[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

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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The Optical Properties of Metal Nanoparticles: The Influence of Size, Shape, and Dielectric Environment

The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102

Chemistry and properties of nanocrystals of different shapes.

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

We present the design for an absorbing metamaterial (MM) with near unity absorbance A(omega). Our structure consists of two MM resonators that couple separately to electric and magnetic fields so as to absorb all incident radiation within a single unit cell layer. We fabricate, characterize, and analyze a MM absorber with a slightly lower predicted A(omega) of 96%. Unlike conventional absorbers, our MM consists solely of metallic elements. The substrate can therefore be optimized for other parameters of interest. We experimentally demonstrate a peak A(omega) greater than 88% at 11.5 GHz.

Perfect metamaterial absorber.

Metamaterial and plasmonic composites have led to the realization that new possibilities abound for creating materials
displaying functional electromagnetic properties not realized by nature. Recently, we have extended these ideas by
combining metamaterial elements - specifically, split ring resonators - with MEMS technology. This has enabled the
creation of non-planar flexible composites and micromechanically active structures where the orientation of the
electromagnetically resonant elements can be precisely controlled with respect to the incident field. Such adaptive
structures are the starting point for the development of a host of new functional electromagnetic devices which take
advantage of designed and tunable anisotropy.

Flexible and reconfigurable terahertz metamaterials

We have studied the picosecond-dynamics of optically pumped hexagonal LuMnO/sub 3/ using ultrafast X-ray diffraction. Experimental data are compared with a simulation based on dynamical diffraction theory modified to account for the hexagonal structure of LuMnO/sub 3/.

Optically Induced Lattice Dynamics Probed with Ultrafast X-ray Diffraction

Evidence for Linelike Vortex Liquid Phase in Tl 2 Ba 2 CaCu 2 O 8 Probed Using Terahertz Time-Domain Spectroscopy

Conductivity Dynamics in the Correlated Metallic State of V$_{2}$O$_{3}$

In this paper, we present novel optically tunable metamaterials (MMs) on flexible polymer sheet operating at terahertz (THz) frequencies. The flexible MMs, consisting of electric split-ring resonators (ESRRs) on GaAs patches, were fabricated on a polyimide thin layer using the developed transfer technique. Our experimental results revealed that with increasing fluence of the incident excitation beam, the transmission amplitude increases from 24% to 40% at 0.98 THz yet decreases from 78% to 25% at 1.25 THz. Our flexible tunable device enables potential applications for terahertz sensing, modulation and perfect absorption not only on rigid flat surfaces but also on curved surfaces.

Richard D. Averitt

Papers

Flexible and reconfigurable terahertz metamaterials

Optically Induced Lattice Dynamics Probed with Ultrafast X-ray Diffraction

Evidence for Linelike Vortex Liquid Phase in Tl 2 Ba 2 CaCu 2 O 8 Probed Using Terahertz Time-Domain Spectroscopy

Conductivity Dynamics in the Correlated Metallic State of V$_{2}$O$_{3}$

Flexible and tunable metamaterials at terahertz frequencies