%0 Journal Article %J The Journal of Physical Chemistry C %D 2019 %T Indirect Detection of Short-lived Hydride Intermediates of Iridium N-Heterocyclic Carbene Complexes via Chemical Exchange Saturation Transfer (CEST) Spectroscopy %A Stephan Knecht %A Sara Hadjiali %A Danila A Barskiy %A Alexander Pines %A Grit Sauer %A Alexey Kiryutin %A Konstantin Ivanov %A Alexandra Yurkovskaya %A Gerd Buntkowsky %X

For the first time, chemical exchange saturation transfer (CEST) nuclear magnetic resonance (NMR) is utilized to study short-lived hydride intermediates in the catalytic cycle of an organometallic complex [Ir(IMes)(Py)3(H)2]Cl. These complexes are typically not observable by other NMR techniques because they are low concentrated and undergo reversible ligand exchange with the main complex. The intermediatecomplexes [Ir(Cl)(IMes)(Py)2(H)2] and [Ir(CD3OD)(IMes)(Py)2(H)2]are detected, assigned, and characterized in solution, in situ and at room temperature. Understanding the spin dynamics in these complexes is necessary for enhancing the performance of the nuclear spin hyperpolarization technique signal amplification by reversible exchange. By eliminating [Ir(Cl (IMes)(Py)2(H)2] and manipulating the spin system by radiofrequency irradiation, the nuclear spin singlet lifetime of the hydride protons was increased by more than an order of magnitude, from 2.2 ± 0.1 to 27.2 ± 1.2 s. Because of its simplicity and ability to unravel unobservable chemical species, the utilized CEST NMR approach has a large application potential for studying short-lived hydride intermediates incatalytic reactions.

%B The Journal of Physical Chemistry C %8 06/2019 %G eng %U https://pubs.acs.org/doi/10.1021/acs.jpcc.9b04179# %R https://doi.org/10.1021/acs.jpcc.9b04179 %0 Journal Article %J Progress in Nuclear Magnetic Resonance Spectroscopy %D 2019 %T SABRE: Chemical kinetics and spin dynamics of the formation of hyperpolarization %A Danila Barskiy %A Stephan Knecht %A Alexandra Yurkovskaya %A Konstantin Ivanov %B Progress in Nuclear Magnetic Resonance Spectroscopy %8 05/2019 %G eng %U https://www.sciencedirect.com/science/article/pii/S007965651930024X %R 10.1016/j.pnmrs.2019.05.005 %0 Journal Article %J Nature Materials %D 2017 %T Distance-dependent magnetic resonance tuning as a versatile MRI sensing platform for biological targets %A Choi, J.-S. %A Kim, S. %A Yoo, D. %A Shin, T.-H. %A Kim, H. %A Gomes, M.D. %A Kim, S. H. %A Pines, A. %A Cheon, J. %B Nature Materials %V 16 %P 537 - 542 %G eng %N 5 %& 537 %0 Journal Article %J Journal of Chemical Physics %D 2010 %T Investigation of antirelaxation coatings for alkali-metal vapor cells using surface science techniques %A Seltzer, S. J. %A Michalak, D. J. %A Donaldson, M. H. %A Balabas, M. V. %A Barber, S. K. %A Bernasek, S. L. %A Bouchiat, M. A. %A Hexemer, A. %A Hibberd, A. M. %A Kimball, D. F. J. %A Jaye, C. %A Karaulanov, T. %A Narducci, F. A. %A Rangwala, S. A. %A Robinson, H. G. %A Shmakov, A. K. %A Voronov, D. L. %A Yashchuk, V. V. %A Pines, A. %A Budker, D. %K SPECTROSCOPY %X

