We have used numerical calculations based on Mie theory to analyze the near field distribution patterns for 4-150 nm spherical silver nanoparticles (nanospheres). We have shown that as the nanoparticle sizes increase, the region where "hot spots" are concentrated is shifted to the forward hemisphere. We have observed a nonmonotonic dependence of the maximum attainable local field enhancement factor on the size of the silver nanospheres. We have determined a correlation between the optimal nanosphere size for the maximum attainable local field enhancement factor and the optical absorption efficiency factor. We have established a nonmonotonic dependence of the optimal size of the nanoparticles and the maximum attainable local field enhancement factor on the refractive index of the surrounding medium.Introduction. Materials containing nanoparticles of noble metals are being actively studied today because of their important properties connected with formation of surface plasmon resonance (SPR) absorption bands in the visible region of the spectrum and substantial enhancement of local fields near the surface of the metallic nanoparticles ("hot spots"). Resonance enhancement of local characteristics of the optical field has a considerable effect on formation of linear and nonlinear optical properties of aggregated nanodispersed structures, and the extent to which these resonances appear can be effectively controlled by varying the topological and morphological parameters of the nanocomposites. Significant local field enhancement and its considerable nonuniformity are important factors leading to the appearance of "surface-enhanced" optical effects, such as surface-enhanced Raman scattering (SERS) and enhancement of the luminescence of molecules situated near the surface of metallic nanostructures.It has been established [1] that the local field enhancement effect is most significant near the SPR absorption bands of metallic nanoparticles. In turn, the spectral position of the SPR absorption bands is determined by the size of the nanoparticles, their shape and internal structure, and also the dielectric properties of the matrix in which they are embedded [2]. The near field distribution is also sensitive to all these parameters [3][4][5][6][7]. In this case, for example, in order to increase the intensity of Raman scattering by molecules situated near the surface of metallic nanoparticles, spectral overlap of the absorption bands of the selected molecules and the SPR absorption bands is of fundamental importance.In order to determine the optimal conditions for resonance local field enhancement by metallic nanospheres, in this work we have studied the topology of the near field distribution for silver nanoparticles of different sizes; we have established the characteristic localization scales for the local field enhancement regions; and we have also studied the dependence of the attainable values of the local field enhancement factor on the sizes of the silver nanoparticles and the properties of the dielectric environmen...

It is shown by numerical simulation that the enhancement of the field near metallic nanoparticles is most significant in the transparency region of the matrix material and falls off as the absorption coefficient rises. In an absorbing matrix medium this leads both to an increase in the fraction of energy absorbed by the matrix material and to a substantial transformation in its spectral distribution. This is illustrated for the case of copper phthalocyanine with silver nanoparticles. By choosing the size of the introduced plasmon nanoparticles it is possible to enhance the absorption in the visible for the materials used in solar cells and thereby increase their energy efficiency. Introduction.When plasmonic nanoparticles are present in a medium, surface plasmon absorption bands form and cause a substantial enhancement in the local electromagnetic field in the spectral region of the plasmon resonance [1-4]. The surface plasmon resonance responsible for the enhancement in the local field is primarily a characteristic of the metal from which the nanoparticles are made. However, certain features of this effect are determined by the sizes and shapes of the nanoparticles, and their organization (nanostructure), but also depend on the optical properties of the medium in which the nanoparticles are embedded. By changing the shape and size of the nanoparticles it is relatively easy to control the characteristics of the surface plasmon resonance.The possibility of local field enhancement in a medium turns out to be attractive for applications in photovoltaic solar cells, since an enhanced field raises the fraction of energy absorbed in the medium, which is proportional to the local field intensity. This is one of the concepts now under rapid development for raising the conversion efficiency for solar energy, both for cells with traditional semiconductors (silicon [5], gallium arsenide [6]) and thin film cells based on organic semiconductors [7].Up to now primary attention has been devoted to the features of the plasmon resonance and the local field enhancement in transparent media. However, absorption in a matrix material does affect the efficiency with which light is scattered [8][9][10][11]. Thus, one should expect changes in both the intensity and the character of the localization of "hot spots," and a transformation in the resulting absorption spectrum of the composite medium. In addition, with regard to absorbing media (and highly absorbing materials are used in photovoltaic cells), the presence of an additional spatial dependence of the wave field has a significant effect on the procedure for calculating and characterizing light scattering [12][13][14][15].Numerical Simulation Technique. The field near the surface of a spherical particle was determined by an approach based on Mie's theory. Our own computer program developed for the case in which the surrounding medium is absorbing was used. The near field distribution was described with the aid of the near zone scattering efficiency factor Q NF [2]. The factor Q NF ...

This paper proposes a novel approach for estimating the utilization efficiency of metal particles to increase light energy absorption by a medium with a nonzero imaginary part of a medium refractive index. This method is implemented for spherical Ag and Au nanoparticles embedded in muscle tissue. Numerical calculations for spheres in absorbing media show that the utilization efficiency of metal particles increases with the decreasing absorbability of the medium.