@article {3083, title = {Realization of portable room temperature nanodiamond 13C hyperpolarizer}, year = {Submitted}, author = {A. Ajoy and R. Nazaryan and E. Druga and K. Liu and B. Han and J.T. Oon and M. Gierth and R. Tsang and J.H. Walton and C.A. Meriles and J.A. Reimer and D. Suter and A. Pines} } @article {3169, title = {Two-electron-spin ratchets as a platform for microwave-free dynamic nuclear polarization of arbitrary material targets}, journal = {Nano Letters}, year = {In Press}, author = {P.R. Zangara and J. Henshaw and D. Pagliero and A. Ajoy and J. Reimer and A. Pines and C. Meriles} } @article {3170, title = {Dynamics of frequency-swept nuclear spin optical pumping in powdered diamond at low magnetic fields}, journal = {Proceedings of the National Academy of Science}, year = {2019}, month = {01/2019}, abstract = {

A broad effort is underway to improve the sensitivity of NMR through the use of dynamic nuclear polarization. Nitrogen vacancy (NV) centers in diamond offer an appealing platform because these paramagnetic defects can be optically polarized efficiently at room temperature. However, work thus far has been mainly limited to single crystals, because most polarization transfer protocols are sensitive to misalignment between the NV and magnetic field axes. Here we study the spin dynamics of NV\−13C pairs in the simultaneous presence of optical excitation and microwave frequency sweeps at low magnetic fields. We show that a subtle interplay between illumination intensity, frequency sweep rate, and hyperfine coupling strength leads to efficient, sweep-direction-dependent 13C spin polarization over a broad range of orientations of the magnetic field. In particular, our results strongly suggest that finely tuned, moderately coupled nuclear spins are key to the hyperpolarization process, which makes this mechanism distinct from other known dynamic polarization channels. These findings pave the route to applications where powders are intrinsically advantageous, including the hyperpolarization of target fluids in contact with the diamond surface or the use of hyperpolarized particles as contrast agents for in vivo imaging.

}, issn = {0027-8424}, doi = { https://doi.org/10.1073/pnas.1811994116 }, url = {https://www.pnas.org/content/early/2019/01/23/1811994116}, author = {P.R. Zangara and S. Dhomkar and A. Ajoy and K. Liu and R. Nazaryan and D. Pagliero and D. Suter and J. Reimer and A. Pines and C. Meriles} } @article {3171, title = {Selective decoupling and Hamiltonian engineering in dipolar spin networks}, journal = {Physics Review Letters}, volume = {122}, year = {2019}, month = {01/2019}, abstract = {

We present a protocol to selectively decouple, recouple, and engineer effective interactions in mesoscopic dipolar spin networks. In particular, we develop a versatile protocol that relies upon magic angle spinning to perform Hamiltonian engineering. By using global control fields in conjunction with a local actuator, such as a diamond nitrogen vacancy center located in the vicinity of a nuclear spin network, both global and local control over the effective couplings can be achieved. We show that the resulting effective Hamiltonian can be well understood within a simple, intuitive geometric picture, and corroborate its validity by performing exact numerical simulations in few-body systems. Applications of our method are in the emerging fields of two-dimensional room temperature quantum simulators in diamond platforms, as well as in molecular magnet systems.

}, doi = {https://doi.org/10.1103/PhysRevLett.122.013205}, url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.013205}, author = {A. Ajoy and U. Bissbort and D. Poletti and P. Cappellaro} } @article {3230, title = {Two-Electron-Spin Ratchets as a Platform for Microwave-Free Dynamic Nuclear Polarization of Arbitrary Material Targets}, journal = {Nano Letters}, year = {2019}, month = {03/2019}, abstract = {

Optically pumped color centers in semiconductor powders can potentially induce high levels of nuclear spin polarization in surrounding solids or fluids at or near ambient conditions, but complications stemming from the random orientation of the particles and the presence of unpolarized paramagnetic defects hinder the flow of polarization beyond the defect\’s host material. Here, we theoretically study the spin dynamics of interacting nitrogen-vacancy (NV) and substitutional nitrogen (P1) centers in diamond to show that outside protons spin-polarize efficiently upon a magnetic field sweep across the NV\–P1 level anticrossing. The process can be interpreted in terms of an NV\–P1 spin ratchet, whose handedness, and hence the sign of the resulting nuclear polarization, depends on the relative timing of the optical excitation pulse. Further, we find that the polarization transfer mechanism is robust to NV misalignment relative to the external magnetic field, and efficient over a broad range of electron\–electron and electron\–nuclear spin couplings, even if proxy spins feature short coherence or spin\–lattice relaxation times. Therefore, these results pave the route toward the dynamic nuclear polarization of arbitrary spin targets brought in proximity with a diamond powder under ambient conditions.

}, doi = {10.1021/acs.nanolett.8b05114}, url = {https://pubs.acs.org/doi/full/10.1021/acs.nanolett.8b05114}, author = {Pablo R. Zangara and J. Henshaw and Daniela Pagliero and Ashok Ajoy and Jeffrey A. Reimer and Alexander Pines and Carlos A. Meriles} } @article {2981, title = {Wide dynamic range magnetic field cycler: Harnessing quantum control at low and high fields}, journal = {Review of Scientific Instruments }, volume = {90}, year = {2019}, month = {01/2019}, abstract = {

We describe the construction of a fast field cycling device capable of sweeping a 4-order-of-magnitude range of magnetic fields, from \∼1 mT to 7 T, in under 700 ms, and which is further extendable to a 1 nT-7 T range. Central to this system is a high-speed sample shuttling mechanism between a superconducting magnet and a magnetic shield, with the capability to access arbitrary fields in between with high resolution. Our instrument serves as a versatile platform to harness the inherent dichotomy of spin dynamics on offer at low and high fields\—in particular, the low anisotropy, fast spin manipulation, and rapid entanglement growth at low field as well as the long spin lifetimes, spin specific control, and efficient inductive measurement possible at high fields. Exploiting these complementary capabilities in a single device opens up applications in a host of problems in quantum control, sensing, and information storage, besides in nuclear hyperpolarization, relaxometry, and imaging. In particular, in this paper, we focus on the ability of the device to enable low-field hyperpolarization of 13C nuclei in diamond via optically pumped electronic spins associated with nitrogen vacancy defect centers.

