Jennifer Dionne

All Publications

• Toward rapid infectious disease diagnosis with advances in surface-enhanced Raman spectroscopy. The Journal of chemical physics Tadesse, L. F., Safir, F., Ho, C., Hasbach, X., Khuri-Yakub, B. P., Jeffrey, S. S., Saleh, A. A., Dionne, J. 2020; 152 (24): 240902

  Abstract

  In a pandemic era, rapid infectious disease diagnosis is essential. Surface-enhanced Raman spectroscopy (SERS) promises sensitive and specific diagnosis including rapid point-of-care detection and drug susceptibility testing. SERS utilizes inelastic light scattering arising from the interaction of incident photons with molecular vibrations, enhanced by orders of magnitude with resonant metallic or dielectric nanostructures. While SERS provides a spectral fingerprint of the sample, clinical translation is lagged due to challenges in consistency of spectral enhancement, complexity in spectral interpretation, insufficient specificity and sensitivity, and inefficient workflow from patient sample collection to spectral acquisition. Here, we highlight the recent, complementary advances that address these shortcomings, including (1) design of label-free SERS substrates and data processing algorithms that improve spectral signal and interpretability, essential for broad pathogen screening assays; (2) development of new capture and affinity agents, such as aptamers and polymers, critical for determining the presence or absence of particular pathogens; and (3) microfluidic and bioprinting platforms for efficient clinical sample processing. We also describe the development of low-cost, point-of-care, optical SERS hardware. Our paper focuses on SERS for viral and bacterial detection, in hopes of accelerating infectious disease diagnosis, monitoring, and vaccine development. With advances in SERS substrates, machine learning, and microfluidics and bioprinting, the specificity, sensitivity, and speed of SERS can be readily translated from laboratory bench to patient bedside, accelerating point-of-care diagnosis, personalized medicine, and precision health.

  View details for DOI 10.1063/1.5142767

  View details for PubMedID 32610995

• Revealing multiple classes of stable quantum emitters in hexagonal boron nitride with correlated optical and electron microscopy. Nature materials Hayee, F., Yu, L., Zhang, J. L., Ciccarino, C. J., Nguyen, M., Marshall, A. F., Aharonovich, I., Vuckovic, J., Narang, P., Heinz, T. F., Dionne, J. A. 2020

  Abstract

  Defects in hexagonal boron nitride (hBN) exhibit high-brightness, room-temperature quantum emission, but their large spectral variability and unknown local structure challenge their technological utility. Here, we directly correlate hBN quantum emission with local strain using a combination of photoluminescence (PL), cathodoluminescence (CL) and nanobeam electron diffraction. Across 40 emitters, we observe zero phonon lines (ZPLs) in PL and CL ranging from 540 to 720nm. CL mapping reveals that multiple defects and distinct defect species located within an optically diffraction-limited region can each contribute to the observed PL spectra. Local strain maps indicate that strain is not required to activate the emitters and is not solely responsible for the observed ZPL spectral range. Instead, at least four distinct defect classes are responsible for the observed emission range, and all four classes are stable upon both optical and electron illumination. Our results provide a foundation for future atomic-scale optical characterization of colour centres.

  View details for DOI 10.1038/s41563-020-0616-9

  View details for PubMedID 32094492

• High Quality Factor Dielectric Metasurfaces for Ultraviolet Circular Dichroism Spectroscopy ACS PHOTONICS Hu, J., Lawrence, M., Dionne, J. A. 2020; 7 (1): 36–42

  View details for DOI 10.1021/acsphotonics.9b01352

  View details for Web of Science ID 000508475800004

• Nanophotonic Platforms for Chiral Sensing and Separation. Accounts of chemical research Solomon, M. L., Saleh, A. A., Poulikakos, L. V., Abendroth, J. M., Tadesse, L. F., Dionne, J. A. 2020

  Abstract

  Chirality in Nature can be found across all length scales, from the subatomic to the galactic. At the molecular scale, the spatial dissymmetry in the atomic arrangements of pairs of mirror-image molecules, known as enantiomers, gives rise to fascinating and often critical differences in chemical and physical properties. With increasing hierarchical complexity, protein function, cell communication, and organism health rely on enantioselective interactions between molecules with selective handedness. For example, neurodegenerative and neuropsychiatric disorders including Alzheimer's and Parkinson's diseases have been linked to distortion of chiral-molecular structure. Moreover, d-amino acids have become increasingly recognized as potential biomarkers, necessitating comprehensive analytical methods for diagnosis that are capable of distinguishing l- from d-forms and quantifying trace concentrations of d-amino acids. Correspondingly, many pharmaceuticals and agrochemicals consist of chiral molecules that target particular enantioselective pathways. Yet, despite the importance of molecular chirality, it remains challenging to sense and to separate chiral compounds. Chiral-optical spectroscopies are designed to analyze the purity of chiral samples, but they are often insensitive to the trace enantiomeric excess that might be present in a patient sample, such as blood, urine, or sputum, or pharmaceutical product. Similarly, existing separation schemes to enable enantiopure solutions of chiral products are inefficient or costly. Consequently, most pharmaceuticals or agrochemicals are sold as racemic mixtures, with reduced efficacy and potential deleterious impacts. Recent advances in nanophotonics lay the foundation toward highly sensitive and efficient chiral detection and separation methods. In this Account, we highlight our group's effort to leverage nanoscale chiral light-matter interactions to detect, characterize, and separate enantiomers, potentially down to the single molecule level. Notably, certain resonant nanostructures can significantly enhance circular dichroism for improved chiral sensing and spectroscopy as well as high-yield enantioselective photochemistry. We first describe how achiral metallic and dielectric nanostructures can be utilized to increase the local optical chirality density by engineering the coupling between electric and magnetic optical resonances. While plasmonic nanoparticles locally enhance the optical chirality density, high-index dielectric nanoparticles can enable large-volume and uniform-sign enhancements in the optical chirality density. By overlapping these electric and magnetic resonances, local chiral fields can be enhanced by several orders of magnitude. We show how these design rules can enable high-yield enantioselective photochemistry and project a 2000-fold improvement in the yield of a photoionization reaction. Next, we discuss how optical forces can enable selective manipulation and separation of enantiomers. We describe the design of low-power enantioselective optical tweezers with the ability to trap sub-10 nm dielectric particles. We also characterize their chiral-optical forces with high spatial and force resolution using combined optical and atomic force microscopy. These optical tweezers exhibit an enantioselective optical force contrast exceeding 10 pN, enabling selective attraction or repulsion of enantiomers based on the illumination polarization. Finally, we discuss future challenges and opportunities spanning fundamental research to technology translation. Disease detection in the clinic as well as pharmaceutical and agrochemical industrial applications requiring large-scale, high-throughput production will gain particular benefit from the simplicity and relative low cost that nanophotonic platforms promise.

  View details for DOI 10.1021/acs.accounts.9b00460

  View details for PubMedID 31913015

• Dynamic Focusing with High-Quality-Factor Metalenses. Nano letters Klopfer, E. n., Lawrence, M. n., Barton, D. R., Dixon, J. n., Dionne, J. A. 2020

  Abstract

  Metasurface lenses provide an ultrathin platform in which to focus light, but weak light-matter interactions limit their dynamic tunability. Here we design submicron-thick, ultrahigh quality factor (high-Q) metalenses that enable dynamic modulation of the focal length and intensity. Using full-field simulations, we show that quality factors exceeding 5000 can be generated by including subtle, periodic perturbations within the constituent Si nanoantennas. Such high-Q resonances enable lens modulation based on the nonlinear Kerr effect, with focal lengths varying from 4 to 6.5 μm and focal intensities decreasing by half as input intensity increases from 0.1 to 1 mW/μm2. We also show how multiple high-Q resonances can be embedded in the lens response through judicious placement of the perturbations. Our high-Q lens design, with quality factors 2 orders of magnitude higher than existing lens designs, provides a foundation for reconfigurable, multiplexed, and hyperspectral metasurface imaging platforms.

  View details for DOI 10.1021/acs.nanolett.0c01359

  View details for PubMedID 32497434

• Sub-20 nm Core-Shell-Shell Nanoparticles for Bright Upconversion and Enhanced Forster Resonant Energy Transfer. Journal of the American Chemical Society Siefe, C., Mehlenbacher, R. D., Peng, C. S., Zhang, Y., Fischer, S., Lay, A., McLellan, C. A., Alivisatos, A. P., Chu, S., Dionne, J. A. 2019

  Abstract

  Upconverting nanoparticles provide valuable benefits as optical probes for bioimaging and Forster resonant energy transfer (FRET) due to their high signal-to-noise ratio, photostability, and biocompatibility; yet, making nanoparticles small yields a significant decay in brightness due to increased surface quenching. Approaches to improve the brightness of UCNPs exist but often require increased nanoparticle size. Here we present a unique core-shell-shell nanoparticle architecture for small (sub-20 nm), bright upconversion with several key features: (1) maximal sensitizer concentration in the core for high near-infrared absorption, (2) efficient energy transfer between core and interior shell for strong emission, and (3) emitter localization near the nanoparticle surface for efficient FRET. This architecture consists of beta-NaYbF4 (core) @NaY0.8-xErxGd0.2F4 (interior shell) @NaY0.8Gd0.2F4 (exterior shell), where sensitizer and emitter ions are partitioned into core and interior shell, respectively. Emitter concentration is varied (x = 1, 2, 5, 10, 20, 50, and 80%) to investigate influence on single particle brightness, upconversion quantum yield, decay lifetimes, and FRET coupling. We compare these seven samples with the field-standard core-shell architecture of beta-NaY0.58Gd0.2Yb0.2Er0.02F4 (core) @NaY0.8Gd0.2F4 (shell), with sensitizer and emitter ions codoped in the core. At a single particle level, the core-shell-shell design was up to 2-fold brighter than the standard core-shell design. Further, by coupling a fluorescent dye to the surface of the two different architectures, we demonstrated up to 8-fold improved emission enhancement with the core-shell-shell compared to the core-shell design. We show how, given proper consideration for emitter concentration, we can design a unique nanoparticle architecture to yield comparable or improved brightness and FRET coupling within a small volume.

