Reconstructing a solid-solid phase transformation pathway in CdSe nanosheets with associated soft ligands

Wang, Zhongwu; Wen, Xiaodong; Hoffmann, Roald; Son, Jae Sung; Li, Ruipeng; Fang, Chia-Chen; Smilgies, Detlef‐M.; Hyeon, Taeghwan

doi:10.1073/pnas.1011224107

Cited by 126 publications

(129 citation statements)

References 43 publications

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“…In addition, nanograins suppress martensitic phase transformation as well. In general, nanocrystalline material can possess different transformation paths, metastable phases, and transformation pressures under hydrostatic conditions (26,27). Nano-sized grains can either suppress (26)(27)(28) or promote (26,27,29) phase transformations.…”

Section: Resultsmentioning

confidence: 99%

“…In general, nanocrystalline material can possess different transformation paths, metastable phases, and transformation pressures under hydrostatic conditions (26,27). Nano-sized grains can either suppress (26)(27)(28) or promote (26,27,29) phase transformations. At the same time, some features of X-ray patterns are similar to those in other turbostratic structures, such as BCN solid solution (15) and BC 4 (14).…”

Section: Resultsmentioning

confidence: 99%

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Shear-induced phase transition of nanocrystalline hexagonal boron nitride to wurtzitic structure at room temperature and lower pressure

Levitas

Zhu

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

134

135

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Disordered structures of boron nitride (BN), graphite, boron carbide (BC), and boron carbon nitride (BCN) systems are considered important precursor materials for synthesis of superhard phases in these systems. However, phase transformation of such materials can be achieved only at extreme pressure-temperature conditions, which is irrelevant to industrial applications. Here, the phase transition from disordered nanocrystalline hexagonal (h)BN to superhard wurtzitic (w)BN was found at room temperature under a pressure of 6.7 GPa after applying large plastic shear in a rotational diamond anvil cell (RDAC) monitored by in situ synchrotron X-ray diffraction (XRD) measurements. However, under hydrostatic compression to 52.8 GPa, the same hBN sample did not transform to wBN but probably underwent a reversible transformation to a high-pressure disordered phase with closed-packed buckled layers. The current phase-transition pressure is the lowest among all reported direct-phase transitions from hBN to wBN at room temperature. Usually, large plastic straining leads to disordering and amorphization; here, in contrast, highly disordered hBN transformed to crystalline wBN. The mechanisms of strain-induced phase transformation and the reasons for such a low transformation pressure are discussed. Our results demonstrate a potential of low pressure-room temperature synthesis of superhard materials under plastic shear from disordered or amorphous precursors. They also open a pathway of phase transformation of nanocrystalline materials and materials with disordered and amorphous structures under extensive shear.plastic deformation | transition mechanism S ynthesis of superhard materials in the boron carbon nitride (BCN) system under high pressure and temperature is one of the modern directions in high-pressure material science with significant technological potential. In particular, superhard wurtzitic boron nitride (wBN) and, especially, cubic boron nitride (cBN) are of great interest because of their unique properties: high hardness, high thermal conductivity, chemical inertia to ferrous materials, high dynamic strength, and high wear resistance, etc. (1). They can be obtained, in particular, by the direct solid-solid phase transitions initiated from the graphite-like boron nitride (BN) phases [i.e., hexagonal (h)BN and rhombohedral (r)BN] under extreme conditions. Specifically, hBN-to-wBN phase transition has been extensively studied in both dynamic and static high-pressure experiments. An important parameter that determines transformation pressure and mechanism is the concentration of the turbostratic stacking faults or degree of disordering. It was found that a highly ordered hBN transforms to wBN when compressed to high pressures [8.1-13 GPa (2-5)] at either room or high temperatures. The lowest pressure at which highly ordered hBN-to-wBN transformation starts at room temperature is, thus far, 8.1 GPa; it starts to become irreversible above 10 GPa; transformation does not complete up to 25 GPa (4, 6). In ref. 3, highly ord...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Shear-induced phase transition of nanocrystalline hexagonal boron nitride to wurtzitic structure at room temperature and lower pressure

Levitas

Zhu

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

134

135

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“…[34] As a result, steric hindrance-vdW balances were destroyed and dominant vdW attraction forces led to the formation of bundles. [38] This argument was supported by the transmission electron microscopy (TEM) characterization (Figure 2d), which gave a wire-towire distance of ≈0.9 nm, more than two times smaller than that for fresh AuNWs. When the aging time further increased to 12 h, the nanowire-nanowire distance further decreased to ≈0.7 nm (Figure 2f).…”

Section: Mechanism Of Mesh Film Formationmentioning

confidence: 85%

“…The average distance (measured by 100 randomly distributed nanowire-nanowire distance, the same below) between adjacent wires was measured to be ≈2.5 nm, slightly shorter than double ligand chain length (≈4 nm) due to ligand interdigitation. [37,38] For the samples aged for 6 h under ambient conditions, the ligands may come off nanowire surfaces possibly due to oxidation breaking the weak bonds between amino groups and gold surfaces. [34] As a result, steric hindrance-vdW balances were destroyed and dominant vdW attraction forces led to the formation of bundles.…”