}, doi = {https://doi.org/10.1063/1.5064685}, url = {https://aip.scitation.org/doi/10.1063/1.5064685}, author = {A. Ajoy and X. Lv and E. Druga and K. Liu and B. Safvati and A. Morabe and M. Fenton and R. Nazaryan and S. Patel and T. Sjolander and J. Reimer and D Sakellariou and C. Meriles and A. Pines} } @article {3193, title = {Zero-Field Nuclear Magnetic Resonance of Chemically Exchanging Systems}, journal = {Nature Communications}, volume = {10}, year = {2019}, month = {07/2019}, abstract = {

Zero- to ultralow-field (ZULF) nuclear magnetic resonance (NMR) is an emerging tool for precision chemical analysis. In this work, we study dynamic processes and investigate the influence of chemical exchange on ZULF NMR J-spectra. We develop a computational approach that allows quantitative calculation of J-spectra in the presence of chemical exchange and apply it to study aqueous solutions of [15N]ammonium (15N) as a model system. We show that pH-dependent chemical exchange substantially affects the J-spectra and, in some cases, can lead to degradation and complete disappearance of the spectral features. To demonstrate potential applications of ZULF NMR for chemistry and biomedicine, we show a ZULF NMR spectrum of [2-13C]pyruvic acid hyperpolarized via dissolution dynamic nuclear polarization (dDNP). We foresee applications of affordable and scalable ZULF NMR coupled with hyperpolarization to study chemical exchange phenomena in vivo and in situations where high-field NMR detection is not possible to implement.

}, doi = {https://doi.org/10.1038/s41467-019-10787-9}, url = {https://www.nature.com/articles/s41467-019-10787-9?fbclid=IwAR1MB5nAamCMGynKRk0sjD6V8rTlZ329IvrVKrCwIO8QjrEH4wD23BV5gak}, author = {Danila Barskiy and Michael Tayler and Irene Marco-Rius and John Kurhanewicz and Daniel Vigneron and Sevil Cikrikci and Ayca Aydogdu and Moritz Reh and Andrey Pravdivtsev and Jan-Bernd H{\"o}vener and John Blanchard and Teng Wu and Dmitry Budker and Alexander Pines} } @article {2980, title = {Enhanced dynamic nuclear polarization via swept microwave frequency combs}, journal = {Proc. Natl. Acad. Sci}, year = {2018}, month = {10/2018}, abstract = {

Dynamic nuclear polarization (DNP) has enabled enormous gains in magnetic resonance signals and led to vastly accelerated NMR/MRI imaging and spectroscopy. Unlike conventional cw-techniques, DNP methods that exploit the full electron spectrum are appealing since they allow direct participation of all electrons in the hyperpolarization process. Such methods typically entail sweeps of microwave radiation over the broad electron linewidth to excite DNP but are often inefficient because the sweeps, constrained by adiabaticity requirements, are slow. In this paper, we develop a technique to overcome the DNP bottlenecks set by the slow sweeps, using a swept microwave frequency comb that increases the effective number of polarization transfer events while respecting adiabaticity constraints. This allows a multiplicative gain in DNP enhancement, scaling with the number of comb frequencies and limited only by the hyperfine-mediated electron linewidth. We demonstrate the technique for the optical hyperpolarization of 13C nuclei in powdered microdiamonds at low fields, increasing the DNP enhancement from 30 to 100 measured with respect to the thermal signal at 7T. For low concentrations of broad linewidth electron radicals [e.g., TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl)], these multiplicative gains could exceed an order of magnitude.

}, doi = {1807125115}, url = {https://doi.org/10.1073/pnas.1807125115}, author = {Ashok Ajoy and Kristina Liu and Xudong Lv and Raffi Nazaryan and G.Wang and E . Druga and Jeff Reimer and Ditter Suter and C. Ramanathan and C.A Meriles and Alexander Pines} } @article {2581, title = {Optically-pumped dynamic nuclear hyperpolarization in 13C enriched diamond}, journal = {Phys. Rev. B Rapid Communications}, year = {2018}, abstract = {

We investigate nuclear spin hyperpolarization from optically polarized nitrogen vacancy centers in isotopically enriched diamonds with 13C concentrations up to 100\%.\ 13C enrichment leads to hyperfine structure of the nitrogen vacancy electron spin resonance spectrum and dynamic nuclear polarization enhancement profile. We show that strongly-coupled \cthirt spins in the first shell surrounding a nitrogen vacancy center generate resolved hyperfine splittings, but do not act as an intermediary in the transfer of hyperpolarization of bulk nuclear spins. High levels of \cthirt enrichment are desirable to increase the efficiency of hyperpolarization for magnetic resonance signal enhancement, imaging contrast agents, and as a platform for quantum sensing and many-body physics.

}, url = {https://journals.aps.org/prb/accepted/0707cOeaT9fE2916845f0be02a174d447e77534ff}, author = {Parker, AJ and Jeong, K and Avalos, CE and Hausmann, BJM and Vassiliou, CC and Pines, A and King, JP} } @article {2979, title = {Orientation independent room-temperature optical 13C hyperpolarization in powdered diamond}, journal = {Science Advances}, volume = {4}, year = {2018}, month = {05/2018}, abstract = {

Dynamic nuclear polarization via contact with electronic spins has emerged as an attractive route to enhance the sensitivity of nuclear magnetic resonance beyond the traditional limits imposed by magnetic field strength and temperature. Among the various alternative implementations, the use of nitrogen vacancy (NV) centers in diamond\—a paramagnetic point defect whose spin can be optically polarized at room temperature\—has attracted widespread attention, but applications have been hampered by the need to align the NV axis with the external magnetic field. We overcome this hurdle through the combined use of continuous optical illumination and a microwave sweep over a broad frequency range. As a proof of principle, we demonstrate our approach using powdered diamond with which we attain bulk 13C spin polarization in excess of 0.25\% under ambient conditions. Remarkably, our technique acts efficiently on diamond crystals of all orientations and polarizes nuclear spins with a sign that depends exclusively on the direction of the microwave sweep. Our work paves the way toward the use of hyperpolarized diamond particles as imaging contrast agents for biosensing and, ultimately, for the hyperpolarization
of nuclear spins in arbitrary liquids brought in contact with their surface.

