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Showing papers on "Surface plasmon resonance published in 2010"


Journal ArticleDOI
TL;DR: The surface plasmon resonance of gold nanoparticles leads to strong electromagnetic fields on the particle surface and consequently enhances all the radiative properties such as absorption and scattering as discussed by the authors, and the strongly absorbed light is converted to heat quickly via a series of nonradiative processes.

1,659 citations


Journal Article
TL;DR: In this article, the authors describe localized surface plasmon resonance (LSPR) arising from p-type carriers in vacancy-doped semiconductor quantum dots, which opens up possibilities for light harvesting, nonlinear optics, optical sensing and manipulation of solid-state processes in single nanocrystals.
Abstract: Quantum confinement of electronic wavefunctions in semiconductor quantum dots (QDs) yields discrete atom-like and tunable electronic levels, thereby allowing the engineering of excitation and emission spectra. Metal nanoparticles, on the other hand, display strong resonant interactions with light from localized surface plasmon resonance (LSPR) oscillations of free carriers, resulting in enhanced and geometrically tunable absorption and scattering resonances. The complementary attributes of these nanostructures lends strong interest toward integration into hybrid nanostructures to explore enhanced properties or the emergence of unique attributes arising from their interaction. However, the physicochemical interface between the two components can be limiting for energy transfer and synergistic coupling within such a hybrid nanostructure. Therefore, it is advantageous to realize both attributes, i.e., LSPRs and quantum confinement within the same nanostructure. Here, we describe well-defined LSPRs arising from p-type carriers in vacancy-doped semiconductor quantum dots. This opens up possibilities for light harvesting, non-linear optics, optical sensing and manipulation of solid-state processes in single nanocrystals.

1,159 citations


Journal ArticleDOI
16 Jun 2010-ACS Nano
TL;DR: An evolution from a loosely attached toward an irreversible attached protein corona over time was observed and mass spectrometry of the digested protein coronia revealed albumin as the most abundant component which suggests an improved biocompatibility.
Abstract: In this work, we explore the formation of the protein corona after exposure of metallic Au nanoparticles (NPs), with sizes ranging from 4 to 40 nm, to cell culture media containing 10% of fetal bovine serum. Under in vitro cell culture conditions, zeta potential measurements, UV-vis spectroscopy, dynamic light scattering and transmission electron microscope analysis were used to monitor the time evolution of the inorganic NP-protein corona formation and to characterize the stability of the NPs and their surface state at every stage of the experiment. As expected, the red-shift of the surface plasmon resonance peak, as well as the drop of surface charge and the increase of the hydrodynamic diameter indicated the conjugation of proteins to NPs. Remarkably, an evolution from a loosely attached toward an irreversible attached protein corona over time was observed. Mass spectrometry of the digested protein corona revealed albumin as the most abundant component which suggests an improved biocompatibility.

1,057 citations


Journal ArticleDOI
TL;DR: This Review highlights morphology-dependent properties of nonspherical noble metal nanoparticles with a focus on localized surface plasmon resonance and local field enhancement, as well as their applications in various fields including Raman spectroscopy, fluorescence enhancement, analytics and sensing, photothermal therapy, (bio-)diagnostics, and imaging.
Abstract: Nanoparticles of noble metals belong to the most extensively studied colloidal systems in the field of nanoscience and nanotechnology. Due to continuing progress in the synthesis of nanoparticles with controlled morphologies, the exploration of unique morphology-dependent properties has gained momentum. Anisotropic features in nonspherical nanoparticles make them ideal candidates for enhanced chemical, catalytic, and local field related applications. Nonspherical plasmon resonant nanoparticles offer favorable properties for their use as analytical tools, or as diagnostic and therapeutic agents. This Review highlights morphology-dependent properties of nonspherical noble metal nanoparticles with a focus on localized surface plasmon resonance and local field enhancement, as well as their applications in various fields including Raman spectroscopy, fluorescence enhancement, analytics and sensing, photothermal therapy, (bio-)diagnostics, and imaging.

