Person: Glenn, David
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Glenn, David
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Publication Efficiency of Cathodoluminescence Emission by Nitrogen-Vacancy Color Centers in Nanodiamonds(Wiley, 2017-04-18) Zhang, Huiliang; Glenn, David; Schalek, Richard; Lichtman, Jeff; Walsworth, RonaldCorrelated electron microscopy and cathodoluminescence (CL) imaging using functionalized nanoparticles is a promising nanoscale probe of biological structure and function. Nanodiamonds (NDs) that contain CL‐emitting color centers are particularly well suited for such applications. The intensity of CL emission from NDs is determined by a combination of factors, including particle size, density of color centers, efficiency of energy deposition by electrons passing through the particle, and conversion efficiency from deposited energy to CL emission. This paper reports experiments and numerical simulations that investigate the relative importance of each of these factors in determining CL emission intensity from NDs containing nitrogen‐vacancy (NV) color centers. In particular, it is found that CL can be detected from NV‐doped NDs with dimensions as small as ≈40 nm, although CL emission decreases significantly for smaller NDs.Publication Optical magnetic detection of single-neuron action potentials using quantum defects in diamond(Proceedings of the National Academy of Sciences, 2016) Barry, John; Turner, Matthew; Schloss, Jennifer M.; Glenn, David; Song, Yuyu; Lukin, Mikhail; Park, Hongkun; Walsworth, RonaldMagnetic fields from neuronal action potentials (APs) pass largely unperturbed through biological tissue, allowing magnetic measurements of AP dynamics to be performed extracellularly or even outside intact organisms. To date, however, magnetic techniques for sensing neuronal activity have either operated at the macroscale with coarse spatial and/or temporal resolution—e.g., magnetic resonance imaging methods and magnetoencephalography—or been restricted to biophysics studies of excised neurons probed with cryogenic or bulky detectors that do not provide single-neuron spatial resolution and are not scalable to functional networks or intact organisms. Here, we show that AP magnetic sensing can be realized with both single-neuron sensitivity and intact organism applicability using optically probed nitrogen-vacancy (NV) quantum defects in diamond, operated under ambient conditions and with the NV diamond sensor in close proximity (∼10 µm) to the biological sample. We demonstrate this method for excised single neurons from marine worm and squid, and then exterior to intact, optically opaque marine worms for extended periods and with no observed adverse effect on the animal. NV diamond magnetometry is noninvasive and label-free and does not cause photodamage. The method provides precise measurement of AP waveforms from individual neurons, as well as magnetic field correlates of the AP conduction velocity, and directly determines the AP propagation direction through the inherent sensitivity of NVs to the associated AP magnetic field vector.Publication Mapping the microscale origins of magnetic resonance image contrast with subcellular diamond magnetometry(Nature Publishing Group UK, 2018) Davis, Hunter C.; Ramesh, Pradeep; Bhatnagar, Aadyot; Lee-Gosselin, Audrey; Barry, John; Glenn, David; Walsworth, Ronald; Shapiro, Mikhail G.Magnetic resonance imaging (MRI) is a widely used biomedical imaging modality that derives much of its contrast from microscale magnetic field patterns in tissues. However, the connection between these patterns and the appearance of macroscale MR images has not been the subject of direct experimental study due to a lack of methods to map microscopic fields in biological samples. Here, we optically probe magnetic fields in mammalian cells and tissues with submicron resolution and nanotesla sensitivity using nitrogen-vacancy diamond magnetometry, and combine these measurements with simulations of nuclear spin precession to predict the corresponding MRI contrast. We demonstrate the utility of this technology in an in vitro model of macrophage iron uptake and histological samples from a mouse model of hepatic iron overload. In addition, we follow magnetic particle endocytosis in live cells. This approach bridges a fundamental gap between an MRI voxel and its microscopic constituents.Publication Limits to Resolution of CW STED Microscopy(Academic Press (Elsevier BV), 2013) Trifonov, Alexei; Jaskula, Jean-Christophe; Teulon, Claire; Glenn, David; Bar-Gill, Nir; Walsworth, RonaldWe