  View details for DOI 10.1021/jacs.9b09571

  View details for PubMedID 31592655

• Nanoscale nonreciprocity via photon-spin-polarized stimulated Raman scattering. Nature communications Lawrence, M., Dionne, J. A. 2019; 10 (1): 3297

  Abstract

  Time reversal symmetry stands as a fundamental restriction on the vast majority of optical systems and devices. The reciprocal nature of Maxwell's equations in linear, time-invariant media adds complexity and scale to photonic diodes, isolators, circulators and also sets fundamental efficiency limits on optical energy conversion. Though many theoretical proposals and low frequency demonstrations of nonreciprocity exist, Faraday rotation remains the only known nonreciprocal mechanism that persists down to the atomic scale. Here, we present photon-spin-polarized stimulated Raman scattering as a new nonreciprocal optical phenomenon which has, in principle, no lower size limit. Exploiting this process, we numerically demonstrate nanoscale nonreciprocal transmission of free-space beams at near-infrared frequencies with a 250nm thick silicon metasurface as well as a fully-subwavelength plasmonic gap nanoantenna. In revealing all-optical spin-splitting, our results provide a foundation for compact nonreciprocal communication and computing technologies, from nanoscale optical isolators and full-duplex nanoantennas to topologically-protected networks.

  View details for DOI 10.1038/s41467-019-11175-z

  View details for PubMedID 31341164

• Optically Robust and Biocompatible Mechanosensitive Upconverting Nanoparticles. ACS central science Lay, A., Sheppard, O. H., Siefe, C., McLellan, C. A., Mehlenbacher, R. D., Fischer, S., Goodman, M. B., Dionne, J. A. 2019; 5 (7): 1211-1222

  Abstract

  Upconverting nanoparticles (UCNPs) are promising tools for background-free imaging and sensing. However, their usefulness for in vivo applications depends on their biocompatibility, which we define by their optical performance in biological environments and their toxicity in living organisms. For UCNPs with a ratiometric color response to mechanical stress, consistent emission intensity and color are desired for the particles under nonmechanical stimuli. Here, we test the biocompatibility and mechanosensitivity of α-NaYF4:Yb,Er@NaLuF4 nanoparticles. First, we ligand-strip these particles to render them dispersible in aqueous media. Then, we characterize their mechanosensitivity (∼30% in the red-to-green spectral ratio per GPa), which is nearly 3-fold greater than those coated in oleic acid. We next design a suite of ex vivo and in vivo tests to investigate their structural and optical properties under several biorelevant conditions: over time in various buffers types, as a function of pH, and in vivo along the digestive tract of Caenorhabditis elegans worms. Finally, to ensure that the particles do not perturb biological function in C. elegans, we assess the chronic toxicity of nanoparticle ingestion using a reproductive brood assay. In these ways, we determine that mechanosensitive UCNPs are biocompatible, i.e., optically robust and nontoxic, for use as in vivo sensors to study animal digestion.

  View details for DOI 10.1021/acscentsci.9b00300

  View details for PubMedID 31403071

  View details for PubMedCentralID PMC6661856

• Small Alkaline-Earth-based Core/Shell Nanoparticles for Efficient Upconversion NANO LETTERS Fischer, S., Mehlenbacher, R. D., Lay, A., Siefe, C., Alivisatos, A., Dionne, J. A. 2019; 19 (6): 3878–85

  View details for DOI 10.1021/acs.nanolett.9b01057

  View details for Web of Science ID 000471834900063

• Bimetallic nanostructures: combining plasmonic and catalytic metals for photocatalysis ADVANCES IN PHYSICS-X Sytwu, K., Vadai, M., Dionne, J. A. 2019; 4 (1)

  View details for DOI 10.1080/23746149.2019.1619480

  View details for Web of Science ID 000471185100001

• Bright sub-20-nm cathodoluminescent nanoprobes for electron microscopy NATURE NANOTECHNOLOGY Prigozhin, M. B., Maurer, P. C., Courtis, A. M., Liu, N., Wisser, M. D., Siefe, C., Tian, B., Chan, E., Song, G., Fischer, S., Aloni, S., Ogletree, D., Barnard, E. S., Joubert, L., Rao, J., Alivisatos, A., Macfarlane, R. M., Cohen, B. E., Cui, Y., Dionne, J. A., Chu, S. 2019; 14 (5): 420-+

  View details for DOI 10.1038/s41565-019-0395-0

  View details for Web of Science ID 000467053100016

• Light years: Combined optical and environmental electron microscopy to visualize photonic processes with atomic-scale resolution Dionne, J. A. AMER CHEMICAL SOC. 2019

  View details for Web of Science ID 000478860504348

• Unraveling the origin of chirality from plasmonic nanoparticle-protein complexes. Science (New York, N.Y.) Zhang, Q. n., Hernandez, T. n., Smith, K. W., Hosseini Jebeli, S. A., Dai, A. X., Warning, L. n., Baiyasi, R. n., McCarthy, L. A., Guo, H. n., Chen, D. H., Dionne, J. A., Landes, C. F., Link, S. n. 2019; 365 (6460): 1475–78

  Abstract

  Plasmon-coupled circular dichroism has emerged as a promising approach for ultrasensitive detection of biomolecular conformations through coupling between molecular chirality and surface plasmons. Chiral nanoparticle assemblies without chiral molecules present also have large optical activities. We apply single-particle circular differential scattering spectroscopy coupled with electron imaging and simulations to identify both structural chirality of plasmonic aggregates and plasmon-coupled circular dichroism induced by chiral proteins. We establish that both chiral aggregates and just a few proteins in interparticle gaps of achiral assemblies are responsible for the ensemble signal, but single nanoparticles do not contribute. We furthermore find that the protein plays two roles: It transfers chirality to both chiral and achiral plasmonic substrates, and it is also responsible for the chiral three-dimensional assembly of nanorods. Understanding these underlying factors paves the way toward sensing the chirality of single biomolecules.

  View details for DOI 10.1126/science.aax5415

  View details for PubMedID 31604278

• Rapid identification of pathogenic bacteria using Raman spectroscopy and deep learning. Nature communications Ho, C. S., Jean, N. n., Hogan, C. A., Blackmon, L. n., Jeffrey, S. S., Holodniy, M. n., Banaei, N. n., Saleh, A. A., Ermon, S. n., Dionne, J. n. 2019; 10 (1): 4927

  Abstract

  Raman optical spectroscopy promises label-free bacterial detection, identification, and antibiotic susceptibility testing in a single step. However, achieving clinically relevant speeds and accuracies remains challenging due to weak Raman signal from bacterial cells and numerous bacterial species and phenotypes. Here we generate an extensive dataset of bacterial Raman spectra and apply deep learning approaches to accurately identify 30 common bacterial pathogens. Even on low signal-to-noise spectra, we achieve average isolate-level accuracies exceeding 82% and antibiotic treatment identification accuracies of 97.0±0.3%. We also show that this approach distinguishes between methicillin-resistant and -susceptible isolates of Staphylococcus aureus (MRSA and MSSA) with 89±0.1% accuracy. We validate our results on clinical isolates from 50 patients. Using just 10 bacterial spectra from each patient isolate, we achieve treatment identification accuracies of 99.7%. Our approach has potential for culture-free pathogen identification and antibiotic susceptibility testing, and could be readily extended for diagnostics on blood, urine, and sputum.

