Showing papers on "Plasmon published in 2003"
TL;DR: In this paper, the authors describe recent progress in the theory of nanoparticle optical properties, particularly methods for solving Maxwell's equations for light scattering from particles of arbitrary shape in a complex environment.
Abstract: The optical properties of metal nanoparticles have long been of interest in physical chemistry, starting with Faraday's investigations of colloidal gold in the middle 1800s. More recently, new lithographic techniques as well as improvements to classical wet chemistry methods have made it possible to synthesize noble metal nanoparticles with a wide range of sizes, shapes, and dielectric environments. In this feature article, we describe recent progress in the theory of nanoparticle optical properties, particularly methods for solving Maxwell's equations for light scattering from particles of arbitrary shape in a complex environment. Included is a description of the qualitative features of dipole and quadrupole plasmon resonances for spherical particles; a discussion of analytical and numerical methods for calculating extinction and scattering cross-sections, local fields, and other optical properties for nonspherical particles; and a survey of applications to problems of recent interest involving triangula...
9,086 citations
TL;DR: A simple and intuitive picture that describes the plasmon response of complex nanostructures of arbitrary shape is presented, an electromagnetic analog of molecular orbital theory, that can be understood as the interaction or "hybridization" of elementary plasmons supported by nanostructure of elementary geometries.
Abstract: We present a simple and intuitive picture, an electromagnetic analog of molecular orbital theory, that describes the plasmon response of complex nanostructures of arbitrary shape. Our model can be understood as the interaction or "hybridization" of elementary plasmons supported by nanostructures of elementary geometries. As an example, the approach is applied to the important case of a four-layer concentric nanoshell, where the hybridization of the plasmons of the inner and outer nanoshells determines the resonant frequencies of the multilayer nanostructure.
3,587 citations
TL;DR: Observations of electromagnetic energy transport from a localized subwavelength source to a localized detector over distances of about 0.5 μm in plasmon waveguides consisting of closely spaced silver rods are presented.
Abstract: Achieving control of light-material interactions for photonic device applications at nanoscale dimensions will require structures that guide electromagnetic energy with a lateral mode confinement below the diffraction limit of light. This cannot be achieved by using conventional waveguides or photonic crystals. It has been suggested that electromagnetic energy can be guided below the diffraction limit along chains of closely spaced metal nanoparticles that convert the optical mode into non-radiating surface plasmons. A variety of methods such as electron beam lithography and self-assembly have been used to construct metal nanoparticle plasmon waveguides. However, all investigations of the optical properties of these waveguides have so far been confined to collective excitations and direct experimental evidence for energy transport along plasmon waveguides has proved elusive. Here we present observations of electromagnetic energy transport from a localized subwavelength source to a localized detector over distances of about 0.5 μm in plasmon waveguides consisting of closely spaced silver rods. The waveguides are excited by the tip of a near-field scanning optical microscope, and energy transport is probed by using fluorescent nanospheres.
2,305 citations
TL;DR: It is demonstrated that the previously described photoinduced method for converting silver nanospheres into triangular silver nanocrystals—so-called nanoprisms—can be extended to synthesize relatively monodisperse nanoprism with desired edge lengths in the 30–120 nm range.
Abstract: Inorganic nanoparticles exhibit size-dependent properties that are of interest for applications ranging from biosensing and catalysis to optics and data storage. They are readily available in a wide variety of discrete compositions and sizes. Shape-selective synthesis strategies now also yield shapes other than nanospheres, such as anisotropic metal nanostructures with interesting optical properties. Here we demonstrate that the previously described photoinduced method for converting silver nanospheres into triangular silver nanocrystals--so-called nanoprisms--can be extended to synthesize relatively monodisperse nanoprisms with desired edge lengths in the 30-120 nm range. The particle growth process is controlled using dual-beam illumination of the nanoparticles, and appears to be driven by surface plasmon excitations. We find that, depending on the illumination wavelengths chosen, the plasmon excitations lead either to fusion of nanoprisms in an edge-selective manner or to the growth of the nanoprisms until they reach their light-controlled final size.
1,585 citations
TL;DR: In this article, the authors investigate the coupling between pairs of elliptical metal particles by simulations and experiments and demonstrate that the resonant wavelength peak of two interacting particles is red-shifted from that of a single particle because of near-field coupling.
