Surface plasmon electric

Futamata, M., Maruyama, Y. and Ishikawa, M. (2003) Local electric field and scattering cross section of Ag nanopartides under surface plasmon resonance by finite difference time domain method. J. Phys. Chem. B, 107, 7607-7617. 

FIGURE 10.3 Quantized oscillation of electrons at the surface of a metallic probe tip. This is so called surface plasmon. As the charge distribution is confined tightly at the sharp tip end, the subsequent electric field at the tip is strongly enhanced. 

Conduction electrons in a metal are nearly free to move within the metal in response to an applied electric field. A surface plasma wave, also called a surface plasmon, is an electromagnetic wave that propagates along the boundary between a metal and a dielectric (an electrical insulator). The electromagnetic field decreases exponentially into both layers but is concentrated in the dielectric layer. 

Figure 20-22a shows essentials of one common surface plasmon resonance measurement Monochromatic light whose electric field oscillates in the plane of the page is directed into a prism whose bottom face is coated with a thin layer (—50 nm) of gold. The bottom surface of the gold is coated with a chemical layer (—2-20 nm) that selectively binds an analyte of inter-... 

Electro-optic effects induced by doping liquid crystals with one-dimensional metal nanoparticles were not only investigated in standard electro-optic test cells, but also in costume-made cells consisting of a thin layer of liquid crystal either deposited onto a thin film of alumina with embedded GNRs [443], or using rubbed polyimide alignment layers modified with solution-cast GNR [444]. In both cases, surface plasmon resonance frequencies of the GNR integrated into these liquid crystal cells could be electrically controlled. 

Surface electromagnetic waves (SEW) on a metal-vacuum interface (often called surface plasmons) are discussed to demonstrate the essential features of SEW. SEW are surface waves in the sense that the electric and magnetic fields decay exponentially as one moves away from the surface, either into the metal or into the vacuum. Figure 1 shows the coordinate system we shall use. The metal-vacuum interface is the z = 0 plane, and the metal occupies the z < 0 half-space. The direction of propagation is the positive x-directi on. The metal has a... 

One simple explanation for these results was as follows The electric field at a metal vacuum interface can be >10 times larger than in free space when the conditions required for a surface plasma resonance are met (47). Since the Raman cross-section is proportional to the square of the field, surface plasmons could produce enhancements of >10. This enhancement is probably not large enough to explain the tunneling junction results by itself, but an enhancement in signal of a factor of 100 by the excitation of surface plasmons would increase the Raman intensity from near the limits of detectibility. 

A complementary approach to the standard reflection geometry described above uses the attenuated total reflection (ATR) geometry which couples surface plasmon waves to the incident electric field and enhances the SH production. Two configura-... 

As is specified in work [17], the system of conductivity electrons in a nanocrystal is similar to the resonator. Thereof electromagnetic field in a crystal can give rise to collective electronic excitations [17], which refer to as surface plasmons as they are caused by charges on a nanocrystal surface in dielectric [16]. At a>v dielectric permeability e (oj) according to the formula (5) is negative. It means that conductivity electrons in a nanocrystal oscillate out of phase with electric oscillations of an external field [16]. 

The piezo-electric effect of deformations of quartz under alternating current (at a frequency in the order of 10 MHz) is used by coating the crystal with a selectively binding substance, e. g. an antibody. When exposed to the antigen, an antibody-antigen complex will be formed on the surface and shift the resonance frequency of the crystal proportionally to the mass increment which is, in turn, proportional to the antigen concentration. A similar approach is used with surface acoustic wave detectors [142] or with the surface plasmon resonance technology (BIAcore, Pharmacia). 

Through the combination of SPR with a - poten-tiostat, SPR can be measured in-situ during an electrochemical experiment (electrochemical surface plasmon resonace, ESPR). Respective setups are nowadays commercially available. Voltammetric methods, coupled to SPR, are advantageously utilized for investigations of - conducting polymers, thin film formation under influence of electric fields or potential variation, as well as - electropolymerization, or for development of -> biosensors and - modified electrodes. Further in-situ techniques, successfully used with SPR, include electrochemical - impedance measurements and -+ electrochemical quartz crystal microbalance. 

Metal nanostructures (such as particles and apertures) can permit local resonances in the optical properties. These local resonances are referred to as localized surface plasmons (LSPs). The simplest version of the LSP resonance comes for a spherical nanoparticle, where the electromagnetic phase-retardation can be neglected in the quasi-static approximation, so that the electric field inside the particle is uniform and given by the usual electrostatic solution [3] ... 

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