Unraveling the Spatial Distribution of Catalytic Non-Cubic Au Phases in a Bipyramidal Microcrystallite by X-ray Diffraction Microscopy

Sow, Chaitali; Sarma, Abhisakh; Schropp, Andreas; Dzhigaev, Dmitry; Keller, Thomas F.; Schroer, Christian G.; Sanyal, M. K.

doi:10.1021/acsnano.0c02031

Cited by 11 publications

(18 citation statements)

References 36 publications

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“…Recent scanning X-ray diffraction microscopy (SXDM) study on a single bc(o,t) Au bipyramid revealed the spatial distribution of the various lattices at the crystallite body, i.e., fcc enriched tips and bc(o,t) enriched body. 32 Additionally, the presence of ranges of bc(o,t) lattices hosting simultaneously large compressive (−6.06%) and tensile (+4.21%) strains was found. In spite of the co-presence of large compressive and tensile strains in the μm sized crystallite, the ambient stability of the crystallite for indefinite period of time is commendable!…”

Section: ■ Results and Discussionmentioning

confidence: 92%

“…Therefore, the intensity of bc(o,t) reflection is usually lower than those of fcc reflections. The presence of strain 32 in addition to lower structure factor and smaller number of atoms in bc(o,t) (2/unit cell) than in fcc (4/unit cell) may contribute to the weakening of bc(o,t) peak intensities. The bc(o,t) crystallites annealed at 700 °C also exhibit similar deformed morphology 33 as in here but with different final orientation in the XRD pattern, i.e., (111) f .…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…31 The unique bipyramidal morphology of the crystallite hosting 5-fold twining and considerable twist along the length enables stabilization of unconventional body-centered orthorhombic and body-centered tetragonal phases (together called as bc(o,t)). 32 In spite of the nanoscale strain, these lattices are ambient stable for years and also thermally stable at ∼400 °C. Interestingly, these phases convert back to fcc irreversibly while annealing at much higher temperatures (∼700 °C) and exhibit a reversible phase transformation under high pressure (∼40 GPa).…”

Section: ■ Introductionmentioning

confidence: 99%

“…The Au microcrystallites synthesized in the laboratory are known to host highly strained noncubic lattices . The unique bipyramidal morphology of the crystallite hosting 5-fold twining and considerable twist along the length enables stabilization of unconventional body-centered orthorhombic and body-centered tetragonal phases (together called as bc(o,t)) . In spite of the nanoscale strain, these lattices are ambient stable for years and also thermally stable at ∼400 °C.…”

Section: Introductionmentioning

confidence: 99%

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Noncubic to Cubic Structural Transformation in Au Microcrystallites by Oxidative Etching

Sow

2021

J. Phys. Chem. C

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Modulating crystal structures of noble metals can provide a library of new properties, optical, electrical, catalytic, and so on. Surprisingly, most lattice conversions occur at high temperatures and pressures. Recently, Au microcrystallites have been stabilized in body-centered orthorhombic and body-centered tetragonal lattices, together termed as bc(o,t), via chemical routes that exhibit exuberant catalytic performance. The noncubic lattices are found to be robust at pressures up to ∼40 GPa and temperature of 700 °C. Herein, we report the irreversible phase transformation to thermodynamically stable face-centered cubic (fcc) lattice induced by surfactants (such as tetrabutylammonium bromide) at high but near ambient temperatures mediated by (002)bc(o,t) → (002)fcc orientational changes involving an intermediate phase termed bct-I. The phase transformation is essentially due to oxidative etching at the nanoscale followed by redeposition of the metal. Interestingly, the conversion is governed by the binding strength of the adsorbent and thereby dependent on the alkyl chain length of the participating quaternary ammonium cation, the most effective one being the butyl chain. The study also unravels a core–shell structure of the microcrystallite, i.e., fcc capped bc(o,t).

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Section: ■ Results and Discussionmentioning

confidence: 92%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Noncubic to Cubic Structural Transformation in Au Microcrystallites by Oxidative Etching

Sow

2021

J. Phys. Chem. C

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“…29 Further, the microcrystallites showed high catalytic activity (unlike fcc Au) and stability in Hg and aqua regia. 30 distribution of these lattices revealed the bc(o,t)-rich body and fcc-enriched tips 31 while hosting a bc(o,t)-fcc core−shell structure. 32 In this work, we have investigated the optical properties of bc(o,t) microcrystallites by monitoring the extinction spectra.…”

Section: ■ Introductionmentioning

confidence: 99%

Optical Properties of Noncubic Au Microcrystallites

2021

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Size-and shape-controlled synthesis of Au nanomaterials and their optical properties have been well explored in the past. However, the influence of crystallinity, particularly in the case of Au, which exists in the face-centered cubic (fcc) phase and is extraordinarily stable, is much unexplored. Recently, Au microcrystallites with unusually stable phases of body-centered tetragonal and body-centered orthorhombic lattices have been synthesized in the laboratory. These metastable crystallites possess unusual properties compared to their fcc counterparts. In this work, we have investigated the optical extinction properties of the microcrystallites while varying the noncubic mole fractions by carefully tuning the synthetic conditions. The crystallites show near-infrared plasmonic features associated with multipolar resonances. The experimental observations have been compared with calculations performed using the discrete dipolar approximation (DDA) method. While there is a reasonable agreement between the two, the noncubic nature of the lattice seems to have little influence on the optical properties investigated.

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Crystal Structure Dependent Dissolution of Non‐Cubic Au Crystallites in Aqua Regia

Sow

2021

Chemistry A European J

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Properties of metal crystallites are governed by their morphologies and inherent crystal structures. In this work, bipyramidal Au microcrystallites hosting non-cubic lattices, body-centered orthorhombic and tetragonal (together termed as bc(o,t)), are investigated for their stability in aqua regia. Specifically, microcrystallites comprising 92 % of bc(o,t) have been subjected to aqua regia of different concentrations and the changes in morphology and lattice phases have been monitored using scanning electron microscopy and X-ray diffraction techniques. The dissolution process was found to be crystal structure dependent and begin at the bipyramidal tips enriched with fcc lattice while retaining the bc(o,t) rich body. Interestingly, with increasing the reaction times, the remaining core was found to be highly reluctant to dissolution and instead, transformed to tetragonal lattices which with increasing treatment, exhibited lattice parameters closer to that of fcc. The study reveals the presence of a bc(o,t)-fcc core-shell structure with the tips enriched with fcc.

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Unraveling the Spatial Distribution of Catalytic Non-Cubic Au Phases in a Bipyramidal Microcrystallite by X-ray Diffraction Microscopy

Cited by 11 publications

References 36 publications

Noncubic to Cubic Structural Transformation in Au Microcrystallites by Oxidative Etching

Noncubic to Cubic Structural Transformation in Au Microcrystallites by Oxidative Etching

Optical Properties of Noncubic Au Microcrystallites

Crystal Structure Dependent Dissolution of Non‐Cubic Au Crystallites in Aqua Regia

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