922 citations


Journal ArticleDOI
TL;DR: In this paper, the authors discuss how the coupling of plasmon modes in certain nanostructure geometries (such as nanoparticle dimers and nanoshells) allows systematic tuning of the optical resonance, and also the confinement and enhancement of the near-field, making possible improved refractive index sensing and fieldenhanced spectroscopy and photochemistry.

806 citations


Journal ArticleDOI
TL;DR: The calculations show that the proposed graphene-on-gold SPR biosensor is three times more sensitive than the conventional gold thin film SPR bios sensor, due to increased adsorption of biomolecules on graphene and the optical property of graphene.
Abstract: A surface plasmon resonance (SPR) based graphene biosensor is presented. It consists of a graphene sheet coated above a gold thin film, which has been proposed and experimentally fabricated recently [ChemPhysChem 11, 585 (2010)]. The biosensor uses attenuated total reflection (ATR) method to detect the refractive index change near the sensor surface, which is due to the adsorption of biomolecules. Our calculations show that the proposed graphene-on-gold SPR biosensor (with L graphene layers) is (1 + 0.025 L) x gamma (where gamma > 1) times more sensitive than the conventional gold thin film SPR biosensor. The improved sensitivity is due to increased adsorption of biomolecules on graphene (represented by the factor gamma) and the optical property of graphene.

801 citations


Journal ArticleDOI
TL;DR: This study demonstrates that the creation of hot spots, where two particles are in subnanometer proximity or have coalesced to form crevices, is paramount to achieving maximum SERS enhancements.
Abstract: Understanding the detailed relationship between nanoparticle structure and activity remains a significant challenge for the field of surface-enhanced Raman spectroscopy. To this end, the structural and optical properties of individual plasmonic nanoantennas comprised of Au nanoparticle assemblies that are coated with organic reporter molecules and encapsulated by a SiO2 shell have been determined using correlated transmission electron microscopy (TEM), dark-field Rayleigh scattering microscopy, surface-enhanced Raman scattering (SERS) microscopy, and finite element method (FEM) calculations. The distribution of SERS enhancement factors (EFs) for a structurally and optically diverse set of nanoantennas is remarkably narrow. For a collection of 30 individual nanoantennas ranging from dimers to heptamers, the EFs vary by less than 2 orders of magnitude. Furthermore, the EFs for the hot-spot-containing nanoparticles are uncorrelated to aggregation state and localized surface plasmon resonance (LSPR) wavelengt...

727 citations


Journal ArticleDOI
TL;DR: This paper reviews the recent research progress in the incorporation of plasmonic nanostructures with photovoltaic devices and the potential for surface plAsmon enhanced absorption, and outlines a variety of cell architectures incorporating metal nanostructure shapes.
Abstract: This paper reviews the recent research progress in the incorporation of plasmonic nanostructures with photovoltaic devices and the potential for surface plasmon enhanced absorption. We first outline a variety of cell architectures incorporating metal nanostructures. We then review the experimental fabrication methods and measurements to date, as well as systematic theoretical studies of the optimal nanostructure shapes. Finally we discuss photovoltaic absorber materials that could benefit from surface plasmon enhanced absorption.

687 citations


Journal ArticleDOI
TL;DR: It is shown that clusters of plasmonic nanoparticles and nanostructures support Fano resonances, and that this spectral feature, produced by the interference between bright and dark modes of the nanoparticle cluster, is strongly dependent upon both geometry and local dielectric environment.
Abstract: Clusters of plasmonic nanoparticles and nanostructures support Fano resonances. Here we show that this spectral feature, produced by the interference between bright and dark modes of the nanoparticle cluster, is strongly dependent upon both geometry and local dielectric environment. This permits a highly sensitive tunability of the Fano dip in both wavelength and amplitude by varying cluster dimensions, geometry, and relative size of the individual nanocluster components. Plasmonic nanoclusters show an unprecedented sensitivity to dielectric environment with a local surface plasmon resonance figure of merit of 5.7, the highest yet reported for localized surface plasmon resonance sensing in a finite nanostructure.

