R-3 Repository :: Browsing by Author "Ringe, Emilie"

Browsing by Author "Ringe, Emilie"

Now showing 1 - 20 of 21

A room-temperature mid-infrared photodetector for on-chip molecular vibrational spectroscopy
(AIP Publishing, 2018) Zheng, Bob; Zhao, Hangqi; Cerjan, Ben; Yazdi, Sadegh; Ringe, Emilie; Nordlander, Peter; Halas, Naomi J.; Laboratory for Nanophotonics
Infrared (IR) photodetection is of major scientific and technical interest since virtually all molecules exhibit characteristic vibrational modes in the mid-infrared region of the spectrum, giving rise to molecular spectroscopy and chemical imaging in this wavelength range. High-resolution IR spectroscopies, such as Fourier Transform IR spectroscopy, typically require large, bulky optical measurement systems and expensive photodetector components. Here, we present a high-responsivity photodetector for the mid-IR spectral region which operates at room temperature. Fabricated from silicon and aluminum, the photodetection mechanism is based on free carrier absorption, giving rise to a photoresponse rivalling commercially available cooled IR photodetectors. We demonstrate that infrared spectra of molecules deposited on this detector can be obtained by a direct electrical read-out. This work could pave the way for simple, fully integrated chemical sensors and other applications, such as chemical imaging, which would benefit from the combination of mid-IR detection, room-temperature operation, and ultracompact portability.
Aluminum Nanocrystals
(American Chemical Society, 2015) McClain, Michael J.; Schlather, Andrea E.; Ringe, Emilie; King, Nicholas S.; Liu, Lifei; Manjavacas, Alejandro; Knight, Mark W.; Kumar, Ish; Whitmire, Kenton; Everitt, Henry O.; Nordlander, Peter; Halas, Naomi J.; Laboratory for Nanophotonics
We demonstrate the facile synthesis of high purity aluminum nanocrystals over a range of controlled sizes from 70 to 220 nm diameter with size control achieved through a simple modification of solvent ratios in the reaction solution. The monodisperse, icosahedral, and trigonal bipyramidal nanocrystals are air-stable for weeks, due to the formation of a 2-4 nm thick passivating oxide layer on their surfaces. We show that the nanocrystals support size-dependent ultraviolet and visible plasmon modes, providing a far more sustainable alternative to gold and silver nanoparticles currently in widespread use.
Communicating Science Concepts to Individuals with Visual Impairments Using Short Learning Modules
(American Chemical Society, 2016) Stender, Anthony S.; Newell, Ryan; Villarreal, Eduardo; Swearer, Dayne F.; Bianco, Elisabeth; Ringe, Emilie
Of the 6.7 million individuals in the United States who are visually impaired, 63% are unemployed, and 59% have not attained an education beyond a high school diploma. Providing a basic science education to children and adults with visual disabilities can be challenging because most scientific learning relies on visual demonstrations. Creating resources to help teachers and service organizations better communicate science is thus critical both to the education of sighted students as well as to the continuing education of individuals with blindness or low vision (BLV). Here, 4 new scientific learning activities that last 5–15 min each are described. These simple exercises are designed to educate the general public, including both those who are sighted and those with BLV. The modules use tactile and auditory approaches to convey basic concepts including the metric system, material strength and deformation, transparency, and the electromagnetic spectrum. These modules were tested on 20 adults with BLV during a science outreach event. Answers to learning assessment questions indicate that the modules conveyed information about the scientific concepts presented and increased an interest in science for most participants.
Compressive Hyperspectral Microscopy of Scattering and Fluorescence of Nanoparticles
(American Chemical Society, 2022) Xu, Yibo; Lu, Liyang; Giljum, Anthony; Payne, Courtney M.; Hafner, Jason H.; Ringe, Emilie; Kelly, Kevin F.
