Electromagnetic Mechanism of Surface‐Enhanced Spectroscopy

Schatz, George C.; Duyne, Richard P. Van

doi:10.1002/0470027320.s0601

Cited by 270 publications

(364 citation statements)

References 105 publications

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“…18,31 The enhancement from E local (ω S ) is much more difficult to model than from E local -(ω 0 ). 32 In fact, only for the limit of a small spherical particles that the expressions for E local (ω 0 ) and E local (ω S ) are similar, and the approximation E local (ω 0 ) ) E local (ω S ) is valid. 32 For more complex geometries, as the ones investigated in this work, these local fields are not expected to be the same, and they might not follow the same polarization dependence.…”

Section: Resultsmentioning

confidence: 99%

“…32 In fact, only for the limit of a small spherical particles that the expressions for E local (ω 0 ) and E local (ω S ) are similar, and the approximation E local (ω 0 ) ) E local (ω S ) is valid. 32 For more complex geometries, as the ones investigated in this work, these local fields are not expected to be the same, and they might not follow the same polarization dependence. It is also unlikely that the orientation of the emission dipole at ω S is the same as the polarizable dipole ω 0 .…”

Section: Resultsmentioning

confidence: 99%

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Strong Polarized Enhanced Raman Scattering via Optical Tunneling through Random Parallel Nanostructures in Au Thin Films

2004

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Random parallel nanostructures (ridges and channels) were created by scratching gold thin films deposited on glass slides. Atomic force microscope (AFM) images showed that the width of the substructures within the scratches were of the order of a few hundred nanometers. These nanometric gold features can then support localized surface plasmon resonances in the direction perpendicular to the propagation of the scratches. This surface plasmon excitation led to a remarkable dependence of the intensity of the surface-enhanced resonance Raman scattering (SERRS) on the polarization direction of the incident light relative to the orientation of the scratch. The maximum SERRS intensities for oxazine 720 (a common laser dye) adsorbed on these nanostructures were obtained when the polarization of the light field was perpendicular to the direction of the substructures. The SERRS intensities followed a squared dependence on the polarization direction of the incident field.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Strong Polarized Enhanced Raman Scattering via Optical Tunneling through Random Parallel Nanostructures in Au Thin Films

2004

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“…Excitation of the LSPR has two consequences: selective absorption and scattering of the resonant electromagnetic radiation, and generation of large electromagnetic fields at the surface of the roughness feature (Figures 1c-1e). Electromagnetic enhancement relies on Raman-active molecules being confined within these electromagnetic fields (17 ) and contributes an average enhancement factor of ≥10,000.…”

Section: Fundamental Theorymentioning

confidence: 99%

“…The simple example of an isolated sphere, with a quasistatic description of the incident electromagnetic field, has been used to derive the proportionality in which E is the electric field magnitude at the surface of the sphere, E 0 is the incident field magnitude, m is the wavelength-dependent dielectric constant of the metal composing the sphere, and 0 is the dielectric constant of the local environment around the sphere (17 ). This relation reveals that when m = −2 0 , which can be achieved for silver and gold at certain wavelengths in the visible and near-IR, the magnitude of the electric field at the surface of the sphere becomes very large.…”

Section: Fundamental Theorymentioning

confidence: 99%

Surface-Enhanced Raman Spectroscopy

Haynes¹,

McFarland²,

Duyne³

2005

Anal. Chem.

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1,077

855

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mekal theoretically predicted inelastic light scattering in 1923 (1). Raman and Krishnan first experimentally observed the phenomenon and reported in their 1928 Nature paper that the inelastic scattering effect was characterized by "its feebleness in comparison with the ordinary scattering" (2). This "feeble" phenomenon is now known as Raman scattering. The change in wavelength that is observed when a photon undergoes Raman scattering is attributed to the excitation (or relaxation) of vibrational modes of a molecule. Because different functional groups have different characteristic vibrational energies, every molecule has a unique Raman spectrum. In accordance with the Raman selection rule, the molecular polarizability changes as the molecular vibrations displace the constituent atoms from their equilibrium positions. The intensity of Raman scattering is proportional to the magnitude of the change in molecular polarizability. Thus, aromatic molecules exhibit more intense Raman scattering than aliphatic molecules.Even so, Raman scattering cross sections are typically 14 orders of magnitude smaller than those of fluorescence; therefore, the Raman signal is still several orders of magnitude weaker than the fluorescence emission in most cases. Because of the inherently small intensity of the Raman signal, the sensitivity limits of available detectors, and the intensity of the excitation sources, the applicability of Raman scattering was restricted for many years. However, its utility as an analytical technique improved with the advent of the laser and the evolution of photon detection technology.In 1977, Jeanmaire and Van Duyne demonstrated that the magnitude of the Raman scattering signal can be greatly enhanced when the scatterer is placed on or near a roughened noble-metal substrate (3). Strong electromagnetic fields are generated when the localized surface plasmon resonance (LSPR) of nanoscale roughness features on a silver, gold, or copper substrate is excited by visible light. When the Raman scatterer is subjected to these intensified electromagnetic fields, the magnitude of the induced dipole increases, and accordingly, the intensity of the inelastic scattering increases. This enhanced scattering process is known as surface-enhanced Raman (SER) scattering-a term that emphasizes the key role of the noblemetal substrate in this phenomenon.

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“…Many aspects of LSPR excitation can be described accurately with classical electromagnetic theory, which makes possible the use of theory to guide in the design of nanoparticle systems which deliver optimal response. From a practical perspective, the tunable optical properties of nanostructures make it possible to use these materials in surfaceenhanced spectroscopy, [10][11][12][13][14] optical filters, 15,16 plasmonic devices, [17][18][19][20] and sensors. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Until recently, there were only limited methods for the synthesis of monodisperse, nonspherical noble metal nanoparticles, which meant that the practical applications of these particles were limited.…”

Section: Introductionmentioning

confidence: 99%

Solution-Phase, Triangular Ag Nanotriangles Fabricated by Nanosphere Lithography

Haes¹,

Zhao²,

Zou³

et al. 2005

J. Phys. Chem. B

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112

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A novel method to produce solution-phase triangular silver nanoparticles is presented. Ag nanoparticles are prepared by nanosphere lithography and are subsequently released into solution. The resulting nanoparticles are asymmetrically functionalized to produce either single isolated nanoparticles or dimer pairs. The structural and optical properties of Ag nanoparticles have been characterized. Mie theory and the Discrete Dipole Approximation method (DDA) have been used to model and interpret the optical properties of the released Ag nanoparticles.

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Electromagnetic Mechanism of Surface‐Enhanced Spectroscopy

Abstract: The sections in this article are Introduction Electromagnetic Mechanism of Surface‐Enhanced R aman Spectroscopy for Isolated Metal Particles A simple Model: Quasistatic Treatment of an Isolated Sphere Electrostatics of Isolated Spheroids Improvements to the Spheroid Model … Show more

Cited by 270 publications

References 105 publications

Strong Polarized Enhanced Raman Scattering via Optical Tunneling through Random Parallel Nanostructures in Au Thin Films

Strong Polarized Enhanced Raman Scattering via Optical Tunneling through Random Parallel Nanostructures in Au Thin Films

Surface-Enhanced Raman Spectroscopy

Solution-Phase, Triangular Ag Nanotriangles Fabricated by Nanosphere Lithography

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