  View details for DOI 10.1038/s41467-019-12898-9

  View details for PubMedID 31666527

• Enantiospecific Optical Enhancement of Chiral Sensing and Separation with Dielectric Metasurfaces ACS PHOTONICS Solomon, M. L., Hu, J., Lawrence, M., Garcia-Etxarri, A., Dionne, J. A. 2019; 6 (1): 43–49

  View details for DOI 10.1021/acsphotonics.8b01365

  View details for Web of Science ID 000456350400007

• Optical Helicity and Optical Chirality in Free Space and in the Presence of Matter Symmetry 2019, 11(9) Poulikakos, L. V., Dionne, J. A., Garcia-Etxarri, A. 2019; 11 (9)

  View details for DOI 10.3390/sym11091113

• In-situ observation of plasmon-controlled photocatalytic dehydrogenation of individual palladium nanoparticles NATURE COMMUNICATIONS Vadai, M., Angell, D. K., Hayee, F., Sytwu, K., Dionne, J. A. 2018; 9

  View details for DOI 10.1038/s41467-018-07108-x

  View details for Web of Science ID 000449363900007

• In-situ observation of plasmon-controlled photocatalytic dehydrogenation of individual palladium nanoparticles. Nature communications Vadai, M., Angell, D. K., Hayee, F., Sytwu, K., Dionne, J. A. 2018; 9 (1): 4658

  Abstract

  Plasmonic nanoparticle catalysts offer improved light absorption and carrier transport compared to traditional photocatalysts. However, it remains unclear how plasmonic excitation affects multi-step reaction kinetics and promotes site-selectivity. Here, we visualize a plasmon-induced reaction at the sub-nanoparticle level in-situ and in real-time. Using an environmental transmission electron microscope combined with light excitation, we study the photocatalytic dehydrogenation of individual palladium nanocubes coupled to gold nanoparticles with sub-2 nanometer spatial resolution. We find that plasmons increase the rate of distinct reaction steps with unique time constants; enable reaction nucleation at specific sites closest to the electromagnetic hot spots; and appear to open a new reaction pathway that is not observed without illumination. These effects are explained by plasmon-mediated population of excited-state hybridized palladium-hydrogen orbitals. Our results help elucidate the role of plasmons in light-driven photochemical transformations, en-route to design of site-selective and product-specific photocatalysts.

  View details for PubMedID 30405133

• Equilibration of Photogenerated Charge Carriers in Plasmonic Core@Shell Nanoparticles JOURNAL OF PHYSICAL CHEMISTRY C Parente, M., Sheikholeslami, S., Naik, G., Dionne, J. A., Baldi, A. 2018; 122 (41): 23631–38

  View details for DOI 10.1021/acs.jpcc.8b05003

  View details for Web of Science ID 000448087900042

• Active polarization control with a parity-time-symmetric plasmonic resonator PHYSICAL REVIEW B Baum, B., Lawrence, M., Barton, D., Dionne, J., Alaeian, H. 2018; 98 (16)

  View details for DOI 10.1103/PhysRevB.98.165418

  View details for Web of Science ID 000447184600006

• Visualizing Facet-Dependent Hydrogenation Dynamics in Individual Palladium Nanoparticles. Nano letters Sytwu, K., Hayee, F., Narayan, T. C., Koh, A. L., Sinclair, R., Dionne, J. A. 2018

  Abstract

  Surface faceting in nanoparticles can profoundly impact the rate and selectivity of chemical transformations. However, the precise role of surface termination can be challenging to elucidate because many measurements are performed on ensembles of particles and do not have sufficient spatial resolution to observe reactions at the single and subparticle level. Here, we investigate solute intercalation in individual palladium hydride nanoparticles with distinct surface terminations. Using a combination of diffraction, electron energy loss spectroscopy, and dark-field contrast in an environmental transmission electron microscope (TEM), we compare the thermodynamics and directly visualize the kinetics of 40-70 nm {100}-terminated cubes and {111}-terminated octahedra with approximately 2 nm spatial resolution. Despite their distinct surface terminations, both particle morphologies nucleate the new phase at the tips of the particle. However, whereas the hydrogenated phase-front must rotate from [111] to [100] to propagate in cubes, the phase-front can propagate along the [100], [110], and [111] directions in octahedra. Once the phase-front is established, the interface propagates linearly with time and is rate-limited by surface-to-subsurface diffusion and/or the atomic rearrangements needed to accommodate lattice strain. Following nucleation, both particle morphologies take approximately the same time to reach equilibrium, hydrogenating at similar pressures and without equilibrium phase coexistence. Our results highlight the importance of low-coordination number sites and strain, more so than surface faceting, in governing solute-driven reactions.

  View details for PubMedID 30148640

• Plasmonic approaches for visualizing and controlling intercalation-driven phase transformations Dionne, J., Hayee, F., Vadai, M., Angell, D., Sytwu, K. AMER CHEMICAL SOC. 2018

  View details for Web of Science ID 000447609103687

• In-situ visualization of plasmon-induced hydrogenation reactions in individual palladium nanocubes Vadai, M., Angell, D., Hayee, F., Sytwu, K., Dionne, J. AMER CHEMICAL SOC. 2018

  View details for Web of Science ID 000447600004268

• Electric field sensitive upconverting nanoparticles: Toward background free in vivo action potential imaging Mehlenbacher, R., Siefe, C., Lay, A., Dionne, J. AMER CHEMICAL SOC. 2018

  View details for Web of Science ID 000447600004298

• Exploring nanoparticle architecture to design small, bright upconverting nanoparticles for bioimaging Siefe, C., Mehlenbacher, R., Fischer, S., Lay, A., Dionne, J. AMER CHEMICAL SOC. 2018

  View details for Web of Science ID 000447600003855

• In-situ observation of plasmon-driven hydrogenation reactions within Au@Pd coreshell nanoparticles Sytwu, K., Vadai, M., Hayee, F., Koh, A., Sinclair, R., Dionne, J. AMER CHEMICAL SOC. 2018

  View details for Web of Science ID 000447600004349

• Mechanosensitive upconverting nanoparticles for visualizing mechanical forces in vivo Lay, A., Siefe, C., Fischer, S., Mehlenbacher, R., Das, A., Nekimken, A., Ke, F., Mao, W., Pruitt, B., Cohen, B., Alivisatos, P., Goodman, M., Dionne, J. AMER CHEMICAL SOC. 2018

  View details for Web of Science ID 000447600003857

• Nanophotonic approaches to observe and control atomic and molecular processes Dionne, J. AMER CHEMICAL SOC. 2018

  View details for Web of Science ID 000447609102530

• Response to "Comment on 'Enantioselective Optical Trapping of Chiral Nanoparticles with Plasmonic Tweezers'" ACS PHOTONICS Zhao, Y., Dionne, J. 2018; 5 (6): 2535–36

  View details for DOI 10.1021/acsphotonics.7b01610

  View details for Web of Science ID 000436211900059

• The social scientist NATURE NANOTECHNOLOGY Dionne, J. A. 2018; 13 (5): 434

  View details for PubMedID 29728664

• Improving Quantum Yield of Upconverting Nanoparticles in Aqueous Media via Emission Sensitization NANO LETTERS Wisser, M. D., Fischer, S., Siefe, C., Alivisatos, A., Salleo, A., Dionne, J. A. 2018; 18 (4): 2689–95

  Abstract

  We demonstrate a facile method to improve upconversion quantum yields in Yb,Er-based nanoparticles via emission dye-sensitization. Using the commercially available dye ATTO 542, chosen for its high radiative rate and significant spectral overlap with the green emission of Er3+, we decorate the surfaces of sub-25 nm hexagonal-phase Na(Y/Gd/Lu)0.8F4:Yb0.18Er0.02 upconverting nanoparticles with varying dye concentrations. Upconversion photoluminescence and absorption spectroscopy provide experimental confirmation of energy transfer to and emission from the dye molecules. Upconversion quantum yield is observed to increase with dye sensitization, with the highest enhancement measured for the smallest particles investigated (10.9 nm in diameter); specifically, these dye-decorated particles are more than 2× brighter than are unmodified, organic-soluble nanoparticles and more than 10× brighter than are water-soluble nanoparticles. We also observe 3× lifetime reductions with dye adsorption, confirming the quantum yield enhancement to result from the high radiative rate of the dye. The approach detailed in this work is widely implementable, renders the nanoparticles water-soluble, and most significantly improves sub-15 nm nanoparticles, making our method especially attractive for biological imaging applications.

  View details for PubMedID 29589449

• Roadmap on plasmonics JOURNAL OF OPTICS Stockman, M. I., Kneipp, K., Bozhevolnyi, S. I., Saha, S., Dutta, A., Ndukaife, J., Kinsey, N., Reddy, H., Guler, U., Shalaev, V. M., Boltasseva, A., Gholipour, B., Krishnamoorthy, H. S., MacDonald, K. F., Soci, C., Zheludev, N. I., Savinov, V., Singh, R., Gross, P., Lienau, C., Vadai, M., Solomon, M. L., Barton, D. R., Lawrence, M., Dionne, J. A., Boriskina, S. V., Esteban, R., Aizpurua, J., Zhang, X., Yang, S., Wang, D., Wang, W., Odom, T. W., Accanto, N., de Roque, P. M., Hancu, I. M., Piatkowski, L., van Hulst, N. F., Kling, M. F. 2018; 20 (4)

  View details for DOI 10.1088/2040-8986/aaa114

  View details for Web of Science ID 000447428100001

• Chemically Responsive Elastomers Exhibiting Unity-Order Refractive Index Modulation. Advanced materials (Deerfield Beach, Fla.) Wu, D. M., Solomon, M. L., Naik, G. V., Garcia-Etxarri, A., Lawrence, M., Salleo, A., Dionne, J. A. 2018; 30 (7)

  Abstract

  Chameleons are masters of light, expertly changing their color, pattern, and reflectivity in response to their environment. Engineered materials that share this tunability can be transformative, enabling active camouflage, tunable holograms, and novel colorimetric medical sensors. While progress has been made in creating artificial chameleon skin, existing schemes often require external power, are not continuously tunable, and may prove too stiff or bulky for applications. Here, a chemically tunable, large-area metamaterial is demonstrated that accesses a wide range of colors and refractive indices. An ordered monolayer of nanoresonators is fabricated, then its optical response is dynamically tuned by infiltrating its polymer substrate with solvents. The material shows a strong magnetic response with a dependence on resonator spacing that leads to a highly tunable effective permittivity, permeability, and refractive index spanning negative and positive values. The unity-order index tuning exceeds that of traditional electro-optic and photochromic materials and is robust to cycling, providing a path toward programmable optical elements and responsive light routing.