607 citations


Journal ArticleDOI
TL;DR: The surface plasmon resonance (SPR) of silver nanoparticles (AgNPs) was studied with the discrete dipole approximation considering different shapes, sizes, dielectric environments, and supraparticles assemblies.
Abstract: The surface plasmon resonance (SPR) of silver nanoparticles (AgNPs) was studied with the discrete dipole approximation considering different shapes, sizes, dielectric environments, and supraparticles assemblies. In particular, we focused our simulations on AgNPs with sizes below 10 nm, where the correction of silver dielectric constant for intrinsic size effects is necessary. We found that AgNPs shape and assembly can induce distinctive features in the extinction spectra and that SPR is more intense when AgNPs have discoid or flat shapes and are embedded in a dielectric shell with high refractive index. However, the SPR loses much of its distinctive features when size effects and stabilizing molecules induce significant broadening of the extinction bands that is often observed in the case of thiolated AgNPs smaller than about 5 nm. These results are useful indications for in situ characterization and monitoring of AgNPs synthesis and for the engineering of AgNPs with new plasmonic properties.

573 citations


Journal ArticleDOI
TL;DR: This work discus basic wet-chemical routes to fabricate conjugates of gold, silver, or composite particles with controllable size, shape, structure and with surface functionalization by biospecific molecules and application of plasmonic bioconjugates to such fields as homogeneous and solid-phase assays, biomedical sensing and imaging, biodistribution and toxicity aspects, drug delivery and plAsmonic photothermal therapy.
Abstract: Nanoparticle plasmonics is a rapidly emerging research field that deals with the fabrication and optical characterization of noble metal nanoparticles of various size, shape, structure, and tunable plasmon resonances over VIS-NIR spectral band. The recent simultaneous advances in synthesis, characterization, electromagnetic simulation, and surface functionalization of plasmonic nanoparticles by biospecific molecular probes have led to a perfect publication storm in discoveries and potential biomedical applications of plasmon-resonant nanoparticle bioconjugates. Here, we present an overview of these topics. First, we discus basic wet-chemical routes to fabricate conjugates of gold, silver, or composite particles with controllable size, shape, structure and with surface functionalization by biospecific molecules. Second, we consider the single-particle dipole and multipole optics and coupled plasmonic nanoparticle arrays. Finally, we discus application of plasmonic bioconjugates to such fields as homogeneous and solid-phase assays, biomedical sensing and imaging, biodistribution and toxicity aspects, drug delivery and plasmonic photothermal therapy.

Journal ArticleDOI
17 Nov 2010-ACS Nano
TL;DR: The results show that, beyond an in-depth NPs characterization before cellular experiments, a detailed understanding of the effects elicited by cell culture media on NPs is crucial for standardized nanotoxicology tests.
Abstract: The development of appropriate in vitro protocols to assess the potential toxicity of the ever expanding range of nanoparticles represents a challenging issue, because of the rapid changes of their intrinsic physicochemical properties (size, shape, reactivity, surface area, etc.) upon dispersion in biological fluids. Dynamic formation of protein coating around nanoparticles is a key molecular event, which may strongly impact the biological response in nanotoxicological tests. In this work, by using citrate-capped gold nanoparticles (AuNPs) of different sizes as a model, we show, by several spectroscopic techniques (dynamic light scattering, UV−visible, plasmon resonance light scattering), that proteins−NP interactions are differently mediated by two widely used cellular media (i.e., Dulbecco Modified Eagle’s medium (DMEM) and Roswell Park Memorial Institute medium (RPMI), supplemented with fetal bovine serum). We found that, while DMEM elicits the formation of a large time-dependent protein corona, RPMI s...