}, doi = {10.1126/sciadv.aar5492 }, url = {http://advances.sciencemag.org/content/4/5/eaar5492}, author = {Ashok Ajoy and Kristina Liu and Raff Nazaryan and Xudong Lv and Pablo R. Zangara and Benjamin Safvati and Guoqing Wang and Daniel Arnold and Grace Li and Arthur Lin and Priyanka Raghavan and Emanuel Druga and Siddharth Dhomkar and Daniela Pagliero and Jeffrey A. Reimer and Dieter Suter and Carlos A. Meriles and Alexander Pines} } @article {1875, title = {Room temperature in situ nuclear spin hyperpolarization from optically pumped nitrogen vacancy centers in diamond}, journal = {Nature Communications}, year = {2015}, author = {Jonathan P. King and Keunhong Jeong and Christophoros C. Vassiliou and Chang S. Shin and Ralph H. Page and Claudia E. Avalos and Hai-Jing Wang and Alexander Pines} } @article {1476, title = {Optically detected cross-relaxation spectroscopy of electron spins in diamonds}, journal = {Nature Communication}, volume = {5}, year = {2014}, month = {06/2014}, pages = {4135}, doi = {10.1038/ncomms5135}, author = {Wang, H. J. and Shin, C. S. and Seltzer, S. J. and Avalos, C. E. and Pines, A. and Bajaj, V. S.} } @article {1477, title = {Optically-detected nuclear quadrupolar interaction of 14N in nitrogen-vacancy centers in diamond}, journal = {Physical Review B}, volume = {89}, year = {2014}, pages = {205202}, doi = {10.1103/PhysRevB.89.205202}, author = {Shin, C. S. and Butler, M. C. and Wang, H. J. and Avalos, C. E. and Seltzer, S. J. and Liu, R. and Pines, A. and Bajaj, V.S.} } @article {245, title = {Fundamental Aspects of Parahydrogen Enhanced Low-Field Nuclear Magnetic Resonance}, journal = {Physical Review Letters}, volume = {110}, year = {2013}, note = {Phys Rev Lett113RITimes Cited:0Cited References Count:28}, month = {Mar 26}, pages = {137602}, abstract = {

We report new phenomena in low-field H-1 nuclear magnetic resonance (NMR) spectroscopy using parahydrogen induced polarization (PHIP), enabling determination of chemical shift differences, delta nu, and the scalar coupling constant J. NMR experiments performed with thermal polarization in millitesla magnetic fields do not allow the determination of scalar coupling constants for homonuclear coupled spins in the inverse weak coupling regime (delta nu \< J). We show here that low-field PHIP experiments in the inverse weak coupling regime enable the precise determination of delta nu and J. Furthermore we experimentally prove that observed splittings are related to delta nu in a nonlinear way. Naturally abundant C-13 and Si-29 isotopes lead to heteronuclear J-coupled H-1-multiplet lines with amplitudes significantly enhanced compared to the amplitudes for thermally prepolarized spins. PHIP-enhanced NMR in the millitesla regime allows us to measure characteristic NMR parameters in a single scan using samples containing rare spins in natural abundance. DOI: 10.1103/PhysRevLett.110.137602

}, keywords = {exchange}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.110.137602}, url = {://WOS:000316685100032}, author = {Colell, J. and Turschmann, P. and Gloggler, S. and Schleker, P. and Theis, T. and Ledbetter, M. and Budker, D. and Pines, A. and Blumich, B. and Appelt, S.} } @article {1074, title = {Sensitive magnetic control of ensemble nuclear spin hyperpolarization in diamond}, journal = {Nature Communications}, volume = {4}, year = {2013}, note = {Nature communicationsWang, Hai-JingShin, Chang SAvalos, Claudia ESeltzer, Scott JBudker, DmitryPines, AlexanderBajaj, Vikram SengEngland2013/06/06 06:00Nat Commun. 2013 Jun 5;4:1940. doi: 10.1038/ncomms2930.}, month = {June 5, 2013}, pages = {1940}, chapter = {1940}, abstract = {

Dynamic nuclear polarization, which transfers the spin polarization of electrons to nuclei, is routinely applied to enhance the sensitivity of nuclear magnetic resonance. This method is particularly useful when spin hyperpolarization can be produced and controlled optically or electrically. Here we show complete polarization of nuclei located near optically polarized nitrogen-vacancy centres in diamond. Close to the ground-state level anti-crossing condition of the nitrogen-vacancy electron spins, (13)C nuclei in the first shell are polarized in a pattern that depends sensitively upon the magnetic field. Based on the anisotropy of the hyperfine coupling and of the optical polarization mechanism, we predict and observe a reversal of the nuclear spin polarization with only a few millitesla change in the magnetic field. This method of magnetic control of high nuclear polarization at room temperature can be applied in sensitivity enhanced nuclear magnetic resonance of bulk nuclei, nuclear-based spintronics, and quantum computation in diamond.