Hyperspectral imaging in optical microscopy is of importance in the study of various submicron physical and chemical phenomena. However, its practical application is still challenging because the additional spectral dimension increases the number of sampling points to be independently measured compared to two-dimensional (2D) imaging. Here, we present a hyperspectral microscopy system through passive illumination approach based on compressive sensing (CS) using a spectrometer with a one-dimensional (1D) detector array and a digital micromirror device (DMD). The illumination is patterned after the sample rather than on it, making this technique compatible with both dark-field and bright-field imaging. The DMD diffraction issue resulting from this approach has been overcome by a novel striped DMD pattern modulation method. In addition, a split pattern method is developed for increasing the spatial resolution when employing the DMD pattern modulation. The efficacy of the system is demonstrated on nanoparticles using two model systems: extended plasmonic metal nanostructures and fluorescent microspheres. The compressive hyperspectral microscopic system provides a fast, high dynamic range, and enhanced signal-to-noise ratio (SNR) platform that yields a powerful and low-cost spectral analytical system to probe the optical properties of a myriad of nanomaterial systems. The system can also be extended to wavelengths beyond the visible spectrum with greatly reduced expense compared to other approaches that use 2D array detectors.
Eigenmode Tomography of Surface Charge Oscillations of Plasmonic Nanoparticles by Electron Energy Loss Spectroscopy
(American Chemical Society, 2015) Collins, Sean M.; Ringe, Emilie; Duchamp, Martial; Saghi, Zineb; Dunin-Borkowski, Rafal E.; Midgley, Paul A.
Plasmonic devices designed in three dimensions enable careful tuning of optical responses for control of complex electromagnetic interactions on the nanoscale. Probing the fundamental characteristics of the constituent nanoparticle building blocks is, however, often constrained by diffraction-limited spatial resolution in optical spectroscopy. Electron microscopy techniques, including electron energy loss spectroscopy (EELS), have recently been developed to image surface plasmon resonances qualitatively at the nanoscale in three dimensions using tomographic reconstruction techniques. Here, we present an experimental realization of a distinct method that uses direct analysis of modal surface charge distributions to reconstruct quantitatively the three-dimensional eigenmodes of a silver right bipyramid on a metal oxide substrate. This eigenmode tomography removes ambiguity in two-dimensional imaging of spatially localized plasmonic resonances, reveals substrate-induced mode degeneracy breaking in the bipyramid, and enables EELS for the analysis not of a particular electron-induced response but of the underlying geometric modes characteristic of particle surface plasmons.
Enhanced control of plasmonic properties of silver–gold hollow nanoparticles via a reduction-assisted galvanic replacement approach
(Royal Society of Chemistry, 2019) Daniel, Josée R.; McCarthy, Lauren A.; Ringe, Emilie; Boudreau, Denis
Hollow noble metal nanoparticles are of growing interest due to their localized surface plasmon resonance (LSPR) tunability. A popular synthetic approach is galvanic replacement which can be coupled with a co-reducer. Here, we describe the control over morphology, and therefore over plasmonic properties including energy, bandwidth, extinction and scattering intensity, offered by co-reduction galvanic replacement. This study indicates that whereas the variation of atomic stoichiometry using the co-reduction method described in this work offers a rather modest tuning range of LSPR energy when compared to traditional galvanic replacement, it nevertheless has a profound effect on shell thickness, which imparts a degree of control over scattering intensity and sensitivity to changes in the dielectric constant of the surrounding environment. Therefore, in this context particle size and gold content become two design parameters that can be used to independently tune LSPR energy and intensity.
From tunable core-shell nanoparticles to plasmonic drawbridges: Active control of nanoparticle optical properties
(AAAS, 2015) Byers, Chad P.; Zhang, Hui; Swearer, Dayne F.; Yorulmaz, Mustafa; Hoener, Benjamin S.; Huang, Da; Hoggard, Anneli; Chang, Wei-Shun; Mulvaney, Paul; Ringe, Emilie; Halas, Naomi J.; Nordlander, Peter; Link, Stephan; Landes, Christy F.
The optical properties of metallic nanoparticles are highly sensitive to interparticle distance, giving rise to dramatic but frequently irreversible color changes. By electrochemical modification of individual nanoparticles and nanoparticle pairs, we induced equally dramatic, yet reversible, changes in their optical properties. We achieved plasmon tuning by oxidation-reduction chemistry of Ag-AgCl shells on the surfaces of both individual and strongly coupled Au nanoparticle pairs, resulting in extreme but reversible changes in scattering line shape. We demonstrated reversible formation of the charge transfer plasmon mode by switching between capacitive and conductive electronic coupling mechanisms. Dynamic single-particle spectroelectrochemistry also gave an insight into the reaction kinetics and evolution of the charge transfer plasmon mode in an electrochemically tunable structure. Our study represents a highly useful approach to the precise tuning of the morphology of narrow interparticle gaps and will be of value for controlling and activating a range of properties such as extreme plasmon modulation, nanoscopic plasmon switching, and subnanometer tunable gap applications.