Many technologies based on cells containing alkali-metal atomic vapor benefit from the use of antirelaxation surface coatings in order to preserve atomic spin polarization. In particular, paraffin has been used for this purpose for several decades and has been demonstrated to allow an atom to experience up to 10 000 collisions with the walls of its container without depolarizing, but the details of its operation remain poorly understood. We apply modern surface and bulk techniques to the study of paraffin coatings in order to characterize the properties that enable the effective preservation of alkali spin polarization. These methods include Fourier transform infrared spectroscopy, differential scanning calorimetry, atomic force microscopy, near-edge x-ray absorption fine structure spectroscopy, and x-ray photoelectron spectroscopy. We also compare the light-induced atomic desorption yields of several different paraffin materials. Experimental results include the determination that crystallinity of the coating material is unnecessary, and the detection of CvC double bonds present within a particular class of effective paraffin coatings. Further study should lead to the development of more robust paraffin antirelaxation coatings, as well as the design and synthesis of new classes of coating materials. (C) 2010 American Institute of Physics. [doi:10.1063/1.3489922]

%B Journal of Chemical Physics %V 133 %P 144703 %8 October 11, 2010 %@ 0021-9606 %G English %U http://link.aip.org/link/doi/10.1063/1.3489922 %N 14 %9 Article %M WOS:000283200400049 %] 144703 %! Investigation of antirelaxation coatings for alkali-metal vapor cells using surface science techniques %& 144703 %R 10.1063/1.3489922 %0 Journal Article %J Physical Review A %D 2008 %T Submillimeter-resolution magnetic resonance imaging at the Earth's magnetic field with an atomic magnetometer %A Xu, S. %A Crawford, C. W. %A Rochester, S. %A Yashchuk, V. %A Budker, D. %A Pines, A. %K nmr %X

Magnetic resonance imaging in the Earth's magnetic field is achieved using a sensitive atomic magnetometer for detection. We demonstrate images with a submillimeter resolution by recording the flow of two water paths meeting at a T-shaped mixer. The high homogeneity of the Earth's field allows the use of weak gradient fields which circumvent the concomitant-field effect. To distinguish the two input channels, we employed selective polarization, which is a unique and noninvasive labeling method for low-field magnetic resonance imaging. Our technique imposes minimal physical constraints on the object under study, in contrast to conventional high-field magnetic resonance imaging. This technique is applicable for microfluidic imaging in laboratory-on-a-chip devices.

%B Physical Review A %V 78 %8 Jul %@ 1050-2947 %G English %U ://WOS:000258180300141 %N 1 %M WOS:000258180300141 %! Submillimeter-resolution magnetic resonance imaging at the Earth's magnetic field with an atomic magnetometer %R Doi 10.1103/Physreva.78.013404 %0 Journal Article %J Applied Physics Letters %D 2006 %T Application of atomic magnetometry in magnetic particle detection %A Xu, S. %A Donaldson, M. H. %A Pines, A. %A Rochester, S. M. %A Budker, D. %A Yashchuk, V. V. %K system %X

The authors demonstrate the detection of magnetic particles carried by water in a continuous flow using an atomic magnetic gradiometer. Studies on three types of magnetic particles are presented: a single cobalt particle (diameter similar to 150 mu m, multidomain), a suspension of superparamagnetic magnetite particles (diameter similar to 1 mu m), and ferromagnetic cobalt nanoparticles (diameter similar to 10 nm). Estimated detection limits are 20 mu m diameter for a single cobalt particle at a water flow rate of 30 ml/min, 5x10(3) magnetite particles at 160 ml/min, and 50 pl for the ferromagnetic fluid of cobalt nanoparticles at 130 ml/min. Possible applications of their method are discussed.

%B Applied Physics Letters %V 89 %8 Nov 27 %@ 0003-6951 %G English %U ://WOS:000242538500151 %N 22 %M WOS:000242538500151 %! Application of atomic magnetometry in magnetic particle detection %R Doi 10.1063/1.2400077 %0 Journal Article %J Proceedings of the National Academy of Sciences of the United States of America %D 2006 %T Magnetic resonance imaging with an optical atomic magnetometer %A Xu, S. J. %A Yashchuk, V. V. %A Donaldson, M. H. %A Rochester, S. M. %A Budker, D. %A Pines, A. %K gas %X

We report an approach for the detection of magnetic resonance imaging without superconducting magnets and cryogenics: optical atomic magnetometry. This technique possesses a high sensitivity independent of the strength of the static magnetic field, extending the applicability of magnetic resonance imaging to low magnetic fields and eliminating imaging artifacts associated with high fields. By coupling with a remote-detection scheme, thereby improving the filling factor of the sample, we obtained time-resolved flow images of water with a temporal resolution of 0.1 s and spatial resolutions of 1.6 mm perpendicular to the flow and 4.5 mm along the flow. Potentially inexpensive, compact, and mobile, our technique provides a viable alternative for MRI detection with substantially enhanced sensitivity and time resolution for various situations where traditional MRI is not optimal.