Abstract: The collaborative oscillation of conductive electrons in metal nanoparticles results in a surface plasmon resonance that makes them useful for various applications including biolabeling. We investigate the coupling between pairs of elliptical metal particles by simulations and experiments. The results demonstrate that the resonant wavelength peak of two interacting particles is red-shifted from that of a single particle because of near-field coupling. It is also found that the shift decays approximately exponentially with increasing particle spacing and become negligible when the gap between the two particles exceeds about 2.5 times the particle short-axis length.
1,492 citations
TL;DR: In this paper, the authors describe recent progress in the theory of nanoparticle optical properties, particularly methods for solving Maxwell's equations for light scattering from particles of arbitrary shape in a complex environment.
Abstract: The optical properties of metal nanoparticles have long been of interest in physical chemistry, starting with Faraday's investigations of colloidal gold in the middle 1800s. More recently, new lithographic techniques as well as improvements to classical wet chemistry methods have made it possible to synthesize noble metal nanoparticles with a wide range of sizes, shapes, and dielectric environments. In this feature article, we describe recent progress in the theory of nanoparticle optical properties, particularly methods for solving Maxwell's equations for light scattering from particles of arbitrary shape in a complex environment. Included is a description of the qualitative features of dipole and quadrupole plasmon resonances for spherical particles; a discussion of analytical and numerical methods for calculating extinction and scattering cross-sections, local fields, and other optical properties for nonspherical particles; and a survey of applications to problems of recent interest involving triangula...
1,416 citations
TL;DR: In this review, some of the properties of individual and some assembled metallic nanoparticles with a focus on their interaction with cw and pulsed laser light of different energies are discussed.
Abstract: Noble metal particles have long fascinated scientists because of their intense color, which led to their application in stained glass windows as early as the Middle Ages. The recent resurrection of colloidal and cluster chemistry has brought about the strive for new materials that allow a bottoms-up approach of building improved and new devices with nanoparticles or artificial atoms. In this review, we discuss some of the properties of individual and some assembled metallic nanoparticles with a focus on their interaction with cw and pulsed laser light of different energies. The potential application of the plasmon resonance as sensors is discussed.
1,327 citations
TL;DR: The optical response of ring-shaped gold nanoparticles prepared by colloidal lithography is investigated and the electric field associated with these plasmons exhibits uniform enhancement and polarization in the ring cavity, suggesting applications in near-infrared surface-enhanced spectroscopy and sensing.
Abstract: The optical response of ring-shaped gold nanoparticles prepared by colloidal lithography is investigated. Compared to solid gold particles of similar size, nanorings exhibit a redshifted localized surface plasmon that can be tuned over an extended wavelength range by varying the ratio of the ring thickness to its radius. The measured wavelength variation is well reproduced by numerical calculations and interpreted as originating from coupling of dipolar modes at the inner and outer surfaces of the nanorings. The electric field associated with these plasmons exhibits uniform enhancement and polarization in the ring cavity, suggesting applications in near-infrared surface-enhanced spectroscopy and sensing.
1,037 citations
TL;DR: In this article, the central role of the Ag femtosecond radiative lifetime and the spatial distribution of the excited Ag electrons, in the near field and far field optical properties is discussed.
Abstract: Molecular surface enhanced Raman scattering (SERS) in compact clusters of 30−70 nm Ag nanocrystals has shown single molecule Raman scattering cross sections that are orders of magnitude larger than free space single molecule luminescence cross sections. We analyze certain aspects of this phenomenon with new numerical electromagnetic calculations, and we also present new spectral depolarization data for single molecule rhodamine 6G scattering. We stress the central role of the Ag femtosecond radiative lifetime, and the spatial distribution of the excited Ag electrons, in the near field and far field optical properties. The fundamental nature of the Ag plasmon excited-electronic-state changes from a volume excitation to a surface junction excitation as two particles approach each other within 1 nm. Adsorbed molecules in the junction interact directly with the metallic excited-state wave function, showing electron-transfer-initiated photochemistry as well as enhanced Raman scattering. Depolarization studies ...
816 citations
TL;DR: In this article, a systematic study of surface-enhanced Raman-scattering (SERS) properties of nanosphere lithography (NSL) derived Ag nanoparticles is presented, which demonstrates the necessity of correlating nanoparticle structure and localized surface plasmon resonance (LSPR) spectroscopic data in order to effectively implement SERS on nanofabricated surfaces.
