A case study on the influence of hydrophilicity on the signal enhancement by dynamic nuclear polarization

Döller, Sonja C.; Gutmann, Torsten; Hoffmann, Markus M.; Buntkowsky, Gerd

doi:10.1016/j.ssnmr.2022.101829

Cited by 4 publications

(10 citation statements)

References 54 publications

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“…This indicates the involvement of motions of the PEG units on a timescale shorter than the inverse resonance frequency or a larger spatial distance between the carbons of the surfactants confined in the MCM 41 as compared to those in the SBA-15 . 49,50 As discussed above, the AMUPol molecule is small enough to be confined into the pores of the mesoporous MCM 41. Therefore, it is unlikely that the smaller pore size leads to considerably higher distance between the carbon atoms of the surfactants and the polarizing agent.…”

Section: Characterization Of the Mesoporous Silica Materialsmentioning

confidence: 96%

“…This is in agreement with observations made in earlier works concerning similar surfactant systems. 41,49,50 The signals of the indirect polarization pathway are caused by the transfer of polarization from the proton reservoir to the observed carbon nucleus. This allows for the observation of nuclei farther away from the polarizing agent, since the polarization can travel through the whole sample via the proton reservoir.…”

Section: Line Width Analysismentioning

confidence: 99%

“…This distinction allows for site-specific probing in crowded spectra like those obtained from protein samples 42,47 or RNA, 48 the investigation of protein−ligand binding, 43 or the determination of active dynamics under low-temperature DNP conditions. 41,49 In previous works, 50 it has been shown that DNP-enhanced ssNMR is a suitable method to probe the interactions of guest molecules with a mesoporous host materials, allowing the development of models and the description of dynamic processes inside of the pores. Therefore, the aim of this work is to apply this methodology in an attempt to understand how different classes of surfactants interact with a host material with a hydrophilic surface, namely mesoporous silica, for the purpose of developing a model of their arrangement in the pores.…”

Section: Introductionmentioning

confidence: 99%

“…The indirect polarization transfer pathway is facilitated by 1 H–X (X = 13 C, 15 N) cross-relaxation of molecular groups due to the presence of adequate dynamics for which the nuclear Overhauser effect type of mechanism is operative. , The two pathways show opposite signs in the recorded NMR signal, leading to a superposition of two sets of resonances. This distinction allows for site-specific probing in crowded spectra like those obtained from protein samples , or RNA, the investigation of protein–ligand binding, or the determination of active dynamics under low-temperature DNP conditions. , …”

Section: Introductionmentioning

confidence: 99%

“…The contribution of the direct and indirect polarization transfer pathways is analyzed for the carbons located in the PEG moiety of each surfactant. To achieve comparability for all investigated samples, an approach based on relative intensities is employed . Finally, differential scanning calorimetry (DSC) is employed to probe the phase behavior of the different surfactants while confined in the mesoporous silica materials, which is compared to those of the AMUPol dissolved in the bulk surfactants.…”

Section: Introductionmentioning

confidence: 99%

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Direct and Indirect DNP NMR Uncovers the Interplay of Surfactants with Their Mesoporous Host Material

et al. 2023

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Two different mesoporous silica materials (SBA-15 and MCM 41) were impregnated with four different, commercially available surfactants, namely, E5, PEG 200, C10E6, and Triton X-100. Differential scanning calorimetry was employed to confirm the confinement of the surfactants in the pores of their host materials. Dynamic nuclear polarization enhanced solid state 13C magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra were recorded for these materials, showing that both the direct as well as the indirect polarization transfer pathways are active for the carbons of the polyethylene glycol moieties of the surfactants. The presence of the indirect polarization pathway implies the presence of molecular motion with correlation times faster than the inverse Larmor frequency of the observed signals. The intensities of the signals were determined, and an approach based on relative intensities was employed to ensure comparability throughout the samples. From these data, the interactions of the surfactants with the pore walls could be determined. Additionally, a model describing the surfactants’ arrangement in the pores was developed. It was concluded that all carbons of the hydrophilic surfactants, E5 and PEG 200, interact with the silica walls in a similar fashion, leading to similar polarization transfer pathway patterns for all observed signals. For the amphiphilic surfactants C10E6 and Triton X-100, the terminal hydroxyl group mediates the majority of the interactions with the pore walls and the polarizing agent.

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Section: Characterization Of the Mesoporous Silica Materialsmentioning

confidence: 96%

Section: Line Width Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Direct and Indirect DNP NMR Uncovers the Interplay of Surfactants with Their Mesoporous Host Material

et al. 2023

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Surface-Assisted Selective Air Oxidation of Phosphines Adsorbed on Activated Carbon

Hoefler,

Jackson,

Blümel

2024

Inorg. Chem.

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Trialkyl- and triarylphosphines readily adsorb onto the surface of porous activated carbon (AC) even in the absence of solvents through van der Waals interactions between the lone electron pair and the AC surface. This process has been proven by solid-state NMR techniques. Subsequently, it is demonstrated that the AC enables the fast and selective oxidation of adsorbed phosphines to phosphine oxides at ambient temperature in air. In solution, trialkylphosphines are oxidized to a variety of P(V) species when exposed to the atmosphere, while neat or dissolved triarylphosphines cannot be oxidized with air. When the trialkyl- and triarylphosphines P n Bu3 (1), PEt3, (2), P n Oct3 (3), PMe t Bu2 (4), PCy3 (5), and PPh3 (6) are adsorbed in a mono- or submonolayer on the surface of AC, in the absence of a solvent and at ambient temperature, they are quantitatively oxidized to the adsorbed phosphine oxides, 1 ox –6 ox , once air is admitted. No formation of any unwanted P(V) side products or water adducts is observed. The phosphine oxides can then be recovered in good yields by washing them off of the AC. The oxidation is likely facilitated by a radical activation of molecular oxygen due to delocalized electrons on the aromatic surface coating of AC, as proven by ESR. This easy and inexpensive oxidation method renders hydrogen peroxide or other oxidizers unnecessary and is broadly applicable to sterically hindered and even to air-stable triarylphosphines. Phosphines adsorbed at lower surface coverages on AC oxidize at a faster rate. All oxidation reactions were monitored by solution- and solid-state NMR spectroscopy.

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Hyperpolarisation techniques

Equbal,

Mewis

2023

Nuclear Magnetic Resonance

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This chapter focuses on the literature published in 2022, covering hyperpolarisation techniques associated with NMR. The literature reviewed relates to the hyperpolarisation techniques of dynamic nuclear polarisation (DNP), spin-exchange optical pumping (SEOP), parahydrogen induced polarisation (PHIP) and signal amplification by reversible exchange (SABRE). In addition to reviewing studies that have been conducted using these techniques, a number of reports are discussed that relate to advances in associated hardware and instrumentation.

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A case study on the influence of hydrophilicity on the signal enhancement by dynamic nuclear polarization

Cited by 4 publications

References 54 publications

Direct and Indirect DNP NMR Uncovers the Interplay of Surfactants with Their Mesoporous Host Material

Direct and Indirect DNP NMR Uncovers the Interplay of Surfactants with Their Mesoporous Host Material

Surface-Assisted Selective Air Oxidation of Phosphines Adsorbed on Activated Carbon

Hyperpolarisation techniques

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