Size- and Temperature-Dependent Structural Transitions in Gold Nanoparticles

Koga, Kenji; Ikeshoji, Tamio; Sugawara, Ko‐ichi

doi:10.1103/physrevlett.92.115507

Cited by 290 publications

(255 citation statements)

References 27 publications

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“…Our results imply that transitions to a stable crystalline phase do not occur easily because of the energy barriers. Our results agreed with those of previous studies, suggesting that several kinds of clusters can coexist in the same size range, such that structural transitions are not sharp [19,20]. If the clusters grow further, the third step of nucleation occurs to form stable clusters, although we did not observe this in our simulations.…”

Section: E Crystalline Structures Of Clusterssupporting

confidence: 67%

“…The structure of nanocrystal clusters is also important in scientific and technological applications [6][7][8][9]. It is known that the structure of an atomic cluster is a function of material component and temperature as well as the number of atoms in the cluster [9][10][11][12][13][14][15][16][17][18][19][20][21]. Many theoretical calculations and experiments have been conducted on size-dependent structures in atomic clusters for various materials, and they have shown that structures for nanoclusters have a variety of characteristics [9,11,15,[18][19][20]22].…”

Section: Introductionmentioning

confidence: 99%

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Analyzing multistep homogeneous nucleation in vapor-to-solid transitions using molecular dynamics simulations

et al. 2017

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In this paper, we present multistep homogeneous nucleations in vapor-to-solid transitions as revealed by molecular dynamics simulations on Lennard-Jones molecules, where liquidlike clusters are created and crystallized. During a long, direct NV E (constant volume, energy, and number of molecules) involving the integration of (1.9-15) × 10 6 molecules in up to 200 million steps (=4.3 μs), crystallization in many large, supercooled nanoclusters is observed once the liquid clusters grow to a certain size (∼800 molecules for the case of T 0.5ε/k). In the simulations, we discovered an interesting process associated with crystallization: the solid clusters lost 2-5 % of their mass during crystallization at low temperatures below their melting temperatures. Although the crystallized clusters were heated by latent heat, they were stabilized by cooling due to evaporation. The clusters crystallized quickly and completely except at surface layers. However, they did not have stable crystal structures, rather they had metastable structures such as icosahedral, decahedral, face-centered-cubic-rich (fcc-rich), and hexagonal-close-packed-rich (hcp-rich). Several kinds of cluster structures coexisted in the same size range of ∼1000-5000 molecules. Our results imply that multistep nucleation is a common first stage of condensation from vapor to solid.

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Section: E Crystalline Structures Of Clusterssupporting

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Analyzing multistep homogeneous nucleation in vapor-to-solid transitions using molecular dynamics simulations

et al. 2017

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“…For such calculations, we used the thermodynamic parameters of the bulk metals. Finitesize effects in elemental metal NPs can induce changes in the structural, vibrational and thermodynamic properties relative to bulk material including differences in bond length [20][21][22][23], Einstein temperature [23,24] and melting temperature [25]. However, these effects are typically significant only for NPs of diameter considerably less than those used in this report and, as a consequence, any error introduced through our use of bulk values was considered minimal.…”

mentioning

confidence: 90%

Role of Thermodynamics in the Shape Transformation of Embedded Metal Nanoparticles Induced by Swift Heavy-Ion Irradiation

