Boosting sensitivity and suppressing artifacts via multi-acquisition in direct polarization NMR experiments with small flip-angle pulses

Fu, Riqiang; Hernández‐Maldonado, Arturo J.

doi:10.1016/j.jmr.2018.05.015

Cited by 4 publications

(3 citation statements)

References 26 publications

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“…Chemical shifts are relative to the CF 3 group in flufenamic acid {N- [3-(trifluoromethyl)phenyl]anthranilic acid} defined as −61.5 ppm. [63] Theoretical Studies: The theoretical simulations of finite systems were performed using molecular mechanics (MM) using the universal force field (UFF) [64] and density functional theory (DFT), with a 6-31G(d) basis set functions and the Becke three-parameter Lee-Yang-Parr exchangecorrelation functional (B3LYP). [65,66] The binding energies (E b ) were evaluated considering the following equation: E b = E hBN+nF − (E hBN + E nF ), in which n is the number of F atoms bonded to BN and E hBN+nF , E hBN , and E nF, respectively, the total energy for a fluorinated BN, unmodified BN, and the F atoms.…”

Section: Methodsmentioning

confidence: 99%

Gas‐Phase Fluorination of Hexagonal Boron Nitride

et al. 2021

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Hexagonal boron nitride (hBN) has received much attention in recent years as a 2D dielectric material with potential applications ranging from catalysts to electronics. hBN is a stable covalent compound with a planar hexagonal lattice and is relatively unreactive to most chemical environments, making the chemical functionalization of hBN challenging. Here, a simple, scalable strategy to fluorinate hBN using a direct gas‐phase fluorination technique is reported. The nature of fluorine bonding to the hBN lattice and their chemical coordination are described based on various characterization studies and theoretical models. The fluorine functionalized hBN shows a bandgap reduction and displays a semiconducting behavior due to the fluorination process. Additionally, the fluorinated hBN shows significant improvement in its thermal and friction properties, which could be substantial in applications such as lubricants and thermal fluids. Theory and simulations reveal that the enhanced friction properties of fluorinated hBN result from reduced inter‐planar interaction energy by electrostatic repulsion of intercalated fluorine atoms between hBN layers without significant disruption of the in‐plane lattice. This technique paves the way for the fluorination of several other 2D structures for various applications such as magnetism and functional nanoscale electronic devices.

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Section: Methodsmentioning

confidence: 99%

Gas‐Phase Fluorination of Hexagonal Boron Nitride

et al. 2021

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“…These units are unrelated to concentration; rather, they make the frequency scale independent of the spectrometer field strength, thereby allowing sample comparison between different NMR instruments. The DP multiacquisition scheme 71 at 40 kHz spinning speed resulted in identifying the isotropic chemical shifts (δ iso , characteristic of particular species) of F − in our treated HAPs. The spectra (Figure 2a) exhibit a pair of broad minor and major resonances at δ iso ( 19 F) = −91.5 to −93.0 ppm and δ iso ( 19 F) = −101.9 to −103.8 ppm, respectively.…”

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Internalization of Fluoride in Hydroxyapatite Nanoparticles

Mosiman

Sutrisno

et al. 2021

Environ. Sci. Technol.

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Hydroxyapatite (HAP) is a cost-effective material to remove excess levels of fluoride from water. Historically, HAP has been considered a fluoride adsorbent in the environmental engineering community. This paper substantiates an uptake paradigm that has recently gained disparate support: assimilation of fluoride to bulk apatite lattice sites in addition to surface lattice sites. Pellets of HAP nanoparticles (NPs) were packed into a fixed-bed media filter to treat solutions containing 30 mg-F/L (1.58 mM) at pH 8, yielding an uptake of 15.97 ± 0.03 mg-F/g-HAP after 864 h. Solid-state 19 F and 13 C magicangle spinning nuclear magnetic resonance spectroscopy demonstrated that all removed fluoride is apatitic. A transmission electron microscopy analysis of particle size distribution, morphology, and crystal habit resulted in the development of a model to quantify adsorption and total fluoride capacity. Low-and high-estimate median adsorption capacities were 2.40 and 6.90 mg-F/g-HAP, respectively. Discrepancies between experimental uptake and adsorption capacity indicate the range of F − that internalizes to satisfy conservation of mass. The model was developed to demonstrate that F − internalization in HAP NPs occurs under environmentally relevant conditions and as a tool to understand the extent of F − internalization in HAP NPs of any kind.

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“…Solid-State 19 F MAS NMR Spectroscopy: Solid-state 19 F NMR spectroscopy was performed on a Bruker Avance 600 MHz NMR spectrometer using a Bruker HX 1.3 mm MAS probe, in which the 1 H channel was tuned to 19 F. The sample spinning rate was controlled by a Bruker pneumatic MAS unit at 48 kHz. The 19 F 90° pulse length was used and in all 19 F experiments, 2048 scans were collected for each sample.…”

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confidence: 99%

Resorcinarene Cavitand Polymers for the Remediation of Halomethanes and 1,4-Dioxane

Skala¹,

Yang²,

Klemes³

et al. 2019

Preprint

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Executive summary: Porous resorcinarene-containing polymers are used to remove halomethane disinfection byproducts and 1,4-dioxane from water. Disinfection byproducts such as trihalomethanes are some of the most common micropollutants found in drinking water. Trihalomethanes are formed upon chlorination of natural organic matter (NOM) found in many drinking water sources. Municipalities that produce drinking water from surface water sources struggle to remain below regulatory limits for CHCl3 and other trihalomethanes (80 mg L–1 in the United States). Inspired by molecular CHCl3⊂cavitand host-guest complexes, we designed a porous polymer comprised of resorcinarene receptors. These materials show higher affinity for halomethanes than a specialty activated carbon used for trihalomethane removal. The cavitand polymers show similar removal kinetics as activated carbon and have high capacity (49 mg g–1 of CHCl3). Furthermore, these materials maintain their performance in real drinking water and can be thermally regenerated under mild conditions. Cavitand polymers also outperform activated carbon in their adsorption of 1,4-dioxane, which is difficult to remove and contaminates many public water sources. These materials show promise for removing toxic organic micropollutants and further demonstrate the value of using supramolecular chemistry to design novel absorbents for water purification.

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Boosting sensitivity and suppressing artifacts via multi-acquisition in direct polarization NMR experiments with small flip-angle pulses

Cited by 4 publications

References 26 publications

Gas‐Phase Fluorination of Hexagonal Boron Nitride

Gas‐Phase Fluorination of Hexagonal Boron Nitride

Internalization of Fluoride in Hydroxyapatite Nanoparticles

Resorcinarene Cavitand Polymers for the Remediation of Halomethanes and 1,4-Dioxane

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