[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...

/pdf/the-optical-properties-of-metal-nanoparticles-the-influence-16vrpkvhkg.pdf

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.

Metamaterials fabricated for operation at terahertz frequencies are presented. Optical excitation enables control of the metamaterial resonance amplitude and frequency

Dynamic Metamaterials at Terahertz Frequencies

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

In this paper, we present a polarization insensitive air-spacer triple band absorber. With the fabricated absorber, the three near unity-absorption peaks can be fine controlled with different structure designs, which have a great advantage in variety applications. Also, with air instead of the traditional dielectric layer, the absorber will exhibit an extremely high quality factor (Q) compare with the one in dielectric layer. Moreover, with the air-spacer triple band absorber structure, the coupling between the metamaterials layer and the ground plane is very strong. As a result, the near-field interaction should be considered in the interference theory. With the coupling effect included, the correctional interference theory can well predict both the numerical and experiment results of the metamaterial perfect absorber. Our findings demonstrate that the capacitance increase and the inductance decrease are the causes of the difference between the interference theory and the simulation and experiment results especially for circles metamaterials structures with thin air-spacer in metamaterial perfect absorber.

Integrated Air Spaced Terahertz Metamaterial Absorber with High Quality Factor

We present a single-shot, high-temporal-resolution terahertz diagnostic capable of measuring free-space electromagnetic fields in time and space. Using the chirped probe electrooptic sampling technique, combined with a novel retrieval algorithm, it provides transform-limited temporal resolution.

Single-Shot, High Resolution Terahertz Field Diagnostic

In this paper, we present a three-dimensional (3D) terahertz metamaterial perfect absorber (MPA) with a high quality factor. The absorption response of the proposed structure is analyzed and optimized using coupled mode theory and numerical simulations. Subsequently, we fabricate the 3D MPA by employing the multi-layer electroplating process and characterize it using terahertz time domain spectroscopy. A quality factor of 20 is verified by the experimental results, which agrees well with the simulation. The high-Q MPA has potential applications in chemical and biological sensing.

Richard D. Averitt

Papers

Dynamic Metamaterials at Terahertz Frequencies

Optically induced lattice dynamics probed with ultrafast X-ray diffraction

Integrated Air Spaced Terahertz Metamaterial Absorber with High Quality Factor

Single-Shot, High Resolution Terahertz Field Diagnostic

A high-Q three-dimensional terahertz metamaterial perfect absorber