Journal ArticleDOI
18 Oct 2010-Small
TL;DR: Co coating Au nanocrystals with semiconductor materials that have band gap energies smaller than the illumination laser energy can improve the photothermal conversion efficiency owing to the presence of an additional light absorption channel.
Abstract: Plasmon-based photothermal therapy is one of the most intriguing applications of noble metal nanostructures. The photothermal conversion efficiency is an essential parameter in practically realizing this application. The effects of the plasmon resonance wavelength, particle volume, shell coating, and assembly on the photothermal conversion efficiencies of Au nanocrystals are systematically studied by directly measuring the temperature of Au nanocrystal solutions with a thermocouple and analyzed on the basis of energy balance. The temperature of Au nanocrystal solutions reaches the maximum at ∼75 °C when the plasmon resonance wavelength of Au nanocrystals is equal to the illumination laser wavelength. For Au nanocrystals with similar shapes, the larger the nanocrystal, the smaller the photothermal conversion efficiency becomes. The photothermal conversion can also be controlled by shell coating and assembly through the change in the plasmon resonance energy of Au nanocrystals. Moreover, coating Au nanocrystals with semiconductor materials that have band gap energies smaller than the illumination laser energy can improve the photothermal conversion efficiency owing to the presence of an additional light absorption channel.

Journal ArticleDOI
TL;DR: In this article, surface plasmons are used to enhance the light trapping properties of thin-film solar cells by tuning the surface plasmon resonance to enhance absorption in the wavelength region required.

Journal ArticleDOI
TL;DR: The optical trapping of Au nanoparticles with dimensions as small as 10 nm in the gap of plasmonic dipole antennas is demonstrated, indicating the possibility to trap nanoparticles only a few nanometers in size.
Abstract: The optical trapping of Au nanoparticles with dimensions as small as 10 nm in the gap of plasmonic dipole antennas is demonstrated. Single nanoparticle trapping events are recorded in real time by monitoring the Rayleigh scattering spectra of individual plasmonic antennas. Numerical simulations are also performed to interpret the experimental results, indicating the possibility to trap nanoparticles only a few nanometers in size. This work unveils the potential associated with the integration of plasmonic trapping with localized surface plasmon resonance based sensing techniques, in order to deliver analyte to specific, highly sensitive regions ("hot spots").

Journal ArticleDOI
30 Aug 2010-Langmuir
TL;DR: The sensitivity toward changes in the local refractive index was found to increase for larger nanostars, though lower figure of merit (FOM) values were obtained because of the larger polydispersity.
Abstract: Gold nanostars are multibranched nanoparticles with sharp tips, which display extremely interesting plasmonic properties but require optimization. We present a systematic investigation of the influence of different parameters on the size, morphology, and monodispersity of Au nanostars obtained via seeded growth in concentrated solutions of poly(vinylpyrrolidone) in N,N-dimethylformamide. Controlled prereduction of Au(3+) to Au(+) was found to influence monodispersity (narrower plasmon bands), while the [HAuCl(4)]/[seed] molar ratio significantly affects the morphology and tip plasmon resonance frequency. We also varied the size of the seeds (2-30 nm) and found a clear influence on the final nanostar dimensions as well as on the number of spikes, while synthesis temperature notably affects the morphology of the particles, with more rounded morphologies formed above 60 °C. This rounding effect allowed us to confirm the importance of sharp tips on the optical enhancing behavior of these nanoparticles in surface-enhanced raman scattering (SERS). Additionally, the sensitivity toward changes in the local refractive index was found to increase for larger nanostars, though lower figure of merit (FOM) values were obtained because of the larger polydispersity.

