One Step Synthesis of Pure Cubic and Monoclinic HfO<sub>2</sub> Nanoparticles: Effects of Temperature and Ambient on the Photoluminescent Properties

Rauwel, Protima; Galeckas, Augustinas; Rauwel, Erwan

doi:10.1149/06444.0019ecst

Cited by 3 publications

(7 citation statements)

References 17 publications

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“…Similar particles (4 nm) are obtained when the mixture is heated at 220 °C for four days . When the same precursor is heated in benzylamine, 2.6 nm cubic hafnia is obtained . Given the absence of an ether elimination mechanism in benzylamine, we speculate that the oxide is formed by an E1 mechanism.…”

Section: Colloidal Metal Oxide Nanocrystalssupporting

confidence: 60%

“…204 When the same precursor is heated in benzylamine, 2.6 nm cubic hafnia is obtained. 224 Given the absence of an ether elimination mechanism in benzylamine, we speculate that the oxide is formed by an E1 mechanism. The oxygen-deficient reaction mixture is most likely responsible for oxygen vacancies and thus the stabilization of the cubic phase.…”

Section: − +mentioning

confidence: 88%

“…When hafnium tert-butoxide is heated in benzyl alcohol at 300 °C, 3 nm monoclinic hafnia is obtained after 48 h. 224 Similar particles (4 nm) are obtained when the mixture is heated at 220 °C for four days. 204 When the same precursor is heated in benzylamine, 2.6 nm cubic hafnia is obtained.…”

Section: − +mentioning

confidence: 93%

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Nonaqueous Chemistry of Group 4 Oxo Clusters and Colloidal Metal Oxide Nanocrystals

2022

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We review the nonaqueous precursor chemistry of the group 4 metals to gain insight into the formation of their oxo clusters and colloidal oxide nanocrystals. We first describe the properties and structures of titanium, zirconium, and hafnium oxides. Second, we introduce the different precursors that are used in the synthesis of oxo clusters and oxide nanocrystals. We review the structures of group 4 metal halides and alkoxides and their reactivity toward alcohols, carboxylic acids, etc. Third, we discuss fully condensed and atomically precise metal oxo clusters that could serve as nanocrystal models. By comparing the reaction conditions and reagents, we provide insight into the relationship between the cluster structure and the nature of the carboxylate capping ligands. We also briefly discuss the use of oxo clusters. Finally, we review the nonaqueous synthesis of group 4 oxide nanocrystals, including both surfactant-free and surfactant-assisted syntheses. We focus on their precursor chemistry and surface chemistry. By putting these results together, we connect the dots and obtain more insight into the fascinating chemistry of the group 4 metals. At the same time, we also identify gaps in our knowledge and thus areas for future research.

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Section: Colloidal Metal Oxide Nanocrystalssupporting

confidence: 60%

Section: − +mentioning

confidence: 88%

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Nonaqueous Chemistry of Group 4 Oxo Clusters and Colloidal Metal Oxide Nanocrystals

2022

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“…The sol–gel route has evolved into an established method to synthesize oxide nanocrystals with a broad range of sizes, shapes, and compositions. ,− The success of nonaqueous sol–gel routes compared to their aqueous counterpart is often accredited to their slower reaction rate as a consequence of the moderate reactivity of the C–O bond, allowing crystals (the thermodynamic product) to be formed immediately instead of an amorphous gel (the kinetic product). Amorphous products typically require high-temperature calcination to crystallize.…”

Section: Discussionmentioning

confidence: 99%

From Gel to Crystal: Mechanism of HfO₂ and ZrO₂ Nanocrystal Synthesis in Benzyl Alcohol

Goossens,

Aalling-Frederiksen,

Tack

et al. 2024

J. Am. Chem. Soc.

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Nonaqueous sol−gel syntheses have been used to make many types of metal oxide nanocrystals. According to the current paradigm, nonaqueous syntheses have slow kinetics, thus favoring the thermodynamic (crystalline) product. Here we investigate the synthesis of hafnium (and zirconium) oxide nanocrystals from the metal chloride in benzyl alcohol. We follow the transition from precursor to nanocrystal through a combination of rheology, EXAFS, NMR, TEM, and X-ray total scattering (PDF analysis). Upon dissolving the metal chloride precursor, the exchange of chloride ligands for benzylalkoxide liberates HCl. The latter catalyzes the etherification of benzyl alcohol, eliminating water. During the temperature ramp to the reaction temperature (220 °C), sufficient water is produced to turn the reaction mixture into a macroscopic gel. Rheological analysis shows a network consisting of strong interactions with temperature-dependent restructuring. After a few minutes at the reaction temperature, crystalline particles emerge from the gel, and nucleation and growth are complete after 30 min. In contrast, 4 h are required to obtain the highest isolated yield, which we attribute to the slow in situ formation of water (the extraction solvent). We used our mechanistic insights to optimize the synthesis, achieving high isolated yields with a reduced reaction time. Our results oppose the idea that nonaqueous sol−gel syntheses necessarily form crystalline products in one step, without a transient, amorphous gel state.