Investigation of Light-Matter Interactions in Nanomaterials via Correlated Optical-Electron Microscopy
(2018-08-10) Villarreal, Eduardo; Ringe, Emilie
Nanomaterials have become more relevant in several sectors (environmental, energy storage, nanomedicine, etc) over recent years, where their unique properties compared to bulk are exploited. The difference in surface area is one of the reasons nanomaterials display tailorable chemical, mechanical, and physical properties due to extremely small grain size. Unfortunately, the properties of most of the nanomaterials are still to be characterized due to the need of precise instrumentation, preventing from making them convenient for consumer/industry applications. This thesis addresses the study and understanding of the relationship of nanomaterials’ optical properties and their physical structure, as well as the creation of protocols to facilitate characterization. By understanding this relationship, nanomaterials can be tailored to exploit their properties for many applications in many sectors. Based on this premise, two different systems were studied and correlated. First, the sensitivity-structure correlation of gold nanoparticles (NPs) for biosensing applications is studied. In such study, a single-nanoparticle approach was used, and statistical models were applied to correlate the refractive index sensitivity of gold NPs with their shape and size. Based on such correlation, rounder NP resulted to be more sensitive to surface events, providing insights on particle selection for biosensors. Furthermore, the nanoparticles were functionalized as DNA sensors as a proof of concept. Next, the Micro Extinction Spectroscopy development is described, as well its use as an analytical tool to study the influence of defects in 2D semiconductors. With such tool, a monolayer transition metal dichalcogenides library was create by detecting excitons with their local absorption. Finally, monolayer MoS2 was treated by both oxygen plasma exposure and hydrogen treatment to create defects and alter its band gap. The material was characterized before and after the treatment using optical spectroscopy, and information about its composition, bandgap, and optical response was revealed. In sum, the projects presented here are unified by the need for structure-function correlations, which are achieved with optical spectroscopy and electron microscopy.
Micro-Extinction Spectroscopy (MExS): a versatile optical characterization technique
(Springer, 2018) Kumar, Anjli; Villarreal, Eduardo; Zhang, Xiang; Ringe, Emilie
Micro-Extinction Spectroscopy (MExS), a flexible, optical, and spatial-scanning hyperspectral technique, has been developed and is described with examples. Software and hardware capabilities are described in detail, including transmission, reflectance, and scattering measurements. Each capability is demonstrated through a case study of nanomaterial characterization, i.e., transmission of transition metal dichalcogenides revealing transition energy and efficiency, reflectance of transition metal dichalcogenides grown on nontransparent substrates identifying the presence of monolayer following electrochemical ablation, and scattering to study single plasmonic nanoparticles and obtain values for the refractive index sensitivity and sensing figure of merit of over a hundred single particles with various shapes and sizes. With the growing integration of nanotechnology in many areas, MExS can be a powerful tool to both characterize and test nanomaterials.
Nanocrystalline materials: recent advances in crystallographic characterization techniques
(International Union of Crystallography, 2014) Ringe, Emilie
Most properties of nanocrystalline materials are shape-dependent, providing their exquisite tunability in optical, mechanical, electronic and catalytic properties. An example of the former is localized surface plasmon resonance (LSPR), the coherent oscillation of conduction electrons in metals that can be excited by the electric field of light; this resonance frequency is highly dependent on both the size and shape of a nanocrystal. An example of the latter is the marked difference in catalytic activity observed for different Pd nanoparticles. Such examples highlight the importance of particle shape in nanocrystalline materials and their practical applications. However, one may ask ‘how are nanoshapes created?’, ‘how does the shape relate to the atomic packing and crystallography of the material?’, ‘how can we control and characterize the external shape and crystal structure of such small nanocrystals?’. This feature article aims to give the reader an overview of important techniques, concepts and recent advances related to these questions. Nucleation, growth and how seed crystallography influences the final synthesis product are discussed, followed by shape prediction models based on seed crystallography and thermodynamic or kinetic parameters. The crystallographic implications of epitaxy and orientation in multilayered, core-shell nanoparticles are overviewed, and, finally, the development and implications of novel, spatially resolved analysis tools are discussed.
