Structure, density and viscosity of water

Нефедов, В. Г.; Матвеев, В. В.

doi:10.32434/0321-4095-2021-137-4-96-105

Cited by 4 publications

(2 citation statements)

References 9 publications

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“…F NMR spectrum (see NMR discussion below), the XPS spectrum contains a signal at 684.9 eV which is consistent with the presence of CdF2 (FigureS10) 30. https://doi.org/10.26434/chemrxiv-2024-0md1d ORCID: https://orcid.org/0000-0002-1524-7503 Content not peer-reviewed by ChemRxiv.…”

supporting

confidence: 62%

Metal fluorides passivate II-VI and III-V quantum dots

VALLEIX,

Zhang,

Guillemeney

et al. 2024

Preprint

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The interaction between II-VI and III-V quantum dots (QDs) and metal fluorides is investigated using optical absorption, photoluminescence, and nuclear magnetic resonance spectroscopies. QDs with metal fluoride passivated surfaces were prepared by ligand exchange with anhydrous oleylammonium fluoride. The photoluminescence quantum yield (PLQY) of II-VI QD cores and core-shell structures are dramatically enhanced following ligand exchange, near unity in some cases, but only after exposure to air. In the case of InP QDs, oleylammonium fluoride induces a gradual etching of the crystal, yielding oleylamine, PH3, and InF3 coproducts, resulting in a remarkable increase in PLQY (up to 83%). The frequency and breadth of ν(N–H) bands in the infrared spectrum supports the assignment of oleylamine ligand binding to InP. The fluoride content (1.6–9.2 nm-2) is compared with the coverage of oleylamine ligands (2.3–5.1 nm-2) and demonstrates the formation of surfaces densely covered by metal fluoride and amine ligands. The relationship between the electrophilicity and small steric profile of metal fluoride surface ligands and their surface passivating effects on QDs is discussed.

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supporting

confidence: 62%

Metal fluorides passivate II-VI and III-V quantum dots

VALLEIX,

Zhang,

Guillemeney

et al. 2024

Preprint

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“…5 The difference in PLQY suggests that [R-NH 3 ] + [F] − (R = oleyl, n-octyl) displaces oleic acid, rather than cadmium oleate, and forms surface bound cadmium fluoride that is responsible for the PLQY enhancement (Scheme 3). X-ray photoelectron spectroscopy analysis of the product QDs supports the presence of the metal fluoride (Figures S23 and S24) coproducts (e.g., InF 3 (685.4 eV) and CdF 2 (684.9 eV)), 32 but the liquids 19 F NMR spectra of these samples gave little to no fluorine signal. This is typical of extended inorganic fluorides whose 19 F NMR line width is broadened by chemical shift anisotropy and dipolar couplings.…”

Section: T H Imentioning

confidence: 77%

Metal Fluorides Passivate II–VI and III–V Quantum Dots

Valleix,

Zhang,

Jordan

et al. 2024

Nano Lett.

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Quantum dots (QDs) with metal fluoride surface ligands were prepared via reaction with anhydrous oleylammonium fluoride. Carboxylate terminated II−VI QDs underwent carboxylate for fluoride exchange, while InP QDs underwent photochemical acidolysis yielding oleylamine, PH 3 , and InF 3 . The final photoluminescence quantum yield (PLQY) reached 83% for InP and near unity for core− shell QDs. Core-only CdS QDs showed dramatic improvements in PLQY, but only after exposure to air. Following etching, the InP QDs were bound by oleylamine ligands that were characterized by the frequency and breadth of the corresponding ν(N−H) bands in the infrared absorption spectrum. The fluoride content (1.6−9.2 nm −2 ) was measured by titration with chlorotrimethylsilane and compared with the oleylamine content (2.3−5.1 nm −2 ) supporting the formation of densely covered surfaces. The influence of metal fluoride adsorption on the air stability of QDs is discussed.

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Phase and structural transformations of water during ice melting

Nefedov¹,

Matveev²

2022

Vopr. Khim. Khim. Tekhnol.

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The processes of phase transformation of water during ice melting are considered. Possible structures of liquid water are analyzed, corresponding to the results of experimental measurements and computer simulation. It is shown that when ice melts, the tridymite structure breaks down into individual clusters, the lifetime of which ranges from 2 to 8 ps and increases with an increase in their molecular weight. A sharp increase in the density of liquid water at 00C is explained by the formation of clathrates during the introduction of water molecules into the cavity of the structure and an increase in the degree of coordination from 4.0 to 4.34. The most stable are water clusters, consisting of 12–20 molecules, the mixture of which determines the density of the liquid phase. Molecules in the middle of clusters can form additional hydrogen bonds with their nearest neighbors in the cluster framework. Thus, one or two framework molecules can have three acceptor and two donor bonds of A3D2 type. The central molecule is most likely of type A1D2 or A1D1. An example of calculating the density of water when taking into account clathrates and vacancies is given.

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Structure, density and viscosity of water

Cited by 4 publications

References 9 publications

Metal fluorides passivate II-VI and III-V quantum dots

Metal fluorides passivate II-VI and III-V quantum dots

Metal Fluorides Passivate II–VI and III–V Quantum Dots

Phase and structural transformations of water during ice melting

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