The Optical Properties of Metal Nanoparticles: The Influence of Size, Shape, and Dielectric Environment
23 Jan 2003-Journal of Physical Chemistry B (American Chemical Society)-Vol. 107, Iss: 3, pp 668-677
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...
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TL;DR: This review describes recent fundamental spectroscopic studies that reveal key relationships governing the LSPR spectral location and its sensitivity to the local environment, including nanoparticle shape and size and introduces a new form of L SPR spectroscopy, involving the coupling between nanoparticle plasmon resonances and adsorbate molecular resonances.
Abstract: Localized surface plasmon resonance (LSPR) spectroscopy of metallic nanoparticles is a powerful technique for chemical and biological sensing experiments. Moreover, the LSPR is responsible for the electromagnetic-field enhancement that leads to surface-enhanced Raman scattering (SERS) and other surface-enhanced spectroscopic processes. This review describes recent fundamental spectroscopic studies that reveal key relationships governing the LSPR spectral location and its sensitivity to the local environment, including nanoparticle shape and size. We also describe studies on the distance dependence of the enhanced electromagnetic field and the relationship between the plasmon resonance and the Raman excitation energy. Lastly, we introduce a new form of LSPR spectroscopy, involving the coupling between nanoparticle plasmon resonances and adsorbate molecular resonances. The results from these fundamental studies guide the design of new sensing experiments, illustrated through applications in which researchers use both LSPR wavelength-shift sensing and SERS to detect molecules of chemical and biological relevance.
5,444 citations
TL;DR: It is found that, after exposure to continuous red laser at 800 nm, malignant cells require about half the laser energy to be photothermally destroyed than the nonmalignant cells, so both efficient cancer cell diagnostics and selective photothermal therapy are realized at the same time.
Abstract: Due to strong electric fields at the surface, the absorption and scattering of electromagnetic radiation by noble metal nanoparticles are strongly enhanced. These unique properties provide the potential of designing novel optically active reagents for simultaneous molecular imaging and photothermal cancer therapy. It is desirable to use agents that are active in the near-infrared (NIR) region of the radiation spectrum to minimize the light extinction by intrinsic chromophores in native tissue. Gold nanorods with suitable aspect ratios (length divided by width) can absorb and scatter strongly in the NIR region (650−900 nm). In the present work, we provide an in vitro demonstration of gold nanorods as novel contrast agents for both molecular imaging and photothermal cancer therapy. Nanorods are synthesized and conjugated to anti-epidermal growth factor receptor (anti-EGFR) monoclonal antibodies and incubated in cell cultures with a nonmalignant epithelial cell line (HaCat) and two malignant oral epithelial ...
5,047 citations
TL;DR: A comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals, including a brief introduction to nucleation and growth within the context of metal Nanocrystal synthesis, followed by a discussion of the possible shapes that aMetal nanocrystal might take under different conditions.
Abstract: Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. Our aim is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Finally, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take.
4,927 citations
TL;DR: Plasmon-enhanced water splitting on composite photocatalysts containing semiconductor and plasmonic-metal building blocks is focused on, and recently reported plasMon-mediated photocatallytic reactions on plAsmonic nanostructures of noble metals are discussed.
Abstract: Recent years have seen a renewed interest in the harvesting and conversion of solar energy. Among various technologies, the direct conversion of solar to chemical energy using photocatalysts has received significant attention. Although heterogeneous photocatalysts are almost exclusively semiconductors, it has been demonstrated recently that plasmonic nanostructures of noble metals (mainly silver and gold) also show significant promise. Here we review recent progress in using plasmonic metallic nanostructures in the field of photocatalysis. We focus on plasmon-enhanced water splitting on composite photocatalysts containing semiconductor and plasmonic-metal building blocks, and recently reported plasmon-mediated photocatalytic reactions on plasmonic nanostructures of noble metals. We also discuss the areas where major advancements are needed to move the field of plasmon-mediated photocatalysis forward.
4,074 citations
Cites background from "The Optical Properties of Metal Nan..."
...It was also demonstrated that these reactions exhibited distinct signatures of energetic electron-induced chemical reactions on metals (that is, the reactions initiated by transfer of high-energy electrons from the metal to the reactant), including: (1) the linear dependence of the reaction rate on light intensity69,71,74; (2) larger kinetic isotope effects compared with the reaction driven using only thermal energy source (that is, the phonon-driven counterparts)70,75,76; and (3) different product selectivity for the reactions induced by the thermal flux compared with the same chemical transformation induced by a photon source68,69....
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...Although this co-catalyst/semiconductor class exhibits improved performance compared with semiconductor photocatalysts, this approach does not address the problems of: (1) very diffuse solar flux; (2) absorption limited to only high-energy photons in many inexpensive and abundant semiconductors (for example, TiO2); and (3) large discrepancy in photon penetration depths (a few nanometres to micrometres) and minority charge-carrier diffusion length (a few nanometres) encountered by many promising semiconductors....