  View details for PubMedID 29315902

• Nonreciprocal Flat Optics with Silicon Metasurfaces NANO LETTERS Lawrence, M., Barton, D. R., Dionne, J. A. 2018; 18 (2): 1104–9

  Abstract

  Metasurfaces enable almost complete control of light through ultrathin, subwavelength surfaces by locally and abruptly altering the scattered phase. To date, however, all metasurfaces obey time-reversal symmetry, meaning that forward and backward traveling waves will trace identical paths when being reflected, refracted, or diffracted. Here, we use full-field calculations to design a passive metasurface for nonreciprocal transmission of both direct and anomalously refracted near-infrared light over nanoscale optical path lengths. The metasurface consists of a 100 nm-thick, periodically patterned Si slab. Owing to the high-quality-factor resonances of the metasurface and the inherent Kerr nonlinearities of Si, this structure acts as an optical diode for free-space optical signals. This structure also exhibits nonreciprocal anomalous refraction with appropriate patterning to form a phase gradient metasurface. Compared to existing schemes for breaking time-reversal symmetry, our platform enables subwavelength nonreciprocity for arbitrary free-space optical inputs and provides a straightforward path to experimental realization. The concept is also generalizable to other metasurface functions, providing a foundation for one-way lensing and holography.

  View details for PubMedID 29369641

• Nanomaterials for in vivo imaging of mechanical forces and electrical fields NATURE REVIEWS MATERIALS Mehlenbacher, R. D., Kolbl, R., Lay, A., Dionne, J. A. 2018; 3 (2)

  View details for DOI 10.1038/natrevmats.2017.80

  View details for Web of Science ID 000426604800006

• Broadband and wide-angle nonreciprocity with a non-Hermitian metamaterial PHYSICAL REVIEW B Barton, D. R., Alaeian, H., Lawrence, M., Dionne, J. 2018; 97 (4)

  View details for DOI 10.1103/PhysRevB.97.045432

  View details for Web of Science ID 000423433700008

• Bright, Mechanosensitive Upconversion with Cubic-Phase Heteroepitaxial Core-Shell Nanoparticles. Nano letters Lay, A. n., Siefe, C. n., Fischer, S. n., Mehlenbacher, R. D., Ke, F. n., Mao, W. L., Alivisatos, A. P., Goodman, M. B., Dionne, J. A. 2018

  Abstract

  Lanthanide-doped nanoparticles are an emerging class of optical sensors, exhibiting sharp emission peaks, high signal-to-noise ratio, photostability, and a ratiometric color response to stress. The same centrosymmetric crystal field environment that allows for high mechanosensitivity in the cubic-phase (α), however, contributes to low upconversion quantum yield (UCQY). In this work, we engineer brighter mechanosensitive upconverters using a core-shell geometry. Sub-25 nm α-NaYF4:Yb,Er cores are shelled with an optically inert surface passivation layer of ∼4.5 nm thickness. Using different shell materials, including NaGdF4, NaYF4, and NaLuF4, we study how compressive to tensile strain influences the nanoparticles' imaging and sensing properties. All core-shell nanoparticles exhibit enhanced UCQY, up to 0.14% at 150 W/cm2, which rivals the efficiency of unshelled hexagonal-phase (β) nanoparticles. Additionally, strain at the core-shell interface can tune mechanosensitivity. In particular, the compressive Gd shell results in the largest color response from yellow-green to orange or, quantitatively, a change in the red to green ratio of 12.2 ± 1.2% per GPa. For all samples, the ratiometric readouts are consistent over three pressure cycles from ambient to 5 GPa. Therefore, heteroepitaxial shelling significantly improves signal brightness without compromising the core's mechano-sensing capabilities and further, promotes core-shell cubic-phase nanoparticles as upcoming in vivo and in situ optical sensors.

  View details for PubMedID 29927609

• In-situ visualization of solute-driven phase coexistence within individual nanorods. Nature communications Hayee, F. n., Narayan, T. C., Nadkarni, N. n., Baldi, A. n., Koh, A. L., Bazant, M. Z., Sinclair, R. n., Dionne, J. A. 2018; 9 (1): 1775

  Abstract

  Nanorods are promising components of energy and information storage devices that rely on solute-driven phase transformations, due to their large surface-to-volume ratio and ability to accommodate strain. Here we investigate the hydrogen-induced phase transition in individual penta-twinned palladium nanorods of varying aspect ratios with ~3 nm spatial resolution to understand the correlation between nanorod structure and thermodynamics. We find that the hydrogenated phase preferentially nucleates at the rod tips, progressing along the length of the nanorods with increasing hydrogen pressure. While nucleation pressure is nearly constant for all lengths, the number of phase boundaries is length-dependent, with stable phase coexistence always occurring for rods longer than 55 nm. Moreover, such coexistence occurs within individual crystallites of the nanorods and is accompanied by defect formation, as supported by in situ electron microscopy and elastic energy calculations. These results highlight the effect of particle shape and dimension on thermodynamics, informing nanorod design for improved device cyclability.

  View details for PubMedID 29720644

  View details for PubMedCentralID PMC5932065

• Nanoscopic control and quantification of enantioselective optical forces. Nature nanotechnology Zhao, Y., Saleh, A. A., van de Haar, M. A., Baum, B., Briggs, J. A., Lay, A., Reyes-Becerra, O. A., Dionne, J. A. 2017; 12 (11): 1055-1059

  Abstract

  Circularly polarized light (CPL) exerts a force of different magnitude on left- and right-handed enantiomers, an effect that could be exploited for chiral resolution of chemical compounds as well as controlled assembly of chiral nanostructures. However, enantioselective optical forces are challenging to control and quantify because their magnitude is extremely small (sub-piconewton) and varies in space with sub-micrometre resolution. Here, we report a technique to both strengthen and visualize these forces, using a chiral atomic force microscope probe coupled to a plasmonic optical tweezer. Illumination of the plasmonic tweezer with CPL exerts a force on the microscope tip that depends on the handedness of the light and the tip. In particular, for a left-handed chiral tip, transverse forces are attractive with left-CPL and repulsive with right-CPL. Additionally, total force differences between opposite-handed specimens exceed 10 pN. The microscope tip can map chiral forces with 2 nm lateral resolution, revealing a distinct spatial distribution of forces for each handedness.

  View details for DOI 10.1038/nnano.2017.180

  View details for PubMedID 28945237

  View details for PubMedCentralID PMC5679370

• Hot-Carrier-Mediated Photon Upconversion in Metal-Decorated Quantum Wells. Nano letters Naik, G. V., Welch, A. J., Briggs, J. A., Solomon, M. L., Dionne, J. A. 2017; 17 (8): 4583-4587

  Abstract

  Manipulating the frequency of electromagnetic waves forms the core of many modern technologies, ranging from imaging and spectroscopy to radio and optical communication. The process of converting photons from higher to lower energy is easily accomplished and technologically widespread. However, upconversion, which is the process of converting lower-energy photons into higher-energy photons, is still a growing field of study with nascent applications and burgeoning interest. Here, we experimentally demonstrate a new photon upconversion technique mediated by hot carriers in plasmonic nanostructures. Hot holes and hot electrons generated via plasmon decay in illuminated metal nanoparticles are injected into an adjacent semiconductor quantum well where they radiatively recombine to emit higher-energy photons. Using GaN/InGaN quantum wells decorated with gold and silver nanoparticles, we show photon upconversion from 2.4 to 2.8 eV. The process scales linearly with illumination power and enables both geometry- and polarization-based tunability. The conversion of plasmonic losses into upconverted optical emission has the potential to impact bioimaging, on-chip wavelength conversion, and high-efficiency photovoltaics.