Journal ArticleDOI
TL;DR: An approach for synthesizing an ideal class of colloidal Ag nanoparticles with highly uniform morphologies and narrow size distributions is reported, indicating that lowered electron conductivity in the outermost atomic layer, due to chemical interactions, is the cause of the red-shift.
Abstract: The size-dependence of surface plasmon resonances (SPRs) is poorly understood in the small particle limit due to complex physical/chemical effects and uncertainties in experimental samples. In this article, we report an approach for synthesizing an ideal class of colloidal Ag nanoparticles with highly uniform morphologies and narrow size distributions. Optical measurements and theoretical analyses for particle diameters in the d ≈ 2–20 nm range are presented. The SPR absorption band exhibits an exceptional behavior: As size decreases from d ≈ 20 nm it blue-shifts but then turns over near d ≈ 12 nm and strongly red-shifts. A multilayer Mie theory model agrees well with the observations, indicating that lowered electron conductivity in the outermost atomic layer, due to chemical interactions, is the cause of the red-shift. We corroborate this picture by experimentally demonstrating precise chemical control of the SPR peak positions via ligand exchange.

Journal ArticleDOI
TL;DR: In this paper, the authors use simulations based on the boundary element method to determine the sensitivity of gold nanorods of various aspect ratios for plasmonic sensors and find values between 3 and 4 to be optimal.
Abstract: The plasmon resonance of metal nanoparticles shifts upon refractive index changes of the surrounding medium through the binding of analytes. The use of this principle allows one to build ultra-small plasmon sensors that can detect analytes (e.g., biomolecules) in volumes down to attoliters. We use simulations based on the boundary element method to determine the sensitivity of gold nanorods of various aspect ratios for plasmonic sensors and find values between 3 and 4 to be optimal. Experiments on single particles confirm these theoretical results. We are able to explain the optimum by showing a corresponding maximum for the quality factor of the plasmon resonance.

Journal ArticleDOI
TL;DR: The current state of development of SPRi technology and its application including commercially available SPRi instruments are reviewed and attention is given to surface chemistries for biochip functionalisation and suitable approaches to improve sensitivity.

Journal ArticleDOI
21 Jan 2010-ACS Nano
TL;DR: Polarization-dependent dark-field microspectroscopy on individual heterodimer structures fabricated using a novel electromigration assembly method allows us to examine Fano resonances, avoided crossing behavior, and a surprising dependence of the scattering spectrum on the direction of excitation, known as the "optical nanodiode" effect.
Abstract: Heterodimers—two closely adjacent metallic nanoparticles differing in size or shape—exemplify a simple nanoscale geometry that gives rise to a remarkably rich set of properties. These include Fano resonances, avoided crossing behavior, and a surprising dependence of the scattering spectrum on the direction of excitation, known as the “optical nanodiode” effect. In a series of studies, we experimentally probe and theoretically analyze these properties in heterodimer nanostructures, where nanoparticle size and plasmon resonance frequency are varied systematically. Polarization-dependent dark-field microspectroscopy on individual heterodimer structures fabricated using a novel electromigration assembly method allows us to examine these properties in detail. These studies expand our understanding of the range of physical effects that can be observed in adjacent metallic nanoparticle pairs.

Journal ArticleDOI
TL;DR: In this article, the plasmonic photoelectric conversion from visible to near-infrared wavelength without deteriorating photo-electric conversion by using electrodes in which gold nanorods are elaborately arrayed on the surface of a TiO2 single crystal.
Abstract: Nanoparticles of noble metals exhibit localized surface plasmons (LSPs) associated with the enhancement of an electromagnetic field due to its localization in nanometric domains at the surface of nanoparticles. We demonstrate the plasmonic photoelectric conversion from visible to near-infrared wavelength without deteriorating photoelectric conversion by using electrodes in which gold nanorods are elaborately arrayed on the surface of a TiO2 single crystal.