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...As well as affordability and robustness, efficient photocatalysts need to: (1) absorb photons across the UV-vis region of the solar spectrum and convert these into electron–hole pairs; (2) allow for a facile separation of electron– hole pairs and their transport to the liquid/semiconductor junction where the half-reactions are performed; (3) have surface electronic structure tailored so that the half-reactions are thermodynamically feasible (product state in each half-reaction needs to have a lower free energy than the reactant state); and (4) possess high catalytic activity, that is, have surface sites that allow for the half-reactions to be performed with low activation barriers....
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TL;DR: While nanorods with a higher aspect ratio along with a smaller effective radius are the best photoabsorbing nanoparticles, the highest scattering contrast for imaging applications is obtained from nanorod of high aspect ratio with a larger effective radius.
Abstract: The selection of nanoparticles for achieving efficient contrast for biological and cell imaging applications, as well as for photothermal therapeutic applications, is based on the optical properties of the nanoparticles. We use Mie theory and discrete dipole approximation method to calculate absorption and scattering efficiencies and optical resonance wavelengths for three commonly used classes of nanoparticles: gold nanospheres, silica−gold nanoshells, and gold nanorods. The calculated spectra clearly reflect the well-known dependence of nanoparticle optical properties viz. the resonance wavelength, the extinction cross-section, and the ratio of scattering to absorption, on the nanoparticle dimensions. A systematic quantitative study of the various trends is presented. By increasing the size of gold nanospheres from 20 to 80 nm, the magnitude of extinction as well as the relative contribution of scattering to the extinction rapidly increases. Gold nanospheres in the size range commonly employed (∼40 nm)...
4,065 citations
References
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12 Jul 1985
TL;DR: In this paper, E.D. Palik and R.R. Potter, Basic Parameters for Measuring Optical Properties, and W.W.Hunter, Measurement of Optical Constants in the Vacuum Ultraviolet Spectral Region.
Abstract: VOLUME ONE: Determination of Optical Constants: E.D. Palik, Introductory Remarks. R.F. Potter, Basic Parameters for Measuring Optical Properties. D.Y. Smith, Dispersion Theory, Sum Rules, and Their Application to the Analysis of Optical Data. W.R. Hunter, Measurement of Optical Constants in the Vacuum Ultraviolet Spectral Region. D.E. Aspnes, The Accurate Determination of Optical Properties by Ellipsometry. J. Shamir, Interferometric Methods for the Determination of Thin-Film Parameters. P.A. Temple, Thin-Film Absorplance Measurements Using Laser Colorimetry. G.J. Simonis, Complex Index of Refraction Measurements of Near-Millimeter Wavelengths. B. Jensen, The Quantum Extension of the Drude--Zener Theory in Polar Semiconductors. D.W. Lynch, Interband Absorption--Mechanisms and Interpretation. S.S. Mitra, Optical Properties of Nonmetallic Solids for Photon Energies below the Fundamental Band Gap. Critiques--Metals: D.W. Lynch and W.R. Hunter, Comments of the Optical Constants of Metals and an Introduction to the Data for Several Metals. D.Y. Smith, E. Shiles, and M. Inokuti, The Optical Properties of Metallic Aluminum. Critiques--Semiconductors: E.D. Palik, Cadium Telluride (CdTe). E.D. Palik, Gallium Arsenide (GaAs). A. Borghesi and G. Guizzetti, Gallium Phosphide (GaP). R.F. Potter, Germanium (Ge). E.D. Palik and R.T. Holm, Indium Arsenide (InAs). R.T. Holm, Indium Antimonide (InSb). O.J. Glembocki and H. Piller, Indium Phosphide (InP). G. Bauer and H. Krenn, Lead Selenide (PbSe). G. Guizzetti and A. Borghesi, Lead Sulfide (PbS). G. Bauer and H. Krenn, Lead Telluride (PbTe). D.F. Edwards, Silicon (Si). H. Piller, Silicon (Amorphous) (-Si). W.J. Choyke and E.D. Palik, Silicon Carbide (SiC). E.D. Palik and A. Addamiano, Zinc Sulfide (ZnS). Critiques--Insulators: D.J. Treacy, Arsenic Selenide (As 2 gt Se 3 gt ). D.J. Treacy, Arsenic Sulfide (As 2 gt S 3 gt ). D.F. Edwards and H.R. Philipp, Cubic Carbon (Diamond). E.D. Palik and W.R. Hunter, Litium Fluoride (LiF). E.D. Palik, Lithium Niobote (LiNbO 3 gt ). E.D. Palik, Potassium Chloride (KCl). H.R. Philipp, Silicon Dioxide (SiO 2 gt ), Type ( (Crystalline). H.R. Philipp, Silicon Dioxide (SiO 2 gt ) (Glass). gt H.R. Philipp, Silicon Monoxide (SiO) (Noncrystalline). H.R. Philipp, Silicon Nitride (Si 3 gt N 4 gt ) (Noncrystalline). J.E. Eldridge and E.D. Palik, Sodium Chloride (NaCl). M.W. Ribarsky, Titanium Dioxide (TiO 2 gt ) (Rutile).