Abstract: This work presents the first systematic study of the surface-enhanced Raman-scattering (SERS) properties of nanosphere lithography (NSL) derived Ag nanoparticles. Furthermore, it demonstrates the necessity of correlating nanoparticle structure and localized surface plasmon resonance (LSPR) spectroscopic data in order to effectively implement SERS on nanofabricated surfaces that have narrow (∼100 nm) LSPR line widths. Using nanoparticle substrates that are structurally well characterized by atomic force microscopy, the relationship between the LSPR extinction maximum (λmax) and the SERS enhancement factor (EF) is explored in detail using the innovative approach of plasmon-sampled surface-enhanced Raman excitation spectroscopy (PS-SERES). PS-SERES studies were performed as a function of excitation wavelength, molecular adsorbate, vibrational band, and molecule-localized resonance or nonresonance excitation. In each case, high S/N ratio spectra are achieved for samples with an LSPR λmax within a ∼120-nm wind...
687 citations
TL;DR: Evidence of a full one-dimensional photonic band gap in resonant plasmon-waveguide structures is shown, providing an efficient tool for photonicBand gap engineering in metallodielectric photonic crystal slabs.
Abstract: Strong coupling between localized particle plasmons and optical waveguide modes leads to drastic modifications of the transmission of metallic nanowire arrays on dielectric waveguide substrates. The coupling results in the formation of a new quasiparticle, a waveguide-plasmon polariton, with a surprisingly large Rabi splitting of 250 meV. Our experimental results agree well with scattering-matrix calculations and a polariton-type model. The effect provides an efficient tool for photonic band gap engineering in metallodielectric photonic crystal slabs. We show evidence of a full one-dimensional photonic band gap in resonant plasmon-waveguide structures.
TL;DR: Two experimental techniques are used; namely, the mechanically controllable break-junction technique to measure electronic transport, and UV/Vis spectroscopy to measure absorption of photochromic molecular switches that are self-assembled on gold.
Abstract: We investigate photochromic molecular switches that are self-assembled on gold. We use two experimental techniques; namely, the mechanically controllable break-junction technique to measure electronic transport, and UV/Vis spectroscopy to measure absorption. We observe switching of the molecules from the conducting to the insulating state when illuminated with visible light (lambda=546 nm), in spite of the gold surface plasmon absorption present around this wavelength. However, we fail to observe the reverse process which should occur upon illumination with UV light (lambda=313 nm). We attribute this to quenching of the excited state of the molecule in the open form by the presence of gold.
TL;DR: In this article, the photoreduction of silver ions by citrate, catalyzed on silver seeds, is used to synthesize disk-shaped silver nanoparticles in solution, characterized by transmission electron microscopy (TEM), atomic force microscopy, optical absorption spectroscopy, and by measuring the silver ion concentration during the reaction.
Abstract: The photoreduction of silver ions by citrate, catalyzed on silver seeds, is used to synthesize disk-shaped silver nanoparticles in solution. The reaction is characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), optical absorption spectroscopy, and by measuring the silver ion concentration during the reaction. The irradiation wavelength determines the final shape of these particles due to the shape dependence of the Ag plasmon spectrum. The quantum yield of this reaction has been calculated, and a growth mechanism is outlined.
TL;DR: In this paper, surface plasmon polaritonic crystals and their role in the determination of optical properties of periodically nanostructured metal films are described, and nonlinear effects related to surface polaritons and localized surface plasmons allowing control of the optical properties with light are discussed.
Abstract: Surface plasmon polaritons and localized surface plasmons are discussed in the context of photonic applications. Near-field imaging of scattering, reflection, interference and localization of surface polaritons is reviewed, and approaches for the implementation of elements of surface polariton optics are presented. Surface plasmon polaritonic crystals and their role in the determination of optical properties of periodically nanostructured metal films are described. Non-linear effects related to surface polaritons and localized surface plasmons allowing control of optical properties of nanostructured metal films with light are discussed. Surface plasmon optics opens up numerous possibilities for application of these intrinsically two-dimensional excitations in passive and active devices of all-optical integrated circuits.