Journal ArticleDOI
TL;DR: This work probes, using polarized scattering spectroscopy, the coupling in a pair of nonequivalent particles (silver/gold nanoparticle heterodimer) that allows us to observe both in-phase and out-of-phase plasmon modes.
Abstract: Electromagnetic coupling between plasmon resonant nanoparticles follows principles of molecular hybridization, that is, particle plasmons hybridize to form a lower energy bonding plasmon mode and a higher energy antibonding plasmon mode. For coupling between equivalent particles (homodimer), the in-phase mode is optically allowed, whereas the out-of-phase mode is dark due to the cancellation of the equivalent dipole moments. We probe, using polarized scattering spectroscopy, the coupling in a pair of nonequivalent particles (silver/gold nanoparticle heterodimer) that allows us to observe both in-phase and out-of-phase plasmon modes. The hybridization model postulates that the bonding modes should be red shifted with respect to the gold particle plasmon resonance and the antibonding modes blue shifted with respect to the silver particle plasmon resonance. In practice, the antibonding modes are red shifted with respect to the silver plasmon resonance. This anomalous shift is due to the coupling of the silve...

Journal ArticleDOI
TL;DR: The bulk self-alignment of dispersed gold nanorods imposed by the intrinsic cylindrical micelle self-assembly in nematic and hexagonal liquid crystalline phases of anisotropic fluids results in a switchable polarization-sensitive plasmon resonance exhibiting stark differences from that of the same nanorod in isotropic fluids.
Abstract: We demonstrate the bulk self-alignment of dispersed gold nanorods imposed by the intrinsic cylindrical micelle self-assembly in nematic and hexagonal liquid crystalline phases of anisotropic fluids. External magnetic field and shearing allow for alignment and realignment of the liquid crystal matrix with the ensuing long-range orientational order of well-dispersed plasmonic nanorods. This results in a switchable polarization-sensitive plasmon resonance exhibiting stark differences from that of the same nanorods in isotropic fluids. The device-scale bulk nanoparticle alignment may enable optical metamaterial mass production and control of properties arising from combining the switchable nanoscale structure of anisotropic fluids with the surface plasmon resonance properties of the plasmonic nanorods.

Journal ArticleDOI
TL;DR: This work demonstrates a multiplexed method to measure the masses of individual viral particles and to study the binding activity of the viral particles in solution by high-resolution surface plasmon resonance microscopy.
Abstract: We report on label-free imaging, detection, and mass/size measurement of single viral particles in solution by high-resolution surface plasmon resonance microscopy. Diffraction of propagating plasmon waves along a metal surface by the viral particles creates images of the individual particles, which allow us to detect the binding of the viral particles to surfaces functionalized with and without antibodies. We show that the intensity of the particle image is related to the mass of the particle, from which we determine the mass and mass distribution of influenza viral particles with a mass detection limit of approximately 1 ag (or 0.2 fg/mm2). This work demonstrates a multiplexed method to measure the masses of individual viral particles and to study the binding activity of the viral particles.

Journal ArticleDOI
TL;DR: Sensing of pure gases over Ag nanoparticles using LSPR spectroscopy, where the detected changes in bulk refractive index are <5 × 10(-4) refractive Index units (RIU), and a novel strategy for amplifying the sensing signal by coating the plasmonic substrate with a metal-organic framework (MOF) material.
Abstract: Despite its high refractive index sensitivity, localized surface plasmon resonance (LSPR) spectroscopy has been generally restricted to large biological analytes. Sensing of smaller molecules is a compelling target for this technique; in particular, LSPR spectroscopy could be utilized to detect hazardous or toxic gases and manage industrial processes involving gaseous chemicals. Here, we report sensing of pure gases over Ag nanoparticles using LSPR spectroscopy, where the detected changes in bulk refractive index are <5 × 10−4 refractive index units (RIU). We further demonstrate a novel strategy for amplifying the sensing signal by coating the plasmonic substrate with a metal−organic framework (MOF) material. Cu3(BTC)2(H2O)3, BTC = benzenetricarboxylate, was grown on Ag nanoparticles using a layer-by-layer method in order to control the MOF thickness, which we show greatly affects the sensor response. Preferential concentration of CO2 within the MOF pores produces a 14-fold signal enhancement for CO2 sens...