  View details for DOI 10.1021/acs.nanolett.7b00900

  View details for PubMedID 28661675

• Subwavelength-scale plasmon waveguides Surface Plasmon Photonics Atwater, H., Dionne, J., Sweatlock, L. edited by Brongersma, M., L., Kik, P., G. Dordrecht, NL: Springer. : 87–104
• Temperature-dependent optical properties of titanium nitride APPLIED PHYSICS LETTERS Briggs, J. A., Naik, G. V., Zhao, Y., Petach, T. A., Sahasrabuddhe, K., Goldhaber-Gordon, D., Melosh, N. A., Dionne, J. A. 2017; 110 (10)

  View details for DOI 10.1063/1.4977840

  View details for Web of Science ID 000397871800011

• Enhancing Enantioselective Absorption Using Dielectric Nanospheres ACS PHOTONICS Ho, C., Garcia-Etxarri, A., Zhao, Y., Dionne, J. 2017; 4 (2): 197-203

  View details for DOI 10.1021/acsphotonics.6b00701

  View details for Web of Science ID 000394483500001

• Direct visualization of hydrogen absorption dynamics in individual palladium nanoparticles NATURE COMMUNICATIONS Narayan, T. C., Hayee, F., Baldi, A., Koh, A. L., Sinclair, R., Dionne, J. A. 2017; 8

  View details for DOI 10.1038/ncomms14020

  View details for Web of Science ID 000391869800001

• Direct visualization of hydrogen absorption dynamics in individual palladium nanoparticles. Nature communications Narayan, T. C., Hayee, F., Baldi, A., Leen Koh, A., Sinclair, R., Dionne, J. A. 2017; 8: 14020-?

  Abstract

  Many energy storage materials undergo large volume changes during charging and discharging. The resulting stresses often lead to defect formation in the bulk, but less so in nanosized systems. Here, we capture in real time the mechanism of one such transformation-the hydrogenation of single-crystalline palladium nanocubes from 15 to 80 nm-to better understand the reason for this durability. First, using environmental scanning transmission electron microscopy, we monitor the hydrogen absorption process in real time with 3 nm resolution. Then, using dark-field imaging, we structurally examine the reaction intermediates with 1 nm resolution. The reaction proceeds through nucleation and growth of the new phase in corners of the nanocubes. As the hydrogenated phase propagates across the particles, portions of the lattice misorient by 1.5%, diminishing crystal quality. Once transformed, all the particles explored return to a pristine state. The nanoparticles' ability to remove crystallographic imperfections renders them more durable than their bulk counterparts.

  View details for DOI 10.1038/ncomms14020

  View details for PubMedID 28091597

  View details for PubMedCentralID PMC5241819

• Nanoscopic control and quantification of enantioselective optical forces Nature Nanotechnology Zhao, Y., Saleh, A., van de Haar, M., Baum, B., Briggs, J. A., Lay, A., Reyes-Becerra, O. A., Dionne, J. A. 2017: 1055–59

  Abstract

  Circularly polarized light (CPL) exerts a force of different magnitude on left- and right-handed enantiomers, an effect that could be exploited for chiral resolution of chemical compounds as well as controlled assembly of chiral nanostructures. However, enantioselective optical forces are challenging to control and quantify because their magnitude is extremely small (sub-piconewton) and varies in space with sub-micrometre resolution. Here, we report a technique to both strengthen and visualize these forces, using a chiral atomic force microscope probe coupled to a plasmonic optical tweezer. Illumination of the plasmonic tweezer with CPL exerts a force on the microscope tip that depends on the handedness of the light and the tip. In particular, for a left-handed chiral tip, transverse forces are attractive with left-CPL and repulsive with right-CPL. Additionally, total force differences between opposite-handed specimens exceed 10 pN. The microscope tip can map chiral forces with 2 nm lateral resolution, revealing a distinct spatial distribution of forces for each handedness.

  View details for DOI 10.1038/nnano.2017.180

  View details for PubMedCentralID PMC5679370

• Grating-flanked plasmonic coaxial apertures for efficient fiber optical tweezers. Optics express Saleh, A. A., Sheikhoelislami, S., Gastelum, S., Dionne, J. A. 2016; 24 (18): 20593-20603

  Abstract

  Subwavelength plasmonic apertures have been foundational for direct optical manipulation of nanoscale specimens including sub-100 nm polymeric beads, metallic nanoparticles and proteins. While most plasmonic traps result in two-dimensional localization, three-dimensional manipulation has been demonstrated by integrating a plasmonic aperture on an optical fiber tip. However, such 3D traps are usually inefficient since the optical mode of the fiber and the subwavelength aperture only weakly couple. In this paper we design more efficient optical-fiber-based plasmonic tweezers combining a coaxial plasmonic aperture with a plasmonic grating coupler at the fiber tip facet. Using full-field finite difference time domain analysis, we optimize the grating design for both gold and silver fiber-based coaxial tweezers such that the optical transmission through the apertures is maximized. With the optimized grating, we show that the maximum transmission efficiency increases from 2.5% to 19.6% and from 1.48% to 16.7% for the gold and silver structures respectively. To evaluate their performance as optical tweezers, we calculate the optical forces and the corresponding trapping potential on dielectric particles interacting with the apertures. We demonstrate that the enahncement in the transmission translates into an equivalent increase in the optical forces. Consequently, the optical power required to achieve stable optical trapping is significantly reduced allowing for efficient localization and 3D manipulation of sub-30 nm dielectric particles.

  View details for DOI 10.1364/OE.24.020593

  View details for PubMedID 27607663

• Enhancing Quantum Yield via Local Symmetry Distortion in Lanthanide-Based Upconverting Nanoparticles ACS PHOTONICS Wisser, M. D., Fischer, S., Maurer, P. C., Bronstein, N. D., Chu, S., Alivisatos, A. P., Salleo, A., Dionne, J. A. 2016; 3 (8): 1523-1530

  View details for DOI 10.1021/acsphotonics.6b00166

  View details for Web of Science ID 000381717600023

• Reconstructing solute-induced phase transformations within individual nanocrystals NATURE MATERIALS Narayan, T. C., Baldi, A., Koh, A. L., Sinclair, R., Dionne, J. A. 2016; 15 (7): 768-?

  Abstract

  Strain and defects can significantly impact the performance of functional nanomaterials. This effect is well exemplified by energy storage systems, in which structural changes such as volume expansion and defect generation govern the phase transformations associated with charging and discharging. The rational design of next-generation storage materials therefore depends crucially on understanding the correlation between the structure of individual nanoparticles and their solute uptake and release. Here, we experimentally reconstruct the spatial distribution of hydride phases within individual palladium nanocrystals during hydrogen absorption, using a combination of electron spectroscopy, dark-field imaging, and electron diffraction in an environmental transmission electron microscope. We show that single-crystalline cubes and pyramids exhibit a uniform hydrogen distribution at equilibrium, whereas multiply twinned icosahedra exclude hydrogen from regions of high compressive strains. Our technique offers unprecedented insight into nanoscale phase transformations in reactive environments and can be extended to a variety of functional nanomaterials.

  View details for DOI 10.1038/NMAT4620

  View details for Web of Science ID 000378347800027

  View details for PubMedID 27088234

• Roadmap on optical energy conversion JOURNAL OF OPTICS Boriskina, S. V., Green, M. A., Catchpole, K., Yablonovitch, E., Beard, M. C., Okada, Y., Lany, S., Gershon, T., Zakutayev, A., Tahersima, M. H., Sorger, V. J., Naughton, M. J., Kempa, K., Dagenais, M., Yao, Y., Xu, L., Sheng, X., Bronstein, N. D., Rogers, J. A., Alivisatos, A. P., Nuzzo, R. G., Gordon, J. M., Wu, D. M., Wisser, M. D., Salleo, A., Dionne, J., Bermel, P., Greffet, J., Celanovic, I., Soljacic, M., Manor, A., Rotschild, C., Raman, A., Zhu, L., Fan, S., Chen, G. 2016; 18 (7)

  View details for DOI 10.1088/2040-8978/18/7/073004

  View details for Web of Science ID 000383908800007

• Towards nanoscale multiplexing with parity-time-symmetric plasmonic coaxial waveguides PHYSICAL REVIEW B Alaeian, H., Baum, B., Jankovic, V., Lawrence, M., Dionne, J. A. 2016; 93 (20)

  View details for DOI 10.1103/PhysRevB.93.205439

  View details for Web of Science ID 000376639000005

• Enantioselective Optical Trapping of Chiral Nanoparticles with Plasmonic Tweezers ACS PHOTONICS Zhao, Y., Saleh, A. A., Dionne, J. A. 2016; 3 (3): 304-309

  View details for DOI 10.1021/acsphotonics.5b00574

  View details for Web of Science ID 000372479500001

• Fully CMOS-compatible titanium nitride nanoantennas APPLIED PHYSICS LETTERS Briggs, J. A., Naik, G. V., Petach, T. A., Baum, B. K., Goldhaber-Gordon, D., Dionne, J. A. 2016; 108 (5)

  View details for DOI 10.1063/1.4941413

  View details for Web of Science ID 000373055700010

• Evolution of Plasmonic Metamolecule Modes in the Quantum Tunneling Regime. ACS nano Scholl, J. A., Garcia-Etxarri, A., Aguirregabiria, G., Esteban, R., Narayan, T. C., Koh, A. L., Aizpurua, J., Dionne, J. A. 2016; 10 (1): 1346-1354

  Abstract

  Plasmonic multinanoparticle systems exhibit collective electric and magnetic resonances that are fundamental for the development of state-of-the-art optical nanoantennas, metamaterials, and surface-enhanced spectroscopy substrates. While electric dipolar modes have been investigated in both the classical and quantum realm, little attention has been given to magnetic and other "dark" modes at the smallest dimensions. Here, we study the collective electric, magnetic, and dark modes of colloidally synthesized silver nanosphere trimers with varying interparticle separation using scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). This technique enables direct visualization and spatially selective excitation of individual trimers, as well as manipulation of the interparticle distance into the subnanometer regime with the electron beam. Our experiments reveal that bonding electric and magnetic modes are significantly impacted by quantum effects, exhibiting a relative blueshift and reduced EELS amplitude compared to classical predictions. In contrast, the trimer's electric dark mode is not affected by quantum tunneling for even Ångström-scale interparticle separations. We employ a quantum-corrected model to simulate the effect of electron tunneling in the trimer which shows excellent agreement with experimental results. This understanding of classical and quantum-influenced hybridized modes may impact the development of future quantum plasmonic materials and devices, including Fano-like molecular sensors and quantum metamaterials.

