Cross-polarization nanoparticles

Un-ionized form of organic compounds are generally absorbed more easily, with the exception of nanoparticles. Presence of substituents that remain ionized at pH 2, such as —S03, make chemicals too polar to cross the intestinal membrane... 

Solutions for the scattering of evanescent waves by a sphere were studied initially by Chew et al. in 1979 (68). Evanescent wave is generated from a dielectric/air plane interface due to total internal reflection and is scattered by a dielectric sphere. Quinten et al, on the other hand, derived the total cross section for extinction and scattering of evanescent waves by a small metal particle (69). In these studies, a particle with smaller size is placed away from the plane interface, and therefore the multiple scattering between the sphere and the plane interface is ignored. Quinten s study further supports that the extinction cross section for the extinction of p-polarized evanescent waves by a metallic nanoparticle is larger than that for s-polarized evanescent waves and plane waves. This can be attributed to the... 

Fig. 10.11 (a) Optical responses of gold nanoparticle pairs as a function of polarization angle for particles separated by 0.8 and 2 radii, (b) NSOM images and cross sections for a gold nanoparticle pair at 532 nm for light polarized perpendicularly (a) and parallel (b) to the interparticle axis with cross-sectional view (Figure reproduced from Ref [134])... 

To examine the role of the LDOS modification near a metal nanobody and to look for a rationale for single molecule detection by means of SERS, Raman scattering cross-sections have been calculated for a hypothetical molecule with polarizability 10 placed in a close vicinity near a silver prolate spheroid with the length of 80 nm and diameter of 50 nm and near a silver spherical particle with the same volume. Polarization of incident light has been chosen so as the electric field vector is parallel to the axis connecting a molecule and the center of the silver particle. Maximal enhancement has been found to occur for molecule dipole moment oriented along electric field vector of Incident light. The position of maximal values of Raman cross-section is approximately by the position of maximal absolute value of nanoparticle s polarizability. For selected silver nanoparticles it corresponds to 83.5 nm and 347.8 nm for spheroid, and 354.9 nm for sphere. To account for local incident field enhancement factor the approach described by M. Stockman in [4] has been applied. To account for the local density of states enhancement factor, the approach used for calculation of a radiative decay rate of an excited atom near a metal body [9] was used. We... 

Hydrophilic materials can be encapsulated with the inverse minianulsions by using interfacial polymerization such as polyaddition and polycondensation, radical, or anionic polymerization. Crespy et al. reported that silver nitrate was encapsulated and subsequently reduced to give silver nanoparticles inside the nanocapsules. The miniemulsions were prepared by anulsilying a solution of amines or alcohols in a polar solvent with cyclohexane as the nonpolar continuous phase. The addition of suitable hydrophobic diisocyanate or diisothiocyanate monomers to the continuous phase allows the polycondensation or the cross-linking reactions to occur at the interface of the droplets. By using different monomers, polyurea, polythiourea, or polyurethane nanocapsules can be formed. The waU thickness of the capsules can be directly tuned by the quantity of the reactants. The nature of the monomers and the continuous phase are the critical factors for the formation of the hollow capsules, which is explained by the interfacial properties of the systan. The resulting polymer nanocapsules could be subsequently dispersed in water. 

Figure 8.21 Simulated near field distribution of a nanoparticle (the radius 40 nm) on M0O3 belt. Theyz plane is the cross-section through the particle center. The particle is separated 10 nm from the surface of the waveguide. Inset the belt is excited by a 632.8 mn laser focused to the edge. The incident polarization is along x-axis. The thickness of the belt is d = 200 nm. The particle is 5 m from the excitation. Reprinted from Ref. [74] with kind permission from Springer Science+Business Media.

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