Synthesis and size-dependent crystallization of colloidal germanium telluridenanoparticles

Caldwell, Marissa A.; Raoux, Simone; Wang, Robert Y.; Wong, H.-S. Philip; Milliron, Delia J.

doi:10.1039/b917024c

Cited by 121 publications

(119 citation statements)

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“…In particular the formation of Te crystallites in the presence of hexadecanethiol is somewhat surprising, since Milliron et al reported on the synthesis of GeTe nanoparticles with controlled size and morphology only in the presence of dodecanethiol, 23 while Korgel et al reported that hexadecanethiol quenches the formation of elemental Te nanowires. 30 These findings also demonstrate that the initial formation of Te polyanions by amination of Te(SiEt 3 ) 2 , which proceeds only with primary and secondary amines, seems to play a key role in the reaction mechanism of the GeTe particle formation.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Reactions of GeI 2 with TOPTe in the presence of tri-n-octylphosphine (TOP), tri-n-octylphosphine oxid (TOPO), and dodecanethiol at 250°C yielded amorphous GeTe nanoparticles, whose sizes ranged from 1.7 to 5 nm. 23 A strong correlation between the crystal size and the crystallization temperature was observed, with a decreasing particle size leading to an increase in crystallization temperature. While for bulk GeTe an amorphous-to-crystalline phase transition was observed at about 170°C, 27 1.8 nm sized GeTe nanoparticles started to crystallize not before 240°C.…”

Section: ■ Introductionmentioning

confidence: 94%

“…16 Nanosized PCM materials such as GeTe nanoparticles are very interesting because of the well-known influence of the reduced dimensionality of a given material on its physical properties such as melting points or crystallization properties. 17−22 Since GeTe nanoparticles are expected to improve device performances, 23 the interest in suitable precursors for the size-and shape-selective synthesis of GeTe nanocrystals has remarkably increased in recent years, and several general reaction pathways have been established. 24 GeTe nanowires containing a large excess of elemental tellurium were formed in high-boiling organic solvents via seed-mediated growth using Bi nanoparticles, 25 whereas GeTe nanowires with uniform diameter distributions were grown on the basis of the VLS mechanism.…”

Section: ■ Introductionmentioning

confidence: 99%

“…While for bulk GeTe an amorphous-to-crystalline phase transition was observed at about 170°C, 27 1.8 nm sized GeTe nanoparticles started to crystallize not before 240°C. 23 Crystalline GeTe nanoparticles were also obtained from the reaction of Ge[N(SiMe 3 ) 2 ] 2 and TOPTe in 1-octadecene at 200°C in the presence of oleylamine and dodecanethiol, whereas amorphous GeTe particles were formed in the absence of dodecanethiol at reaction temperatures below 170°C. 27 Increasing reaction times produced larger, polydisperse nanoparticles (9.0−27.8 nm).…”

Section: ■ Introductionmentioning

confidence: 99%

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Solution-Based Synthesis of GeTe Octahedra at Low Temperature

et al. 2013

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GeTe octahedra were prepared by reaction of equimolar amounts of GeCl 2 ·dioxane and Te(SiEt 3 ) 2 in oleylamine, whereas a slight excess of the Te precursor yielded GeTe octahedra decorated with elemental Te nanowires, which can be removed by washing with TOP. The mechanism of the GeTe formation is strongly influenced by the solvent. The expected elimination of Et 3 SiCl (dehalosilylation) only occurred in aprotic solvents, whereas Te(SiEt 3 ) 2 was found to react with primary and secondary amines with formation of silylamines. Temperature-dependent studies on the reaction in oleylamine showed that crystalline GeTe particles are formed at temperatures higher than 140 °C. XRD, SAED, and HRTEM studies proved the formation of rhombohedral GeTe nanoparticles. These findings were confirmed by a single-crystal and powder X-ray analysis. The rhombohedral structure modification was found, and the structure was solved in the acentric space group R3m. Disciplines Ceramic Materials | Complex Fluids | Other Materials Science and Engineering | Thermodynamics CommentsReprinted with permission from Inorg. Chem., 2013, 52 (24) ABSTRACT: GeTe octahedra were prepared by reaction of equimolar amounts of GeCl 2 · dioxane and Te(SiEt 3 ) 2 in oleylamine, whereas a slight excess of the Te precursor yielded GeTe octahedra decorated with elemental Te nanowires, which can be removed by washing with TOP. The mechanism of the GeTe formation is strongly influenced by the solvent. The expected elimination of Et 3 SiCl (dehalosilylation) only occurred in aprotic solvents, whereas Te(SiEt 3 ) 2 was found to react with primary and secondary amines with formation of silylamines. Temperature-dependent studies on the reaction in oleylamine showed that crystalline GeTe particles are formed at temperatures higher than 140°C. XRD, SAED, and HRTEM studies proved the formation of rhombohedral GeTe nanoparticles. These findings were confirmed by a single-crystal and powder X-ray analysis. The rhombohedral structure modification was found, and the structure was solved in the acentric space group R3m.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 94%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Solution-Based Synthesis of GeTe Octahedra at Low Temperature

