Fractal Aggregations at Low Driving Force with Strong Anisotropy

Wang, Mu; Liu, Xiaoyong; Strom, C.S.; Bennema, P.; Enckevort, Willem van; Ming, Nai‐Ben

doi:10.1103/physrevlett.80.3089

Cited by 52 publications

(59 citation statements)

References 24 publications

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“…In our experiments, the sealed autoclave provided a high reaction temperature and high pressure environment for growth. Such unstable and oscillating experimental conditions may stimulate new nucleus to appear at the tips of the existing seeds, where the growth is significantly favored because of the advantageous location for obtaining the crystal-grown precursors [48][49][50]. The successive nucleation process followed the crystallographic orientation related to the crystal anisotropy of the noble metal.…”

Section: Resultsmentioning

confidence: 99%

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Synthesis of single-crystal hyperbranched rhodium nanoplates with remarkable catalytic properties

Zhang

Chen

et al. 2017

Sci. China Mater.

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The catalytic properties of noble metal nanocrystals can be tuned via engineering their structures. Nanocrystals with fractal structures are fascinating catalysts regarding their large surface area-to-volume ratios, large numbers of edges and corners, which can be tuned simultaneously by their hierarchical ordering. However, it is still a great challenge to control the hierarchical ordering of noble metal fractal nanocrystals and their formation mechanism is not fully understood. Herein, we report a facile solvothermal method for the direct preparation of a unique single-crystal Rh-hyperbranched structure, which consists of hierarchically ultrathin nanoplates with threefold symmetry, large surface area and high density of low-coordinated edge/corner sites. Importantly, the hierarchical ordering can be readily tuned by changing the composition of solvent. In addition, we found the as-prepared single-crystal hyperbranched Rh nanoplates possessed great structure stability, and exhibited better catalytic performance towards both ethanol electrooxidation and hydrogenation of styrene than the commercial Rh black, which can be attributed to the large surface area and high-dentisty of edge/corner sites.

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Section: Resultsmentioning

confidence: 99%

“…The successive nucleation process followed the crystallographic orientation related to the crystal anisotropy of the noble metal. Thus, a fractal structure with anisotropy was obtained during the diffusion-limited growth process, which was defined as the nucleation-limited aggregation growth [48][49][50].…”

Section: Resultsmentioning

confidence: 99%

Synthesis of single-crystal hyperbranched rhodium nanoplates with remarkable catalytic properties

Zhang

Chen

et al. 2017

Sci. China Mater.

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“…In this way, a pattern with welldefined long-range-order emerges and can be observed. 8,9 As we pointed out earlier, this phenomenon is not limited to the growth of NH 4 Cl only. A similar phenomenon has been observed in the crystallization of CsCl, 12 Ba(NO 3 ) 2 , FeSO 4 , etc.…”

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confidence: 95%

“…Thereafter the angle θ eq is held. θ eq is determined by ∆θ* ) 0, according to eq 10 Once θ eq is reached, the crystallographic orientation of subsequently grown crystalline layers will not be changed anymore; hence, the long-range-ordering phenomena as that reported before [7][8][9] will not be observable on large scale. However, in some cases, before θ eq is reached, reconstruction of crystalline facet may take place for the sake of minimizing the total interfacial energy, and hence new contact angle appears.…”

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confidence: 99%

“…Indeed, it has been observed that, during lateral growth of NH 4 Cl crystallite on a glass plate, the crystallographic orientation is continuously rotated, leading to either a periodic distribution of faceted regions and roughened regions 7 or a regular zigzag branches. 8,9 The appearance of the specific morphology depends on the index of the initial crystalline facet contacting the substrate and the axis of rotation. 9 Another example is the crystallographic wing tilt commonly observed in lateral overgrowth, 10,11 which is generally ascribed to the substrate effect.…”

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Nucleation-Mediated Lateral Growth on Foreign Substrate

et al. 2006

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A model is developed to deal with lateral growth of a crystalline layer on a foreign substrate, which is mediated by successive nucleation at the concave corner defined by the meeting of a crystal facet and the substrate. It is demonstrated that due to an imbalance of surface/interface tensions at the concave corner, once the embryo of a nucleus is formed, the crystallographic orientation of the nucleus is spontaneously twisted. By successive nucleation at the concave corner, the crystalline layer develops laterally on the substrate, with its crystallographic orientation continuously rotated. In this way, a regular spatial pattern with well-defined long-range order is eventually achieved. Our model provides a criterion to predict when such an effect becomes observable in the nucleation-mediated lateral growth. The theoretical expectations are consistent with the experimental observations.Thin film growth has been extensively investigated in recent decades. Previous studies concentrated mostly on vertical growth (i.e., on the increase of film thickness above a substrate). 1,2 To initiate a thin film growth, nevertheless, horizontal extension of individual crystalline islands on the substrate is an important step. It is known that the crystallographic orientation of an epitaxial film is well aligned with that of the substrate. Yet in some cases the crystallographic orientation of the film may become complicated. [3][4][5] One interesting scenario is that nucleation selectively occurs at the concave corner of an expanding crystalline island and the substrate, and the island expansion (hence the thin film growth) is a repeated nucleation process at the concave corner with the orientation of each new nucleus heavily influenced by the surface tensions at the corner site. Once an embryo of nucleus (nascent nucleus) forms at the concave corner, the asymmetric local surface tensions will apply a torque to the embryo. 6 Hence, the crystallographic orientation is rotated with respect to the previous nucleus. Indeed, it has been observed that, during lateral growth of NH 4 Cl crystallite on a glass plate, the crystallographic orientation is continuously rotated, leading to either a periodic distribution of faceted regions and roughened regions 7 or a regular zigzag branches. 8,9 The appearance of the specific morphology depends on the index of the initial crystalline facet contacting the substrate and the axis of rotation. 9 Another example is the crystallographic wing tilt commonly observed in lateral overgrowth, 10,11 which is generally ascribed to the substrate effect. The underlying mechanisms of these lateral-growth-associated phenomena, however, are still not very clear, and the relationship between the rotation of the crystallographic orientation and the longrange order in aggregating crystallites has yet to be understood. In this paper, we try to establish fundamental relationships between nucleation and the rotation of crystallographic orientation. Based on previous experimental observations, we propose a model to...

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Hierarchical and Self‐Similar Growth of Self‐Assembled Crystals

Tian

Voigt

et al. 2003

Angewandte Chemie

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ZuschriftenMithilfe von mikroskopisch kleinen, polyedrischen selbstorganisierten Kristallen als Bausteinen bilden sich spontan gro˚e Kristalle und offene Mesophasen, in denen Form und Orientierung der zugrundeliegenden Struktureinheiten bewahrt bleiben. Diese Strukturen stehen in Einklang mit einfachen geometrischen Modellen. Mehr zu diesem Thema erfahren Sie im Beitrag von Liu et al. auf den folgenden Seiten.

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Fractal Aggregations at Low Driving Force with Strong Anisotropy

Cited by 52 publications

References 24 publications

Synthesis of single-crystal hyperbranched rhodium nanoplates with remarkable catalytic properties

Synthesis of single-crystal hyperbranched rhodium nanoplates with remarkable catalytic properties

Nucleation-Mediated Lateral Growth on Foreign Substrate

Hierarchical and Self‐Similar Growth of Self‐Assembled Crystals

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