Near-field mapping of three-dimensional surface charge poles for hybridized plasmon modes
(AIP Publishing LLC, 2015) Huang, Yu; Ringe, Emilie; Hou, Mengjing; Ma, Lingwei; Zhang, Zhengjun; Laboratory for Nanophotonics
We describe a new computational approach to mapping three-dimensional (3D) surface charge poles and thus to determine complicated and hybridized plasmon modes in metallic nanostructures via finite element method (FEM) calculations. 3D surface charge distributions at the near-field resonance energies are calculated directly using Gaussﾒ law. For a nanosphere dimer, we demonstrate that higher-order hybridized plasmon modes can be addressed clearly. As an improvement to conventional mapping approaches, this new approach provides a better understanding of comprehensive physical image of plasmonic systems necessary for fundamental studies and spectroscopy applications.
Plasmon and compositional mapping of plasmonic nanostructures
(SPIE, 2014) Ringe, Emilie; Collins, Sean M.; DeSantis, Christopher J.; Skrabalak, Sara E.; Midgley, Paul A.
Recently, co-reduction of Au and Pd has allowed the synthesis of complex Au core/AuPd shell nanoparticles with elongated tips and cubic-like symmetry. Optical studies have shown strong plasmonic behavior and high refractive index sensitivities. In this paper, we describe the composition and the near-field plasmonic behavior of those complex structures. Monochromated STEM-EELS, Cathodoluminescence, and EDS mapping reveals the different resonant modes in these particles, and shows that Pd, a poor plasmonic metal, does not prevent strong resonances and could actually be extremely helpful for plasmon-enhanced catalysis.
Resonances of nanoparticles with poor plasmonic metal tips
(Macmillan Publishers Limited, 2015) Ringe, Emilie; DeSantis, Christopher J.; Collins, Sean M.; Duchamp, Martial; Dunin-Borkowski, Rafal E.; Skrabalak, Sara E.; Midgley, Paul A.
The catalytic and optical properties of metal nanoparticles can be combined to create platforms for light-driven chemical energy storage and enhanced in-situ reaction monitoring. However, the heavily damped plasmon resonances of many catalytically active metals (e.g. Pt, Pd) prevent this dual functionality in pure nanostructures. The addition of catalytic metals at the surface of efficient plasmonic particles thus presents a unique opportunity if the resonances can be conserved after coating. Here, nanometer resolution electron-based techniques (electron energy loss, cathodoluminescence, and energy dispersive X-ray spectroscopy) are used to show that Au particles incorporating a catalytically active but heavily damped metal, Pd, sustain multiple size-dependent localized surface plasmon resonances (LSPRs) that are narrow and strongly localized at the Pd-rich tips. The resonances also couple with a dielectric substrate and other nanoparticles, establishing that the full range of plasmonic behavior is observed in these multifunctional nanostructures despite the presence of Pd.
Resonant Coupling between Molecular Vibrations and Localized Surface Plasmon Resonance of Faceted Metal Oxide Nanocrystals
(American Chemical Society, 2017) Agrawal, Ankit; Singh, Ajay; Yazdi, Sadegh; Singh, Amita; Ong, Gary K.; Bustillo, Karen; Johns, Robert W.; Ringe, Emilie; Milliron, Delia J.
Doped metal oxides are plasmonic materials that boast both synthetic and postsynthetic spectral tunability. They have already enabled promising smart window and optoelectronic technologies and have been proposed for use in surface enhanced infrared absorption spectroscopy (SEIRA) and sensing applications. Herein, we report the first step toward realization of the former utilizing cubic F and Sn codoped In2O3 nanocrystals (NCs) to couple to the C–H vibration of surface-bound oleate ligands. Electron energy loss spectroscopy is used to map the strong near-field enhancement around these NCs that enables localized surface plasmon resonance (LSPR) coupling between adjacent nanocrystals and LSPR-molecular vibration coupling. Fourier transform infrared spectroscopy measurements and finite element simulations are applied to observe and explain the nature of the coupling phenomena, specifically addressing coupling in mesoscale assembled films. The Fano line shape signatures of LSPR-coupled molecular vibrations are rationalized with two-port temporal coupled mode theory. With this combined theoretical and experimental approach, we describe the influence of coupling strength and relative detuning between the molecular vibration and LSPR on the enhancement factor and further explain the basis of the observed Fano line shape by deconvoluting the combined response of the LSPR and molecular vibration in transmission, absorption and reflection. This study therefore illustrates various factors involved in determining the LSPR–LSPR and LSPR–molecular vibration coupling for metal oxide materials and provides a fundamental basis for the design of sensing or SEIRA substrates.