  View details for DOI 10.1021/acsnano.5b06738

  View details for PubMedID 26639023

• Plasmonics feature issue: publisher's note OPTICAL MATERIALS EXPRESS Boltasseva, A., Dionne, J. 2015; 5 (12): 2978-2978

  View details for DOI 10.1364/OME.5.002978

  View details for Web of Science ID 000366045900027

• Localized fields, global impact: Industrial applications of resonant plasmonic materials MRS BULLETIN Dionne, J. A., Baldi, A., Baum, B., Ho, C., Jankovic, V., Naik, G. V., Narayan, T., Scholl, J. A., Zhao, Y. 2015; 40 (12): 1138-1145

  View details for DOI 10.1557/mrs.2015.233

  View details for Web of Science ID 000365744400014

• Feature issue introduction: plasmonics OPTICAL MATERIALS EXPRESS Boltasseva, A., Dionne, J. 2015; 5 (11): 2698-2701

  View details for DOI 10.1364/OME.5.002698

  View details for Web of Science ID 000364467700034

• Photon upconversion with hot carriers in plasmonic systems APPLIED PHYSICS LETTERS Naik, G. V., Dionne, J. A. 2015; 107 (13)

  View details for DOI 10.1063/1.4932127

  View details for Web of Science ID 000362575600051

• Polymer lattices as mechanically tunable 3-dimensional photonic crystals operating in the infrared APPLIED PHYSICS LETTERS Chernow, V. F., Alaeian, H., Dionne, J. A., Greer, J. R. 2015; 107 (10)

  View details for DOI 10.1063/1.4930819

  View details for Web of Science ID 000361640200018

• Controlling electric, magnetic, and chiral dipolar emission with PT-symmetric potentials PHYSICAL REVIEW B Alaeian, H., Dionne, J. A. 2015; 91 (24)

  View details for DOI 10.1103/PhysRevB.91.245108

  View details for Web of Science ID 000355647400003

• Nanoscale optical tomography with cathodoluminescence spectroscopy NATURE NANOTECHNOLOGY Atre, A. C., Brenny, B. J., Coenen, T., Garcia-Etxarri, A., Polman, A., Dionne, J. A. 2015; 10 (5): 429-436

  Abstract

  Tomography has enabled the characterization of the Earth's interior, visualization of the inner workings of the human brain, and three-dimensional reconstruction of matter at the atomic scale. However, tomographic techniques that rely on optical excitation or detection are generally limited in their resolution by diffraction. Here, we introduce a tomographic technique--cathodoluminescence spectroscopic tomography--to probe optical properties in three dimensions with nanometre-scale spatial and spectral resolution. We first obtain two-dimensional cathodoluminescence maps of a three-dimensional nanostructure at various orientations. We then use the method of filtered back-projection to reconstruct the cathodoluminescence intensity at each wavelength. The resulting tomograms allow us to locate regions of efficient cathodoluminescence in three dimensions across visible and near-infrared wavelengths, with contributions from material luminescence and radiative decay of electromagnetic eigenmodes. The experimental signal can be further correlated with the radiative local density of optical states in particular regions of the reconstruction. We demonstrate how cathodoluminescence tomography can be used to achieve nanoscale three-dimensional visualization of light-matter interactions by reconstructing a three-dimensional metal-dielectric nanoresonator.

  View details for DOI 10.1038/NNANO.2015.39

  View details for Web of Science ID 000354094900012

  View details for PubMedID 25849788

• Strain-induced modification of optical selection rules in lanthanide-based upconverting nanoparticles. Nano letters Wisser, M. D., Chea, M., Lin, Y., Wu, D. M., Mao, W. L., Salleo, A., Dionne, J. A. 2015; 15 (3): 1891-1897

  Abstract

  NaYF4:Yb(3+),Er(3+) nanoparticle upconverters are hindered by low quantum efficiencies arising in large part from the parity-forbidden nature of their optical transitions and the nonoptimal spatial separations between lanthanide ions. Here, we use pressure-induced lattice distortion to systematically modify both parameters. Although hexagonal-phase nanoparticles exhibit a monotonic decrease in upconversion emission, cubic-phase particles experience a nearly 2-fold increase in efficiency. In-situ X-ray diffraction indicates that these emission changes require only a 1% reduction in lattice constant. Our work highlights the intricate relationship between upconversion efficiency and lattice geometry and provides a promising approach to modifying the quantum efficiency of any lanthanide upconverter.

  View details for DOI 10.1021/nl504738k

  View details for PubMedID 25647523

• Lights, nano, action! New plasmonic materials and methods to probe nanoscale phenomena MRS BULLETIN Dionne, J. A. 2015; 40 (3): 264-270

  View details for DOI 10.1557/mrs.2015.31

  View details for Web of Science ID 000351157100021

• A parity-time symmetric coherent plasmonic absorber-amplifier JOURNAL OF APPLIED PHYSICS Baum, B., Alaeian, H., Dionne, J. 2015; 117 (6)

  View details for DOI 10.1063/1.4907871

  View details for Web of Science ID 000349846300006

• Probing Complex Reflection Coefficients in One-Dimensional Surface Plasmon Polariton Waveguides and Cavities Using STEM EELS. Nano letters Schoen, D. T., Atre, A. C., García-Etxarri, A., Dionne, J. A., Brongersma, M. L. 2015; 15 (1): 120-126

  Abstract

  The resonant properties of a plasmonic cavity are determined by the size of the cavity, the surface plasmon polariton (SPP) dispersion relationship, and the complex reflection coefficients of the cavity boundaries. In small wavelength-scale cavities, the phase propagation due to reflections from the cavity walls is of a similar magnitude to propagation due to traversing the cavity. Until now, this reflection phase has been inferred from measurements of the resonant frequencies of a cavity of known dispersion and length. In this work, we present a method for measuring the complex reflection coefficients of a truncation in a 1D surface plasmon waveguide using electron energy loss spectroscopy in the scanning transmission electron microscope (STEM EELS) and show that this insight can be used to engineer custom cavities with engineered reflecting boundaries, whose resonant wavelengths and internal mode density profiles can be analytically predicted given knowledge of the cavity dimensions and complex reflection coefficients of the boundaries.

  View details for DOI 10.1021/nl503179j

  View details for PubMedID 25545292

• Upconversion for Enhanced Photovoltaics 3rd Physics of Sustainable Energy (PSE) Conference Briggs, J. A., Wu, D. M., Atre, A. C., Garcia-Etxarri, A., Dionne, J. A. AMER INST PHYSICS. 2015: 33–43

  View details for DOI 10.1063/1.4916166

  View details for Web of Science ID 000354881700003

• Strain-induced modification of optical selection rules in lanthanide-based upconverting nanoparticles Nano Letters Wisser, M., Chea, M., Lin, Y., Wu, D., Mao, W. L., Salleo, A., Dionne, J. 2015: 1891–97

  Abstract

  NaYF4:Yb(3+),Er(3+) nanoparticle upconverters are hindered by low quantum efficiencies arising in large part from the parity-forbidden nature of their optical transitions and the nonoptimal spatial separations between lanthanide ions. Here, we use pressure-induced lattice distortion to systematically modify both parameters. Although hexagonal-phase nanoparticles exhibit a monotonic decrease in upconversion emission, cubic-phase particles experience a nearly 2-fold increase in efficiency. In-situ X-ray diffraction indicates that these emission changes require only a 1% reduction in lattice constant. Our work highlights the intricate relationship between upconversion efficiency and lattice geometry and provides a promising approach to modifying the quantum efficiency of any lanthanide upconverter.