%B Proceedings of the National Academy of Sciences of the United States of America %V 103 %P 12668-12671 %8 Aug 22 %@ 0027-8424 %G English %U ://WOS:000240035900006 %N 34 %M WOS:000240035900006 %! Magnetic resonance imaging with an optical atomic magnetometer %R Doi 10.1073/Pnas.0605396103 %0 Journal Article %J Physical Review Letters %D 2004 %T Hyperpolarized xenon nuclear spins detected by optical atomic magnetometry %A Yashchuk, V. V. %A Granwehr, J. %A Kimball, D. F. %A Rochester, S. M. %A Trabesinger, A. H. %A Urban, J. T. %A Budker, D. %A Pines, A. %K mri %X

We report the use of an atomic magnetometer based on nonlinear magneto-optical rotation with frequency-modulated light to detect nuclear magnetization of xenon gas. The magnetization of a spin-exchange-polarized xenon sample (1.7 cm(3) at a pressure of 5 bars, natural isotopic abundance, polarization 1%), prepared remotely to the detection apparatus, is measured with an atomic sensor. An average magnetic field of similar to10 nG induced by the xenon sample on the 10 cm diameter atomic sensor is detected with signal-to-noise ratio similar to10, limited by residual noise in the magnetic environment. The possibility of using modern atomic magnetometers as detectors of nuclear magnetic resonance and in magnetic resonance imaging is discussed. Atomic magnetometers appear to be ideally suited for emerging low-field and remote-detection magnetic resonance applications.

%B Physical Review Letters %V 93 %8 Oct 15 %@ 0031-9007 %G English %U ://WOS:000224533300012 %N 16 %M WOS:000224533300012 %! Hyperpolarized xenon nuclear spins detected by optical atomic magnetometry %R Doi 10.1103/Physrevlett.93.160801 %0 Journal Article %J Proceedings of the National Academy of Sciences of the United States of America %D 2001 %T Functionalized xenon as a biosensor %A Spence, M. M. %A Rubin, S. M. %A Dimitrov, I. E. %A Ruiz, E. J. %A Wemmer, D. E. %A Pines, A. %A Yao, S. Q. %A Tian, F. %A Schultz, P. G. %K mri %X

The detection of biological molecules and their interactions is a significant component of modern biomedical research. In current biosensor technologies, simultaneous detection is limited to a small number of analytes by the spectral overlap of their signals. We have developed an NMR-based xenon biosensor that capitalizes on the enhanced signal-to-noise, spectral simplicity, and chemical-shift sensitivity of laser-polarized xenon to detect specific biomolecules at the level of tens of nanomoles. We present results using xenon "functionalized" by a biotin-modified supramolecular cage to detect biotin-avidin binding. This biosensor methodology can be extended to a multiplexing assay for multiple analytes.

%B Proceedings of the National Academy of Sciences of the United States of America %V 98 %P 10654-10657 %8 Sep 11 %@ 0027-8424 %G English %U ://WOS:000170966800030 %N 19 %M WOS:000170966800030 %! Functionalized xenon as a biosensor %R Doi 10.1073/Pnas.191368398 %0 Journal Article %J Journal of Chemical Physics %D 1999 %T NMR study of InP quantum dots: Surface structure and size effects %A Tomaselli, M. %A Yarger, J. L. %A Bruchez, M. %A Havlin, R. H. %A deGraw, D. %A Pines, A. %A Alivisatos, A. P. %K clusters %X

We report the results of P-31 NMR measurements on trioctylphosphine oxide (TOPO) passivated InP quantum dots. The spectra show distinct surface-capping sites, implying a manifold of crystal-ligand bonding configurations. Two In P-31 surface components are resolved and related to different electronic surroundings. With decreasing particle size the In P-31 core resonance reveals an increasing upfield chemical shift related to the overall size dependence of the InP electronic structure. (C) 1999 American Institute of Physics. [S0021-9606(99)70718-X].