Reversible Shape and Plasmon Tuning in Hollow AgAu Nanorods
(American Chemical Society, 2016) Yazdi, Sadegh; Daniel, Josée R.; Large, Nicolas; Schatz, George C.; Boudreau, Denis; Ringe, Emilie
The internal structure of hollow AgAu nanorods created by partial galvanic replacement was manipulated reversibly, and its effect on optical properties was mapped with nanometer resolution. Using the electron beam in a scanning transmission electron microscope to create solvated electrons and reactive radicals in an encapsulated solution-filled cavity in the nanorods, Ag ions were reduced nearby the electron beam, reshaping the core of the nanoparticles without affecting the external shape. The changes in plasmon-induced near-field properties were then mapped with electron energy-loss spectroscopy without disturbing the internal structure, and the results are supported by finite-difference time-domain calculations. This reversible shape and near-field control in a hollow nanoparticle actuated by an external stimulus introduces possibilities for applications in reprogrammable sensors, responsive materials, and optical memory units. Moreover, the liquid-filled nanorod cavity offers new opportunities for in situ microscopy of chemical reactions.
Spectroelectrochemistry of Nanomaterials
(2018-11-12) Kumar, Anjli; Ringe, Emilie
As the development and application of novel nanomaterials is continually expanding, so is the need for versatile characterization methods that can probe nanoscale processes as they occur. Such characterization techniques would permit non-destructive and parallel spectroscopy and imaging of nanomaterials. The objective of this work is to address the need for such techniques. First, a new spectroelectrochemical characterization technique, Micro-Extinction Spectroscopy (MExS), is presented, including instrumental design as well as data acquisition and analysis algorithms. Two nanomaterial systems are then studied with MExS: two-dimensional transmission metal dichalcogenides (TMDs) and plasmonic nanoparticles. For TMDs, in situ and hyperspectral reflectance studies coupled with cyclic voltammetry and chronocoulometry enable the time-resolved observation of the process of electroablation, an oxidative technique recently developed for the synthesis of monolayer TMDs. For plasmonic nanoparticles, dark-field microscopy is used in conjunction with chronocoulometry to observe, in a hyperspectral manner, single-particle electrodeposition, a technique developed for nanoparticle surface modification. Together, these two techniques position spectroelectrochemistry as a rich tool for optical nanomaterials, capable of both synthesis and concurrent characterization.
Structural and Optical Properties of Discrete Dendritic Pt Nanoparticles on Colloidal Au Nanoprisms
(American Chemical Society, 2016) Leary, Rowan K.; Kumar, Anjli; Straney, Patrick J.; Collins, Sean M.; Yazdi, Sadegh; Dunin-Borkowski, Rafal E.; Midgley, Paul A.; Millstone, Jill E.; Ringe, Emilie
Catalytic and optical properties can be coupled by combining different metals into nanoscale architectures where both the shape and composition provide fine-tuning of functionality. Here, discrete, small Pt nanoparticles (diameter = 3 - 6 nm) were grown in linear arrays on Au nanoprisms, and the resulting structures are shown to retain strong localized surface plasmon resonances. Multi-dimensional electron microscopy and spectroscopy techniques (energy dispersive X-ray spectroscopy, electron tomography and electron energy-loss spectroscopy) were used to unravel their local composition, 3D morphology, growth patterns, and optical properties. The composition and tomographic analyses disclose otherwise ambiguous details of the Pt-decorated Au nanoprisms, revealing that both pseudospherical protrusions and dendritic Pt nanoparticles grow on all faces of the nanoprisms (the faceted or occasionally twisted morphologies of which are also revealed), and shed light on the alignment of Pt nanoparticles. The electron energy-loss spectroscopy investigations show that the Au nanoprisms sustain multiple localized surface plasmon resonances despite the presence of pendant Pt nanoparticles. The plasmonic fields at the surface of the nanoprisms indeed extend into the Pt nanoparticles, opening possibilities for combined optical and catalytic applications. These insights pave the way towards comprehensive nano-engineering of multi-functional bimetallic nanostructures, with potential application in plasmon-enhanced catalysis and in-situ monitoring of chemical processes via surface-enhanced spectroscopy.
