Contrast of Highly Dispersed Metal Nanoparticles in High-resolution
                        Secondary Electron and Backscattered Electron Images of Supported Metal
                        Catalysts

Liu, Jingyue

doi:10.1007/s100050010033

Cited by 3 publications

(3 citation statements)

References 10 publications

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“…To verify our presumption, SEM and HRTEM characterizations were conducted. SEM images (Figure ) under different detector modes (LED/UED or BED-C) and distinct electron accelerating voltages (15.0 or 5.0 keV) can provide useful information about the morphology and distribution of particles positioned on or embedded in the carbon support because the penetration depth of electrons depends strongly on the detector as well as accelerating voltage (μm for BED-C mode, < 10 nm for LED/UED mode) . It is clear that significantly fewer nanoparticles were observed in the leached samples (Figure D, F) than that in the fresh one (Figure B), and more nanoparticles were detected under BED-C mode (Figure B, D, F) than that under UED mode (Figure A, C, E).…”

Section: Results and Discussionmentioning

confidence: 99%

Co–N–C Catalyst for C–C Coupling Reactions: On the Catalytic Performance and Active Sites

Zhang,

Wang,

Wang

et al. 2015

ACS Catal.

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309

222

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C−C bond-forming reactions are important in chemistry for construction of complex large molecules from readily available simple substrates. However, they usually involve the employment of organic halides and suffer from toxic or environmental issues. We report an efficient and environmentally benign methodologyaerobic oxidative cross-coupling of primary and secondary alcoholsto directly produce α,β-unsaturated ketones that are key intermediates for synthesis of agrochemical, pharmaceutical, and other fine chemicals. A noble-metal-free Co−N−C catalyst, derived from pyrolysis of cobalt−phenanthroline complexes on a mesoporous carbon support, is developed toward the target reactions and shows high catalytic activity (turnover frequency of 3.8 s −1 based on Co single atoms, surpassing the state of art in the literature), good recyclability, and wide applicability to diverse substrates (28 examples). The active sites in the Co−N−C catalyst are proposed to be Co single atoms bonded with N within graphitic sheets.

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Section: Results and Discussionmentioning

confidence: 99%

Co–N–C Catalyst for C–C Coupling Reactions: On the Catalytic Performance and Active Sites

Zhang,

Wang,

Wang

et al. 2015

ACS Catal.

Self Cite

309

222

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“…The size and location of the particles determine critically the performance of the catalyst. The characterization of such a system by scanning electron microscopy (SEM) imaging has been a powerful tool [1]. However, although small metal particles can be routinely observed in SEM images, the origin of the contrast of SEM images is complicated and is far from being fully understood [2,3].…”

Section: Introductionmentioning

confidence: 99%

“…Liu has recently performed a Monte Carlo simulation for the BSE signals generated from carbon supported Pt spheres [1]. A quantitative discussion on signal contrast for different beam energies, sphere sizes and depths in the support has revealed the complex nature of the contrast of small Pt particles in high-resolution BSE images of carbon supported Pt catalysts.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo simulation of secondary electron and backscattered electron images for a nanoparticle–matrix system

Yue¹,

Li²,

Ding³

2005

J. Phys. D: Appl. Phys.

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Contrast simulation of scanning electron microscope (SEM) images for particle–matrix systems is important for understanding the contrast formation mechanism in such systems. Most of the previous works have been limited to backscattered electron (BSE) signals because of the difficulties involved in the simulation of the secondary electron (SE) signals. This limitation prevents some important information from being extracted from experimental SEM images. A comprehensive and accurate Monte Carlo model has been developed for simulation of electron–solid interactions, which enables the simulation of production and emission of cascade SEs and is then quite suitable for investigating both SE and BSE signals. In this paper, we have modified the simulation model for a particle–matrix system and performed a simulation of SE and BSE images for nano-size Pt particles in a carbon matrix. Since the size of the particles is comparable with the electron scattering mean free path, modification of the conventional Monte Carlo procedure for a solid is necessary in order to include the boundary correction due to different scattering mean free paths. SE and BSE line scans and two-dimensional images under various conditions (particle size, depth and beam incident angle) are obtained and discussed in detail. The results have shown that: (1) In the formation of Pt–C contrast, the material factor plays a dominant role. (2) Only those particles located on, or quite close to, the matrix surface can be clearly revealed in a SE image. The maximum visible depth in SE observation for a Pt particle embedded in carbon matrix is about three times the particle size, while it is twice deeper than that with BSE signals. (3) The maximum SE emission from Pt particles appears at the centre of, instead of the sides of, the particle when the size falls down to the nanometre region; (4) Both the SE and BSE contrast have maximum values at a certain primary energy for particles of a specific size. (5) For oblique incidence of the primary beam, the SE contrast is quite different for the particles placed on the surface from that for those embedded in the matrix. These simulation results on image contrast will be helpful in evaluating the fraction of catalyst particles on the matrix surface and the optimum operating condition for imaging.

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Electron irradiation effects in transmission electron microscopy: Random displacements and collective migrations

Jiang

2023

Micron

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Contrast of Highly Dispersed Metal Nanoparticles in High-resolution Secondary Electron and Backscattered Electron Images of Supported Metal Catalysts

Cited by 3 publications

References 10 publications

Co–N–C Catalyst for C–C Coupling Reactions: On the Catalytic Performance and Active Sites

Co–N–C Catalyst for C–C Coupling Reactions: On the Catalytic Performance and Active Sites

Monte Carlo simulation of secondary electron and backscattered electron images for a nanoparticle–matrix system

Electron irradiation effects in transmission electron microscopy: Random displacements and collective migrations

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