonal boron nitride (h-BN) by industrially scalable methods is of broad interest for spintronic and nanoelectronic device applications. Such applications often require atomically precise control of film thickness and azimuthal registry between layers and substrate. We report the formation, by atomic layer epitaxy (ALE), of multilayer h-BN(0001) films (up to 7 monolayers) on Co(0001). The ALE process employs BCl₃/NH₃ cycles at 600 K substrate temperature. X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) data show that this process yields an increase in h-BN average film thickness linearly proportional to the number of BCl₃/NH₃ cycles, with BN layers in azimuthal registry with each other and with the Co(0001) substrate. LEED diffraction spot profile data indicate an average BN domain size of at least 1900 Å. Optical microscopy data indicate the presence of some domains as large as ∼20 μm. Transmission electron microscopy (TEM) and ambient exposure studies demonstrate macroscopic and microscopic continuity of the h-BN film, with the h-BN film highly conformal to the Co substrate. Photoemission data show that the h-BN(0001) film is p-type, with band bending near the Co/h-BN interface. Growth of graphene by molecular beam epitaxy (MBE) is observed on the surface of multilayer h-BN(0001) at temperatures of 800 K. LEED data indicate azimuthal graphene alignment with the h-BN and Co(0001) lattices, with domain size similar to BN. The evidence of multilayer BN and graphene azimuthal alignment with the lattice of the Co(0001) substrate demonstrates that this procedure is suitable for scalable production of heterojunctions for spintronic applications

Metastable Intermediates in Amorphous Titanium Oxide: A Hidden Role Leading to Ultra-Stable Photoanode Protection

Metastable intermediates represent a non-equilibrium state of matter that may impose profound impacts to materials properties beyond our understandings of monolithic and equilibrium systems. Here, we report a discovery of hidden metastable intermediates in amorphous TiO₂ thin films and their critical role in electrochemical damage. These intermediates have a non-bulk crystal-like structure and exhibit significantly higher electrical conductivity than both the amorphous and the crystalline phases. When these TiO₂ films are applied to protect Si photoelectrochemical (PEC) photoanodes, the intermediates can induce localized high electrical currents that largely accelerate the etching of the TiO₂ film and the Si electrode underneath. The intermediates can be effectively suppressed by raising their nucleation barrier via reducing the film thickness from 24 to 2.5 nm. The homogeneous amorphous TiO₂-film-coated Si photoanodes achieved more than 500 h of PEC water oxidation at a steady photocurrent density of over 30 mA·cm^–2

Pore Structure and Bifunctional Catalyst Activity of Overlayers Applied by Atomic Layer Deposition on Copper Nanoparticles

We present a model system, based on spherical nonporous supports, to facilitate the characterization of supported metal catalysts stabilized by atomic layer deposition (ALD) against sintering and leaching under liquid-phase conditions. Calcination at high temperatures (973 K) produces pores in the ALD overcoat, and we image these pores using scanning transmission electron microscopy and electron energy loss spectroscopy (STEM/EELS). We determine the size of these pores to be ∼1 nm using small-angle X-ray scattering (SAXS). Finally, we demonstrate the use of ALD to synthesize novel bifunctional catalysts by the addition of an acidic oxide layer to the stabilizing overcoat