6.2.2. Definition of Effective Properties 3064 6.3. Response Properties to Magnetic Fields 3066 6.3.1. Nuclear Shielding 3066 6.3.2. Indirect Spin−Spin Coupling 3067 6.3.3. EPR Parameters 3068 6.4. Properties of Chiral Systems 3069 6.4.1. Electronic Circular Dichroism (ECD) 3069 6.4.2. Optical Rotation (OR) 3069 6.4.3. VCD and VROA 3070 7. Continuum and Discrete Models 3071 7.1. Continuum Methods within MD and MC Simulations 3072

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Quantum mechanical continuum solvation models.

Surface plasmons are waves that propagate along the surface of a conductor. By altering the structure of a metal's surface, the properties of surface plasmons--in particular their interaction with light--can be tailored, which offers the potential for developing new types of photonic device. This could lead to miniaturized photonic circuits with length scales that are much smaller than those currently achieved. Surface plasmons are being explored for their potential in subwavelength optics, data storage, light generation, microscopy and bio-photonics.

/pdf/surface-plasmon-subwavelength-optics-5e55p12p4o.pdf

Surface plasmon subwavelength optics

Fundamentals of Plasmonics.- Electromagnetics of Metals.- Surface Plasmon Polaritons at Metal / Insulator Interfaces.- Excitation of Surface Plasmon Polaritons at Planar Interfaces.- Imaging Surface Plasmon Polariton Propagation.- Localized Surface Plasmons.- Electromagnetic Surface Modes at Low Frequencies.- Applications.- Plasmon Waveguides.- Transmission of Radiation Through Apertures and Films.- Enhancement of Emissive Processes and Nonlinearities.- Spectroscopy and Sensing.- Metamaterials and Imaging with Surface Plasmon Polaritons.- Concluding Remarks.

/pdf/plasmonics-fundamentals-and-applications-4syb9877sr.pdf

Plasmonics: Fundamentals and Applications

Recent developments have greatly improved the sensitivity of optical sensors based on metal nanoparticle arrays and single nanoparticles. We introduce the localized surface plasmon resonance (LSPR) sensor and describe how its exquisite sensitivity to size, shape and environment can be harnessed to detect molecular binding events and changes in molecular conformation. We then describe recent progress in three areas representing the most significant challenges: pushing sensitivity towards the single-molecule detection limit, combining LSPR with complementary molecular identification techniques such as surface-enhanced Raman spectroscopy, and practical development of sensors and instrumentation for routine use and high-throughput detection. This review highlights several exceptionally promising research directions and discusses how diverse applications of plasmonic nanoparticles can be integrated in the near future.

Biosensing with plasmonic nanosensors

Monodisperse samples of silver nanocubes were synthesized in large quantities by reducing silver nitrate with ethylene glycol in the presence of poly(vinyl pyrrolidone) (PVP). These cubes were single crystals and were characterized by a slightly truncated shape bounded by {100}, {110}, and {111} facets. The presence of PVP and its molar ratio (in terms of repeating unit) relative to silver nitrate both played important roles in determining the geometric shape and size of the product. The silver cubes could serve as sacrificial templates to generate single-crystalline nanoboxes of gold: hollow polyhedra bounded by six {100} and eight {111} facets. Controlling the size, shape, and structure of metal nanoparticles is technologically important because of the strong correlation between these parameters and optical, electrical, and catalytic properties.

http://science.sciencemag.org/content/sci/298/5601/2176.full.pdf

Shape-Controlled Synthesis of Gold and Silver Nanoparticles

Optical detection and spectroscopy of single molecules and single nanoparticles have been achieved at room temperature with the use of surface-enhanced Raman scattering. Individual silver colloidal nanoparticles were screened from a large heterogeneous population for special size-dependent properties and were then used to amplify the spectroscopic signatures of adsorbed molecules. For single rhodamine 6G molecules adsorbed on the selected nanoparticles, the intrinsic Raman enhancement factors were on the order of 10 14 to 10 15 , much larger than the ensemble-averaged values derived from conventional measurements. This enormous enhancement leads to vibrational Raman signals that are more intense and more stable than single-molecule fluorescence.

http://science.sciencemag.org/content/sci/275/5303/1102.full.pdf

Probing Single Molecules and Single Nanoparticles by Surface-Enhanced Raman Scattering

This paper reports two fundamental observations on the size-dependent optical properties of colloidal gold nanoparticles. First, faceted gold nanocrystals in the size range of 63 ± 3 nm have been found to be highly efficient for surface-enhanced Raman scattering (SERS). These nanocrystals are identified from a heterogeneous population for large optical enhancement at 647-nm laser excitation. Second, spatially isolated single gold particles emit Stokes-shifted Raman photons in an intermittent on-and-off fashion. In contrast to population-averaged studies, blinking surface-enhanced Raman scattering is a signature of single-particle (or even single-molecule) behavior. By directly measuring optical enhancement and time-resolved emission on single nanoparticles, this work opens new possibilities in studying the mechanisms of SERS, in developing metal tips for near-field optical microscopy, and in designing new nanostructured materials.

Efficient Raman enhancement and intermittent light emission observed in single gold nanocrystals

Steven R. Emory, William E. Haskins, and Shuming Nie*Department of Chemistry, Indiana UniVersityBloomington, Indiana 47405ReceiVed May 5, 1998Metal and semiconductor particles on the nanometer scale haveunique optical, electronic, and structural properties that are notavailable in either isolated molecules or bulk solids.

Direct Observation of Size-Dependent Optical Enhancement in Single Metal Nanoparticles

A rapid screening and enrichment method is reported for exploring the size and shape diversities (libraries) of nanometer-scale colloidal particles. With the use of surface-enhanced Raman scattering, a new class of metal nanoparticles has been identified from heterogeneous silver colloids. These particles are relatively large, faceted nanocrystals that are able to enhance the efficiencies of surface optical processes by as much as 14−15 orders of magnitude. The population of these novel nanoparticles is only about 0.1−1% in standard colloid preparations but can be enriched to about 10−15% by size-selective fractionation. This new class of nanoparticles could find potential uses in optoelectronic devices, ultrasensitive chemical sensors, and single-molecule detection.

Screening and Enrichment of Metal Nanoparticles with Novel Optical Properties

We report the development of a near-field Raman microscope for nanometer-scale vibrational spectroscopy at room temperature. With the use of surface-enhanced Raman scattering and tapered single-mode fiber probes, near-field Raman spectra have been obtained from single Ag colloidal nanoparticles with excitation intensities as low as 10 nW. Far-field confocal studies have also been carried out on spatially isolated, single Ag nanoparticles. A direct comparison of the near-field and confocal results shows that near-field optical excitation does not lead to significantly different selection rules in Raman spectroscopy. This work further demonstrates that single metallic nanoparticles can be attached to the tip of a near-field probe for potential application in surface-enhanced optical microscopy and nanofabrication.

Steven R. Emory

Papers

Probing Single Molecules and Single Nanoparticles by Surface-Enhanced Raman Scattering

Efficient Raman enhancement and intermittent light emission observed in single gold nanocrystals

Direct Observation of Size-Dependent Optical Enhancement in Single Metal Nanoparticles

Screening and Enrichment of Metal Nanoparticles with Novel Optical Properties

Near-Field Surface-Enhanced Raman Spectroscopy on Single Silver Nanoparticles