  View details for DOI 10.1021/nl504738k

• In situ detection of hydrogen-induced phase transitions in individual palladium nanocrystals NATURE MATERIALS Baldi, A., Narayan, T. C., Koh, A. L., Dionne, J. A. 2014; 13 (12): 1143-1148

  View details for DOI 10.1038/NMAT4086

  View details for Web of Science ID 000345432200018

• In situ detection of hydrogen-induced phase transitions in individual palladium nanocrystals. Nature materials Baldi, A., Narayan, T. C., Koh, A. L., Dionne, J. A. 2014; 13 (12): 1143-1148

  Abstract

  Many energy- and information-storage processes rely on phase changes of nanomaterials in reactive environments. Compared to their bulk counterparts, nanostructured materials seem to exhibit faster charging and discharging kinetics, extended life cycles, and size-tunable thermodynamics. However, in ensemble studies of these materials, it is often difficult to discriminate between intrinsic size-dependent properties and effects due to sample size and shape dispersity. Here, we detect the phase transitions of individual palladium nanocrystals during hydrogen absorption and desorption, using in situ electron energy-loss spectroscopy in an environmental transmission electron microscope. In contrast to ensemble measurements, we find that palladium nanocrystals undergo sharp transitions between the α and β phases, and that surface effects dictate the size dependence of the hydrogen absorption pressures. Our results provide a general framework for monitoring phase transitions in individual nanocrystals in a reactive environment and highlight the importance of single-particle approaches for the characterization of nanostructured materials.

  View details for DOI 10.1038/nmat4086

  View details for PubMedID 25194700

• Plasmon-Enhanced Upconversion JOURNAL OF PHYSICAL CHEMISTRY LETTERS Wu, D. M., Garcia-Etxarri, A., Salleo, A., Dionne, J. A. 2014; 5 (22): 4020-4031

  Abstract

  Upconversion, the conversion of photons from lower to higher energies, is a process that promises applications ranging from high-efficiency photovoltaic and photocatalytic cells to background-free bioimaging and therapeutic probes. Existing upconverting materials, however, remain too inefficient for viable implementation. In this Perspective, we describe the significant improvements in upconversion efficiency that can be achieved using plasmon resonances. As collective oscillations of free electrons, plasmon resonances can be used to enhance both the incident electromagnetic field intensity and the radiative emission rates. To date, this approach has shown upconversion enhancements up to 450×. We discuss both theoretical underpinnings and experimental demonstrations of plasmon-enhanced upconversion, examining the roles of upconverter quantum yield, plasmonic geometry, and plasmon spectral overlap. We also discuss nonoptical consequences of including metal nanostructures near upconverting emitters. The rapidly expanding field of plasmon-enhanced upconversion provides novel fundamental insight into nanoscale light-matter interactions while improving prospects for technological relevance.

  View details for DOI 10.1021/jz5019042

  View details for Web of Science ID 000345542900014

• Plasmon-Enhanced Upconversion. journal of physical chemistry letters Wu, D. M., García-Etxarri, A., Salleo, A., Dionne, J. A. 2014; 5 (22): 4020-4031

  Abstract

  Upconversion, the conversion of photons from lower to higher energies, is a process that promises applications ranging from high-efficiency photovoltaic and photocatalytic cells to background-free bioimaging and therapeutic probes. Existing upconverting materials, however, remain too inefficient for viable implementation. In this Perspective, we describe the significant improvements in upconversion efficiency that can be achieved using plasmon resonances. As collective oscillations of free electrons, plasmon resonances can be used to enhance both the incident electromagnetic field intensity and the radiative emission rates. To date, this approach has shown upconversion enhancements up to 450×. We discuss both theoretical underpinnings and experimental demonstrations of plasmon-enhanced upconversion, examining the roles of upconverter quantum yield, plasmonic geometry, and plasmon spectral overlap. We also discuss nonoptical consequences of including metal nanostructures near upconverting emitters. The rapidly expanding field of plasmon-enhanced upconversion provides novel fundamental insight into nanoscale light-matter interactions while improving prospects for technological relevance.

  View details for DOI 10.1021/jz5019042

  View details for PubMedID 26276488

• Parity-time-symmetric plasmonic metamaterials PHYSICAL REVIEW A Alaeian, H., Dionne, J. A. 2014; 89 (3)

  View details for DOI 10.1103/PhysRevA.89.033829

  View details for Web of Science ID 000333184400011

• Non-Hermitian nanophotonic and plasmonic waveguides PHYSICAL REVIEW B Alaeian, H., Dionne, J. A. 2014; 89 (7)

  View details for DOI 10.1103/PhysRevB.89.075136

  View details for Web of Science ID 000332419900002

• A metafluid exhibiting strong optical magnetism. Nano letters Sheikholeslami, S. N., Alaeian, H., Koh, A. L., Dionne, J. A. 2013; 13 (9): 4137-4141

  Abstract

  Advances in the field of metamaterials have enabled unprecedented control of light-matter interactions. Metamaterial constituents support high-frequency electric and magnetic dipoles, which can be used as building blocks for new materials capable of negative refraction, electromagnetic cloaking, strong visible-frequency circular dichroism, and enhancing magnetic or chiral transitions in ions and molecules. While all metamaterials to date have existed in the solid-state, considerable interest has emerged in designing a colloidal metamaterial or "metafluid". Such metafluids would combine the advantages of solution-based processing with facile integration into conventional optical components. Here we demonstrate the colloidal synthesis of an isotropic metafluid that exhibits a strong magnetic response at visible frequencies. Protein-antibody interactions are used to direct the solution-phase self-assembly of discrete metamolecules comprised of silver nanoparticles tightly packed around a single dielectric core. The electric and magnetic response of individual metamolecules and the bulk metamaterial solution are directly probed with optical scattering and spectroscopy. Effective medium calculations indicate that the bulk metamaterial exhibits a negative effective permeability and a negative refractive index at modest fill factors. This metafluid can be synthesized in large-quantity and high-quality and may accelerate development of advanced nanophotonic and metamaterial devices.

  View details for DOI 10.1021/nl401642z

  View details for PubMedID 23919764

• Surface-enhanced circular dichroism spectroscopy mediated by nonchiral nanoantennas PHYSICAL REVIEW B Garcia-Etxarri, A., Dionne, J. A. 2013; 87 (23)

  View details for DOI 10.1103/PhysRevB.87.235409

  View details for Web of Science ID 000320164900008

• NANOPLASMONICS Plasmons rock in metal bands NATURE MATERIALS Dionne, J. A. 2013; 12 (5): 380-381

  View details for DOI 10.1038/nmat3607

  View details for Web of Science ID 000317954800003

  View details for PubMedID 23503013

• A Broadband Negative Index Metamaterial at Optical Frequencies ADVANCED OPTICAL MATERIALS Atre, A. C., Garcia-Etxarri, A., Alaeian, H., Dionne, J. A. 2013; 1 (4): 327-333

  View details for DOI 10.1002/adom.201200022

  View details for Web of Science ID 000320998600009

• Narrow-bandwidth solar upconversion: Case studies of existing systems and generalized fundamental limits JOURNAL OF APPLIED PHYSICS Briggs, J. A., Atre, A. C., Dionne, J. A. 2013; 113 (12)

  View details for DOI 10.1063/1.4796092

  View details for Web of Science ID 000316967800061

• Observation of Quantum Tunneling between Two Plasmonic Nanoparticles NANO LETTERS Scholl, J. A., Garcia-Etxarri, A., Koh, A. L., Dionne, J. A. 2013; 13 (2): 564-569

  Abstract

  The plasmon resonances of two closely spaced metallic particles have enabled applications including single-molecule sensing and spectroscopy, novel nanoantennas, molecular rulers, and nonlinear optical devices. In a classical electrodynamic context, the strength of such dimer plasmon resonances increases monotonically as the particle gap size decreases. In contrast, a quantum mechanical framework predicts that electron tunneling will strongly diminish the dimer plasmon strength for subnanometer-scale separations. Here, we directly observe the plasmon resonances of coupled metallic nanoparticles as their gap size is reduced to atomic dimensions. Using the electron beam of a scanning transmission electron microscope (STEM), we manipulate pairs of ~10-nm-diameter spherical silver nanoparticles on a substrate, controlling their convergence and eventual coalescence into a single nanosphere. We simultaneously employ electron energy-loss spectroscopy (EELS) to observe the dynamic plasmonic properties of these dimers before and after particle contact. As separations are reduced from 7 nm, the dominant dipolar peak exhibits a redshift consistent with classical calculations. However, gaps smaller than ~0.5 nm cause this mode to exhibit a reduced intensity consistent with quantum theories that incorporate electron tunneling. As the particles overlap, the bonding dipolar mode disappears and is replaced by a dipolar charge transfer mode. Our dynamic imaging, manipulation, and spectroscopy of nanostructures enables the first full spectral mapping of dimer plasmon evolution and may provide new avenues for in situ nanoassembly and analysis in the quantum regime.

  View details for DOI 10.1021/nl304078v

  View details for Web of Science ID 000315079500040

  View details for PubMedID 23245286

• Plasmons rock in metal bands Nature Materials 12 Dionne, J. 2013: 380
• Toward Efficient Optical Trapping of Sub-10-nm Particles with Coaxial Plasmonic Apertures NANO LETTERS Saleh, A. A., Dionne, J. A. 2012; 12 (11): 5581-5586

  Abstract

  Optical trapping using focused laser beams has emerged as a powerful tool in the biological and physical sciences. However, scaling this technique to nanosized objects remains challenging due to the diffraction limit of light and the high power levels required for nanoscale trapping. In this paper, we propose plasmonic coaxial apertures as low-power optical traps for nanosized specimens. The illumination of a coaxial aperture with a linearly polarized plane wave generates a dual optical trapping potential well. We theoretically show that this potential can stably trap dielectric particles smaller than 10 nm in diameter while keeping the trapping power level below 20 mW. By tapering the thickness of the coaxial dielectric channel, trapping can be extended to sub-2-nm particles. The proposed structures may enable optical trapping and manipulation of dielectric particles ranging from single proteins to small molecules with sizes previously inaccessible.