%B Journal of Chemical Physics %V 110 %P 8861-8864 %8 May 8 %@ 0021-9606 %G English %U ://WOS:000080073200002 %N 18 %M WOS:000080073200002 %! NMR study of InP quantum dots: Surface structure and size effects %R Doi 10.1063/1.478858 %0 Journal Article %J Applied Physics Letters %D 1998 %T Low field magnetic resonance images of polarized noble gases obtained with a dc superconducting quantum interference device %A Augustine, M. P. %A Wong-Foy, A. %A Yarger, J. L. %A Tomaselli, M. %A Pines, A. %A TonThat, D. M. %A Clarke, J. %K mri %X

Using a low transition temperature superconducting quantum interference device as a detector, we have obtained magnetic resonance images of laser-polarized He-3 gas and solid Xe-129 at 4.2 K in magnetic fields as low as 0.54 mT (He-3) and 1 mT (Xe-129), corresponding to Larmor frequencies of 17.6 and 11.8 kHz, respectively. The experimental resolution of the images is similar to 500 mu m for He-3 ill the gas phase and similar to 950 mu m for Xe-129 in the solid state. (C) 1998 American Institute of Physics.

%B Applied Physics Letters %V 72 %P 1908-1910 %8 Apr 13 %@ 0003-6951 %G English %U ://WOS:000073054300038 %N 15 %M WOS:000073054300038 %! Low field magnetic resonance images of polarized noble gases obtained with a dc superconducting quantum interference device %R Doi 10.1063/1.121223 %0 Journal Article %J Physical Review B %D 1998 %T Scalar and anisotropic J interactions in undoped InP: A triple-resonance NMR study %A Tomaselli, M. %A deGraw, D. %A Yarger, J. L. %A Augustine, M. P. %A Pines, A. %K solids %X

The heteronuclear J-coupling tensor between nearest neighbor P-31 and In-113 spins in undoped InP is investigated by means of In-113-->P-31 polarization transfer under rapid magic angle spinning (MAS). The scalar contribution can be measured directly and is found to have the value \J(iso)(P-31-In-113,In-115)\ = (225+/-10) Hz. The principal value of the traceless anisotropic J-coupling tensor (pseudodipolar coupling) is determined to be J(aniso)(P-31-In-113,In-115)= 2/3[J(parallel to)(P-31-In-113,In-115)-J(perpendicular to)(P-31-In-113,In-115)] = (813+/-50) or (1733+/-50) Hz, assuming axial symmetry with the principal axis parallel to the In-P bond. Our values deviate from those reported previously [M. Engelsberg and R. E. Norberg, Phys. Rev. B 5, 3395 (1972)] [based on a moment analysis of the P-31 resonance \J(iso)(31P-In-113,In-115)\ = 350 Hz and J(aniso)(P-31-In-113,In-115) = 1273 Hz], but confirm the postulate that the nearest neighbor P-31-In-113,In-115 magnetic dipolar and pseudodipolar interactions are of the same order of magnitude and partially cancel each other.

%B Physical Review B %V 58 %P 8627-8633 %8 Oct 1 %@ 0163-1829 %G English %U ://WOS:000076232100075 %N 13 %M WOS:000076232100075 %! Scalar and anisotropic J interactions in undoped InP: A triple-resonance NMR study %R Doi 10.1103/Physrevb.58.8627 %0 Journal Article %J Journal of Chemical Physics %D 1995 %T C-13 Chemical-Shift Tensor Correlation Via Spin-Diffusion in Solid Tropolone Using Switched-Angle Spinning Spectroscopy %A Larsen, R. G. %A Lee, Y. K. %A He, B. %A Yang, J. O. %A Luz, Z. %A Zimmermann, H. %A Pines, A. %K spectra %X