}, isbn = {2041-1723 (Linking)}, doi = {10.1038/ncomms2930}, url = {http://www.ncbi.nlm.nih.gov/pubmed/23736952}, author = {Wang, H. J. and Shin, C. S. and Avalos, C. E. and Seltzer, S. J. and Budker, D. and Pines, A. and Bajaj, V. S.} } @article {1318, title = {Suppression of electron spin decoherence of the diamond NV center by a transverse magnetic field}, journal = {Physical Review B}, volume = {88}, year = {2013}, month = {10/2013}, abstract = {

We demonstrate that the spin decoherence of nitrogen vacancy (NV) centers in diamond can be suppressed by a transverse magnetic field if the electron spin bath is the primary decoherence source. The NV spin coherence, created in \“a decoherence-free subspace,\” is protected by the transverse component of the zero-field splitting, increasing the spin-coherence time about twofold. The decoherence due to the electron spin bath is also suppressed at magnetic fields stronger than \∼25 G when applied parallel to the NV symmetry axis. Our method can be used to extend the spin-coherence time of similar spin systems for applications in quantum computing, field sensing, and other metrologies.

}, doi = {10.1103/PhysRevB.88.161412}, url = {http://prb.aps.org/abstract/PRB/v88/i16/e161412}, author = {Shin, Chang S. and Avalos, Claudia E. and Butler, Mark C. and Wang, Hai-Jing and Seltzer, Scott J. and Liu, Ren-Bao and Pines, Alexander and Bajaj, Vikram S.} } @article {249, title = {Room-temperature operation of a radiofrequency diamond magnetometer near the shot-noise limit}, journal = {Journal of Applied Physics}, volume = {112}, year = {2012}, note = {J Appl Phys061ECTimes Cited:1Cited References Count:15}, month = {Dec 15, 2012}, pages = {124519}, chapter = {124519}, abstract = {

We operate a nitrogen-vacancy (NV-) diamond magnetometer at ambient temperatures and study the dependence of its bandwidth on experimental parameters including optical and microwave excitation powers. A model based on the Bloch equations is used to analyze the NV center\&$\#$39;s response time, tau, during continuous optical and microwave irradiation, and tau(-1) is shown to be a weighted average of T-1(-1) and T-2(-1), where T-1 and T-2 are the longitudinal and transverse relaxation times of the electron spin during optical irradiation. We measured a maximum detection bandwidth of similar to 1.6 MHz with optical excitation intensity of similar to 2.3MW/cm(2), limited by the available optical power. The sensitivity of the NV ensemble for continuous-wave magnetometry in the presence of photon shot noise is analyzed. Two detection schemes are compared, one involving modulation of the fluorescence by an oscillating magnetic field while the microwave frequency is held constant, and the other involving double modulation of the fluorescence when the microwave frequency is modulated during the detection. For the first of these methods, we measure a sensitivity of 4.6 +/- 0.3 nT/root Hz, unprecedented in a detector with this active volume of similar to 10 mu m(3) and close to the photon-shot-noise limit of our experiment. The measured bandwidth and sensitivity of our device should allow detection of micro-scale NMR signals with microfluidic devices. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4771924]

}, keywords = {spin}, isbn = {0021-8979}, doi = {Doi 10.1063/1.4771924}, url = {http://link.aip.org/link/doi/10.1063/1.4771924}, author = {Shin, C. S. and Avalos, C. E. and Butler, M. C. and Trease, D. R. and Seltzer, S. J. and Mustonen, J. P. and Kennedy, D. J. and Acosta, V. M. and Budker, D. and Pines, A. and Bajaj, V. S.} } @article {258, title = {Near-Zero-Field Nuclear Magnetic Resonance}, journal = {Physical Review Letters}, volume = {107}, year = {2011}, note = {Phys Rev Lett813YOTimes Cited:5Cited References Count:26}, month = {Sep 1}, abstract = {

We investigate nuclear magnetic resonance (NMR) in near zero field, where the Zeeman interaction can be treated as a perturbation to the electron mediated scalar interaction (J coupling). This is in stark contrast to the high-field case, where heteronuclear J couplings are normally treated as a small perturbation. We show that the presence of very small magnetic fields results in splitting of the zero-field NMR lines, imparting considerable additional information to the pure zero-field spectra. Experimental results are in good agreement with first-order perturbation theory and with full numerical simulation when perturbation theory breaks down. We present simple rules for understanding the splitting patterns in near-zero-field NMR, which can be applied to molecules with nontrivial spectra.

}, keywords = {mri}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.107.107601}, url = {://WOS:000294406600017}, author = {Ledbetter, M. P. and Theis, T. and Blanchard, J. W. and Ring, H. and Ganssle, P. and Appelt, S. and Blumich, B. and Pines, A. and Budker, D.} } @article {272, title = {Picomolar sensitivity MRI and photoacoustic imaging of cobalt nanoparticles}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {106}, year = {2009}, note = {P Natl Acad Sci USA420HDTimes Cited:43Cited References Count:41}, month = {Mar 17}, pages = {4085-4089}, abstract = {

Multimodality imaging based on complementary detection principles has broad clinical applications and promises to improve the accuracy of medical diagnosis. This means that a tracer particle advantageously incorporates multiple functionalities into a single delivery vehicle. In the present work, we explore a unique combination of MRI and photoacoustic tomography (PAT) to detect picomolar concentrations of nanoparticles. The nanoconstruct consists of ferromagnetic (Co) particles coated with gold (Au) for biocompatibility and a unique shape that enables optical absorption over a broad range of frequencies. The end result is a dual-modality probe useful for the detection of trace amounts of nanoparticles in biological tissues, in which MRI provides volume detection, whereas PAT performs edge detection.

}, keywords = {cancer}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.0813019106}, url = {://WOS:000264278800008}, author = {Bouchard, L. S. and Anwar, M. S. and Liu, G. L. and Hann, B. and Xie, Z. H. and Gray, J. W. and Wang, X. D. and Pines, A. and Chen, F. F.} } @article {282, title = {NMR imaging of catalytic hydrogenation in microreactors with the use of para-hydrogen}, journal = {Science}, volume = {319}, year = {2008}, note = {Science254HBTimes Cited:55Cited References Count:33}, month = {Jan 25}, pages = {442-445}, abstract = {

Catalysis is vital to industrial chemistry, and the optimization of catalytic reactors attracts considerable resources. It has proven challenging to correlate the active regions in heterogeneous catalyst beds with morphology and to monitor multistep reactions within the bed. We demonstrate techniques, using magnetic resonance imaging and para- hydrogen ( p-H(2)) polarization, that allow direct visualization of gas- phase flow and the density of active catalyst in a packed- bed microreactor, as well as control over the dynamics of the polarized state in space and time to facilitate the study of subsequent reactions. These procedures are suitable for characterizing reactors and reactions in microfluidic devices where low sensitivity of conventional magnetic resonance would otherwise be the limiting factor.

