Optics and Plasmonics: Fundamental Studies and Applications

Abstract

During the last decade, nanotechnology has become one of the major driving forces for basic and applied research [ 1-3 ]. The extraordinary physicochemical properties of metal particles as they approach the nanometer scale have increased the interest of physicists and chemists in nanoscience [ 4 ]. Matter at this size scale has been demonstrated to outperform in a wide variety of applications, such as catalysis [ 5 ] , environmental [ 6 ] , biological labeling and sensing [ 7, 8 ] , surface Raman scattering [ 9 ] , nonlinear absorption processes [ 10 ] , photonics [ 11 ] , and optoelectronics [ 12 ]. Nanoscience has additionally had a strong impact in biophotonics through radiative decay engineering (RDE) of organic dye molecules in the close vicinity of conducting metal surfaces or covalently attached to them [ 13-15 ]. Most of the applications explored so far are based on the well-known surface plasmon resonance (SPR) effect [ 16 ]. SPR in noble metal nanoparticles is manifested by well-defi ned absorption bands in the visible region as a result of the interaction of electromagnetic radiation with conduction band electrons [ 17 ]. These bands present a remarkable feature that should be underlined, i.e., their spectral position strongly depends on their size, shape, and composition [ 18 ]. This dependence has been applied, among other things, to the development of specifi c optical noses in biology and environmental applications [ 19, 20 ]. Furthermore, SPR can also produce a tremendous electric fi eld enhancement at the surface of metal nanoparticles [ 16 ]. Such an augmentation has been applied to second harmonic generation [ 21, 22 ] , SERS [ 9 ] , multiphoton-assisted excitation, and enhanced fl uorescence of chromophores [ 23-26 ]. Another effect worth to be highlighted is the modifi cation of the radiative decay rates of emitters close to metal surfaces [ 27-29 ]. As a result, RDE has resulted in the design of better fl uorophore complexes for bioimaging [ 30 ] , and has awakened the interest of the