et al. 2011

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Swift heavy-ion irradiation of elemental metal nanoparticles (NPs) embedded in amorphous SiO 2 induces a spherical to rodlike shape transformation with the direction of NP elongation aligned to that of the incident ion. Large, once-spherical NPs become progressively more rodlike while small NPs below a critical diameter do not elongate but dissolve in the matrix. We examine this shape transformation for ten metals under a common irradiation condition to achieve mechanistic insight into the transformation process. Subtle differences are apparent including the saturation of the elongated NP width at a minimum sustainable, metal-specific value. Elongated NPs of lesser width are unstable and subject to vaporization. Furthermore, we demonstrate the elongation process is governed by the formation of a molten ion-track in amorphous SiO 2 such that upon saturation the elongated NP width never exceeds the molten ion-track diameter. Ion-solid interactions during swift heavy-ion irradiation (SHII) are dominated by inelastic processes in the form of electron excitation and ionization while, in contrast, the influence of elastic processes such as ballistic displacements is negligible. Macroscopically, amorphous SiO 2 (a-SiO 2 ) undergoes a volume-conserving anisotropic deformation when subjected to SHII such that thin freestanding layers contract and expand, respectively, in directions parallel and perpendicular to that of the incident ion [1]. The viscoelastic model [2,3], based on a transient thermal effect, successfully explains this so-called ion hammering. Microscopically, energy is deposited along the ion path, from incident ion to matrix electrons, and is then dissipated within a narrow cylinder of material surrounding the ion path. The heat flow in both the electron and lattice subsystems is well described as functions of time and radial distance by the inelastic thermal spike (i-TS) model [4,5]. When the temperature of the lattice exceeds that required for melting, the material along the ion path is molten and upon quenching an ion track is formed. Recently, we measured the molten ion-track diameter in a-SiO 2 as a function of electronic stopping power [6]. The ion-track radial density distribution consisted of an under-dense core and over-dense shell (relative to unirradiated material), the formation of which was attributed to a quenched-in pressure wave emanating from the ion-track center [6].Elemental metal nanoparticles (NPs) embedded in a-SiO 2 and subjected to SHII can undergo an intriguing shape transformation where once-spherical NPs become progressively more rodlike with the direction of elongation aligned along that of the incident ion. This phenomenon has been reported for several metals under a wide range of SHII conditions, with Refs. [7][8][9][10][11][12][13][14][15][16][17] citing selected examples. Freestanding metallic NPs irradiated under comparable conditions do not change shape, demonstrating the embedding a-SiO 2 matrix must have a role in the shape transformation process [8,17]. An unambiguous ...

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“…Gold nanoparticles over a wide size range, 3-14 nm, undergo a structural transformation from icosahedral to decahedral morphology just below the melting points. [7] The various preparations of the monometallic systems Au/SiO 2 , Au/MgO and Au/Al 2 O 3 , have demonstrated that it is difficult to obtain small monodisperse gold particles. [8 -10] The particles obtained have an average diameter between 3 and 200 nm depending on the method of preparation.…”

Section: Introductionmentioning

confidence: 99%

In situ ESR study of gold supported on NaY zeolite

Roduner

2009

Asia-Pacific J Chem Eng

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Electron spin resonance (ESR) spectroscopy was used to study the anchoring of a Au complex and gold nanoparticles in NaY type zeolites. The complex of Au(II) with two nitrogen atoms of two ethylenediamine ligands [g iso = 2.053, A (Au) = 16.4 G, A (N) = 15.0 G.] in the supercage of the zeolite and conduction electron spin resonance (CESR) of gold particles with 1.56-nm diameter (g = 2.064) were observed. Their formation and stability were related with the gold concentration and the pre-treatment conditions. The small gold particles stabilized in the supercage of zeolite were formed in the samples with low gold concentration after oxygen pre-treatment. The confinement in the zeolite pores obviously prevents the Au(II) complex bound to two nitrogen ligands from undergoing disproportionation.

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Size- and Temperature-Dependent Structural Transitions in Gold Nanoparticles

Cited by 290 publications

References 27 publications

Analyzing multistep homogeneous nucleation in vapor-to-solid transitions using molecular dynamics simulations

Analyzing multistep homogeneous nucleation in vapor-to-solid transitions using molecular dynamics simulations

Role of Thermodynamics in the Shape Transformation of Embedded Metal Nanoparticles Induced by Swift Heavy-Ion Irradiation

In situ ESR study of gold supported on NaY zeolite

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