}, keywords = {chip}, isbn = {0036-8075}, doi = {Doi 10.1126/Science.1151787}, url = {://WOS:000252576600031}, author = {Bouchard, L. S. and Burt, S. R. and Anwar, M. S. and Kovtunov, K. V. and Koptyug, I. V. and Pines, A.} } @article {275, title = {Remote detection of nuclear magnetic resonance with an anisotropic magnetoresistive sensor}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {105}, year = {2008}, note = {P Natl Acad Sci USA266XBTimes Cited:8Cited References Count:17}, month = {Feb 19}, pages = {2271-2273}, abstract = {

We report the detection of nuclear magnetic resonance (NMR) using an anisotropic magnetoresistive (AMR) sensor. A \"remote-detection\" arrangement was used in which protons in flowing water were prepolarized in the field of a superconducting NMR magnet, adiabatically inverted, and subsequently detected with an AMR sensor situated downstream from the magnet and the adiabatic inverter. AMR sensing is well suited for NMR detection in microfluidic \"lab-on-a-chip\" applications because the sensors are small, typically on the order of 10 mu m. An estimate of the sensitivity for an optimized system indicates that approximate to 6 x 10(13) protons in a volume of 1,000 mu m(3), prepolarized in a 10-kG magnetic field, can be detected with a signal-to-noise ratio of 3 in a 1-Hz bandwidth. This level of sensitivity is competitive with that demonstrated by microcoils in superconducting magnets and with the projected sensitivity of microfabricated atomic magnetometers.

}, keywords = {mri}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.0712129105}, url = {://WOS:000253469900006}, author = {Verpillat, F. and Ledbetter, M. P. and Xu, S. and Michalak, D. J. and Hilty, C. and Bouchard, L. S. and Antonijevic, S. and Budker, D. and Pines, A.} } @article {290, title = {Para-hydrogen-enhanced hyperpolarized gas-phase magnetic resonance imaging}, journal = {Angewandte Chemie-International Edition}, volume = {46}, year = {2007}, note = {Angew Chem Int Edit174ZPTimes Cited:28Cited References Count:37}, pages = {4064-4068}, keywords = {he-3}, isbn = {1433-7851}, doi = {Doi 10.1002/Anie.200700830}, url = {://WOS:000246981900008}, author = {Bouchard, L. S. and Kovtunov, K. V. and Burt, S. R. and Anwar, M. S. and Koptyug, I. V. and Sagdeev, R. Z. and Pines, A.} } @article {285, title = {Para-hydrogen-induced polarization in heterogeneous hydrogenation reactions}, journal = {Journal of the American Chemical Society}, volume = {129}, year = {2007}, note = {J Am Chem Soc160MRTimes Cited:36Cited References Count:45}, month = {May 2}, pages = {5580-5586}, abstract = {

We demonstrate the creation and observation of para-hydrogen-induced polarization in heterogeneous hydrogenation reactions. Wilkinson\&$\#$39;s catalyst, RhCl(PPh3)(3), supported on either modified silica gel or a polymer, is shown to hydrogenate styrene into ethylbenzene and to produce enhanced spin polarizations, observed through NMR, when the reaction was performed with H-2 gas enriched in the para spin isomer. Furthermore, gaseous phase para-hydrogenation of propylene to propane with two catalysts, the Wilkinson\&$\#$39;s catalyst supported on modified silica gel and Rh(cod)(sulfos) (cod = cycloocta-1,5-diene; sulfos = -O3S(C6H4)CH2C(CH2PPh2)(3)) supported on silica gel, demonstrates heterogeneous catalytic conversion resulting in large spin polarizations. These experiments serve as a direct verification of the mechanism of heterogeneous hydrogenation reactions involving immobilized metal complexes and can be potentially developed into a practical tool for producing catalyst-free fluids with highly polarized nuclear spins for a broad range of hyperpolarized NMR and MRI applications.

}, keywords = {alignment}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja068653o}, url = {://WOS:000245946400064}, author = {Koptyug, I. V. and Kovtunov, K. V. and Burt, S. R. and Anwar, M. S. and Hilty, C. and Han, S. I. and Pines, A. and Sagdeev, R. Z.} } @article {291, title = {Spin coherence transfer in chemical transformations monitored by remote detection NMR}, journal = {Analytical Chemistry}, volume = {79}, year = {2007}, note = {Anal Chem151QATimes Cited:7Cited References Count:39}, month = {Apr 1}, pages = {2806-2811}, abstract = {

We demonstrate a nuclear magnetic resonance (NMR) experiment using continuous flow in a microfluidic channel for studying the transfer of spin coherence in nonequilibrium chemical processes. We use the principle of remote detection, which involves spatially separated NMR encoding and detection coils. As an example, we provide the map of chemical shift correlations for the amino acid alanine as it transitions from the zwitterionic to the anionic form. The presented method uniquely allows for tracking the migration of encoded spins during the course of any chemical transformation and can provide useful information about reaction mechanisms.

}, keywords = {lab}, isbn = {0003-2700}, doi = {Doi 10.1021/Ac062327+}, url = {://WOS:000245304300022}, author = {Anwar, M. S. and Hilty, C. and Chu, C. and Bouchard, L. S. and Pierce, K. L. and Pines, A.} } @article {334, title = {Isotropic-liquid crystalline phase diagram of a CdSe nanorod solution}, journal = {Journal of Chemical Physics}, volume = {120}, year = {2004}, note = {J Chem Phys763JETimes Cited:27Cited References Count:29}, month = {Jan 15}, pages = {1149-1152}, abstract = {

We report the isotropic-liquid crystalline phase diagram of 3.0 nm x 60 nm CdSe nanorods dispersed in anhydrous cyclohexane. The coexistence concentrations of both phases are found to be lower and the biphasic region wider than the results predicted by the hard rod model, indicating that the attractive interaction between the nanorods may be important in the formation of the liquid crystalline phase in this system. (C) 2004 American Institute of Physics.