report a systematic theoretical and experimental study of the limits to spatial resolution for stimulated emission depletion (STED) superresolution fluorescence microscopy using continuous wave (CW) laser beams. We develop a theoretical framework for CW STED imaging from point fluorescent emitters and calculate the dependence of 2D spatial resolution on the power of the CW excitation (pump) beam, as well as the power, contrast, and polarization of the CW STED “doughnut” beam. We perform CW STED experiments on (non-bleaching) nitrogen vacancy (NV) color centers in diamond and find good agreement with the theoretical expressions for CW STED spatial resolution. Our results will aid the optimization and application of CW STED microscopy in both the physical and life sciences.Publication A Genetic Strategy for Probing the Functional Diversity of Magnetosome Formation(Public Library of Science, 2015) Rahn-Lee, Lilah; Byrne, Meghan E.; Zhang, Manjing; Le Sage, David; Glenn, David; Milbourne, Timothy; Walsworth, Ronald; Vali, Hojatollah; Komeili, ArashModel genetic systems are invaluable, but limit us to understanding only a few organisms in detail, missing the variations in biological processes that are performed by related organisms. One such diverse process is the formation of magnetosome organelles by magnetotactic bacteria. Studies of model magnetotactic α-proteobacteria have demonstrated that magnetosomes are cubo-octahedral magnetite crystals that are synthesized within pre-existing membrane compartments derived from the inner membrane and orchestrated by a specific set of genes encoded within a genomic island. However, this model cannot explain all magnetosome formation, which is phenotypically and genetically diverse. For example, Desulfovibrio magneticus RS-1, a δ-proteobacterium for which we lack genetic tools, produces tooth-shaped magnetite crystals that may or may not be encased by a membrane with a magnetosome gene island that diverges significantly from those of the α-proteobacteria. To probe the functional diversity of magnetosome formation, we used modern sequencing technology to identify hits in RS-1 mutated with UV or chemical mutagens. We isolated and characterized mutant alleles of 10 magnetosome genes in RS-1, 7 of which are not found in the α-proteobacterial models. These findings have implications for our understanding of magnetosome formation in general and demonstrate the feasibility of applying a modern genetic approach to an organism for which classic genetic tools are not available.Publication Nanodiamond-enhanced MRI via in situ hyperpolarization(Nature Publishing Group, 2017) Waddington, David E. J.; Sarracanie, Mathieu; Zhang, Huiliang; Salameh, Najat; Glenn, David; Rej, Ewa; Gaebel, Torsten; Boele, Thomas; Walsworth, Ronald; Reilly, David J.; Rosen, MatthewNanodiamonds are of interest as nontoxic substrates for targeted drug delivery and as highly biostable fluorescent markers for cellular tracking. Beyond optical techniques, however, options for noninvasive imaging of nanodiamonds in vivo are severely limited. Here, we demonstrate that the Overhauser effect, a proton–electron polarization transfer technique, can enable high-contrast magnetic resonance imaging (MRI) of nanodiamonds in water at room temperature and ultra-low magnetic field. The technique transfers spin polarization from paramagnetic impurities at nanodiamond surfaces to 1H spins in the surrounding water solution, creating MRI contrast on-demand. We examine the conditions required for maximum enhancement as well as the ultimate sensitivity of the technique. The ability to perform continuous in situ hyperpolarization via the Overhauser mechanism, in combination with the excellent in vivo stability of nanodiamond, raises the possibility of performing noninvasive in vivo tracking of nanodiamond over indefinitely long periods of time.Publication High-Flux Beam Source for Cold, Slow Atoms or Molecules(American Physical Society (APS), 2005) Maxwell, S. E.; Brahms, N.; deCarvalho, R.; Glenn, David; Helton, J. S.; Nguyen, S. V.; Patterson, D.; Petricka, J.; DeMille, D.; Doyle, JohnWe demonstrate and characterize a high-flux beam source for cold, slow atoms or molecules. The desired species is vaporized using laser ablation, then cooled by thermalization in a cryogenic cell of buffer gas. The beam is formed by particles exiting a hole in the buffer gas cell. We characterize the properties of the beam (flux, forward velocity, temperature) for both an atom (Na) and a molecule (PbO) under varying buffer gas density, and discuss conditions for optimizing