Synthesis and Application of Graphene Based Nanomaterials
(2015-04-08) Peng, Zhiwei; Tour, James M.; Engel, Paul S; Ringe, Emilie
Graphene, a two-dimensional sp2-bonded carbon material, has recently attracted major attention due to its excellent electrical, optical and mechanical properties. Depending on different applications, graphene and its derived hybrid nanomaterials can be synthesized by either bottom-up chemical vapor deposition (CVD) methods for electronics, or various top-down chemical reaction methods for energy generation and storage devices. My thesis begins with the investigation of CVD synthesis of graphene thin films in Chapter 1, including the direct growth of bilayer graphene on insulating substrates and synthesis of “rebar graphene”: a hybrid structure with graphene and carbon or boron nitride nanotubes. Chapter 2 discusses the synthesis of nanoribbon-shaped materials and their applications, including splitting of vertically aligned multi-walled carbon nanotube carpets for supercapacitors, synthesis of dispersable ferromagnetic graphene nanoribbon stacks with enhanced electrical percolation properties in magnetic field, graphene nanoribbon/SnO2 nanocomposite for lithium ion batteries, and enhanced electrocatalysis for hydrogen evolution reactions from WS2 nanoribbons. Next, Chapter 3 discusses graphene coated iron oxide nanomaterials and their use in energy storage applications. Finally, Chapter 4 introduces the development, characterization, and fabrication of laser induced graphene and its application as supercapacitors.
Tunable Lattice Coupling of Multipole Plasmon Modes and Near-Field Enhancement in Closely Spaced Gold Nanorod Arrays
(Nature Publishing Group, 2016) Huang, Yu; Zhang, Xian; Ringe, Emilie; Hou, Mengjing; Ma, Lingwei; Zhang, Zhengjun
Considering the nanogap and lattice effects, there is an attractive structure in plasmonics: closely spaced metallic nanoarrays. In this work, we demonstrate experimentally and theoretically the lattice coupling of multipole plasmon modes for closely spaced gold nanorod arrays, offering a new insight into the higher order cavity modes coupled with each other in the lattice. The resonances can be greatly tuned by changes in inter-rod gaps and nanorod heights while the influence of the nanorod diameter is relatively insignificant. Experimentally, pronounced suppressions of the reflectance are observed. Meanwhile, the near-field enhancement can be further enhanced, as demonstrated through surface enhanced Raman scattering (SERS). We then confirm the correlation between the near-field and far-field plasmonic responses, which is significantly important for maximizing the near-field enhancement at a specific excitation wavelength. This lattice coupling of multipole plasmon modes is of broad interest not only for SERS but also for other plasmonic applications, such as subwavelength imaging or metamaterials.
Ultrasensitive Plasmonic Platform for Label-Free Detection of Membrane-Associated Species
(American Chemical Society, 2016) Bruzas, Ian; Unser, Sarah; Yazdi, Sadegh; Ringe, Emilie; Sagle, Laura
Lipid membranes and membrane proteins are important biosensing targets, motivating the development of label-free methods with improved sensitivity. Silica-coated metal nanoparticles allow these systems to be combined with supported lipid bilayers for sensing membrane proteins through localized surface plasmon resonance (LSPR). However, the small sensing volume of LSPR makes the thickness of the silica layer critical for performance. Here, we develop a simple, inexpensive, and rapid sol–gel method for preparing thin conformal, continuous silica films and demonstrate its applicability using gold nanodisk arrays with LSPRs in the near-infrared range. Silica layers as thin as ∼5 nm are observed using cross-sectional scanning transmission electron microscopy. The loss in sensitivity due to the thin silica coating was found to be only 16%, and the biosensing capabilities of the substrates were assessed through the binding of cholera toxin B to GM1 lipids. This sensor platform should prove useful in the rapid, multiplexed detection and screening of membrane-associated biological targets.

Browsing by Author "Ringe, Emilie"

Results Per Page

Sort Options