}, keywords = {model}, isbn = {0021-9606}, doi = {Doi 10.1063/1.1640331}, url = {://WOS:000188081000002}, author = {Li, L. S. and Marjanska, M. and Park, G. H. J. and Pines, A. and Alivisatos, A. P.} } @article {379, title = {NMR study of InP quantum dots: Surface structure and size effects}, journal = {Journal of Chemical Physics}, volume = {110}, year = {1999}, note = {J Chem Phys192HUTimes Cited:30Cited References Count:28}, month = {May 8}, pages = {8861-8864}, abstract = {

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].

}, keywords = {clusters}, isbn = {0021-9606}, doi = {Doi 10.1063/1.478858}, url = {://WOS:000080073200002}, author = {Tomaselli, M. and Yarger, J. L. and Bruchez, M. and Havlin, R. H. and deGraw, D. and Pines, A. and Alivisatos, A. P.} } @article {402, title = {A high-resolution(17)O NMR study of siliceous zeolite faujasite}, journal = {Journal of the American Chemical Society}, volume = {120}, year = {1998}, note = {J Am Chem SocZj097Times Cited:66Cited References Count:19}, month = {Apr 15}, pages = {3510-3511}, keywords = {workstation computers}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja9743001}, url = {://WOS:000073179200032}, author = {Bull, L. M. and Cheetham, A. K. and Anupold, T. and Reinhold, A. and Samoson, A. and Sauer, J. and Bussemer, B. and Lee, Y. and Gann, S. and Shore, J. and Pines, A. and Dupree, R.} } @article {405, title = {Low field magnetic resonance images of polarized noble gases obtained with a dc superconducting quantum interference device}, journal = {Applied Physics Letters}, volume = {72}, year = {1998}, note = {Appl Phys LettZg930Times Cited:37Cited References Count:24}, month = {Apr 13}, pages = {1908-1910}, abstract = {

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.

}, keywords = {mri}, isbn = {0003-6951}, doi = {Doi 10.1063/1.121223}, url = {://WOS:000073054300038}, author = {Augustine, M. P. and Wong-Foy, A. and Yarger, J. L. and Tomaselli, M. and Pines, A. and TonThat, D. M. and Clarke, J.} } @article {391, title = {Scalar and anisotropic J interactions in undoped InP: A triple-resonance NMR study}, journal = {Physical Review B}, volume = {58}, year = {1998}, note = {Phys Rev B125HUTimes Cited:29Cited References Count:40}, month = {Oct 1}, pages = {8627-8633}, abstract = {

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.

}, keywords = {solids}, isbn = {0163-1829}, doi = {Doi 10.1103/Physrevb.58.8627}, url = {://WOS:000076232100075}, author = {Tomaselli, M. and deGraw, D. and Yarger, J. L. and Augustine, M. P. and Pines, A.} } @article {411, title = {Enhancement of surface NMR by laser-polarized noble gases}, journal = {Physical Review B}, volume = {55}, year = {1997}, note = {Phys Rev BWy504Times Cited:65Cited References Count:34}, month = {May 1}, pages = {11604-11610}, abstract = {

The transfer of spin polarization from laser-polarized helium and xenon to spins such as H-1 and C-13 On the surface of high-surface-area solids (Aerosil) is demonstrated over a temperature range from 4 to 200 K. The transfer mechanism is dipole-dipole cross relaxation between the spins of the adsorbed mobile noble gas and the surface spins (spin-polarization-induced nuclear Overhauser effect). The enhancement of surface proton magnetization by laser-polarized helium at 4 K and 10 K is between one and twofold. Using laser-polarized xenon, enhancement factors of up to 20 were obtained when compared to the Boltzmann polarization in a field of 4.2 T and at a temperature of 130 K.

}, keywords = {he-3}, isbn = {0163-1829}, doi = {Doi 10.1103/Physrevb.55.11604}, url = {://WOS:A1997WY50400096}, author = {Room, T. and Appelt, S. and Seydoux, R. and Hahn, E. L. and Pines, A.} } @article {408, title = {Low magnetic field dynamic nuclear polarization using a single-coil two-channel probe}, journal = {Review of Scientific Instruments}, volume = {68}, year = {1997}, note = {Rev Sci InstrumWp247Times Cited:4Cited References Count:29}, month = {Mar}, pages = {1527-1531}, abstract = {

We describe the design and construction of a single-coil, two-channel probe for the detection of low-field magnetic resonance using dynamic nuclear polarization (DNP). The high-frequency channel of the probe, which is used to saturate the electron spins, is tuned to the electron Larmor frequency, 75 MHz at 2.7 mT, and matched to 50 Omega. Low-field, H-1 nuclear magnetic resonance (NMR) is detected through the second, low-frequency channel at frequencies \<1 MHz. The performance of the probe was tested by measuring the DNP of protons in a manganese (II) chloride solution at 2.7 mT. At the proton NMR frequency of 120 kHz, the signal amplitude was enhanced over the value without DNP by a factor of about 200. (C) 1997 American Institute of Physics.