these beam parameters. Our source compares favorably to existing techniques of beam formation, for a variety of applications.Publication Correlative light and electron microscopy using cathodoluminescence from nanoparticles with distinguishable colours(Nature Publishing Group, 2012) Glenn, David; Zhang, Huidan; Kasthuri, Narayanan; Schalek, Richard; Lo, P. K.; Trifonov, Alexei; Park, Hongkun; Lichtman, Jeff; Walsworth, RonaldCorrelative light and electron microscopy promises to combine molecular specificity with nanoscale imaging resolution. However, there are substantial technical challenges including reliable co-registration of optical and electron images, and rapid optical signal degradation under electron beam irradiation. Here, we introduce a new approach to solve these problems: imaging of stable optical cathodoluminescence emitted in a scanning electron microscope by nanoparticles with controllable surface chemistry. We demonstrate well-correlated cathodoluminescence and secondary electron images using three species of semiconductor nanoparticles that contain defects providing stable, spectrally-distinguishable cathodoluminescence. We also demonstrate reliable surface functionalization of the particles. The results pave the way for the use of such nanoparticles for targeted labeling of surfaces to provide nanoscale mapping of molecular composition, indicated by cathodoluminescence colour, simultaneously acquired with structural electron images in a single instrument.Publication Magnetic Field Imaging with Nitrogen-Vacancy Ensembles(Institute of Physics, 2011) Pham, Linh; Le Sage, David; Stanwix, Paul L.; Yeung, Tsun Kwan; Glenn, David; Trifonov, Alexei; Cappellaro, Paola; Hemmer, Philip; Lukin, Mikhail; Park, Hongkun; Yacoby, Amir; Walsworth, RonaldWe demonstrate a method of imaging spatially varying magnetic fields using a thin layer of nitrogen-vacancy (NV) centers at the surface of a diamond chip. Fluorescence emitted by the two-dimensional NV ensemble is detected by a CCD array, from which a vector magnetic field pattern is reconstructed. As a demonstration, ac current is passed through wires placed on the diamond chip surface, and the resulting ac magnetic field patterns are imaged using an echo-based technique with sub-micron resolution over a \(140 \mu m\) x \(140 \mu m\) field of view, giving single-pixel sensitivity \(\sim 100 nT / \sqrt{Hz}\). We discuss ongoing efforts to further improve the sensitivity, as well as potential bioimaging applications such as real-time imaging of activity in functional, cultured networks of neurons.Publication High-Resolution Magnetic Resonance Spectroscopy Using a Solid-State Spin Sensor(Springer Nature, 2018-03) Glenn, David; Bucher, Dominik; Lee, Junghyun; Lukin, Mikhail; Park, Hongkun; Walsworth, RonaldQuantum systems that consist of solid-state electronic spins can be sensitive detectors of nuclear magnetic resonance (NMR) signals, particularly from very small samples. For example, nitrogen–vacancy centres in diamond have been used to record NMR signals from nanometre-scale samples1,2,3, with sensitivity sufficient to detect the magnetic field produced by a single protein4. However, the best reported spectral resolution for NMR of molecules using nitrogen–vacancy centres is about 100 hertz5. This is insufficient to resolve the key spectral identifiers of molecular structure that are critical to NMR applications in chemistry, structural biology and materials research, such as scalar couplings (which require a resolution of less than ten hertz6) and small chemical shifts (which require a resolution of around one part per million of the nuclear Larmor frequency). Conventional, inductively detected NMR can provide the necessary high spectral resolution, but its limited sensitivity typically requires millimetre-scale samples, precluding applications that involve smaller samples, such as picolitre-volume chemical analysis or correlated optical and NMR microscopy. Here we demonstrate a measurement technique that uses a solid-state spin sensor (a magnetometer) consisting of an ensemble of nitrogen–vacancy centres in combination with a narrowband synchronized readout protocol7,8,9 to obtain NMR spectral resolution of about one hertz. We use this technique to observe NMR scalar couplings in a micrometre-scale sample volume of approximately ten picolitres. We also use the ensemble of nitrogen–vacancy centres to apply NMR to thermally polarized nuclear spins and resolve chemical-shift spectra from small molecules. Our technique enables analytical NMR spectroscopy at the scale of single cells.