Journal ArticleDOI
TL;DR: It is shown that the polarization sensitivity of the plasmonic vortex lens can be utilized for the dynamic switching of the surface Plasmon vortices with different topological charges.
Abstract: The generation of surface plasmon vortices with arbitrary higher order vortex topological charges with novel plasmonic vortex lens is experimentally demonstrated. It is shown that the polarization sensitivity of the plasmonic vortex lens can be utilized for the dynamic switching of the surface plasmon vortices with different topological charges. A simple algebraic rule related to the vortex topological charge change in the dynamic switching is formulated, and its proof is provided with theory and experiment. The synthesis and dynamic switching of higher order surface plasmon vortices have profound potential in optical trapping, optical data storage, and other related fields.

Journal ArticleDOI
13 Oct 2010-ACS Nano
TL;DR: Gold nanostars provide high sensitivity for single nanoparticle label-free biosensing and Streptavidin molecules are detected upon binding to individual, biotin-modified gold nanostar molecules by spectral shifts in the plasmon resonances.
Abstract: Gold nanostars provide high sensitivity for single nanoparticle label-free biosensing. The nanostars present multiple plasmon resonances of which the lower energy ones, corresponding to the nanostar tips and core−tip interactions, are the most sensitive to environmental changes. Streptavidin molecules are detected upon binding to individual, biotin-modified gold nanostars by spectral shifts in the plasmon resonances. Concentrations as low as 0.1 nM produce a shift of the tip related plasmon resonances of about 2.3 nm (5.3 meV).

Journal ArticleDOI
TL;DR: In this paper, single-particle structure-property measurements, coupled with a statistical analysis and FDTD calculations, are performed on silver and gold nanocubes, and the dependencies of LSPR frequencies on nanocube size, composition, and substrate dielectric constant are determined.
Abstract: Localized surface plasmon resonances (LSPRs), resulting from the interaction of light with metal nanoparticles, are powerful tools for biological sensors, surface-enhanced spectroscopies, and optical devices. LSPR frequencies are strongly dependent on a nanoparticle’s structure, composition, and local dielectric environment. However, these relationships are prohibitively difficult or impossible to probe from bulk solutions due to the heterogeneity of chemically synthesized products. In this study, systematic single-particle structure−property measurements, coupled with a statistical analysis and FDTD calculations, are performed on silver and gold nanocubes. The dependencies of LSPR frequencies on nanocube size, composition, and substrate dielectric constant are determined. The results obtained represent the most quantitative measurements and analysis to date, yielding predictive rules and fundamental insights into the interactions between nanoparticles and substrates.

Journal ArticleDOI
29 Apr 2010-ACS Nano
TL;DR: A surface-enhanced Raman scattering (SERS) substrate with plasmon resonances at both excitation and Stokes frequencies is reported, which combines localized surface plasmons on the nanoparticles with surface plAsmon polaritons excited on a gold film.
Abstract: We report a surface-enhanced Raman scattering (SERS) substrate with plasmon resonances at both excitation and Stokes frequencies. This multilayer structure combines localized surface plasmons on the nanoparticles with surface plasmon polaritons excited on a gold film. The largest SERS enhancement factor for a gold device is measured to be 7.2 x 10(7), which is more than 2 orders of magnitude larger than that measured on a gold nanoparticle array on a glass substrate. The largest SERS enhancement for a silver device is measured to be 8.4 x 10(8).

Journal ArticleDOI
12 Mar 2010-Science
TL;DR: It is shown that optical measurements of surface plasmon resonances can be used as a less disruptive way of determining the concentration of electrochemically active species on gold-coated glass slides and their current density.
Abstract: We demonstrated an electrochemical microscopy technique based on the detection of variations in local electrochemical current from optical signals arising from surface plasmon resonance. It enables local electrochemical measurements (such as voltammetry and amperometry) with high spatial resolution and sensitivity, because the signal varies with current density rather than current. The imaging technique is noninvasive, scanning-free, and fast, and it constitutes a powerful tool for studying heterogeneous surface reactions and for analyzing trace chemicals.