}, keywords = {nmr}, isbn = {0034-6748}, doi = {Doi 10.1063/1.1147641}, url = {://WOS:A1997WP24700033}, author = {TonThat, D. M. and Augustine, M. P. and Pines, A. and Clarke, J.} } @article {407, title = {SQUID detected NMR of laser-polarized xenon at 4.2 K and at frequencies down to 200 Hz}, journal = {Chemical Physics Letters}, volume = {272}, year = {1997}, note = {Chem Phys LettXh440Times Cited:18Cited References Count:32}, month = {Jun 27}, pages = {245-249}, abstract = {

A spectrometer based on a dc SQUID (superconducting quantum interference device) was used to record nuclear magnetic resonance signals from laser-polarized Xe-129 at 4.2 K and at frequencies ranging from about 200 Hz to 110 kHz in magnetic fields varying from about 0.02 to 9 mT. The Xe-129 resonance linewidths were found to increase with increasing magnetic field, and, at a given field, to increase with higher Xe-129 concentration. The spin-lattice relaxation times were observed to decrease from similar to 8000 s at 5 mT to similar to 2000 s at fields below 0.05 mT. Such long relaxation times make possible a variety of spin polarization transfer experiments. (C) 1997 Published by Elsevier Science B.V.

}, keywords = {relaxation}, isbn = {0009-2614}, doi = {Doi 10.1016/S0009-2614(97)88016-5}, url = {://WOS:A1997XH44000017}, author = {TonThat, D. M. and Ziegeweid, M. and Song, Y. Q. and Munson, E. J. and Appelt, S. and Pines, A. and Clarke, J.} } @article {426, title = {Enhancement of solution NMR and MRI with laser-polarized xenon}, journal = {Science}, volume = {271}, year = {1996}, note = {ScienceUc778Times Cited:230Cited References Count:41}, month = {Mar 29}, pages = {1848-1851}, abstract = {

Optical pumping with laser light can be used to polarize the nuclear spins of gaseous xenon-129. When hyperpolarized xenon-129 is dissolved in liquids, a time-dependent departure of the proton spin polarization from its thermal equilibrium is observed, The variation of the magnetization is an unexpected manifestation of the nuclear Overhauser effect, a consequence of cross-relaxation between the spins of solution protons and dissolved xenon-129. Time-resolved magnetic resonance images of both nuclei in solution show that the proton magnetization is selectively perturbed in regions containing spin-polarized xenon-129. This effect could find use in nuclear magnetic resonance spectroscopy of surfaces and proteins and in magnetic resonance imaging.

}, keywords = {resonance}, isbn = {0036-8075}, doi = {Doi 10.1126/Science.271.5257.1848}, url = {://WOS:A1996UC77800041}, author = {Navon, G. and Song, Y. Q. and Room, T. and Appelt, S. and Taylor, R. E. and Pines, A.} } @article {425, title = {Si-29 high resolution solid state nuclear magnetic resonance spectroscopy of porous silicon}, journal = {Journal of Non-Crystalline Solids}, volume = {202}, year = {1996}, note = {J Non-Cryst SolidsVe406Times Cited:13Cited References Count:33}, month = {Jul}, pages = {68-76}, abstract = {

Porous silicon has been characterized by Si-29 nuclear magnetic resonance spectroscopy under conditions of static samples, magic angle spinning, decoupling and cross polarization. In a free induction decay experiment, two Si-29 resonances at -80 and -111 ppm were obtained. Cross polarization resulted in a single resonance at -97 ppm. Magic angle spinning and decoupling slightly reduce the linewidth of the Si-29 cross polarized signal, The minor narrowing effect and thr relaxation behavior in the laboratory and rotating frame indicate a homogeneous contribution to the linewidth. The relaxation data suggest that the resonance observed under cross polarization conditions arises from SiH or SiH2 structural elements.

}, keywords = {dipolar}, isbn = {0022-3093}, doi = {Doi 10.1016/0022-3093(96)00144-5}, url = {://WOS:A1996VE40600008}, author = {Pietrass, T. and Bifone, A. and Roth, R. D. and Koch, V. P. and Alivisatos, A. P. and Pines, A.} } @article {439, title = {Spin-Polarized Xe-129 Gas Imaging of Materials}, journal = {Journal of Magnetic Resonance Series A}, volume = {115}, year = {1995}, note = {J Magn Reson Ser ARl474Times Cited:49Cited References Count:23}, month = {Jul}, pages = {127-130}, keywords = {xenon}, isbn = {1064-1858}, doi = {Doi 10.1006/Jmra.1995.1157}, url = {://WOS:A1995RL47400017}, author = {Song, Y. Q. and Gaede, H. C. and Pietrass, T. and Barrall, G. A. and Chingas, G. C. and Ayers, M. R. and Pines, A.} } @article {438, title = {Xe-129 Nmr-Studies of Hyper-Cross-Linked Polyarylcarbinols - Rigid Versus Flexible Structures}, journal = {Chemistry of Materials}, volume = {7}, year = {1995}, note = {Chem MaterRk993Times Cited:27Cited References Count:30}, month = {Jul}, pages = {1325-1332}, abstract = {

Xenon NMR is used with adsorption measurements to infer information about the microstructure of some novel hyper-cross-linked polyarylcarbinols. It is shown that rigidrod connecting units are necessary for microporosity in these systems, as hyper-cross-linked polymers based on flexible structures are found to have conventional surface areas and xenon NMR spectra. A microporous polymer based on rigid triarylcarbinol monomers shows high xenon uptake and a linear chemical shift variation with pressure at room temperature. Spin-lattice relaxation and cross-polarization dynamics are studied at low temperatures. In this regime the xenon has extremely long equilibration times, and the adsorption dynamics are complicated but give important insight into the polymer topology. The data are compared with two possible models of the polymer microstructwre.