01 Jan 2003
TL;DR: In this paper, the size and shape effects in surface plasmon resonance have been studied and a growth mechanism was proposed for Ag particle growth from adsorbed Ag silver ions in the presence of citrate.
Abstract: The photoreduction of silver ions by citrate, catalyzed on silver seeds, is used to synthesize disk-shaped silver nanoparticles in solution. The reaction is characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), optical absorption spectroscopy, and by measuring the silver ion concentration during the reaction. The irradiation wavelength determines the final shape of these particles due to the shape dependence of the Ag plasmon spectrum. The quantum yield of this reaction has been calculated, and a growth mechanism is outlined. Introduction. Silver particles provide an ideal system for study of size and shape effects in the surface plasmon resonance; indeed, this sensitivity is a tool to monitor the shape of the particles during their synthesis via the optical extinction spectrum. Plasmon resonances concentrate an incident electromagnetic field via near-field enhancement; this antenna effect is the source of surface enhanced Raman scattering (SERS). The intense Ag resonance allows single molecule observation in SERS, 1-5 enables coupled Ag particles to form a subwavelength waveguide, 6 and enables sensitive colorimetric DNA screening. 7,8 Henglein 9,10 has shown that the physical and chemical properties of finely divided, nm-sized Ag particles are strongly modified by the adsorption of nucleophilic species and that Ag particles catalyze thermal and optical electro- chemical reactions. For example, core/shell metallic particles can be grown. 11 Indeed, adsorption of chemical species modifies the Fermi level of both the metal and the reactant, like a polarized nanoelectrode. Combining these effects, we now report controlled pho- tochemical Ag particle growth from adsorbed Ag silver ions in the presence of citrate. If different shapes and sizes are present in a seed colloid, the particle with the largest plasmon absorption cross-section at the laser wavelength initially grows fastest. The reaction accelerates for those shapes whose plasmons move into resonance with the photochemical wavelength as growth occurs. This effect allows control of shape in the dominant photoproduct by choice of photo- chemical wavelength. There have been previous observations of reduced silver formation by irradiation of citrate and Ag ion, however, without control of shape or size. 12,13
TL;DR: In this article, a geometrical probability measure is proposed for calculating the effective conduction electron mean free path of an arbitrary shape convex particle, which is shown to be consistent with exact quantum mechanical widths for simple particle shapes.
Abstract: A geometrical probability measure is proposed for calculating the effective conduction electron mean free path of an arbitrary shape convex particle. It is shown that the plasmon widths determined from this mean free path are consistent with exact quantum mechanical widths for simple particle shapes. We use the mean free path formula to evaluate size and shape dependent dielectric functions and extinction spectra for silver spheroids, square prisms, truncated tetrahedrons, and cylinders.
TL;DR: The presented type of biosensing can be a cost-effective and easy to use alternative to conventional biosensing techniques, and also the interband absorption of the particles changes, will be demonstrated.
Abstract: The absorption spectrum of noble metal spherical nanoparticles is known to be strongly influenced by the dielectric constant of the surrounding material, and as such, these particles are well suited for biosensing applications. To perform biosensing using nanoparticles on a substrate, the metal particles are covalently attached onto quartz using an organic adhesion layer of mercaptosilanes. The particles in solution are characterized by UV-vis spectroscopy and transmission electron microscopy, while those attached to the quartz are characterized with UV-vis spectroscopy and atomic force microscopy. Antibodies are attached to the metal nanoparticles, and the antigen recognition is monitored via the change of light absorption when this binding event occurs. Not only is the absorbance originating from plasmon resonances of the particles influenced by the dielectric properties of molecules attached to the nanospheres but also the interband absorption of the particles changes, which will be demonstrated in this report. A light absorption change is detected when a molecular recognition occurs between the bioreceptor molecules attached to the nanoparticle and a biomolecular counterpart. This change in absorption can be very large when adhered molecules are at resonance (interband transitions). In addition, the presented type of biosensing can be a cost-effective and easy to use alternative to conventional biosensing techniques.
TL;DR: Ultra-bright plasmon resonant particle conjugates, and the automation of PRP identification, discrimination, and counting, have enabled the development of ultrasensitive, multicolor, and multiplex applications in the life science field.