  View details for DOI 10.1021/nl302627c

  View details for Web of Science ID 000311244400023

  View details for PubMedID 23035765

• Plasmonics: Metal-worthy methods and materials in nanophotonics MRS BULLETIN Dionne, J. A., Atwater, H. A. 2012; 37 (8): 717-724

  View details for DOI 10.1557/mrs.2012.171

  View details for Web of Science ID 000308083700008

• Plasmon nanoparticle superlattices as optical-frequency magnetic metamaterials OPTICS EXPRESS Alaeian, H., Dionne, J. A. 2012; 20 (14): 15781-15796

  Abstract

  Nanocrystal superlattices have emerged as a new platform for bottom-up metamaterial design, but their optical properties are largely unknown. Here, we investigate their emergent optical properties using a generalized semi-analytic, full-field solver based on rigorous coupled wave analysis. Attention is given to superlattices composed of noble metal and dielectric nanoparticles in unary and binary arrays. By varying the nanoparticle size, shape, separation, and lattice geometry, we demonstrate the broad tunability of superlattice optical properties. Superlattices composed of spherical or octahedral nanoparticles in cubic and AB(2) arrays exhibit magnetic permeabilities tunable between 0.2 and 1.7, despite having non-magnetic constituents. The retrieved optical parameters are nearly polarization and angle-independent over a broad range of incident angles. Accordingly, nanocrystal superlattices behave as isotropic bulk metamaterials. Their tunable permittivities, permeabilities, and emergent magnetism may enable new, bottom-up metamaterials and negative index materials at visible frequencies.

  View details for Web of Science ID 000306176100110

  View details for PubMedID 22772268

• Opportunities and Challenges of Using Plasmonic Components in Nanophotonic Architectures IEEE JOURNAL ON EMERGING AND SELECTED TOPICS IN CIRCUITS AND SYSTEMS Wassel, H. M., Dai, D., Tiwari, M., Valamehr, J. K., Theogarajan, L., Dionne, J., Chong, F. T., Sherwood, T. 2012; 2 (2): 154-168

  View details for DOI 10.1109/JETCAS.2012.2193934

  View details for Web of Science ID 000208972800004

• Quantum plasmon resonances of individual metallic nanoparticles NATURE Scholl, J. A., Koh, A. L., Dionne, J. A. 2012; 483 (7390): 421-U68

  Abstract

  The plasmon resonances of metallic nanoparticles have received considerable attention for their applications in nanophotonics, biology, sensing, spectroscopy and solar energy harvesting. Although thoroughly characterized for spheres larger than ten nanometres in diameter, the plasmonic properties of particles in the quantum size regime have been historically difficult to describe owing to weak optical scattering, metal-ligand interactions, and inhomogeneity in ensemble measurements. Such difficulties have precluded probing and controlling the plasmonic properties of quantum-sized particles in many natural and engineered processes, notably catalysis. Here we investigate the plasmon resonances of individual ligand-free silver nanoparticles using aberration-corrected transmission electron microscope (TEM) imaging and monochromated scanning TEM electron energy-loss spectroscopy (EELS). This technique allows direct correlation between a particle's geometry and its plasmon resonance. As the nanoparticle diameter decreases from 20 nanometres to less than two nanometres, the plasmon resonance shifts to higher energy by 0.5 electronvolts, a substantial deviation from classical predictions. We present an analytical quantum mechanical model that describes this shift due to a change in particle permittivity. Our results highlight the quantum plasmonic properties of small metallic nanospheres, with direct application to understanding and exploiting catalytically active and biologically relevant nanoparticles.

  View details for DOI 10.1038/nature10904

  View details for Web of Science ID 000301771200034

  View details for PubMedID 22437611

• Toward high-efficiency solar upconversion with plasmonic nanostructures JOURNAL OF OPTICS Atre, A. C., Garcia-Etxarri, A., Alaeian, H., Dionne, J. A. 2012; 14 (2)

  View details for DOI 10.1088/2040-8978/14/2/024008

  View details for Web of Science ID 000300303400009

• Optimized light absorption in Si wire array solar cells JOURNAL OF OPTICS Alaeian, H., Atre, A. C., Dionne, J. A. 2012; 14 (2)

  View details for DOI 10.1088/2040-8978/14/2/024006

  View details for Web of Science ID 000300303400007

• Waveguides with a silver lining: Low threshold gain and giant modal gain in active cylindrical and coaxial plasmonic devices PHYSICAL REVIEW B Saleh, A. A., Dionne, J. A. 2012; 85 (4)

  View details for DOI 10.1103/PhysRevB.85.045407

  View details for Web of Science ID 000298865200008

• Mirror, Mirror Physics 5 Dionne, J. 2012: 38
• Controlling the Interplay of Electric and Magnetic Modes via Fano-like Plasmon Resonances NANO LETTERS Sheikholeslami, S. N., Garcia-Etxarri, A., Dionne, J. A. 2011; 11 (9): 3927-3934

  Abstract

  Assemblies of strongly coupled plasmonic nanoparticles can support highly tunable electric and magnetic resonances in the visible spectrum. In this Letter, we theoretically demonstrate Fano-like interference effects between the fields radiated by the electric and magnetic modes of symmetric nanoparticle trimers. Breaking the symmetry of the trimer system leads to a strong interaction between the modes. The near and far-field electromagnetic properties of the broken symmetry trimer are tunable across a large spectral range. We exploit this Fano-like effect to demonstrate spatial and temporal control of the localized electromagnetic hotspots in the plasmonic trimer.

  View details for DOI 10.1021/nl202143j

  View details for Web of Science ID 000294790200072

  View details for PubMedID 21819059

• Realistic upconverter-enhanced solar cells with non-ideal absorption and recombination efficiencies JOURNAL OF APPLIED PHYSICS Atre, A. C., Dionne, J. A. 2011; 110 (3)

  View details for DOI 10.1063/1.3610522

  View details for Web of Science ID 000293956600144

• Giving photovoltaics the green light: Plasmon-enhanced upconversion for broadband solar absorption IEEE Photonics Conference (PHO) Dionne, J. A., Atre, A., Alaeian, H., Garcia, A. IEEE. 2011: 447–448

  View details for Web of Science ID 000299750700224

• Observations of shape-dependent hydrogen uptake trajectories from single nanocrystals JACS Communications Tang, M., L., Liu, N., Dionne, J., Alivisatos, A., P. 2011
• Si-based plasmonics for on-chip photonics invited review, Journal of Selected Topics in Quantum Electronics Dionne, J., Sweatlock, L., Sheldon, M., Alivisatos, A., P., Atwater, H. 2010; 16: 295
• PlasMOStor: a metal-oxide-silicon field-effect plasmonic modulator Nano Letters 9 Dionne, J., Diest, K., Sweatlock, L., Atwater, H. 2009: 897
• Flatland Photonics: Circumventing diffraction with planar plasmonic architectures Caltech Thesis Dionne, J. 2009
• Tunable color filters based on metal-insulator-metal resonators Nano Letters 9 Diest, K., Dionne, J., Spain, M., Atwater, H. 2009: 2579
• Are negative index materials achievable with surface plasmon waveguides? A case study of three plasmonic geometries Optics Express 16 Dionne, J., Verhagen, E., Polman, A., Atwater, H. 2008: 19001
• Near field visualization of strongly confined surface plasmon polaritons in metal-insulator-metal waveguides Nano Letters 8 Verhagen, E., Dionne, J., Kuipers, K., Atwater, H., Polman, A. 2008: 2925
• Silver diffusion bonding and layer transfer of lithium niobate to silver Applied Physics Letters 93 Diest, K., Archer, M., Dionne, J., Czubakowski, M., Atwater, H. 2008: 092906
• Negative refraction at visible frequencies Science 316 Lezec, H., Dionne, J., Atwater, H. 2007: 430
• Highly confined photon transport in subwavelength metallic slot waveguides NanoLetters 6 Dionne, J., Lezec, H., Atwater, H. 2006: 1928
• Plasmon slot waveguides: Towards chip-scale propagation with subwavelenth-scale localization Phys. Rev. B 73 Dionne, J., Sweatlock, L., Polman, A., Atwater, H. 2006: 035407
• Planar metal plasmon waveguides: frequency-dependent dispersion, propagation, localization, and loss beyond the free electron model Phys. Rev. B 72 Dionne, J., Sweatlock, L., Polman, A., Atwater, H. 2005: 075405
• The new ‘PN junction’: Plasmonics enables photonic access to the nanoworld MRS Bulletin Atwater, H., Maier, S., Polman, A., Dionne, J., Sweatlock, L. 2005: 30