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Book•
01 Jan 1983
TL;DR: In this paper, a Potpourri of Particles is used to describe surface modes in small Particles and the Angular Dependence of Scattering is shown to be a function of the size of the particles.
Abstract: BASIC THEORY. Electromagnetic Theory. Absorption and Scattering by an Arbitrary Particle. Absorption and Scattering by a Sphere. Particles Small Compared with the Wavelength. Rayleigh--Gans Theory. Geometrical Optics. A Potpourri of Particles. OPTICAL PROPERTIES OF BULK MATTER. Classical Theories of Optical Constants. Measured Optical Properties. OPTICAL PROPERTIES OF PARTICLES. Extinction. Surface Modes in Small Particles. Angular Dependence of Scattering. A Miscellany of Applications. Appendices. References. Index.
16,859 citations
Book•
31 May 1995
TL;DR: This paper presents background history of space-grid time-domain techniques for Maxwell's equations scaling to very large problem sizes defense applications dual-use electromagnetics technology, and the proposed three-dimensional Yee algorithm for solving these equations.
Abstract: Part 1 Reinventing electromagnetics: background history of space-grid time-domain techniques for Maxwell's equations scaling to very large problem sizes defense applications dual-use electromagnetics technology. Part 2 The one-dimensional scalar wave equation: propagating wave solutions finite-difference approximation of the scalar wave equation dispersion relations for the one-dimensional wave equation numerical group velocity numerical stability. Part 3 Introduction to Maxwell's equations and the Yee algorithm: Maxwell's equations in three dimensions reduction to two dimensions equivalence to the wave equation in one dimension. Part 4 Numerical stability: TM mode time eigenvalue problem space eigenvalue problem extension to the full three-dimensional Yee algorithm. Part 5 Numerical dispersion: comparison with the ideal dispersion case reduction to the ideal dispersion case for special grid conditions dispersion-optimized basic Yee algorithm dispersion-optimized Yee algorithm with fourth-order accurate spatial differences. Part 6 Incident wave source conditions for free space and waveguides: requirements for the plane wave source condition the hard source total-field/scattered field formulation pure scattered field formulation choice of incident plane wave formulation. Part 7 Absorbing boundary conditions for free space and waveguides: Bayliss-Turkel scattered-wave annihilating operators Engquist-Majda one-way wave equations Higdon operator Liao extrapolation Mei-Fang superabsorption Berenger perfectly-matched layer (PML) absorbing boundary conditions for waveguides. Part 8 Near-to-far field transformation: obtaining phasor quantities via discrete fourier transformation surface equivalence theorem extension to three dimensions phasor domain. Part 9 Dispersive, nonlinear, and gain materials: linear isotropic case recursive convolution method linear gyrontropic case linear isotropic case auxiliary differential equation method, Lorentz gain media. Part 10 Local subcell models of the fine geometrical features: basis of contour-path FD-TD modelling the simplest contour-path subcell models the thin wire conformal modelling of curved surfaces the thin material sheet relativistic motion of PEC boundaries. Part 11 Explicit time-domain solution of Maxwell's equations using non-orthogonal and unstructured grids, Stephen Gedney and Faiza Lansing: nonuniform, orthogonal grids globally orthogonal global curvilinear co-ordinates irregular non-orthogonal unstructured grids analysis of printed circuit devices using the planar generalized Yee algorithm. Part 12 The body of revolution FD-TD algorithm, Thomas Jurgens and Gregory Saewert: field expansion difference equations for on-axis cells numerical stability PML absorbing boundary condition. Part 13 Modelling of electromagnetic fields in high-speed electronic circuits, Piket-May and Taflove. (part contents).
11,194 citations
10,184 citations
TL;DR: A method for assembling colloidal gold nanoparticles rationally and reversibly into macroscopic aggregates by using the specificity of DNA interactions to direct the interactions between particles of different size and composition is described.
Abstract: COLLOIDAL particles of metals and semiconductors have potentially useful optical, optoelectronic and material properties1–4 that derive from their small (nanoscopic) size. These properties might lead to applications including chemical sensors, spectro-scopic enhancers, quantum dot and nanostructure fabrication, and microimaging methods2–4. A great deal of control can now be exercised over the chemical composition, size and polydis-persity1,2 of colloidal particles, and many methods have been developed for assembling them into useful aggregates and materials. Here we describe a method for assembling colloidal gold nanoparticles rationally and reversibly into macroscopic aggregates. The method involves attaching to the surfaces of two batches of 13-nm gold particles non-complementary DNA oligo-nucleotides capped with thiol groups, which bind to gold. When we add to the solution an oligonucleotide duplex with 'sticky ends' that are complementary to the two grafted sequences, the nanoparticles self-assemble into aggregates. This assembly process can be reversed by thermal denaturation. This strategy should now make it possible to tailor the optical, electronic and structural properties of the colloidal aggregates by using the specificity of DNA interactions to direct the interactions between particles of different size and composition.
6,188 citations