Nuclear magnetic resonance studies of diamond

Reynhardt, E. C.; High, Grant L.

doi:10.1016/s0079-6565(00)00025-x

Cited by 31 publications

(32 citation statements)

References 52 publications

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“…Low natural abundance of 13 C isotope (1.07%) makes carbon materials to be nuclear spin diluted, which, in turn, yields 13 C nuclear spin diffusion to be quite slow. Detailed analysis of the spin diffusion in diamonds [ 49 – 51 ] shows that for the concentration of paramagnetic centers all 13 C nuclei, excluding those located inside the sphere of diffusion barrier radius, relax via spin diffusion. Increase in causes an increase in the number of 13 C nuclei which relax directly and decrease of those that relax via spin diffusion.…”

Section: Experimental Results and Calculation Of Ion-particle Distancmentioning

confidence: 99%

Towards Determination of Distances Between Nanoparticles and Grafted Paramagnetic Ions by NMR Relaxation

Panich

Sergeev

2017

Appl Magn Reson

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We developed an approach for determining distances between carbon nanoparticles and grafted paramagnetic ions and molecules by means of nuclear spin–lattice relaxation data. The approach was applied to copper-, cobalt- and gadolinium-grafted nanodiamonds, iron-grafted graphenes, manganese-grafted graphene oxide and activated carbon fibers that adsorb paramagnetic oxygen molecules. Our findings show that the aforementioned distances vary in the range of 2.7–5.4 Å and that the fixation of paramagnetic ions to nanoparticles is most likely implemented by means of the surface functional groups. The nuclear magnetic resonance data data are compared with the results of electron paramagnetic resonance measurements and density functional theory calculations.

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Section: Experimental Results and Calculation Of Ion-particle Distancmentioning

confidence: 99%

Towards Determination of Distances Between Nanoparticles and Grafted Paramagnetic Ions by NMR Relaxation

Panich

Sergeev

2017

Appl Magn Reson

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“…Later after a minute long probe transfer to the NMR spectrometer, an enhancement factor of about 45 is observed. Please note that for this type of sample it takes a very long time for the thermal polarisation to build up at B=7 T, see also [22]; the thermal spectrum was measured after 13 h. and a a , We note two resonance points A 1 and A 2 .The polarisation is transferred between the dressed state of the electron spin and the nuclear spin during a quasi-adiabatic sweep through these resonances (see supplementary information for additional details).…”

Section: Methodsmentioning

confidence: 95%

Optically induced dynamic nuclear spin polarisation in diamond

et al. 2016

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The sensitivity of magnetic resonance imaging (MRI) depends strongly on nuclear spin polarisation and, motivated by this observation, dynamical nuclear spin polarisation has recently been applied to enhance MRI protocols (Kurhanewicz et al 2011 Neoplasia 13 81). Nuclear spins associated with the 13 C carbon isotope (nuclear spin I=1/2) in diamond possess uniquely long spin lattice relaxation times (Reynhardt and High 2011 Prog. Nucl. Magn. Reson. Spectrosc. 38 37). If they are present in diamond nanocrystals, especially when strongly polarised, they form a promising contrast agent for MRI. Current schemes for achieving nuclear polarisation, however, require cryogenic temperatures.Here we demonstrate an efficient scheme that realises optically induced 13 C nuclear spin hyperpolarisation in diamond at room temperature and low ambient magnetic field. Optical pumping of a nitrogen-vacancy centre creates a continuously renewable electron spin polarisation which can be transferred to surrounding 13 C nuclear spins. Importantly for future applications we also realise polarisation protocols that are robust against an unknown misalignment between magnetic field and crystal axis.

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“…With sufficient microwave power to overcome the unfavorable field dependence, SE can generate large DNP enhancements as shown in a trityl-doped solution in a capillary tube held in a cylindrical microwave resonator [31*]. Despite unfavorable field dependence, the option of SE can be exclusive to highly diluted paramagnetic species, such as naturally occurring electron centers in diamonds [117; 118; 119; 120], γ-ray irradiated organic solids [121] and sparsely dye-doped systems in which non-Boltzmann electron spin polarization can be obtained from photoexcited triplets [122; 123]. …”

Section: Polarizing Agents For Dnp In Dielectric Solidsmentioning

confidence: 99%

Polarizing agents and mechanisms for high-field dynamic nuclear polarization of frozen dielectric solids

2011

Solid State Nuclear Magnetic Resonance

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This article provides an overview of polarizing mechanisms involved in high-frequency dynamic nuclear polarization (DNP) of frozen biological samples at temperatures maintained using liquid nitrogen, compatible with contemporary magic-angle spinning (MAS) nuclear magnetic resonance (NMR). Typical DNP experiments require unpaired electrons that are usually exogenous in samples via paramagnetic doping with polarizing agents. Thus, the resulting nuclear polarization mechanism depends on the electron and nuclear spin interactions induced by the paramagnetic species. The Overhauser Effect (OE) DNP, which relies on time-dependent spin-spin interactions, is excluded from our discussion due the lack of conducting electrons in frozen aqueous solutions containing biological entities. DNP of particular interest to us relies primarily on time-independent, spin interactions for significant electron-nucleus polarization transfer through mechanisms such as the Solid Effect (SE), the Cross Effect (CE) or Thermal Mixing (TM), involving one, two or multiple electron spins, respectively. Derived from monomeric radicals initially used in DNP experiments, bi- or multiple-radical polarizing agents facilitate CE/TM to generate significant NMR signal enhancements in dielectric solids at low temperatures (< 100 K). For example, large DNP enhancements (~300 times at 5 T) from a biologically compatible biradical, 1-(TEMPO-4-oxy)-3-(TEMPO-4-amino)propan-2-ol (TOTAPOL), have enabled high-resolution MAS NMR in sample systems existing in submicron domains or embedded in larger biomolecular complexes. The scope of this review is focused on recently developed DNP polarizing agents for high-field applications and leads up to future developments per the CE DNP mechanism. Because DNP experiments are feasible with a solid-state microwave source when performed at <20 K, nuclear polarization using lower microwave power (< 100 mW) is possible by forcing a high proportion of biradicals to fulfill the frequency matching condition of CE (two EPR frequencies separated by the NMR frequency) using the strategies involving hetero-radical moieties and/or molecular alignment. In addition, the combination of an excited triplet and a stable radical might provide alternative DNP mechanisms without the microwave requirement.

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Nuclear magnetic resonance studies of diamond

Cited by 31 publications

References 52 publications

Towards Determination of Distances Between Nanoparticles and Grafted Paramagnetic Ions by NMR Relaxation

Towards Determination of Distances Between Nanoparticles and Grafted Paramagnetic Ions by NMR Relaxation

Optically induced dynamic nuclear spin polarisation in diamond

Polarizing agents and mechanisms for high-field dynamic nuclear polarization of frozen dielectric solids

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