Kinematic HAADF-STEM image simulation of small nanoparticles

He, Dongsheng; Li, Ziyou; Yuan, Jun

doi:10.1016/j.micron.2015.04.005

Cited by 28 publications

(18 citation statements)

References 38 publications

(47 reference statements)

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“…The width of the Gaussian, σ, is chosen to have the value 0.78Å as was deduced by Li et al from their experimental AC-STEM data on Au nanoclusters [7]. A similar value, 0.8Å, was deduced by He et al [19].…”

Section: Methodsmentioning

confidence: 85%

Nanocluster structure deduced from AC-STEM images coupled to theoretical modelling

Sukuta¹,

Bossche²,

Pedersen³

et al. 2017

Nanosystems: Phys. Chem. Math.

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Determining the atomic structure of nanoclusters is a challenging task and a critical one for understanding their chemical and physical properties. Recently, the high resolution aberration corrected scanning transmission electron microscope (AC-STEM) technique has provided valuable information about such systems, but the analysis of the experimental images has typically been qualitative rather than quantitative. A method is presented for detailed analsis of AC-STEM images combined with theoretical modelling to extract atomic coordinates. An objective function formed by a linear combination of a fit to the two-dimensional AC-STEM image plus an estimate of the cluster's energy for adding information about the third dimension is used in a global optimization algorithm to extract the atomic coordinates. The method is illustrated by analyzing model images generated for the Garzón structure of the Au 55 cluster, which is a metastable structure for the embedded atom method (EAM) potential function used here to estimate the total energy. As the method does not rely on the alignment of atom rows in the AC-STEM image, the partially disordered chiral structure of the Au 55 can successfully be determined even when a significant level of noise is added to the images.

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Section: Methodsmentioning

confidence: 85%

Nanocluster structure deduced from AC-STEM images coupled to theoretical modelling

Sukuta¹,

Bossche²,

Pedersen³

et al. 2017

Nanosystems: Phys. Chem. Math.

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“…HAADF-STEM images are captured with an electron probe size of 8 C and a pixel dwell time of 38 μs with a 512 × 512 pixel scanning area. Atomic simulation environment (ASE) 35 is used to generate the atomic models of Pt nanoparticles used in the kinetic simulation of the HAADF-STEM images of Pt nanoparticles 36 . For shape identification, the structural models used in Fig.…”

Section: Methodsmentioning

confidence: 99%

Shape control of size-selected naked platinum nanocrystals

et al. 2021

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Controlled growth of far-from-equilibrium-shaped nanoparticles with size selection is essential for the exploration of their unique physical and chemical properties. Shape control by wet-chemistry preparation methods produces surfactant-covered surfaces with limited understanding due to the complexity of the processes involved. Here, we report the controlled production and transformation of octahedra to tetrahedra of size-selected platinum nanocrystals with clean surfaces in an inert gas environment. Molecular dynamics simulations of the growth reveal the key symmetry-breaking atomic mechanism for this autocatalytic shape transformation, confirming the experimental conditions required. In-situ heating experiments demonstrate the relative stability of both octahedral and tetrahedral Pt nanocrystals at least up to 700 °C and that the extended surface diffusion at higher temperature transforms the nanocrystals into equilibrium shape.

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“…STEM simulation: Atomically-resolved HAADF STEM image simulation was performed with the STEM simulation software developed by He, Li and Yuan using Matlab 7.12.0.635 (R2011a). [42] This software assumes kinetic scattering of the electrons (i.e. the incident electrons are only scattered once) by the atoms of the structure under consideration.…”

Section: Methodsmentioning

confidence: 99%

Revealing Size Dependent Structural Transitions in Supported Gold Nanoparticles in Hydrogen at Atmospheric Pressure

Nassereddine

Wang

Loffreda

et al. 2021

Small

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activity of Au NPs with size smaller than 5 nm has been often attributed to sizedependent physical features such as the fraction of surface atoms. [5][6][7] For instance, in reactions of hydrogenation, it is widely accepted that surface atoms on small particles are much more active than those on large particles since the fraction of low coordinated sites, that is, at edges and corners, which are the hydrogen activation sites, increases when size decreases. [8][9][10][11] This concept has been largely adopted for studying the reactivity of Au NPs, especially by theoreticians and surface science researchers. [12] The common practice is to consider Au nanoparticles as perfect model crystals with well-defined symmetry and static surface facets interacting with low coverage of gas molecules. However, the effect of adsorbates, which induces surface changes, is generally neglected in these studies. [13][14][15] This is a serious drawback that may prevent reliable description of the catalyst reactivity that mainly depends on the configuration of the surface. Aside from structural effects, quantum size effects are also frequently invoked to explain the exceptional activity of Au NPs. [16,17] For instance, using Density Functional Theory, Illas et al. have reported that the minimum energy pathway of O 2 dissociation for different Au NPs is chemically similar whichThe enhancement of the catalytic activity of gold nanoparticles with their decreasing size is often attributed to the increasing proportion of low-coordinated surface sites. This correlation is based on the paradigmatic picture of working gold nanoparticles as perfect crystal forms having complete and static outer surface layers whatever their size. This picture is incomplete as catalysts can dynamically change their structure according to the reaction conditions and as such changes can be eventually size-dependent. In this work, using aberration-corrected environmental electron microscopy, size-dependent crystal structure and morphological evolution in gold nanoparticles exposed to hydrogen at atmospheric pressure, with loss of the face-centered cubic crystal structure of gold for particle size below 4 nm, are revealed for the first time. Theoretical calculations highlight the role of mobile gold atoms in the observed symmetry changes and particle reshaping in the critical size regime. An unprecedented stable surface molecular structure of hydrogenated gold decorating a highly distorted core is identified. By combining atomic scale in situ observations and modeling of nanoparticle structure under relevant reaction conditions, this work provides a fundamental understanding of the size-dependent reactivity of gold nanoparticles with a precise picture of their surface at working conditions.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202104571.

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Kinematic HAADF-STEM image simulation of small nanoparticles

Cited by 28 publications

References 38 publications

Nanocluster structure deduced from AC-STEM images coupled to theoretical modelling

Nanocluster structure deduced from AC-STEM images coupled to theoretical modelling

Shape control of size-selected naked platinum nanocrystals

Revealing Size Dependent Structural Transitions in Supported Gold Nanoparticles in Hydrogen at Atmospheric Pressure

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