In switched-angle spinning spectroscopy (SAS) a sample is spun about different angles, beta, relative to the magnetic field, during various periods of the experiment. In the present work, SAS is combined with two-dimensional exchange spectroscopy in order to correlate carbon-13 chemical shift tensors of the carbonyl (1) and hydroxyl (2) carbons of tropolone. Experiments were performed on a sample enriched to 25 at. % in each of these sites (at different molecules). At this level of enrichment the dominant exchange mechanism between the two sites involves spin diffusion, The experiment consists of a preparation period during which the sample spins at the magic angle and the magnetization of one of the sites is quenched by means of a selective pulse sequence. During the rest of the experiment the sample spins with its axis away from the magic angle except for a short period just before the detection where the axis is switched to the magic angle in order to select the magnetization to be detected. Experiments were performed for all four possible combinations of the initial and final magnetizations, thus providing chemical shift correlations between carbons 1,1',2, and 2' in the two magnetically inequivalent (but symmetry related) molecules in the unit cell. Combining these results with the known crystal structure of tropolone (neglecting a small tilt between the perpendicular to the molecular plane and the crystallographic c-axis) provides information on the orientation and magnitude of the chemical shift tensors of the two types of carbons, The principal values (in ppm) are sigma(xx)(1)=65, sigma(yy)(1)=33, sigma(zz)(1)=-98, sigma(xx)(2)=77, sigma(yy)(2)=17, and sigma(zz)(2)=-94. Assuming sigma(zz) to be perpendicular to the molecular plane, the orientations of the sigma(yy) s' are 12 degrees off the C-1=0 bond (toward the hydroxyl carbon) for carbon 1 and 10 degrees off the C-3=C-2 bond (away from the carbonyl carbon) for carbon 2. (C) 1995 American Institute of Physics.

%B Journal of Chemical Physics %V 103 %P 9844-9854 %8 Dec 8 %@ 0021-9606 %G English %U ://WOS:A1995TH65700040 %N 22 %M WOS:A1995TH65700040 %! C-13 Chemical-Shift Tensor Correlation Via Spin-Diffusion in Solid Tropolone Using Switched-Angle Spinning Spectroscopy %R Doi 10.1063/1.469951 %0 Journal Article %J Analytical Chemistry %D 1995 %T Detection of N-14 and CL-35 in Cocaine Base and Hydrochloride Using NQR, NMR and SQUID Techniques %A Yesinowski, J.Y. %A Buess, M.L. %A Garroway, A.N. %A Zeigeweid, M. %A Pines, A. %B Analytical Chemistry %P 2256-2263 %G eng %N 34 %! Detection of N-14 and CL-35 in Cocaine Base and Hydrochloride Using NQR, NMR and SQUID Techniques %0 Journal Article %J Chinese Journal of Microwave and Radio Frequency Spectroscopy %D 1983 %T Multiple quantum NMR spectroscopy %A Ye, C. %A Tang, J. %A Pines, A. %B Chinese Journal of Microwave and Radio Frequency Spectroscopy %V 1 %P 12 %G eng %! Multiple quantum NMR spectroscopy %0 Journal Article %J Journal of Chemical Physics %D 1983 %T Multiple-Quantum Nmr in Solids %A Yen, Y. S. %A Pines, A. %B Journal of Chemical Physics %V 78 %P 3579-3582 %@ 0021-9606 %G English %U ://WOS:A1983QG96300031 %N 6 %M WOS:A1983QG96300031 %! Multiple-Quantum Nmr in Solids %R Doi 10.1063/1.445185 %0 Journal Article %J Journal of Magnetic Resonance %D 1983 %T Spin Diffusion and Orientation Dependence of Deuterium T1 in Solids %A Ye, C. %A Eckman, R. %A Pines, A. %B Journal of Magnetic Resonance %V 55 %P 334-337 %@ 1090-7807 %G English %U ://WOS:A1983RR92300016 %N 2 %M WOS:A1983RR92300016 %! Spin Diffusion and Orientation Dependence of Deuterium T1 in Solids %R Doi 10.1016/0022-2364(83)90245-7