et al. 2013

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“…6 For phase-change materials used in optical data storage and nonvolatile computer memory, chalcogenide (e.g., GeTe) NPs offer an intriguing route of manufacturing composite materials with tuned (size-dependent) melting point and recrystallization temperature. 7 Other size-dependent properties include surface plasmon resonance in metal NPs, 8 quantum confinement effects in semiconductor NPs (quantum dots), 9 and superparamagnetism in magnetic materials. 10 The changes in physical properties are not always desirable, and, e.g., the magnetization direction of small ferromagnetic NPs can switch at low temperature, making them unsuitable for applications.…”

Section: ■ Introductionmentioning

confidence: 99%

Atomistic Simulations of Functional Au₁₄₄(SR)₆₀ Gold Nanoparticles in Aqueous Environment

et al. 2012

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Charged monolayer-protected gold nanoparticles (AuNPs) have been studied in aqueous solution by performing atomistic molecular dynamics simulations at physiological temperature (310 K). Particular attention has been paid to electrostatic properties that modulate the formation of a complex comprised of the nanoparticle together with surrounding ions and water. We focus on Au 144 nanoparticles that comprise a nearly spherical Au core (diameter ∼2 nm), a passivating Au−S interface, and functionalized alkanethiol chains. Cationic and anionic AuNPs have been modeled with amine and carboxyl terminal groups and Cl − /Na + counterions, respectively. The radial distribution functions show that the side chains and terminal groups show significant flexibility. The orientation of water is distinct in the first solvation shell, and AuNPs cause a long-range effect in the solvent structure. The radial electrostatic potential displays a minimum for AuNP − at 1.9 nm from the center of the nanoparticle, marking a preferable location for Na + , while the AuNP + potential (affecting the distribution of Cl − ) rises almost monotonically with a local maximum. Comparison to Debye−Huckel theory shows very good agreement for radial ion distribution, as expected, with a Debye screening length of about 0.2−0.3 nm. Considerations of zeta potential predict that both anionic and cationic AuNPs avoid coagulation. The results highlight the importance of long-range electrostatic interactions in determining nanoparticle properties in aqueous solutions. They suggest that electrostatics is one of the central factors in complexation of AuNPs with other nanomaterials and biological systems, and that effects of electrostatics as water-mediated interactions are relatively long-ranged, which likely plays a role in, e.g., the interplay between nanoparticles and lipid membranes that surround cells. ■ INTRODUCTIONNanoparticles (NPs, size range 1−100 nm) have many interesting properties, as they bridge the gap between bulk materials and atomic or molecular structures.1,2 Typically, the physical properties of bulk materials do not depend on the size of the sample, while at the nanoscale size-dependent properties are frequently encountered. Two contributing factors for the size dependence are (a) number of surface atoms whose percentage reduces as the NP size increases toward the bulk limit and (b) quantum confinement effects at the smallest length scales (<10 nm) where the electronic structure plays a significant role in determining the composition, stability, structure, and function of NPs. 3,4 Nanoparticles often display fascinating optical properties because of quantum effects, and, e.g., gold nanoparticles (AuNPs) appear from yellow to deep red and black in solution depending on their size. 5 In photovoltaic cells, absorption of solar radiation is much higher for semiconductor materials comprised of NPs than for continuous sheets of thin films (e.g., CdTe, ZnO).6 For phase-change materials used in optical data storage and nonvolatile computer ...

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Phase Change Memory

Jeyasingh

Ahn

Eryilmaz

et al. 2014

Emerging Nanoelectronic Devices

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Synthesis and size-dependent crystallization of colloidal germanium telluridenanoparticles

Cited by 121 publications

References 49 publications

Solution-Based Synthesis of GeTe Octahedra at Low Temperature

Solution-Based Synthesis of GeTe Octahedra at Low Temperature

Atomistic Simulations of Functional Au₁₄₄(SR)₆₀ Gold Nanoparticles in Aqueous Environment

Phase Change Memory

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Synthesis and size-dependent crystallization of colloidal germanium telluridenanoparticles

Cited by 121 publications

References 49 publications

Solution-Based Synthesis of GeTe Octahedra at Low Temperature

Solution-Based Synthesis of GeTe Octahedra at Low Temperature

Atomistic Simulations of Functional Au144(SR)60 Gold Nanoparticles in Aqueous Environment

Phase Change Memory

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Atomistic Simulations of Functional Au₁₄₄(SR)₆₀ Gold Nanoparticles in Aqueous Environment