TL;DR: In this paper, three-dimensional numerical simulations have been performed for the H-plane and E-plane optical circuits that consist of straight and branched bend SPGWs.
Abstract: Nanometric optical waveguides can be made by using the dependence of surface plasmon polaritons on the gap-width between two parallel metallic plates. This waveguide can be called surface plasmon polariton gap waveguide (SPGW). The H-plane and E-plane optical circuits that consist of SPGWs have been considered. Three-dimensional numerical simulations have been performed for the nanometric optical circuits that consist of straight and branched bend SPGWs. Results show that optical circuits considered in this letter can perform guiding, branching, and bending functions of optical waves in the nanometric device.
TL;DR: In this paper, surface plasmon modes on silver and gold nanowires of a fixed cross section and different lengths, produced by electron beam lithography were determined by extinction spectroscopy and can be interpreted in terms of standing Plasmon polariton waves.
Abstract: We have studied surface plasmon modes on silver and gold nanowires of a fixed cross section and different lengths, produced by electron beam lithography. The optically excited modes are determined by extinction spectroscopy and can be interpreted in terms of standing plasmon polariton waves. The eigenfrequencies are found to follow a dispersion relation similar to that for a planar metal/dielectric interface.
TL;DR: It is shown that a composite of nanowires arranged into parallel pairs can act as a left-handed material with the effective magnetic permeability and dielectric permittivity both negative in the visible and near-infrared spectral ranges.
Abstract: Optical properties of metal nanowires and nanowire composite materials are studied. An incident electromagnetic wave can effectively couple to the propagating surface plasmon polariton (SPP) modes in metal nanowires resulting in very large local fields. The excited SPP modes depend on the structure of nanowires and their orientation with respect to incident radiation. A nanowire percolation composite is shown to have a broadband spectrum of localized plasmon modes. We also show that a composite of nanowires arranged into parallel pairs can act as a left-handed material with the effective magnetic permeability and dielectric permittivity both negative in the visible and near-infrared spectral ranges.
TL;DR: Using the TDLDA method, this paper investigated how the polarizability of the d electrons of the gold atoms influences the electronic and optical properties of metallic nanoshells and showed that a polarizable jellium background can introduce a significant shift of the plasmon resonances.
Abstract: Using the TDLDA method, we investigate how the polarizability of the d electrons of the gold atoms influences the electronic and optical properties of metallic nanoshells. It is shown that a polarizable jellium background can introduce a significant shift of the plasmon resonances. The results of the study show that the theoretically calculated optical absorption spectra for gold nanoshells with a gold sulfide core are in excellent agreement with experimental data.
TL;DR: A novel method for detection of noble-metal nanoparticles by their nonlinear optical properties is presented and applied for specific labeling of cellular organelles and membranes.
Abstract: A novel method for detection of noble-metal nanoparticles by their nonlinear optical properties is presented and applied for specific labeling of cellular organelles. When illuminated by laser light in resonance with their plasmon frequency these nanoparticles generate an enhanced multiphoton signal. This enhanced signal is measured to obtain a depth-resolved image in a laser scanning microscope setup. Plasmon-resonance images of both live and fixed cells, showing specific labeling of cellular organelles and membranes, either by two-photon autofluorescence or by third-harmonic generation, are presented.
TL;DR: It is shown that a Rayleigh-like scattering of surface plasmons by the periodic hole array is the microscopic origin of this damping, allowing the reradiation rate to be controlled.
Abstract: We report spatial domain measurements of the damping of surface-plasmon excitations in metal films with periodic nanohole arrays. The measurements reveal a short coherent propagation length of a few $\ensuremath{\mu}\mathrm{m}$ inside nanohole arrays, consistent with delays of about 10 fs in ultrafast transmission experiments. This implies that the transmission spectra of the entire plasmonic band-gap structure are homogeneously broadened by radiative damping of surface-plasmon excitations. We show that a Rayleigh-like scattering of surface plasmons by the periodic hole array is the microscopic origin of this damping, allowing the reradiation rate to be controlled.
TL;DR: In this article, the authors investigated the tunability of the optical polarizability of small metallic nanoshells using the time-dependent LDA method and showed that the energies of the two dipolar plasmon resonances vary with the ratio of shell thickness to particle radius in a manner similar to what has been predicted using classical Mie scattering and semiclassical models for uniform metallic shell structures.