}, keywords = {adsorption}, isbn = {0897-4756}, doi = {Doi 10.1021/Cm00055a008}, url = {://WOS:A1995RK99300008}, author = {Urban, C. and Mccord, E. F. and Webster, O. W. and Abrams, L. and Long, H. W. and Gaede, H. and Tang, P. and Pines, A.} } @article {467, title = {Probing Cds Nanocrystal Surfaces with Laser-Polarized Xenon}, journal = {Journal of Physical Chemistry}, volume = {98}, year = {1994}, note = {J Phys Chem-UsPh559Times Cited:32Cited References Count:29}, month = {Sep 22}, pages = {9400-9404}, abstract = {

This paper describes the application of optically pumped xenon NMR to probe the surface of semiconductor nanocrystals by physisorption at 123 K. These experiments were made possible by using highly spin ordered Xe-129, prepared by optical pumping and spin exchange of a rubidium xenon gas mixture, to increase the NMR signal strength. CdS nanocrystals were prepared by regulated growth in inverse micelles and precipitated by surface derivatization with thiophenol. Nanocrystals of 11.8, 12.8, and 23 Angstrom radii with 26\%, 63\%, and 57\% thiophenol surface coverage, respectively, were characterized. Within this sample parameter space, the Xe-129 spectra, recorded at varying xenon coverages, depended strongly on thiophenol surface coverage but were not sensitive to the crystallite size. In addition, the nanocrystals with low thiophenol coverage yielded a xenon line shape consisting of two components, interpreted as xenon signals arising from distinct surface domains. These domains are presumably formed by the aggregation of thiophenol molecules on the nanocrystal surface when the thiophenol coverage is incomplete, a model which is consistent with existing X-ray photoelectron spectroscopy and liquid state H-1 NMR data.

}, keywords = {resonance}, isbn = {0022-3654}, doi = {Doi 10.1021/J100089a008}, url = {://WOS:A1994PH55900008}, author = {Bowers, C. R. and Pietrass, T. and Barash, E. and Pines, A. and Grubbs, R. K. and Alivisatos, A. P.} } @proceedings {460, title = {Yakir Aharonov: From A to B}, journal = {Proc. of the Int. Conf. on Fundamental Aspects of Quantum Theory}, year = {1994}, publisher = {World Scientific}, author = {Pines, A.}, editor = {Anandan, J. and Safko, J.} } @article {487, title = {Nmr-Studies of the Surface-Structure and Dynamics of Semiconductor Nanocrystals}, journal = {Chemical Physics Letters}, volume = {198}, year = {1992}, note = {Chem Phys LettJt385Times Cited:77Cited References Count:27}, month = {Oct 16}, pages = {431-436}, abstract = {

H-1 NMR studies of thiophenol capping groups on cadmium sulfide nanocrystals demonstrate that the coverage of the capping molecule depends on the size of the nanocrystal. Data are presented which show that as the size of the nanocrystal increases, the coverage of thiophenol decreases. In addition, information about the overall tumbling of the nanocrystal and the motion of the capping groups relative to the surface can be obtained from linewidth studies, indicating that the rotation of the capping groups is hindered in the smaller nanocrystals (r almost-equal-to 12 angstrom) and becomes less so in larger nanocrystals (r almost-equal-to 20 angstrom). The coverage data are related to the electronic properties of this important class of compounds.

}, keywords = {relaxation}, isbn = {0009-2614}, doi = {Doi 10.1016/0009-2614(92)80023-5}, url = {://WOS:A1992JT38500001}, author = {Sachleben, J. R. and Wooten, E. W. and Emsley, L. and Pines, A. and Colvin, V. L. and Alivisatos, A. P.} } @proceedings {519, title = {Abelian and non-abelian holonomy in NMR interferometry}, journal = {Proc. of the Conference on Fundamental Aspects of Quantum Theory}, year = {1990}, publisher = {World Scientific Press}, author = {Pines, A. and Meuller, K.T.}, editor = {Anandan, J.} } @article {557, title = {Non-Abelian Geometric Phase from Incomplete Quantum Measurements}, journal = {Physics Letters A}, volume = {141}, year = {1989}, note = {Phys Lett ACb816Times Cited:19Cited References Count:16}, month = {Nov 13}, pages = {335-339}, isbn = {0375-9601}, doi = {Doi 10.1016/0375-9601(89)90060-1}, url = {://WOS:A1989CB81600005}, author = {Anandan, J. and Pines, A.} } @article {670, title = {Deuterium Nmr in Solids with a Cylindrical Magic Angle Sample Spinner}, journal = {Journal of Magnetic Resonance}, volume = {41}, year = {1980}, note = {J Magn ResonKx294Times Cited:41Cited References Count:10}, pages = {440-446}, isbn = {1090-7807}, doi = {Doi 10.1016/0022-2364(80)90301-7}, url = {://WOS:A1980KX29400011}, author = {Eckman, R. and Alla, M. and Pines, A.} } @article {671, title = {Spin Diffusion and Spin-Lattice Relaxation of Deuterium in Rotating Solids}, journal = {Chemical Physics Letters}, volume = {71}, year = {1980}, note = {Chem Phys LettJq737Times Cited:39Cited References Count:7}, pages = {148-151}, isbn = {0009-2614}, doi = {Doi 10.1016/0009-2614(80)85309-7}, url = {://WOS:A1980JQ73700031}, author = {Alla, M. and Eckman, R. and Pines, A.} } @article {675, title = {Experimental Results on Deuterium Nmr in the Solid-State by Magic Angle Sample Spinning}, journal = {Chemical Physics}, volume = {42}, year = {1979}, note = {Chem PhysHl541Times Cited:50Cited References Count:15}, pages = {423-428}, isbn = {0301-0104}, doi = {Doi 10.1016/0301-0104(79)80092-0}, url = {://WOS:A1979HL54100022}, author = {Ackerman, J. L. and Eckman, R. and Pines, A.} } @article {700, title = {Chemical Shielding Tensors of C-13 in Solid Dimethyl Oxalate}, journal = {Journal of Chemical Physics}, volume = {60}, year = {1974}, note = {J Chem PhysT5858Times Cited:29Cited References Count:9}, pages = {5130-5131}, isbn = {0021-9606}, doi = {Doi 10.1063/1.1681041}, url = {://WOS:A1974T585800081}, author = {Pines, A. and Abramson, E.} } @article {694, title = {Molecular Ordering and Even-Odd Effect in a Homologous Series of Nematic Liquid-Crystals}, journal = {Physical Review Letters}, volume = {33}, year = {1974}, note = {Phys Rev LettU3736Times Cited:72Cited References Count:26}, pages = {1002-1005}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.33.1002}, url = {://WOS:A1974U373600004}, author = {Pines, A. and Ruben, D. J. and Allison, S.} }