Section: Mechanism Of Mesh Film Formationmentioning

confidence: 99%

Fabrication of Highly Transparent and Flexible NanoMesh Electrode via Self‐assembly of Ultrathin Gold Nanowires

Gong

Zhao

Yap

et al. 2016

Adv Elect Materials

118

120

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new design principles. Nanomaterials, such as carbon nanotubes, [1,3,4,[12][13][14] graphene, [15,16] and metal nanowires [8,9,[17][18][19][20][21][22][23][24] have been recently explored and demonstrated their potentials to flexible TE overcoming shortcoming of current ITObased TE (brittleness, low inferred transmittance, and earth rareness). Despite this potential, it remains challenging to achieve high conductivity and high transparency without deterioration under repeated bending and stretching cycles. In this context, metal mesh/grid is emerging as a promising solution, which achieved exceptionally low-sheet resistance and high optical transparency. [25][26][27] The fabrication of mesh-like electrodes could be achieved by top-down [25][26][27][28] and bottomup [29,30] approaches. Self-assembled meshlike structure have been successfully demonstrated by using silver and gold nanoparticles. [29,30] However, to the best of our knowledge, self-assembled mesh geometry based on 1D nanowire materials has not been reported. Here, we report a simple yet efficient solution-based, equipment-free interfacial self-assembly strategy to fabricate mesh TE (mTE) using ultrathin gold nanowires. Unlike other metal nanomaterials, ultrathin gold nanowires we used possess a serpentine morphology due to its ultrathin width (≈2 nm) and ultrahigh aspect ratio (>10 000). [31][32][33] Briefly, freshly synthesized AuNWs hexane solutions were purified and aged prior to spreading onto air-water interface. During the hexane evaporation, AuNWs could self-assemble into bundles with a mesh-like network. The partial removal of oleyamine ligands during aging may be the reason for the bundle formation. [34] The bundles had a typical thickness of 193.7 ± 67.6 nm and mesh pore sizes varied from 8 μm to 52 μm, depending on 100 random pores at aging time of 12 h. The resulting mesh film is easily transferred to a variety of substrate, exhibiting a sheet resistance of ≈40 times smaller than our previous nonmeshed film [18] under the similar optical transmittance of ≈92%. Moreover, our mesh electrode is patternable and washable with excellent flexibility, which could be directly used for touch screen and flexible circuit of light emitting devices (LEDs). We believe our approach opens a new route to flexible TE for applications in future soft electronic sensors, displays and energy-harvesting devices.Transparent electrodes simultaneously require high electrical conductivity and high optical transparency, which have been achieved with mesh metal structures. However, most currently fabricated micro-and nanoelectronic devices are produced via top-down lithography methods. Here, a bottomup self-assembly approach to fabricate mesh electrode using ultrathin gold nanowires (AuNWs) at the air/water interface is reported. Slow partial ligand removal during the aging process is the key for the formation of such self-assembled mesh structures. The resulting mesh film has a typical mesh pore size of 8-52 μm, with a sheet resistance of ≈40 times smaller than our pr...

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“…However the interparticle separation that this type of stabilisation offers on the substrate is of the same order of magnitude of the capping ligand $2 nm. 44 This interparticle separation can be increased by varying the spin coating parameters, but this oen results in areas of dense nanoparticle coverage interspaced by vast areas of scarce nanoparticle coverage. Ag nanoparticles that are not well separated can "etch as one" under MAE conditions and subsequently coalesce to seed the growth of larger diameter Ge nanowires.…”

Section: Resultsmentioning

confidence: 99%

Containing the catalyst: diameter controlled Ge nanowire growth

et al. 2013

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Sub-20 nm diameter Ge nanowires with narrow size distributions were grown from Ag nanoparticle seeds in a supercritical fluid (SCF) growth process. The mean Ge nanowire diameter and size distribution was shown to be dependent upon Ag nanoparticle coalescence, using both spin-coating and a block copolymer (BCP) templating method for particle deposition. The introduction of a metal assisted etching (MAE) processing step in order to "sink" the Ag seeds into the growth substrate, prior to nanowire growth, was shown to dramatically decrease the mean nanowire diameter from 27.7 to 14.4 nm and to narrow the diameter distributions from 22.2 to 6.8 nm. Hence, our BCP-MAE approach is a viable route for controlling the diameters of semiconductor nanowires whilst also ensuring a narrow size distribution. The MAE step in the process was found to have no detrimental effect on the length or crystalline quality of the Ge nanowires synthesised.

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Reconstructing a solid-solid phase transformation pathway in CdSe nanosheets with associated soft ligands

Cited by 126 publications

References 43 publications

Shear-induced phase transition of nanocrystalline hexagonal boron nitride to wurtzitic structure at room temperature and lower pressure

Shear-induced phase transition of nanocrystalline hexagonal boron nitride to wurtzitic structure at room temperature and lower pressure

Fabrication of Highly Transparent and Flexible NanoMesh Electrode via Self‐assembly of Ultrathin Gold Nanowires

Containing the catalyst: diameter controlled Ge nanowire growth

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