Abstract: Using the time-dependent LDA method, we investigate the tunability of the optical polarizability of small metallic nanoshells. We show that the energies of the two dipolar plasmon resonances vary with the ratio of shell thickness to particle radius in a manner similar to what has been predicted using classical Mie scattering and semiclassical models for uniform metallic shell structures.
TL;DR: Silver nanoparticles arranged in two-dimensional arrays experience quadrupolar coupling of plasmon resonances when irradiated with visible light that exemplifies a generic approach in which new optical properties of materials can be engineered by organizing metal nanoparticles in various one-, two-, and three-dimensional structures.
Abstract: Silver nanoparticles arranged in two-dimensional arrays experience quadrupolar coupling of plasmon resonances when irradiated with visible light. This coupling leads to the formation of the coherent plasmon mode characterized by an intense narrow resonance in the blue spectral range in the extinction spectrum. The coupling and the intensity of this mode can be effectively controlled by varying the distance between particles. The interparticle distance was varied by biaxial stretching of the arrays prepared in transparent elastomeric film of poly(dimethylsiloxane). The observed phenomenon exemplifies a generic approach in which new optical properties of materials can be engineered by organizing metal nanoparticles in various one-, two-, and three-dimensional structures. Further development of this approach will result in the discovery of novel principles of both fundamental and practical importance.
TL;DR: In this paper, the authors studied in the near-field the launching of surface plasmons in a well-defined direction by micro-arrays of subwavelength holes milled in a thick metal film.
Abstract: Controlling separately the launching of surface plasmons and their recovery as freely propagating light is essential for the development of surface plasmon photonic circuits. With this target in mind, we have studied in the near-field the launching of surface plasmons in a well-defined direction by micro-arrays of subwavelength holes milled in a thick metal film. We show that surface plasmons can then be converted back to freely propagating light by means of another appropriately designed array. These results not only provide insight into the efficient decoupling of surface plasmons but also into their role in the enhanced transmission mechanism.
TL;DR: In this article, a two-dimensional cubic lattice consisting of thin metal wires, having wire diameter of 30 μm, lattice constant of 120 μm and wire length of 1 mm, was constructed using microstereolithography.
Abstract: Metamaterials, which contain engineered subwavelength microstructures, can be designed to have positive or negative e and μ at desired frequencies. In this letter, we demonstrate a metamaterial which has a “plasmonic” response to electromagnetic waves in the terahertz (THz) range. The sharp change of reflection and transmission at this plasma frequency makes the structure a high pass filter. The reflection response is characterized by Fourier transform infrared spectroscopy, and a plasma frequency at 0.7 THz is observed, which agrees with the theoretical calculation. The metamaterial is a two-dimensional cubic lattice consisting of thin metal wires, having wire diameter of 30 μm, lattice constant of 120 μm, and wire length of 1 mm. The microstereolithography technique is employed to fabricate the high-aspect-ratio lattice.
TL;DR: Replacing the hole array by a continuous metallic film, it is shown that resonant extraordinary transmission can still occur, provided the film is modulated.
Abstract: Using a rigorous electromagnetic analysis of two-dimensional (or crossed) gratings, we account, in a first step, for the enhanced transmission of a sub-wavelength hole array pierced inside a metallic film, when plasmons are simultaneously excited at both interfaces of the film. Replacing the hole array by a continuous metallic film, we then show that resonant extraordinary transmission can still occur, provided the film is modulated. The modulation may be produced in both a one-dimensional and a two dimensional geometry either by periodic surface deformation or by adding an array of high index pillars. Transmittivity higher than 80% is found when surface plasmons are excited at both interfaces, in a symmetric configuration.
TL;DR: Calculations show that a radially polarized waveguide mode can create a strong field enhancement localized at the apex of the tip that forms a nanoscale optical near‐field source.
Abstract: Near the cut-off radius of a guided waveguide mode of a metal-coated glass fibre tip it is possible to couple radiation to surface plasmons propagating on the outside surface of the metal coating. These surface plasmons converge toward the apex of the tip and interfere constructively for particular polarization states of the initial waveguide mode. Calculations show that a radially polarized waveguide mode can create a strong field enhancement localized at the apex of the tip. The highly localized enhanced field forms a nanoscale optical near-field source.