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“…[16,17] By now, several methods have been applied to chemically synthesize monoclinic or cubic HfO 2 nanocrystals with different sizes. [18][19][20][21][22][23][24][25][26][27][28][29][30] Typical high-boiling solvents in non-aqueous syntheses are benzyl alcohol, benzylamine, and oleylamine. Apart from these approaches, presumably one of them stands out as it features a non-hydrolytic gram scale synthesis of sub-4 nm nanocrystalline hafnia, where tri-n-octylphoshphine oxide (TOPO) serves as both, a high boiling solvent for the metal precursors and as coordinating agent that prevents crystal aggregation.…”

mentioning

confidence: 99%

Tailoring of Colloidal HfO₂ Nanocrystals with Unique Morphologies and New Self‐Assembly Features

Ohlerth,

Du,

Hammoor

et al. 2024

Small Science

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Advancing the synthesis of HfO2 nanocrystals, a refined anhydrous protocol that enables kinetic trapping of the metastable tetragonal phase and modulates twinning defects in anisotropically grown monoclinic nanoprisms is presented. This evolved sol–gel approach examines the role of the capping agent tri‐n‐octylphosphine oxide (TOPO) and introduces a novel heating strategy with sequential growth stages. Replacement of TOPO with triphenylphosphine oxide (TPPO) leads to the formation of prismatic hafnia nanocrystals exhibiting pristine {011}‐facets of the monoclinic phase. Furthermore, a hot‐injection inspired heating approach yields sub‐4 nm isotropic HfO2 nanocrystals in the tetragonal phase, bypassing the need for aliovalent cation species. In contrast, a heat‐up approach culminates in the generation of well‐characterized HfO2 nanorods. With sophisticated transmission electron microscopy analysis and the Wulff construction method, insights into the structural nucleation of nanoparticle growth are provided. This synthesis offers exceptional control and facilitates the formation of self‐assemblies akin to liquid crystals, opening the door for new applications with nanocolloidal HfO2.

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One Step Synthesis of Pure Cubic and Monoclinic HfO₂ Nanoparticles: Effects of Temperature and Ambient on the Photoluminescent Properties

Cited by 3 publications

References 17 publications

Nonaqueous Chemistry of Group 4 Oxo Clusters and Colloidal Metal Oxide Nanocrystals

Nonaqueous Chemistry of Group 4 Oxo Clusters and Colloidal Metal Oxide Nanocrystals

From Gel to Crystal: Mechanism of HfO₂ and ZrO₂ Nanocrystal Synthesis in Benzyl Alcohol

Tailoring of Colloidal HfO₂ Nanocrystals with Unique Morphologies and New Self‐Assembly Features

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One Step Synthesis of Pure Cubic and Monoclinic HfO2 Nanoparticles: Effects of Temperature and Ambient on the Photoluminescent Properties

Cited by 3 publications

References 17 publications

Nonaqueous Chemistry of Group 4 Oxo Clusters and Colloidal Metal Oxide Nanocrystals

Nonaqueous Chemistry of Group 4 Oxo Clusters and Colloidal Metal Oxide Nanocrystals

From Gel to Crystal: Mechanism of HfO2 and ZrO2 Nanocrystal Synthesis in Benzyl Alcohol

Tailoring of Colloidal HfO2 Nanocrystals with Unique Morphologies and New Self‐Assembly Features

Contact Info

Product

Resources

About

One Step Synthesis of Pure Cubic and Monoclinic HfO₂ Nanoparticles: Effects of Temperature and Ambient on the Photoluminescent Properties

From Gel to Crystal: Mechanism of HfO₂ and ZrO₂ Nanocrystal Synthesis in Benzyl Alcohol

Tailoring of Colloidal HfO₂ Nanocrystals with Unique Morphologies and New Self‐Assembly Features